Which heart sound is classically associated with pericarditis?

The friction rub is the heart sound that is classically associated with pericarditis. This sound occurs due to the inflammation of the pericardial layers, which leads to roughening of the surfaces. When these inflamed layers rub against each other during the cardiac cycle, a characteristic scratching or grating sound is produced, often described as a "friction rub." It is usually heard best when the patient is in a sitting position and leaning forward, and it can be heard throughout the cardiac cycle.

This sound differs from the other choices, as the S3 gallop is typically associated with heart failure and volume overload, the opening snap is indicative of mitral stenosis, and the mitral click indicates mitral valve prolapse. None of these sounds are specifically related to the inflammation of the pericardium, which makes the friction rub the definitive sound for diagnosing pericarditis. Understanding the distinctions between these heart sounds helps in diagnosing various cardiac conditions effectively.