Round Valve in an Oval Hole

Progressive narrowing of the aortic valve orifice eventually leads to limitations in cardiac output and myocardial blood flow, particularly during exercise or other physiological stress. The pressure gradient across the stenotic aortic valve is a useful and reproducible measure of the severity of the stenosis in most patients. The mainstay of therapy for aortic stenosis is relief of the fixed obstruction that has traditionally been accomplished with surgical aortic valve replacement (SAVR). However, during the past decade, transcatheter aortic valve replacement (TAVR) has rapidly evolved as an alternative therapy. Despite improvements in valve design and delivery, all prostheses are hemodynamically inferior to healthy native valves and, therefore, valve replacement results in the exchange of de novo valve disease for prosthetic valve disease. Because the gradient across most prosthetic valves is directly related to their size, a paradigm of aortic valve surgery is to implant the largest valve possible to minimize the transvalvular pressure gradient and maximize the ability to generate increased cardiac output in times of increased demand.