INDUCED RIGHT-TO-LEFT CARDIAC SHUNT DURING PULMONARY PERFUSION IMAGING

Ventilation-perfusion lung scans are routinely performed using Tc-99m labeled MAA particles administered intravenously which are subsequentl y trapped in the pulmonary artery capillary bed. In the presence of a right-to-left shunt, activity may be seen in the systemic circulation. Right-to-left shunts may be worsened by inducing hypoxemia which caus es pulmonary artery constriction, and also by increasing venous return to the heart. In this case, the authors used various maneuvers to inc rease right-to-left shunting and thereby demonstrated the presence of fixed pulmonary hypertension. These findings suggested that the patien t's dyspnea on exertion was not primarily because of left ventricular dysfunction, and proposed coronary bypass surgery was deferred for med ical management.