Seeing the Future of Aortic Disease: How 4D Flow MRI Predicts Surgery in Patients with Bicuspid Aortic Valve

Document Type

Conference Proceeding - Restricted Access

Publication Date

5-9-2025

Abstract

Bicuspid aortic valve (BAV) is the most common congenital heart defect, often causing progressive dilation of the ascending aorta (AAo), which can lead to dissections or ruptures. As a result, guidelines recommend lifelong monitoring and prophylactic repair once AAo dilation occurs. However, these guidelines are largely based on expert consensus due to limited observational data. This highlights the need for new biomarkers to risk-stratify BAV patients. Recent 4D flow MRI studies show that BAV morphology leads to abnormal flow patterns, increasing wall shear stress (WSS)-a key driver of aortic dilation. These studies suggest that WSS could serve as an early predictor of AAo dilation. However, the long-term prognostic value of WSS remains unclear. Therefore, our study aims to quantify WSS in BAV patients using 4D flow MRI and assess its ability to predict aortic surgery need over 10 years.

This study was conducted at Northwestern University. BAV patients without prior surgical intervention who underwent an MRI scan-including a 4D flow sequence-prior to April 1, 2014, were retrospectively identified from medical records. Patients were followed for 10 years and categorized into two groups: 'operated' if they underwent aortic surgery within 10 years post-scan, and 'non-operated' if they remained surgery-free for at least 10 years post-scan. 4D flow MRIs were processed with an AI pipeline, capable of automatically performing 3D segmentation of the aorta and isolating the AAo. Following processing steps, peak velocity (PV) and WSS were quantified in the AAo using an established algorithm. Baseline mid-AAo diameters were measured by a radiologist using the double-oblique technique. Normality of the data was assessed using the Kolmogorov-Smirnov test and T-tests were performed to identify significant differences between groups, with a significance threshold set at p < 0.05.

A total of 115 patients were included in the study, comprising 73 non-operated patients (mean age: 42.5 ± 11.5 years, 49 males) and 42 operated patients (mean age: 53.5 ± 12.1 years, 34 males). No significant difference in age was detected between the two groups (p = 0.12). The mean mid-AAo diameter at baseline for non-operated and operated patients were 3.8 ± 0.6 cm and 4.1 ± 0.5 cm, respectively (p = 0.11). Among the operated patients, the average time from initial scan to surgery was 5.7 ± 3.3 years. In terms of 4D flow metrics, the operated group exhibited significantly higher flow values compared to the non-operated group: PV of 2.6 ± 0.6 m/s vs. 1.7 ± 0.4 m/s (p < 0.01) and WSS of 2.2 ± 0.5 Pa vs. 1.6 ± 0.4 Pa (p < 0.01).

4D flow MRI-derived PV and WSS offer valuable long-term predictive insights in BAV patients. High PV and WSS are associated with aortic surgery within 10 years of the scan, highlighting their potential as early markers of surgical risk. These findings suggest that altered hemodynamics, reflected in higher flow metrics, may drive the progression of aortic disease. Monitoring these parameters could help identify patients at risk of dilation, enabling earlier intervention and potentially preventing late-stage complications associated with surgery or disease progression.

Comments

2025 Research Day Corewell Health West, Grand Rapids, MI, May 9, 2025. Abstract 1685

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