In the Modified Bernoulli equation, p1 represents:

In the Modified Bernoulli equation, p1 represents:

• A. Pressure of the proximal chamber
• B. Pressure of the distal chamber
• C. Mean transvalvular gradient
• D. Pressure drop across the valve

Answer: (A)

The essential idea is that the Modified Bernoulli equation links the pressure drop across a valve to the flow velocity through the valve. It states p1 − p2 = 4v^2, where p1 is the pressure on the side before the narrowing (upstream or proximal chamber) and p2 is the pressure beyond the narrowing (downstream). So p1 represents the proximal chamber pressure—in practice, the pressure in the chamber that feeds the valve (for aortic stenosis, the left ventricular systolic pressure). The downstream pressure p2 is the pressure in the chamber beyond the valve (the aorta, in that example). This is why the other options don’t fit: the distal chamber pressure is p2, the mean transvalvular gradient is the overall ΔP, and the pressure drop across the valve is the gradient ΔP itself, not p1 alone.

The essential idea is that the Modified Bernoulli equation links the pressure drop across a valve to the flow velocity through the valve. It states p1 − p2 = 4v^2, where p1 is the pressure on the side before the narrowing (upstream or proximal chamber) and p2 is the pressure beyond the narrowing (downstream). So p1 represents the proximal chamber pressure—in practice, the pressure in the chamber that feeds the valve (for aortic stenosis, the left ventricular systolic pressure). The downstream pressure p2 is the pressure in the chamber beyond the valve (the aorta, in that example). This is why the other options don’t fit: the distal chamber pressure is p2, the mean transvalvular gradient is the overall ΔP, and the pressure drop across the valve is the gradient ΔP itself, not p1 alone.