This paper describes the occurrence of cor triatriatum sinister, a rare cardiac malformation in dogs, associated with pulmonary edema and pulmonary hypertension in a 5-year-old Poodle female with history of acute dyspnea and cyanosis. The animal presented acute respiratory failure, heart failure with low cardiac output, progressing to acute tubular necrosis and death. The diagnosis was made posmortem due to the clinical instability of the dog. This malformation was diagnosed by the subdivision of the left atrium into two compartments separated by an abnormal fibromuscular membrane, absence of structural abnormalities of the mitral valve and thickening of pulmonary artery tunica media associated with renal tubular degeneration. The occurrence of cor triatriatum in dogs is most common in the right atrium, defined as cor triatriatum dexter. Additionally, pulmonary arterial hypertension associated with this malformation is described only in humans with this heart defect.

Estudaram-se os parâmetros eletrocardiográficos utilizando-se os métodos convencional, computadorizado e computadorizado impresso de 30 cães da raça Beagle clinicamente normais. As medidas eletrocardiográficas dos três diferentes traçados foram analisadas na derivação DII. A comparação entre os métodos revelou diferença nos valores da onda P, onda R, complexo QRS, intervalo QT e intervalo PR e na polaridade da onda T. Este fato deve ser levado em consideração, na dependência do método a ser utilizado.

Electrocardiographic parameters were studied in thirty healthy adult Beagles, using conventional and computerized methods and reading the computerized registration printed on paper. The electrocardiographic measurements of the three different tracings were analyzed in lead II. The results obtained showed that there are differences among the three methods for P wave, R wave, QRS complex, QT interval, PR interval and polarity of the T wave. Special attention should be given to these differences, depending on the chosen method.