Severe low-gradient aortic stenosis: impact of inadequate left ventricular responses to high afterload on diagnosis and therapeutic decision-making.

The fact that nearly 50% of patients with an aortic valve (AV) area < 1.0 cm2, consistent with severe aortic stenosis (AS), can have mean trans-AV pressure gradients < 40 mmHg, consistent with non-severe AS, indicates that "low-gradient" (LG) severe AS, which is often associated with poor prognosis, deserves particular consideration. Inadequate left ventricular (LV) adaptation to severe AV stenosis resulting from preexistent intrinsic myocardial damages and/or maladaptive LV responses to increased afterload are typical features of severe LG-AS. The diagnosis and management of patients with severe LG-AS are particularly challenging because the discrepancy between the AV area and the trans-AV pressure gradient raises doubts concerning the actual severity of AS and therefore also about the necessity of AV replacement (AVR). LG-AS diagnosis requires integrative multimodality evaluation of both the AV and the LV and therapeutic decision-making necessitates careful individual benefit-risk estimation. Although patients with severe LG-AS associated with low trans-AV flow (i.e., stroke volume ≤ 35 ml/m2) have worse outcomes after AVR than those with high-gradient severe AS, even those with reduced LV ejection fraction (LVEF) can have a significant survival benefit particularly by transcatheter AVR. Dobutamine stress echocardiography facilitates distinction between true-severe and pseudo-severe low-flow LG-AS with reduced LVEF. The review aimed to provide an updated theoretical and practical basis for those engaged in this demanding and still current topic due to the new aspects which have emerged in conjunction with both the evolving scientific knowledge about the various LV responses to the increased afterload and the increasing use of the less invasive transcatheter AVR.