Preliminary Study of Coupling Intervals of Premature Ventricular Complexes in Dogs With Different Cardiac Diseases

Coupling interval (CI), the time (ms) from the onset of a sinus QRS to the onset of the following premature ventricular complex (PVC), and their variability (CIV) might predict mortality and elucidate mechanisms of arrhythmogenesis. There has been limited investigation of CIV in dogs. Therefore, we determined CIV and prematurity index (PI) in three groups of dogs with ventricular arrhythmias that were subject to 24 hour ambulatory electrocardiographic (Holter) monitoring. Dogs in group 1 had presumptive arrhythmogenic right ventricular cardiomyopathy (ARVC), those in group 2 had structural heart disease in which patients with valvular heart disease predominated, and those in group 3 had a dilated cardiomyopathy (DCM) either phenotype or presumed familial cardiomyopathy. In this preliminary study, we did not find significant differences in indices of CIV between groups. Median PI was lower in dogs treated with antiarrhythmic therapy. Severity of cardiac remodeling, except for left atrial to aortic ratio, were not correlated with CIV. It was not possible to determine the mechanism of arrhythmias in ARVC, DCM phenotype or structural heart disease groups and re-entry, triggered activity, and abnormal automaticity are possible etiologies. The effect of antiarrhythmic therapy demonstrated potential drug effect on CIV. Risk for malignant arrhythmias and sudden cardiac death were not examined. A larger study would be needed to determine if differences exist; if present, this would give insight into possible mechanisms and optimal antiarrhythmic therapy.