VF: R-on-T Phenomenon

Report:

Top:

Rhythm of uncertain origin, 57 - 67/min

Intraventricular conduction delay QRS 0.20”

VEB, R-on-T phenomenon

Ventricular fibrillation

Middle :

Ventricular fibrillation

DCC and CPR artefact

Bottom :

Idioventricular or junctional rhythm 57/min

Probable exit block

Marked QRS prolongation

Comment:

First and third QRS are preceded by atrial activity, but the PR intervals are different and it is unlikely to represent a conducted sinus rhythm. The money is on irregular atrial activity, perhaps even AF.

Ventricular fibrillation starts with the R-on-T VEB, although some authors would describe the strip as VT “degenerating” into VF. I think it’s VF ab initio. The initiating VEB is very early, with about 0. 36” coupling interval; it takes the preceding T wave at its peak.

Another controversy surrounds the R-on-T phenomenon, as seen in this example. My impression (and, obviously, Lown’s) is that in the setting of acute infarction the phenomenon is quite real. That’s why Lown classified it as Grade V ventricular ectopic activity. There are studies, however, that show the R-on-P to be equally dangerous!

This episode (there were many) of resuscitation was successful: a formed rhythm emerged. Its complexes are so broad and bizarre that one may be, at first, led to believe they are only a CPR artefact. But the regular rate, the initial R wave and the nipple at the bottom of each S wave all attest to them being real QRS complexes, with ensuing T waves as well.

167. 68 year old man with 90% stenosis of the proximal left anterior descending artery during the contrast injection into the left (main) coronary artery. [Paper speed 12.5 mm/sec, then doubled]