SUMMARY Intracardiac electrophysiologic studies were performed in two patients who had recurrent sustained ventricular tachycardia. In both, the tachycardia was repeatedly terminated by carotid massage. In one patient, intracardiac electrophysiologic studies revealed ventricular tachycardia with 2: 1 retrograde ventriculoatrial (VA) block. Carotid massage resulted in alternate Wenckebach retrograde VA conduction terminated by ventricular echo beats. When ventricular echo beats occurred at a coupling interval of 340-400 msec, the tachycardia was terminated. Similarly, induced atrial depolarizations (during ventricular tachycardia) produced ventricular capture and terminated the tachycardia when the resultant ventricular coupling interval was 330-395 msec. In the second patient, progressively premature atrial or ventricular depolarizations did not terminate the tachycardia. Carotid massage had no consistent effect on retrograde VA conduction during ventricular tachycardia, but usually resulted in gradual increases in the tachycardia cycle length (50-100 msec) before abrupt termination of the tachycardia. This is the first report documenting termination of ventricular tachycardia by carotid massage alone (i.e., without prior drug intervention); hence, tachycardia termination by simple carotid sinus massage does not prove a supraventricular origin. The mechanism of tachycardia termination was due to ventricular echo beats from retrograde atrioventricular nodal reentry in one patient and to direct vagal effects on either the ventricular muscle or the ventricular specialized conduction system in the other.DIFFERENTIATION of ventricular from supraventricular tachycardia with aberrant conduction traditionally includes the application of maneuvers that either enhance vagal or inhibit sympathetic tone.' 3 These include the Valsalva maneuver, carotid sinus massage, and the administration of edrophonium hydrochloride or phenylephrine. Termination of a regular wide-QRS-complex tachycardia using these techniques suggests a supraventricular origin. However, ventricular tachycardia can be terminated by either phenylephrine administration or by application of carotid sinus massage after pretreatment with edrophonium hydrochloride.' 6 We studied two patients with recurrent ventricular tachycardia who could terminate their wide-complex tachyarrhythmias by carotid sinus massage alone. Documentation of this phenomenon in the absence of pharmacologic manipulations is reported and adds to the growing evidence that changes in autonomic tone can significantly influence ventricular arrhythmias. Materials and MethodsAll studies were performed in a cardiac catheterization laboratory. Both patients gave informed consent. Patient 1 had been taking quinidine, but the medication was discontinued 48 tion. During the study, four quadripolar electrode catheters were inserted into the right femoral vein. Catheters were positioned in the high lateral right atrium, across the tricuspid valve, in the apex of the right ventricle, and across a patent...
A patient with recurrent bouts of atrial fibrillation and wide-complex regular tachycardia underwent electrophysiologic studies. Premature atrial stimulation or atrial pacing during sinus rhythm resulted in gradual lengthening of the PR and AH intervals, narrowing of the HV interval and progressive preexcitation with a left bundle branch block and left-axis contour. Induction of tachycardia was dependent on critical delay in the atrioventricular interval and was associated with attainment of a maximal preexcitation pattern. During tachycardia, the ventriculoatrial interval was constant, whereas the interval from His bundle deflection to the ventricular complex was variable. We postulate that the tachycardia circuit involved reciprocation within the atrioventricular node and that a nodoventricular bypass tract was present in close anatomic or functional association with the slow atrioventricular nodal pathway. Our data suggest that both the nodoventricular bypass tract and the His-Purkinje system may be passive "bystanders" rather than essential components of the tachycardia circuit. In addition, although HV dissociation usually implies ventricular tachycardia, this case demonstrates that HV dissociation during wide-complex regular tachyarrhythmia is not diagnostic of ventricular tachycardia.
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