An unusual cause of low-flow, low-gradient severe aortic stenosis: left-to-right shunt due to atrial septal defect.

Paradoxical low-flow, low-gradient severe aortic valve stenosis (AVS) may occur despite preserved left-ventricular (LV) ejection fraction in older females with marked LV concentric remodeling and small LV cavity size or in patients with coexisting severe mitral regurgitation. This report illustrates the case of a paradoxical low-flow, low-gradient severe AVS despite preserved LV function related to an ostium secundum atrial septal defect (ASD) in a patient presenting with congestive heart failure. Left-to-right shunt ASD that lowers forward LV stroke volume translating into lower transvalvular gradients is an underrecognized cause of paradoxical low-flow, low-gradient severe AVS. In addition, if not detected before open-heart surgery, ASD may result in cardiopulmonary bypass life-threatening complications.