Late-phase depolarization and repolarization abnormalities in english bulldogs with phenotypic expression of arrhythmogenic cardiomyopathy

In humans with arrhythmogenic cardiomyopathy (ACM) late-phase depolarization and repolarization abnormalities, such as epsilon (epsilon) waves and T wave inversion (TWI), are commonly observed in right precordial leads (V1-V3). This myocardial disorder has also been described in Boxer and English bulldogs (EBs), but data on electrocardiographic alterations in these breeds are lacking. The objective of this study was to describe electrocardiographic abnormalities in EBs with ACM, comparing QRS complexes and T waves with <= 5-year-old EBs without phenotypic expression of the disease. This is a retrospective study including 59 EBs (37 with ACM-ACM group and 22 healthy-healthy group). Standard echocardiographic, and 12-lead electrocardiogram data were retrospectively analyzed. In all leads QRS complex, R-peak time (RPT), and R peak-end time (RPE) were evaluated. Terminal activation duration (TAD), TWI, and presence of epsilon wave, defined as a positive small spike wave in right limb (aVR) and right precordial (V1) leads, were evaluated and compared with echocardiographic measurements. Arrhythmogenic cardiomyopathy group showed wider QRS complexes in all leads due to longer RPE (P < 0.05). The TAD in lead V1 was longer in ACM group (P < 0.001). The TWI and epsilon wave in ACM group were respectively present in 19% and 32%. Prolonged QRS complex and RPE in duration V1, the epsilon wave in lead aVR and V1, TWI and prolonged TAD in V1 were correlated with echocardiographic parameters defining right ventricular systolic function (P < 0.05). The presence of fragmented QRS complexes in limb and precordial leads, the prolongation of the RPE, the prolongation of TAD in V1, the presence of epsilon wave, can all be considered electrocardiographic features associated with ACM in EBs.