Aortic Stenosis Murmur: Auscultatory Characteristics and Clinical Approach
The aortic stenosis murmur is a midsystolic, crescendo-decrescendo (diamond-shaped) systolic ejection murmur best heard at the cardiac apex with radiation to the upper right sternal border and carotid arteries. 1
Key Acoustic Characteristics
The murmur begins shortly after S1 when ventricular pressure rises sufficiently to open the stenotic aortic valve, peaks in mid-to-late systole, and diminishes before S2. 2, 1 The crescendo-decrescendo configuration reflects the flow dynamics across the narrowed valve as ejection increases then declines. 2
Optimal auscultation requires:
- Positioning the stethoscope at the cardiac apex (where the murmur is typically loudest) and the upper right sternal border 1
- Using the diaphragm of the stethoscope for these higher-pitched sounds 3
- Listening during expiration when left-sided sounds are amplified 3
- Ensuring a quiet room with the patient's chest fully exposed 3
Critical Physical Examination Findings for Severity Assessment
The classic triad of severe aortic stenosis includes: 1
- A loud (grade 4/6 or greater) late-peaking systolic murmur radiating to the carotids
- Single or paradoxically split second heart sound (S2)
- Delayed and diminished carotid upstroke (pulsus parvus et tardus)
Second Heart Sound Abnormalities
A soft or absent A2 component of S2 is highly specific for severe aortic stenosis and mandates immediate echocardiography. 2, 3, 4 Valve calcification and immobility prevent normal forceful closure of the aortic leaflets, progressively dampening the closure sound as stenosis worsens. 4 Reversed splitting of S2 (splitting during expiration, single during inspiration) may also indicate severe disease. 2
Carotid Pulse Assessment
A slow-rising, diminished carotid pulse (pulsus parvus et tardus) strongly suggests severe stenosis, with positive likelihood ratios ranging from 2.8 to 130. 5 However, this sign may be absent in elderly patients due to age-related arterial stiffening. 1, 4
Additional Examination Clues
- A systolic ejection click heard during both inspiration and expiration suggests a bicuspid aortic valve 2, 1
- A sustained apical impulse reflects left ventricular hypertrophy from chronic pressure overload 1
- Mid-to-late peak intensity of the murmur has positive likelihood ratios of 8.0 to 101 for severe stenosis 5
Dynamic Auscultation Maneuvers
Changes in left ventricular loading conditions alter murmur characteristics: 2
- Standing or Valsalva maneuver (decreased preload): Most murmurs decrease in intensity 3
- Squatting (increased preload and afterload): Increases murmur intensity 2
- Handgrip exercise (increased afterload): Can accentuate certain findings 3
Critical Diagnostic Pitfalls
The "Silent" Severe Aortic Stenosis
Severe aortic stenosis can present with a faint or absent murmur, particularly in elderly patients or those with low cardiac output. 4 When left ventricular function is markedly depressed, transvalvular flow velocity falls, producing a soft or inaudible murmur despite critical valve narrowing. 4
Do not assume that a grade 2/6 or softer murmur excludes severe aortic stenosis. 4 Murmur intensity does not reliably reflect stenosis severity when cardiac output is compromised. 4
Detection Rates in Clinical Practice
Real-world data show that clinicians detect the aortic stenosis murmur in only 39% of patients with moderate-to-severe disease. 6 Detection is significantly better in outpatient settings (OR 3.40), when the diagnosis is already known (OR 2.77), in symptomatic patients (OR 1.91), and in female patients (OR 1.97). 6
Immediate Diagnostic Approach
Order transthoracic echocardiography immediately for: 1, 4
- Any systolic murmur grade 3/6 or greater
- Any systolic murmur with a single or paradoxically split S2
- Any systolic murmur with symptoms potentially attributable to aortic stenosis (exertional dyspnea, syncope, angina, or heart failure)
- Any elderly patient with exertional symptoms and any systolic murmur, regardless of grade
- Abnormal ECG or chest radiograph in a patient with any cardiac murmur 2, 4
Echocardiographic Severity Criteria
Severe aortic stenosis is defined by: 2
- Aortic valve area ≤1.0 cm² (or indexed area <0.6 cm²/m² BSA)
- Peak velocity ≥4.0 m/s
- Mean gradient ≥50 mmHg (at normal transvalvular flow)
Low-Flow/Low-Gradient Assessment
When mean gradient is <40 mmHg with valve area <1.0 cm², low-dose dobutamine stress echocardiography differentiates true severe stenosis (valve area remains <1.0 cm² with increased flow) from pseudo-severe stenosis (valve area increases >0.2 cm² with augmented flow). 4
Surveillance Recommendations for Asymptomatic Patients
Follow-up echocardiography intervals based on severity: 4, 7
- Severe aortic stenosis: Every 6-12 months
- Moderate aortic stenosis: Every 1-2 years
- Mild aortic stenosis: Every 3-5 years
Management Implications
Aortic valve replacement is recommended for: 2
- All patients with severe aortic stenosis and any valve-related symptoms (angina, dyspnea, syncope) - Class I, Level B
- Asymptomatic patients with severe aortic stenosis who develop symptoms during exercise testing - Class I, Level C
- Patients with severe aortic stenosis and left ventricular systolic dysfunction (LVEF <50%) - Class I, Level C
Conservative management of severe symptomatic aortic stenosis carries a grave prognosis, while aortic valve replacement markedly improves survival. 4 Patients should be educated about the importance of promptly reporting any symptoms. 7
Cardiology referral is recommended for: 7
- All patients with symptomatic moderate or severe aortic stenosis
- Asymptomatic patients with severe aortic stenosis
- Any patient with left ventricular systolic dysfunction and aortic stenosis