BACKGROUND Nesiritide is recombinant human B-type natriuretic peptide with vasodilatory effects used in patients with decompensated congestive heart failure. We sought to evaluate the effects of nesiritide on left ventricular diastolic function in heart failure patients. RESULTS Twenty-five heart failure patients underwent left heart catheterization (using a pressure-volume conductance catheter) and echocardiography at baseline and 30 minutes after an intravenous bolus and infusion of nesiritide. Invasive and noninvasive measurements of load-dependent (deceleration time, echocardiographic diastolic function classification, negative dP/dt, left ventricular diastolic pressure, tau) parameters of diastolic function were assessed. The nonlinear slope of the end-diastolic pressure volume relationship (EDPVR) using 2 single-beat methods for measuring left ventricular end-diastolic elastance was calculated to assess load-independent parameters of diastolic function. Nesiritide reduced biventricular diastolic pressure and systemic vascular resistance. Tau and negative dP/dt showed modest improvement. Deceleration time, isovolumetric relaxation time, diastolic stiffness indices (E/E'/stroke volume (SV) and E/E'/left ventricular end-diastolic volume index (LVEDVI)), and the echocardiographic diastolic filling pattern classification did not change. Furthermore, there was no change in the EDPVR. CONCLUSIONS Although nesiritide is an effective vasodilator resulting in decreased left ventricular preload and afterload in heart failure patients, intrinsic left ventricular diastolic function did not change acutely, suggesting that nesiritide has no significant acute lusitropic effect.