KG is a 38-year-old woman with the diagnosis of transposition of the great arteries (TGA). She underwent an atrial switch operation at age 2 (Figure 13-1). Her first episode of atrial flutter occurred at age 11 and was refractory to antiarrhythmic drug therapy with multiple cardioversions and ultimately required permanent pacemaker implant to support drug therapy. A prior electrophysiologic (EP) study and radiofrequency ablation (RFA) was unsuccessful. She recently had an episode of atrial flutter while taking sotalol 120 mg bid and metoprolol 12.5 mg daily. Her symptoms abruptly began with exertion and including dizziness and dyspnea associated with ventricular rates greater than 200 bpm (Figure 13-2). She underwent cardioversion and beta-blocker dose titration but unfortunately could not tolerate higher beta-blockade. She was subsequently referred for repeat EP study. Two separate arrhythmias were induced, an atrial tachycardia that had not been seen clinically (Figure 13-3) and atrial flutter (Figures 13-4 and 13-5). 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 13-6). Entrainment mapping was used to identify the circuit (Figure 13-5). The atrial flutter was successfully ablated (Figure 13-7) by placing lesions from the inferior vena cava (IVC) to the baffle on the systemic venous side and then from the baffle to the tricuspid valve on the pulmonary venous side (Figure 13-8). She has since had no recurrence of her atrial flutter.
FIGURE 13-3
Atrial tachycardia induced in the electrophysiology laboratory with a cycle length of 300 ms. From top to bottom surface leads I, III, and aVF; ablation distal and proximal, left atrial appendage distal and proximal, 10 pole coronary sinus catheter distal (1, 2) to proximal (9, 10). 10 pole halo catheter proximal (9, 10) to distal (1, 2) and the right ventricular proximal and distal electrograms.
FIGURE 13-7
Atrial flutter terminated with radiofrequency ablation. From top to bottom surface leads I, III, and aVF; ablation distal and proximal, left atrial appendage distal and proximal, 10 pole coronary sinus catheter distal (1, 2) to proximal (9, 10). 10 pole halo catheter proximal (9, 10) to distal (1, 2) and the right ventricular proximal and distal electrograms.
Over 1 million adult congenital heart disease (CHD) patients are living in the United States.1
About 45% have simple defects (eg, atrial septal defect [ASD], ventricular septal defect [VSD], valve stenosis).
About 40% have moderately complex heart disease (eg, tetralogy of Fallot [TOF]).
About 15% have severely complex defects (eg, single ventricle anatomy, Fontan, atrial switch procedure for transposition of the great arteries).
This case highlights that arrhythmogenic complications increase as patients with CHD get older. These arrhythmias are often the leading cause of hospitalization and morbidity in adults with congenital heart disease.2
Cardiovascular anatomy predicts the location of conduction system disease.
Broadly, arrhythmias should be considered as the following:
Supraventricular including bradyarrhythmias
Ventricular arrhythmias that pose a risk of sudden death
About 34% of older patients with TOF develop symptomatic supraventricular arrhythmias.3
Older style atriopulmonary Fontans, have up to a 50% incidence of atrial arrhythmias due to atrial dilation and suture lines.4
Bradyarrhythmias occur as a result of sinoatrial node dysfunction, delays in intra-atrial conduction, dysfunction of the atrioventricular (AV) node, or disease of the His-Purkinje fibers.3, 5
Cardiovascular anatomy and the surgical repair predict the location of conduction system disease.
Arrhythmias are dependent on the surgical approach with ventricular arrhythmias predominating in older repairs via ventriculotomy and atrial arrhythmias dominant in newer transatrial or transpulmonary approaches.
About 4% to 8% of patients present with bradycardia.6
Complete AV block occurs in 22% of patients, largely in the infrahisian fibers.7
Following Mustard or Senning repairs bradycardia is mediated by direct iatrogenic injury to the sinus or AV node or interruption of blood flow to the sinus node during surgery.8
Arrhythmias are dependent on the surgical approach.9
Atriopulmonary level conduits result in 30% to 40% of patients with sinus node dysfunction and 11% to 18% requiring pacemaker therapy.
Extracardiac Fontan patients have 7% to 23% incidence of sinus node dysfunction with 3% to 7% requiring pacemakers.
Lateral tunnel conduits result in 3% to 25% of patients with sinus node dysfunction and 5% to 10% of patients needing pacemaker therapy.
Sinus node anatomy in most patients with adult congenital heart disease is consistent with the normal adult and is located in the high right atrium lateral to the superior cavoatrial junction.10
P-wave axis is 20 to 75 degrees.
AV nodal and QRS features are based on anatomy and highly variable depending on the type of congenital anomoly.11
Rightward axis with right bundle branch block is almost universal.
Left anterior fascicular block is seen in 10% of patients.
Mobitz type II or III AV block with a stable narrow complex junctional QRS.
Third-degree AV block is common in patients with simultaneous VSD repair.
Highly variable electrocardiography (ECG) but universal prolongation in the PR interval.
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