Modified Konno operation for diffuse subaortic stenosis.

The modified Konno operation is designed to provide relief of diffuse subaortic stenosis, while preserving the native aortic valve. The aorta and the right ventricular infundibulum are opened. The upper part of the subaortic stenosis is incised through the aortic orifice. The conal septum is incised and the septotomy is extended across the stenotic area. The obstructive tissue is removed (mainly from the left-handed rim of the septotomy) and the conal septum is enlarged with a prosthetic patch. The aorta is closed and the right ventricular infundibulum is enlarged. Early and late mortality rates are low. Potential morbidity (complete heart block, residual ventricular septal defect, iatrogenic aortic insufficiency, right ventricular outflow tract obstruction) should be minimized by a careful surgical technique. The modified Konno operation is indicated in patients with diffuse subaortic stenosis and a normal aortic orifice; this includes patients with severe forms of hypertrophic obstructive cardiomyopathy and children with tunnel subaortic stenosis and a normal aortic orifice; the modified Konno procedure provides long-lasting relief of the obstruction. In patients with tunnel stenosis and a borderline-sized aortic annulus, residual obstruction may develop at the valvar level and need reoperation; the modified Konno operation can, however, delay aortic valve replacement.