Cardiac dysrhythmias in clinically healthy heifers and cows

In bovine medicine, electrocardiography has been mainly used for detection of cardiac dysrhythmias, as deep penetration of the Purkinje fibers in the myocardium in large animals, including ruminants, makes it unsuitable for determination of chamber enlargement. For detection of cardiac dysrhythmias, large electrocardiographic configurations and clear separation of the duration of the phases of the waveform facilitate the interpretation of electrocardiogram (ECG). In large animals, including cattle, a base apex lead has been shown to be an ideal lead system for monitoring cardiac dysrhythmias [19]. Cardiac dysrhythmias can be either primary or secondary and pathological or functional. A review of the veterinary literature shows that the majority of cardiac dsyrhythmias in cattle are physiological, that is they have no deleterious effects on the heart and no lesions can be found in the cardiovascular system at necropsy [9, 11]. However, pathological dysrhythmias have also been reported which are life threatening if not treated [4, 10, 20].