Effect of atrial capture beats on the subsequent cycle during slow common atrioventricular nodal reentry tachycardia

摘要

A 60-year-old patient affected by arterial hypertension undergoes a 24-hour Holter ECG monitoring for palpitations. The Holter analysis shows numerous episodes of regular paroxysmal supraventricular tachycardia (SVT) with ventricular rates included between 113 and 148 bpm.Figure 1 shows the effects of an atrial capture beat on the tachycardia: in Figure 1(A) it stops the subsequent tachycardia beat and in Figure 1(B) it causes a delay of the following beat without terminating the tachycardia. What is the mechanism?