Evaluation of Maropitant-Induced Changes in the Electrocardiogram of Healthy Dogs and Comparison of Three Methods for QT Interval Correction.

Abstract

Objective: To assess for ECG changes, particularly affecting the QT interval, in healthy dogs administered maropitant and to compare methods of QT interval correction in dogs.

Design: Prospective interventional pre-post study.

Setting: University teaching hospital.

Animals: Twenty-seven healthy, privately owned dogs.

Interventions: After physical examination, bloodwork, and baseline six-lead ECG, dogs were administered a standard antiemetic dose of maropitant (1 mg/kg, SC). A follow-up ECG was performed 35-65 min later, after maximum plasma concentration was expected to be reached.

Measurements and main results: Twenty dogs completed the study. No adverse effects of maropitant were witnessed apart from apparent pain on injection, and no tachyarrhythmias or bradyarrhythmias were observed. ECG measurements included RR interval, QT interval, TQ interval, PR interval, P wave duration and amplitude, and QRS complex duration and amplitude. Instantaneous heart rate (HR) was determined based on the RR interval, followed by HR correction of QRS complex duration and QT interval using the Rautaharju, Van de Water, and Hodges formulas. Cardiac restitution was also evaluated using the QT/TQ ratio. Comparisons made before and after maropitant administration showed subtle prolongation of the QTc that only reached significance with the Van de Water formula and no change in the QT/TQ ratio. A significant reduction in P wave amplitude was observed with maropitant. An increase in variability between formulas at higher HRs was seen when QT interval correction formulas across a range of HRs were compared.

Conclusions: Maropitant administered subcutaneously at a standard antiemetic dose may induce a slight prolongation of the QTc and a reduction in P wave amplitude that are unlikely to promote tachyarrhythmias such as torsades de pointes or become clinically relevant in healthy dogs. The Van de Water formula may be more accurate across a wide range of HRs in dogs than the Rautaharju and Hodges formulas.