Modification of ventricular tachycardia by carotid sinus massage.

A case of ventricular tachycardia (VT) was aggravated by carotid sinus massage in a woman with an old myocardial infarction. The patient presented with a wide QRS complex tachycardia with a rate of 143 beats/min, which fulfilled the classic and newer electrocardiographic criteria for the diagnosis of VT. Carotid sinus massage performed during the tachycardia resulted in its conversion to another, wide QRS complex tachycardia, with different morphology and a faster rate resembling ventricular flutter. This latter tachycardia was converted to sinus rhythm by a thump on the patient's chest. The initial tachycardia was proved to be of ventricular origin by electrophysiologic study at a later stage during a recurrence. Vagal stimulation probably resulted in inhomogeneous increase of the ventricular refractory period, creating conditions for a reentrant circuit other than the preexisting one and for the emergence of VT with a different QRS morphology and rate. Although termination and/or initiation of VT by carotid sinus massage has been reported in the past, modification of VT by carotid sinus massage has not been described previously.