The Role of Cardiac MRI in Aortic Stenosis

Amina Elfhal *¹

*Correspondence to: Dr. Amina Elfhal, Professor Jérôme Garot, Paris South Cardiovascular Institute (ICPS) – MASSY, Paris-France.

              
Copyright.

© 2025 Amina Elfhal This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: 26  May 2025

Published: 01 July 2025

DOI: https://doi.org/10.5281/zenodo.15838113

Abstract:

Aortic stenosis is the most common valvular disease in Western countries, mainly affecting the elderly. Its prevalence increases with age, and it is now a real public health issue. Diagnosis is traditionally based on transthoracic echocardiography, which allows functional and hemodynamic assessment of the aortic valve. However, certain clinical situations make ultrasound interpretation difficult or uncertain, particularly in low-flow, low-gradient forms, parameter discrepancies, or poor acoustic windows.

In this context, cardiac magnetic resonance imaging (CMR) is emerging as an increasingly used modality. It allows for a comprehensive anatomical, functional, and tissue assessment of the heart, with the advantage of being non-invasive, radiation-free, and operator-independent. Its ability to characterize the myocardium, quantify flow, and analyze cardiac geometry makes it a particularly relevant tool in the management of patients with AS. This review aims to explore the various contributions of cardiac MRI in the assessment of aortic stenosis from initial diagnosis to post-intervention follow-up, including risk stratification and therapeutic planning.

1. Introduction

Aortic stenosis is the most common valvulopathy in developed countries. Assessment is mainly based on transthoracic echocardiography, but certain situations limit its reliability (low gradient shapes, low flow, suboptimal acoustic window). Cardiac MRI, as a non-invasive, reproducible method, without radiation or iodinated contrast, is becoming an essential modality.

2. Contribution of MRI in aortic stenosis

2.1 Aortic orifice planimetry

MRI allows direct measurement of the aortic valve area , by cine-MRI planimetry, often performed in a short-axis slice centered on the cusps . Unlike echocardiography, which relies on indirect measurements and is subject to angular variations, CMR provides high-resolution and isotropic imaging, allowing accurate planimetry, even in the case of a difficult acoustic window. This method is particularly useful in low-flow forms where ultrasound can underestimate the severity.

2.2 Morphological analysis

MRI provides excellent visualization of valvular anatomy. It allows identification of the bicuspid phenotype, cusp fusion , and valvular apparatus abnormalities. It also provides reliable data on the dimensions of the aortic annulus and the geometry of the left ventricle and aortic root, which is useful for planning procedures such as TAVI.

2.3 Flow quantification

 Phase-contrast flow MRI , usually acquired orthogonally to the transvalvular jet , allows direct measurement of flow velocity and flow rate. This technique is less sensitive to Doppler angle and allows a more robust calculation of stroke volume and aortic valve area according to the continuity equation. Dynamic analysis of flow through the valve, combined with the study of peak velocities, allows for the completion or even correction of ultrasound data, particularly in discordant cases (aortic valve area but moderate mean gradient).

3. Clinical applications of MRI

3.1 In complex or discordant forms

MRI helps differentiate true severe low-flow stenoses from falsely severe ones. It is an additional tool in the decision-making strategy in case of diagnostic doubt.

3.2 In preparation for an intervention

MRI allows the analysis of left ventricular function, planning of annulus size, and assessment of myocardial remodeling before TAVI or surgery.

3.3 Post-intervention follow-up

MRI is useful for assessing regression of hypertrophy, residual fibrosis, and detection of paravalvular leaks.

4. Tissue characterization and prognostic stratification

4.1 Myocardial fibrosis

Focal fibrosis (late enhancement) and interstitial fibrosis (T1 mapping and ECV) are validated prognostic markers. Their presence is associated with increased mortality and less reversibility post-aortic valve replacement.

4.2 Ventricular remodeling

MRI allows for precise analysis of volumes, myocardial mass, and strain . These parameters are used to determine the optimal timing of the intervention.

5. Limitations of MRI in aortic stenosis

Despite its advantages, cardiac MRI has certain limitations:

• temporal resolution than echocardiography, which may impair the analysis of rapid flows such as those observed in severe aortic stenosis.
• Movement artifacts, especially in cases of arrhythmias or uncooperative patients.
• Limited availability : MRI is not always readily available in all centers, and acquisition time can be a logistical constraint.
• Incompatibilities : some patients with devices (pacemakers not compatible with MRI) or with advanced renal failure may not be eligible.

6. Perspectives and innovations

Technological development opens new perspectives for MRI in aortic stenosis:

• Artificial intelligence and machine learning : to automate segmentation, flow quantification, or even the detection of myocardial fibrosis, saving time and reducing inter-operator variability.
• 4D Flow MRI : allows three-dimensional analysis of valvular and aortic flow, providing access to more complex hemodynamic parameters such as wall stress or areas of post-stenosis turbulence.
• Integration into risk stratification algorithms : in combination with clinical and biological data, MRI markers could ultimately guide individualized management.

Conclusion

Cardiac MRI plays a growing role in the assessment of aortic stenosis, providing precise information on anatomy, hemodynamic flow, ventricular remodeling, and myocardial fibrosis. Complementary to ultrasound, it is essential in low-flow or discordant forms, as well as in peri-interventional strategy. The tissue characterization capabilities of MRI allow for fine prognostic stratification, which can guide therapeutic decisions. With the rise of artificial intelligence and 4D MRI, its potential continues to grow, heralding an even greater integration into the overall management of patients with aortic stenosis. It is therefore essential to increase its accessibility, train cardiologists in its interpretation, and promote multicenter prospective studies to better define its impact on therapeutic strategies and long-term clinical outcomes.

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