The utility of the T wave peak to T wave end interval to Q-T end interval ratio as a dynamic indicator of cardiac sympathetic activity: a preliminary study

Excessive cardiac sympathetic nerve activity significantly contributes to chronic heart failure (CHF) and lethal arrhythmias. However, reliable dynamic markers to assess sympathetic modulation are lacking in clinical practice. The T wave peak to T wave end interval (TpTe) to Q-T end interval ratio (TpTe/QTe) has been suggested as a surrogate marker for transmural dispersion of repolarization (TDR). We hypothesized that the TpTe/QTe reflects cardiac sympathetic nerve activity based on anatomical differences in the distribution and activation of cardiac sympathetic nerves. 12-lead Electrocardiograms (ECGs) were analyzed retrospectively in two cohorts without structural heart disease: (1) Exercise study; ECGs from patients who underwent treadmill or cardiopulmonary exercise testing between 2013 and 2023 were analyzed at baseline and 1-min post-maximal exercise. (2) β-stimulator infusion study; ECGs from patients who underwent catheter ablation (CA) of premature ventricular contractions (PVCs) or paroxysmal supraventricular tachycardias (PSVT) between 2017 and 2022 were analyzed at baseline and post-isoproterenol (ISO) infusion. In the exercise study, 45 patients (35.6% female, median age: 51) showed significant changes in the TpTe/QTe (interquartile range [IQR]: 0.20-0.30) from baseline to 1-min post-maximal exercise. In the β-Stimulator infusion study, 55 patients (63.6% female, median age: 55) had significant TpTe/QTe changes (0.19-0.33) from baseline to post-ISO infusion. The TpTe/QTe exhibited the largest change among the ECG parameters in both groups, regardless of sex, with no correlation to the left ventricular wall thickness. The TpTe/QTe may serve as a valuable dynamic indicator of cardiac sympathoexcitaion in patients without organic heart disease.