HIGH-PASS-FILTERED MAGNETOCARDIOGRAM AND CARDIOMYOPATHY IN PATIENTS WITH TYPE-1 DIABETES-MELLITUS

Prolonged and/or fractionated depolarization due to tissue degeneratio n of the ventricular myocardium is a feature of cardiomyopathy. Signal averaged electrocardiography uses high-pass filters of the Butterwort h type to quantify noninvasively, fractionated high-frequency componen ts at the end of the QRS complex. In this study a finite impulse respo nse high-pass filter of the 90th order (cutoff at 37 Hz) was applied t o magnetocardiograms (MCGs) and high-resolution electrocardiograms (EC Gs) order to quantify high-frequency components throughout the myocard ial depolarization Additionally, late-potential analysis on the signal -averaged ECG was performed. A prospective investigation was made of 2 3 cardiologically asymptomatic patients, 11 females and 12 males, with type I diabetes mellitus. Their mean age was 21.7 years (range, 13-34 years). The mean duration of diabetes was 14 years (range, 1-27 years ). Data were compared with those of 22 control subjects (12 females, 1 0 males) of mean age, 23.2 years (range, 11-35 years). The ECGs and MC Gs were simultaneously recorded and signal-averaged, digitally filtere d, and quantified by a score obtained by multiplying the amplitude var iation of the signal by the number of maximal/minimal in the QRS compl ex. Echocardiograms were used to calculate the left ventricular mass a nd to document the presence of cardiomyopathy. Scores were higher in t he MCGs of with type I diabetes mellitus than in the control subjects (P < .001). High scores correlated with an increased left ventricular muscular mass index (P < .05) and duration of the diabetes (P < .05). The high-resolution EGG, processed analogously, showed similar results in relation to left ventricular mass (P = .06) and duration of diabet es (P = .07), respectively (nonsignificant). No late potentials were f ound. These findings suggest that using a linear-phase high-pass finit e impulse response filler may be useful for the noninvasive identifica tion of patients with cardiomyopathy wile exhibit possible disturbance s of intraventricular depolarization. Our findings that analysis using the total QRS complex, rather than the final part of the QRS complex only, may improve identification of patients at risk.