Electrocardiogram abnormalities in cardiac disorders of dogs

Abstract

In the present study, standard electrocardiogram patterns were worked out from sixty normal dogs. These dogs were grouped according to age groups like dogs below one year and above one year and different breeds like German Shepherd, Dobermann pinscher, Dachshund, Spitz and Mongrel. Based on the clinical signs and electrocardiogram abnormalities, thirteen dogs were grouped into ( 1) dogs with congestive heart failure, (2) dogs with ventricular enlargement secondary to anaemia and (3) dogs with electolyte imbalance due to renal disease. Congestive heart failure was found to be more in geriatric small breeds like Dachshund and Spitz. The clinical signs observed in dogs with CHF were anorexia, cough, exertional dyspnoea, exercise intolerance, orthopnoea, crackles, murmurs, syncope, cachexia and ascites. Clinical signs exhibited by the dogs with ventricular enlargement secondary to anaemia were anorexia, pale visible mucous membranes, weakness and respiratory distress. Dogs with electrolyte imbalance due to renal disease exhibited anorexia, vomiting, diarrhoea, malena, polydipsia, oliguria and anuria. The electrocardiographic signs exhibited by dogs with congestive heart failure were consistent with left atria! enlargement, left and right ventricular enlargement, ventricular tachycardia and right bundle branch block. Dogs in group II had right and left ventricular enlargement as major electrocardiogram abnormality. Dogs in group III with renal disease exhibited tall and peaked ‘T ’ wave and prolonged ‘Q-T- interval in electrocardiogram specifically on the chest leads. The prominent radiographic signs observed in dogs with CHF in the present study were left atrial enlargement, left and right ventricular enlargement and tracheal elevation. Dogs in group II showed left ventricular enlargement, pericardial effusion and tracheal elevation. Group III animals had no radiographic signs of cardiac enlargement. Ultrasonographic evidence of cardiac involvement were present in three dogs, two with CHF and one with ventricular enlargement secondary to anaemia. The findings of postmortem examination of the heart in one dog with CHF were suggestive of mitral valvular insufficiency. Haematology showed no variations in dogs with CHF. Group II and III animals exhibited anaemia evidenced by haematological changes like low TEC, Hb and PCV. Group III animals had neutrophilia with lymphopenia. Group III also had microcytic anaemia.