Efficacy and safety of different antiarrhythmic protocols used for rate control in dogs with secondary atrial fibrillation

Studies comparing the effects of antiarrhythmic protocols used for rate control in dogs with secondary atrial fibrillation (AF) are currently limited. Therefore, this study aimed to report detailed data on the efficacy and therapy-related side effects (TRSEs) of different antiarrhythmic protocols in dogs with secondary AF. Dogs with secondary AF treated with combination therapy with diltiazem and digoxin (CT Dilt+Digox ), diltiazem monotherapy (MT Dilt ), digoxin monotherapy (MT Digox ), or amiodarone monotherapy (MT Amiod ) were retrospectively evaluated. Signalment, clinical, diagnostic, therapeutic, and outcome data were retrieved. Electrocardiographically, antiarrhythmic efficacy was defined by a reduction in the mean heart rate on Holter monitoring ≤125 beats/minutes. Statistical analysis was performed to compare selected data, including the rate of efficacy and TRSEs as well as the median survival time, between dogs treated with different antiarrhythmic protocols. Fifty-four dogs were included, 28 receiving CT Dilt+Digox and 26 receiving monotherapies (MT Digox =16; MT Dilt =5; MT Amiod =5). The efficacy rate documented in dogs treated with CT Dilt+Digox was significantly higher than that observed in dogs from the composite monotherapy group (i.e., MT Dilt +MT Digox +MT Amiod ) (P = 0.048). The rate of TRSEs documented in dogs treated with CT Dilt+Digox was similar to that observed in dogs from the composed monotherapy group (P = 0.129). The median survival time documented in dogs treated with CT Dilt+Digox was significantly longer than that observed in dogs of the MT Digox group (P = 0.01). In dogs with secondary AF, CT Dilt+Digox is generally well tolerated and provides clinically relevant benefits compared to the use of a single antiarrhythmic drug.