Spectral analysis of the cardiac cycle of signal-averaged Frank leads from patients with ventricular tachycardia.
Identification of the spectral features in electrocardiograms that distinguish patients prone to ventricular tachycardia (VT) is a prerequisite to increasing the diagnostic power of the signal-averaged electrocardiogram (SAECG). To determine distinguishing features of the magnitude spectrum, the spectra of SAECGs of sinus beats were analyzed over the entire cardiac cycle from 32 patients with VT, 30 without VT, and 10 normal control subjects. The magnitude spectra of the Frank SAECGs separated patients with VT from those without VT over the band from 7 to 140 Hz with a P value of .000000047. To determine distinguishing features of phase and group-delay spectra, SAECGs of sinus beats over the entire cardiac cycle were analyzed from 57 patients with VT, 65 without VT, and 20 normal control subjects. Unwrapped phase spectra from SAECGs of the entire cardiac cycle were calculated with respect to the onset of the Q wave. Phase spectra of SAECGs from patients with VT differed from those from non-VT patients at frequencies of 60 Hz or greater (P = .00085). Average group delays in SAECGs from patients with and without VT differed (P = .00000069) from 14 to 24 Hz. Group delays in the VT patients in the 14-24-Hz band were on average 9 ms and 5 ms longer than those of the non-VTs and normal subjects, respectively. Time-domain reconstructions demonstrated that distinguishing frequency bands were detectable throughout the QRS complex, ST-segment, and T wave in SAECGs from each group. Thus, the spectra of SAECGs over the cardiac cycle contain features that together with temporal features from throughout the cardiac cycle are essential in improving methods for stratifying risk of VT.
Arthur
R M
RM
Department of Electrical Engineering, Washington University, St. Louis, Missouri 63130.
Kavesh
N G
NG
Ambos
H D
HD
Cain
M E
ME
D004562:Electrocardiography; D006801:Humans; D009200:Myocardial Contraction; D012815:Signal Processing, Computer-Assisted; D017180:Tachycardia, Ventricular / Q000503:physiopathology*