Atrioventricular Block: Does This Patient Require a Pacemaker?
A 71-year-old woman was admitted due to intermittent palpitations and occasional episodes of mild dizziness, particularly noticeable on assuming a standing position during the past month. The ECG recorded in the emergency room is depicted in Figure 1. These observed sequences were repetitive for long periods during ECG monitoring. The patient’s cardiovascular history and physical examination yielded no noteworthy findings. The echocardiogram did not reveal any significant structural abnormalities. Does this patient need a pacemaker?
The ECG shows repetitive sequences of sinus beats with interpolated monomorphic premature ventricular complexes (PVCs). These premature depolarizations had a constant coupling interval (460 ms), a left bundle-branch block pattern in V1 with a markedly delayed transition in precordial leads, and a frontal QRS axis of –30º. After each PVC, the PR interval becomes progressively prolonged until a P wave is blocked (Figures 1 and 2). This case exemplifies a “typical” Wenckebach sequence induced by concealed repetitive conduction of interpolated PVCs. Their retrograde hidden influence into the atrioventricular (A-V) node progressively increases its refractoriness to A-V conduction, leading to a gradual prolongation of succeeding conduction intervals with decreasing increments. The development of such a typical Wenckebach periodicity is relatively uncommon in routine clinical practice.
