Twenty-four-hour ambulatory (Holter) electrocardiographic findings in 13 cats with non-hypertrophic cardiomyopathy.

Detection and characterisation of cardiac arrhythmias in cats with hypertrophic cardiomyopathy (HCM) has already been documented in various studies. However, similar studies have not been reported for other forms of feline cardiomyopathy. The clinical records of 13 client-owned cats diagnosed with restrictive cardiomyopathy (RCM), arrhythmogenic right ventricular cardiomyopathy (ARVC) and non-specific cardiomyopathy (NSCM) that underwent Holter recording at the time of diagnosis were reviewed retrospectively. Eight cats had signs of congestive heart failure at presentation, one cat had a history of recurrent syncope and the remaining four cats were asymptomatic. The average heart rate was 138 ± 22 (range 97-181) beats per minute (bpm) with the lowest value (97 bpm) recorded in a cat with third degree atrioventricular block (3-AVB) and the highest value (181 bpm) observed in a cat with atrial fibrillation (AF). The median number of ventricular ectopic beats (VEB) over 24 h was 2031 (338-8305), mostly represented by single isolated VPCs (803, 123-2221). Cardiac pauses were observed in three cats, with the longest pause lasting more than 6 s. A survival analysis was not performed due to the small number of cats and limited follow-up information. Holter recording revealed cardiac arrhythmias in all 13 cats, while 8/13 cats (61.5%) had an unremarkable resting electrocardiogram (ECG). The average daily heart rate in these cats did not appear affected by the presence of heart failure, although periods of sinus arrhythmia were absent in all individuals.