Subaortic Membrane and Aorto-Septal Angle

Abstract

Background: Development of a subaortic membrane is not fully understood. Recurrence after surgical removal continues to be high. We sought to assess the differences in aorto-septal angles (AoSA) to possibly explain alterations within the left ventricular outflow tract, hence in subaortic membrane formation. Methods: A total of 113 patients who underwent subaortic membrane resection were matched by age and sex with 113 controls. The subaortic membrane resection group included isolated subaortic membranes (n = 34, group I), associated with ventricular septal defect (n = 29, group II), or patent ductus arteriosus (n = 50, group III). Results: Mean (± standard deviation) AoSA (in degrees) were not different between subaortic membrane groups I, II, and III but were steeper than their control groups (126.2 ± 9.2 vs 138.6 ± 7.0, 129.2 ± 9.9 vs 137.7 ± 10.0, and 126.2 ± 8.1 vs 135 ± 8.5, respectively; all Ps < .05). Additionally, group II had lower preoperative gradients (28.8 ± 20.7 mm Hg) compared to groups I and III (67.0 ± 32.9 and 66.2 ± 33.1 mm Hg, respectively, P < .001). Follow-up ranged from 3 to 132 months. In 22 (32%) patients, a subaortic membrane recurred. Early postoperative residual gradients and development of aortic regurgutation were associated with the need for reoperation ( P < .05). Conclusions: These findings suggest a contributing role of the AoSA in the development of subaortic membrane. Further rheological experiments are warranted. Whether the steeper the angle the higher the risk of recurrence may be revealed by longer follow-up periods.