Longitudinal Assessment of QT Apex in Tumor-Bearing Dogs Receiving Doxorubicin Monotherapy.

Abstract

BACKGROUND: The cardiac morphologic and functional derangements induced by doxorubicin (DOX) are referred to as DOX-induced cardiotoxicity (DOX-IC). Prolongation of the QT apex (QTa) has been identified as a potential marker for the early detection of DOX-IC in humans. OBJECTIVES: Describe changes in QTa that occur in dogs with cancer undergoing DOX monotherapy. ANIMALS: Forty-five client-owned dogs. METHODS: Descriptive analysis of data routinely recorded as part of case management of dogs with cancer. Dogs included in the study had a confirmed malignant neoplasm, received DOX as a monotherapy, and had at least 4 ECGs > 30 s. All ECGs included in the study were recorded before DOX administration. Five heartbeats with a stable signal and minimal artifact were randomly selected from each dog, and the QTa was blindly evaluated in lead II, lead III, or both. Subsequently, a linear mixed model was used to quantify the effect of a cumulative dose of DOX on the QTa interval, adjusting for the effect of the other clinical variables. RESULTS: Forty-five dogs met the inclusion criteria. Among them, 39/45 received five DOX treatments and 26/45 received six DOX treatments. For ECG analysis, 234 ECGs were evaluated for changes in the QTa. The average cumulative dose of DOX was 154.1 mg/m. There was no significant impact of the DOX treatments on the change in QTa (p = 0.8). CONCLUSIONS: Administration of DOX up to a cumulative dose of 154.1 mg/mdoes not result in QTa prolongation.