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.