The present study attempted to determine the accuracy of B-type natriuretic peptide (BNP) compared with left atrial enlargement at echocardiography in the emergency diagnosis of new-onset heart failure with preserved systolic function (HFPSF) related to longstanding hypertension. The study comprised 57 patients in sinus rhythm hospitalized for acute dyspnea, 30 with hypertensive HFPSF and 27 with noncardiac cause. By stepwise logistic regression analysis, BNP provided independent and incremental diagnostic information over the score of Boston criteria. There was a trend toward superiority of this biomarker compared to the left atrial area index for the diagnosis of HFPSF. A BNP concentration >142 pg/ml was 93% sensitive and 85% specific for the diagnosis of HFPSF in this clinical setting (area under the ROC curve of 0.91 [0.8-0.97], p<0.001).