Beat-to-beat spatial and temporal analysis for QRS-T morphology

The aim of this study was to investigate beat-to-beat variations of spatial and temporal QRS and T loop morphology for identifying myocardial infarction (MI) patients. We investigated short-term 12-lead ECG recordings of 84 MI patients (22 female, mean age 63 ± 12 years and 62 male, mean age 56 ± 10 years) and 69 healthy control subjects (17 female, mean age 42 ± 18 years and 52 male, mean age 40 ± 13 years). To quantify spatial and temporal variations in QRS complex and T-wave morphology, we defined two descriptor parameters: point-to-point distance variability (DV) and mean loop length (MLL). These parameters were extracted from the reconstructed vector ECG, using singular value decomposition. The results showed that the beat-to-beat spatiotemporal point-to-point distance variability for QRS and T loops (DV_QRS; 0.13±0.04 vs. 0.10±0.04, p <; 0.0001 and DV_T; 0.16±0.07 vs. 0.13±0.06, p <; 0.05), were significantly higher in MI subjects compared to control subjects. In addition, the mean loop length of QRS and T loops were significantly higher in control subjects than MI (p <;0.001), respectively. In conclusion, the beat-to-beat spatiotemporal DV and MLL may be useful for characterizing conduction and repolarization characteristics in patients with MI.