Left ventricular dysfunction in Rocky Mountain spotted fever.

Rocky Mountain spotted fever is a serious infectious disease that continues to occur with increasing incidence in various areas of the United States. A high case-fatality ratio (11%) persists in spite of availability of adequate chemotherapeutic agents, and the cardiac involvement may play an important role in the final outcome of some cases. To assess the effect of the disease on left ventricular function 13 patients underwent M-mode echocardiographic examination on admission to a children's hospital. Increased left ventricular dimension was found in 3 patients and decreased left ventricular shortening fraction in 9. Diminished mean velocity of circumferential fiber shortening and increased left ventricular systolic time interval ratios were found in 8 patients and increased mitral valve E point to ventricular septal separation in 9. One patient died and biventricular dilatation with diffuse myocarditis was seen at autopsy. Repeat echo examination was available in 11 patients at follow-up (mean 5 months). Abnormal E mitral point to ventricular septal separation remained in 4 patients and decreased left ventricular shortening fraction in 2. The long-term prognosis for this group is unknown. Myocardial involvement is frequently present in Rocky Mountain spotted fever; close monitoring and aggressive therapeutic approach are essential if the high case-fatality ratio is to be reduced.