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Does CHF Cause Exudative Pleural Effusions?

In these CHF patients, most exudative effusions had causes other than heart failure.

According to conventional teaching, congestive heart failure causes transudative pleural effusions; nevertheless, we occasionally encounter CHF patients with exudative effusions. Can we assume that CHF is responsible for the exudates in these cases?

In a retrospective study, Oklahoma researchers identified 770 hospitalized patients with CHF and pleural effusions. Thoracenteses were performed in 175 patients: 86 had transudates, and 89 had exudates (classified according to Light's criteria). During hospitalization, non-CHF explanations (e.g., infection, cancer) were found for 59 of the 89 exudates. Among the remaining 30 cases, non-CHF causes became evident in 7 patients during follow-up. Thus, 23 patients had exudative effusions with no identifiable cause other than CHF. Compared to patients with transudates, patients with CHF-related exudates were more likely to have undergone coronary bypass surgery in the remote past, had higher pleural-fluid red blood cell counts (suggesting traumatic thoracenteses), and had received higher doses of diuretics during the week before hospitalization.

Comment: These findings suggest that most, but not all, exudative effusions in CHF patients have causes other than heart failure. The authors believe that, in some cases with no apparent cause other than CHF, transudates might be "converted" into exudates by traumatic taps (which lead to increased pleural-fluid lactate dehydrogenase -- itself a criterion for an exudate) or by aggressive diuresis (which might transiently increase protein and LDL cholesterol concentrations in pleural fluid). In patients with previous bypass surgery, persistent impairment of lymphatic clearance might predispose to exudative effusions.

— Allan S. Brett, MD

Published in Journal Watch General Medicine December 24, 2002

Citation(s):

Eid AA et al. Exudative effusions in congestive heart failure. Chest 2002 Nov; 122:1518-23.

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