Second degree AV block

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There is a limitation in interpreting the rhythm as a long rhythm strip is not available. This is often the situation when the ECG is obtained without your supervision. The PR interval of the first beat is quite prolonged so that it overlaps with the T wave of the previous beat. The next P wave is superimposed on the T wave as well as non conducted, resulting in a pause. The PR interval of the second beat is less prolonged as the conduction recovers partially following the blocked beat and the pause. The next PR interval is again prolonged. So overall the ECG shows a 3:2 type I AV block. QRS complex is narrow, indicating a supra Hisean location of the block. These features fit in with the Wenckebach phenomenon.