Congenital heart disease (CHD) is common, occurring—if bicuspid aortic valve (AV) is excluded—in approximately 1% of all live births. The most common defects and the incidence of each are outlined in Table 14-1 . Approximately 85% of patients with CHD now survive to adulthood, which has resulted in more adults than children with CHD. Recent estimates indicate there are approximately 1 million adults with CHD in the United States.
| Lesion | Incidence/1000 Live Births |
|---|---|
| VSD | 3.57 ± 2.9 |
| ASD | 0.94 ± 1.0 |
| Patent ductus arteriosus | 0.80 ± 1.4 |
| Pulmonary stenosis | 0.73 ± 0.73 |
| Tetralogy of Fallot | 0.42 ± 0.19 |
| Coarctation of the aorta | 0.41 ± 0.25 |
| Aortic stenosis | 0.40 ± 0.54 |
| Atrioventricular septal defects | 0.35 ± 0.16 |
| d-Transposition of the great arteries | 0.32 ± 0.12 |
| Hypoplastic left heart | 0.27 ± 0.22 |
| Hypoplastic right heart | 0.22 ± 0.20 |
| Double-outlet right ventricle | 0.16 ± 0.10 |
| Pulmonary atresia | 0.13 ± 0.12 |
| Ebstein anomaly | 0.11 ± 0.14 |
| Truncus arteriosus | 0.11 ± 0.07 |
| Tricuspid atresia | 0.08 ± 0.05 |
Adults with CHD present to anesthesiologists for various reasons, including the following:
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Cardiac surgery for the first time, including palliative or definitive surgery
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Cardiac reoperation for further palliation or definitive correction after palliative surgery
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Cardiac surgery for management of residual defects or complications of prior interventions
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Noncardiac surgery or procedures in the presence of uncorrected, palliated, or corrected lesions
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Conscious sedation or general anesthesia for TEE, usually before electrical cardioversion
Because of the increased perioperative risk associated with cardiac and noncardiac surgery in adults with CHD, certain patients—such as those with prior Fontan repair, severe pulmonary hypertension, complex lesions, or cyanotic heart disease—should be managed in specialist centers.
Ventricular septal defects
Ventricular septal defects (VSD) is the most common congenital heart defect at birth, accounting for nearly 30% of all cases of CHD (excluding bicuspid AV).
Large VSDs cause volume loading of the left heart and increased flow through the pulmonary circulation. Shunting across the VSD is from left to right. However, over time, increased flow through the pulmonary circulation from a large uncorrected VSD can lead to pulmonary vascular obstructive disease. Elevated pulmonary vascular resistance (PVR) pressurizes the right heart, which can lead to bidirectional or reversed (i.e., right to left) shunting across the VSD. Right-to-left shunting in association with severely elevated PVR is termed Eisenmenger syndrome. Once Eisenmenger syndrome has developed, closure of the VSD results in acute RV failure and is therefore contraindicated.
By adulthood, most VSDs either have closed spontaneously or have been surgically corrected. Thus, adults with a VSD usually have either a small defect of no hemodynamic significance or a large defect with severe pulmonary vascular obstructive disease to the extent that repair is contraindicated. However, even for small VSDs, serious complications may occur during extended follow-up, including endocarditis, progressive aortic regurgitation, and rhythm disturbances, most commonly atrial fibrillation.
Anatomy and classification of ventricular septal defects
The anatomy of the ventricular septum is complex, and the classification and terminology of VSDs is confusing. Broadly, there are four anatomic types ( Figure 14-1 ), with multiple synonyms for each ( Table 14-2 ). The ventricular septum is composed of membranous and muscular portions. The membranous septum is small and located directly below the AV. The right ventricular (RV) surface is adjacent to the septal leaflet of the tricuspid valve (TV). The left ventricular (LV) surface forms the superior border of the left ventricular outflow tract (LVOT). The rest of the septum is muscular. Three regions of muscular septum are identified: (1) the inlet septum, which lies posterior to the membranous septum and inferior to the atrioventricular valves; (2) the trabecular septum, which extends from the membranous septum toward the cardiac apex; and (3) the outlet septum, which extends anteriorly from the membranous septum and lies above the trabecular septum and below the great arteries.
| Common Term | Synonyms |
|---|---|
| Perimembranous | Membranous, conoventricular |
| Inlet | Atrioventricular canal type |
| Trabecular | Muscular |
| Outlet | Conal, subpulmonary, infundibular, supracristal, subarterial, doubly committed |
The most common type of VSD is perimembranous, constituting 70% of VSDs. Perimembranous VSDs are adjacent to the septal leaflet of the TV, which can become adherent to the defect limiting left-to-right shunt. Perimembranous VSDs are associated with AV prolapse and regurgitation. The VSD present in tetralogy of Fallot is perimembranous. Inlet VSDs constitute 5% of VSDs. They involve the inlet of the ventricular septum immediately inferior to the atrioventricular valve apparatus. Inlet defects typically occur in patients with Down syndrome and are associated with primum atrial septal defects (ASDs) and defects of the atrioventricular valves. Trabecular defects constitute 20% of VSDs. They may be midmuscular, apical, posterior, or anterior and may be single or multiple (“Swiss cheese” VSD). Outlet VSDs constitute 5% of VSDs. They lie in the outflow portion of the right ventricle beneath the semilunar valves and above the crista supraventricularis. They are also associated with AV prolapse and regurgitation.
