Effect of anterior strut chordal transection on the force distribution on the marginal chordae of the mitral valve

Abstract

BACKGROUND Transection of the secondary chordae on the anterior leaflet of the mitral valve to relieve leaflet tethering and reduce regurgitation is an experimentally proven procedure to correct functional mitral regurgitation. In this study, we sought to investigate if transecting the secondary chordae has an impact on the marginal chordal force on the same leaflet. METHODS Adult porcine mitral valves (N =8) were studied in a pulsatile heart simulator, in which the papillary muscle positions can be precisely positioned. The anterior marginal chordae were instrumented with miniature transducers to measure the chordal forces. Each valve was studied under baseline conditions, three different tethering conditions [apical, apical-lateral, apical-lateral-posterior], and following chordal cutting in the three tethering conditions. The temporal changes, the peak and average marginal chordal forces under each condition are reported. RESULTS Apical tethering increased marginal chordal force by an average 96% but remained unchanged after chordal cutting. With apical-lateral tethering, marginal chordal force increased by 210% from baseline, and further increased to 350% of baseline after chordal cutting. After apical-lateral-posterior tethering, the marginal chordal force increased to 335% of baseline before transection and by 548% after the transection. CONCLUSIONS Increase in marginal chordal force after secondary chordal cutting depends on the location of the papillary muscles and the extent of leaflet tethering. While, chordal cutting may not alter the valve mechanics under minimal leaflet tethering, it significantly impacts the mechanics when the leaflet tethering is more pronounced, which is typically seen in patients with functional mitral regurgitation.

Bench Models for Assessing the Mechanics of Mitral Valve Repair and Percutaneous Surgery

“…1a). 5,8,12,[18][19][20]22,23,[26][27][28][29][30][31][32][34][35][36][37][38][39]44,[46][47][48] These components are supplemented by systemic resistances and compliances to control cardiac output, systemic pressures, and dampen undesired flow and pressure oscillations within the rigid chambers of the system.…”

“…While the majority of annuluses reported in literature provide only a single size, adjustable and flexible annuluses have been reported. 22,29,37,46,47 These designs are described and evaluated in subsequent sections evaluating methods of assessing MV annuloplasty.…”

“…These models have been used to evaluate multiple repairs on a single MV, changes in leaflet mobility and coaptation, improvements in transmitral hemodynamics, and provide direct quantitative measures of tissue loading. [3][4][5]8,9,[11][12][13][14][17][18][19][20][22][23][24][26][27][28][29][30][31][32][33][34][35][36][37][38][39]41,42,44,[46][47][48] Within the limitation of each setup, these models are more risk averse, controlled, reproducible, and less expensive than clinical studies or large animal models. Understanding the advantages and limits of these models will aid the interpretation of their resulting data, inform future experimental evaluations, and further the translation of results to procedure and device development.…”

Chronic Ischemic Mitral Regurgitation

“…Padala et al 19 have recently assessed the effects of secondary chordal cutting on marginal (primary) chordae in a pulsatile left heart simulator. These investigators found an increase in marginal chordal force when apical tethering was induced, with no further adverse effect of secondary chordal cutting.…”

“…However, division of secondary chords led to an increased force on marginal chords when the leaflets were tethered in an apical-lateral direction, with an even more pronounced effect during apical-lateral-posterior tethering. 19 What effect such increased forces on the marginal chords may have on ventricular function is currently unknown, but it is important to note that the marginal chord force levels did not reach those required to induce chordal rupture.…”