Santiago O. Valdes1, Jeffrey J. Kim1, and Wanda C. Miller‐Hance2,3 1 Department of Pediatrics, Section of Cardiology, Electrophysiology and Pacing, Texas Children’s Hospital, Houston, TX, USA 2 Department of Anesthesiology, Perioperative and Pain Medicine, Arthur S. Keats Division of Pediatric Cardiovascular Anesthesiology, Baylor College of Medicine and Texas Children’s Hospital, Houston, TX, USA 3 Department of Pediatrics, Section of Cardiology, Baylor College of Medicine and Texas Children’s Hospital, Houston, TX, USA The practice of pediatric cardiovascular anesthesiology has evolved significantly over the years, expanding beyond the operative setting to many non‐surgical environments. Anesthetic care for infants, children, and adolescents who have or are at risk for, cardiac rhythm disturbances is now provided at various locations, including operating rooms, critical care units, emergency facilities, treatment rooms, and cardiac catheterization/electrophysiology laboratories. The same is true for other patients with congenital heart disease (CHD) beyond childhood. General knowledge of arrhythmia diagnosis and management is essential for anesthetic care in any of these settings, although in some cases, consultation with a specialist is required. This chapter provides a practical approach to pediatric cardiac arrhythmias and rhythm disturbances most commonly affecting patients with CHD, focusing on the diagnosis, mechanisms, and acute management strategies. A brief review of anti‐arrhythmic drug (AAD) therapies and the basic principles of cardiac pacing in children, as applicable to the practice of anesthesia, is also presented. Sinus bradycardia is characterized by a heart rate below the norm for the patient’s age and by a normal, sinus P wave. Slow heart rates can be observed during sleep or may be secondary to a high vagal tone. During significant sinus bradycardia, an escape rhythm may arise from the atrium, junction, or ventricle. In otherwise healthy children, this is usually a benign rhythm with no hemodynamic consequences. Patients with certain forms of CHD, however, are more prone to slow heart rhythms that may indeed be clinically significant. Those with heterotaxy syndromes are included in this category because of the absence, displacement, or hypoplasia of the true sinus node in these patients [1]. Intraoperatively, sinus bradycardia can result from vagal stimulation during induction of anesthesia, laryngoscopy, endotracheal intubation, or tracheal suctioning. Sinus bradycardia may also be related to drug administration (e.g., opioids) or other mechanisms of increased parasympathetic activity. This type of sinus bradycardia rarely results in significant hemodynamic compromise and can usually be treated by removing the stimulus or by administering a chronotropic agent such as atropine or epinephrine (See Box 22.1). Slow sinus rates can be seen during cardiac surgical manipulations around the sinus node or after interventions such as the closure of atrial septal defects (ASDs) and cardiac transplantation. Sinus bradycardia can also be due to hypoxemia, hypothermia, hypotension, drugs, acidosis, electrolyte abnormalities, or increased intracranial pressure. Hypoxemia‐related bradycardia should be treated promptly with oxygenation and ventilation as appropriate. The approach to other forms of secondary sinus bradycardia should focus on addressing the underlying cause. For worrisome low heart rates, particularly in small infants, drugs such as atropine or glycopyrrolate, should be considered. Ongoing bradycardia with clinical evidence of compromised cardiac output requires immediate escalation of therapy that, in most cases, includes epinephrine administration, cardiopulmonary resuscitation, and consideration of temporary pacing. A low atrial rhythm is characterized by atrial activation that spreads upward from a focus on the low atrium. The electrocardiogram (ECG) shows inverted P waves in the inferior leads (II, III, and aVF). A slow atrial rhythm implies that another region of the heart has assumed the pacemaker activity of the sinus node. Although this rhythm may be associated with conditions that affect sinus node function intraoperatively, it is most commonly the result of surgical manipulation (Figure 22.1). In most individuals, this is a normal variant and