Atrial Premature Beats, July 30, 1986

Atrial Premature Beats, July 30, 1986

1. There is an ectopic atrial P wave that appears prematurely, and its morphology differs from that of a normal P wave. Sometimes the atrial P wave appears so early that it overlaps with the preceding T wave, in which case identification relies on the deformation of the T wave.

2. The PR interval may sometimes exceed 0.20 seconds.

3. In V1 lead, the QRS complex of premature beats often shows an rSR pattern, and the atrial P wave can usually be found before the QRS complex. Although the PR interval is longer than 0.12 seconds, the compensatory pause is often incomplete, which can be used to differentiate it from ventricular premature beats (a complete compensatory pause means that the sum of the short pause before the premature beat and the long pause after it equals twice the normal pause). If the P wave appears even earlier, within the absolute refractory period of the atrioventricular node, there will be no corresponding QRS complex, which is called a blocked atrial P wave. If the premature beat occurs during the relative refractory period, the QRS complex will show intraventricular differences, and here it is important to clarify a concept—the coupling interval. The coupling interval refers to the distance between the premature beat and the underlying basic rhythm. If the coupling intervals of all premature beats are equal, it indicates that the premature beats are monogenic; if the coupling intervals are unequal, it indicates that they are polygenic.