What is the PHT range for mild mitral stenosis?

• A. 60-90 ms
• B. 60-120 ms
• C. 90-150 ms
• D. 150-200 ms

Answer: (C)

PHT, or pressure half-time, is used to estimate the mitral valve area in mitral stenosis: the larger the valve area, the shorter the PHT, and vice versa. The relationship is commonly approximated by MVA ≈ 220 / PHT (with PHT in milliseconds). To have mild stenosis, the valve area should be greater than about 1.5 cm². Solving 1.5 ≈ 220 / PHT gives PHT ≈ 146–150 ms as the upper limit for mild stenosis. The range around 90–150 ms aligns with MVA values roughly from ~2.4 cm² down to ~1.5 cm², which corresponds to mild disease and just up to the border of moderate severity. Values shorter than 90 ms would indicate a substantially larger valve area (very mild or absent stenosis), while longer than 150 ms moves toward moderate severity. Keep in mind that PHT can be affected by heart rate, loading conditions, and coexisting valve lesions, so it’s an estimate rather than a definitive measure.