1. The timing of the peak of the systolic murmur
2. The intensity of the S2 heart sound
3. Pulsus parvus et tardus

The intensity of the murmur typically increases as disease progresses, however when heart failure develops and cardiac output declines, the murmur becomes softer. Thus the intensity of the murmur is not a good indicator of disease severity.

The timing of the peak of the systolic murmur

The typical murmur of AS is a high-pitched, "diamond shaped" crescendo-decrescendo, mid-systolic ejection murmur heard best at the right upper sternal border radiating to the neck and carotid arteries (see figure below). In mild AS, the murmur peaks in early systole, however as the disease progresses the peak moves to later in systole since longer time is required to complete LV systole and aortic valve closure is delayed.

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The intensity of the S2 heart sound

As disease progresses and the aortic valve leaflets lose their mobility, the intensity of S2 decreases. When the S2 sound is no longer audible, it can be concluded that the AS is relatively severe.

Pulsus parvus et tardus

Perhaps the best bedside method to estimate the severity of AS is derived from evaluation of the carotid arteries. The phenomenon known as "pulsus parvus et tardus" refers to a weak (parvus) and delayed (tardus) carotid upstroke. To asses for "parvus," it is often helpful to palpate one’s own carotid artery while concurrently palpating the patient's carotid artery. It is important to note that in some elderly individuals the carotids may be stiff due to calcification, which may falsely normalize the carotid upstroke. To assess for "tardus," auscultate the patient's S2 heart sound while palpating their carotid upstroke. The S2 and carotid upstroke should occur almost simultaneously. If the carotid upstroke comes significantly after the S2 heart sound, "tardus" is present indicating severe AS.