Severe Pulmonary Stenosis and Bidirectional Shunting Muscular Ventricular Septum Defect in a Dog

Abstract

A 4-year-old border collie dog with syncope was refered. Arterial oxygen saturation measured by pulse oximeter was low, and echocardiograph revealed pulmonary stenosis and bidirectional shunting muscular ventricular septum defect (VSD). As flow velocity of pulmonary artery was 5.3 m/sec with concentric hypertrophy of right ventricular and right-to-left shunting VSD in systole, we diagnosed pulmonary stenosis was severe, so performed surgical relief of pulmonary stenosis under the cardiopulmonary bypass. Postoperatively, although flow velocity of pulmonary artery was high, we suggested that surgical relief of pulmonary stenosis was effective for improving hemodynamics because of disappearance of syncope, improvement of arterial oxygen saturation, left-to-right shunting VSD in systole due to reversal of pressure gradient between right and left ventricular. Because Qp/Qs was 1.35, we speculated that increasing of shunt blood was responsible for high velocity of pulmonary artery.