The Paradoxic Effect of Tolazoline Hydrochloride on Pulmonary Hypertension of Mitral Stenosis

The administration of 25 mg of tolazoline hydrochloride (Priscoline) into the pulmonary artery of a patient with severe pulmonary hypertension due to mitral stenosis resulted in significant elevation in the pulmonary artery and left atrial pressures, and pulmonary vascular resistance. The elevation in the pulmonary artery pressures and the pulmonary vascular resistance was out of proportion to the increase in the left atrial pressures and the cardiac output. A discussion of the possible mechanism of this paradoxic response is given.