Ventricular tachycardia: tricks and traps.

tachycardias. When unsure of the type of tachycardia, it is wise not to use verapamil. Intravenous amiodarone or procainamide can be used. When a broad-QRS tachycardia shows RBBB-type of morphology in lead V1, a monophasic or biphasic complex in V1 and R/S <1 in V6, suggests VT. A triphasic complex in leads V1 and V6 suggests SVT. On the other hand, when lead V1 shows LBBB-type of morphology; a broad (>40 ms) R or a slurred/notched S downstroke in lead V1, a distance ≥ 70 ms from QRS-onset to the nadir of QS complex in lead V1 or any Q wave in lead V6, suggests VT. A QRS width >140 ms favors the diagnosis of VT in patients with RBBB-type of broad-QRS tachycardia. QRS width is not of much discriminatory value in case of LBBB-type of tachycardia. However, fascicular VT, a narrow-QRS (120 ms) tachycardia responsive to intravenous verapamil, is often mistaken for SVT (Fig. 1). A qR-pattern, in related leads, during the tachycardia suggests post-infarct VT, with q waves pointing to infarct–site (Fig. 2). A north–west axis or a shift in a QRS–axis >40o (when compared to sinus rhythm) strongly indicates VT. A negative concordant QRS pattern in pre-cordial leads definitely suggests VT, whereas a positive concordant QRS pattern only implies that the ventricular activation is originating in the left posterior region, and could either be from a VT focus or a left posterior-located accessory pathway. During VT, P wave should be searched in the lead with the smallest QRS complex. Presence of AV dissociation, found in 50