Pericardial knock

Pericardial knock – is a high-pitched early diastolic sound

What is the Mechanism of pericardial knock?

Mechanism of pericardial knock – high-pitched, early diastolic sound that occurs when unyielding pericardium results in sudden arrest of ventricular filling.

Pericardial knock can be an important clue to the diagnosis of constrictive pericarditis.

Pericardial knock – corresponds in timing to the

  1. abrupt cessation of ventricular expansion after AV valve opening
  2. prominent y descent seen in the jugular venous waveform in patients with constrictive pericarditis

How to differentiate pericardial Knock from S3?

  1. S3 is a low-pitched sound
  2. LV S3 – best heard over the LV apex with the patient in the left lateral decubitus position,
  3. RV S3 – best heard at the lower left sternal border or in the subxiphoid position with the patient supine and become louder with inspiration.
  4. Pericardial knock occurs earlier than an S3 heart sound which is the distinguishing factor
  5. S3 heart sound occurs from stretch of a very compliant left ventricle which takes a short time longer than Pericardial Knock.
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