Electrocardiographic Findings in Clinical Healthy Adult Borzoi Dogs with a Normal Echocardiogram

Abstract: Background– Borzoi dogs reportedly experience sudden death.

Objectives– To report electrocardiogram (ECG) intervals, amplitudes, and frequency of ECG abnormalities in clinically healthy Borzoi.

Animals– Eighty-two client-owned Borzoi.

Methods– Clinically healthy Borzoi were prospectively recruited as part of a larger cohort study and underwent an echocardiogram and an ECG. Borzoi with structural cardiac abnormalities were excluded. Standard ECG measurements were obtained. QT interval was corrected (QTc) using the Van de Water formula.

Results– Of 82 Borzoi with a structurally normal echocardiogram, ventricular arrhythmias were seen in six dogs and supraventricular premature complexes in one dog. Median P wave duration was 55 msec (range: 45-70 msec). Median PR interval was 125 msec (range: 80-175 msec), with 31 Borzoi (37.8%) having first degree atrioventricular block (PR interval > 130 msec). Median QRS duration was 65 msec (range: 48-90 msec). The median QT interval was 235 msec (range: 185-275 msec). The median QTc interval was 270 msec (range: 223-304 msec). Twenty-nine of 82 Borzoi had a QT interval > 240 msec (35.4%). Seventeen of 82 Borzoi (20.7%) had an abnormality of the ST segment, most commonly convexity/doming. Convexity of the ST segment was intermittent in nine dogs and persistent in four.

Conclusions and clinical importance– Prolonged QT intervals and ST segment abnormalities are not infrequent in clinically healthy Borzoi with normal echocardiograms. Whether these ventricular repolarization abnormalities relate to the reported predisposition for sudden death warrants further investigation. P, PR, and QRS durations are also commonly prolonged compared to reference intervals in other dogs.