Figure 3

Venous hum in a 1.7-year-old. Auscultation revealed a systolic-diastolic second-degree murmur that was loudest in early diastole (DM = Diastolic Murmur). Venous hum is sometimes a misleadingly loud murmur. It is caused by flow in the jugular veins under the clavicle into the superior vena cava. This sound is intensified when the head is turned left and disappears when lying supine. The hum is heard best at the right second intercostal space and medially up behind the sternum. The hum is not necessarily heard on every auscultation. The phonogram shows a rather flat contour, and the spectrogram contains 300 Hz and 400 Hz frequencies at the beginning of diastole, when venous return is fastest. Respiratory sounds are also loud in the area of auscultation, which sometimes makes the interpretation of the curves difficult. Age 1.7 years. Auscultation area: right second intercostal space (RIC2). Duration 100 % of systole and diastole, peak frequency 368 Hz and volume 49 %, at the beginning of diastole.