Difference Between a Bruit and Radiating Heart Sounds
A bruit is a vascular sound produced by turbulent blood flow through a narrowed vessel, while radiating heart sounds are cardiac sounds that transmit beyond their point of origin due to normal anatomical conduction pathways.
Bruits
Definition and Characteristics
- A bruit is a sound produced by turbulent blood flow through a narrowed or stenotic blood vessel, representing vascular pathology 1
- Bruits typically have a medium pitched, harsh character and are heard directly over the affected vessel 1
- Most bruits are systolic, though they can sometimes be continuous, and may increase with inspiration 1
Common Locations and Clinical Significance
- Carotid bruits are heard at the right or left upper sternal border, supraclavicular region, or anterior portion of the lower neck 1
- Carotid bruits are important diagnostic signs of potential underlying carotid stenosis, with patients having >50% higher likelihood of harboring hemodynamically significant internal carotid stenosis 1
- Peripheral bruits may be heard over the back or lateral sides of the chest (pulmonary artery stenosis), abdomen (renal artery stenosis), or left upper quadrant (splenic artery stenosis) 1, 2
Diagnostic Value
- The positive predictive value of carotid bruits for significant stenosis is relatively low (approximately 30%), which increases the importance of radiographic evaluation 1, 3
- Bruits are associated with increased risk of cardiovascular events - patients with carotid bruits have higher rates of myocardial infarction (3.69 vs 1.86 per 100 patient-years) and cardiovascular death (2.85 vs 1.11 per 100 patient-years) compared to those without bruits 4
Radiating Heart Sounds
Definition and Characteristics
- Radiating heart sounds are cardiac sounds that originate at the heart valves but are transmitted to areas beyond their point of maximum intensity 1
- These sounds follow normal anatomical conduction pathways and represent the transmission of normal or abnormal cardiac sounds 1
- Unlike bruits, radiating heart sounds maintain the same timing and characteristics as their source but may be softer in intensity 1
Common Examples
- Aortic valve sounds often radiate to the carotid arteries and can be mistaken for carotid bruits, especially in children with aortic stenosis 5
- Mitral valve sounds may radiate to the axilla 1
- Tricuspid valve sounds may radiate to the right of the sternum 1
Key Differences
Origin
- Bruits originate from turbulent flow in blood vessels due to stenosis or other vascular abnormalities 1
- Radiating heart sounds originate from cardiac valves and are transmitted through tissue 1
Clinical Significance
- Bruits indicate potential vascular pathology and increased cardiovascular risk 1, 4
- Radiating heart sounds may be normal or represent cardiac pathology, depending on the nature of the original heart sound 1
Distinguishing Features
- Bruits change with maneuvers that affect blood flow (e.g., carotid bruits may disappear with bilateral shoulder hyperextension) 1
- Radiating heart sounds maintain synchrony with cardiac cycle and don't change with vascular compression 1
- Bruits have a different sound spectrum compared to radiating heart sounds - bruits contain both turbulent flow components and resonant spectra from arterial wall vibration 6
Clinical Approach to Differentiation
- Carefully trace the sound to its point of maximum intensity - bruits are loudest directly over the affected vessel 1
- Compare timing with the cardiac cycle - both may be systolic, but bruits may extend into diastole 1
- Perform maneuvers that affect blood flow or vessel compression to help distinguish between the two 1
- Consider advanced diagnostic testing such as duplex ultrasonography when clinical differentiation is difficult 3, 2