Mitral Regurgitation in Patients With Hypertrophic Obstructive Cardiomyopathy: Implications for Concomitant Valve Procedures

Background Incidence and outcome of mitral valve (MV) surgery are unknown in patients with hypertrophic obstructive cardiomyopathy (HOCM) undergoing extended transaortic septal myectomy. Objectives This study sought to define indications and suitable operative strategy for mitral regurgitation (MR) in patients with HOCM. Methods A total of 2,107 septal myectomy operations performed in adults from January 1993 to May 2014 at Mayo Clinic in Rochester, Minnesota, were retrospectively reviewed. Patients with prior MV operation and apical hypertrophic cardiomyopathy were excluded. Overall, 2,004 operations were performed in 1,993 patients. Results Pre-operative MR was grade ≥3 (of 4) in 1,152 operations (57.5%). Systolic anterior motion of mitral leaflets caused the MR in most patients. However, intrinsic MV disease was identified pre-operatively in 99 patients, all of whom had MV surgery (with septal myectomy). In 1,905 operations, no intrinsic MV disease was identified pre-operatively; in 1,830 (96.1%), septal myectomy was performed without a direct MV procedure. For 75 patients, intrinsic MV disease discovered intraoperatively led to concomitant MV repair (86.7%) or replacement (13.3%). After isolated septal myectomy, the percentage of patients with MR grade ≥3 decreased from 54.3% to 1.7% (p = 0.001) on early post-operative echocardiography. Among 174 patients with concomitant MV surgery, late survival was superior with MV repair (n = 133 [76.4%]) versus replacement (10-year survival: 80.0% vs. 55.2%; p = 0.002). Conclusions In most patients with HOCM, MR related to systolic anterior motion of the MV is relieved through adequate myectomy. Concomitant MV surgery is rarely necessary unless intrinsic MV disease is present. When MV procedures are required, repair is preferred because of improved survival compared with replacement.