pericardial friction rub

A pericardial friction rub is the scratchy, grating sound a doctor hears through the stethoscope when inflamed pericardial surfaces rub against each other as the heart moves. The sound is often likened to creaking leather or walking on dry, crunchy snow.

Classically it has up to three components within each heartbeat, reflecting the moments when the heart moves most against the sac: during atrial contraction, during ventricular contraction, and during early ventricular filling. The rub is typically loudest at the lower left edge of the breastbone, and it can get louder when the patient leans forward and holds their breath after breathing out.

A friction rub is one of the most specific signs of pericarditis, so hearing one strongly supports that diagnosis. However, it can be intermittent and is easy to miss, so its absence does not rule pericarditis out. As fluid accumulates in a pericardial effusion, the surfaces are separated and the rub may fade.