Non-Sustained Ventricular Tachycardia: Fusion and Narrow Capture Beats

Report:

Sinus tachycardia 108/min

Runs of ventricular tachycardia 134/min

Fusion beats

Possible old inferior infarction

Nonspecific ST/T changes

Comment:

The diagnosis of ventricular tachycardia is based on (i) R or qR complexes in V1; (ii) A-V dissociation; (iii) fusion beats; (iv) narrow capture beat terminating the second run of VT and (v) VEB, in the middle of the trace, of the same morphology as the runs. It is, by definition, non-sustained as its runs last less than 30 seconds.

Fusion is, itself, an incomplete dissociation or incomplete capture. It has great value in diagnosing the broad complexes as ventricular. Fusion (Dressler15) complexes have, of course, to occur exactly at the time when both pacemakers are expected to capture the chamber where fusion takes place16. The narrow capture beats, unlike fusion beats, are early (capture beats always are!); their diagnostic value is that they are narrow – if the fat complexes were supraventricular aberrancy, the capture beat should be even fatter than they are17.[! XE "Dressler beats" \t "See Ventricular tachycardia:fusion beats" !]

The runs of VT were not this patient’s priority; they were merely monitored until they disappeared, spontaneously. Non-sustained VT remains a difficult subject18.