Standardization of the 24-hour electrocardiographic monitoring in dogs

The normal pattern for dynamic eletrocardiographic monitoring of Doberman, Boxer and Cocker Spaniel dogs, enhancing earlier diagnostic of dilated cardiomyopathy (DCM) was studied. For this, the technique of 24-hour electrocardiographic monitoring was standardized in 10 animals of each referred breeds. QRS complexes were more frequent in Cocker Spaniel than in Doberman and Boxer dogs. Ventricular premature beats were more common in Boxer dogs than in the other two breeds; however, all of then presented less than 1% of supraventricular ectopic beats in relation to the total of beatings. Cocker Spaniel dogs manifested the highest minimum, average and maximum heart rates and remained with heart rates equal or greater than 120bpm longer than Doberman and Boxer dogs otherwise, Cocker Spaniel dogs remained more time than dogs of the other two breeds with heart rate equal or lower than 50bpm. Cocker Spaniel dogs demonstrated, besides less frequently, shorter pauses than Doberman and Boxer dogs did. It was concluded that: a) clinically normal dogs of the studied breeds showed an evident variation of the heart rate; b) the isolate ectopic supraventricular and ventricular contraction were less than 50 during a 24-hour period of monitorization; c) in Boxer dogs, the number of isolated ectopic ventricular beats was less than 50 during a period of 24 hours; d) the periods of assistolia or pauses bigger than two seconds were frequent in Boxer and Doberman dogs and absent in Cocker Spaniel dogs; e) these pauses were commonly greater than three seconds; f) alterations of ST segment were not observed in clinically normal dogs of the three breeds studied.