THE REVERSIBILITY OF PULMONARY HYPERTENSION IN PATIENTS WITH CYSTIC FIBROSIS

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Abstract
1. The present study was concerned with the evaluation of the acute and chronic effects of tolazoline, O2, and sleep on the pulmonary circulation of six subjects with cystic fibrosis and pulmonary hypertension. 2. Right heart catheterization was performed and observations were made at rest, after tolazoline and after O2. In four subjects, changes in pulmonary artery pressure (PAP) induced by various agents and sleep were observed for periods ranging from 3 hours to 4 days. 3. Resting mean PAP ranged from 22 to 67 mm Hg; arterial PO2 from 37 to 47 mm Hg; pH from 7.252 to 7.408, cardiac index from 2.64 to 3.91 1/min/m2, and total pulmonary resistance (TPR) from 440 to 1,330 dynes sec cm-5-m2. 4. Following tolazoline, the average mean PAP dropped from 51 to 28 mm Hg, average cardiac output rose from 3.20 to 4.08 1/min/m2; TPR dropped from 880 to normal. This decrease in PAP and TPR was achieved with little change in either pH or arterial pO2. 5. The addition of O2 to tolazoline lowered the mean PAP further by 8 mm Hg. 6. Observations were made during sleep in three of the patients. In each, there was an increase in PAP ranging from 9 to 23 mm Hg. 7. Repeated administration of tolazoline resulted both in progressively lower PAP and less tendency for its return to control level. 8. Postmortem pulmonary arteriograms and histological examination of the pulmonary vessels were performed in one patient. Despite the presence of numerous abscesses and diffuse bronchopneumonia, the pulmonary vessel was found to be relatively normal. Only medial hypertrophy of the small arterioles was seen. 9. The factors involved in the development of hypoxic pulmonary hypertension and possible mechanisms by which tolazoline effects acute and sustained reduction of PAP are discussed. 10. It is concluded that acute and repetitive pharmacologic treatment is effective in the reduction of pulmonary hypertension in patients with cystic fibrosis. Further, it is suggested that patients with cystic fibrosis and reactive pulmonary hypertension would benefit from residing at sea level.

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