ECG changes in dogs with hypothyroidism.

The results of electrocardiogram (ECG) recordings in 19 dogs with primary hypothyroidism are presented. Low voltage and inverted T waves were the most frequently observed abnormalities. In a number of dogs the ECG changes contributed to the diagnosis of hypothyroidism. A few dogs had even been referred to the cardiopulmonary service because of decreased exercise tolerance and the ECG pointed to the need for thyroid function studies.