If no P waves can be seen and the QRS complexes are irregularly irregular, then atrial fibrillation is present. ... not elevation in leads V1 and V2 with an R:S ratio greater that 1 in lead V1.

The morphology of the P wave will not be similar to the sinus P wave, which is normally upright in lead II and biphasic in lead V1. Often, the P wave is inverted in lead II, if it can be seen at all.

The diagnosis is sinus tachycardia, right ventricular pacemaker, P-wave synchronous ventricular pacing (A-sensed V-paced), pseudo second-degree AV block due to failure of atrial sensing. There is ...

In the cohort of 15,321 patients, 2273 patients presented with prolonged P-wave duration at the study start, 2406 patients developed prolonged P-waves during study follow-up, and 268 SCDs were ...

Surface ECGs show a P wave preceding each QRS complex, although at rapid heart rates, the P wave may be obscured by the T wave. The remaining supraventricular tachycardias are much less common.