Low-flow/low-gradient aortic stenosis-Still a diagnostic and therapeutic challenge

Aortic stenosis (AS) is the most frequently observed valvular heart disease. During the symptomatic stage, the rate of death increases dramatically, so that a precise diagnostic approach is taken to guide therapeutic options. Of patients with severe AS, 30% to 50% present with low-flow/low-gradient AS (LF/LGAS) status. This review focuses on LF/LGAS and the best diagnostic and therapeutic management in either classic LF/LGAS with reduced left ventricular ejection fraction (LVEF) or paradoxical LF/LGAS with preserved LVEF. Current literature demonstrates that in classic LF/LGAS it is crucial to rule out a pseudo-severe AS, because reduced LVEF may result in an incomplete opening of the valve. This can be done by low-dose dobutamine stress echocardiography. Classic LF/LGAS has poor clinical outcomes when managed conservatively; therefore, surgical or interventional aortic valve replacement should be performed. In paradoxical LF/LGAS, the LVEF is preserved (>50%), but impaired filling of the concentric hypertrophied ventricle leads to reduced stroke volume. Therefore, diagnostic and therapeutic decisions in paradoxical LF/LGAS are even more challenging. It is a heterogeneous disease entity, and it is crucial to rule out any diagnostic errors because numerous potential confounders might lead to misdiagnosis. As in classic stenosis, pseudo-severe stenosis must be ruled out as well. Evaluation via multidetector computed tomography or transesophageal echocardiography can help to evaluate the morphologic alterations of the valve (eg, calcification). Further studies are necessary to understand this disease entity and to evaluate the optimal diagnostic and therapeutic approach for these patients.