Subaortic Membrane Late after Surgical Correction of Tetralogy of Fallot
A 29-year-old woman presented for a routine check-up of surgically corrected congenital heart disease. At 7 years of age, she had undergone surgical repair of TOF with excision of the infundibular stenosis and closure of a 10-mm ventricular septal defect. She had been asymptomatic until her first decade of life, and only a 5-year clinical follow-up had been performed after the operation. Approximately 6 months prior to presentation, she began to feel exertional dyspnea that was progressively aggravated. On physical examination, she was alert and well-oriented. Her blood pressure was 100/60 mmHg, pulse 60 beats/min, respiration rate 18/min, and body temperature 36.6℃. The left ventricular (LV) impulse was almost normal in location. On auscultation, a grade 3 of 6 mid- to late-systolic murmur was audible over the base of the heart and heard clearly on both sides of the sternum. Routine blood examinations, including a complete blood count, chemistry panel, coagulation panel, and C-reactive protein level, were all within normal ranges. An electrocardiogram showed a sinus rhythm with nonspecific ST-T changes. Transthoracic and transesophageal echocardiograms both demonstrated severe subaortic stenosis due to a subvalvular membrane, on which a mobile mass-like structure that was suspicious of a vegetation was noted (). The peak pressure gradient across the subaortic membrane was 95.3 mmHg (). The aortic valve was trileaflet with associated mild aortic regurgitation. There was a mild degree of tricuspid regurgitation, but no clinically significant obstruction of the RV outflow tract. The maximum velocity measured across the tricuspid valve was 2.8 m/sec, and thus the maximal pressure gradient was estimated to be 31.4 mmHg using the simplified Bernoulli equation. Due to the up to 20 mmHg pressure gradient across the pulmonary valve, clinically relevant pulmonary hypertension was not expected. Her RV was not dilated, and its systolic function was good. Due to the suspicion of infective endocarditis despite the absence of clinical evidence, blood cultures were performed three times; however, no pathogen was cultured. The patient underwent resection of the subaortic membrane and myomectomy of the LV outflow tract along with aortic valve commissurotomy. shows the subaortic membrane from the surgeon's view. The membrane, with the exception of the noncoronary cusp area, was located beneath the aortic annulus (i.e., inverted U shape). The mobile mass-like structure described on transesophageal echocardiography was proven to be loose tissue attached to the subaortic membrane. The patient remains asymptomatic 18 months after surgery.