Multimodality Imaging for Discordant Low-Gradient Aortic Stenosis: Assessing the Valve and the Myocardium

Abstract

Aortic stenosis (AS) is a disease of the valve and the myocardium. A correct assessment of the valve disease severity is key to define the need for aortic valve replacement (AVR), but a better understanding of the myocardial consequences of the increased afterload is paramount to optimize the timing of the intervention. Transthoracic echocardiography remains the cornerstone of AS assessment, as it is universally available, and it allows a comprehensive structural and hemodynamic evaluation of both the aortic valve and the rest of the heart. However, it may not be sufficient as a significant proportion of patients with severe AS presents with discordant grading (i.e., an AVA ≤ 1 cm2 and a mean gradient <40 mmHg) which raises uncertainty about the true severity of AS and the need for AVR. Several imaging modalities (transesophageal or stress echocardiography, computed tomography, cardiovascular magnetic resonance, positron emission tomography) exist that allow a detailed assessment of the stenotic aortic valve and the myocardial remodeling response. This review aims to provide an updated overview of these multimodality imaging techniques and seeks to highlight a practical approach to help clinical decision making in the challenging group of patients with discordant low-gradient AS.

Peak flow measurements in patients with severe aortic stenosis: a prospective comparative study between cardiovascular magnetic resonance 2D and 4D flow and transthoracic echocardiography

“…Such averaging phenomenon has been observed in pulmonary arteries, where considerable spread in the peak velocity values has been obtained by CMR 4D flow [ 29 ]. An interesting patient group that potentially benefits from multimodality imaging is low flow—low gradient AS [ 30 ]. Due to the low number of these patients in our material (n = 4), statistical analyses were not possible.…”

Aliased Flow Signal Planimetry by Cardiovascular Magnetic Resonance Imaging for Grading Aortic Stenosis Severity: A Prospective Pilot Study

“…Cardiovascular magnetic resonance (CMR) complements echocardiographic assessment of AS—e.g., by allowing planimetric measurement of the aortic valve area in systole (GOA cmr )—providing precise information in patients with reduced cardiac output or with conditions influencing the accuracy of flow velocities or pressure gradient measurement by TTE ( 7 , 8 ). CMR also allows direct measurement of LV stroke volume (without using geometrical assumptions) and of LVOT area, and is more accurate and reproducible than echocardiography ( 9 ), but, when compared to Doppler echocardiography, it underestimates flow velocities ( 6 ).…”