RESOLUTION OF VASCULAR STEAL AFTER PULMONARY THROMBOENDARTERECTOMY

Patients who undergo thromboendarterectomy for relief of chronic, majo r-vessel thromboembolic pulmonary hypertension (CT-E PH) offer a uniqu e opportunity to evaluate potential resolution of hypertensive lesions in the small, nonelastic pulmonary arteries. Prior studies have demon strated that, postoperatively, these patients commonly develop new per fusion scan defects. This ''vascular steal'' phenomenon occurs almost exclusively in lung segments which, preoperatively, were normally perf used by lung scan, were served by segmental arteries normal by pulmona ry angiography, and, at surgery, were uninvolved with thrombi by direc t inspection. In this study, we explored whether this intriguing ''ste al'' phenomenon resolves over time. Twenty-nine patients who returned at 11 or more months following thromboendarterectomy were reevaluated by perfusion lung scan, repeated right heart catheterization (26 patie nts), and pulmonary angiography (25 patients). ''Steal'' of one or mor e lung segments occurred in 79 percent of patients in postoperative, p redischarge perfusion scans. All demonstrated postoperative improvemen t in pulmonary hemodynamics, which persisted at follow-up. Postoperati ve ''steal'' improved in 96 percent of patients and 86 percent of the ''stolen'' segments. The results suggest that, in CT-E PH, hypertensiv e lesions in the small, nonelastic pulmonary arteries are responsible for ''steal,'' and that, with relief of pulmonary hypertension, these lesions can resolve. The study also indicates that postoperative ''ste al'' does not connote either new thromboembolic events or a poor hemod ynamic result.