Mechanism of Pleural Effusion in Heart Failure: The Role of Diastolic Dysfunction and Misconception of Systolic Function

Pleural effusions are common in patients with congestive heart failure. This process is felt to be due to left ventricular (LV) dysfunction leading to elevated pulmonary venous and left atrial pressures. However, the pathogenesis of LV dysfunction is not well understood. Although poor left ventricular ejection fraction (LVEF) has been implicated in the development of pleural effusions, other parameters such as diastolic dysfunction have not been systematically investigated. In this study, we analyzed the association between LVEF, mitral early (E) to late (A) filling (E/A ratio), and presence of pleural effusion. ICD-9 codes were used to identify patients with congestive heart failure (CHF). At enrollment, all patients simultaneously underwent a chest CT scan and transthoracic echocardiogram. Patients with pleural effusions from non-cardiac causes were excluded. The control group comprised of patients with heart failure without pleural effusions. A trained cardiologist and radiologist blinded to patient information interpreted the echocardiograms and CT findings. E/A ratio, a measure of diastolic dysfunction, assessed by the flow across the mitral valve during early rapid filling (E) and flow across the mitral valve during atrial contraction (A) was calculated. Age, BMI, and echocardiographic measurements were included in the model as covariates with the outcome variable being the presence of pleural effusion. A stepwise logistic regression analysis was used to estimate this association. Nagelkerke R-value assessed the model strength. Of the 70 patients, 47% (33) were female and 53% (37) were male, with a mean age of 57 ± 15 years. 5% of the pleural effusions were left sided, 28% were right sided, and 67% were bilateral. The mean E/A ratio in patients with effusions (2.53 ± 1.1) were significantly higher than in patients without effusions (1.15 ± 0.9), P < .01. Multiple logistic regression analysis identified an elevated E/A ratio as an independent predictor (P < .01) for the development of pleural effusions in CHF. Left ventricular ejection fraction (LVEF), baseline labs, age, and BMI were not significantly associated with the presence of pleural effusions. Additionally, patients with CHF related pleural effusions were noted to have a higher overall mean LVEF. Patients with elevated E/A ratio are more likely to develop pleural effusions than patients with a normal E/A ratio. Systolic function does not seem to play a role in pleural effusion formation. Further studies as required to validate these results and determine the prognostic significance of this ratio in patients with heart failure.