Mid-Term Outcomes of Mitral Valve Annuloplasty in Type I versus Type IIIb Functional Mitral Regurgitation

Introduction: Functional mitral regurgitation (FMR) represents a heterogeneous clinical entity and the impact of different pathophysiological mechanisms (i.e., type I vs. type IIIb) on long-term outcome has not been analyzed yet. The aim of our study was to evaluate the outcomes of mitral valve annuloplasty in patients with type I versus type IIIb FMR.

Methods: We retrospectively identified consecutive FMR patients who underwent mitral valve annuloplasty during a period of 3 years (2014–2016) from our institutional mitral valve database. Preoperative tenting parameters (i.e., tenting height, tenting area, PML and AML angle, interpapillary muscle distance) were assessed quantitatively. All patients who underwent additional leaflet maneuvres were excluded. We subdivided our study cohort into type I FMR subgroup (n = 80) and type IIIb FMR subgroup (n = 40) based on the severity of tenting parameters, considering the cutoff value of tenting area at 3.0 cm². Follow-up protocol (mean follow-up of 17 ± 10 months) consisted of structured clinical questionnaire and recording of echocardiographic findings.

Results: A total of 120 patients (mean age 67 ± 10 years, mean STS 2.5 ± 2.2%) underwent an isolated mitral valve annuloplasty due to FMR during the study period. Concomitant surgeries were performed in 58% patients (n = 70). Mean preoperative left ventricular ejection fraction was 46 ± 12%. Overall survival and freedom from adverse cardiac events were 88.3 and 87.5% in the whole study cohort, respectively. Severe recurrent mitral regurgitation (MR) was found in 16 patients (13.3%).

Post hoc comparison of type I FMR versus type IIIb FMR subgroups revealed similar in-hospital (96.3 vs. 95.0%, p = 0.7) and late survival (88.8 vs. 87.5%, p = 0.8). There was an increased tendency to experience an adverse cardiac event during follow-up in type IIIb FMR versus. type I FMR patients (15.0 vs. 11.25%, p = 0.3). The proportion of patients with severe MR tended to be higher in type IIIb FMR patients (17 vs. 8.3%, p = 0.2).

Conclusion: Our study demonstrates that standard annuloplasty results in an acceptable clinical and echocardiographic outcome in type I FMR patients. However, patients with type IIIb FMR showed tendency toward increased prevalence of adverse cardiac events and higher recurrence rates of severe MR compared with patients with type I FMR. To optimize the outcome of these patients, additive operative strategies such as subannular maneuvers should be strongly considered.