Aortic stenosis (AS) is a condition where the heart’s aortic valve, which controls blood flow out of the main pumping chamber, becomes narrowed and stiffened. This narrowing restricts blood flow, forcing the heart muscle to work much harder. Listening to the heart with a stethoscope (auscultation) provides the first non-invasive clue for diagnosis. The characteristic sound produced by blood turbulence is known as a murmur, and its location and quality are essential for recognizing AS.
The Primary Auscultation Site
The primary location where the aortic stenosis murmur is heard most clearly is the “aortic area.” This anatomical site corresponds to the second intercostal space (between the second and third ribs) immediately to the right of the sternum. This spot is where the sounds generated by the valve project onto the chest wall with the greatest intensity.
The location is acoustically optimal because the ascending aorta, the largest artery carrying blood from the heart, begins directly behind this area. When blood is forcefully ejected through the narrowed valve, the resulting high-velocity jet of turbulent flow is directed toward the chest wall. This turbulence creates the harsh, whooshing sound characteristic of the murmur. Healthcare providers use the stethoscope’s diaphragm here, as it detects the higher-pitched components.
Characteristics of the Aortic Stenosis Murmur
The aortic stenosis murmur is described as a harsh, “ejection systolic” sound. Systolic means the sound occurs when the heart muscle is contracting and actively pushing blood out, specifically between the first and second normal heart sounds (“lub-dub”). This timing is a defining feature, distinguishing it from murmurs that occur when the heart is relaxed.
The intensity follows a distinctive crescendo-decrescendo pattern, often visualized as a diamond shape. The murmur starts softly, rapidly increases in loudness to a peak, and then quickly decreases before the heart’s contraction cycle ends. The point at which this peak intensity occurs provides clues about the severity of the stenosis.
A murmur that peaks early in systole suggests milder narrowing, while a late-peaking murmur indicates a more significant obstruction. Sometimes, an “ejection click” can be heard just after the first heart sound, marking the moment the stenotic valve snaps open. Maneuvers like squatting can temporarily increase the intensity of the murmur, while standing or performing the Valsalva maneuver may decrease it.
Understanding Sound Radiation and Associated Findings
While the murmur is loudest at the aortic area, the sound often travels, or “radiates,” to other parts of the body due to the path of the turbulent blood flow. The most common direction of radiation is upward toward the neck, where the sound is heard distinctly over the carotid arteries. This occurs because the high-velocity jet of blood leaving the aortic valve is aimed directly into the great vessels of the neck.
A less common, but diagnostically significant, phenomenon is when a musical, high-pitched component of the murmur radiates paradoxically to the apex of the heart (near the left nipple). This is known as the Gallavardin phenomenon. The musical quality heard at the apex contrasts with the harsher quality at the primary site.
Auscultation is complemented by other physical findings that help confirm the diagnosis and assess severity. One finding is the characteristic pulse pattern felt in the carotid arteries, described as pulsus parvus et tardus. This means the pulse is small in amplitude (parvus) and its peak is noticeably delayed (tardus), reflecting the restricted flow of blood out of the heart.
Furthermore, in severe aortic stenosis, the second heart sound (S2) is often diminished or absent. This happens because the severely stiffened aortic valve has lost its ability to close sharply and loudly.