Evaluation of electrocardiographic parameters, thoracic morphometry and vertebral heart size in clinically normal dogs

ABSTRACT

Background: The Vertebral Heart Size (VHS) method sets standards for the evaluation of dog’s heart size from the comparison of the cardiac dimension with the length of the thoracic vertebrae through radiographic study. Electrocardiogram(ECG) is widely used in veterinary medicine for the evaluation of electrical conduction system of the heart; however, theincrease of duration and amplitude of the ECG waves can suggest the increase of cardiac chambers in dogs. The scientificliterature presents electrocardiographic and VHS values for dogs of different breeds and sizes; however, there is little information on the correlation of these parameters. Therefore, the aim of this study was to evaluate the amplitude and durationof ECG waves, thoracic morphometry and VHS values, in order to correlate these parameters in clinically normal dogs.Materials, Methods & Results: Twenty healthy dogs (11 females and 9 males), without breed distinction, medium sized(14.46 ± 2.92 kg) and aged between 1 and 8 years, were evaluated through physical examination, digital ECG (frontaland precordial leads) and thorax X-ray in right lateral (RL), left lateral (LL) and ventrodorsal (VD) projections. Thoracicmorphometry and VHS measurements were determined as previously described. Clinical and ECG parameters were compatible with the references in all dogs evaluated. Dogs presented thorax intermediate (75%) with the depth and width ratio(D/W ratio) > 1.0. Some individual VHS values were higher than the references and the mean VHS values in VD projectionwas higher than in RL and LL projections (n = 20; P < 0.05). Female and male dogs did not differ among the evaluatedparameters. A positive correlation was observed between thoracic morphometry and body weight (r ≥ +0.70; P < 0.001)and a negative correlation was found between the D/W ratio and VD VHS (r = -0.62; P < 0.05). No significant correlationswere observed between the age, ECG parameters, thoracic morphometry and...