Which is best heard with a stethoscope (stethoscope): opening snap, systolic click, or mid-diastolic murmur?

Optimal Stethoscope Technique for Cardiac Auscultatory Findings

The mid-diastolic murmur is best heard with the bell of the stethoscope applied lightly at the apex, while the opening snap and systolic click are best heard with the diaphragm.

Mid-Diastolic Murmur

The mid-diastolic murmur requires specific technique for optimal detection:

• Use the bell of the stethoscope with light pressure at the cardiac apex 1
• This low-pitched, rumbling murmur originates from the mitral or tricuspid valves during early ventricular filling and is typically due to mitral or tricuspid stenosis 1
• The murmur results from disproportion between valve orifice size and diastolic blood flow volume 1
• Left-sided mid-diastolic murmurs are louder during expiration, which helps distinguish them from right-sided findings 1

Clinical Context

• Mid-diastolic murmurs can also occur with increased flow across normal valves (e.g., in atrial septal defect across the tricuspid valve, or in severe mitral regurgitation) 2
• The Austin-Flint murmur in severe aortic regurgitation is a low-pitched, rumbling mid-diastolic murmur at the apex, but notably an opening snap is absent in isolated aortic regurgitation 1

Opening Snap

The opening snap requires different technique:

• Use the diaphragm of the stethoscope for this high-frequency sound
• The opening snap is a sharp, high-pitched sound that occurs in mitral or tricuspid stenosis
• It is best heard between the apex and left sternal border
• The opening snap is absent in isolated aortic regurgitation, which helps differentiate the Austin-Flint murmur from true mitral stenosis 1

Systolic Click

The midsystolic click also requires the diaphragm:

• Use the diaphragm of the stethoscope at the apex for optimal detection 3
• The midsystolic click results from sudden tensing of the mitral valve apparatus as leaflets prolapse into the left atrium during systole 3
• Pressure on the stethoscope does not eliminate the click (unlike an S4 gallop, which disappears with pressure) 4
• The click-murmur complex of mitral valve prolapse characteristically moves earlier in systole with standing or Valsalva (decreased LV volume) and later toward S2 with squatting (increased LV volume) 3, 5

Key Distinguishing Features

• The systolic click is a high-frequency, non-ejection sound best heard at the apex 3
• When accompanied by a late systolic murmur (medium-to-high-pitched, musical or honking quality), this indicates mitral valve prolapse with some degree of mitral regurgitation 3, 6

Practical Pitfalls to Avoid

• Do not use heavy pressure with the bell when listening for mid-diastolic murmurs, as this converts the bell into a diaphragm and filters out low-frequency sounds 1
• Use the "inching" technique by keeping S2 as a reference point and moving the stethoscope from the aortic area to apex to accurately time sounds relative to the cardiac cycle 4
• In patients with emphysematous chests or increased anteroposterior diameter, listen over the xiphoid or epigastric area if sounds are faint over the usual precordial areas 4