Beat-to-beat vectorcardiographic analysis of ventricular depolarization and repolarization in myocardial infarction

Objectives: Increased beat-to-beat variability in the QT interval has been associated with heart disease and mortality. The purpose of this study was to investigate the beat-to-beat spatial and temporal variations of ventricular depolarization and repolarization in vectorcardiogram (VCG) for characterising myocardial infarction (MI) patients. Methods: Standard 12-lead ECGs of 84 MI patients (22 f, 63612 yrs; 62 m, 56610 yrs) and 69 healthy subjects (17 f, 42618 yrs; 52 m, 40613 yrs) were investigated. To extract the beat-to-beat QT intervals, a template-matching algorithm and the singular value decomposition method have been applied to synthesise the ECG data to VCG. Spatial and temporal variations in the QRS complex and T-wave loops were studied by investigating several descriptors (point-to-point distance variability, mean loop length, T-wave morphology dispersion, percentage of loop area, total cosine R-to-T). Results: Point-to-point distance variability of QRS and T-loops (0.1360.04 vs. 0.1060.04, p, 0.0001 and 0.1660.07 vs. 0.1360.06, p, 0.05) were significantly larger in the MI group than in the control group. The average T-wave morphology dispersion was significantly higher in the MI group than in the control group (62u68u vs. 38u616u, p, 0.0001). Further, its beat-to-beat variability appeared significantly lower in the MI group than in the control group (12u65u vs. 15u66u, p, 0.005). Moreover, the average percentage of the T-loop area was found significantly lower in the MI group than the controls (46617 vs. 55615, p, 0.001). Finally, the average and beat-to-beat variability of total cosine R-to-T were not found statistically significant between both groups. Conclusions: Beat-to-beat assessment of VCG parameters may have diagnostic attributes that might help in identifying MI patients.