Echocardiography
Preoperatively, echocardiography is used to determine (1) the number and location of the defects, (2) ventricular function, (3) the presence and severity of AV prolapse and regurgitation, (4) the presence and severity of tricuspid regurgitation, (5) shunt fraction (6), pulmonary arterial pressure, and (7) the presence of any associated congenital lesions.
Both perimembranous and outlet VSDs communicate with the LVOT and can be visualized in the midesophageal RV inflow–outflow view ( Figure 14-2 ). Perimembranous defects can be seen adjacent to the TV, and outlet defects can be seen adjacent to the pulmonary vein (PV). Both of these VSDs, but particularly outlet defects, can lead to prolapse of the adjacent AV cusp and AV regurgitation.
Inlet and midmuscular defects may be visible in the midesophageal four-chamber view ( Figure 14-3 ) or transgastric short-axis view. In the midesophageal four-chamber view, an inlet VSD can be seen adjacent to the septal leaflet of the TV. If an inlet VSD is identified, other features of an atrioventricular canal defect should also be sought (described later). Apical and midtrabecular VSDs are often difficult to visualize with two-dimensional (2-D) imaging because of the distance of the apical septum from the transducer and because, with transesophageal echocardiography (TEE), the ventricular septum is parallel to the ultrasound beam. Apical or midmuscular defects may be seen in the deep transgastric view.
Defects that are not well seen with 2-D imaging may be more obvious with color flow Doppler, particularly midmuscular and apical VSDs. Color flow Doppler is also useful to assess the direction and velocity of flow. Shunting occurs predominantly in systole and is normally left to right. Turbulent flow or marked flow convergence (aliasing) on the LV side of the VSD indicates a high velocity jet and suggests a small defect that is restrictive to flow. By contrast, laminar flow and the absence of aliasing suggest a large, unrestrictive defect. High PVR is inferred from bidirectional or right-to-left shunting and is typically associated with large unrestrictive defects that have not been closed in childhood. Interrogation of the defect with continuous wave (CW) Doppler is also useful to determine the physiologic significance of the lesion: large VSDs that are unrestrictive to flow are associated with low velocities (typically <2 m/sec), whereas small VSDs that are restrictive to flow are associated with high velocities (typically >4 m/sec).
With large, uncorrected VSDs, left atrial (LA) and LV volumes are typically increased. Right atrial (RA) and RV volumes are often normal. However, in the presence of severe pulmonary hypertension, there may also be signs of RV pressure overload (RV hypertrophy and paradoxical motion of the ventricular septum) ( Chapter 13 ) and RV systolic dysfunction. Severe RV systolic dysfunction is uncommon but occurs in the late stages of Eisenmenger syndrome.
Spectral Doppler can also be used to estimate pulmonary arterial systolic pressure and to calculate the shunt fraction (see Chapter 21 ). RV systolic pressure, and therefore pulmonary arterial systolic pressure, can be estimated by two methods: (1) from the peak tricuspid regurgitant velocity and RA pressure (see Equation 21-23 ) and (2) as the difference between the systemic systolic blood pressure and the calculated systolic pressure difference between the two ventricles using the peak velocity of the VSD flow (see page 349 ). Shunt fraction can be estimated by dividing the right-sided stroke volume by the left-sided stroke volume (see Equation 21-13 ). In general, a shunt fraction ratio greater than 1.5:1 (i.e., pulmonary blood flow > 1.5 times systemic blood flow) implies a physiologically significant defect that should be closed in childhood.
Following surgical patch closure of a VSD, it is important to carefully inspect the ventricular septum with 2-D and color flow Doppler to rule out residual flow across the defect and identify any other defects that might be manifested only after closure of the dominant lesion.
Atrial septal defects and anomalous venous connections
Defects in the atrial septum comprise up to 10% of all congenital cardiac anomalies (excluding bicuspid AV). ASDs are associated with right-sided volume overload that is usually well tolerated and frequently results in only minor limitation in exercise tolerance. ASDs are often discovered as an incidental finding. However, with each passing decade, the risks of developing atrial arrhythmias (as a consequence of atrial dilatation), RV dysfunction, and less commonly, pulmonary hypertension increase. (In contrast to VSDs, severe pulmonary hypertension is uncommon, even with large ASDs.) ASDs are associated with an increased risk of cerebral events due to paradoxical embolism.
Anatomy, classification, and associations of atrial septal defects
ASDs may occur in isolation, may be fenestrated or multiple, and are associated with other congenital cardiac lesions in 30% of cases ( Table 14-3 ). Four main types of ASD are recognized based on their anatomic location in the atrial septum ( Figure 14-4 ): secundum, primum, sinus venosus, and coronary sinus.
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