Septal myomectomy and mitral valve replacement for idiopathic hypertrophic subaortic stenosis: short- and long-term follow-up.

The long-term results of septal myotomy-myomectomy or mitral valve replacement, or both, were assessed in 36 patients with idiopathic hypertrophic subaortic stenosis who were followed up for 5 to 67 months (mean 48) postoperatively. The mean left ventricular outflow tract gradient at rest decreased postoperatively in all three patient groups. It decreased from 60 mm Hg (range 17 to 160) preoperatively to 3 mm Hg (range 0 to 20) postoperatively (p less than 0.001) in the 13 patients who underwent mitral valve replacement alone, from 69 mm Hg (range 18 to 140) to 35 mm Hg (range 20 to 50) (p less than 0.05) in the 12 patients who underwent myotomy-myomectomy alone and from 89 mm Hg (range 60 to 165) to 3.8 mm Hg (range 0 to 27) (p less than 0.001) in the 11 patients who underwent myomectomy plus mitral valve replacement. The reduction in gradient was more impressive after mitral valve replacement with or without septal myotomy-myomectomy than after septal myotomy-myomectomy alone. There was a marked reduction in symptoms after all three surgical procedures that was long-lasting and independent of the type of operation performed. There was no operative mortality. Postoperative annual mortality rate was 1.6%. Patients with severe congestive heart failure, significantly elevated left ventricular end-diastolic pressure and atrial fibrillation have a less favorable long-term postoperative prognosis. Septal myotomy-myomectomy is recommended as the procedure of choice for the majority of patients with idiopathic hypertrophic subaortic stenosis who require surgery, because it can alleviate symptoms without subjecting patients to the complications of a valve prosthesis.(ABSTRACT TRUNCATED AT 250 WORDS)