Correlation of QT dispersion with indices used to evaluate the severity offamilial ventricular arrhythmias in Boxers

Objective-To measure QT Interval duration and QT dispersion in Boxers and t o determine whether QT variables correlate with indices of disease severity in Boxers with familial ventricular arrhythmias, Including the number of v entricular premature complexes per day, arrhythmia grade, and fractional sh ortening, Animals-25 Boxers were evaluated by ECG and echocardiography. Procedure-The QT interval duration was measured from 12-lead ECG and correc ted for heart rate (QTc), using Fridericia's formula. The QT and QTc were c alculated for each lead, from which QT and QTc dispersion were determined. Echocardiography and 24-hour ambulatory ECG were performed to evaluate for familial ventricular arrhythmias. Total number of ventricular premature com plexes, arrhythmia grade, and fractional shortening were determined and use d as indices of disease severity. Results-There was no correlation between any QT variable and total number o f ventricular premature complexes, arrhythmia grade, or fractional shorteni ng. No difference between QT dispersion and QTc dispersion was identified, and correction for heart rate did not affect the results. Conclusions and Clinical Relevance-QT Interval duration and dispersion did not correlate with Indices of disease severity for familial ventricular arr hythmias. Heart rate correction of the QT interval did not appear to be nec essary for QT dispersion calculation in this group of dogs. QT dispersion d oes not appear to be a useful noninvasive diagnostic tool in the evaluation of familial ventricular arrhythmias of Boxers. Identification of affected individuals at risk for sudden death remains a challenge In the management of this disease.