‘Primary’ percutaneous mitral valve repair in patients with acute myocardial infarction: is it ready for primetime?

This editorial refers to ‘Conservative, surgical, and percutaneous treatment for mitral regurgitation shortly after acute myocardial infarction’, by D. Haberman et al., https://doi.org/10.1093/eurheartj/ehab496. Functional mitral regurgitation (FMR) is commonly observed in patients with ischaemic cardiomyopathy.1 FMR results from progressive left ventricular remodelling and papillary muscle displacement, leading to leaflet malcoaptation and MR. The literature is uniformly consistent showing that both the presence and degree of FMR are associated with an increased risk of mortality and morbidity in patients with ischaemic cardiomyopathy. Patients with an effective regurgitant orifice ≥20 mm2 and/or a regurgitant volume ≥30 mL are those with the worse prognosis,2 , 3 although the definition of severe FMR remains debated.4 , 5 Despite its undebatable association with a worse outcome, the beneficial impact of FMR correction is disputed. Two randomized control trials (RCTs) have evaluated the benefit of surgical correction of FMR and have shown no benefit, with a high rate of MR recurrence after surgical mitral valve repair.6 , 7 The contradictory results of transcatheter therapies in the MITRA-FR and COAPT trials have generated much controversy. Our understanding of the results of these two trials is that percutaneous edge to edge repair is beneficial in selected patients with severe FMR who remained symptomatic despite guideline medical therapy, but precise criteria to identify these patients remain to be defined. In this issue of the European Heart Journal, Haberman and colleagues tackle the benefit of mitral valve interventions (both surgical and percutaneous) in a completely different setting, i.e. in patients who present with acute myocardial infarction (MI).8 In this multicentre international registry (International Registry of Mitraclip in Acute Mitral Regurgitation following acute myocardial infarction; IREMMI), the authors have collected 471 patients who presented with 3+ or 4+ MR within 90 days after acute MI between 2009 and 2020 in 21 centres in North America, Europe, and the Middle East. Importantly, 46 patients who presented with a mechanical complication (papillary muscle rupture) were excluded. Mean age was 73 years, with a male predominance. Clinical presentation was often severe, with 50% in Killip class ≥3, 24% on mechanical ventilation, 35% in cardiogenic shock, and 49% receiving mechanical support (intra-aortic balloon pump, extracorporeal membrane oxygenation, or a mechanical support device). Mean left ventricular ejection fraction (LVEF) was only mildly reduced (40%), although LVEF is likely to overestimate left ventricular function due to the presence of severe MR. In-hospital and 1-year mortality rates were high, 20% and 36%, respectively. As expected, age, Euroscore II, anterior wall involvement, Killip class ≥3, LVEF, cardiogenic shock, mechanical ventilation, and use of a mechanical support device were significantly associated with mortality. Among these 471 patients, 266 patients were conservatively managed and 205 underwent a mitral valve intervention. Both in-hospital and 1-year mortality were significantly lower in the intervention group than in the conservative group (11% vs. 27% and 16% vs. 35%, respectively). Baseline characteristic were markedly different between the two groups, but overall clinical presentation was worse in the intervention group than in the conservative group. After multivariate adjustment and in a matched cohort analysis, mitral valve intervention was associated with a better survival. Among the 205 patients who underwent a mitral valve intervention, mitral valve surgery was performed in 106 patients and percutaneous mitral valve repair in 99 patients. Surgery was performed at a median of 12 days after the MI, and the percutaneous mitral valve repair at a median of 19 days. The immediate procedural success rate was high and similar between the two types of intervention (92% and 93%, respectively). More procedural complications were observed after surgery than with percutaneous interventions (34% vs. 6%, P < 0.001). Patients who underwent a percutaneous mitral valve repair were overall sicker, but percutaneous mitral valve repair was associated with a better outcome than surgery in multivariate analysis as well as in the matched cohort. Importantly, a coronary artery bypass graft was performed concomitant to the mitral valve surgery in 82% of patients. The overall conclusion of the present study is that mitral valve intervention improves outcomes, and that percutaneous mitral valve repair performs better than surgery. The present study adds to the growing literature suggesting that percutaneous mitral valve intervention appears feasible and safe in patients in cardiogenic shock or who are critically ill, and might be beneficial.9 , 10 A steady increase in the use of percutaneous mitral valve repair has been observed in recent years, but use of the procedure remains extremely low in this setting (<1% of all cardiogenic shock in the USA).11 The authors should be commended for gathering such a large series, but critical limitations should be mentioned. Firstly, this is a retrospective observational study with inherent bias, and consecutive inclusion of the population could not be established. In this regard, the low number of patients collected (two patients/year/centre) is surprisingly low for large tertiary centres, suggesting a possible selection bias. Secondly, although the authors enrolled a series of patients after acute MI, the setting was unclear, and the population was very heterogenous. Patients were enrolled after both ST-segment elevation MI (STEMI) and non-STEMI presentations, and it is unclear if the MR was acute or chronic in the setting of ischaemic cardiomyopathy with a recent admission for recurrent MI. Clinical presentation was highly variable and probably included stable patients with well-tolerated MR to critically ill patients in refractory cardiogenic shock under a mechanical support device. Whether a similar benefit was observed across the full spectrum of clinical presentations was not assessed and is highly hypothetical. Thirdly, the clinical presentation of the groups (intervention vs. conservative management and surgery vs. percutaneous) was greatly different and patients were possibly conservatively managed because they were poor surgical candidates. Multivariate and matched analyses were performed in an attempt to adjust for these differences, but confounders cannot be excluded. Fourthly, the vast majority of patients referred for surgery underwent concomitant coronary artery bypass grafting, while patients with prior coronary artery bypass grafting predominantly underwent percutaneous mitral valve intervention. It is likely that the need for revascularization, which was not accounted for in the present study, played a major role in both the need for and type of intervention. Finally, patients were collected over more than a decade, and therapeutic options and approaches have changed over the years. Although not specified by the authors, percutaneous mitral valve repair was mainly performed in the last few years. In summary, the take-home message of this study is that mitral valve intervention and, more specifically, percutaneous mitral valve repair might be beneficial and should be considered in patients presenting with acute MI and 3+/4+ MR. The retrospective observational design of the study, the heterogeneous clinical presentation of the population enrolled, and the marked differences between the patients who were conservatively managed and those who underwent a mitral intervention, which could not be fully eliminated by any statistical methods, preclude a formal conclusion on the benefits of mitral valve intervention. Thus, the results of the study should only be seen as hypothesis-generating and it is now time to design large multicentre RCTs in well-defined populations and settings, with centralized evaluation of MR severity, MR mechanisms, and clinical endpoints to compare two strategies: conservative management vs. percutaneous mitral valve repair (Graphical Abstract). Conflict of interest: D.M.-Z. has received consultant fees and research grants from Edwards Lifesciences outside the submitted work. B.H. has received funding as a clinical trial investigator from Abbott, Boston Scientific, and Edwards Lifesciences, outside the submitted work. V.C. has no relevant relationships to disclose. The opinions expressed in this article are not necessarily those of the Editors of the European Heart Journal or of the European Society of Cardiology.

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