Optimal Detection of Pericardial Friction Rub in Acute Pericarditis
The pericardial friction rub is best heard with the patient sitting upright and leaning forward during end expiration, ideally with the patient briefly holding their breath after exhaling. 1, 2
Patient Positioning and Breathing Technique
Position the patient sitting upright and leaning forward to bring the heart closer to the anterior chest wall, which optimizes detection of the friction rub 1
Auscultate during end expiration with the patient holding their breath briefly, as this minimizes lung sounds that can obscure the friction rub 2
The optimal auscultation location is typically at the left lower sternal border, though the rub may be audible across multiple precordial areas 1
In some cases, the friction rub may be more pronounced when the patient is in the left lateral decubitus position, though the sitting-leaning-forward position remains the standard approach 1, 3
Clinical Characteristics and Detection Challenges
The pericardial friction rub is highly specific but only audible in approximately one-third of patients with confirmed acute pericarditis, making it an important finding when present but its absence does not exclude the diagnosis 4, 1, 5
The friction rub is characteristically described as a "sandpaper-scratching" sound and can be mono-, bi-, or triphasic in character 1, 3
The rub is often transient and may disappear and reappear during the course of illness, necessitating multiple auscultatory examinations throughout the day 1
Reported detection rates vary widely from 18% to 84% of acute pericarditis cases, reflecting both the transient nature of the finding and variability in examination technique 5
Common Pitfalls to Avoid
Do not exclude pericarditis based solely on the absence of a friction rub, as it is only present in one-third of cases and normal echocardiography does not rule out the diagnosis 4, 6
Perform repeated examinations if initial auscultation is negative, as the rub can be intermittent 1
Remember that pericardial effusion is only detectable in about 60% of acute pericarditis cases, so clinical evaluation remains paramount 4, 6
When a friction rub is detected in the setting of acute myocardial infarction with persistent pain, hypotension, or nausea, urgent echocardiography is indicated to evaluate for complications 1