Reference values of six-limb-lead electrocardiogram in conscious Labrador retriever dogs

Breed-wise standard electrocardiographic values in dogs have been reported as there is variation in body and chest conformation, which limits the application of data of one breed for other breed. Labrador retrievers being originated from hunting dogs, their electrocardiogram (ECG) values might be different from standard normal range of other dog breeds. So, the purpose of the present study was to determine the standard ECG of Labrador retrievers and to check effect of body weight, gender and breed upon different ECG parameters. Six-lead ECGs, three bipolar standard limb leads (I, II and III) and three augmented unipolar limb leads (aVR, aVL and aVF), were taken from 24 Labrador retrievers positioned in right lateral recumbency without any chemical restraint. Amplitude and duration of P wave and QRS complex, PR interval, QT interval and mean electrical axis and heart rate were measured in each recording. Non-significant effect of gender and body weight was seen on all the ECG waves. Deep Q waves in Leads I, II and aVF and variation in relation to QRS pattern were noted. It was concluded that retrievers had a specific shape of QRS complex which must be considered when evaluating a patient suspected of having cardiac disease. However, amplitude and durations of different ECG waves in all the six leads were statistically not affected by gender or body weight.