Computational evaluation of mechano-elastic properties and of paramagnetic contrast enhancement of thoracic aortic wall in acute myocardial infarction and in non-coronarogenic myocardial damage, from the data of dynamic ECG-gated MRI (MR-elastometry)

Abstract

Background. The state of the aorta is a key factor in the prognosis of the patient’s life, since the distension of the ascending aorta in systole determines the blood supply to the myocardium in diastole. Paramagnetic contrast-enhanced MRI provides a reliable assessment of pathological neoangiogenesis, however, in fact, studies of the aorta are performed descriptively, without calculating mechanical strength and extensibility. Objective. To develop and clinically test on the patients with atherosclerotic lesions and myocarditis a method for quantitative assessment of extensibility and mechanical elasticity of the aortic wall.Design and methods. Were examined 12 patients with acute myocardial infarction with ST segment elevation, as a control group 11 patients without clinical and instrumental signs of atherosclerosis of large arteries and aorta. All underwent MRI of the chest and heart with paramagnetic contrast enhancement (PMCE) and ECG synchronization. The indices of aortic distensibility, distensibility normalized to pulse BP, Young’s modulus of the aortic wall, systolic distension of the ascending aorta (mL), index of strengthening of the aortic wall in PMCE were calculated.Results. Ascending aortic distensibility decreased in patients with myocarditis and acute infarction. Young’s modulus and distensibility of the ascending aorta significantly correlated with the value of the aortic wall enhancement index in PMCE. Myocardial damage in acute infarction and myocarditis was noted with a decrease in systolic expansion of the ascending aorta below 10 ml due to its reduced elasticity.Conclusion. There is a relationship between pathological accumulation of a paramagnet in the wall of the ascending aorta, a decrease in its elasticity, a decrease in the volume of systolic aortic dilation, and the development of hypoperfusion myocardial damage. Magnetic resonance elastometry of the aortic wall makes it possible to assess violations of aortic distensibility and predict the development of ischemic damage in the myocardium of the left ventricle.

Prospects of the Magnetic Resonance Imaging Method for Assessing the Bioelastic Function of the Aortic Wall

“…Растяжимость аорты с помощью МРТ у пациентов с артериальной гипертонией в РФ уже изучалась (Мартынов А. И. и др. 2001), при этом оценка биоэластических свойств аорты могла проводиться и у пациентов с острым инфарктом миокарда и при некоронарных его повреждениях [5]. Redheuil A. и др.…”

Existing and Emerging Approaches to Risk Assessment in Patients with Ascending Thoracic Aortic Dilatation

“…Serial cardiac magnetic resonance (CMR) measurements demonstrate that ascending aortic distensibility declined in BAV patients even faster than it did in a comparison group with connective tissue disorders [ 27 ]. A prospective assessment of the biomechanical and elastic aortic properties based on the data of echocardiography, CT, and CMR imaging is promising for risk stratification [ 28 , 29 , 30 ], but it should be integrated with other predictors.…”

“…Higher values of tensile strength and Young’s modulus are present in patients with an ascending aortic aneurysm [ 31 ], but studies focusing on Young’s modulus as a criterion for determining the timing of pre-emptive open aortic repair in patients with a borderline dilatation of the ascending thoracic aorta are almost lacking. We encourage researchers to consider the Young’s elastic modulus of the ascending aorta for the risk assessment of it because it may be easily calculated based on widely available ECG-synchronized MRI aortography as follows (1) ( Figure 1 ) [ 28 ]: E = ((d diast 2 × (1 − 0.25) × ABP pulse )/(2 × h × ∆d pulse )) × 133.3 where E—Young’s elastic modulus (Pa); d diast —diastolic aortic diameter; ∆d pulse —an increase in aortic diameter during systole; 0.25—squared Poisson ratio for the aorta wall (Poisson ratio is known to be 0.5); h—aorta wall thickness during diastole; ABP pulse —pulse arterial blood pressure; 133.3—mmHg to Pa conversion factor. …”

“…A group of patients underwent ECG-synchronized MRI-based aortography for months before some of them developed an ascending aortic aneurysm. The values of the Young’s elastic modulus in all of the patients who later developed the aneurysms exceeded 0.67 mPa, though the study was limited by its retrospective nature and small sample size [ 28 ]. The involvement of the aorta wall thickness in the formula agrees with the report revealing the association between this parameter and the adverse ascending aortic events.…”