Medical Lecture
Location
Still’s murmur is usually best heard at the lower left sternal border. However, this is not always the case. In some patients, the point of maximal intensity may be closer to the area where the pulmonary flow murmur is best heard. The cervical venous hum is the only innocent murmur that may be best heard above the clavicles.
Radiation
Radiation of Still’s murmur and the cervical venous hum can be minimal. Nonetheless, radiation to the apex of the heart is more suggestive of a Still’s murmur. Radiation to the back or axilla doesn’t occur with those two innocent murmurs and is thus helpful for identifying a pulmonary flow murmur.
Timing
The cervical venous hum is the only one of these innocent murmurs to have a diastolic component.
Configuration
Unlike with Still’s murmur and the pulmonary flow murmur, the systolic component of the cervical venous hum has a plateau configuration.
Quality
The quality of each of these murmurs is different. Still’s murmur can be described as musical or twangy, the pulmonary flow murmur as blowing, and the cervical venous hum as rough or roaring.
Pitch
The pulmonary flow murmur is the only one of these innocent murmurs that as a high-pitch and thus is best heard with the diaphragm of the stethoscope. The other two are better heard with the bell.
Increases Intensity
Hyperkinetic circulatory states increases the intensity of each of these murmurs. However, laying down increases the intensity of Still’s murmur and pulmonary flow murmur, while the opposite, standing up increases the intensity of the cervical venous hum. Furthermore, the cervical venous hum is usually better heard with chin elevation and contralateral rotation of the head (i.e., to the side away from the murmur).
Decreases Intensity
The Valsalva manoeuvre decreases the intensity of all of these murmurs. The intensity of these murmurs can be decreased by performing the opposite of the aforementioned manoeuvres (e.g., standing up for Still’s murmur, laying down for cervical venous hum). However, only the cervical venous hum can be obliterated by applying digital pressure over the internal jugular vein.