Cardiology Heart Sounds

Pericardial Knock

The pericardial knock is a loud, high pitched sound in early diastole that occurs in patients with constrictive pericarditis. It is the result of rapid deceleration of blood due to the inelastic pericardium. It occurs well outside the range for a split S2, and the opening snap of mitral stenosis, but not as far from S2 as an S3. In patients with suspected constrictive pericarditis, try to identify a constellation of supportive physical findings, including Kussmaul’s sign, Friedreich’s sign, the W sign, and the pericardial knock.
Card Tutorial

Patient 1

An older woman with a history of systemic lupus erythematosus complicated by recurrent episodes of acute pericarditis was admitted to the hospital with dyspnea. She was found to have an extra transient sound just after S2, best heard with the diaphragm of the stethoscope over the apex, consistent with a pericardial knock. She was later diagnosed with constrictive pericarditis.

Audio recording courtesy of BMJ case reports: “Pericardial Knock”

Pericardial Knock

Annotated

Pericardial Knock

Annotated