Interpolated Main-Stem Extrasystoles

Report:

Sinus rhythm 80/min

Interpolated junctional or bundle of His (main-stem) extrasystoles

Allorhythmic triplets

Left bundle branch block

Primary T wave changes

Comment:

There is a regular sinus rhythm, even though the initial impression may be of recurrent SVEBs in couplets, the second SVEB being, perhaps, a reentry beat in view of the P wave sandwiched between the SVEBs. The polarity of such P waves may be difficult to tell. However, transposition of sinus P waves shows that all the P waves are sinus!

The premature complexes have the same basic LBBB morphology as the sinus beats: the slight difference may be due to non-phasic aberrant conduction reflecting their junctional provenance. Subsequent PR intervals are prolonged through concealed retrograde conduction and subsequent sinus R-R intervals are slighly shorter (by the amount of previous PR prolongation) than the others. Had the P waves following the extrasystoles been completely blocked, the patient would have common or garden trigeminy93.

The T wave changes are subtle but definite: T waves should be inverted in leads V5 and V6. The pattern was stable over time (Fig 146a below is another Outpatient trace) but it does reflect a myocardial problem.

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