Use of tachycardia templates for recognition of recurrent monomorphic ventricular tachycardia

The authors show that the ventricular electrograms of recurrent monomorphic ventricular tachycardia (VT) having an identical 12-lead surface configuration can be matched to a template constructed from a previous episode of the same VT. This could allow assessment of the number of times a device has delivered therapy for a known VT, in addition to the total number of therapies for cardiac rhythms that may have exceeded a rate criterion and/or morphology criterion. Templates constructed during monomorphic VT in 12 patients were examined by means of correlation waveform analysis (CWA) and area of difference (AD). With CWA the VT templates correctly discriminated 902/936 (97%) ventricular depolarizations, and AD correctly discriminated 932/936 (99%) depolarizations when the same VT was reinduced. The study used acute leads positioned during electrophysiologic study and has not been tested or validated on chronic leads. The monomorphic VT was reinduced during a single electrophysiology study. Whether changes in heart substrate or structure may cause changes in the intracardiac VT morphology over time has not been determined