Use of the signal-averaged ECG to predict maximum ventricular tachycardia rate

Rapid ventricular tachycardia is poorly tolerated, and estimation of maximum ventricular tachycardia rate prior to programmed ventricular stimulation is difficult. A method to estimate maximum ventricular tachycardia rate using late potential duration from the signal-averaged ECG and ventricular functional refractory period is described. Late potentials recorded in patients with ventricular tachycardia may represent delayed conduction through arrhythmogenic ventricular myocardium. This delay may be rate limiting in determining the minimum cycle length of reentrant ventricular tachycardia originating from these areas. Using the ratio of ventricular activation time (VAT), which equals QRS plus late potential duration, to unfiltered QRS duration (QRS) as estimate of this delay, the following relationship is proposed: Minimum ventricular tachycardia cycle length = (FRP 400 - 12.5 ms) (VAT/QRS). Twenty patients with late potentials who had sustained, monomorphic ventricular tachycardia at programmed stimulation were evaluated. Predicted cycle lengths ranged from 326 to 214 ms. Predicted and observed cycle lengths were significantly correlated (r = 0.91, SEE = 11.9 ms, p less than 0.0005), with predicted and observed cycle lengths differing by less than 3.5%. Predicted cycle lengths were more accurate than cycle lengths estimated using FRP alone (p less than 0.01). Accurate prediction of minimum ventricular tachycardia cycle length using this relationship suggests that late potential duration is proportional to the conduction delay occurring in arrhythmogenic ventricular myocardium.