Anesthetic Management of the Pregnant Cardiac Patient
Shobana Chandrasekhar
Daniel A. Tolpin
Dennis T. Mangano
Introduction
The pregnant parturient with cardiac disease continues to challenge the anesthesiologist’s skills. Pregnancy, labor, and delivery impose unique stresses on the circulation. In fact, the induction and delivery of anesthesia may further destabilize these patients if not approached cautiously and comprehensively. To avoid cardiac decompensation, the anesthesiologist must be thoroughly aware of the normal physiology of labor, delivery, and the puerperium (1); the nature and progression of heart disease during pregnancy (2); the cardiovascular effects of various anesthetic regimens (3); and the therapies available to manage acute complications (4). In the first section of this chapter, we review the incidence, risks, morbidity, and mortality of cardiovascular diseases that are known to occur in these patients. We review expected changes to the cardiovascular system that occur during all phases of pregnancy, and make recommendations for the choice of anesthetic and the mode of delivery. The second, third, and fourth sections review significant cardiovascular diseases that anesthesiologists encounter in parturients. The final section addresses the less common, but important issue of surgical treatment of cardiac disease during pregnancy and cardiac transplantation, with particular attention to the effects on the fetus.
Background
Epidemiology
The incidence of heart disease among pregnant patients varies by age, country, and socioeconomic status from less than 0.1% to 3.9% and has decreased over the past 4 decades (1,2,3,4,5,6,7,8,9,10,11). In particular, among patients in developing countries, the incidence appears highest with rheumatic heart disease (RHD) being the most prevalent type of cardiac disease in parturients (12,13,14). Among developed countries, despite advances in the prophylaxis for, and treatment of, cardiac disease, challenges continue given the increasing age of parturients and the attendant risks regarding disease progression (15,16,17). Notably, several diseases appear most challenging, including right-sided lesions, right-to-left congenital shunts, aortic stenosis, and heart failure (12,13,17,18,19,20,21).
Cardiovascular Changes Associated with Pregnancy and Delivery
Cardiovascular changes, associated with pregnancy and delivery, induce progressive stress on both mother and fetus. During labor, stress, pain, and compensatory changes trigger increases in stroke volume and cardiac output by 50% over prelabor values. Additionally, other stresses can impose acute increases in central blood volume and lead to cardiac decompensation, such as acute uterine contraction (increasing central blood volume and cardiac output by 10% to 25%), and, following delivery, relief of vena cava obstruction (increasing central blood volume and cardiac output by 50% to 100%). These acute changes are well tolerated by the normal heart; however, such preload stress may be intolerable to a diseased heart that has become increasingly compromised throughout pregnancy and labor. When combined with postdelivery cardiovascular changes and those induced by hemorrhage or administration of oxytocic drugs, rapid decompensation may occur (Figs. 30-1 and 30-2).
Overview of Anesthetic Considerations
Anesthetic management involves an understanding of the type, severity, and progression of the disease in the context of the normal cardiovascular adaptations to pregnancy. Preanesthetic assessment in each trimester of pregnancy is of paramount importance as the presence or worsening of symptoms correlate directly with morbidity and mortality. Physical examination and consultation with the primary physician and the cardiologist are necessary to define the severity of the disease.
There are very few controlled studies addressing the effects of anesthetics and therapeutics on pregnant patients with cardiac disease. However, the physiologic changes occurring during pregnancy, the pathophysiology of cardiac disease processes, and the effects of anesthetics on pregnant patients without cardiac disease are well documented. Anesthetic management of pregnant patients with cardiac disease involves a firm understanding of the above complex issues.
Cardiovascular maternal morbidity and mortality during pregnancy correlate strongly with maternal functional status (22,23,24). Women with NYHA class I and II (no or minor symptoms) are likely to tolerate pregnancy without major deterioration, whereas risk progressively increases among those with NYHA III and IV (25). See Table 30-1.
Choice of Technique
Analgesic techniques and anesthetic management for vaginal delivery or cesarean delivery of pregnant cardiac patients are largely determined by the nature of the presenting illness. The primary concern of the anesthesiologist is to avoid and/or treat specific pathophysiologic changes that can exacerbate the disease process. Of note are auto transfusion during uterine contractions, effects of oxytocic agents, and degree of hemorrhage. The risks of each anesthetic technique must be balanced against the possible benefits to both the mother and the fetus, in the context of the presenting cardiac disease. In general, no one anesthetic approach is exclusively indicated or contraindicated.
 Figure 30-1 Cardiac output changes during labor and delivery. |
Monitoring
In addition to routine monitoring (continuous electrocardiography, pulse oximetry, and noninvasive blood pressure assessment), the use of more invasive monitoring (intra-arterial, central venous, pulmonary artery, echocardiography [ECG]) during labor and delivery depends on the severity and progression of the cardiovascular disease prior to, and during, pregnancy (26,27,28,29). Asymptomatic patients without any evidence of disease progression most likely will experience an uneventful course and will not require invasive monitoring. However, exceptions do exist and must be considered even among asymptomatic patients who present with primary pulmonary hypertension, right-to-left shunt, dissecting aortic aneurysm, severe aortic stenosis, or coarctation of the aorta. Such patients, as well as those manifesting signs and/or symptoms of cardiovascular compromise, should undergo thorough hemodynamic profiling including measurement of cardiac output, vascular resistance, and central pressure, and function (surface ECG). Based on these measurements, a therapeutic plan should be designed for handling each of the acute complications that may occur with the specific disease.
 Figure 30-2 Normal heart. |
Perioperative use of pulmonary artery catheters (PACs) remains controversial (30); however, under certain conditions where central pressure and peripheral resistance measurements are critical, we continue to recommend its use. For example, we believe that PAC placement is indicated in patients with decompensated cardiac disease, pulmonary hypertension, severe mitral/aortic stenosis, patients with NYHA IV heart disease, ARDS, and preeclampsia with refractory oliguria or pulmonary edema (23,31,32).
Both transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) can provide critical information regarding risk assessment and disease progression (33). Among our population, use of these techniques is highly recommended, certainly for those undergoing general anesthesia (TEE) and those undergoing regional anesthesia (TTE).
A review by Armstrong et al. highlights newer technologies that are available and maybe integrated in routine practice in the future management of severely ill,
pregnant cardiac patients (34). Apart from TTE that has been validated and proven useful for pregnancy, there are other noninvasive or minimally invasive monitors used in current obstetric practice. TTE is precisely accurate and informative, but is highly specialized and needs training and expertise on a routine basis, which is hard to acquire by the obstetric anesthesiologist in everyday practice. The normal structural and functional changes that occur during pregnancy have to be understood when interpreting these studies.
pregnant cardiac patients (34). Apart from TTE that has been validated and proven useful for pregnancy, there are other noninvasive or minimally invasive monitors used in current obstetric practice. TTE is precisely accurate and informative, but is highly specialized and needs training and expertise on a routine basis, which is hard to acquire by the obstetric anesthesiologist in everyday practice. The normal structural and functional changes that occur during pregnancy have to be understood when interpreting these studies.
Table 30-1 NYHA Classification System for Heart Failure | ||||||||||||
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TEE provides clearer images due to signal attenuation by the chest wall. It also provides better views of the atria, septum, and detection of thrombi. However, it will not be tolerated in an awake obstetric patient. Hence, this device is most useful in parturients undergoing delivery under general anesthesia. Recent National Institute for Health and Clinical Excellence (NICE) guidelines have recommended the use of esophageal Doppler in major or high risk surgery to reduce the need for central venous catheterization and postsurgical morbidity (35).
