Aortic Valve
The parameter used to characterize PPM is effective orifice area (EOA) indexed to the patient’s body surface area (BSA).

Severity	Indexed EOA (cm²/m²)
Hemodynamically insignificant	>0.85
Moderate	0.65-0.85
Severe	<0.65

Mitral Valve
Indexed EOA of mitral prostheses should ideally be no less than 1.2 to 1.3 cm²/m² to avoid abnormally high postoperative gradients.