Mixed Bigeminy

Report:

Sinus rhythm 74/min

SVEBs, blocked

VEBs

Left ventricular hypertrophy with ST/T changes

Comment:

The diagnosis of sinus bradycardia is refuted by the negative (in the inferior leads) P waves – probably of junctional origin – after the first, fifth and sixth sinus beat. Marriott’s “commonest causes of pauses”135 follow the preceding QRSs by approximately 0.52”.

From the third sinus beat onward the rhythm is, in a sense, bigeminal: at first with the two VEBs and then with blocked SVEBs. The pulse would, most likely, reveal only a regular bradycardia 37/min.

In V1, the broad complex takes almost 0.08” to descend to its nadir: this makes a ventricular origin more likely than a supraventricular one, with LBBB aberrancy.

If the junctional extrasystoles were blocked retrogradely as well, the only evidence of their existence would be unexplained blocked P waves – a pseudoblock. Unfortunately, no examples could be found in this patient’s record. In the company of VEBs, the junctional SVEBs may well be main-stem (bundle of His) extrasystoles, with antegrade block. Standard ECG cannot tell them apart.

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