R-on-T Ventricular Fibrillation

Report:

Sinus tachycardia

Second degree AV block

VEBs

Bigeminy

R-on-T phenomenon

Ventricular fibrillation

ST segment elevation consistent with epicardial injury

Comment:

The VEB with the shortest coupling interval initiates VF. It comes right on top of the T wave; all the others occur just after the peak. The significance of this, traditionally fearful, phenomenon remains uncertain vis à vis VEBs occurring later30. Similarly, the significance of primary VF in acute MI continues to be redefined120.

The Cardiologist’s report of “Möbitz 2” and “4:1 A-V block” is remarkable. It must have been in a context like this when an Englishman said: The Americans scare me: they are so knowledgeable!

It is interesting to observe the doubling of the “block” due to the VEBs. In the single cycle without a VEB, at the end of the top strip, the block is clearly 2:1. VEBs causing advanced AV block de novo are shown in Case 202.

It has never been established whether one should, conventionally, report first degree AV block in the presence of a second degree one. It feels pedantic; I do not do it routinely. In this example, it points to the AV nodal site of the block (Möbitz 2 report notwithstanding) - hardly necessary in the presence of narrow QRS and acute inferior infarction. As the conduction ratio improves this patient would be expected to reveal Wenckebach AV block.

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