Unilateral Pulmonary Edema

Abstract & Commentary

By Michael H. Crawford, MD

Source: Attias D, et al. Prevalence, characteristics, and outcomes of patients presenting with cardiogenic unilateral pulmonary edema. Circulation. 2010;122:1109-1115.

Cardiogenic unilateral pulmonary edema is unusual and, if it is the presenting manifestation of heart failure, diagnosis and appropriate treatment may be delayed. Thus, these investigators from France reviewed 869 cases of cardiogenic pulmonary edema admitted over eight years to assess the prevalence and clinical features of unilateral pulmonary edema. Echocardiograms were obtained within 48 hours in 96% of the patients.

Results: Bilateral edema was present in 851 (98%) and unilateral in 18 (2%). Severe mitral regurgitation (MR) was found in 71 (8%). Unilateral edema was right-sided in most (89%). All patients with unilateral edema had severe MR, and the radiological location of the edema in the lungs was related to the direction of the MR jet. Only 6% of the patients with bilateral edema had severe MR. A murmur was heard in about two-thirds of patients with severe MR, but it was more likely in those with organic MR (83%) vs. functional MR (43%). Delay in treatment (> 6 hours from presentation) was more common in unilateral edema as compared to bilateral edema patients (33 vs. 4%, p < 0.003). Total in-hospital mortality was 9%, and was higher in those with unilateral edema as compared to bilateral edema (39% vs. 8%, OR 6.9, 95% CI 2.6-18, p < 0.001). Multivariate analysis for clinical factors associated with death showed that unilateral edema was the most predictive variable. The authors concluded that unilateral pulmonary edema is infrequent (2% of pulmonary edema cases), usually involves the right lung, and is almost always associated with acute severe MR. The presence of unilateral edema delays treatment and is associated with greater mortality.


Unilateral pulmonary edema in this series was unusual (2% of cardiac pulmonary edema), but was always associated with severe mitral regurgitation (MR). Among their patients presenting with pulmonary edema due to severe MR, unilateral edema was seen in 25%. Their series demonstrates that the diagnosis of cardiac edema was often delayed when unilateral edema was present. In fact, pneumonia was often suspected, and 61% were treated with antibiotics even though only 11% had fever. Unfortunately, you cannot rely on the presence of a murmur to help you arrive at the correct diagnosis. Although over 80% of those with organic MR had murmurs, less than half of those with functional murmurs did. Also, an elevated leukocyte count was frequent (72%) in those with unilateral edema. Thus, if you suspect a cardiac cause, an echocardiogram should be done.

Echocardiography suggested that unilateral edema is due to the regurgitant jet preferentially impacting the pulmonary veins from one lung. Prior invasive studies of patients with severe MR and eccentric jets have confirmed that pulmonary capillary wedge pressures can be higher in one lung vs. the other. Interestingly, involvement of the right lung is more common perhaps because the more common posterior leaflet prolapse usually directs the MR jet toward the right pulmonary veins. Anterior leaflet prolapse often is directed toward the left pulmonary veins. Whether the observed increase in mortality in patients with unilateral edema is due to the delay in diagnosis is unclear. In this series, these patients had lower blood pressures and were more likely to be on mechanical ventilation and pressors. Also, all patients with unilateral edema had severe MR, whereas only 6% of those with bilateral edema did. Thus, it appears that delaying the diagnosis of severe MR is detrimental to survival.