Ventricular premature beat terminating SVT

Abstract

The following tracings were obtained in the EP lab during a SVT study. Fig. 1 shows a 12 lead recording of ECG of a patient showing termination of supraventricular tachycardia (SVT). The first 8 beats are narrow QRS short RP tachycardia e with the differential diagnosis of AVNRT or AVRT or less commonly atrial tachycardia. This train is followed by a single ventricular premature beat (VPB) delivered from a catheter in right ventricle, which terminates the tachycardia. On the 12 lead ECG, the single paced beat is seen as a fusion beat as it has some resemblance to a paced ventricular beat and some to the SVT beat. The fusion can result only if both the paced and SVT beats have excited the HisePurkinje system and confirms that the paced beat is His refractory. Fig. 2 shows the corresponding intracardiac recordings of the same event. The first 3 complexes are the SVT beats, where the atrial activation of distal coronary sinus appears to precede that of theHis andproximal coronary sinus suggesting possible involvement of a left sided accessory pathway. The single VPB (4th beat) is delivered during the SVT coinciding with the His deflection on the His catheter and this terminates the tachycardia. Subsequent 2 beats are sinus. Delivering of a His synchronous or