The suprasternal Doppler ultrasound is a completely noninvasive method for measuring hemodynamic variables. They could be ideal for use in pregnant patients; however, there are interobserver variabilities and naturally there is a learning curve. More research is needed into this technology.
There are also minimally invasive techniques based on analysis of the arterial waveform (LiDCO, PiCCO, and FloTrac-Vigileo). These are the pulse contour devices that seem promising based on their ease of use and calibration, measurement of fluid responsiveness, and their precision when compared to PAC derived measures of cardiac output (34,35). The latter group measures the electrical resistance changes induced by vascular flow (bioimpedance and bioreactance techniques).
Potential Problems at Delivery
Hemorrhage is not well tolerated in patients with coexisting cardiac disease since they may be unable to compensate given limitations in heart rate and stroke volume responses. Bleeding may be increased due to concurrent anticoagulation.
Pulmonary edema is more likely to occur in the peripartum period in patients with depressed cardiac function due to fluid shifts and as a consequence of additional intravenous (IV) fluids to replace intravascular volume losses. Careful fluid balance is essential; urine output and blood loss should be closely monitored and care should be taken in administering fluids. This may be aided by running drug infusions in smaller volumes of increased concentration to reduce excess IV fluid administration.
Dysrhythmias and tachycardia are poorly tolerated in most patients with significant cardiac disease. Pharmacologic agents causing tachycardia should be avoided or limited. Oxytocin after delivery should be used in slower and more dilute preparations.
Embolism clearly is a risk among women with cardiac disease, particularly venous thromboembolism. Air embolism can occur among women with right-to-left shunt, requiring proper de-airing of all intravenous access lines.
Acute pulmonary hypertension at delivery can cause right ventricular failure and cardiac ischemia in susceptible patients. The risk of death is high in those with severe pulmonary hypertension, and severe morbidity can occur even in those patients with relatively mild pulmonary hypertension.
Postoperative Care
Since hemodynamic aberrations associated with labor and delivery continue after delivery, patients with symptomatic heart disease who have had a complicated peripartum course should be managed in a multidisciplinary intensive care unit.
Congenital Heart Disease
The overall incidence of congenital heart disease (CHD) has remained stable over the last 5 decades with most studies reporting incidences of 4/1,000 to 12/1,000 live births (36,37,38). However, the prevalence of CHD in the adult population has increased in this same time period due to improvement in therapies aimed at increasing the survival of infants born with CHD (36,37,38,39). Cardiac disease in the parturient is increasingly attributable to CHD as opposed to acquired disease. Management of the parturient with CHD requires an understanding of underlying physiology associated with different CHD defects as well as the cardiovascular changes of pregnancy. In addition, cardiac function, coexisting cardiac disease, and type of surgical repair all affect the care of the parturient with CHD.
We will address CHD separately among three groups based on lesion physiology: left-to-right shunts (atrial septal defect [ASD], ventricular septal defect [VSD], patent ductus arteriosus [PDA]), right-to-left shunts (tetralogy of Fallot [TOF], Eisenmenger’s syndrome), and congenital valvular and vascular lesions (coarctation of the aorta, aortic stenosis [AS], pulmonary stenosis [PS]).
Left-To-right Shunt
Atrial Septal Defect
ASDs are the most common CHD found in adults occurring in up to 21% of adults with CHD (37,40) (Table 30-2). Symptomatic ASDs are typically corrected early in life; patients with small- or moderate-sized ASDs usually do not develop symptoms until the fourth or fifth decade of life. Symptomatic patients may display dysrhythmias, congestive heart failure, and pulmonary hypertension. Most women with an ASD (corrected or uncorrected) will tolerate pregnancy well with little increased risk of maternal morbidity or mortality. Women with uncorrected ASDs may be at increased risk for
delivering small-for-gestational-age infants (41). The most common maternal complications associated with pregnancy in patients with an ASD are cardiac dysrhythmias, endocarditis, heart failure, and cerebrovascular events (19,41). Fetal and perinatal mortality are increased and occur in up to 2.4% of pregnancies (19,41,42).
delivering small-for-gestational-age infants (41). The most common maternal complications associated with pregnancy in patients with an ASD are cardiac dysrhythmias, endocarditis, heart failure, and cerebrovascular events (19,41). Fetal and perinatal mortality are increased and occur in up to 2.4% of pregnancies (19,41,42).
Table 30-2 Atrial Septal Defect | ||||||
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 Figure 30-3 Modified mid-esophageal aortic valve short-axis view demonstrating a large ASD (left-to-right blood flow). LA, Left atrium; RA, Right atrium; ASD, Atrial septal defect. |
Clinical Manifestations
Signs and Symptoms: Physical examination findings include fixed expiratory splitting of the second heart sound and a systolic ejection murmur at the left upper sternal border, whose intensity varies with the degree of left-to-right shunting (43).
Test Indicators: Chest x-ray may reveal cardiomegaly, pulmonary artery prominence, and increased pulmonary vascular markings. Electrocardiography usually demonstrates signs of increased right-sided pressures (right ventricular hypertrophy, right atrial enlargement, right axis deviation) (44). ECG can be utilized to visualize and classify the ASD (primum, secundum, and sinus venosus). RV function and size, LV function and size, PA pressure and shunt fraction can all be assessed with ECG (Figs. 30-3 and 30-4). Cardiac catheterization usually reveals normal RA, RV, and PA pressures, even in the presence of cardiac chamber dilation.
Pathophysiology: Left-to-right shunting increases the amount of volume delivered to the right ventricle. The resultant rise in RV preload increases RV volume work and pulmonary blood flow. Compensatory changes in the capacitance of the pulmonary vascular system maintain normal PA pressures until the fourth or fifth decade of life. Chronic volume overload of the right and left atria leads to biatrial enlargement, and the onset of supraventricular dysrhythmias, particularly atrial fibrillation. Eventually, the pulmonary vasculature can no longer manage the increased pulmonary blood flow leading to increased pulmonary vascular resistance (PVR) and pulmonary hypertension. Right ventricular failure secondary to the chronic increased volume workload may occur, particularly when pressure work increases or in the presence of pulmonary hypertension.
Cardiovascular changes of pregnancy augment the physiologic derangements of left-to-right shunts. Normal increases in cardiac output and blood volume during pregnancy may increase the amount of left-to-right shunting, leading to increased work of the ventricles and increased pulmonary blood flow. Depending on the severity of the underlying disease, may precipitate left or right ventricular failure and pulmonary hypertension. Supraventricular dysrhythmias are of particular concern because incomplete left atrial emptying leads to volume and pressure increases in the left atrium worsening any left-to-right shunt.
 Figure 30-4 Mid-esophageal four chamber view demonstrating a large ASD (secundum). Also note enlarged right ventricle secondary to chronic volume overload. RA, Right atrium; RV, Right ventricle; LA, Left atrium; LV, Left ventricle. |
Anesthetic Considerations: Asymptomatic patients who have no evidence of pulmonary hypertension or RV compromise can go through labor without special care. Patients with symptoms of RV compromise or pulmonary hypertension should have arterial, central venous, or pulmonary arterial catheter monitoring depending on the severity of their symptoms. The following key points should be noted.
Supraventricular dysrhythmias are poorly tolerated and may increase left-to-right shunt. Generally, antiarrhythmic medications should be continued throughout the pregnancy and the peripartum period. New onset dysrhythmias associated with hypotension or RV failure should be treated immediately with direct current cardioversion or use of pharmacologic rate control (β-blockers, calcium channel blockers, amiodarone, etc.).
