Background: Ischemic heart disease (IHD) is the leading cause of mortality world-wide. The majority of these deaths are due to lethal ventricular arrhythmia (VA). A promising marker of increased arrhythmia risk is beat-to-beat variability of repolarization (BVR). (Semi-)automated BVR analysis could improve non-invasive risk stratification and may be valuable in the management and prevention of VA in IHD patients. This paper uses a semi-automated framework to investigate the temporal evolution in BVR before spontaneous non-sustained ventricular tachycardia (nsVT) in patients with IHD.
Methods: 24h Holter recordings from 20 IHD patients were collected prior to ICD implantation. The R-peaks were detected by an in-house developed algorithm, adapted from the Pan-Tompkins algorithm. After R-peak detection, Q-wave deflection and the end of the T-wave were located with a semi-automated template matching technique. The QT annotation was manually verified and adjusted if necessary. Episodes of nsVT were semi-automatically identified and BVR was assessed at time points 1, 5 and 30 minutes prior to nsVT, and at a fixed moment during sleep (3:00am). BVR was calculated from 30 consecutive beats, excluding ventricular ectopic beats. The resulting BVR was compared by repeated measures ANOVA.
Results: Resting BVR measured at 3:00am was 6.64 ±1.79ms and was significantly (p<0.05) increased at 5 minutes (15.26 ±1.67ms) and 1 minute (17.88 ±2.25ms), but not at 30 minutes (9.2 ±2.82ms) prior to nsVT.
Conclusion: Temporal changes in pre-arrhythmic BVR could be used to predict imminent nsVT in this subset of IHD patients. These preliminary results set a strong precedent that both reinforces the value of BVR analysis in the risk stratification of IHD patients; and identifies a novel method of impending VA prediction that could be used for real-time analysis and monitoring.