608 The VCX Index: a novel haemodynamic quantification of mitral regurgitation
Authors: Leone Antonio Maria , Di Giusto Federico , Lucarelli Katya , Migliaro Stefano , Anastasia Gianluca , Galante Domenico , Petrolati Edoardo , Lombardo Antonella , Graziani Francesca , Locorotondo Gabriella , Lillo Rosa , Troisi Federica , Grimaldi Massimo , Trani Carlo , Crea Filippo 
Published: December 2021

Abstract
Percutaneous edge-to-edge mitral valve (MV) repair is extensively used in different pathological MV conditions. Randomized controlled trials have evaluated the role of this technique in both primary (organic) and secondary (functional) mitral regurgitation (MR). Furthermore, recent analyses of these studies have shown the relevance of echocardiographic patient selection in the functional setting of MR, differentiating proportionate MR from disproportionate MR according to the degree of the effective regurgitant orifice area (EROA) related to the left ventricular volume.
The haemodynamic impact of MR cannot be univocally measured by echocardiography alone and the aim of our study was to determine how invasive LAP monitoring during percutaneous edge-to-edge MV repair can predict long-term procedural success on top of the echocardiographic assessment by introducing the VCX INDEX and identifying haemodynamic variables with direct influence on filling pressures. The VCX INDEX, reflecting the impact of MR, is calculated by dividing the difference between v wave (ventricular systole in the left atrial pressure, LAP, or in the pulmonary capillary wedge pressure, PCWP, waveform) and the mean minimum LAP or mean minimum PCWP (mean between minimum LAP or minimum PCWP, x wave, and a/c wave) by systolic arterial pressure (SAP): (v wave – mean minimum LAP or mean minimum PCWP)/SAP.
85 patients at our centres underwent invasive intracardiac pressure monitoring either measuring LAP during percutaneous edge-to-edge MV repair or PCWP during right heart catheterization. Median VCX INDEX was 0.1 (Q1 0.05, Q3 0.16). The study population was further analysed according to the echocardiographic aetiology of MR: in the organic MR subgroup median VCX INDEX was 0.08 (Q1 0.05, Q3 0.14), in the functional proportionate MR subgroup median VCX INDEX was 0.07 (Q1 0.03, Q3 0.13) and in the functional disproportionate MR subgroup median VCX INDEX was 0.11 (Q1 0.06, Q3 0.19).
20 patients were deemed inoperable by the Heart Team and no further intervention was performed, while 65 patients underwent percutaneous edge-to-edge MV repair with MitraClip device and VCX INDEX was recalculated after the procedure. Median post-MitraClip VCX INDEX was 0.04 (Q1 0.02, Q3 0.07) and a subanalysis based on the echocardiographic MR aetiology was repeated: median post-MitraClip VCX INDEX was 0.02 in the organic MR subgroup (Q1 0.01, Q3 0.05), 0.03 in the functional proportionate MR subgroup (Q1 0.02, Q3 0.07) and 0.05 in the functional disproportionate MR subgroup (Q1 0.03, Q3 0.07). Median VCX INDEX in patients who did not undergo MitraClip implantation was 0.07 (Q1 0.04, Q3 0.12).
The variation of VCX INDEX when comparing pre- and post-procedural invasive pressure assessment gives an insight of MitraClip’s favourable haemodynamic effect in terms of VCX INDEX reduction in the treated subgroup of the study and how the intervention has a comparable haemodynamic impact between different echocardiographic MR aetiologies. Further studies are needed to explore the incremental diagnostic role in the decision-making process as well as the prognostic value of the VCX INDEX in patients undergoing percutaneous edge-to-edge MV repair.