Increases in systemic vascular resistance (SVR) may worsen a left-to-right shunt. Increases in vascular resistance increase the impedance to left ventricular emptying, increasing pressure in the left-sided heart chambers and worsening a left-to-right shunt.
Decreases in PVR may worsen a left-to-right shunt. Decreases in PVR may decrease the pressures in the right side of the heart thus increasing the pressure difference between the left and right sides of the heart. This worsens a left-to-right shunt and may lead to hypotension.
Increases in PVR exacerbate pre-existing pulmonary hypertension, which may lead to right ventricular failure.
Anesthesia for Vaginal Delivery and Cesarean Delivery
Lumbar epidural anesthesia for either vaginal delivery or cesarean delivery avoids the harmful increases in SVR that may worsen left-to-right shunting across an ASD. General anesthesia that keeps the above goals in mind can also be safely used.
Ventricular Septal Defect
VSDs are the most common congenital heart defect present at birth. However, about two-thirds resolve (close) after birth with three-quarters resolving spontaneously by age 70 (36) (Table 30-3). Among adults with CHD, about 20% present with VSDs (37,40,45). Small defects typically require no medical or surgical intervention and most of these will eventually close on their own. Larger VSDs require medical management for heart failure symptoms and are usually referred for surgical correction (46). Symptomatic patients may present in heart failure, with dysrhythmias or in severe cases with Eisenmenger’s syndrome.
Women with small isolated VSDs usually tolerate pregnancy and delivery without any problems. Women with repaired VSDs can also undergo pregnancy and delivery safely though they may be at higher risk for preterm delivery and for delivering small-for-gestational age infants (47). The most serious complications occur in pregnancies (CHF, dysrhythmia, major cardiovascular events) complicated by reversal of their left-to-right shunt (Eisenmenger’s syndrome discussed in right-to-left section), and in those patients with other congenital heart defects in addition to their VSD (19,42,48). Neonatal mortality is slightly increased at 1.4% in women with a VSD (19).
Table 30-3 Ventricular Septal Defect | ||||||
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Clinical Manifestations
Signs and Symptoms: Physical examination features of VSDs depend on the size and location of the lesion. Auscultation typically reveals a pansystolic murmur. Smaller defects may have the loudest murmur associated with them along with a thrill. The murmur may be loudest at different locations along the precordium depending if the VSD is in the muscular and membranous septum. Larger lesions that cause elevations in the pulmonary artery pressure may cause splitting of the second heart sound. However, as ventricular pressure equalizes, the flow murmur diminishes (46).
Test Indicators: Most asymptomatic VSD patients will present with a normal electrocardiogram and chest x-ray. The ECG and chest x-ray will reflect the changes that occur in the heart as the shunt increases. Left ventricular hypertrophy (LVH) and left atrial enlargement may be present in predominantly left-to-right shunts with normal PAP; a slight increase in pulmonary vasculature may be present on chest x-ray. As the shunt increases more, and the PAP rises, the ECG will show signs of right axis deviation and right ventricular hypertrophy. The chest x-ray shows increased vascularity and signs of right heart enlargement (46). ECG will identify lesion anatomy, associated lesions, shunt direction, and the shunt ratio (Qp/Qs) (Fig. 30-5).
Pathophysiology: Similar to ASDs, most VSDs result in small left-to-right shunts that are usually well tolerated with PVR decreasing to accommodate the increase in pulmonary blood flow and maintain normal PAP. With larger VSDs, left-to-right shunting of blood increases, eventually limiting PVR compensation, and resulting in increases in PAP. Left ventricular volume work increases, leading to dysfunction, elevated PCWPs, and progressive worsening of pulmonary hypertension. Consequent is right ventricular
failure, equalization of right and left ventricular pressures, bidirectional shunting, cyanosis, and clubbing.
Figure 30-5 Mid-esophageal long-axis view demonstrating a VSD with left-to-right ventricular flow. LA, Left atrium; LV, Left ventricle; RV, Right ventricle; AO, Ascending aorta; VSD, Ventricular septal defect.
Increases in cardiac output, intravascular volume, and heart rate which occur with pregnancy may worsen the existing left-to-right shunt and lead to right or left ventricular heart failure. Increases in stress as seen in labor or from surgical stimulation may produce intolerable increases in SVR and PVR resulting in left or right ventricular failure.
Anesthetic Considerations: Pregnant woman with small, asymptomatic VSDs may undergo pregnancy and delivery without the use of extra monitors or special care. Women with symptomatic, large VSDs, or signs of heart failure should have invasive monitoring during labor and delivery proportionate to the degree of their symptoms. Invasive arterial monitoring, central venous access, PAC use, and ECG may be used in the care of these patients. Important anesthetic considerations are summarized below.
Increases in SVR may not be tolerated. Increases in SVR may worsen a left-to-right shunt and lead to right or left ventricular dysfunction. Afterload-reducing agents such as nicardipine or nitroglycerine may be useful. If there is evidence of ventricular dysfunction, vasodilators such as dobutamine or phosphodiesterase inhibitors may be useful.
Marked increases in heart rate are poorly tolerated. In addition to increases in SVR worsening left-to-right shunting, increases in heart rate may also worsen left-to-right shunting. β-blockers or calcium channel blockers should be continued, and/or started if indicated. Adequate pain control for the different stages of labor and delivery is needed to prevent tachycardia and increases in SVR.
With pulmonary hypertension and right ventricular compromise, marked decreases in SVR may not be well tolerated. Patient with pulmonary hypertension and right ventricular dysfunction are susceptible to bidirectional shunting or reversal of a left-to-right shunt with marked decreases in SVR. Right-to-left shunting and systemic hypoxia may ensue. Vasoconstrictors such as phenylephrine are useful to help reverse large decreases in SVR as seen with the onset of a lumbar epidural sympathetic blockade. In addition, patients with increased right-sided pressures are at risk for ischemia if the systemic blood pressure is low enough to critically reduce coronary perfusion pressure to the right side of the heart.
Factors that increase PVR should be avoided in patients with pulmonary hypertension and evidence of right ventricular compromise. In patients who already have evidence of pulmonary hypertension and RV compromise, any further increases (hypercarbia, hypoxia, sympathetic stimulation) can result in right ventricular failure.
Anesthesia for Vaginal Delivery and Cesarean Delivery
Continuous lumbar epidural anesthesia provides excellent anesthesia for both labor and delivery, either via vaginal delivery or cesarean delivery. In addition, the afterload reduction associated with continuous lumbar epidural anesthesia reduces the impedance to left ventricular emptying, reducing intraventricular pressure and thus decreasing the amount of blood shunted from left to right. Spinal anesthesia should be used with caution, as large decreases in SVR may not be tolerated. Vasopressors should be titrated as needed to offset the rapid sympathectomy that accompanies spinal anesthesia with local anesthetics. General anesthesia may be used safely if the above goals are kept in mind. Inhaled anesthetics combined with intravenous opioids provide a balance of blunting the sympathetic response to surgery and minimizing any increases in SVR with minimal cardiac depression. Additional vasodilators may be necessary.
Table 30-4 Patent Ductus Arteriosus | ||||||
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Potential Complications: Cyanosis or hypoxia in the presence of an increased cardiac output likely represents an imbalance between the pulmonary and SVRs with resultant right-to-left shunting. Treatment includes switching to 100% oxygen, and increasing the SVR by and the addition of a vasopressor such as phenylephrine. If the cardiac output is depressed, 100% oxygen should be administered along with a reduction in anesthesia and the addition of inotropes or vasodilators (depending on SVR).
