Pathoanatomic Findings and Treatment During Hypertrophic Obstructive Cardiomyopathy Surgery: The Role of Mitral Valve

Background: To assess the role of the mitral valve apparatus (leaflets, chordae and papillary muscles, PM) in left ventricle outflow tract (LVOT) obstruction, and results of the surgical treatment for hypertrophic obstructive cardiomyopathy (HOCM). Methods: Twenty-eight consecutive patients (58 ± 11 years, 53% female) undergoing HOCM surgery from 2007 to 2016 at our institute were retrospectively reviewed. Endpoints included the involvement of the mitral valve in LVOT obstruction, mortality, and changes in clinical and echocardiographic characteristics after HOCM surgery. Results: Secondary chordae tendineae tractioning the anterior mitral leaflet to the interventricular septum, and systolic anterior motion were detected in 78% of the patients. Anomalous, hypertrophied, and fused PM with muscularis trabeculae hypertrophy were found in 50%, 25%, and 35% of the patients, respectively. Four patients had posterior leaflet redundancy. Secondary chordae (92%), PM, and muscularis trabeculae resection (71%), and PM splitting and elongation (28%) were added variably to septal myectomy (100%). Nine procedures (32%) on mitral valve leaflets were performed, involving six posterior and three anterior mitral leaflets. Long-term follow-up was 4 ± 2.8 years. There was no hospital mortality, and NYHA was reduced from 3 ± 0.5 to 1 ± 0.7 (p < 0.0001), the LVOT gradient from 88 ± 35 to 20 ± 18 mmHg (p < 0.0001), mitral valve regurgitation from grade 3 ± 1 to 1 ± 0.7 (p < 0.0001), and septum thickness from 18 ± 3 to 14 ± 2 mm (p < 0.0001). Conclusions: The mitral valve apparatus contributes with all its components variably to LVOT dynamic obstruction thus surgical correction in addition to extended myectomy is recommended to achieve the best outcome.