Modifications of Heart Murmurs and Cardiac Output During Fever

Fever, Heart Murmurs

The combination of fever and auscultation of a heart murmur suggests the diagnosis of endocarditis. However, fever itself increases cardiac output and could therefore modify heart sounds. The aim of the FeMur study is to measure the modification of heart sounds during fever. Heart sounds of 15 hospitalized febrile patients with a heart murmur will be recorded using an electronic stethoscope before and after resolution of fever. The records will be analyzed using a computerized application in order to quantify the intensity of heart murmurs.

Fever is an frequently observed during acute illnesses, particularly infectious diseases. The hemodynamic consequences of fever have been extensively studied. Fever leads to an acceleration of heart rate (approximately 8.5 bpm per degree celsius) and to a moderate drop in blood pressure. Cardiac output increases in the context of heat stress as a result of complex physiological adaptations, including heart rate and systolic function increase while preload and after load decrease. However, there are no studies on the specific consequences of fever on heart sounds. The question is important since auscultation of a heart murmur in a febrile patient suggests the diagnosis of endocarditis. In endocarditis, the heart murmur, which is present in 85% of cases, is due to the mutilation of heart valves, which requires urgent diagnostic and therapeutic management. Suspicion of endocarditis requires emergency cardiac ultrasonography. However, the proportion of patients with actual endocarditis among patients with heart murmur and fever is low. This could arise from the fact that fever itself may increase or trigger a heart murmur. Indeed, any increase in cardiac output may generate audible turbulence when blood is pumped across a heart valve. Functional or inorganic murmurs are murmurs triggered by changes in cardiac output or blood viscosity, as opposed to organic murmurs reflecting an anatomical abnormality in the heart. Certain characteristics of the murmur and the context of occurrence can guide the clinical toward one of these two situations, but distinguishing functional from organic murmurs is most often difficult. The impact of fever on cardiac murmurs has not been experimentally demonstrated. This is the aim of the FeMur study. For this purpose, heart sounds of 15 patients will be recorded during a febrile ilness and after resolution of fever using an electronic stethoscope and analyzed using a computer application. The average intensity of heart murmurs will be compared between the two periods in order to determine the impact of fever.

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