Prolonged heart repolarization ratio in Dobermans with early heart

Abstract

OBJECTIVE: The T-wave peak-end to QT ratio (TpTe:QT) is an ECG marker of myocardial repolarization dispersion that is not influenced by the RR interval. The authors hypothesized that TpTe:QT would be prolonged in Doberman Pinschers with dilated cardiomyopathy (DCM). METHODS: This retrospective cross-sectional study included clinically healthy Doberman Pinschers that were pyruvate kinase dehydrogenase 4 and/or titin genotype positive as the controls and dogs diagnosed with subclinical DCM as the DCM+ group. Data were collected between 2019 and 2024. Dogs receiving antiarrhythmic drugs were excluded. The QT interval, corrected QT interval, TpTe, TpTe:QT, and corrected TpTe were measured as repolarization markers with the use of ambulatory ECGs. Interrelationships among RR interval, DCM phenotype, and each marker were determined with a mixed-effects model. RESULTS: 36 dogs were included: 12 in the DCM+ group and 24 in the controls. The TpTe:QT was significantly higher in the DCM+ group compared to controls (risk ratio, 1.23), with negligible to weak correlation identified to RR interval (0.04 in controls; -0.16 in DCM+). The TpTe and corrected TpTe were also elevated in the DCM+ group (risk ratios 1.04 and 1.06, respectively): these values were significantly influenced by RR interval. CONCLUSIONS: TpTe:QT is a potential marker for distinguishing Doberman Pinschers with subclinical DCM from those that are normal, yet genetically at risk. Its independence from heart rate variation underscores its potential utility in clinical practice. CLINICAL RELEVANCE: TpTe:QT is a simple, noninvasive, and readily available test that may predict subclinical, clinically evident DCM in Doberman Pinschers. Larger clinical investigations of this easily obtained variable are warranted.