• G Sierra, F Molin, P Savard, B Soucy, and R Nadeau.
• Centre de Recherche Hôpital du Sacré-Coeur, Université de Montréal, Montréal, Canada. sierrag@crhsc.umontreal.ca
• Can J Cardiol. 1999 Nov 1; 15 (11): 1223-8.

ObjectiveTo discriminate between monomorphic (MVT) and polymorphic (PVT) ventricular tachycardias in humans using cycle length variability (CLV), and to characterize the onset of MVT and PVT using power spectral analysis of the CLV during sinus rhythm and the number of ventricular extrasystoles before onset of arrhythmia.Patients And MethodsMedtronic, Inc's Spontaneous Ventricular Tachy- arrhythmia Database was analyzed. This data base contains sets of 1000 RR intervals (n=135) that preceded spontaneous onset of ventricular tachycardia or fibrillation and sets of controls (n=135) without spontaneous ventricular tachycardia or fibrillation from 78 patients with the Medtronic Model 7218 implantable cardioverter defibrillator. CLV was measured as the standard deviation of RR intervals normalized by the mean RR value. Power spectral analysis based on the fast Fourier transform analysis was performed on 128 RR samples, and the normalized power spectrum of the low frequency band (0.04 to 0.15 Hz) and of the high (NHF) frequency band (0.15 to 0.4 Hz) were estimated.ResultsDuring PVT the CLV was much greater (0. 133+/-0.095) than during MVT (0.04+/-0.035) (P<0.0001). Also, 64% of patients who developed PVT had more than 27 extrasystoles compared with 40% of patients during control conditions (P=0.03). This parameter was not significantly different in patients with MVT. Due to the high incidence of extrasystoles in this population, only 36% of PVT and 43% of MVT recordings could be analyzed for CLV during sinus rhythm. NHF characterizing parasympathetic activity decreased from 50.6% (PVT control) to 34.4% (PVT onset) (P=0.06) and from 47. 4% (MVT control) to 43.7% (MVT onset) (P=0.18).ConclusionsDiscrimination between MVT and PVT episodes was possible based on CLV analysis. The onset of PVT was characterized by a greater number of preceding extrasystoles compared with the control. During sinus rhythm, the NHF spectral power activity decreased at the onset of both types of arrhythmic episodes compared with control, although statistical significance was marginal.

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