April 16th Question
A 60-year-old man with prior multiple endocardial catheter ablation procedures for atrial fibrillation and atrial flutters including pulmonary vein isolation, left atrial roof line, and lateral mitral isthmus line was brought to the electrophysiology laboratory for recurrent left atrial flutter. The left pulmonary veins were found to be isolated, but the right pulmonary veins were reconnected. The clinical atrial flutter was inducible, and its left atrial electroanatomic point-by-point activation map is shown in Figure 1 in the left anterior oblique and right anterior oblique views. Entrainment from the left atrial posterior wall and left atrial roof in between the left and right superior pulmonary veins shows demonstrably longer postpacing intervals than tachycardia cycle length. Entrainment maneuvers from the endocardial lateral mitral isthmus (3-o’clock mitral isthmus) and from the proximal coronary sinus electrodes (approximately at 6:30 mitral annulus) are shown in Figure 2. Which of the following statements is the most appropriate next step?
A. Epicardial connection using the coronary sinus should be evaluated for participation in a clockwise perimitral atrial flutter.
B. Mapping/ablation catheter should be retracted from the left atrium to the right atrium to perform entrainment from the cavotricuspid isthmus.
C. The early-meets-late stripe from the mitral annulus to the right-sided wide area circumferential ablation along the interatrial septum should be ablated.
D. This is a focal microreentrant atrial tachycardia and ablation targeting early electrograms in the red region should be performed.
E. Ablation should be performed at coronary sinus (CS) 9,10 at the site of entrainment in Figure 2B.
Answer to April 9th Question
D. Left atrial posterior wall
The intracardiac electrograms from April 9th Question show the activation for the premature atrial complex being similarly early at proximal His catheter, coronary sinus 5,6 and 7,8, as well as the circular mapping catheter in the left atrial appendage (see asterisks in Figure 1). In a focal arrhythmia, depolarization starts at a single site in the heart from where the wavefront propagates radially outwards to activate the entire cardiac chamber(s). When there are multiple equally early but spatially separate sites mapped, none of them could be the site of origin, as this would obligate the other sites to be activated with some delay. The intracardiac catheters are not mapping the entirety of the atrial chambers, and there must be a singular early site of origin that is not being recorded from which the electric propagation takes a similar time to reach the regions marked with asterisks in Figure 1. In other words, the site of origin needs to be triangulated to a region somewhat equidistant from all 3 relatively similar early sites being mapped.
Triangle of Koch (Option B) and noncoronary aortic sinus of Valsalva (Option C) being in anatomic proximity to the His catheter, and the left atrial appendage (Option E) are therefore wrong answers. Option A (crista terminalis) is wrong because radial spread from such a right atrial site would have resulted in early activation of the right atrial electrograms, which are clearly very late. The left atrial posterior wall (Option D) is the correct answer as this would be spatially equally distant from all the asterisked sites in Figure 1. The earliest site was mapped to the left atrial posterior wall, 55 ms before the asterisked sites as shown in Figure 2 (arrowhead). Focal ablation at this site eliminated the premature atrial complexes.
- © 2018 American Heart Association, Inc.