Afterload mismatch after MitraClip insertion for functional mitral regurgitation

Afterload mismatch, defined as acute impairment of left ventricular function after mitral surgery, is a major issue in patients with low ejection fraction and functional mitral regurgitation (FMR). Safety and efficacy of MitraClip therapy have been assessed in randomized trials, but limited data on its acute hemodynamic effects are available. This study aimed to investigate the incidence and prognostic role of afterload mismatch in patients affected by FMR treated with MitraClip therapy. We retrospectively analyzed patients affected by FMR and submitted to MitraClip therapy from October 2008 to December 2012. Patients were assigned to 2 groups according to the occurrence of the afterload mismatch: patients with afterload mismatch (AM+) and without afterload mismatch (AM-). Of 73 patients, 19 (26%) experienced afterload mismatch in the early postoperative period. Among preoperative variables, end-diastolic diameter (71 ± 8 vs 67 ± 7 mm, p = 0.02) and end-systolic diameter (57 ± 9 vs 53 ± 7 mm, p = 0.04) were both significantly larger in AM+ group. An increased incidence of right ventricular dysfunction (68% vs 31%, p = 0.049) and pulmonary hypertension (49 ± 10 vs 40 ± 10 mm Hg, p = 0.0009) was found in AM+ group. Before hospital discharge, left ventricular ejection fraction (LVEF) became similar in both groups (31 ± 9% vs 33 ± 11%, p = 0.65). Long-term survival was comparable between the 2 groups (p = 0.44). A low LVEF in the early postoperative period (LVEF <17%) was significantly associated with higher mortality rate in long-term follow-up (p = 0.048). In conclusion, reduction of mitral regurgitation with MitraClip can cause afterload mismatch; however, this phenomenon is transient, without long-term prognostic implications.