VT: Dressler Beat

Report:

Ventricular tachycardia 188/min

Termination by ventricular fusion beat (Dressler beat)

Sinus tachycardia 120/min

Probable inferior infarction

Comment:

The rhythm strip is not taken simultaneously with the three channels above. This has the advantage of recording more events, but may look confusing to students used to simultaneous four-channel recordings.

Dressler beat12 is a fusion beat occurring during a run of VT. It is the sixth complex in the 12-lead ECG; it is preceded by a shorter VT cycle and terminates the VT run. In the rhythm strip itself there is, of course, another Dressler beat: the fourth QRS complex. The strip’s VT run is terminated by what looks like a VEB but may be a differently conducted complex of the same VT. This happened at the end of a 75 mg IV bolus of Xylocaine.

The VT morphology in V1 is QR rather than RSR’; the bizarre axis and the deep S wave in V6 also support the diagnosis of VT. Most importantly, the overall morphology does not look like any known fascicular block or combination of blocks; the one it comes closest to would be RBBB + LPHB. And finally, there is the Dressler beat itself.

It is of interest that the sinus beats in V1, both immediately after VT in the rhythm strip and in 12-lead ECG below (Fig 30a), have a slurred S descent. There is a qR in V6 and the QRS is only 0.10” long: the conduction delay is probably a nonspecific IVCD rather than incomplete LBBB. This morphology in V1 would certainly be misleading were the P waves not present – it’s an exception to the rule.

Leads 1 and aVL show the reciprocal S segment depression, but the expected similar depression is missing in the right precordial leads: there may be a right ventricular infarction as well.

30a. Slow S descent in V1 is unusual. The rhythm strip is mislabelled III instead of II. 31. 80 year old lady admitted with acute left ventricular failure.