Objectives. The present study was performed to determine the systemic and pulmonary hemodynamic effects of amrinone in infants and children with a cardiac left to right shunt to determine if there is a beneficial effect on the pathophysiology of this condition. Background. Amrinone is a bipyridine derivative with inotropic and vasodilator effects that have not been systematically evaluated in the pediatric patient with increased pulmonary blood flow. Methods. Nineteen patients (aged 2 months to 8.3 years) with one or more left to right shunts were evaluated during cardiac catheterization with direct hemodynamic measurements made before and 10 min (peak effect) after administration of a bolus injection of amrinone, 3 mg/kg body weight. The Fick method was used to calculate pulmonary and systemic blood flow, and resistances were then calculated. Results. In group A, five patients with normal pulmonary artery pressure and resistance, amrinone significantly reduced mean pulmonary artery pressure by 19%, mean left atrial pressure by 39% and systemic vascular resistance by 17%. In group B, seven patients with pulmonary artery hypertension (mean pulmonary artery pressure >20 mm Hg) and normal pulmonary vascular resistance (total pulmonary resistance ≤3 Wood U-m2), amrinone significantly reduced the pulmonary artery pressure by 27%, systolic aortic pressure by 5%, mean aortic pressure by 12%, pulmonary arteriolar resistance by 36% and total pulmonary vascular resistance by 26%. In group C, seven patients with pulmonary artery hypertension (mean pulmonary artery pressure >20 mm Hg) and elevated pulmonary vascular resistance (total pulmonary resistance >3 Wood U·m2), amrinone significantly reduced the pulmonary arteriolar resistance by 49%, total pulmonary resistance by 47% and pulmonary arteriolar/systemic vascular resistance ratio by 45% and increased the heart rate by 15%. Conclusions. In children with a cardiac left to right shunt, amrinone 1) appears to have selective vasodilator effects depending on the pulmonary artery pressure and resistance, 2) has a beneficial hemodynamic effect in children with normal pulmonary artery pressure and resistance, and 3) may have a role in the treatment of patients with pulmonary artery hypertension without causing systemic hypotension.
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