Mitral Valve Closure: Left Atrial Pressure Exceeds Ventricular Pressure

The mitral (bicuspid) valve closes when left ventricular pressure exceeds left atrial pressure at the onset of ventricular systole. This prevents retrograde flow into the atrium during ejection.

Pressure Dynamics

• Diastole: LA pressure > LV pressure → valve open (passive filling + atrial kick).
• Systole: LV pressure rapidly rises > LA pressure → valve closes (S1 heart sound).
• Isovolumetric relaxation: LV pressure falls < LA pressure → valve reopens.

Clinical Relevance

• Mitral stenosis: Impaired opening → elevated LA pressure, pulmonary congestion.
• Mitral regurgitation: Incomplete closure → systolic backflow, volume overload.
• Echo assessment: E/A ratio, deceleration time, pulmonary vein flow evaluate diastolic function.

Normal valve function ensures unidirectional flow and optimal cardiac output.