Acute heart failure due to Q fever endocarditis.

We report a case of Q fever endocarditis in a patient who presented with a slight pyrexia and acute cardiac failure due to aortic incompetence. The diagnosis was made by detecting high titres of serum IgG and IgA antibody against Coxiella burnetii phase I antigens and confirmed by demonstrating C. burnetii on the excised aortic valve using immunofluorescence and electron microscopy. Aortic valve replacement was followed by initially successful antibiotic treatment for 15 months. Reappearance of IgA anti-phase I antibodies 5 months later suggested continued presence of bacteria, although the patient's condition remained satisfactory. In endemic areas, such as rural southern France, Q fever endocarditis should be considered when there is evidence of acute heart valve damage but are few other features of infection.