LUNG PERFUSION SCANS AND HEMODYNAMICS IN ACUTE AND CHRONIC PULMONARY-EMBOLISM

To assess the relationship between pulmonary vascular obstruction and hemodynamic status in acute pulmonary embolism (APE) and in chronic th romboembolic pulmonary hypertension (CTEPH), perfusion lung scan and h emodynamic measurements were obtained in 31 consecutive patients with APE and in 45 with CTEPH. Methods: Lung scans were scored independentl y by two experienced observers who determined the percentage of vascul ar obstruction (PVOs). Mean pulmonary artery pressure (PAF) and total pulmonary resistance (TPR) were obtained during right heart catheteriz ation. In patients with APE, measurements were recorded within a 1-hr interval before and 12 hours after thrombolysis. This yielded 62 paire d PVOs values with concomitant PAP and TPR measurements. In patients w ith CTEPH, data were recorded within a 3-day interval. Results: Mean P VOs (%) values were similar in APE and CTEPH patients (59 +/- 13 vs. 5 8 +/- 15), whereas PAP and TPR were significantly higher in CTEPH pati ents (51 +/- 17 mmHg and 23 +/- 11 U/m(2), respectively) than in APE p atients (23 +/- 8 mmHg and 9 +/- 5 U/m(2), respectively, p < 0.001). I n APE patients, significant hyperbolic correlations were found linking PVOs with PAP and TPR (r = 0.75, p < 0.01 for PAP; r = 0.71, p < 0.01 for TPR). In CTEPH, there were no significant correlations between PV Os and PAP or TPR. For the same level of PVOs, patients with CTEPH had higher PAP and TPR values than patients with APE. Conclusion: In APE without prior cardiopulmonary disease, increases in PAP and TPR are co rrelated in a nonlinear fashion with the degree of pulmonary vascular obstruction as assessed by lung scanning. In CTEPH patients, the highe r PAP and TPR values as compared to APE patients with comparable degre es of PVOs are consistent with previous reports that pulmonary hyperte nsion in CTEPH is due not only to the obstruction of proximal pulmonar y arteries but also to remodeling of small distal arteries in nonocclu ded areas.