Naomi J. Kertesz, MD
The patient is a 38-year-old woman with the diagnosis of transposition of the great arteries. She underwent an atrial switch operation at 2 years of age (Figure 16-1). Her first episode of atrial flutter occurred at 11 years of age. She required multiple medications and ultimately underwent pacemaker implantation due to bradycardia secondary to antiarrhythmic management. She continued to have recurrent flutter requiring multiple cardioversions. She underwent an EP study with attempted ablation at 26 years of age. Multiple circuits were found, and the procedure was unsuccessful. She recently had an episode of atrial flutter while taking sotalol 120 mg BID and metoprolol 12.5 mg daily. She was walking up stairs and noted the onset of flutter (Figure 16-2). She became dizzy and could not make it up the stairs. Her ventricular response was greater than 200 bpm. She underwent cardioversion, and her metoprolol was increased to 25 mg daily. She did not tolerate the increased dose, and she was referred to for repeat attempt at ablation.
FIGURE 16-1 MRI of transposition of the great arteries following atrial switch operation. Note the baffling of the superior vena cava (SVC) and inferior vena cava (IVC) towards the mitral valve and left ventricle (LV). There is no access to the tricuspid valve from the systemic venous side or the IVC.
FIGURE 16-2 The patient’s clinical atrial flutter.
As is all too common in this population two separate arrhythmias were induced: an atrial tachycardia that had not been seen clinically (Figure 16-3) and atrial flutter (Figures 16-4 and 16-5). Mapping was initially performed on the systemic venous side, and the atrial tachycardia location was identified and ablated. In order to map the atrial flutter, a transbaffle puncture was performed to access the tricuspid valve and the pulmonary venous side (Figure 16-6). Entrainment mapping was used to identify the circuit (see Figure 16-5). The atrial flutter was successfully ablated (Figure 16-7) by placing lesions from the IVC to the baffle on the systemic venous side and then from the baffle to the tricuspid valve on the pulmonary venous side (Figure 16-8). She has had no recurrence of her atrial flutter.
FIGURE 16-3 Atrial tachycardia induced in the EP laboratory.
FIGURE 16-4 Atrioventricular block was induced during catheter manipulation, which makes the flutter waves easier to identify.
FIGURE 16-5 Entrainment mapping used to define flutter circuit.
FIGURE 16-6 Carto map of the systemic venous baffle. Note the site of successful atrial tachycardia ablation. The ablation catheter is on the pulmonary venous side of the baffle.
FIGURE 16-7 Atrial flutter terminated with radiofrequency ablation.
FIGURE 16-8 Both systemic and venous baffles are outlined. In order to completely ablate the flutter isthmus it was necessary to cross the baffle and ablate from the IVC to the tricuspid valve.
• Over one million adult congenital heart disease (CHD) patients are living in the United States.1
• Forty-five percent have simple defects (atrial septal defect, ventricular septal defect, valve stenosis).
• Forty percent have moderately complex heart disease (tetralogy of Fallot).
• Fifteen percent have severely complex deflects (single ventricle anatomy, Fontan palliation, atrial switch procedure for transposition of the great arteries).
• Any patient who has had an atriotomy incision is at risk for supraventricular arrhythmias.
• Thirty-four percent of older patients with TOF develop symptomatic supraventricular arrhythmias.2
• Older style Fontans, that is, atriopulmonary, have up to a 50% incidence of atrial arrhythmias due to atrial dilation and suture lines.3
DIAGNOSIS AND MANAGEMENT
Atrioventricular Reentry and Twin AV Nodes
The embryological abnormalities that cause congenital heart defects may also have a direct impact on the conduction system. The AV node and the His bundle may only be displaced, or there may be accessory or duplicated AV connections with the possibility of reentrant arrhythmias.
• Common in some types of congenital heart disease.
• Ebstein anomaly (Figure 16-9) is associated with Wolf-Parkinson-White syndrome in 20% of cases. Nearly half of these patients will have multiple accessory pathways.
FIGURE 16-9 MRI of Ebstein anomaly of the tricuspid valve. Note the diminutive right ventricle, the displaced tricuspid valve, and the large right atrium.
• Patients with L-TGA, that is, corrected transposition, also have a high incidence of accessory pathways; many of these patients also have Ebstein anomaly of their left-sided tricuspid valve.
• Given the atrial dilation in these patients the risk of atrial fibrillation with rapid conduction is becoming increasingly problematic in adolescence and adulthood (Figure 16-10).
FIGURE 16-10 (A) Baseline ECG in an adult with Ebstein anomaly and WPW. (B) Atrial fibrillation in a 20-year-old woman with Ebstein anomaly and WPW.
• Catheter ablation is considered the standard of care for management of accessory pathways.
• It should be recognized that long-term recurrence is higher in patients with Ebstein anomaly. These ablations are complicated by distorted landmarks, difficulty in identifying the true AV groove, and the high incidence of multiple pathways.4
Twin AV Nodes
• This is a rarer anomaly typically seen in single ventricles of the heterotaxy variety.
• There are two AV nodes with 2 discrete His bundles with evidence of a connecting fiber.5
• Treatment is focused on ablation of one of the limbs of the duplicate system.
INTRA-ATRIAL REENTRANT TACHYCARDIA (IART)
• Most common mechanism of symptomatic arrhythmia in the adult CHD patient.
• IART or incisional tachycardia are customary labels to distinguish this arrhythmia from typical atrial flutter (Figures 16-11 and 16-12). It is a macroreentrant circuit within atrial muscle caused by atrial dilation, thickening, and scarring.
FIGURE 16-11 Atrial flutter in an adult with unrepaired single ventricle.
