Preliminary investigation of T-wave peak-end interval and its ratio to QT interval in dogs with an echocardiographic phenotype of dilated cardiomyopathy and its possible correlation with left ventricular diameter and volume

Objective: The T-wave peak-end (TpTe) interval and its ratio to the QT interval (TpTe:QT) are ECG markers of myocardial repolarization dispersion. We hypothesized that these markers are associated with echocardiographic indices reflecting structural remodeling in dogs with the dilated cardiomyopathy (DCM) phenotype and are minimally influenced by heart rate (HR). Methods: A cross-sectional study was conducted in dogs with an echocardiographic subtype of DCM, excluding sighthound breeds, between July 2021 and June 2023. Dogs receiving antiarrhythmic drugs prior to the diagnostic ECG were excluded. Repolarization markers (QT interval, corrected QT interval using the Fridericia formula [QTc], TpTe interval, and TpTe:QT) were retrospectively evaluated from in-clinic ECGs and correlated with echocardiographic variables (left ventricular end-diastolic diameter normalized to body weight [LVEDDN], left ventricular end-systolic diameter normalized to body weight [LVESDN], end-diastolic volume, end-systolic volume [ESV], end-diastolic volume normalized to body surface area, ESV normalized to body surface area, fractional shortening, and ejection fraction). Results: Correlation analysis between repolarization markers and HR showed a significant moderate negative correlation for the QT interval, whereas QTc exhibited a weak positive correlation. The TpTe interval showed a weak negative correlation, and TpTe:QT demonstrated a negligible correlation with HR; however, neither association was statistically significant. The TpTe interval showed significant weak correlations with LVEDDN and LVESDN, whereas TpTe:QT showed significant weak to moderate correlations with LVEDDN, LVESDN, ESV, and ESV normalized to body surface area, even after adjustment for HR. In contrast, QT and QTc were not significantly associated with any echocardiographic variable. Conclusions: The TpTe interval and TpTe:QT might have been independent of HR and correlated with left ventricular diameter and volume. Clinical Relevance: The TpTe interval and TpTe:QT may serve as ECG repolarization markers reflecting myocardial structural remodeling in dogs with DCM.