rarely has a hemodynamic consequence. Sinus node dysfunction often termed sick sinus syndrome, encompasses a spectrum of disorders characterized by slow or irregular heart rates that have a variety of escape rhythms and that frequently alternate with the periods of tachycardia. The respondent’s tachycardia may be atrial tachycardia, atrial flutter, or atrial fibrillation. The term tachycardia‐bradycardia syndrome is frequently used to characterize this association. The surgical interventions most likely to be associated with sinus node dysfunction include extensive atrial baffling procedures, such as Mustard and Senning operations, and the Fontan procedure. The management of symptomatic patients may include pacemaker implantation, pharmacological therapy for tachyarrhythmias, atrial anti‐tachycardia pacing (ATP), and, in some cases, transcatheter or surgical ablation. Sinus tachycardia is more commonly seen in the perioperative period than sinus bradycardia. It is often the result of painful stimuli or stress, hypovolemia, anemia, medications (e.g., inotropic agents), a high catecholamine state, surgical manipulation, or fever. Sinus tachycardia can often be differentiated from pathologic supraventricular arrhythmias by its variability in rate and its normal P‐wave axis. Treatment is directed at the underlying cause. Prolonged periods of sinus tachycardia may impair diastolic filling time, limit ventricular preload, and compromise systemic cardiac output. Patients at higher risk of hemodynamic compromise have substantial ventricular hypertrophy or non‐compliant (“stiff”) ventricles with associated diastolic dysfunction, such as in certain types of cardiomyopathies or obstructive outflow lesions (e.g., tetralogy of Fallot). Junctional rhythm is characterized by QRS complexes with a morphology identical to that of sinus rhythm without preceding P waves. This arrhythmia is thought to originate in the bundle of His. It often occurs in patients with sinus bradycardia or with sinus node dysfunction. In this rhythm, there is normal atrioventricular (AV) nodal conduction, but it is sometimes difficult to determine if the junctional beats are slightly faster than the atrial beats or there is 1 : 1 ventriculoatrial (V:A) conduction retrograde through the AV node. During surgery, this may occur as a result of cardiac manipulation and dissection around the right atrium. In addition to the ECG features described above, the arterial and venous pressure waveforms can change during junctional rhythm (Figure 22.2). The central venous pressure tracing may show a tall a wave, termed as cannon a wave, which is due to late atrial contraction against a closed tricuspid valve. An associated decrease in stroke volume and cardiac output, resulting from the absence of the normal atrial systolic contribution to ventricular filling, may manifest as a reduction in systemic arterial blood pressure. Temporary atrial pacing at 10–20 beats/min (bpm) above the junctional rate can be used to document normal AV nodal conduction, and it frequently restores AV synchrony. In an unoperated patient, bundle branch block is an uncommon ECG finding. An incomplete right bundle branch block (RBBB) pattern or intraventricular conduction delay can be seen in patients with right ventricular volume overload (e.g., ASDs, anomalous pulmonary venous drainage). In rare cases, an RBBB can be congenital and idiopathic. An RBBB pattern is frequently seen in postoperative patients after interventions for lesions such as tetralogy of Fallot, right ventricular outflow tract pathology, and AV septal defect (AVSD; also referred to as AV canal or endocardial cushion defect). This conduction abnormality may be related to a ventriculotomy incision, resection of infundibular muscle, damage to the moderator band, or, in some cases, closure of a ventricular septal defect (VSD). A left bundle branch block (LBBB) pattern is uncommon but may be found after surgical procedures involving the left ventricular outflow tract. First‐degree AV block is characterized by a prolonged PR interval beyond what is considered normal for age. Each P wave is followed by a conducted QRS complex. This type of rhythm disturbance can be a normal variant in healthy individuals but can also be seen in a variety of disease states (e.g., structural heart defects associated