Fascicular Ventricular Tachycardia & Positive Concordant Precordial Pattern

Report:

Ventricular tachycardia 198/min

Comment:

Fascicular ventricular tachycardia12,13 is distinguished by the relatively narrow QRS width and marked axis deviation in the frontal plane; in this case the QRS lasts just under 0.12”, less than in sinus rhythm with right bundle branch block and left posterior hemiblock (Fig 11a below); its axis is –55o. Presumably the ectopic focus in the His-Purkinje system is close to the major fascicles; in this case it may well be in the distal, unblocked portion of the left posterior fascicle.

This VT is usually responsive to verapamil or adenosine; it is sometimes called Belhassen tachycardia, at least by Belhassen himself and his friends and family14.

The sinus rhythm trace contains five VEBs with marked left axis deviation, also retaining basic RBBB configuration, but with different precordial pattern. These, too, may have fascicular provenance. The first three show retrograde conduction, the last two are dissociated from sinus P waves. This does not affect the constancy of their inter-ectopic distances or the difference in their coupling intervals: parasystole!

The third supraventricular beat is a junctional one, seemingly “forced” (perhaps “facilitated” is a better term) by the preceding VEB with retrograde conduction (its P wave in V1 is down-up rather than up-down).

Less disturbed sinus rhythm is seen in Fig 11b. Fig 11a. The basic parasystolic interval is between the second and the third VEB, also between the third and the fourth..

Fig 11b. Sinus rhythm with a single interpolated (intercalated) VEB. 12. Routine admission ECG of a 70 year old man with ischæmic foot from a thrombosed popliteal aneurysm.