Variability of MRI Aortic Stiffness Measurements in a Multicenter Clinical Trial Setting: Intraobserver, Interobserver, and Intracenter Variability of Pulse Wave Velocity and Aortic Strain Measurement

Magnetic Resonance Imaging and Computed Tomography for the Noninvasive Assessment of Arterial Aging: A Review by the VascAgeNet COST Action

Magnetic resonance imaging and computed tomography allow the characterization of arterial state and function with high confidence and thus play a key role in the understanding of arterial aging and its translation into the clinic. Decades of research into the development of innovative imaging sequences and image analysis techniques have led to the identification of a large number of potential biomarkers, some bringing improvement in basic science, others in clinical practice. Nonetheless, the complexity of some of these biomarkers and the image analysis techniques required for their computation hamper their widespread use. In this narrative review, current biomarkers related to aging of the aorta, their founding principles, the sequence, and postprocessing required, and their predictive values for cardiovascular events are summarized. For each biomarker a summary of reference values and reproducibility studies and limitations is provided. The present review, developed in the COST Action VascAgeNet, aims to guide clinicians and technical researchers in the critical understanding of the possibilities offered by these advanced imaging modalities for studying the state and function of the aorta, and their possible clinically relevant relationships with aging.

Impaired aortic strain and distensibility by cardiac MRI in children with chronic kidney disease

Renal disease is associated with increased arterial stiffness. The aim was to investigate the effect of renal disease on regional aortic strain and distensibility in children with chronic kidney disease (CKD) by cardiac magnetic resonance imaging (MRI). The study included 30 children with CKD on hemodialysis, and ten healthy control subjects. Using cardiac MRI, maximal and minimal aortic areas were measured in axial cine steady state free precision images at the ascending aorta, proximal descending, and aorta at diaphragm. Regional strain and distensibility were calculated using previously validated formulas. Second reader aortic areas measurements were used to assess inter-observer agreement. Ascending aorta strain was significantly reduced in patients (38.4 ± 17.4%) compared to the control group (56.1 ± 17%), p-value 0.011. Ascending Aorta distensibility was significantly reduced in patients (9.1 ± 4.4 [× 10⁻³ mm Hg⁻¹]) compared to the control group (13.9 ± 4.9 [× 10⁻³ mm Hg⁻¹]), p-value 0.006. Strain and distensibility were reduced in proximal descending aorta and aorta at diaphragm but did not reach statistical significance. Only ascending aorta strain and distensibility had significant correlations with clinical and cardiac MRI parameters. Inter-observer agreement for strain and distensibility was almost perfect or strong in the three aortic regions. Aortic strain and distensibility by cardiac MRI are important imaging biomarkers for initial clinical evaluation and follow up of children with CKD.

Assessment of Aortic Stiffness by Transthoracic Echocardiographic in Young COVID-19 Patients

Background

Deteriorated aortic elasticity is part of the atherosclerotic process. Inflammation is an underlying factor in both COVID-19 and atherosclerosis.

Aims and Objectives

Using aortic elastic properties, we aimed to assess the subclinical indicators of susceptibility to inflammatory atherosclerosis in patients with COVID-19.

Materials and Methods

Out of 194 participants included in this study, 100 were diagnosed with COVID-19 in the last 6 months (60 women and 40 men with a mean age of 34.13 ± 6.45 years) and 94 were healthy controls (55 women and 39 men with a mean age of 30.39 ± 7.21 years). We analyzed transthoracic echocardiographic and aortic stiffness parameters in all participants.

Results

Values of systolic blood pressure (110 [85-140] vs. 110 [80-140], P = 0.037) and pulse pressure (PP) (37 [25-55] vs. 40 [25-55], P < 0.01) were significantly different between the groups. As for laboratory parameters, levels of glucose (97.89 ± 20.23 vs. 92.00 ± 9.95, P = 0.003) and creatinine (0.80 ± 0.13 vs. 0.75 ± 0.09, P = 0.003) were significantly higher in the COVID-19 group. Echocardiographic parameters showed that both groups differed significantly in diastolic aortic diameter (2.42 ± 0.28 vs. 2.31 ± 0.35, P = 0.017), aortic strain (9.66 [1.20-31.82] vs. 12.82 [2.41-40.11], P = 0.025), aortic distensibility (0.502 [0.049-2.545] vs. 0.780 [0.120-2.674], P < 0.01), and aortic stiffness (16.67 [4.19-139.43] vs. 11.71 [3.43-65.21], P = 0.006).

Conclusion

Measurement of aortic stiffness is a simple, practical yet inexpensive method in COVID-19 patients, and therefore, may be used as an early marker for COVID-19-induced subclinical atherosclerosis.

Evaluation of Plaque Characteristics and Inflammation Using Magnetic Resonance Imaging

Atherosclerosis is an inflammatory disease of large and medium-sized arteries, characterized by the growth of atherosclerotic lesions (plaques). These plaques often develop at inner curvatures of arteries, branchpoints, and bifurcations, where the endothelial wall shear stress is low and oscillatory. In conjunction with other processes such as lipid deposition, biomechanical factors lead to local vascular inflammation and plaque growth. There is also evidence that low and oscillatory shear stress contribute to arterial remodeling, entailing a loss in arterial elasticity and, therefore, an increased pulse-wave velocity. Although altered shear stress profiles, elasticity and inflammation are closely intertwined and critical for plaque growth, preclinical and clinical investigations for atherosclerosis mostly focus on the investigation of one of these parameters only due to the experimental limitations. However, cardiovascular magnetic resonance imaging (MRI) has been demonstrated to be a potent tool which can be used to provide insights into a large range of biological parameters in one experimental session. It enables the evaluation of the dynamic process of atherosclerotic lesion formation without the need for harmful radiation. Flow-sensitive MRI provides the assessment of hemodynamic parameters such as wall shear stress and pulse wave velocity which may replace invasive and radiation-based techniques for imaging of the vascular function and the characterization of early plaque development. In combination with inflammation imaging, the analyses and correlations of these parameters could not only significantly advance basic preclinical investigations of atherosclerotic lesion formation and progression, but also the diagnostic clinical evaluation for early identification of high-risk plaques, which are prone to rupture. In this review, we summarize the key applications of magnetic resonance imaging for the evaluation of plaque characteristics through flow sensitive and morphological measurements. The simultaneous measurements of functional and structural parameters will further preclinical research on atherosclerosis and has the potential to fundamentally improve the detection of inflammation and vulnerable plaques in patients.