Subannular Repair for Functional Mitral Regurgitation Type IIIb in Patients with Ischemic versus Dilated Cardiomyopathy

Objectives: Due to geometric displacement of papillary muscles, functional mitral regurgitation (FMR) type IIIb is a common sequela of LV remodeling in various cardiomyopathies. Relocation of both papillary muscles in addition to ring annuloplasty specifically addresses mitral leaflet tethering to improve long-term competence. Nevertheless, the prognostic impact of the underlying LV disease on the outcome after subannular mitral valve repair remains unknown.

Methods: A prospective series of 57 patients with severe type-IIIb FMR, EF < 40%, LVEDD > 55 mm and tenting-height >  10 mm underwent ring annuloplasty and subannular repair. Thirty-six patients (63.2%) suffered from an ischemic cardiomyopathy (ICM-group), whereas 21 patients (36.8%) were categorized as dilated cardiomyopathy (DCM-group). Primary endpoints were death and the reoccurrence of MR ≥ 2 after 1 year. Secondary endpoints were periprocedural cardiac adverse events and echocardiographic outcome parameters.

Results: Mean age at the time of surgery was 63 ± 13.4 years, 35 patients (61.4%) were male. The severity of LV remodeling at baseline was comparable between the two study groups (LVEF 36 ± 9.4% ICM-group vs. 38 ± 11.8% DCM-group, p = 0.57; LVEDD 61 ± 8.5 mm ICM-group vs. 62 ± 11.7 mm DCM-group, p = 0.67). Due to concomitant CABG (63.9 vs. 0%; p < 0.001), full sternotomy was required more frequently in the ICM-group (i.e., 72.2 vs. 33.3%; p < 0.001). Therefore, the procedural time (i.e., 323 ± 89 min vs. 253 ± 48 min, p < 0.001) and postoperative ventilation time (15 ± 19.1 vs. 7 ± 5.2 hours; p = 0.048) was significantly increased in the ICM-group, whereas there was no in-hospital mortality in both study-groups. The number of patients preoperatively categorized as NYHA III/IV (80.1%) was significantly reduced 12-months after surgery (21.8%; p < 0.001). 1-year overall survival was 96.5% (55/57; [35/36] ICM-group vs. [20/21] DCM-group). MR ≥ 2 reoccurred in three patients in the DCM-group (14.2%), while no patient had recurrent MR >  2 in the ICM-group (p = 0.002). LV reremodeling (improvement of LVEF ≥ 10% from the baseline values) occurred in 37.1% in the ICM-group vs. 40% in the DCM-group (p = 0.06).

Conclusion: Standardized realignment of both papillary muscles to correct type IIIb FMR resulted in excellent in-hospital and 1-year outcomes, in both ischemic and dilated cardiomyopathy. Subannular repair represents a valid therapeutic option in heart-failure patients presenting with severe type IIIb FMR, independent of the type of the underlying cardiomyopathy.

No conflict of interest has been declared by the author(s).