Prevalence of symptomatic large pleural effusions first diagnosed more than 30 days after coronary artery bypass graft surgery.

Background And Objective: Symptomatic large pleural effusions (>25% of hemithorax) are sometimes diagnosed after coronary artery bypass graft surgery (CABG). Their incidence and outcome have not been fully described. This study aims to discuss the prevalence and the clinical course in patients diagnosed with symptomatic newly developed large pleural effusions at least 30 days after CABG.

Methods: A retrospective study of 410 patients who underwent CABG over a three and a half year period was undertaken. The type of surgery, timing of occurrence of effusion after CABG, amount and characteristics of the pleural effusion, left ventricular dimension and ejection fraction were obtained from medical records and cardiac surgery databases.

Results: The records of 356 patients 1 month post CABG were available for evaluation. The initial diagnosis of a newly developed symptomatic large pleural effusions was made in 11 patients (3.1%) at least 30 days after CABG. Eight had a pleural effusion predominantly on the left side and three on the right. Patients were further divided into two groups: those who had effusions diagnosed between 30 and 90 days post CABG (group 1) and those diagnosed more than 90 days post-CABG (group 2). The pleural fluid LDH levels were higher in patients in group 1 (1262.0 +/- 921.3 U/L vs. 117.5 +/- 35.1 U/L, P = 0.02). Patients in group 2 had evidence of cardiac impairment compared with those in group 1, as evidenced by a lower ejection fraction (68.8 +/- 6.0% vs. 52.0 +/- 10.6% in groups 1 and 2, respectively, P = 0.01) and higher left ventricular end-diastolic dimension (45.2 +/- 6.0 mm vs. 55.3 +/- 8.4 mm in groups 1 and 2, respectively, P = 0.05).

Conclusions: The incidence of symptomatic newly developed large pleural effusions first diagnosed at more than 30 days post CABG was 3.1%. Those who were diagnosed between 30 and 90 days post CABG tended to have exudative effusions, whereas those diagnosed more than 90 days post CABG often had left ventricular impairment and transudative effusions. Most of these effusions settled with conservative management and did not recur.