Patent Ductus Arteriosus
The reported incidence of PDA ranges from 1/500 to1/2,000 (37,49,50) (Table 30-4). Up to 23% of PDAs may resolve spontaneously (51). Similar to other causes of left-to-right shunt, the timing and severity of the symptoms is dependent on the degree of shunt. Small PDAs may not develop symptoms until the fourth or fifth decade of life. Larger PDAs develop symptoms earlier in life including reactive airway disease, dyspnea on exertion, dysrhythmias, pulmonary hypertension and/or heart failure (50). Infrequent complications include aneurysm of the ductus, recurrent laryngeal nerve injury, and infective endarteritis (50). Little evidence is available as to the outcomes of pregnancy with PDAs; however, outcomes appear to be dependent on the severity of symptoms. Complications associated with pregnancy include dysrhythmias, heart failure, and pulmonary artery rupture (along with small-for-gestational-age fetuses) (42,52).
Clinical Manifestations
Signs and Symptoms: Small, asymptomatic PDAs may have no physical examination findings. Classically, the murmur associated with PDAs is a continuous murmur heard best at the left sternal border ending in late or mid-diastole. The murmur may radiate around to the back. Large PDAs may cause widening of the pulse pressure and signs of heart failure (50).
Test Indicators: Patients with a small PDA may have a normal ECG and chest x-ray. Larger PDAs may show evidence of LV or RV hypertrophy or dysrhythmias (commonly atrial fibrillation). Chest x-ray in patients with larger PDAs may display signs of pulmonary vascular congestion or cardiomegaly (50).
Pathophysiology: Shunting of blood across a PDA results in a left-to-right shunt, increasing blood flow through pulmonary vasculature at the expense of flow through the systemic circulation. The amount of blood shunted from left-to-right depends on the resistance to flow across the PDA. The resistance is determined by the size and length of the ductus as well as the pressure difference between the aortic and pulmonary blood pressure. Small PDAs (<1 cm) impart a large resistance to flow and result in minimal shunting of blood that is well tolerated. Moderately sized PDAs (1 to 2 cm) and large PDAs (>2 cm) result in significantly more blood flow through the pulmonary vasculature.
When the pulmonary vasculature can no longer compensate, pulmonary hypertension ensues. Left ventricular work is increased to compensate for the left-to-right shunt, eventually left ventricular failure develops worsening any existing pulmonary hypertension and leading to biventricular failure. Large shunts can eventually result in reversal leading to a right-to-left shunt (Eisenmenger’s syndrome).
With pregnancy, the increased intravascular volume can increase shunting across the PDA worsening pulmonary hypertension and left ventricular work. In addition, the increased heart rate and stroke volume will increase myocardial oxygen demand and may compromise left ventricular function during stressful periods, such as uterine contractions. The decrease in SVR seen throughout pregnancy and the postpartum period may lead to shunt reversal and cyanosis in patients with large PDAs.
Anesthetic Considerations: Asymptomatic patients with small shunts and no evidence of ventricular dysfunction may undergo labor and delivery without special considerations. Women with symptomatic, large PDAs, pulmonary hypertension, or signs of ventricular dysfunction should have invasive monitoring during labor and delivery proportionate to the degree of their symptoms. Invasive arterial monitoring, central venous access, PAC, and ECG may be used in the care of these patients. Important anesthetic considerations are summarized below.
Increases in SVR may not be tolerated. Increases in SVR may worsen left-to-right shunting and pulmonary hypertension.
Marked increases in blood volume may be poorly tolerated. Increases in blood volume may lead to ventricular failure by increasing ventricular work and oxygen demand.
Marked decreases in SVR or increases in pulmonary resistance may lead to reverse shunting in patients with pre-existing pulmonary hypertension and right ventricular compromise. See section on Eisenmenger’s syndrome.
Patients with left ventricular failure may not tolerate additional myocardial depression.
Anesthesia for Vaginal Delivery and Cesarean Delivery
The decrease in afterload associated with continuous lumbar epidural anesthesia makes it an excellent choice for pain control during labor and delivery. Lumbar epidural anesthesia is also excellent for cesarean delivery as it will prevent increases in SVR associated with painful stimulation. Spinal anesthesia with narcotics alone or combined with local anesthetics may be used. However, care should be taken not to severely decrease SVR as this may cause a reversal of flow through a PDA. Spinal anesthesia should be used with particular caution if at all, in patients with large PDAs. General anesthesia can safely be administered to patients with a PDA undergoing cesarean delivery; supplementation with additional vasodilators may be needed to prevent increases in SVR.
Monitoring Concerns: Monitoring extremities with pulse oximetry has been shown to be useful (53). The right hand blood flow is predominantly preductal; blood flow to the feet is postductal. When the oxygen saturation of the right hand is constant, the oxygen saturation of the foot will change inversely with the amount of right-to-left shunting through the PDA.
Right-To-left Shunt
Tetrology of Fallot
TOF is the most common of the cyanotic congenital heart defects and comprises 5% to 10% of all congenital heart defects, with TOF occurring in 3/100,000 to 4.7/100,000 live births (49,54,55,56) (Table 30-5). TOF is characterized by right ventricular outflow obstruction, VSD, right ventricular hypertrophy, and an overriding aorta (an aortic valve with biventricular connection, which is situated above the VSD and connected to both the right and the left ventricle). The degree to which the aorta is attached to the right ventricle is referred to as its degree of “override.” Medical and surgical advances in the last 5 decades have led to the long-term survival of females born with this CHD allowing these women to lead normal lives including going through pregnancy and childbirth. Multiple centers have a 30-year long-term survival after TOF repair of up to 86% (57,58,59).
Table 30-5 Tetralogy of Fallot | ||||||
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Pregnancy in patients with uncorrected TOF is usually counseled against and is associated with worsened maternal and fetal outcomes (55,60). Risk factors for increased morbidity and mortality include syncope, polycythemia, low arterial oxygen saturation (< 80%), and right ventricular hypertension (1,4,5,28,29,61,62,63,64). As discussed above, most women reaching childbearing age will have had surgical corrective or palliative procedures. Women with corrected TOF are not at increased risk for mortality during pregnancy; however, they are at higher risk for maternal and neonatal morbidity. Women with corrected TOF are at higher risk for ventricular/supraventricular dysrhythmias (up to 7%) and heart failure (2.4%) (19,42,55,65,66,67). Risk factors for cardiovascular complications include severe pulmonary regurgitation, pulmonary hypertension, and right ventricular dilation. In addition, women with uncorrected or corrected TOF are at increased risk for delivering small-for-gestational-age infants (up to 30% and 35% respectively). Fetal mortality is not increased in women with corrected TOF (19,55,60,65).
Clinical Manifestations
Signs and Symptoms: TOF results in right-to-left shunting of blood leading to cyanosis, clubbing, and pulmonary hypertension. S2 in TOF patients is exaggerated and a systolic ejection murmur is present at the left sternal border near the second or third intercostal space. Severely obstructed patients have little flow through the pulmonary outflow tract and will subsequently have a softer murmur. ECG typically demonstrates right axis deviation and right ventricular hypertrophy. Chest x-ray displays cardiomegaly, classically in a “boot” shape. ECG can be used to differentiate the different anatomical varieties of TOF, assess the degree of pulmonic outflow obstruction, and identify any other coexisting lesions (54).
