Identification of malignant early repolarization pattern by late QRS activity in high-resolution magnetocardiography

The early repolarization pattern (ERP) in electrocardiography (ECG) has been considered as a risk for ventricular fibrillation (VF), but effective methods for identification of malignant ERP are still required. We investigated whether high spatiotemporal resolution 64-channel magnetocardiography (MCG) would enable distinction between benign and malignant ERPs.

Among all 2,636 subjects who received MCG in our facility, we identified 116 subjects (43 ± 18 years old, 54% male) with inferior and/or lateral ERP in ECG and without structural heart disease, including 13 survivors of VF (ERP-VF(+)) and 103 with no history of VF (ERP-VF(-)). We measured the following MCG parameters in a time-domain waveform of relative current magnitude: (a) QRS duration (MCG-QRSD), (b) root-mean-square of the last 40 ms (MCG-RMS40), and (c) low amplitude (<10% of maximal) signal duration (MCG-LAS).

Compared to ERP-VF(-), ERP-VF(+) subjects presented a significantly longer MCG-QRS (108 ± 24 vs. 91 ± 23 ms, p = .02) and lower MCG-RMS40 (0.10 ± 0.08 vs. 0.25 ± 0.20, p = .01) but no difference in MCG-LAS (38 ± 22 vs. 29 ± 23 ms, p = .17). MCG-QRSD and MCG-RMS40 showed significantly larger area under the ROC curve compared to J-peak amplitude in ECG (0.72 and 0.71 vs. 0.50; p = .04 and 0.03). The sensitivity, specificity, and odds ratio for identifying VF(+) based on MCG-QRSD ≥ 100 ms and MCG-RMS40 ≤ 0.24 were 69%, 74%, and 6.33 (95% CI, 1.80-22.3), and 92%, 48%, and 10.9 (95% CI, 1.37-86.8), respectively.

Magnetocardiography is an effective tool to distinguish malignant and benign ERPs.