with stretching of the atria, rheumatic fever). In general, a prolonged PR interval in an otherwise healthy child is a benign condition and requires no treatment. There are four types of second‐degree AV block. The two predominant types, Mobitz type I (Wenckebach) and Mobitz type II, involve a periodic failure to conduct atrial impulses to the ventricle. In type I second‐degree AV block, the PR interval lengthens progressively until the next atrial impulse cannot be conducted to the ventricle. These failures of conduction manifest on the surface ECG as P waves without associated QRS complexes and concomitant shortening of the RR intervals (Figure 22.3). This rhythm disturbance can occur during periods of high vagal tone and is generally considered a benign phenomenon that requires no therapy. In the less frequent type II second‐degree AV block, there is a constant PR interval before an atrial impulse that suddenly fails to conduct. This conduction abnormality is more concerning because of its potential for progression. It can be seen in patients after surgery for CHD and is thought to be due to damage to the His bundle or distal conduction system. The third type of second‐degree AV block is two to one AV block (2:1). In 2:1, every second P wave is blocked. In most cases, this is a type of Mobitz type I or Wenckebach block and is secondary to high vagal tone. It is rare for 2:1 to progress to a higher degree of AV block or to require treatment. The fourth type of second‐degree AV block is a high‐grade AV block, which is evidenced by two or more non‐conducted P waves in succession that would normally be expected to conduct. Temporary pacing and close patient observation may be warranted because hemodynamically significant bradycardia or continued progression of the conduction deficit may ensue. Third‐degree AV block is characterized by the total failure of atrial impulses to be conducted to the ventricles. There is complete dissociation of the electrical activity between the atria and ventricles, and the ventricular rate is usually slow and regular. In third‐degree AV block, the ventricular escape rate may be narrow (if originating from the perinodal region) or wide (if originating from within the ventricle). The diagnostic feature on the ECG is that all atrial impulses that should be conducted to the ventricle fail to do so (Figure 22.4). Complete AV block may be either congenital or acquired. Congenital complete AV block in infants with otherwise structurally normal hearts may be due to intrauterine exposure to maternal antibodies associated with collagen vascular diseases (e.g., lupus). Patients at high risk of complete AV block include those with congenitally corrected transposition (L‐transposition of the great arteries with ventricular inversion) and those with polysplenia (left atrial isomerism) [1]. Acquired postoperative AV block is thought to result from damage to the compact AV node or bundle of His and may be transient or permanent. The surgical procedures most commonly associated with the onset of complete AV block include repair of AVSD, closure of VSD, resection of obstructive subaortic tissue, and interventions in patients with congenitally corrected transposition [2]. In children, reported incidences of surgical AV block are as high as 2–4%. Normal conduction eventually recovers in more than 60% of patients, usually within the first 10 postoperative days [3, 4]. Acute treatment includes temporary pacing (either AV sequential pacing or ventricular pacing only). If the rate of the junctional escape rhythm is high enough to support stable hemodynamics, temporary pacing can be set as a backup with close monitoring of the underlying cardiac rhythm. Important considerations in patients with surgical AV block include careful surveillance for the return of AV conduction and frequent evaluation of temporary pacing wire thresholds. The ventricular output of the temporary pacemaker should be set well above the capture threshold to increase the margin of safety (please refer to the section on temporary pacing). Permanent cardiac pacing is generally indicated in patients who do not recover from complete AV block within 10–14 days after surgical intervention. A small minority of patients have late recovery of their native AV nodal conduction after surgically acquired