Abstract

Introduction: Patients with mitral annular calcification (MAC) can develop transmitral gradients despite lacking the commissural fusion that typifies rheumatic mitral stenosis (MS). As the gradient worsens, dyspnea, exercise intolerance, and heart failure can develop, similar to classical MS. A proposed mechanism relates to viscous energy dissipation (VED) due to turbulence as blood flows through the diseased valve into the ventricle.

Methods: 3D-TEE images of a normal mitral valve (MV) were employed to create a generic model. Using an end-systolic frame (prior to leaflet opening) the volume enclosed by the MV was segmented and printed. Latex was applied to the resulting mold reproducing the mitral valve and annulus. Multiple copies were created. Next, calcium phantoms made of hard plastic were cemented onto various annular locations to simulate mild (P2 only), moderate (P2-P3), and severe (P1-P3 and A2) MAC. An optically neutral silicone ventricle was created and the MV was placed in its inlet, using 4 cardinal sutures and a continuous stitch to fix it in place. Latex chordae were affixed to the leaflets and commissures, and then sutured to the ventricular wall. The synthetic MVs were tested in a left heart duplicator under heart rate and stroke volume conditions similar to those at rest. Fine particles were placed in a water/glycerol solution and particle image velocimetry tracked flow across the MV and through the ventricle, and VED was calculated (Figure).

Results: Preliminary data demonstrate increased VED in MAC valves compared with normal (Figure). Further, there was a graded response with 3x VED for mild MAC (compared to normal) and 4x VED for severe MAC.

Conclusions: MAC MS is associated with increased transmitral gradients and increased VED. These energy losses may contribute to signs and symptoms of heart failure in MAC patients. Further testing is planned with protocols simulating exercise conditions and various pathologies such as HFpEF and chronic infarction.