Discrete membranous subaortic stenosis. Report of 31 patients, review of the literature, and delineation of management.

Abstract

The presentation, management, and follow-up of 31 patients with discrete membranous subaortic stenosis (DMSS) is presented. DMSS comprised 16% of 185 patients with congenital left ventricular (LV) obstruction. Only one patient was older than 40 years. The rarity of DMSS in older patients in both our population and in the literature is noted, and possible explanations are discussed. One-quarter of these patients had dyspnea, chest pain, or syncope combined with electrocardiographic left ventricular hypertrophy (LVH) and strain, and these all had peak LV outflow gradients (PSG) greater than 85 mm Hg. One-quarter had neither symptoms nor electrocardiographic abnormalities and all had PSG less than 90 mm Hg. Bacterial endocarditis was found in 13%, and in 13% an immediate family member also had congenital LV obstruction. Following surgical resection (25 patients), 18 were asymptomatic, two had residual fibromuscular obstruction, and four developed new fibromuscular obstruction after from one to six years (leading in one to late sudden death). Thus, even after resection, these patients require continued re-evaluation for residual or new LV obstruction.

Clinical presentation and natural history of mild discrete subaortic stenosis. Follow-up of 1--17 years.

“…The site of endocarditis may also be the subaortic obstruction itself. 3 -The incidence of subacute bacterial endocarditis in postoperative series is 0-4%,3 4, 7 9 21 These series include various degrees of obstruction.…”

ACC/AHA 2008 Guidelines for the Management of Adults With Congenital Heart Disease: Executive Summary

“…82 Patients are at risk for endocarditis, which will contribute to worsening AR. 84 Surgical intervention should be recommended for patients with SubAS when the peak instantaneous echocardiographic gradient is greater than 50 mm Hg, the mean gradient is greater than 30 mm Hg, or catheter measurement of the resting peak-to-peak gradient is greater than 50 mm Hg. Patients with lesser degrees of obstruction may be considered for surgery in the presence of LV systolic dysfunction or significant aortic valve regurgitation, or if the patient desires to become pregnant or to participate in active sports.…”

Left Ventricular Outflow Obstruction

“…12 However, in a series of 75 pediatric and adult patients who underwent surgical SAS resection at University of California at Los Angeles (UCLA), the severity of presenting symptoms did not correlate with the preoperative LVOT gradient but did correlate with the presence of a VSD in 54% of symptomatic patients. 1 Patients with SAS are at a high risk for developing infective endocarditis, which frequently involves the aortic valve 13,14 and often leads to aortic regurgitation. The aortic valve is in harm's way even in the absence of endocarditis.…”