Magnetocardiographic Intra-QRS fragmentation analysis in the identification of patients with sustained ventricular tachycardia after myocardial infarction

The aim of this study was to investigate if magnetocardiographic (MCG) anal ysis of cardiac micropotentials within the QRS complex can identity patient s prone to ventricular arrhythmias, and to compare it to MCG time-domain, l ate-field analysis. The study population consisted of 136 patients with rem ote MI, 53 with and 83 without a history of VT. After averaging and high pa ss filtering of multichannel MCG signals, time-domain parameters describing the end-QRS activity and fragmentation index M and score S describing the whole QRS complex were computed. Fragmentation and time-domain parameters d iffered between the VT and control groups: fragmentation index M was 12 +/- 3 versus 9 +/-2 (P < 0.001), fragmentation score S was 83<plus/minus>42 ver sus 56 +/- 21 (P < 0.001), and filtered QRS duration was 144<plus/minus>32 versus 114 +/- 19 ms (P < 0.001) in VT and control groups, respectively. A combination of fragmentation parameters yielded 87% sensitivity and 61% spe cificity in VT identification. Corresponding figures for a time-domain para meter combination were 81% and 72%. Sensitivity of time-domain analysis was 88% and specificity was 75% in a subgroup with anterior MI. In multivariat e analysis, fragmentation and time-domain analyses discriminated VT patient s from controls independently of the extent of coronary artery disease or l eft ventricular dysfunction. MCG in postinfarction patients reveals patholo gy associated with propensity to ventricular arrhythmias inside and not onl y at the end of the QRS complex. MCG seems most accurate in the anterior in farct location.