Left shift of the ventricular mean electrical axis in healthy Doberman Pinschers

In canine electrocardiography, the reference interval of the ventricular mean electrical axis (MEA) is between +40 degrees and +100 degrees. MEA values in dogs can be influenced by the patient position as well as by the shape of the thorax. The aim of this study was to evaluate the MEA in healthy Doberman Pinschers, hypothesizing that some present a left shift of the MEA. In this retrospective study, 41 healthy, client-owned Doberman Pinschers were included. Echocardiography and standard six-lead ECG examination were performed in all dogs. The MEA was calculated using the isoelectric method. The morphology of the QRS complex and the Q/R ratio in lead II were also evaluated. The median MEA was + 45 degrees and ranged from -45 degrees to +90 degrees. MEA was deviated in 16/41 dogs (39%), all presenting a left axis deviation (range, -45 degrees to + 30 degrees). Age was significantly associated with the MEA (P=0.008), showing a negative linear correlation. A deep Q wave in lead II was present in 26/41 (63%) dogs. The Q/R ratio was higher in dogs presenting left shift of the MEA (0.66; range, 0.28-1.35) in comparison to dogs with a MEA within reference range (0.44; range, 0.04-0.73; P<0.001). In conclusion, a significant number of healthy Doberman Pinschers present a left shift of the MEA compare to the reference range, and dogs with MEA deviation show a higher Q/R ratio in lead II. This data should be considered when electrocardiographic evaluation is performed in Doberman Pinschers.