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.
Magnetic resonance imaging (MRI) of transposition of the great arteries following atrial switch operation. There is no access to the tricuspid valve from the systemic venous side or the IVC.
A 12-lead ECG showing clinical atrial flutter.
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.
Atrioventricular block during catheter manipulation which makes the flutter waves easier to identify.
Entrainment mapping used to define flutter circuit. The post pacing interval (PPI) is 370 ms with a tachycardia cycle length (TCL) of 360 ms. The PPI-TCL of 10 ms suggests that the pacing catheter is within the tachycardia circuit.