complete AV block [3, 4]. When providing anesthetic care to a patient with complete AV block but no implanted pacemaker, the following should be considered: Isolated premature atrial contractions (PACs) are relatively common in infants and small children. The early P waves frequently have an abnormal axis and morphology and are typically followed by a normal QRS complex. Atrial bigeminy is characterized by a PAC that follows every sinus beat (Figure 22.5). On occasion, the PACs block at the AV node or conduct aberrantly, displaying an abnormally wide QRS. Blocked PACs can mimic bradycardia, and aberrantly conducted PACs can resemble ventricular ectopy. Most PACs are benign, requiring no therapy. An investigation may be warranted in cases of symptomatic, frequent, or complex (multifocal) PACs. This type of rhythm can be the result of irritation from a central venous catheter or other type of intracardiac line. Radiographic or echocardiographic assessment of catheter/wire tip position should be considered because appropriate adjustments can eliminate the atrial ectopy. Supraventricular tachycardia (SVT) is the most common clinically significant arrhythmia in infants and children. This rhythm disturbance is characterized by a narrow or “usual” complex QRS morphology and can occur in structurally normal hearts, as well as in various forms of CHD. “Usual” complex describes a QRS morphology in tachycardia similar to that seen during normal sinus rhythm. This is important because patients with CHD often have abnormalities on their baseline ECG, including a bundle branch block pattern. On occasion, widening of the QRS duration in SVT can be due to aberrancy in the right or left bundle branches or to the tachycardia mechanism itself (i.e., antidromic SVT; refer to the discussion later in this chapter). When the QRS complex is wide, distinguishing between supraventricular and ventricular tachycardia can be challenging. Two general categories of SVT are recognized: automatic and reentrant. These can be differentiated by evaluating characteristics of the tachycardia (Table 22.1). The most common mechanisms of SVT and their ECG features are noted in Table 22.2. Evaluation of a tachyarrhythmia usually includes a surface 15‐lead ECG and a continuous rhythm strip to document onset, termination, and response to medications (e.g., adenosine) or pacing maneuvers. Strips obtained from the bedside or transport monitors are helpful for determining tachycardia rate, but they are usually not sufficient for definitive diagnosis or to distinguish among tachycardia mechanisms. In the postoperative patient, an atrial electrogram (AEG) can be useful in both diagnosis and management of rhythm problems. This type of ECG recording is obtained from the temporary atrial wires placed toward the end of surgery (Figure 22.6). Typically, atrial wires emerge on the right side of the chest wall and ventricular wires on the left side, although this configuration may vary. Although both a standard 15‐lead ECG and an AEG record the same electrical cardiac activity, these electrical sequences display distinctly different configurations in different leads. On an AEG, the P waves are larger in amplitude, making them easily recognizable because the recording is obtained from wires attached directly to the atrial myocardium. Therefore, in situations in which P waves are not clearly identified on a surface ECG, an AEG may assist in defining atrial activity and the relationship between atrial and ventricular depolarization (Figure 22.7). Such recordings can help clinicians to differentiate between atrial and junctional arrhythmias [6]. For example, during junctional tachycardia, the AEG displays P waves that are either superimposed on the R waves or dissociated from them. In most reentrant SVTs, the PR interval is longer than the RP interval, whereas in sinus rhythm, the PR interval is shorter than the RP interval. An AEG is also helpful in defining the type of an AV block if present and can facilitate the differential diagnosis of sinus node dysfunction vs. various degrees of AV block. AEGs can be obtained from bedside monitors (Figure 22.6) or standard 15‐lead ECG machines [7]. With a bedside or operating room monitor, it is best to use a rhythm strip with two or more channels so that AEG and ECG recordings can be viewed