[Incidence of innocuous thoracic murmurs in a sample of 12,009 students]. / Incidencia de soplos inocentes toracicos en una muestra de 12,009 escolares.

We have studied a total of 12,009 school children (age range 6 to 14 years) in order to determine the incidence of thoracic innocent murmurs. 6,816 were male and 5,193 female. A initial clinical evaluation was carried out in the school and the second examination was performed in our hospital. Global incidence of innocent murmurs was 9.57% with a female/male ratio of 1.73. We divided the innocent murmurs according with Fishleder's method: mesocardial systolic murmur (62%), pulmonary systolic murmur (26%), protosystolic apical murmur (7%), "whooping" murmur (5%). Afterwards, children with murmurs were divided in two groups of age and anthropometric characteristics observing a significative increment in the incidence of mesocardial systolic murmur in children which ranged ages from 6 to 10 years (74%) and of the pulmonary systolic murmur in the group of 10 to 14 years (40%).