Objective To determine the prevalence and clinical significance of heart murmurs detected during heart disease screening among apparently healthy schoolchildren.

Design Cross-sectional study.

Setting 32 elementary schools in Dongguan City of China.

Patients 81 213 schoolchildren aged 5–13 years from different elementary schools.

Main outcome measures The prevalence and clinical significance of heart murmurs among schoolchildren.

Results Murmurs were detected in 2193 schoolchildren (2.7%), of whom 215 had a structural heart disease (SHD). Of patients who had SHD, 198 children had congenital heart disease (CHD), 12 had mitral valve prolapse and 5 had rheumatic heart disease. In patients who had CHD, the most common diagnosis was a ventricular septal defect. With respect to sex, SHDs were equally distributed between males and females. Of the schoolchildren who had a murmur, 1797 (81.9%) had a murmur with the loudness of grade 1 or 2 and 396 (18.1%) had a murmur with the loudness of grades 3–6. The prevalence of SHD fell significantly with increasing age.

Conclusions The study suggested that apparently healthy schoolchildren with grade ≤2 cardiac murmurs are least likely to have underlying SHD, especially in those aged ≥10 years. However, echocardiography should be performed in younger schoolchildren with cardiac murmur grade ≥3.