simultaneously. There are various ways to obtain an AEG along with a standard tracing, depending on various equipment‐related factors (e.g., the recorder, epicardial wires, lead configuration). The following methods of obtaining an AEG require the use of a standard 15‐lead ECG machine: Table 22.1 Characteristics of supraventricular tachycardia mechanisms Table 22.2 Mechanisms and electrocardiographic features of supraventricular tachycardia AV, atrioventricular In addition to assisting in arrhythmia diagnosis and the selection of appropriate treatment, temporary atrial wires can be used for rapid atrial pacing in attempts to terminate SVT due to reentrant mechanisms or to overdrive suppress an automatic focus. Management of SVT depends on the clinical status of the patient, the type of tachycardia, and the precise electrophysiologic mechanism that is causing SVT (Table 22.3). If the tachyarrhythmia is associated with significant hemodynamic compromise, emergent therapy is indicated. Synchronized direct‐current cardioversion (0.5–1.0 J/kg) should be considered for a patient with any acute tachyarrhythmia associated with low cardiac output, recognizing that this approach does not always restore normal sinus rhythm. Table 22.3 Acute therapy of perioperative arrhythmias without evidence of hemodynamic compromise The automaticity of atrial tissue accounts for the majority of supraventricular arrhythmias in this group [8]. In general, these rhythm disorders are more recalcitrant and difficult to treat than reentrant ones. Focal atrial tachycardia (AT) originates from a single focus in the atrium outside of the sinus node. In the past, this rhythm disturbance was thought to be due solely to enhanced automaticity. Thus, it was often referred to as an automatic or ectopic AT (EAT; also known as atrial ectopic tachycardia, or AET). In rare cases, however, focal AT is triggered or microreentrant in origin and is not due to a true ectopic focus. These forms of AT cannot be easily differentiated on the basis of the surface ECG alone. The clinical characteristics of EAT follow those outlined in Table 22.1 for automatic tachycardias. EAT may be incessant or episodic. The diagnosis is made by identifying abnormal P‐wave morphology, axis, or both on a surface ECG or rhythm strip (Figure 22.8). Also, the PR interval may differ from that in sinus rhythm. Atrial rates in EAT are faster than usual sinus rates for the age and physiologic state of the patient. If the atrial rates are very rapid, some of the atrial impulses may not be conducted to the ventricles because of AV node refractoriness. Ectopic AT is relatively rare and is generally found in two different clinical scenarios [9, 10]. A child with a structurally normal heart can develop EAT as a primary phenomenon. In older children, EAT can be incessant and, on rare occasions, lead to the development of ventricular systolic impairment or result in dilated cardiomyopathy due to the chronicity of the tachycardia. In neonates and infants, EAT often follows a more benign course and frequently resolves spontaneously early in life. A patient with CHD can also develop EAT in the postoperative period after cardiac surgery. In such cases, EAT tends to be episodic and transient, usually resolving within days. It has been reported that postoperative patients who developed EAT tended to have a lower preoperative oxyhemoglobin saturation, increased inotropic support both pre‐ and postoperatively, and a previous atrial septostomy [11]. No specific cardiac repair has been associated with the development of EAT. Multifocal atrial tachycardia (MAT), also known as chaotic atrial rhythm, is an uncommon atrial arrhythmia characterized by multiple (at least three) P‐wave morphologies [16]. These different morphologies correspond to multiple foci of automatic atrial activity. Characteristic ECG features include variable PP, RR, and PR intervals and typical atrial rates that exceed 100 bpm. MAT can be seen in young infants without structural heart disease, in postoperative CHD patients, and in children with non‐cardiac medical conditions [17, 18]. Treatment focuses on ventricular rate control or decreasing automaticity, or both. Drugs such as digoxin, procainamide, flecainide, amiodarone, and propafenone have been found to be successful in converting MAT to sinus rhythm