Discrete subvalvar aortic stenosis after tetralogy of Fallot repair.

The development of discrete subvalvar aortic stenosis after repair of Fallot's tetralogy is most unusual and prompts this report. Kelly et al.,' in 1972, divided discrete subaortic stenosis into two distinct types. Type I is a 1 to 2 mm thick discrete membrane immediately under the aortic valve and type II is a thicker membrane 1 cm below the valve consisting of a fibrous ring and associated with muscular obstruction of the left ventricular outflow tract. Discrete subaortic stenosis is a progressive disease and there is some evidence that it may develop after birth.23 Up to 57% of patients have associated cardiac defects.2 The association of left sided obstructive lesions with Fallot's tetralogy is rare. The few reports of subaortic stenosis with Fallot's tetralogy have emphasised outflow obstruction from abnormalities of the mitral leaflets and chordae.4 We are aware of only one published case5 of discrete subvalvar aortic stenosis in a patient with Fallot's tetralogy similar to the patient to be reported. We recently treated a 6 year old girl who developed subvalvar aortic stenosis after repair of Fallot's tetralogy at 9 months of age. Preoperative cardiac catheterisation had shown fairly severe infundibular stenosis and a right to left shunt through the ventricular septal defect. There was no evidence of left ventricular outflow obstruction. At operation, excess infundibular muscle was excised, a patent foramen ovale was closed, and a large subaortic ventricular septal defect repaired with a woven Teflon patch. She did well after operation until 6 years of age when she developed decreased exercise tolerance. Follow-up cardiac catheterisation was recommended because of symptoms and the development of a thrill and an increase in intensity of a murmur along the left sternal border. A grade 4 harsh ejection systolic murmur was heard along the left sternal border and a grade 1 diastolic blow at the right base. There was mild cardiomegaly on x-ray examination and an electrocardiogram showed sinus rhythm, with complete right bundlebranch block. Left ventricular voltage was increased compared with previous electrocardiograms, but left ventricular hypertrophy was not apparent. At catheterisation, the right ventricular pressure was 32/10 mmHg, the left ventricular pressure was 220/14 mmHg, and aortic pressure was 96/56 mmHg, giving a 145 mmHg gradient on pullback from the left ventricle to the aorta. Injection into the right ventricle showed no evidence of residual infundibular stenosis. A left ventricular injection showed an intact septum and a discrete subaortic linear lucency typical of a