What does a high peak velocity measured on Doppler indicate?

A high peak velocity measured on Doppler ultrasound indicates increased flow across a stenotic valve. When a valve is narrowed, or stenotic, the blood flow through the valve becomes more constricted, causing the velocity of blood flow to increase as it passes through the narrowed space. This phenomenon can be described by the principles of fluid dynamics, particularly the Bernoulli principle, which states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure.

In clinical practice, measuring the peak velocity can help sonographers and cardiologists assess the severity of the stenosis. Higher velocities correspond to more significant narrowing and can guide treatment decisions. It is important to differentiate this from other conditions, such as decreased myocardial contractility or myocardial hypertrophy, which affect the heart's overall function but do not necessarily produce the same Doppler flow characteristics as encountered with valvular stenosis. Normal blood flow would not produce abnormally high peak velocities, reinforcing that elevated velocities are indicative of pathological states such as stenosis.