in children [19]. Adenosine, pacing, and direct‐current cardioversion are usually ineffective. The automaticity of junctional tissue accounts for the majority of supraventricular arrhythmias in this group [8]. These rhythm disorders tend to be somewhat resistant to standard pharmacological therapy. Accelerated junctional rhythm is an arrhythmia that arises from the AV junction. Characteristics of this automatic rhythm include a narrow or “usual” QRS pattern with no preceding P wave. There is either VA dissociation, with ventricular rates faster than atrial rates, or the presence of 1 : 1 VA conduction retrograde via the AV node. Temporary atrial pacing at a rate of 10–20 bpm faster than the junctional rate often re‐establishes AV synchrony and effectively suppresses the automatic junctional rhythm. Changes in the patient’s physiologic state (including fever), chronotropic agents, and endogenous catecholamines can stimulate the automatic junctional focus, increasing junctional rates. This rhythm is usually well‐tolerated and is easily managed with temporary pacing and control of the patient’s underlying physiologic state. Junctional ectopic tachycardia (JET) is another automatic rhythm that arises from the AV junction. It is a narrow or “usual” complex tachycardia without preceding P waves. It is distinguishable from accelerated junctional rhythm on the basis of the patient’s heart rate and hemodynamic status. This tachyarrhythmia has been classically defined by heart rates above 160 or 170 bpm with resultant hemodynamic compromise [20]. The diagnosis of JET has also been considered if the junctional rate exceeds the 95th percentile of heart rate for age [21]. There is either VA dissociation with ventricular rates faster than atrial rates or the presence of 1:1 VA conduction (Figure 22.9). If 1:1 VA conduction is identified, a trial of adenosine or rapid atrial pacing may be beneficial to differentiate JET from other reentrant forms of SVT on an AEG. This type of tachycardia typically occurs in the immediate postoperative period and usually results in hemodynamic instability and significant morbidity and may contribute to mortality [22–24]. It occurs most commonly after surgical intervention for tetralogy of Fallot, VSD, AVSD, transposition of the great arteries, and total anomalous pulmonary venous return [25]. Other risk factors for the development of JET are long ischemic cross‐clamp and cardiopulmonary bypass times, young age, and the need for inotropic support [26, 27]. Excessive retraction of tissues to allow for intracardiac surgical exposure anecdotally has also been linked to JET. Several strategies have been used to decrease the incidence of postoperative JET. The administration of magnesium during cardiopulmonary bypass decreases the incidence of postoperative JET, its use appears to be more effective in higher complexity surgeries [28, 29]. Another strategy that has shown promise in the reduction of postoperative JET is the use of dexmedetomidine in the perioperative period [30, 31]. Numerous therapies have been advocated for JET [23, 24, 26, 32]. Strategies for acute care include the following: Reentry, also known as “circus” movement or reciprocation, implies that a single stimulus or excitation wave front returns and reactivates the same site or tissue from which it originated. Reentrant forms of SVT may or may not involve accessory pathways. Atrial flutter is a rhythm disturbance confined to the atrial myocardium. The electrophysiologic basis for this arrhythmia involves reentry within the atrium itself. The typical or classic form of atrial flutter is characterized by a negative sawtooth P‐wave pattern and atrial rates that exceed 300 bpm (Figure 22.10). This form of atrial flutter is occasionally seen in otherwise healthy neonates but is relatively uncommon in children. In patients with CHD, slower atrial rates and varying P‐wave morphologies are more frequently seen than in those without CHD. This is due to anatomic abnormalities related to suture lines, scars, or fibrosis from a previous surgery involving atrial tissue. This form of “scar flutter” is commonly termed intra‐atrial reentrant tachycardia (IART) [49]. It is one of the most common arrhythmias in postoperative patients with structural heart disease and is considered the cause of significant