Pathophysiology: Right ventricular outflow obstruction increases intraventricular pressure in the right ventricle promoting right-to-left shunting through the VSD. The degree of shunting depends on the following: The size of the VSD, the obstruction to outflow from the right ventricle, and the ability of the right ventricle to overcome that obstruction. Right ventricular outflow obstruction often has two components: A fixed obstruction from pulmonic stenosis and a dynamic component from infundibular hypertrophy. Obstruction as a result of infundibular hypertrophy is
worsened by hypovolemia, catecholamines, or other hyperdynamic states (see section on asymmetric septal hypertrophy) (54). If the dynamic component is absent, maintenance of right ventricular contractility is important for pulmonary blood flow and peripheral oxygenation. Regardless of the type of right ventricular outflow obstruction, decreases in SVR may exacerbate right-to-left shunting and produce cyanosis.
Pregnancy-induced Changes: The physiologic changes associated with labor and delivery can compromise parturients with TOF. The stress and pain associated with labor and delivery can increase PVR, thereby worsening right-to-left shunting. SVR is reduced throughout pregnancy and may lead to worsening of a right-to-left shunt. Dynamic obstruction may particularly worsen during delivery when contractility is the highest.
Anesthetic Considerations: As a result of the success of surgical correction of TOF, most pregnant patients presenting with TOF will have already been surgically corrected. In the rare event that an uncorrected TOF patient arrives for labor and delivery, invasive monitoring is in order (arterial line and central venous pressure monitoring). In addition, a TTE or TEE may help to characterize the cardiac function. Corrected TOF patients may have varying levels of residual right ventricular failure and pulmonary hypertension (see section on pulmonary hypertension). Careful review of the patient’s history and medical records as well as consultation with the primary care physician, will help delineate the type of correction performed and the residual cardiac function. The following important considerations should be noted.
Decreases in vascular resistance, blood volume, or venous return are not well tolerated. A reduction in SVR increases right-to-left shunt, while a decline in blood volume or in venous return compromises right ventricular perfusion of the lungs. High central blood volumes are essential to maintain right ventricular output when this ventricle is compromised.
Myocardial depression may not be well tolerated. If right ventricular compromise is present, inotropic support (epinephrine/dopamine) may be necessary to offset the effects of even small amounts of myocardial depression.
Anesthesia for Vaginal Delivery and Cesarean Delivery
Vaginal Delivery: Decreases in SVR as associated with lumbar epidural or spinal anesthesia will worsen right-to-left shunts and therefore epidural/spinal anesthesia should be used with extreme caution. Injection of only narcotics (other than meperidine) into the epidural/spinal space may decrease the sympathectomy associated with local anesthetic use, but may not be effective. To blunt decreases in SVR and venous return, volume infusion and continuous left uterine displacement are recommended. Ephedrine should be administered cautiously because it may produce a marked increase in PVR. Vasopressin may be useful if the SVR is low. Labor and vaginal delivery in parturients with TOF is best managed with systemic medications, paracervical, or pudendal nerve block.
Cesarean Delivery: Continuous epidural or spinal anesthesia for cesarean delivery in patients with TOF may exacerbate right-to-left shunting as mentioned above. However, in corrected TOF patients with good functional status, slow, careful titration of an epidural or spinal anesthetic is reasonable and effective. Invasive monitoring with the use of an arterial line and central venous catheter is helpful to closely monitor fluid status and SVR. For patients with poor residual cardiac function or uncorrected TOF, general anesthesia using a combination of narcotics and low levels of inhalational anesthetics may provide the most stable hemodynamics. Invasive monitors and TEE are helpful adjuncts in assessing cardiac function, fluid status, and SVR. Vasopressin may be helpful when increases in SVR are needed with pre-existing pulmonary hypertension. PACs should not be used in patients with artificial pulmonic valves and/or pulmonary outflow grafts.
Complications: The presence of an increasing peripheral cyanosis in patients with uncorrected TOF but without infundibular obstruction usually indicates a decrease in SVR or increased right ventricular compromise. Treatment consists of delivering the maximum concentration of oxygen and decreasing the anesthetic depth.
Table 30-6 Eisenmenger’s Syndrome | ||||||
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In patients with a history of significant infundibular obstruction, an increase in peripheral cyanosis is typically precipitated by tachycardia, increased myocardial contractility, and/or decreased right ventricular volume. Treatment consists of increasing the depth of inhalational anesthesia, increasing venous return and central blood volume, and decreasing contractility and heart rate with the use of β-blockers (titration of esmolol, either bolus or infusion).
Eisenmenger’s Syndrome
Eisenmenger’s syndrome consists of pulmonary hypertension and a right-to-left or bidirectional shunt with peripheral cyanosis (68,69) (Table 30-6, Fig. 30-6). The shunt may be atrial, ventricular, or aortopulmonary. A left-to-right shunt reversal commonly occurs during the later stages of a PDA, VSD, and ASD (69). Approximately 3% of all patients with CHD are reported to have Eisenmenger’s syndrome; prognosis is poor for most of these patients, with survival beyond the age of 40 unlikely. Unfortunately, the condition of high pulmonary artery pressures with a fixed vascular resistance is not reversible by surgical intervention (51,68,70).
 Figure 30-6 Eisenmenger’s syndrome. |
Maternal outcomes in patients with Eisenmenger’s syndrome are poor. Major cardiovascular mortality including heart failure and death occur in up to 33.3% of parturients with Eisenmenger’s syndrome (19,51,53,61,62,63,71,72,73,74,75,76). Neonatal outcomes are poor as well, with almost two-thirds of deliveries occurring prematurely and elevated rates of fetal and perinatal mortality (9.5% and 18.2% mortality, respectively) (19).
Clinical Manifestations
Signs and Symptoms: Clinical manifestations of Eisenmenger’s syndrome depend on the degree of pulmonary hypertension and right-to-left shunt (2,43,53,69,73,77). The underlying defect directly influences the type of heart murmur that will be present (e.g., a systolic ejection murmur with ASD or a holosystolic murmur with VSD).
Test Indicators: ECG usually demonstrates right ventricular hypertrophy with right axis deviation. Chest x-ray typically reveals increased pulmonary artery markings with a prominent right ventricle. TEE usually displays signs of right-sided volume and work overload. Right atrial/ventricular enlargement is typically present. Decreased right and left ventricular contractility may be present. The underlying structural defect (ASD, VSD, etc.) may also be visualized on TEE.
Pathophysiology: The degree of right-to-left shunt depends on three factors: (a) The severity of the pulmonary hypertension and size of the right-to-left communication; (b) the relationship between the pulmonic and SVR, that is, increases in PVR or decreases in SVR exacerbate the right-to-left shunt, producing peripheral cyanosis; and (c) the contractile state of the right ventricle (progressive right ventricular dysfunction decreases pulmonary blood flow and increases right-to-left shunt).
Pregnancy-induced Changes: In Eisenmenger’s syndrome, PVR is fixed and is not altered with pregnancy. However, the SVR decreases as usual in pregnancy, markedly increasing the right-to-left shunt (5,61,78). Other cardiovascular changes associated with pregnancy including increases in heart rate, stroke volume, and blood volume, all contribute to increasing right ventricular oxygen consumption which in the presence of desaturated blood may lead to right ventricular compromise (43,78).
Anesthetic Considerations: All patients with Eisenmenger’s syndrome should be considered high risk and their care should be approached in a multidisciplinary fashion. Invasive monitoring with arterial and central venous access should be utilized. The principal concerns are the following.
Decreases in SVR or venous return are not well tolerated (see section on TOF).
Elevations in PVR are not well tolerated. Even minimal hypercarbia, acidosis, and hypoxia should be avoided and treated aggressively when they occur (see section on primary pulmonary hypertension).
