Will a Bruit Be Heard with Arterial Stenosis?
Yes, a bruit can be heard with arterial stenosis, but the relationship is not absolute—bruits are frequently present with hemodynamically significant stenosis but may be absent in severe stenosis, occlusion, or mild disease. 1, 2
Understanding the Stenosis-Bruit Relationship
When Bruits Are Present
A bruit is produced by turbulent blood flow through a narrowed vessel and represents vascular pathology. 2
In arterial stenosis, bruits typically have a medium-pitched, harsh character and are heard directly over the affected vessel. 2
Approximately 69-75% of vessels with significant stenosis will exhibit an audible bruit, but this means a substantial minority of stenotic vessels remain silent. 3
The ACC/AHA guidelines specifically note that "a murmur or bruit may be heard in the left interscapular position, either due to the coarctation or to collaterals" in aortic coarctation, demonstrating that stenotic lesions commonly produce audible sounds. 1
Critical Pitfall: When Bruits Are Absent Despite Stenosis
The absence of a bruit does NOT exclude significant stenosis. This is a crucial clinical trap. 3
Bruits are often absent at high degrees of stenosis and in occluded vessels, likely because severely reduced flow produces less turbulence. 3
Research demonstrates that in 56% of internal carotids clinically documented as having a bruit, no turbulence was actually found—many were transmitted cardiac sounds or external carotid disease. 3
Post-stenotic turbulence is almost zero for 50-60% severity stenoses, meaning mild-to-moderate stenosis may not generate audible sounds. 4
Turbulent kinetic energy and acoustic signals become significant only at 75% severity or greater, with dramatic increases at 87% and 95% severity levels. 4
Clinical Diagnostic Approach
Physical Examination Specifics
Check for abnormal high-frequency bruit produced by turbulence due to stenosis, distinguishing this from the normal low-frequency bruit with systolic and diastolic components. 1
Trace the sound to its point of maximum intensity—true bruits are loudest directly over the affected vessel, while radiating cardiac sounds diminish away from the heart. 2
In carotid evaluation, patients with carotid bruits have >50% higher likelihood of harboring hemodynamically significant internal carotid stenosis, though the positive predictive value is only approximately 30%. 2
When to Pursue Further Testing
The presence or absence of a bruit should never be the sole determinant for further evaluation. 1, 2
Duplex carotid Doppler has 90% sensitivity and 94% specificity for identifying clinically significant >70% stenosis, making it the appropriate screening test regardless of bruit presence. 1
The ACR emphasizes that in otherwise uncomplicated cases, ultrasound imaging alone may be the only necessary examination in a patient with carotid bruit. 1
Caution must be observed when evaluating patients with extremely severe stenosis or multivessel involvement because Doppler can overestimate or underestimate stenosis severity. 1
Key Clinical Pearls
Bruits indicate turbulent flow but their absence does not exclude disease—silent stenoses are common, particularly at extremes of severity. 3, 4
Cervical bruits may originate from diseased external carotid arteries or transmitted cardiac sounds, not just internal carotid stenosis. 3
Continuous murmurs over parasternal areas and around the left scapula suggest collateral vessel development in the setting of significant proximal obstruction like aortic coarctation. 1
The acoustic spectrum becomes richer and more intense with increasing stenosis severity, with distinct murmur patterns emerging at 75% stenosis and above. 4