R-on-T VT?

Report:

Sinus rhythm

Left bundle branch block

Ventricular fusion beat (8th complex)

Ventricular tachycardia (flutter)188/min

Comment:

The answer to the question is: none - no significance!

It looks, at first, that the flutter starts with an R-on-T VEB: the last T wave of sinus rhythm appears truncated by the ectopic complex following it. To some extent it is true (like most illusions) - but its shape is altered well before the reach of the ectopic beat! It ascends to its peak with a different curve. Then, milking the QRS, one sees at once that it’s thinner than its fellow LBBB QRSs. Its R wave is also smaller: a fusion beat.

The initiating beat of the tachycardia is therefore not early, but very, very late67. We can further assume that, judging from the shape of the fusion beat, this first ectopic is different from the subsequent ones. A real R-on-T ectopic – from a different patient, but with a similar background – is shown below (Fig 70a).

The tachycardia can be, at least in this strip, called ventricular flutter: there are no distinctive QRS-ST-T components discernible. In other leads, however, this may not be so.

This patient had a LBBB with acute anterior infarction several years earlier (not shown).