Anesthesia for Vaginal Delivery and Cesarean Delivery
Anesthetic management of parturients with Eisenmenger’s syndrome is identical to that of patients with TOF. Regional anesthesia can be used in parturients with Eisenmenger’s, but should be done cautiously (79,80). Attempts to limit the sympathectomy associated with local anesthesia (epidural or spinal anesthesia) must be considered (i.e., slowly titrate epidural level, administration of vasopressin, or other vasopressor). Adjunct therapies for lowering the PVR have been used successfully in parturients with Eisenmenger’s syndrome. Inhaled nitric oxide and intravenous epoprostenol have both been utilized to assist in the care of parturients with Eisenmenger’s syndrome. However, their availability and experience in parturients is limited (81,82,83).
Table 30-7 Coarctation of Aorta | ||||||
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Other Congenital Heart Diseases
Coarctation of the Aorta
Coarctation of the aorta occurs in 4 to 4.4 per 10,000 of live births and represents approximately 8% of all CHD in adults (49,51,56) (Table 30-7). Most cases are surgically corrected in early childhood, decreasing the incidence of coarctation in the pregnant population. Parturients with corrected isolated coarctation of the aorta are not at increased risk for morbidity and mortality (5,19,84,85,86,87). Previous reports indicated that parturients with uncorrected coarctation had maternal mortality rates as high as 9%; however, recently published data report that these patients can undergo labor and delivery safely with no increase in maternal mortality (5,19,84,85,86,87,88,89,90,91,92,93,94).
Clinical Manifestations
Signs and Symptoms: Physical examination usually reveals a significant difference in blood pressures in the upper and lower extremities, or in the right and left upper extremities. Other signs include an increase in intensity of the aortic component of the second heart sound, a medium-pitched systolic blowing murmur (heard best between the scapulae), a ventricular heave, and a laterally displaced apical impulse. In pregnancy, aortic coarctation may present as unexplained hypertension during pregnancy (91,95).
Test Indicators: Late in the course of the disease, an ECG will demonstrate signs of LVH. A chest x-ray will demonstrate left ventricular enlargement and a characteristic “three” sign in the aortic knob. TEE may be used to evaluate the aorta as well as any coexisting cardiac disease (Fig. 30-7).
Cardiac catheterization is indicated for complicated cases and is useful in assessing the severity of the disease.
Figure 30-7 Descending aorta long-axis view demonstrating a narrowing of the descending aorta as seen in a patient with aortic coarctation.
Pathophysiology: Coarctation, like aortic stenosis, represents a fixed obstruction to left ventricular ejection. Stroke volume tends to be limited, and increases in cardiac output are achieved primarily through increases in heart rate. Due to increased left ventricular afterload, ventricular pressure work increases and concentric hypertrophy occurs. Patients with mild coarctation tolerate this well, and progression to ventricular dilation and failure occurs late in the course. With severe coarctation, ventricular changes occur earlier, along with pathologic changes in the arterial wall at the site of coarctation that serve as the nidus for dissection and rupture.
Pregnancy-induced Changes: Pregnancy may exacerbate both left ventricular compromise and vascular wall damage. Because stroke volume is limited, the increase in intravascular volume and metabolic demand associated with pregnancy is accommodated by increase in the heart rate. During labor and delivery, heart rate compensation may not be adequate, and left ventricular failure may occur. Pregnancy can also precipitate changes in the media and intima of the aorta, resulting in catastrophic complications (84,85). Aortic dissection, pseudoaneurysm formation, and aortic rupture may occur as a result of the physiologic alterations and vascular changes during pregnancy in patients with coarctation (86,96). Depending on the severity of aortic coarctation, the vasodilation associated with pregnancy may be poorly tolerated in patients with pre-existing hypotension below the level of coarctation resulting in decreased uterine blood flow. Finally, these patients have increased blood flow proximal to the aortic narrowing, and should be monitored for signs of intracranial hypertension, especially if preeclampsia is also present.
Anesthetic Considerations: Previously corrected patients and asymptomatic patients without evidence of cardiac enlargement or dysfunction can safely undergo labor and delivery without special considerations. Patients with coexisting cardiac disease or symptomatic lesions should have additional monitoring proportional to the level of their disease (radial and/or femoral artery monitoring, PA catheter, TEE). The following summarizes the anesthetic considerations for these patients.
Decreases in SVR are not well tolerated. Stroke volume is relatively fixed and therefore there is limited capacity to compensate for decreases in SVR. In addition, while blood flow proximal to the coarctation may be adequate, distal flow may be severely limited, and any further decreases may lead to critically low uterine/placental blood flow. Vasoconstrictors may be needed to offset any decreases of SVR associated with anesthetic use. It is important to monitor for awareness using devices such as the bispectral index monitor (BIS).
Decreases in heart rate are not well tolerated. When stroke volume is fixed, cardiac output becomes dependent on heart rate. Vagal stimulations, medications, or anesthetics which result in decreases in heart rate may be poorly tolerated and should be avoided. Decreases in heart rate should be treated by removing the causative stimulus and/or pharmacologic treatment with ephedrine or glycopyrrolate.
Decreases in left ventricular filling are not well tolerated. As stroke volume is relatively restricted by stenosis in the aorta, adequate end-diastolic volumes are critical in maintaining stroke volume. Avoid hypovolemia or other causes of decreased preload. Maintain sinus rhythm. Atrial fibrillation is particularly deleterious as it can cause loss of the atrial (“kick”) component of ventricular filling, which can seriously compromise cardiac output.
Anesthesia for Vaginal and Cesarean Delivery
Anesthetic management of patients with aortic coarctation is similar to the management of patients with aortic stenosis. Vaginal delivery can be safely achieved with the use of intravenous pain medications or local nerve blocks. Spinal anesthesia with only narcotic may also be used. A lumbar epidural anesthetic using a combination of low dose local anesthetic with a narcotic can be used, but should be titrated slowly with careful monitoring of maternal blood pressure and fetal heart rate. Fluid administration and vasopressors should be used if SVR is decreased.
Cesarean delivery can be accomplished with a balanced general anesthetic technique (nitrous oxide/inhalational agent/opioid/muscle relaxant) that maintains the anesthetic goals discussed above (94). Neuraxial techniques have been used for cesarean delivery but we recommend general anesthesia for patients with moderate-to-severe aortic coarctation (97). Invasive monitoring should be used in proportion to the patient’s disease severity. Patients with severe stenotic lesions may benefit from pre- and poststenotic blood pressure monitoring. If aortic dissection is present, consult the anesthetic considerations listed in the aortic dissection section.
Congenital Aortic Stenosis
Congenital aortic stenosis comprises lesions that may occur at the aortic, subvalvular, or supravalvular location (98,99,100,101). The supravalvular lesion has been described in the maternal rubella syndrome (102), where the narrowing occurs just distal to the coronary artery orifices. Subvalvular stenosis may be fibrous (subaortic membrane) or muscular (hypertrophic obstructive cardiomyopathy [HOCM]) in nature (101). The most common cause of congenital aortic stenosis is the bicuspid aortic valve, which occurs in 1% to 2% of the general population (103,104,105). Patients with bicuspid aortic valves often do not become symptomatic until later in life (105).
Effects on Pregnancy: Historically, the literature regarding pregnancy and aortic stenosis has been limited. However, several recent publications help to shed light on the effects of aortic stenosis on maternal and neonatal outcomes (19,106,107,108). Although mild-to-moderate aortic stenosis was not reported to be associated with increased mortality, it was associated with increased rates of maternal dysrhythmia, pulmonary edema, and worsening heart failure (up to 7.3%, 10%, and 7.3% respectively) (19,106,107,108). Additionally, one-in-seven deliveries among patients with aortic stenosis are associated with small-for-gestational-age infants (19,106,107,108).
