New Device for the Treatment of Ischemic Mitral Regurgitation: Proof-of-Concept in an in Vitro Model

Objectives: Adequate surgical treatment of ischemic mitral regurgitation (IMR) is still an unresolved issue. In contrast to non-ischemic MR, where current guidelines clearly favor mitral valve repair (MVR) over replacement, MVR in IMR shows unsatisfying results. Due to the underlying pathophysiology, stand-alone ring annuloplasty is not sufficient and associated with a high recurrence rate of MR. A potential solution are subvalvular repair techniques aiming to restore the natural geometry of the left ventricle. This in vitro study introduces a new device for subvalvular MVR.

Methods: We developed a new papillary muscle (PM) bail for subvalvular MVR. It consists of two frames for the attachment of the PMs. These frames are connected with two holding bars serving for fixation of the device on the atrial site of an annuloplasty ring. The frames are tilted in an angle of 80° against each other and their design was based on physiological PM shape. The in vitro evaluation was performed in a pulse duplicator determining regurgitant volume (v_r). Systolic/diastolic pressure was 125/80mmHg, heart rate 64min⁻¹ and stroke volume 54ml. Porcine mitral valves (n = 10) with an anterior-posterior (a.-p.) diameter of 18–21mm, including the chordae tendineae and PMs, were fixated on a holding device, consisting of an anatomically bean-shaped holding ring and adjustable frames for the attachment of the PMs. To simulate mitral annulus dilation, the holding ring was constructed with an anteroposterior diameter of 37 mm. In the first experimental run, v_r was determined in the mitral valves fixated on the holding device. Afterwards, the PMs were attached to our newly developed PM bail and the measurements repeated. To evaluate the isolated effect of our new device on v_r, we did not perform reduction ring annuloplasty.

Results: In the model without our new device, the mean value for v_r was 44.3 ± 12.38 mL/stroke standard deviation. After subvalvular reconstruction with our newly developed PM bail, v_r was reduced to 33.1 ± 11.68 mL/stroke. This reduction was significant (p = 0.009).

Conclusion: In this specific in vitro model, our newly developed device for subvalvular MVR led to a significant reduction of v_r, thus representing a promising technique to potentially improve the results of MVR in IMR. Additional studies are required to further investigate and improve our device, especially with regard to concomitant annuloplasty.