R-on-P Bigeminal Tachycardia

Report:

(Lead V1)

Sinus tachycardia 108/min

Incomplete right bundle branch block

VEBs (late-diastolic, R-on-P) in bigeminy

Comment:

The broader complexes, terminating slightly shorter cycles, fall at the end of sinus P waves. A “tad of fusion” cannot be excluded. The P-terminal force inscribes what could be the short broad R wave of the VEBs the true onset of the VEBs cannot be determined from this strip.

However, this patient had runs of VT with LBBB morphology and their QRS in V1 had 1 mm isoelectric beginning (determined from R waves in V2). Very likely, the broad little R in the strip overlaps the PTF.

Could the extrasystoles be of junctional origin, with LBBB aberrant conduction? This is unlikely: the cycles are not particularly short and any aberrancy would tend to exaggerate the RBBB pattern of the sinus beats rather than go for the LBBB.

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