In cases where the narrowing is below the aortic valve (subvalvular stenosis) care is taken in this procedure to avoid damaging the aortic and mitral valves.

Unlike valvar aortic stenosis, subvalvular aortic stenosis is not successfully treated with balloon valvuloplasty. Instead, surgical resection or removal of the fibrous tissue is performed. For the repair,the surgeon usually enters the heart through the aortic valve and removes the obstructing tissue (see animation at left). In as many as 50% of cases, there will be some re-growth of the obstruction after surgery, so careful monitoring of the patient is necessary and the need for re-operation is relatively common as the ridge has been demonstrated to return.

Recovery after this operation is usually straightforward, requiring a typical postoperative hospital stay of 5 to 7 days.