Bicuspid valve aortopathy is associated with distinct patterns of matrix degradation

Geometry and flow in ascending aortic aneurysms are influenced by left ventricular outflow tract orientation: Detecting increased wall shear stress on the outer curve of proximal aortic aneurysms

BACKGROUND

The geometrical characterization of ascending thoracic aortic aneurysms in clinical practice is limited to diameter measurements. Despite growing interest in hemodynamic assessment, its relationship with ascending thoracic aortic aneurysm pathogenesis is poorly understood. This study examines the relationship between geometry of the ventriculo-aortic junction and blood flow patterns in ascending thoracic aortic aneurysm disease.

METHODS

Thirty-three patients with ascending thoracic aortic aneurysms (exclusions: bicuspid aortic valves, connective tissue disease) underwent 4-dimensional flow magnetic resonance imaging. After image segmentation, geometrical parameters were measured, including aortic curvature, tortuosity, length, and diameter. A unique angular measurement made by the trajectory of the left ventricular outflow tract axis and the proximal aorta was also conducted. Velocity profiles were quantitatively and qualitatively analyzed. In addition, 11 patients (33%) underwent wall shear stress mapping of the ascending thoracic aortic aneurysm region using computational fluid dynamics simulation.

RESULTS

Greater left ventricular outflow tract aortic angles were associated with larger aortic diameters at the levels of the sinus (coefficient = 0.387, P = .014) and ascending aorta (coefficient = 0.284, P = .031). Patients with left ventricular outflow tract aortic angles greater than 60° had marked asymmetric flow acceleration on the outer curvature in the proximal aorta, ascertained from 4-dimensional flow analysis. For patients undergoing computational fluid dynamics assessment, regression analysis found that higher left ventricular outflow tract aortic angles were associated with significantly higher wall shear stress values in the outer curve of the aorta (coefficient 0.07, 95% confidence interval 0.04-0.11, P = .002): Angles greater than 50° yielded time-averaged wall shear stress values greater than 2.5 Pa, exhibiting a linear relationship.

CONCLUSIONS

Our findings strengthen the hypothesis of flow-mediated ascending thoracic aortic aneurysm disease progression and that left ventricular outflow tract aortic angle may be a predictor of disease severity.

Prognostic role of aortic distensibility in patients with bicuspid aortic valve: a CMR study

To evaluate the prognostic value of aortic distensibility measured by cardiovascular magnetic resonance (CMR) as predictors of prophylactic aortic valve or aortic surgery in patients with bicuspid aortic valve (BAV). 110 patients with BAV were included. Distensibility of middle ascending aorta (AscAo) and proximal descending aorta (DescAo) at baseline was determined using CMR. The association between aortic distensibility and primary endpoint of aortic valve and/or aortic surgery was investigated with Cox proportional hazard regression analyses. The receiver operating characteristics curves (ROC) of the area under receiver-operator (AUC) and DeLong test were used to evaluate and compare the performance of different models. During a median follow-up of 66.5 months [IQR 13-75 months], 42 patients experienced surgical treatments. After adjusting for traditional risk factors, aortic distensibility (P = 0.003) and severe valve dysfunction (P < 0.001) were found significantly associated with aortic valve and/or aortic surgery. The model 2 (aortic distensibility and severe valve dysfunction) is slightly better in predicting primary endpoint than the model 1 (aortic diameter and severe valve dysfunction) (AUC: 0.893 vs. 0.842, P = 0.106). In BAV patients, aortic distensibility and severe valve dysfunction are valuable predictors for final aortic valve and/or aortic surgery.

Microcalcification and Thoracic Aortopathy: A Window Into Disease Severity

BACKGROUND

Patients with thoracic aortopathy are at increased risk of catastrophic aortic dissection, carrying with it substantial mortality and morbidity. Although granular medial calcinosis (medial microcalcification) has been associated with thoracic aortopathy, its relationship to disease severity has yet to be established.

METHODS

One hundred one thoracic aortic specimens were collected from 57 patients with thoracic aortopathy and 18 control subjects. Standardized histopathologic scores, immunohistochemistry, and nanoindentation (tissue elastic modulus) were compared with the extent of microcalcification on von Kossa histology and 18F-sodium fluoride autoradiography.

RESULTS

Microcalcification content was higher in thoracic aortopathy samples with mild (n=28; 6.17 [2.71-10.39]; P≤0.00010) or moderate histopathologic degeneration (n=30; 3.74 [0.87-11.80]; P<0.042) compared with control samples (n=18; 0.79 [0.36-1.90]). Alkaline phosphatase (n=26; P=0.0019) and OPN (osteopontin; n=26; P=0.0045) staining were increased in tissue with early aortopathy. Increasingly severe histopathologic degeneration was related to reduced microcalcification (n=82; Spearman ρ, -0.51; P<0.0001)-a process closely linked with elastin loss (n=82; Spearman ρ, -0.43; P<0.0001) and lower tissue elastic modulus (n=28; Spearman ρ, 0.43; P=0.026).¹⁸F-sodium fluoride autoradiography demonstrated good correlation with histologically quantified microcalcification (n=66; r=0.76; P<0.001) and identified areas of focal weakness in vivo.

