The rate at which pressure differences decrease in diastole provides a means to estimate the severity of stenosis, with more severe grades of stenosis retarding the rate at which a gradient diminishes in diastole.
mitral valve area in square centimeters =
= 220 / (pressure half-time in msec)
where:
• Pressure half-time is the time required for the pressure to diminish to half of its peak diastolic value, or approximately 70% of its initial velocity.
Interpretation:
• Inaccuracies may occur in the presence of significant aortic regurgitation or immediately after a mitral valvuplasty.
• A mitral valve areas less than 1.5 square centimeters generally denotes hemodynamically significant degrees of obstruction.
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