Ventricular parasystole in a dog and a cat.

In human beings, ventricular parasystole usually is a benign arrhythmia with an ectopic focus that fires independently from the rest of the heart. The specific electrocardiographic criteria used to diagnose this condition are variable coupling intervals with the preceding beat; interectopic intervals, all multiple of the same number; and fusion beats. Ventricular premature beats having those characteristics were identified in a dog and a cat, both free of detectable, structural heart disease. In these cases, the arrhythmia was refractory to treatment, but the animals were clinically normal. Recognition of this kind of arrhythmia is important because it may help in avoiding unnecessary concerns and treatment.