morbidity after certain types of surgical interventions [50]. Procedures that involve extensive atrial suture lines, such as atrial redirection procedures (Senning or Mustard operations) and those associated with atrial dilation (Fontan surgery) pose a particularly high risk of atrial flutter. The possibility of atrial flutter is suggested by the abrupt onset of a rapid atrial rhythm that remains relatively regular over time. AV nodal conduction accounts for variability in the ventricular response rate. Rapid clinical deterioration is likely; fast ventricular rates frequently require prompt intervention. Atrial fibrillation is a complex arrhythmia that can be due to either multiple reentrant circuits or focal points within the pulmonary veins. In the majority of cases, it originates in the left atrium (in contrast to atrial flutter, which is generally considered a disease of the right atrium). In children, this tachyarrhythmia is less frequent than atrial flutter. The atrial rates are rapid and irregular, ranging from 400 to 700 bpm. Ventricular response rates are variable but generally range between 80 and 150 bpm. Patients at potential risk for atrial fibrillation include those with an enlarged left atrium (e.g., rheumatic heart disease, severe AV valve regurgitation), pre‐excitation syndromes, structural heart disease (Ebstein anomaly, tricuspid atresia, ASDs), and cardiomyopathies. Atrioventricular reentrant tachycardia (AVRT) is the most common type of SVT in infancy and childhood. It is mediated by an accessory pathway between the atrium and ventricle. The tachycardia circuit typically consists of conduction from the atrium, down the AV node, through the bundle of His and ventricles, and then up the accessory connection back to the atrium. This form of SVT is referred to as orthodromic SVT and occurs in patients with Wolff–Parkinson–White syndrome (WPW; Figure 22.11), concealed accessory pathways, and permanent junctional reciprocating tachycardia. In contrast, in antidromic SVT, conduction travels from the atrium, down the accessory connection, through the ventricles, up the AV node, and back to the atrium. The QRS complex in this form of SVT is wide. Antidromic tachycardia can occur in patients with WPW and other pre‐excitation variants (Mahaim tachycardia). Atrioventricular nodal reentrant tachycardia (AVNRT), or reentry within the AV node, is most likely in adolescents or young adults. In AVNRT, the AV node has two physiologically distinct components, designated the “slow” and “fast” AV nodal pathways. The typical form of AVNRT consists of antegrade conduction (from the atrium to the ventricle) via the slow pathway, followed by retrograde conduction (back to the atrium) via the fast pathway. Both AVRT and AVNRT have clinical characteristics typical of reentrant tachycardia mechanisms as listed in Table 22.1. The two can often be distinguished by closely evaluating the surface ECG during sinus rhythm and tachycardia. In orthodromic AVRT, the P wave can be seen immediately after the QRS complex or in the ST segment or T wave (Figure 22.12). The reason for this P‐wave location is that a set time is necessary for conduction to proceed from the ventricles through the accessory pathway back to the atrium. In contrast, in AVNRT, the P wave is buried in the QRS complex and is often not discernible (Figure 22.13). This is the case because the tachycardia circuit is within the AV node, and the atria and the ventricles are activated almost simultaneously. Patients with structurally normal hearts, as well as those with CHD, can have either AVRT or AVNRT. Ebstein malformation of the tricuspid valve is frequently associated with AVRT secondary to one or multiple accessory pathways. The accessory connections in this condition are usually right‐sided. Congenitally corrected transposition can be associated with an Ebstenoid left‐sided AV valve, and left‐sided accessory pathways can be identified in a subset of patients.
CHAPTER 22
Arrhythmias: Diagnosis and Management
Introduction
Cardiac rhythm disturbances
Sinus bradycardia
Low atrial rhythm
Sinus node dysfunction
Sinus tachycardia
Junctional rhythm
Conduction disorders
Bundle branch block
Atrioventricular block
First‐degree AV block
Second‐degree AV block
Third‐degree (complete) AV block
Supraventricular arrhythmias
Premature atrial contractions