Anesthetic Considerations: The anesthetic considerations for congenital cases of aortic stenosis are similar to those for acquired causes of aortic stenosis and are described in this chapter in the next section (Table 30-8).
Pulmonic Stenosis
The incidence of congenital pulmonic stenosis is 7.3/10,000 live births and comprises 10% to 12% of CHD in adults
(49,109) (Table 30-9). The region of stenosis is typically at the valve (90% of cases) (109). Most patients with isolated pulmonic stenosis do not develop symptoms until later in adult life (109). However, the subvalvular lesion that has a different pathophysiology can be progressive.
(49,109) (Table 30-9). The region of stenosis is typically at the valve (90% of cases) (109). Most patients with isolated pulmonic stenosis do not develop symptoms until later in adult life (109). However, the subvalvular lesion that has a different pathophysiology can be progressive.
Table 30-8 Aortic Stenosis | ||||||
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Table 30-9 Congenital Pulmonic Stenosis | ||||||
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Effects on Pregnancy: The literature on the effects of pulmonic stenosis on pregnancy is limited. One large review of 81 pregnancies found no increased risk of maternal mortality, but did find increased rates of thromboembolic events (3.7%), hypertensive disorders of pregnancy (14.8%), premature delivery (16%), and increased infant mortality (4.8%) (110).
Clinical Manifestations
Signs and Symptoms: Severe right ventricular failure decreases left ventricular output, producing symptoms of fatigue and syncope. Auscultation reveals a normal first heart sound and a widely split second sound; a systolic ejection murmur is also present. As the degree of pulmonic stenosis worsens, the murmur increases in duration and has a late systolic accentuation.
Test Indicators: ECG usually demonstrates right axis deviation and right ventricular hypertrophy. With severe stenosis, a predominant R wave occurs in lead V1 that usually exceeds 20 mm in height (111), and correlates with a right ventricular systolic pressure of at least 80 mm Hg (112). Right ventricular strain manifested by negative T waves in the right precordial leads also may occur. Chest x-ray reveals dilation of the main pulmonary artery and reduced peripheral pulmonary vascular markings (109).
Pathophysiology: With progressive stenosis of the right ventricular outflow tract, pressure work increases and concentric hypertrophy occurs. The right ventricle compensates until late in the disease when systolic pressure exceeds 80 mm Hg (113). As right ventricular output decreases, so does left ventricular preload and thus cardiac output. SVR increases in an effort to compensate for decreased left ventricular output. However, as right ventricular failure progresses, further decreases in cardiac output are uncompensated, and symptoms of low cardiac output, such as fatigue and syncope, occur with exercise and later at rest.
Pregnancy-induced Changes: Many patients with isolated pulmonic stenosis will not develop symptoms until after childbearing age; however, patients with advanced disease are susceptible to the stresses involved in pregnancy and delivery. Increases in intravascular volume and heart rate associated with pregnancy can precipitate right ventricular failure. Decreases in SVR seen with pregnancy may counteract compensatory mechanisms triggered by during low ventricular output states.
Anesthetic Considerations: Patients with asymptomatic disease and no symptoms of right ventricular compromise can be managed in the standard fashion. Patients with advanced disease or signs of compromise should have invasive monitoring including arterial monitoring and central venous access in proportion to their disease level. The following considerations should be noted.
Marked increases or decreases in right ventricular filling pressure are not well tolerated. Right ventricular filling pressures must be maintained to ensure adequate stroke volume. Excessive preload can overdistend the right ventricle leading to right ventricular failure. Too little volume in the right ventricle may lead to ineffective contraction and decreased preload to the left ventricle.
Decreases in heart rate are not well tolerated. Because of the presence of right ventricular outflow stenosis, stroke volume is relatively fixed. Therefore, cardiac output is reliant on maintaining an adequate heart rate. Decreases in heart rate should be treated quickly with positive chronotropic drugs. Anesthetic agents and levels should be chosen to limit decreases in heart rate.
Marked decreases in SVR may not be tolerated. In patients with severe pulmonic stenosis, cardiac output is limited and systemic blood pressure is preserved by compensatory increases in SVR. Maintaining SVR by the use of vasoconstrictors such as ephedrine is necessary.
Negative inotropes may not be well tolerated. Any agents that decrease the contractile function of the right ventricle may be poorly tolerated and lead to ventricular failure. Use of medications or techniques with positive inotropic action is therefore recommended.
Anesthesia for Vaginal Delivery and Cesarean Delivery
Vaginal Delivery: Patients with mild disease can be managed in the normal fashion while those with more severe disease should be managed with techniques that optimize the anesthetic considerations discussed previously. Systemic medications or local blocks (pudendal, paracervical) should be used for vaginal delivery. Spinal anesthesia utilizing only opioids (other than meperidine) satisfies many of the criteria listed above. Epidural or spinal anesthesia using a combination of local anesthetic and narcotics can be utilized; however, care should be taken to maintain the physiologic parameters mentioned above. Preload should be maintained with volume loading prior to the onset of the sympathectomy; vasoconstrictors should be readily available to maintain system vascular resistance.
Cesarean Delivery: Careful titration of epidural anesthesia with the use in invasive arterial monitoring (central venous access should be considered) can be safely used (114). The level of anesthesia should be slowly titrated with careful following of the heart rate, preload, and systemic blood pressure. General anesthesia using predominantly nitrous oxide/narcotic/muscle relaxant combination may help maintain adequate heart rate, preload, and myocardial contractility. If right ventricular failure develops, anesthetic concentration should be reduced and inotropes administered.
Asymmetric Septal Hypertrophy
Also known as idiopathic hypertrophic subaortic stenosis, this condition typically manifests in the third or fourth decade (See Table 30-10 and Fig. 30-8). It is characterized by marked
hypertrophy of the ventricle, involving the interventricular septum and outflow tract. During ventricular systole, constriction of the outflow tract occurs, producing obstruction to ventricular ejection.
hypertrophy of the ventricle, involving the interventricular septum and outflow tract. During ventricular systole, constriction of the outflow tract occurs, producing obstruction to ventricular ejection.
Table 30-10 Asymmetric Septal Hypertrophy | |||||||
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 Figure 30-8 Asymmetric septal hypertrophy. |
Clinical Manifestations
Patient develops exertional dyspnea, angina pectoris, and syncope. Late in the course of the disease, left ventricular failure occurs. Physical examination reveals a double apical impulse and a systolic murmer best heard at the apex.
Test Indicators: Chest x-ray shows cardiomegaly and ECG evidence of LVH and a Wolff–Parkinson–White syndrome or abnormal Q waves in inferior or left precordial leads are seen. ECG will reveal a ventricular septum that is disproportionately hypertrophied compared with the posterobasal left ventricular free wall.
Pathophysiology: Patients with asymmetric septal hypertrophy (ASH) involving the left ventricle (LV) exhibit a marked hypertrophy of the entire LV, with bulging of the ventricular myocardium in the septal region several centimeters below the aortic valve. The ventricular cavity is relatively small. With each systolic contraction, the muscle around the outflow tract constricts and left ventricular ejection is obstructed. Progression of LVH eventually leads to ventricular failure.
Anesthetic Considerations: Decreases in preload are not well tolerated. Maintaining slight hypervolemia is recommended because the increase in ventricular volume tends to decrease the amount of outflow obstruction.
Tachycardia and dysrhythmias are not well tolerated. There is decreased time for ventricular filling and immediate treatment with β-blockers to slow heart rate or direct cardioversion is advocated.
