Introduction: Ventricular repolarization dynamics modulate vulnerability to potentially life-threatening arrhythmias. The link between the repolarization sequence and the morphology of the T-wave of the surface ECG in the intact human heart is still poorly characterised. In this study we assessed 3 multi-lead ECG markers to track changes in dispersion of repolarization using intra-cardiac data recorded in patients with structurally normal ventricles.
Methods: Three decapolar catheters were used to simultaneously record unipolar electrograms in the right ventricular endocardium (RVendo), left ventricular endocardium (LVendo) and left ventricular epicardium (coronary sinus, LVepi) in 10 patients. The 12-lead ECG was simultaneously recorded. An S1S2 restitution protocol was conducted by pacing from the RVendo (n=8), LVendo (n=10) and LVepi (n=7). Total dispersion of repolarization (DRT) was measured in the beats following the short-coupled intervals as the interval between the earliest to the latest repolarization time (RT). The following markers of dispersion of repolarization were derived from inter-lead analysis of precordial and augmented limb leads of the surface ECG: (1) Interval between the earliest and the latest maximum upslope of the T-wave (ΔdVdt-max); (2) Interval between median T-peak and median T-end (Tpe-med); (3) Interval between the earliest T-peak and latest T-end (Tpe-range). Results are show as median and Q1-Q3 interval.
Results: Changes in DRT from cycle length equal to 1000 ms to effective refractory period (240, 223-250 ms) were equal to 94.4±36.9 ms. Intra-patient correlation (Pearson’s correlation coefficient) between changes in DRT and changes in surface ECG markers was equal to 0.79 (0.66-0.89) for ΔdVdt-max, 0.71 (0.44-0.79) for Tpe-range and 0.61 (0.14-0.76) for Tpe-med. Group differences were significant (P=0.017, Kruskal-Wallis test) and pair-wise comparison showed that ΔdVdt-max correlated significantly better than Tpe-med (p=0.001) and almost significantly better than Tpe-range (P=0.054) with DRT.
Conclusions: Multi-lead index ΔdVdt-max tracks changes in dispersion of repolarization with high intra-patient correlation.