Scientists at the University of East Anglia (UEA) have developed a cutting-edge MRI-based technique that significantly improves the diagnosis and management of aortic stenosis, a life-threatening heart condition affecting hundreds of thousands in the UK and worldwide.
It is more commonly diagnosed in high-income countries, largely due to aging populations and widespread availability of echocardiographic screening. In contrast, in low- and middle-income countries, the prevalence may be underreported due to limited diagnostic resources, and rheumatic heart disease remains a notable cause of AS, particularly in younger individuals. This condition affects around 5% of adults over 65 in the US and an estimated 300,000 people in the UK. It can lead to serious symptoms, including chest pain, dizziness, fatigue, and even heart failure if left untreated.
Currently, transthoracic echocardiography (TTE), a type of ultrasound, is the standard diagnostic tool for AS. However, it has limitations, particularly in accurately measuring peak aortic valve velocity (VPeak), a key indicator of disease severity. TTE measurements can be affected by misalignment of the ultrasound beam and patient-specific flow conditions, which may lead to underestimations and delayed interventions.
In the newly published study in Open Heart, researchers evaluated the effectiveness of four-dimensional flow cardiovascular magnetic resonance (4D flow CMR) in diagnosing and predicting the need for surgical intervention in AS patients. This advanced imaging method visualizes blood flow in three directions over time (the fourth dimension), providing a detailed and comprehensive view of heart valve function.
The study involved 30 patients (mean age 75.4 years, 67% male) from the PREFER-CMR registry who underwent both TTE and 4D flow CMR imaging. Over an eight-month follow-up, 17 of these patients underwent aortic valve intervention.
The results demonstrated that 4D flow CMR provided more accurate and reliable measurements of VPeak compared to traditional echocardiography. The average VPeak measured by 4D flow was significantly higher in patients who required surgery (4.2 m/s vs 2.7 m/s, P<0.0001), and it was a strong predictor of valve replacement, with a hazard ratio (HR) of 2.51 (P<0.01). In contrast, the echocardiographic VPeak did not significantly predict the need for surgery (HR = 0.54, P = 0.76).
The researchers suggested that 4D flow CMR offers a significant advantage over standard ultrasound methods, allowing for more accurate diagnosis and timely surgical intervention, which could save thousands of lives. The study also identified a 4D flow VPeak threshold of greater than 3.5 m/s as a robust marker for determining when surgery is needed.
In a prior study, the researchers validated peak pressure gradients derived from 4D flow CMR by comparing them with both TTE and invasive catheter-based measurements. The results demonstrated that 4D flow CMR measurements aligned more closely with invasive data, indicating its superior accuracy over TTE in evaluating the severity of aortic stenosis.
The present research supports the integration of 4D flow CMR into clinical practice guidelines, especially in cases where TTE results are inconclusive or discordant. As cardiac imaging continues to evolve, this innovation marks a major step forward in precision cardiology, offering hope for earlier diagnosis and improved outcomes for patients with aortic stenosis.
The key advantages of 4D flow CMR in aortic stenosis is listed below:
- Provides more precise assessment of VPeak than TTE, reducing the risk of underestimation.
- Demonstrates strong predictive ability for determining the need for surgical intervention.
- Allows dynamic visualization of three-directional blood flow across the aortic valve over time.
- Peak pressure gradients align more closely with invasive catheter-based measurements than with TTE.
- Offers critical diagnostic clarity in patients with suboptimal TTE images or discordant results.
- Unlike Doppler ultrasound, it is not affected by beam alignment, improving reliability.
- Enables retrospective evaluation of blood flow anywhere within the imaging volume.
- Evaluates wall shear stress, turbulent flow, adjacent aortic structures, and energy loss, which are relevant for disease progression.
References
- Grafton-Clarke C, Assadi H, Li R, Mehmood Z, Hall R, Matthews G, et al. Four-dimensional flow provides incremental diagnostic value over echocardiography in aortic stenosis. Open Heart [Internet]. 2025 May 7 [cited 2025 May 9];12(1). Available from: https://openheart.bmj.com/content/12/1/e003081
- Grafton-Clarke C, Njoku P, Aben JP, Ledoux L, Zhong L, Westenberg J, et al. Validation of aortic valve pressure gradient quantification using semi-automated 4D flow CMR pipeline. BMC Research Notes. 2022 Apr 29;15(1):151.