Characteristics Of Pericardial Friction Rub In Acute Pericarditis

Acute pericarditis is often accompanied by a distinct clinical sign known as the pericardial friction rub. This sound provides important diagnostic clues and has several unique characteristics that set it apart from other cardiac sounds.

Timing And Positioning

The pericardial friction rub typically appears during the early stages of acute pericarditis. Its presence can vary depending on the patient's position. It is most clearly heard when the patient is sitting upright and leaning slightly forward. This posture brings the heart closer to the chest wall, making the sound more audible. The optimal location to detect this rub is at the left sternal border, specifically between the third and fourth ribs.

Presence Throughout The Cardiac Cycle

One of the defining features of the pericardial friction rub is its occurrence throughout the entire cardiac cycle. This means it can be detected during both systole (when the heart contracts) and diastole (when the heart relaxes). The continuous nature of this sound helps distinguish it from other types of heart murmurs that may be limited to a specific phase of the heartbeat.

Underlying Cause

The sound is produced due to inflammation of the pericardium, which causes the visceral and parietal layers of the pericardium to become roughened. In the early phase of acute pericarditis, these layers exude a significant amount of fibrin, reducing their natural smoothness. As the heart beats, these rough surfaces rub against each other, creating a distinctive scratching or grating sound. In some cases, this friction can even be felt by a physician during physical examination, adding a tactile component to the diagnosis.