Mitral chordae tendineae force profile characterization using a posterior ventricular anchoring neochordal repair model for mitral regurgitation in a three-dimensional-printed ex vivo left heart simulator

Figures

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  Figure 1:. Rendered illustration of the posterior ventricular anchoring neochordal (PVAN) repair and the hypothesized forces experienced on the repair suture throughout the cardiac cycle. During diastole (A), the PVAN suture is relaxed and experiences no tension. As systole begins (B), the closing posterior leaflet is held in position for optimal coaptation by the PVAN repair suture. Forces on the PVAN suture peak immediately before leaflet coaptation. Once the anterior and posterior leaflets coapt (C), the forces on the PVAN suture begin to fall as the leaflet forces are distributed throughout the 2 opposing leaflets (D). Images modified with permission and licensed from 3D4Medical Ltd.

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  Figure 2:. (A) Schematic of the Stanford Left Heart Simulator with each major component labelled. Reprinted with permission from [21]. Copyright 2019 Elsevier. (B) Computer-aided design rendering of the force-sensing post with embedded FBG sensor for measuring strain on the PVAN repair suture. (C) Ex vivo experimental set-up showing the PVAN repair suture anchored to the force-sensing post with embedded FBG sensor, which has been positioned to mimic the correct in vivo placement of the PVAN repair suture. FBG: Fibre Bragg Grating; PTFE: polytetrafluoroethylene; PVAN: posterior ventricular anchoring neochordal; TOE: transoesophageal echocardiography.

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  Figure 3:. High-speed videography still frames of the mitral valve from the surgeons’ view during prolapse (A, top) showing isolated P2 prolapse with ruptured (cut) chordae. Valve competency is restored following PVAN repair (A, bottom). Two-dimensional colour Doppler echocardiography images demonstrate moderate–severe mitral regurgitation (MR) secondary to posterior leaflet prolapse with an eccentric jet (B, top). PVAN repair corrected MR in all experiments. The repair suture attached to the force-sensing post can be appreciated in the echocardiography images after PVAN repair, with correction of posterior leaflet prolapse (B, bottom). Regurgitant fraction (C) measured by an electromagnetic flow probe demonstrates that PVAN repair effectively corrects MR to baseline levels (8.4 ± 1.5% vs 30.3 ± 6.5% vs 9.1 ± 4.0%). *P < 0.001. AL: anterior leaflet; LA: left atrium; LV: left ventricle; PL: posterior leaflet; PVAN: posterior ventricular anchoring neochordal.

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  Figure 4:. Composite pressure tracings (A) were indistinguishable between baseline and following PVAN repair, confirming restoration of aortic, left ventricular and left atrial pressures to baseline levels after PVAN repair. No significant difference was found in mean flow (B) between the baseline and PVAN repair groups. The shaded regions represent standard deviation. PVAN: posterior ventricular anchoring neochordal.

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  Figure 5:. Composite force tracings for each group of chordae tendineae at baseline (A), after prolapse was induced (B) and following PVAN repair (C). PVAN repair resulted in normalization of forces to baseline levels for anterior primary, posterior primary, anterior secondary and posterior secondary chordae tendineae. The force tracing for the PVAN repair suture is also shown in (C), which experienced extremely low peak forces. *Prolapse tracings were normalized to baseline ventricular pressures for comparative purposes in the setting of acute mitral regurgitation. PVAN: posterior ventricular anchoring neochordal.

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  Figure 6:. (A and B) Experimental set-up using uniaxial tensile testing machine to measure forces required to pull the repair suture from the posterior left ventricular myocardium. A 3D-printed clamp held the ventricular myocardial samples (n = 5) in place during experiments. (C) Results show that the average force required to pull the repair suture out of the posterior left ventricle is over 90 times higher than the average peak force experienced by the repair suture during normal physiological conditions (0.08 ± 0.04 N vs 6.90 ± 1.34 N, P < 0.001). PVAN: posterior ventricular anchoring neochordal.

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  Figure 7:. Close-up composite force tracing of the PVAN repair suture (note y-axis scale) overlaid with hypothesized renderings of PVAN repair suture forces. As predicted, forces during diastole are zero, peak in early-systole as the posterior leaflet is positioned for coaptation, after which point the forces are redistributed throughout the mitral valve apparatus and away from the PVAN suture, with marked reductions in PVAN repair suture forces throughout systole, until they fall to zero at the start of diastole. PVAN: posterior ventricular anchoring neochordal.