Aortic stenosis (AS) is a common heart valve disease where the aortic valve, which controls blood flow from the heart’s main pumping chamber to the rest of the body, becomes stiff and narrowed. Healthcare professionals use a stethoscope to listen for a specific sound, known as a heart murmur, that results from this narrowing. Locating where this sound is loudest and how it travels is a fundamental step in diagnosing the condition.
Understanding Aortic Stenosis
The aortic valve sits between the left ventricle, the heart’s strongest chamber, and the aorta, the body’s largest artery. Its purpose is to open fully during a heart contraction to allow oxygenated blood to flow out to the body, and then close tightly to prevent backward flow. Aortic stenosis occurs when the valve leaflets thicken or fuse, preventing them from opening completely.
The obstruction forces the left ventricle to work harder to push blood through the smaller opening. As blood is squeezed through the narrowed valve at high speed, the flow becomes chaotic and turbulent. This turbulent motion generates vibrations that are audible as a heart murmur, the sound of this disrupted blood flow. The intensity and characteristics of this murmur relate directly to the severity of the obstruction and the resulting pressure differences across the valve.
Identifying the Primary Auscultation Point
The sound generated by a stenotic aortic valve is heard most clearly over the “Aortic Area” of the chest. This location, known as the punctum maximum, is the second intercostal space immediately to the right of the sternum (Right Upper Sternal Border). The sound is loudest here because this area is closest to the ascending aorta, where the turbulent blood is ejected. The sound waves travel directly to the chest wall with minimal interference, allowing for the clearest detection.
To maximize the audibility of the murmur, the patient is often asked to sit upright and lean slightly forward while holding their breath at the end of exhalation. This positioning brings the heart closer to the chest wall, making the high-frequency components easier to detect. Intense turbulent flow may also create a palpable vibration, known as a systolic thrill, felt over the upper right sternal border.
The precise location of maximal intensity helps distinguish AS from other heart valve issues. For instance, pulmonary valve murmurs are heard at the second intercostal space on the left side of the sternum. Localizing the loudest point to the right of the sternum allows the clinician to attribute the sound confidently to the aortic valve. The proximity of the stethoscope to the turbulent source at the base of the heart makes this the primary diagnostic listening point.
Sound Transmission to Other Areas
While the murmur is loudest at the Aortic Area, the vibrations travel away from the heart along the path of blood circulation. The sound commonly transmits upward into the neck, specifically over the carotid arteries. This radiation occurs because the turbulent jet of blood is forcefully ejected into the aorta, carrying the sound waves into the major neck arteries.
A clinician often places the stethoscope over the carotid artery to confirm the sound heard there is a continuation of the chest murmur. The presence of this radiating sound is a strong indicator of aortic stenosis, as it follows the physical route of the blood flow. In some patients, especially those with a heavily calcified valve, the murmur may also radiate downward to the apex of the heart (near the fifth intercostal space).
This specific apical radiation is sometimes called the Gallavardin phenomenon. When the murmur is prominent at the apex, it might be mistaken for mitral regurgitation. However, the apical component of the AS murmur often has a higher-pitched, more musical quality than the harsh sound heard at the base, aiding in differentiation.
Distinguishing Features of the Murmur
Beyond its location, the aortic stenosis murmur is classified as a systolic ejection murmur. This means it occurs during the heart’s contraction phase, between the first heart sound (S1) and the second heart sound (S2). The sound has a distinct crescendo-decrescendo, or diamond-shaped, pattern, starting softly after S1, building to a peak loudness, and fading before S2.
The quality of the murmur is described as harsh, rough, or coarse. As the disease becomes more severe, the peak of the murmur tends to shift later in the systolic phase, closer to the second heart sound. This shift in timing provides a clue to the severity of the valve obstruction.
Associated findings include a diminished or absent aortic component of the second heart sound (S2) because the stiffened valve cannot close sharply. Palpation of the pulse may reveal a slow-rising and sustained pulse, known as pulsus parvus et tardus. This reflects the delayed and reduced blood ejection from the heart.