Functional Mitral Valve Regurgitation
Ischaemic MR is characterised by restrictive mitral leaflet mobility due to dyskinesia or akinesia of the ventricular wall involving one or both papillary muscles, thus, extending the distance between the ventricular wall and the leaflets. The posterior papillary muscle is the most frequently affected.
FMR is associated with a poor prognosis in heart failure patients with post-ischaemic or idiopathic dilated cardiomyopathy.3 Surgical MV repair may be considered in severely symptomatic patients with severe FMR despite optimal medical therapy and cardiac resynchronisation therapy.35,36 Although several studies have reported reverse LV remodelling and improvements in symptoms and quality of life after surgical mitral repair,36 operative mortality is not negligible, ranging from 8.8 % to 21.0 %.37 Moreover, there is a high number of patients with severe FMR who are not referred for surgery because of advanced age, high surgical risk and co-morbidities.8
Surgical Treatment
Historically, the surgical approach to patients with FMR was to perform MV replacement, but it had a high impact on LV systolic function and exerted high mortality rates. Techniques of MV replacement, such as prosthesis implantation with preservation of the subvalvular apparatus, and prosthesis implantation with preservation of one or both leaflets (usually posterior) have evolved to improve the long-term haemodynamic function and clinical status of these patients38 Replacement should be reserved for cases of acute papillary muscle rupture in relation to acute myocardial infarction.39 In appropriately selected patients, restrictive annuloplasty is associated with low operative mortality and is effective in eliminating MR.
Acker et al.40 have recently published the randomised comparison of MV repair versus replacement for severe ischaemic MR. At 12 months, the rate of death was 14.3 % in the repair group and 17.6 % in the replacement group (hazard ratio with repair, 0.79; 95 % confidence interval, 0.42–1.47; p=0.45), with an increased rate of moderate or severe recurrence of MR at 12 months in the repair group compared with the replacement group (32.6 % versus 2.3 %, p<0.001). Patient selection for repair is crucial. When the pre-operative clinical and echocardiographic data suggest that annuloplasty alone is unlikely to be successful and durable, additional surgical procedures should be used to enhance the effectiveness of MV repair.39
Since FMR exerts high mortality and high incidence of recurrence of MR after repair, several alternative treatments have been proposed.
Percutaneous Edge-To-Edge Repair
EVEREST II trial included 26 % patients with FMR randomised to surgery or Mitraclip treatment. Recently reported five-year data (EuroPCR2014) have shown that freedom from mortality in Mitraclip patients (n=48) and surgical patients (n=18) is comparable within aetiologies: FMR Mitraclip 59.7 % and FMR Surgery 55.0 %, compared with a 86.0–89.0 % survival for the DMR group. Moreover, 90 % of FMR patients treated with Mitraclip were free from MV surgery of re-operation at five years, compared with 81 % treated surgically. Durability of the Mitraclip repair was confirmed at five years follow-up, with 86 % of the patients in both groups with MV regurgitation grades 1+ or 2+. NYHA I/II functional class at five years was present in FMR in 76 % of the Mitraclip patients compared with 100 % of surgical survivors at five years. Mitraclip patients had comparable stability of mitral annular dimensions at five years compared to baseline (3.8 cm versus 3.7 cm, p=0.20).
Taramasso et al.41 have recently published the results of Mitraclip implantation in 109 consecutive patients with FMR and prohibitive surgical risk (logistic EuroSCORE [LogEuroscore] 22 ± 16 %). Mean ejection fraction (EF) was 28 ± 11 %; left ventricular end-diastolic diameter (LVEDD) was 68 ± 8 mm. Procedural success was 99.0 % and 30-day mortality was 1.8 %. At discharge, 87 % patients had MR ≤2+. At 12 months, EF was 34.7 ± 10.4 % (p=0.002 compared with pre-operative value). Actuarial survival at three years was 74.5 ± 7.0 %. Actuarial freedom from MR ≥3+ at 2.5 years was 70 ± 6 %. At one-year follow-up, 86 % of patients were in NYHA Class I-II. Pre-operative pro-B-type natriuretic peptide (pro-BNP) level ≥1,600 pg/ml was identified as an independent risk factor of mortality at follow-up.
Recently, the new European guidelines included the MitraClip as a treatment option in high-risk and inoperable patients with FMR and severe symptoms despite optimal medical therapy (class IIb indication with evidence C) (see Table 1).21, 42–44 In the EVEREST II high surgical risk cohort, a 44 % reduction of the annual rate of hospitalisations was observed (0.82–0.46, p=0.0004) after Mitraclip implantation.
After EVEREST II trial results (EuroPCR2014), including standard-risk patients, future guidelines may consider Mitraclip treatment as an option for FMR since it exerts sustained reduction of MR severity, sustained improvement in LV volumes and dimensions, and sustained improvement in NYHA functional class at five years, with low rates of conversion to MV surgery overall.