Fascicular VT with 1:1 Retrograde Conduction

Report:

Ventricular tachycardia 106/min

1:1 retrograde conduction

Comment:

This is a very slow VT – well within what some authorities would call AIVR. It is fascicular, with the QRS complex only 0.12” long. Its morphology is that of basic RBBB/LAHB, of known verapamil sensitivity. It differs importantly from true RBBB/LAHB: there are no septal q waves in L1 and the inferior leads have pure QS complexes (excluding LAHB), also seen in V4-6 (excluding preexcitation). The QR in V1 is also a rather unlikely morphology for RBBB, even though the patient may have had a septal infarct (Fig 129a, where V2 qRS supports it).

The retrograde P waves are well seen in the ST segment of aVL, L3, or V1-2. They have captured the atria and are likely to hold them until the VT subsides or the retrograde conduction is interrupted for long enough (by a VEB or a SVEB) to allow a sinus capture. This has no clinical significance apart from the possible observation of regular cannon waves in the central venous pressure trace.

Semiventricular Tachycardia

Report :

Sinus rhythm 52/min

First degree AV block (PR 0.24”)

Interpolated VEBs

Tachycardia 104/min

Right axis deviation (RAD) +110o

Non-specific ST/T changes

Comment :

Unlike Case 128, this one has VEBs interpolated in every cycle, doubling the heart rate. This is known (to me, at least) as semiventricular tachycardia70. One cannot, however, exclude interpolated junctional beats with RBBB/LPHB aberrancy, one (the first one in V1) with LPHB alone. Semijunctional, anyone?

The case for junctional origin is strengthened by the rhythm m recorded below (Fig 130a), two days after the original one. In this trace the three interpolated beats appear to be LPHB alone (the axis is seen in aVL and aVF) in the first and the third beat. The middle one has almost normal configuration. I think they are all both junctional and ventricular. How about His bundle extrasystoles?