Coaptation Reserve of the Mitral Valve- Emerging Mitral Regurgitation Detection Index

While the lack of regurgitation is often seen as proof of proper MV function, leaflet apposition preserves systolic competence of the mitral valve (MV), and valves may actually be at varied degrees of risk for developing mitral regurgitation (MR) dependent on the coaptation reserve. Assessment of alterations in MV geometry in patients with functional MR is challenging and little understood, partly because to the heterogeneous remodelling of the MV system in response to ischemia. In primary MR, structural derangements of the MV are easily recognised. Assessment of geometric indices of MV remodelling was once regarded as an offline research approach; however, as computing power has increased, complicated dynamic geometric analysis of the valve apparatus may now be conducted in near real-time. As a result, there is a growing interest in trying to comprehend the geometric modifications of the MV apparatus in response to ischemia insults. Regardless of its origin, the last stage of remodelling depletes the apposition zone between the anterior and posterior MV leaflets. The degree of apposition, also known as coaptation reserve or coaptation depth, is the ultimate measured target for sustaining the MV's systolic competence. Therefore, coaptation depth may be utilised to predict the probability of ischemia-related remodelling of the MV apparatus. This suggests that a non-regurgitant mitral valve with a smaller coaptation reserve is at a higher risk of developing future regurgitation than a valve with a bigger coaptation reserve. Mufarrih et al. and Jainandunsing et al. have recently published publications that provide a clear understanding of Mitral Valve Coaptation Reserve.

Ischemia-induced remodelling of the MV apparatus causes apical displacement of the coaptation site, resulting in a decrease in coaptation reserve. Traditional geometric indicators for evaluating the degree of remodelling include measurements of tenting height (TH) and tenting area (TA), which stand in for the evaluation of coaptation reserve. Although not explicitly assessed, increasing apical displacement of the coaptation site implies coaptation depletion. Since TH and TA measurements are based on single tomographic sections planes, they do not accurately depict the MV's whole topography. Mufarrih et al. have recently proven that tenting volume (TV) obtained from three dimensions (3D) has a higher negative association with coaptation area. As detailed by Jainandunsing et al., technological developments in 3D echocardiographic imaging have made it feasible to assess the individual coaptation depths at various sites along the closure line. This research confirms the conventional belief that patients with structurally normal valves would have the greatest depth at the central coaptation site, i.e., the A2-P2 area. This does not, however, explain the central jet of regurgitation that is often seen in individuals with functional MR. Coaptation reserve is a function of circumferential expansion of the annulus, hence indexing to account for annular dilation is crucial.

In this perspective, the paper of Jainandunsing et al. represents a substantial advancement. They have tried to detect a specific structural reserve in particular MVs using a complex algorithm. They have identified structural remodelling as a heterogeneous phenomena, with resulting differences in structural reserve, and there are particular indices that explain the durability of MV leaflets at various places in connection to increasing annular dilatation. This research contradicts the popular belief that, in a structurally normal MV, the A2-P2 segment has the greatest coaptation reserve in comparison to the commissural segments. Intriguingly, in their investigation, the lowest coaptation reserve score was seen in the majority of patients at A2-P2, which further explains the higher number of patients with functional MR central jet. Notable also is the correlation between coaptation reserve index and the location of MR jets in 66% of their patients with trace to moderate MR.

Defining the indicators of the changing morphology of the mitral annulus, leaflets, and papillary muscles throughout various periods of the cardiac cycle and assessing their influence on valve integrity will be a key issue moving ahead. The developments in non-invasive imaging that have gotten us to this point in our understanding of the complicated geometry of the mitral valve indicate that we live in a fascinating era. On the other side, artificial intelligence has enabled the incorporation of sophisticated algorithms in a single location, allowing us to forecast the future and alter its direction as we see fit. The coaptation area is currently computed manually with extensive human input and is an off-line approach. To be clinically practical, this method must be accessible online with substantial productivity improvements. However, this should not diminish the therapeutic significance of this idea.

Reference –

Rehman, Taha A., et al. “Mitral Valve Coaptation Reserve – Identifying the at-Risk valve.” Journal of Cardiothoracic and Vascular Anesthesia, vol. 0, no. 0, 2023, doi:10.1053/j.jvca.2023.01.020.

Mufarrih SH, Sharkey A, Mahmood F, et al. Geometric Indices for Predicting Ischemic Mitral Regurgitation: Correlation of Mitral Valve Coaptation Area With Tenting Height, Tenting Area and Tenting Volume. J Cardiothorac Vasc Anesth. 2023;37(1):8-15. doi:10.1053/j.jvca.2022.10.003.

Jainandunsing JS, Massari D, Vos JJ, Wijdh-den Hamer IJ, van den Heuvel AF, Mariani MA, Mahmood F, Bouma W, Scheeren TWL. Mitral Valve Coaptation Reserve Index: A Model to Localize Individual Resistance to Mitral Regurgitation Caused by Annular Dilation. J Cardiothorac Vasc Anesth. 2022 Nov 13:S1053-0770(22)00798-4. doi: 10.1053/j.jvca.2022.11.009. Epub ahead of print. PMID: 36509635.