Supraventricular tachycardia
Atrial electrogram
Features of the tachycardia
Automatic
Reentrant
Onset and termination
“Warm‐up” at initiation, “cool‐down” at termination
Abrupt
Mode of initiation
Spontaneous
Premature beats
Ability to initiate/terminate with timed premature beats
No
Yes
Variation in tachycardia rate
Wide
Narrow
Response to catecholamines
Increased rate
None or slight rate increase
Response to adenosine
None
Termination
Response to drugs that increase refractoriness
Variable
Slowing or termination
Response to overdrive pacing
Transient suppression, quick resumption
Termination
Response to cardioversion
None
Termination
Diagnosis
Electrocardiographic features
Automatic tachycardias
Ectopic atrial tachycardia or atrial ectopic tachycardia
Atrial rates of 90–330 bpm
Incessant rhythm
From atrial focus distinct from the sinus node
Abnormal P‐wave morphology and/or axis
Distinct P waves preceding QRS complexes
No influence of AV block on tachycardia
Junctional ectopic tachycardia
Narrow QRS tachycardia
Incessant rhythm
AV dissociation (often)
Atrial rate slower than the ventricular rate
Capture beats frequently seen (QRS complexes slightly earlier than expected from antegrade conduction of normal sinus impulses)
Reentrant tachycardias
Atrial flutter
Sawtooth pattern or more discrete undulating P waves (leads II, II, aVF)
Variable rates of AV conduction seen (1:1, 2:1, 3:1, or 4:1)
Atrioventricular reentrant tachycardia (accessory pathway‐mediated from concealed bypass tract or Wolff‐Parkinson‐White syndrome)
P waves immediately following the QRS complex, on ST segment or T wave
AV block results in termination of tachycardia
Atrioventricular nodal reentry tachycardia
P waves buried within QRS and not discernible
AV block results in termination of tachycardia
General management principles for SVT
Rhythm disturbance
Treatment considerations
Sinus bradycardia
See Box 22.1
Sinus tachycardia
Correct underlying cause
Premature atrial contractions
Evaluate the position of a central venous line or intracardiac catheter Assess/correct electrolyte disturbances (e.g., hypokalemia)
Focal (ectopic) atrial tachycardia or atrial ectopic tachycardia
Correct fever, electrolyte abnormalities
Adequate sedation
Consider the potential detrimental role of inotropes/vagolytics
ß‐blockers – use with caution if depressed cardiac function
Digoxin
Procainamide
Amiodarone
Sotalol
Flecainide
Propafenone
Ivabradine
Multifocal (chaotic) atrial tachycardia
As in ectopic atrial tachycardia
Goals are rate control and decreased automaticity
Accelerated junctional rhythm
Correct fever
Consider the potential detrimental role of inotropes/vagolytics
Temporary atrial pacing
Junctional ectopic tachycardia
Correct fever and electrolyte abnormalities
Consider the potential detrimental role of drugs (e.g., inotropes)
Adequate sedation (dexmedetomidine)
Surface cooling to 34–35 °C
Temporary atrial pacing (for JET rates <180 bpm)
Amiodarone
Hypothermia plus procainamide
Sotalol
Ivabradine
Atrial flutter
Adenosine to confirm the diagnosis
Atrial overdrive pacing
Digoxin
Procainamide
Amiodarone
Sotalol
Propafenone
Atrial fibrillation
Digoxin (except in Wolff–Parkinson–White syndrome)
ß‐blockers
Procainamide
Quinidine
Amiodarone
Sotalol
Atrioventricular reentrant tachycardia or atrioventricular nodal reentrant tachycardia
Consider vagal maneuvers
Adenosine
Atrial overdrive pacing
Procainamide
Amiodarone
Sotalol
Premature ventricular contractions
Identify and treat underlying cause
Lidocaine
Ventricular tachycardia
Lidocaine
Amiodarone
Procainamide
Sotalol
Magnesium (for torsades de pointes)
ß‐blockers
Phenytoin (for digitalis toxicity)
Ventricular fibrillation
Lidocaine (adjunct to defibrillation/prevent recurrence)
Amiodarone (adjunct to defibrillation/prevent recurrence)
Atrial tachycardias
Focal atrial tachycardia
Management principles for postoperative EAT
Multifocal atrial tachycardia
Junctional tachycardias
Accelerated junctional rhythm
Junctional ectopic tachycardia
Management principles for postoperative JET
Reentrant supraventricular tachycardias
Atrial flutter
Management principles for atrial flutter
Atrial fibrillation
Management principles for atrial fibrillation
Atrioventricular reentrant tachycardia and atrioventricular nodal reentrant tachycardia
Management principles for AVRT or AVNRT