Arrhythmias

Abstract

The morphology of an atrial premature P wave is different from that of the sinus P wave (Fig. 11-1). The premature P wave is usually followed by a QRS complex similar to that with the normally conducted sinus beat. The premature P wave may be unrecognizable because it is hidden in the preceding T wave, hence the admonition “search the T for the P” (Figs. 11-2 and 11-3). The PR interval of an atrial premature beat (APB) is more than 0.11 second; if the P wave is inverted in leads II, III, and aVF, the PR should be more than 0.11 second to distinguish an APB from a junctional premature beat. Early occurring APBs may trigger atrial tachycardia (see Fig. 11-2), atrial fl utter, or atrial fi brillation. APBs that follow every sinus beat cause atrial bigeminy (see Fig. 11-1). The atrial premature P wave may not be conducted, resulting in a pause (see Fig. 11-3).