Does aortic peak velocity increase or decrease as aortic stenosis (AS) becomes worse?

From the Guidelines

Aortic peak velocity increases as aortic stenosis (AS) becomes worse. As the aortic valve narrows progressively in AS, blood must flow through a smaller orifice, causing the velocity of blood flow to increase to maintain adequate cardiac output. This relationship follows the principles of fluid dynamics, where velocity increases when the same volume of fluid passes through a narrower opening. In mild AS, peak velocity typically ranges from 2.0-3.0 m/s, while moderate AS shows velocities of 3.0-4.0 m/s. Severe AS is characterized by velocities exceeding 4.0 m/s, with very severe AS defined by a peak velocity ≥5.5 m/s 1. This increased velocity creates a pressure gradient across the valve, which is another key parameter in assessing AS severity. The higher velocity also generates a louder systolic murmur that can be heard during physical examination. Clinicians use this velocity measurement via Doppler echocardiography as one of the primary methods to grade AS severity and make treatment decisions regarding valve replacement timing.

Key Points

• Aortic peak velocity is a key parameter in assessing AS severity.
• Velocity increases as the aortic valve narrows, with severe AS characterized by velocities exceeding 4.0 m/s.
• Very severe AS is defined by a peak velocity ≥5.5 m/s.
• Doppler echocardiography is used to measure velocity and grade AS severity.
• Treatment decisions, including valve replacement timing, are based on velocity measurements and other clinical factors.

Clinical Implications

• Accurate measurement of aortic peak velocity is crucial for diagnosing and managing AS.
• Clinicians should consider velocity measurements in conjunction with other clinical factors, such as symptoms and LV function, when making treatment decisions.
• Regular monitoring of velocity and other parameters is necessary to assess disease progression and guide treatment.

From the Research

Aortic Stenosis and Peak Velocity

• As aortic stenosis becomes worse, the aortic peak velocity increases.
• This is evident from studies that have investigated the relationship between peak aortic jet velocity and the severity of aortic stenosis 2, 3, 4.
• For instance, a study published in the Journal of the American Heart Association found that increasing peak aortic jet velocity was associated with incrementally higher risk for aortic stenosis-related events 4.
• Another study published in Circulation: Cardiovascular Imaging found that patients with very severe aortic stenosis (peak aortic jet velocity ≥5 m/s) had a higher mortality risk compared to those with less severe aortic stenosis 2.

Peak Aortic Jet Velocity and Aortic Stenosis Severity

• Peak aortic jet velocity is a key parameter used to assess the severity of aortic stenosis.
• A velocity of ≥4 m/s is generally considered indicative of severe aortic stenosis 3.
• However, the threshold for very severe aortic stenosis varies, with some guidelines suggesting a peak aortic jet velocity of ≥5 m/s 2 and others proposing ≥5.5 m/s.
• Studies have shown that delayed time to peak velocity is also useful for detecting severe aortic stenosis 5.

Clinical Implications

• The increase in peak aortic jet velocity with worsening aortic stenosis has important clinical implications.
• It highlights the need for regular monitoring and timely intervention in patients with severe aortic stenosis.
• Additionally, the use of velocity ratio, which is less dependent on flow, may be useful in evaluating aortic valve hemodynamics in patients with moderate aortic stenosis and reduced left ventricular ejection fraction 6.