Surgical indications in children with subaortic stenosis, frequency and risk factors for restenosis, aortic regurgitation and reoperation

Subaortic stenosis accounts for 8-20% of left ventricular outflow tract obstruction. An important clinical feature of subaortic stenosis is being a progressive and repetitive pathology. Abnormal geometry of left ventricular outflow tract, genetic predisposition, increased septal flow stress and response of abnormal cellular proliferation are significant for the development of the subaortic stenosis. If severe form of subaortic stenosis is untreated, it may result in aortic valve injury, left ventricular hypertrophy and dysfunction, heart failure, ventricular arrhythmia and infective endocarditis. The surgical indications, risk factors for aortic regurgitation, restenosis, and reoperation are contraversial. Even after a successful operation, reoperation rate is high. Aim of this study is to evaluate incidence and risk factors of restenosis, aortic regurgitation and reoperation. The results of this study may serve to clarify surgical indications The study included 188 patients who have been operated for subaortic stenosis between January 1995 and December 2007 and who have fulfilled the study criteria. Echocardiography and catheterization data and surgical notes were reviewed from medical records of patients. Physical examination, echocardiographic and laboratory assessments were repeated in 134 patients during the study interval. Discrete subaortic membrane was found in 59% and fibromuscular ridge in 38% of the patients. The mean age at operation was 5.79±4.18 years. Aortic regurgitation was present in 53.2 % of the patients before the operation. The most common surgical indications consisted of correction of associated cardiac anomalies and high left ventricular outflow gradient. Seventy eight patients underwent resection of membrane and 106 patients had septal myectomy. Left ventricular outflow tract gradient declined to 10.4±11.2 from iv 48.5±32.2 mmHg (P<0.001) after surgery. Two patients developed significant aortic regurgitation, three had complete heart block and three had insignificant iatrogenic ventricular septal defect during initial surgery. The patients were followed for a mean of 5.51±3.68 years. 22 (11.7 %) patients had significant aortic regurgitation and 31 (16.5%) had restenosis. After 4.4±3.6 years of follow-up, 22 (11.7%) patients required reoperation. Additionally, two patients underwent second reoperation. There was significant correlation between immediate postoperative left ventricular outflow tract gradient and the gradient at last control (r=0.73, P<0.001). Aortic regurgitation was detected in 126 (73.2%) patients at last echocardiographic examination. Small aortic annulus, preoperative left ventricular outflow tract echo gradient, left ventricular peak systolic pressure, catheter gradient, postoperative echo gradient at one month, secondary subaortic stenosis, postoperative echo gradient ≥10 mmHg, isolated discrete subaortik stenosis and type of the stenosis were related to restenosis. Age at surgery, left ventricular peak systolic pressure, catheter gradient, preoperative echo gradient, postoperative echo gradient at one month, long follow-up period, aortic valve thickening, balloon aortic valvuloplasty, aortic valve reconstruction and secondary subaortic stenosis were associated with aortic regurgitation. Small aortic annulus, preoperative left ventricular outflow tract gradient, left ventricular peak systolic pressure, catheter gradient, immediate postoperative echo gradient, and gradient at one year, isolated discrete subaortik stenosis, type of the stenosis and relation of the subaortic stenosis to the mitral valve were associated with reoperation. The rate and severity of aortic regurgitation increased during follow-up. In conclusion children with mild stenosis and mild aortic regurgitation may be followed up without surgery. However the increased risk of restenosis with high preoperative gradients should be kept in mind.