Introduction
This topic covers the pericardial friction rub, the most important extracardial sound heard over the precordium, and the other non-cardiac sounds that students must not confuse with heart murmurs. A good answer explains the mechanism of the rub, its causes and clinical picture, how it is separated from a pleural rub, and how the underlying condition is managed.
Pericardial friction rub: definition and mechanism
A pericardial friction rub is a superficial, scratching or creaking sound produced when two inflamed pericardial layers, the visceral and parietal pericardium, rub against each other during the cardiac cycle. Roughened, fibrin-covered surfaces move over each other with every heartbeat, so the sound is not a turbulent flow sound like a murmur but a mechanical contact sound.
- Usually has up to three components: systolic (ventricular contraction), early diastolic (rapid ventricular filling) and late diastolic (atrial contraction), though one or two may be audible.
- Best heard at the left sternal border in the third and fourth intercostal spaces, with the patient sitting up and leaning forward and at end-expiration.
- Is characteristically superficial, leathery or creaking, and it may be louder with light pressure of the diaphragm of the stethoscope.
- Is not changed by breath-holding, which is the key feature that separates it from a pleural rub.