When is the pericardial friction rub best heard?

When the Pericardial Friction Rub is Best Heard

The pericardial friction rub is best heard with the patient sitting upright and leaning forward while briefly holding their breath, using the diaphragm of the stethoscope at the left lower sternal border. 1

Optimal Patient Positioning

• The sitting, leaning forward position brings the heart closer to the anterior chest wall and minimizes interfering lung sounds, making the friction rub more audible 1
• Having the patient briefly hold their breath during auscultation further eliminates respiratory sounds that can obscure the rub 1
• While the sitting-leaning-forward position is generally optimal, the friction rub can occasionally be more pronounced when the patient is supine in some cases 1
• One case report documented that the rub was more pronounced in the left lateral decubitus position, though this is less typical 2

Optimal Auscultation Location

• The friction rub is typically most prominent at the left lower sternal border, though it may be audible across multiple precordial areas 1, 3
• Use the diaphragm of the stethoscope for best detection of this high-pitched sound 3

Acoustic Characteristics to Listen For

• The rub can be mono-, bi-, or triphasic in character, corresponding to atrial systole, ventricular systole, and ventricular diastole 1
• The sound is classically described as "sandpaper-scratching" or scratchy in quality 2
• It is a high-pitched, grating sound that may have a superficial quality 3

Critical Clinical Caveats

• The friction rub is highly specific for pericarditis but is only audible in approximately one-third of patients with confirmed acute pericarditis, making it an insensitive finding 4, 1
• Some sources report detection rates as high as 85% with careful examination, but the more conservative estimate of one-third is from major cardiology guidelines 5, 4
• The rub is characteristically transient and can disappear and reappear during the course of illness, necessitating repeated auscultatory examinations 1
• The absence of a friction rub does not exclude the diagnosis of pericarditis 1

Practical Examination Approach

• Perform multiple auscultatory examinations over time, as the rub may be intermittent 1
• Listen specifically during the optimal positioning (sitting, leaning forward, breath held) to maximize detection probability 1
• Focus attention on the left lower sternal border as the primary location 1, 3
• If the rub develops in the setting of acute myocardial infarction with persistent pain, hypotension, or nausea, urgent echocardiography is indicated 4