Mitral valve coaptation and its relationship to late diastolic flow: A color Doppler and vector flow map echocardiographic study in normal subjects

Abstract

Background Three competing theories about the mechanism of mitral coaptation in normal subjects were evaluated by color Doppler and vector flow mapping (VFM): (1) beginning of ventricular (LV) ejection, (2) “breaking of the jet” of diastolic LV inflow, and (3) returning diastolic vortices impacting the leaflets on their LV surfaces. Methods and Results We analyzed 80 color Doppler frames and 320 VFM measurements. In all 20 normal subjects, coaptation occurred before LV ejection, 78±16 ms before onset. On color Doppler frames the larger anterior, and smaller posterior vortices circle back and, in all cases, strike the ventricular surfaces of the leaflets. On the first closing‐begins frame, for the first time, vortex velocity normal to the ventricular surface of the anterior leaflet (AML) is greater than that in the mitral orifice, and the angle of attack of LV vortical flow onto the AML is twice as high as the angle of flow onto the valve in orifice. Thus, at the moment coaptation begins, vortical flow strikes the mitral leaflet with higher velocity, and higher angle of attack than orifice flow, and thus with greater force. According to the “breaking of the jet” theory, one would expect to see de novo LV flow perpendicular to the leaflets beginning after transmitral flow terminates. Instead, the returning continuous LV vortical flow that impacts the valve builds continuously after the P‐wave. Conclusions Late diastolic vortices strike the ventricular surfaces of the mitral leaflets and contribute to valve coaptation, permitted by concomitant decline in transmitral flow.

Relationship between left ventricular vortex and preejectional flow velocity during isovolumic contraction studied by using vector flow mapping

“…The mean velocity along the flow axis line (V LVOT ) should be representative of the flow velocity in the LVOT. Our measurement results in normals were lower than those in the study by Sherrid et al . This should be because the flow velocity was measured at different moments within the heart cycle.…”

“…We thought that the changes in LV structure and function would alter the occurrence of the IVC vortex and then cause a loss of efficiency of momentum transfer, which could further aggravate LV dysfunction and remodeling. In addition, the late diastolic vortices strike the ventricular surfaces of the mitral leaflets and contribute to valve coaptation . The impaired IVC vortex and its greater distance to the LVOT might lead to a delay in leaflet coaptation and higher regurgitant closing volumes.…”

Factors influencing the end‐diastolic vortex assessed by using vector flow mapping

“…This technique combines measured axial flow velocities (parallel to the ultrasound beam) with inferred radial flow velocities (perpendicular to the ultrasound beam) based on physical principles . VFM has proved to be a reasonably accurate tool for delineating the main features of intracavitary flow . By using VFM, we were able to assess the relations of the late diastolic vortex to LV structure and function in normal and abnormal ventricles in the present study.…”

“…During left ventricle (LV) early filling and atrial contraction, transmitral flow entering the LV leads to the formation of vortex rings along the tips of the mitral valve leaflets . In a two‐dimensional (2D) plane, the vortex ring appears as a stronger anterior vortex and a weaker posterior one.…”

“…Obviously, the vortex can favor an effective LV filling and play an important role in diastolic function. In addition, the late diastolic vortices strike the ventricular surfaces of the mitral leaflets and contribute to valve coaptation during mitral valve closure …”