The predictive capability of aortic stiffness index for aortic dissection among dilated ascending aortas

Stiffness matters: Improved failure risk assessment of ascending thoracic aortic aneurysms

Objectives

Rupture and dissection are feared complications of ascending thoracic aortic aneurysms caused by mechanical failure of the wall. The current method of using the aortic diameter to predict the risk of wall failure and to determine the need for surgical resection lacks accuracy. Therefore, this study aims to identify reliable and clinically measurable predictors for aneurysm rupture or dissection by performing a personalized failure risk analysis, including clinical, geometrical, histologic, and mechanical data.

Methods

The study cohort consisted of 33 patients diagnosed with ascending aortic aneurysms without genetic syndromes. Uniaxial tensile tests until failure were performed to determine the wall strength. Material parameters were fitted against ex vivo planar biaxial data and in vivo pressure-diameter relationships at diastole and systole, which were derived from multiphasic computed tomography (CT) scans. Using the resulting material properties and in vivo data, the maximal in vivo stress at systole was calculated, assuming a thin-walled axisymmetric geometry. The retrospective failure risk was calculated by comparing the peak wall stress at suprasystolic pressure with the wall strength.

Results

The distensibility coefficient, reflecting aortic compliance and derived from blood pressure measurements and multiphasic CT scans, outperformed predictors solely based on geometrical features in assessing the risk of aneurysm failure.

Conclusions

In a clinical setting, multiphasic CT scans followed by the calculation of the distensibility coefficient are of added benefit in patient-specific, clinical decision-making. The distensibility derived from the aneurysm volume change has the best predictive power, as it also takes the axial stretch into account.

Noninvasive left ventricular pressure-strain myocardial work in patients with well-functioning bicuspid aortic valves and aortic dilation: a preliminary study

Background

Noninvasive left ventricular pressure-strain myocardial work (MW) is a novel method for evaluating left ventricular function that integrates myocardial deformation and afterload and has certain advantages over global longitudinal strain (GLS). The study aimed to analyze MW in patients with well-functioning bicuspid aortic valve (BAV) and explore the influences of aortic dilation and arterial stiffness on left ventricular function.

Methods

A total of 104 patients with well-functioning BAVs and 50 controls were enrolled in our study. Global work index (GWI), global constructive work (GCW), global wasted work (GWW), global work efficiency (GWE), GLS, and aortic stiffness index were measured. Based on the ascending aortic diameter, patients with BAV were divided into 3 subgroups (nondilated, mildly dilated, and moderately dilated).

Results

GWI, GCW, GWW, and aortic stiffness index were significantly increased (P<0.001, P=0.023, P<0.001, and P<0.001, respectively), while GWE and GLS were significantly decreased among patients with BAV compared with controls (all P values <0.001). Patients with BAV and mildly and moderately dilated aortas had an increased GWW and aortic stiffness index but a decreased GWE compared with patients with BAV and nondilated aortas (all P values <0.05); meanwhile, GCW and GLS did not differ among the BAV subgroups (all P values >0.05). GWI was elevated in patients with BAV and moderately dilated aortas compared with patients with BAV and nondilated aortas (P<0.05). On multivariable analysis, the aortic stiffness index was an independent influencer of GWI, GCW, GWW, and GWE (P=0.025, P=0.049, P<0.001, and P=0.001, respectively). The aortic diameter was highly correlated with the aortic stiffness index (r=0.863; P<0.001).

Conclusions

MW could assess early myocardial impairment in patients with well-functioning BAV. MW may help to differentiate the detrimental effect of aortic dilation on left ventricular function, whereas GLS may not.

The Role of Spatial Aortic Arch Architecture in Type B Aortic Dissection

OBJECTIVE

The incidence of type B aortic dissection (TBAD) is increasing worldwide; however, the underlying pathomechanisms are not conclusively understood. This study explores the geometric architecture of the aortic arch and supra-aortic branches in TBAD patients as opposed to non-TBAD patients.

METHODS

Patient characteristics were retrieved from archived medical records. Computer-assisted tomography (CAT) scans of patients with TBAD and carotid stenosis (CS) from two high-volume centers were analyzed. Various aortic arch parameters and take-off angles of the supra-aortic branches of TBAD patients were measured following centerline normalization in comparison CS patients. A compression index (C-index) was calculated from the para-sagittal, and a torsion index (T-index) was calculated from the para-coronal take-off angles of the supra-aortic branches to analyze aortic arch tortuosity.

RESULTS

A total of 199 CAT scans were analyzed, namely, 85 in the TBAD group and 114 in the CS group. The average age was 61.5 ± 13.1 years among the TBAD patients and 71 ± 9.3 years among the CS patients. We found a significantly higher proportion of type III aortic arch configurations in TBAD patients compared with CS patients. Further, the aortic arch angle was steeper in the TBAD group. In the para-sagittal plane, the left subclavian artery (LSA) take-off angle was less steep in TBAD patients. In the para-coronal plane, the left carotid artery (LCA) had a less steep take-off angle, while the LSA had a more obtuse take-off angle in the TBAD group when compared with the CS group. In addition, the inter-vessel distance was increased in TBAD patients. Finally, the T-index was increased, suggesting a significant torsion resulting from the deviating take-off angles of the supra-aortic branches supplying the left half of the body as opposed to the innominate artery (IA) in TBAD patients.

CONCLUSIONS

Our results suggest several aortic arch-specific geometric configurations in patients suffering from TBAD that significantly differ from those in CS patients. Further functional studies are needed to verify the pathogenetic relevance of our results and their disease-specific causality. Although our data are not mechanistically explorative, they may serve as a basis for identifying future patients with aortic arch morphology at higher risk for TBAD development and who may benefit from more stringent adjustment of risk factors as a primary prevention concept.