Pericardial knock

Abstract

Correspondence to Dr André Martin Mansoor; [email protected] Description A 69-year-old woman with a history of systemic lupus erythematosus complicated by recurrent episodes of acute pericarditis was admitted to the hospital with chronic, progressive dyspnoea. The qualities of the extra sound, including pitch, timing and location, were consistent with that of a pericardial knock. A pericardial knock can be difficult to distinguish from an S3 gallop; it is a high-pitched, diastolic sound heard 0.09 to 0.12 s after the aortic component of S2 (A2).1–3 It tends to be louder, higher-pitched, and slightly closer to A2 than the low-pitched S3 gallop, which occurs 0.1 to 0.2 s after A2.2 3 The sound is presumed to occur when stiff and thickened pericardium cause sudden arrest of ventricular filling during diastole.2 3 Learning points The pericardial knock is a high-pitched, early diastolic sound that occurs when unyielding pericardium results in sudden arrest of ventricular filling.

Correspondence to Dr André Martin Mansoor; [email protected]

Description

A 69-year-old woman with a history of systemic lupus erythematosus complicated by recurrent episodes of acute pericarditis was admitted to the hospital with chronic, progressive dyspnoea. Physical examination was notable for a jugular venous pressure (JVP) of 18 cm H₂O, with paradoxical rise on inspiration (Kussmaul’s sign). The y descent of the jugular venous waveform was observed to be sharp and deep (Friedreich’s sign). Coinciding with the nadir of the y descent, an extra, early diastolic heart sound was heard over the apex. It occurred just after the second heart sound (S2) and was high-pitched, heard best with the diaphragm of the stethoscope. A digital stethoscope was used to record the heart sounds. Simultaneously, an antique phonocardiograph was used to produce visualisation of the sounds in the form of a phonocardiogram. Combining these results, a video was created for analytic and teaching purposes (video 1). The qualities of the extra sound, including pitch, timing and location, were consistent with that of a pericardial knock. In a patient with a history of recurrent episodes of acute pericarditis, the constellation of elevated JVP, Kussmaul’s sign, Friedreich’s sign, and a pericardial knock led to the diagnosis of constrictive pericarditis. A pericardial knock can be difficult to distinguish from an S3 gallop; it is a high-pitched, diastolic sound heard 0.09 to 0.12 s after the aortic component of S2 (A2).^1–3 It tends to be louder, higher-pitched, and slightly closer to A2 than the low-pitched S3 gallop, which occurs 0.1 to 0.2 s after A2.^{2 3} The sound is presumed to occur when stiff and thickened pericardium cause sudden arrest of ventricular filling during diastole.^{2 3}

Learning points

• The pericardial knock is a high-pitched, early diastolic sound that occurs when unyielding pericardium results in sudden arrest of ventricular filling. It can be an important clue to the diagnosis of constrictive pericarditis.^{2 3}

• The pericardial knock occurs earlier in diastole (0.09–0.12 s after the aortic component of the second heart sound (A2)) compared with the S3 gallop (0.1–0.2 s after A2).^1–3

• Phonocardiography combined with modern digital recording devices can be used to facilitate the understanding and recognition of extra heart sounds.

Footnote

Contributors AMM captured the audio and phonocardiographic tracing of the heart sounds. TEB created the synchronised video. TEB, NNL, GSO, PDS, and AMM were involved in writing the manuscript.

Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

Competing interests None declared.

Patient consent for publication Obtained.

Provenance and peer review Not commissioned; externally peer reviewed.

References

¹ Wood P. Chronic constrictive pericarditis. Am J Cardiol 1961; 7: 48–61. doi:10.1016/0002-9149(61)90422-2

² Marriott HJL. Bedside cardiac diagnosis. Philadelphia, PA: Lippincott Company, 1993.

³ Tavel ME. Clinical phonocardiography and external pulse recording. 2nd edn. Chicago, Illinois: Year Book Medical Publishers, Inc, 1967.