Background: We have found that there are usually 2 causes of acute dyspnea in our emergency department: (1) pulmonary infection only and (2) pulmonary infection in the setting of acute left ventricular heart failure (LVHF). These conditions are sometimes difficult to differentiate. Lung ultrasonography (LUS) is easily performed at the bedside and provides accurate information for diagnosis. In this study, we propose a simple B-line score to allow rapid differential diagnosis between these 2 lung conditions. Methods: A prospective, single-blind trial was conducted on 98 patients with acute dyspnea in the emergency department. Lung ultrasonography and transthoracic echocardiography were performed within 30 minutes after enrollment. The final clinical diagnosis was recorded for all patients. Using the Bedside Lung Ultrasound in Emergency protocol, we recorded the number of B lines at 4 standardized points. Based on the theory of Lichtenstein, scores of 1, 2, 3, and 4 were categorized by the number of B lines on a static screen (0 to <3, 3 to <6, 6 to <8, and >= 8, respectively). The B-line score of 4 Bedside Lung Ultrasound in Emergency protocol points was recorded, and the total B-line score was calculated. Receiver operating characteristic (ROC) curves were used to evaluate the accuracy of the rapid ultrasound measurements for the final clinical diagnosis. Results: In our study, 27 patients were diagnosed with pulmonary infection and acute LVHF. The total number of B lines and the B-line score in patients with pulmonary infection in the setting of acute LVHF were 24.2 +/- 2.5 and 11.5 +/- 1.5, respectively, which were significantly higher than those in patients with pulmonary infection (12.5 +/- 6.4 and 7.2 +/- 1.9) (P =.000). In patients with pulmonary infection and acute LVHF, the effective diagnostic value of left ventricular ejection fraction and the total B-line score were similar (area under the ROC curve: 0.986 vs 0.962, P=.2607). The cutoff value of the total B-line score was 8, with a sensitivity of 80.7% and a specificity of 100%. A combination of LUS and echocardiography might improve the diagnostic accuracy (area under the ROC curve: 0.994; 95% confidence interval, 0.981-1.000; P =.000). Conclusions: This simple B-line score with LUS can help make a rapid differential diagnosis between pulmonary infection and pulmonary infection with acute LVHF. The diagnostic accuracy may be enhanced when used in conjunction with echocardiography. (C) 2015 Elsevier Inc. All rights reserved.