Magnetocardiographic study of ventricular repolarization in hypertensive patients with and without left ventricular hypertrophy

Previous studies in magnetically shielded rooms have shown that magnetocardiographic (MCG) mapping can be useful to detect early signs of left ventricular hypertrophy (LVH). The aim of this study was to evaluate ventricular repolarization parameters in patients with essential hypertension, associated or not with LVH, by means of unshielded multichannel MCG mapping. METHODS: 31 patients with pharmacologically treated essential hypertension (average BP systolic: 147.8+/-11.2, diastolic: 92.2+/-4.9) since 6.5+/-5.6 years, 13 without and 18 with evidence of LVH (4 by ECG, 11 by echocardiography, and 3 at both), were studied with a 36-channel MCG system (sensitivity of 20 fT/square root of Hz1/2) and with 12-lead ECG, in an unshielded hospital setting. To assess ventricular repolarization, HR-corrected, QTend, JTpeak, JTend, Tpeak-end intervals and QT dispersion (QTd) were measured from both MCG and ECG waveforms. The magnetic field gradient orientation (alpha angle) during the ST interval and at the Tpeak was also computed. 20 normal age-matched volunteers were used for comparison. RESULTS: As compared to normal volunteers, MCG JTend, QTend, Tpeak-end and QTd were significantly longer in hypertensive patients. The difference was not significant, if only patients with essential hypertension but no LVH were considered. The magnetic field alpha angle during the ST was significantly abnormal in patients with essential hypertension (p < 0.01). CONCLUSIONS: In patients with essential hypertension, MCG detects alterations of ventricular repolarization, not evidenced by 12-lead ECG.