FIGURE 16-12 Nineteen-year-old with Fontan who presented with palpitations. Adenosine administration (A and B) makes classic flutter waves easily seen, which was unexpected given the type of heart disease and baseline ECG (C).
• Other risk factors for IART include concomitant sinus node dysfunction with tachy-brady syndrome and older age at the time of surgery.3
• IART is seen in 30% of patients following an atrial switch operation (Mustard or Senning) (see Figure 16-3); or 50% of patients following a Fontan palliation (Figure 16-13) though IART can occur in any patient who has undergone an atriotomy incision.
FIGURE 16-13 Lateral tunnel Fontan. Note the SVC and IVC directly connected to the pulmonary arteries (PA).
• The route of propagation varies depending on the anatomic defect and the surgical repair and is modulated by fibrosis of suture lines or patches.
• It is common to have multiple circuits in one patient. When a tricuspid valve is present the cavotricuspid isthmus is often part of the circuit.
• The IART rate is generally slower than classic flutter with atrial rates of 150 to 250 bpm. The P waves are small and separated by a flat baseline and are masked by the QRS and T waves (Figures 16-14 and 16-15). There may be 1:1 or variable AV conduction.
FIGURE 16-14 Thirty-year-old with history of Mustard operation who presented with complaints of tachycardia. She was originally discharged from the ER until ECG reviewed by cardiology. The ECG demonstrates IART with 2:1 AV conduction. Note short PR and P wave buried in T wave.
FIGURE 16-15 Twenty-six-year-old status post-Senning operation with AAIR pacemaker due to sinus node dysfunction. He presented to ER with palpitations. Pacemaker interogration demonstrated that this was IART with 2:1 AV conduction. P waves virtually unable to be seen.
• One must have high index of suspicion in older CHD patients, as the P waves are so difficult to see. Adenosine may be useful to unmask the arrhythmia (see Figure 16-12).
• IART can lead to hemodynamic instability, including cardiac arrest, or in the subacute setting cause heart failure and thromboembolic phenomena.
• IART can be reliably terminated with electrical cardioversion and sometimes with overdrive pacing.
• Many patients with underlying sinus node dysfunction may be significantly bradycardic following cardioversion.
• Consideration should be given to placing cardioversion pads over sternum and back to have the vector of energy travel through the atrium to increase the success rate.
• Patients have a high incidence of thrombus formation and need anticoagulation.
• Long-term therapeutic options include antiarrhythmic drugs, pacemakers, catheter ablation, and surgical intervention.
• Pacemakers are useful for treating tachy-brady syndrome, allowing use of antiarrhythmics in patients with underlying sinus node dysfunction, and antitachycardia pacing. One must be careful with antitachycardia pacing as this may cause a shift to a different and faster IART circuit or cause degeneration into atrial fibrillation.
• Catheter ablation using 3-D mapping and irrigated-tip or large-tip catheters has a short term success rate of nearly 90%.6,7 It is important to remember that in patients with atrial switch procedures the cavotricuspid annulus is in the pulmonary venous atrium and only accessible prograde via transbaffle puncture.
• Recurrence risk is particularly high—nearly 40% in Fontan patients due to the large number of IART circuits and the thickness and size of the atrium. However, ablation still may be useful as it may reduce the frequency of episodes or make drug therapy more effective.4
• Surgical ablation is an option and consists of a right atrial maze procedure particularly in the Fontan population. Many times this is combined with a revision of the Fontan connection from an older atriopulmonary anastomosis to a cavopulmonary anastomosis or extracardiac Fontan.
• Atrial fibrillation arises in response to hemodynamic stress in the left atrium (Figure 16-16) and is most commonly associated with aortic stenosis, mitral valve deformities, and unrepaired single ventricles.
FIGURE 16-16 (A and B) Surface ECG and rhythm strip of patient with dual chamber pacemaker and atrial fibrillation. (C) Rhythm strip with atrial wires hooked up to right and left arm; ECG leads therefore displaying on lead I.
• Patients with isolated right-sided heart lesions are at a higher risk of developing atrial arrhythmias than those with isolated left heart lesions. The 30-year risk of developing atrial arrhythmias in an 18-year-old patient with right-sided heart disease (ASD, Ebstein anomaly, Fontan, tricuspid valve abnormality) is 18% in comparison to 11% in one with left-sided disease (VSD, aortic, or mitral valve disease).8
• Issues regarding hemodynamic instability, heart failure, and stroke are seen in this population just as in those patients with structurally normal hearts. There is no difference in morbidity or mortality between those with right- or left-sided heart lesions.
• Management is similar to atrial fibrillation in adults without CHD and consists of cardioversion, antiarrhythmics for rate control, and anticoagulation.
• Antiarrhythmic therapy is only marginally successful.
• Pacemaker insertion may reduce recurrence in those with sinus node dysfunction.
• Surgical ablation with a right- and left-sided maze is possible.
• Catheter ablation with pulmonary vein isolation has been reported in the presence of congenital heart disease with the most common defect being an ASD. However, pulmonary vein isolation has also been reported in patients, status post-Fontan operation.9
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7. Jais P, Shah DC, Haissaguerre M, et al. Prospective randomized comparison of irrigated-tip versus conventional-tip catheters for ablation of common flutter. Circulation. 2000;101:772-776.
8. Vernier M, Marelli AJ, Pilote L, et al. Atrial arrhythmias in adult patients with right versus left sided congenital heart disease anomalies. Am J Cardiol. 2010;106(4):547-551.
9. Philip F, Muhammad KI, Agarwal S, et al. Pulmonary vein isolation for the treatment of drug-refractory atrial fibrillation in adults with congenital heart disease. Congenit Heart Dis. 2012;7:392-399.