Long Latency

Report:

Sinus rhythm

Latent (first degree) AV block

PR 0.90”

Left anterior hemiblock

Right bundle branch block

Old anterior infarction

Comment:

This is the longest sustained first degree AV block I have seen. It is possible that the rhythm is other than sinus - the P waves are rather small - or that the sinus impulses are not conducted, being merely ‘linked’ to a prevailing junctional or idioventricular rhythm. They could also, conceivably, be retrograde upright91 P waves. Finally, initial portion of the P waves may be masked by the terminal portion of the T waves.

It is known that the rhythm was not idioventricular, since atrial pacing produced the same QRS morphology later (strip below), but at a spike-QRS interval less than half as long. At other times the patient was in AF; the striking original ECG is, unfortunately, the only record of the 0.90” PR interval.

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