Normal-Flow Low-Gradient Severe Aortic Stenosis: Myth or Reality?

ABSTRACT

The most prevalent form of “low-gradient” aortic stenosis (AS) is characterized by the concomitant presence of a small aortic valve area (<1.0 cm²) and a low mean gradient (<40 mmHg) but with preserved LV ejection fraction (≥50%) and normal flow (stroke volume index ≥ 35 mL/m²). This intriguing pattern referred to as “normal-flow, low-gradient” (NF-LG) AS is a matter of debate. Some studies suggest that this NF-LG pattern is a moderate form of AS, whereas others report that about half of these patients actually have true severe AS and thus benefit from aortic valve replacement (AVR). The purpose of this article is to provide an overview of the pathophysiology, diagnosis workup, and therapeutic management of NF-LG AS. This pattern of AS may occur as a result of normal stroke volume but reduced mean transvalvular flow rate, reduced arterial compliance and systolic hypertension, and/or incongruity in the aortic valve area and mean gradient severity cut-points. The key steps in the management of NF-LG AS are: (1) rule out measurement errors; (2) assess the presence of symptoms; (3) confirm stenosis severity using dobutamine or preload stress echocardiography or aortic valve calcium scoring by multi-detector computed tomography (MDCT); and (4) select the type of AVR depending on the assessment of surgical risk.

KEYWORDS:

• Aortic stenosis
• aortic valve replacement
• computed tomography
• echocardiography
• low flow
• low gradient

Acknowledgments

PP holds the Canada Research Chair in Valvular Heart disease and his research program is funded by a Foundation grant (FDN-143225) from the Canadian Institutes of Health Research (Ottawa, Ontario, Canada). MAC has received a research scholarship from Fond de Recherche en Santé du Québec.

Disclosure statements

PP received research contract from Edwards Lifesciences and Medtronic for echocardiography core laboratory analyses in the context of transcatheter aortic valve replacement trials. The other authors have no conflicts of interest.