Frequent, Multiform, R-on-T VEBs in Acute MI

Report:

Atrial fibrillation

Possible run of accelerated junctional rhythm 75/min (first four beats)

VEBs, dimorphic couplet, R-on-T phenomenon

Acute anterolateral infarction

Probable old inferior infarction

Comment:

There is obvious ST segment elevation with early T inversion in the anterolateral leads, but no reciprocal changes. This may be due to a previous inferior infarction (despite miniscule and variable R waves in lead 3). Lead 2 also shows some ST elevation; sometimes it joins the anterior leads.

The VEBs are early-coupled at 0.28”. This is no longer regarded as malignant “grade V” ectopic activity but still commands respect, even though we know that as many episodes of VT or VF are initiated by late as by early VEBs54. In this case, the early VEBs did cause first transient and then sustained runs of very fast multiform VT (not true torsades in this setting). The sustained run received a 200 Joule shock and did not return, but the early VEBs persisted despite belatedly instituted xylocaine therapy. The shock also effected a true defibrillation in the case of AF, but this benefit did not last long (75a).

Interestingly, the early VEBs have rsR’ configuration in V1 – both in the 12-lead ECG and in the monitor rhythm strips. They also have, in the ECG at least, long-short sequencing characteristic of aberrant conduction (Ashman’s phenomenon). This is unusual. On the other hand, R-on-T occurrence is itself evidence of ventricular ectopy.