Increases in contractility and decreases in SVR are not well tolerated as it may markedly increase outflow obstruction.
Treatment of ventricular failure in patients with ASH is to increase preload and afterload, and slow heart rate and contractility, which is different from the treatment of other types of heart failure.
Management of Labor and Delivery
Pregnancy and delivery are usually well tolerated in patients with ASH despite decrease in SVR and the risk of impaired venous return owing to uterine compression of the inferior vena cava. They present a major anesthetic challenge at term, as bearing down (Valsalva maneuver) may increase LVOT obstruction. Although general anesthesia is preferred in these patients, there are case reports where epidural anesthesia has been successfully used with CVP monitoring (115). Oxytocin must be administered carefully because of its vasodilating properties and compensatory tachycardia. Pulmonary edema has been observed in parturients with HCM after delivery, emphasizing the judicious fluid management in these patients (116).
Acquired Heart Disease
Rheumatic Heart Disease
Rheumatic fever is a diffuse inflammatory disease affecting the heart, joints, and subcutaneous tissues following group A β-hemolytic streptococcal infection. Acute rheumatic fever is evidenced by a history of streptococcal infection and subsequent clinical picture that usually includes recurrent migratory polyarthritis with or without carditis, which can progressively and permanently damage the valves or heart muscle. Although the prophylactic administration of antibiotics generally prevents the sequelae of rheumatic fever; RHD continues to be a common cause of death in the United States and in many other countries (43,117,118,119,120,121,122).
Left or right ventricular failure, atrial dysrhythmias, systemic or pulmonary embolism, and infective endocarditis may complicate RHD during pregnancy. The most common sequelae in parturients are mitral valve stenosis, regurgitation or prolapse, and/or aortic valve stenosis or regurgitation.
Mitral Stenosis
Rheumatic mitral valve stenosis is the most frequent RHD encountered in the pregnant population worldwide (Figs. 30-9 and 30-10) (Table 30-11). Mitral stenosis is the lesion
that most frequently requires therapeutic intervention during pregnancy.
that most frequently requires therapeutic intervention during pregnancy.
 Figure 30-9 Mitral stenosis. |
Clinical Manifestations
Signs and Symptoms: The initial symptoms are fatigue and dyspnea progressing to paroxysmal nocturnal dyspnea, orthopnea, and dyspnea at rest. Hemoptysis with rupture of bronchopulmonary varices can occur. In severe mitral stenosis, superimposition of atrial fibrillation, pulmonary embolism, infection, or pregnancy can cause rapid decompensation.
 Figure 30-10 Mid-esophageal four chamber view demonstrating an enlarged left atrium and thickened, restricted mitral valve leaflets in a patient with RHD. Note the thickening of the mitral valve leaflets is primarily at the leaflet tips resulting in the characteristic “hockey stick” deformation of the mitral valve leaflets classically seen with RHD. LA, Left atrium; MV, Mitral valve; LV, Left ventricle; RA, Right atrium; RV, Right ventricle. |
Physical examination may reveal a presystolic or middiastolic murmur. In addition to the murmur, an opening snap may be heard at the base of the heart along the left sternal border. Approximately, one-third of patients with mitral stenosis develop atrial fibrillation.
Test Indicators: Radiologic studies that may be normal early in the disease will show left atrial and right ventricular enlargement as the disease progresses. Severe mitral stenosis will result in pulmonary edema on chest x-ray. The ECG typically indicates broad P waves in lead V1, signifying left atrial enlargement. Right axis deviation signifies right atrial enlargement. Cardiac catheterization shows elevated pulmonary capillary wedge pressures of 25 to 30 mm Hg (normally 0 to 12 mm Hg) occurring when the mitral valve orifice is less than 2 cm2. There is an associated increase in PVR (117,123,124).
Echocardiographic Examination for Mitral Stenosis: Normally, the area of the mitral valve is between 4 and 6 cm2. When the area is reduced to less than 2 cm2, the transvalvular pressure gradient is increased. Continuous wave Doppler ultrasound should be used to measure the velocity of blood flow across the mitral valve (the use of pulse wave Doppler may result in “aliasing” at high-velocity blood flow). After
measuring the velocity, the transvalvular pressure gradient can be estimated by using the modified Bernoulli equation. Mean gradient is more precise and clinically relevant. Mean gradients in the range of 5 to 10 mm Hg are consistent with moderate mitral stenosis; mean gradients above 10 mm Hg are consistent with severe mitral stenosis (125).
Table 30-11 Mitral Stenosis
Hemodynamic Goals
Prevent rapid ventricular rates
Minimize increase in central blood volume
Avoid marked decreases in SVR
Prevent increases in pulmonary artery pressure
SVR, Systemic Vascular Resistance.
Figure 30-11 Pathophysiology of mitral stenosis.
Two other echocardiographic evaluations are useful in estimating the severity of mitral stenosis.
The measurement of mitral valve pressure half–time (i.e., the time it takes for the transvalvular pressure gradient to decrease to 50% of its maximum value). Mitral valve area of 1 to 1.5 cm2 is consistent with moderate mitral stenosis and an area less than 1 cm2 is consistent with severe mitral stenosis.
The area of the mitral valve orifice also can be estimated using planimetry. The opening of the mitral valve can be visualized and the area traced to provide an estimation of the MVA. Severe calcification of the mitral valve may interfere with a determination of its area by planimetry, and in patients with significant subvalvular stenosis, the degree of hemodynamic compromise may be underestimated.
Pathophysiology: The decrease in mitral valve orifice area impairs left ventricular filling, which will cause left atrial enlargement and increases in left atrial volume and pressures. This causes increased pressure in the pulmonary circulation, increased pulmonary capillary wedge pressures, and pulmonary edema. Compensatory RV hypertrophy leads to right heart failure. Factors aggravating this situation are tachycardia, atrial fibrillation, and increased preload (Figs. 30-11 and 30-12).
Pregnancy-induced Changes: Prognosis depends on the severity of the valve stenosis, heart rate and rhythm, atrial compliance, circulating blood volume, and pulmonary vascular response. A narrowed mitral valve orifice allows a relatively fixed amount of blood to move across during diastole. Thus, when cardiac output and blood volume increase during pregnancy and the mitral valve stenotic, left atrial pressure is markedly increased. Additionally, increased cardiac output increases the transmitral pressure gradient, which worsens symptoms of congestive heart failure and eventually leads to pulmonary edema and respiratory distress.
With pregnancy, an anatomically moderate stenosis can become functionally severe. Pregnant patients with mitral stenosis can have an increased incidence of pulmonary congestion (25%), atrial fibrillation (7%), and paroxysmal atrial tachycardia (3%) (88). Left ventricular dysfunction is very uncommon in pure mitral stenosis and its presence suggests coexisting mitral or aortic insufficiency.
During pregnancy and labor, the increased heart rate, increased cardiac output and demand, and decreased ventricular filling causes back pressure in the pulmonary circulation and risk for pulmonary edema. Immediately after delivery is the most likely time for decompensation and pulmonary
edema due to tachycardia and increased preload from autotransfusion.
edema due to tachycardia and increased preload from autotransfusion.
 Figure 30-12 Pressure gradient across the stenotic mitral valve. |
Anesthetic Considerations: Patients with a mitral orifice area of less than 1.5 cm2 can be treated medically, whereas parturients with severe stenosis may require percutaneous mitral balloon valvotomy, a procedure with a low complication rate in experienced hands. Closed and open mitral commissurotomy have been performed with low maternal risk and a fetal survival of greater than 90% (126).Related posts:
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