Abstract 11291: Visualization of Intra-QRS Fragmented Activation in Patients with Hypertrophic Cardiomyopathy and Life-Threatening Ventricular Tachyarrhythmias Using Magnetocardiography
Backgrounds: Previous studies indicated that intra-QRS fragmentation (QRSf) on ECG is a possible marker of lethal ventricular arrhythmias in ischemic and other heart diseases, the origin of QRSf remains unclarified, however. We hypothesized that patients with hypertrophic cardiomyopathy (HCM) who had experienced ventricular tachycardia (VT) or fibrillation (Vf) exhibit similar abnormalities, which can be visualized by high-resolution multi-channel (64-Ch) magnetocardiography (MCG).
Methods: In 21 HCM patients with narrow QRS (<120ms) and a history of VT (n=11) and Vf (n=10), necessitating implantable cardioverter defibrillator (ICD) subsequently, we examined the presence of QRSf on 12-lead ECG (500Hz) and analyzed 2-dimensional QRS current arrow mapping with a 64-Ch MCG system (MC-6400, Hitachi, 1kHz). We measured left ventricular (LV) conduction time defined as an interval from QRS onset to LV End, the instant when the visualized LV leftward current disappears. Healthy volunteers (n=25) served as Controls.
Results: In 19 of 21 patients, QRSf was recognized on ECG. MCG analysis revealed that LV conduction time in HCM patients was markedly prolonged compared with Controls (73±17 vs 51±5 ms, p<0.001). In Controls, after the initial rightward currents (septal activation), uni-directional left-downward currents appeared up to 50-55 ms after QRS onset, followed by RV activation (Figure). In contrast, this normal pattern was not observed in all of HCM patients. In 15 of 19 patients, during the period corresponding to QRSf, we recognized abnormal, complicated current patterns (mostly multi-directional currents appearing simultaneously, Figure).
Conclusions: Patients with HCM and a history of life-threatening ventricular tachyarrhythmias often showed intra-QRS fragmentation on ECG. This depolarization abnormalities, possibly associated with the occurrence of lethal arrhythmias, can be noninvasively visualized on the MCG 2-D current mapping.
- Noninvasive cardiac imaging
- Hypertrophic cardiomyopathy
- Implantable cardioconvert defibrillator
- Ventricular fibrillation
- Ventricular tachycardia
- © 2011 by American Heart Association, Inc.