A significant proportion of stable outpatients with unexplained chronic dyspnea may have HFPEF. In the patients whom we studied, increased LV stiffness, dyssynchrony, and dynamic mitral regurgitation were the major mechanisms underlying development of HFPEF.

This case describes a middle-aged patient with normal ejection fraction (64%) and significant dyspnoea which could not be explained by results from routine examinations. A pressure-volume loop analysis revealed severe left ventricular (LV) dyssynchrony to be the underlying mechanism of heart failure. The patient underwent implantation of a biventricular pacemaker. Cardiac resynchronization therapy (CRT) was associated with an immediate reduction in LV dyssynchrony from 32 to 13%, decrease in LV end-diastolic pressure from 19 to 8 mmHg, and increased exercise tolerance during follow-up. Thus, CRT may be considered a causal therapy in selected patients with heart failure and preserved ejection fraction.