From the Guidelines
The S2 (second heart sound) is typically single or paradoxically split in patients with severe aortic stenosis, and not necessarily louder 1.
Key Points
- Aortic stenosis is often suspected based on a systolic ejection murmur on cardiac auscultation, but physical examination findings are specific but not sensitive for diagnosis of AS severity.
- The classic findings of severe AS include a loud, late-peaking systolic murmur, a single or paradoxically split S2, and a delayed and diminished carotid upstroke.
- A normally split second heart sound is the only physical examination finding that is reliable in excluding the possibility of severe AS.
- Echocardiography is recommended for diagnosis and assessment of AS severity, including evaluation of valve anatomy and function, and determining the LV response to pressure overload 1.
Diagnosis and Assessment
- Echocardiography is indicated when there is a systolic murmur that is grade 3/6 or greater, a single S2, or symptoms that might be due to AS.
- Doppler echocardiographic measurements, such as maximum jet velocity, mean transvalvular pressure gradient, and continuity equation valve area, can define the severity of the stenotic lesion.
From the Research
Analysis of Second Heart Sound in Aortic Stenosis
- The second heart sound (S2) is composed of two components: the aortic component (A2) and the pulmonic component (P2) 2.
- In aortic stenosis, the amplitude of both A2 and P2 components is decreased compared to normal subjects 2.
- The decrease in amplitude of both components is related to the prolongation of the isovolumic relaxation period of both ventricles, caused by the influence of the left ventricle on the right ventricle 2.
- Paradoxical splitting of S2, where P2 closes before A2, can occur in aortic stenosis due to delayed aortic closure 3.
- The use of wavelet transform and support vector machine can help detect paradoxical splitting in S2 with high accuracy and sensitivity 3.
- Analysis of phonocardiograms using signal processing techniques, such as discrete wavelet transform (DWT), can provide useful information for clinicians to diagnose and analyze the severity of aortic stenosis 4.
Comparison with Other Conditions
- In contrast to aortic regurgitation, where the second heart sound is often single or closely split due to prolongation of the Q-A2 interval 5.
- The split in S2 can be measured and analyzed using techniques such as DWT and CWT, and can be used to distinguish between normal and pathological cases 6.