Characteristics of Aortic Regurgitation Murmur
The murmur of aortic regurgitation is characteristically a high-pitched, early diastolic decrescendo murmur best heard at the left parasternal border, beginning immediately after S2 and diminishing throughout diastole. 1, 2
Primary Auscultatory Features
- Timing: Early diastolic, begins immediately after S2
- Configuration: Decrescendo (gradually decreasing in intensity)
- Pitch: High-pitched
- Location: Best heard at the left parasternal border in the 3rd-4th intercostal space
- Intensity: Variable, depending on severity
- Duration: May extend throughout diastole in severe cases
Associated Auscultatory Findings
Austin-Flint murmur: A low-pitched, rumbling middiastolic or presystolic murmur heard at the LV apex in severe, chronic AR 1, 3
- Results from regurgitant flow causing functional mitral stenosis
- No opening snap is present (distinguishing it from true mitral stenosis)
Systolic murmurs: Often coexist with AR murmurs due to increased stroke volume across the aortic valve 4
- These can sometimes be the predominant finding, especially when auscultation is performed by non-cardiologists
Auscultatory Techniques to Enhance Detection
- Patient position: Leaning forward, end-expiration, sitting up
- Diaphragm of stethoscope: Better for detecting the high-pitched diastolic murmur
- Firm pressure: Apply firm pressure with the diaphragm against the chest wall
Associated Physical Examination Findings
- Widened pulse pressure: Hallmark finding with systolic hypertension and normal or low diastolic pressure 2
- Bounding peripheral pulses: Water-hammer or Corrigan's pulse 2
- Forceful apical impulse: Due to LV enlargement in chronic AR 2
- Displaced point of maximal impulse (PMI): Due to LV dilatation
Differentiating Features from Other Diastolic Murmurs
- Pulmonic regurgitation: Similar timing but best heard at left upper sternal border
- Mitral stenosis: Middiastolic rumbling murmur at apex with opening snap
- Mitral valve prolapse with diastolic component: May have associated systolic click and typically occurs 70-110 msec after A2 5
Grading Severity Based on Auscultation
The intensity of the murmur does not always correlate with severity. Echocardiography is required for accurate assessment of AR severity 1.
Pitfalls and Caveats
- AR murmurs may be missed if auscultation is performed casually or in noisy environments
- Systolic murmurs may be the predominant finding in patients with AR, potentially leading to missed diagnosis if diastolic auscultation is not performed carefully 4
- The Austin-Flint murmur may be mistaken for mitral stenosis if not carefully evaluated 3
Echocardiography is the definitive diagnostic test for confirming the presence and severity of AR, as well as determining its etiology and impact on left ventricular size and function 1, 6.