Septal Myectomy

Hypertrophic cardiomyopathy is an inherited heart muscle disease in which the wall of the left ventricle, especially the upper part of the septum just below the aortic valve, becomes very thick. In the obstructive form the bulging septum narrows the path out of the ventricle (the left ventricular outflow tract), and as blood rushes past it the front leaflet of the mitral valve is pulled forward into the outflow (systolic anterior motion), which both adds to the blockage and makes the mitral valve leak. Patients have shortness of breath, chest pain, fainting and a risk of sudden death. Many respond to medicines, pacing or alcohol septal ablation, but for patients with severe symptoms despite treatment, surgical septal myectomy is the established treatment. What makes this operation distinct is that the work is done deep inside the ventricle through the aortic valve, with no valve being replaced. Through a low aortotomy the surgeon holds the aortic leaflets out of the way, makes two lengthwise cuts in the septum under the right coronary cusp (one below the commissure between the right and left cusps and one below the lowest point of the right cusp), joins them about 1 cm below the valve, and removes a long wedge of muscle down toward the bases of the papillary muscles. Abnormal muscle bundles, extra chords tied to the septum and papillary muscles fused to the wall are also cut, and the mitral valve is sometimes repaired at the same time. Good light (a headlight and loupes) and long instruments help. The risks are cutting too little (obstruction remains), cutting through the septum (a ventricular septal defect), heart block from injury to the conduction tissue, damage to the aortic or mitral valve, and muscle fragments falling into the ventricle and embolizing. TEE before and after bypass guides the resection, and the surgeon may go back on bypass to resect more.