Classification of Aortic Stenosis by Flow and Gradient Patterns Provides Insights into the Pathophysiology of Disease

Area of Science:

• Cardiology
• Medical Imaging
• Valvular Heart Disease

Background:

• Aortic stenosis (AS) severity assessment can be challenging due to varying flow and gradient patterns.
• Distinguishing true AS severity requires understanding these hemodynamic variations.

Purpose of the Study:

• To investigate the relationship between aortic valve calcification (AVC), flow patterns, and gradients in severe AS.
• To differentiate subgroups within severe AS, particularly low-gradient, low-flow AS with preserved ejection fraction.

Main Methods:

• Echocardiography and computed tomography were used in 181 patients with severe AS (valve area <1 cm(2)).
• Patients were categorized into four groups: high-gradient/normal flow (HGNF), high-gradient/low flow (HGLF), low-gradient/normal flow (LGNF), and low-gradient/low flow (LGLF).
• Aortic valve calcification (AVC) was quantified using the Agatston score; low flow was defined as stroke volume index <35 mL/m(2), and low gradient as mean aortic gradient <40 mm Hg.

Main Results:

• Significant differences in median AVC (2048, 2015, 1366, 1178 AU/m(2)) and valvuloarterial impedance (4.5, 6.4, 4.2, 5.9) were observed across the four groups (P < .0001).
• In the low-gradient, low-flow (LGLF) AS group, patients with preserved ejection fraction had lower AVC (1018 AU/m(2)) compared to those with reduced ejection fraction (2550 AU/m(2); P < .0001).
• Valvuloarterial impedance was similar between LGLF subgroups with preserved versus reduced ejection fraction (P = .33).

Conclusions:

• Low-gradient, low-flow AS with preserved ejection fraction is associated with lower aortic valve calcification.
• This subgroup may represent a less severe form of AS, potentially reflecting an adaptive ventricular response to high afterload.
• Further research is needed to confirm the clinical implications for treatment decisions.