Purpose: To determine the prevalence of innocent murmur among adolescents, and to evaluate the clinical features in comparison with echocardiogram (two-dimensional, M-mode, Doppler, and color-Doppler) in the assessment of heart murmurs.
Methods: The study was carried out from March to December, 1992, and involved high school students coming from families of the medium and low-medium social classes. Considering the total of 1400 students registered in a public school, 536 adolescents aging from 10 to 20 years were admitted in this study. Twenty seven students with heart murmur were submitted to Echocardiography in order to find any cardiac lesions.
Results: Among 536 adolescents, 171 (32%) had some kind of heart murmur. On the basis of the clinical diagnosis, 160 (29.9%) patients were classified as having innocent murmur and 11 (2.1%) as having "pathologic murmur". Out of 27 students submitted to echocardiography, 20 of them with clinical diagnosis of innocent murmur showed normal results. Among seven students with clinical diagnosis of "pathologic murmur", the echocardiography recognized cardiac lesions in two (small ventricular septal defect and rheumatic heart disease: combined mitral incompetence and stenosis, and aortic incompetence).
Conclusion: From the data obtained, the prevalence of innocent murmur among adolescents was 29.9% on the basis of clinical diagnosis. It is suggested that careful clinical examination by physicians skilled in cardiac examination is the recommended method for the diagnosis of innocent murmur (sensitivity of 100% and specificity of 80%).