Normal mitral annulus dynamics and its relationships with left ventricular and left atrial function.

Area of Science:

• Cardiovascular Imaging
• Cardiac Mechanics
• Echocardiography

Background:

• Mitral annulus (MA) geometry and dynamics are essential for normal mitral valve (MV) function.
• Previous studies reported static MA reference values, but normal MA dynamics across the entire cardiac cycle remain debated.

Purpose of the Study:

• To assess mitral annulus (MA) size and shape changes throughout the cardiac cycle in healthy volunteers.
• To characterize normal MA dynamics and their relationship with atrial and ventricular function.

Main Methods:

• Utilized 3D transthoracic echocardiography to acquire full-volume datasets from 50 healthy volunteers.
• Measured projected MA area (MAA), circumference (MAC), antero-posterior (AP) and anterolateral-posteromedial (ALPM) diameters, and sphericity index (SphI) at key cardiac cycle phases.

Main Results:

• MAA and AP diameter showed significant dynamic changes, contracting before mitral valve closure (MVC) due to left atrial contraction.
• Maximum MAA occurred at end-systole (ES), while maximum AP diameter and SphI were observed at early diastolic filling (EDF).
• MAA fractional shortening was 35 ± 10%, AP diameter change was 25 ± 10%, MAC fractional change was 35 ± 10%, and ALPM diameter change was 13 ± 8%.

Conclusions:

• The study elucidates normal mitral annulus (MA) dynamics, revealing pre-systolic contraction related to left atrial (LA) contraction.
• Normal MA dynamics are linked to physiological LA-LV coupling, requiring coordinated LA and LV systole for complete MA contraction.