Stokes–Adams Syncope and Ventricular Standstill

FIGURE 1. Baseline electrocardiogram. ECG with sinus tachycardia, incomplete right bundle branch block (QRS 118 ms), normal axis (approximately 45°), and first‐degree AV block (PR interval 209 ms). No other conduction abnormalities are identified.

FIGURE 2. (A) 12‐lead ECG demonstrating atrial tachycardia with 2:1 AV block during 3 beats, followed by a ventricular standstill. (B) Zoomed‐in rhythm strip highlighting the P–P intervals (red arrows) and P waves (green arrows) buried in the T waves. The P wave axis is unusual, as there is no distinct P wave in Lead I, with a clear P wave leads II (upright) and V1 (negative). The lack of an upright P wave in Lead I in this regular tachycardia (P–P interval 480 ms, atrial rate 125 bpm) favors an ectopic rhythm over sinus rhythm.

FIGURE 3. ECG with upper rate tracking behavior. Note the difference in P wave morphology in leads I and V1 in this ECG compared to the baseline ECG (Figure 1). Whereas the baseline P wave in V1 is biphasic, it is negative in this atrial tachycardia. There is no clear P wave in lead I in comparison to the baseline ECG. These suggest an ectopic focus near the crista terminalis.