A 10-month-old intact female mixed breed dog was referred for evaluation of exercise-induced dyspnea and a low grade II/VI systolic murmur was detected. The communication between ascending aortic and pulmonary trunk was observed by detecting a continuous flow just above the semilunar valves on echoDopplercardiography and attested by surgery. After the surgical procedure, the dog was presented in good clinical conditions without exercise-induced dyspnea, reflecting the importance of an early and accurate diagnostic for the therapeutic success. This is the first Brazilian report of this rare congenital disease and the unique well succeed surgery in the veterinary literature.Keywords: dog, aorticopulmonary window, aorticopulmonary fenestration RESUMO Na avaliação da dispneia pós-exercício em uma cadela de 10 meses de idade, não castrada e sem raça definida, foi detectado sopro sistólico leve grau II/VI. A comunicação entre a aorta ascendente e o tronco pulmonar, observada pela presença de fluxo contínuo logo abaixo das valvas semilunares

In the present protocol, adult dogs were infected with Trypanosoma cruzi, Bolivian strain, in order to show electrocardiographic changes by means of resting and dynamic (Holter) methods during acute and chronic phases of Chagas disease. In the acute phase there were sinus tachycardia, atrial and left ventricular overload, millivoltage suppression, electric alternance, and episodes of sinus arrest. At the parasitemia peak, atrium-ventricular block, junctional escape complexes, and atrium-ventricular dissociation were observed. Dogs that presented the most serious arrhythmias died suddenly. The increase in supraventricular and ventricular arrhythmic events, concentrated in the 4th postinoculation week, was visible at electrocardiographic monitoring. In the chronic phase, the events were restricted to first-degree atrium-ventricular blocks, premature ventricular complexes, ventricular bigeminy, and electrical alternation. It was concluded that the computerized and dynamic electrocardiography allowed to diagnose transient arrhythmia and to observe that the main tachyarrhythmic changes are concentrated at the acute phase concomitantly to the parasitemia peak.