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.
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
Patient 2:
A middle-aged woman was admitted to the hospital with exertion dyspnea six months after an episode of acute pericarditis caused by anterior chest wall trauma related to a boogie boarding accident. She was found to have a pericardial knock on examination, as well as other evidence of constrictive pericarditis.
Pericardial Knock
Annotated
Pericardial Knock
Patient 3:
This is an older woman with Hodgkin’s lymphoma and breast cancer who had radiation therapy to chest and later developed valvular heart disease. We suspect that she may have constrictive pericarditis. This extra sound is heard just after S2, and is best appreciated with the diaphragm of the stethoscope along the left sternal border. It could also be a split S2. However, arguing against the split S2 is the fact that the extra sound is not heard in the aortic area (would expect a split S2 over that area) and the sounds are heard a bit too far apart.