Sinoatrial node reentrant tachycardia triggered by a premature atrial contraction

Rhythm strip recording leads I, II, II, and V1 at 25 mm/sec and demonstrating a PAC initiating SANRT. The PR interval (PR) is longer during tachycardia than it is during sinus rhythm. This results in the P wave merging into the previous T wave (P on T). The P wave morphology during sinus rhythm is very similar to that during tachycardia. The heart rate during sinus rhythm is 86 bpm, and the PR interval is 0.14 seconds. During SANRT, the rate is 145 bpm and the PR interval is 0.20 seconds.