BACKGROUND AND OBJECTIVES: Although Doppler echocardiography has been used to identify left ventricular (LV) diastolic dysfunction, its limitations suggest there is a need for new biomarkers to measure the diastolic dysfunction. Because the B-type natriuretic peptide (BNP) levels correlate with the LV diastolic pressure, we hypothesized that the BNP would be useful for diagnosing and monitoring the patients with diastolic heart failure. SUBJECTS AND METHODS: We prospectively studied a total of 69 consecutive patients (mean age: 68+/-12 yrs, 31 men and 38 women) who presented to the emergency room with suspected dyspnea of a cardiac origin from November 2003 to May 2004. BNP sampling and Doppler echocardiography were performed for all the study patients. We diagnosed the systolic heart failure (SHF) and diastolic heart failure (DHF) on the conditions that both the clinical and echocardiographic criteria for systolic and diastolic dysfunction were fulfilled. From June 2004 to May 2005, we also performed clinical examinations, measurement of the tissue Doppler derived E/E' and the BNP level at baseline and at 1 year after pharmacologic treatment for 42 consecutive patients who were diagnosed with DHF in the ER and the outpatient clinic. RESULTS: We diagnosed SHF in 37 patients, DHF in 19 patients and we excluded HF in 13 patients (the control group). The mean BNP levels of the SHF and DHF groups were 716+/-532 pg/mL and 390+/-446 pg/mL, respectively, and these values were significantly higher than that of the control group (13+/-14 pg/mL, p<0.01). The area under the receiver-operating characteristic (ROC) curve for BNP to diagnose DHF was 0.94 (95% CI: 0.86 to 1.02, p<0.001). We also compared the BNP levels with the E/E' in terms of the changes of the functional status for the 42 patients suffering with DHF. After treatment, the blood pressure (BP) was significantly decreased from 162+/-26/91+/-15 to 141+/-16/80+/-12 mmHg (p<0.001), the New York Heart Association (NYHA) functional class was decreased from 2.3+/-0.7 to 1.7+/-0.6 (p<0.001), and the E/E' was decreased from 15.9+/-5.7 to 13.8+/-5.1 (p<0.01), but there were no significant changes of the BNP levels, from 213+/-404 to 208+/-464 pg/mL, following treatment. CONCLUSION: A BNP assay is clinically useful for diagnosing DHF, and a cut-off value of BNP can be suggested for screening DHF. However, the tissue doppler derived E/E' is the better index for monitoring changes in the functional status of DHF patients than is the BNP level.