CONCLUSIONS

Medial microcalcification is a marker of aortopathy, although progression to severe aortopathy is associated with loss of both elastin fibers and microcalcification.¹⁸F-sodium fluoride positron emission tomography quantifies medial microcalcification and is a feasible noninvasive imaging modality for identifying aortic wall disruption with major translational promise.

Micromechanical and Ultrastructural Properties of Abdominal Aortic Aneurysms

Abdominal aortic aneurysms are a common condition of uncertain pathogenesis that can rupture if left untreated. Current recommended thresholds for planned repair are empirical and based entirely on diameter. It has been observed that some aneurysms rupture before reaching the threshold for repair whilst other larger aneurysms do not rupture. It is likely that geometry is not the only factor influencing rupture risk. Biomechanical indices aiming to improve and personalise rupture risk prediction require, amongst other things, knowledge of the material properties of the tissue and realistic constitutive models. These depend on the composition and organisation of the vessel wall which has been shown to undergo drastic changes with aneurysmal degeneration, with loss of elastin, smooth muscle cells, and an accumulation of isotropically arranged collagen. Most aneurysms are lined with intraluminal thrombus, which has an uncertain effect on the underlying vessel wall, with some authors demonstrating a reduction in wall stress and others a reduction in wall strength. The majority of studies investigating biomechanical properties of ex vivo abdominal aortic aneurysm tissues have used low-resolution techniques, such as tensile testing, able to measure the global material properties at the macroscale. High-resolution engineering techniques such as nanoindentation and atomic force microscopy have been modified for use in soft biological tissues and applied to vascular tissues with promising results. These techniques have the potential to advance the understanding and improve the management of abdominal aortic aneurysmal disease.

Mid-term follow-up of aortic valve replacement for bicuspid aortic valve

OBJECTIVE

The purpose of this study was to evaluate the mid-term outcome of aortic valve replacement for bicuspid aortic valve and tricuspid aortic valve and the related risk factors.

METHODS

From January 2014 to June 2019, 177 tricuspid aortic valve patients and 101 bicuspid aortic valve patients who underwent aortic valve replacement in our hospital were collected. 1:1 propensity score matching analysis was used to control the bias in patient selection. The perioperative and follow-up data between the two groups were compared. Independent risk factors which were associated with the continued dilatation of the ascending aorta were identified by univariate or multivariate logistic regression analysis.

RESULTS

After the matching procedure, 160 patients were included in the analysis (80 in each group). Baseline characteristics, intraoperative, and perioperative outcomes were similar between the two groups (all p > 0.05). Moreover, 67 patients in the tricuspid aortic valve group and 70 in the bicuspid aortic valve group completed the follow-up. The ascending aorta change, annual change rate, and the proportion of continuous dilation of ascending aorta in bicuspid aortic valve group were significantly higher than those in the tricuspid aortic valve group (p < 0.05). Multivariate logistic regression analysis showed that type 1 in bicuspid aortic valve (OR 5.173; 95% CI 1.772, 15.101; p = 0.003), aortic regurgitation (OR 3.673; 95% CI 1.133, 11.908; p = 0.030), and aortic valve stenosis with regurgitation (OR 6.489; 95% CI 1.726, 24.404; p = 0.006) were independent risk factors for the continued dilatation of the ascending aorta in all AV patients. Furthermore, the multivariate logistic regression analysis showed that type 1 in bicuspid aortic valve (OR 5.157; 95% CI 1.053, 25.272; p = 0.043), age ≥ 40 years (OR 6.956; 95% CI 1.228, 39.410; p = 0.028), and aortic regurgitation (OR 4.322; 95% CI 1.174, 15.911; p = 0.028) were independent risk factors for the continued dilatation of the ascending aorta in bicuspid aortic valve patients.

CONCLUSION

Compared with tricuspid aortic valve patients, the ascending aorta of bicuspid aortic valve patients is more likely to continue to enlarge after aortic valve replacement. Type 1 in bicuspid aortic valve, age ≥ 40 years, and aortic regurgitation were the independent risk factors.

Exploring the potential of rapid evaporative ionization mass spectrometry (Intelligent Knife) for point-of-care testing in aortic surgery

 

OBJECTIVES

Many intraoperative decisions regarding the extent of thoracic aortic surgery are subjective and are based on the appearance of the aorta, perceived surgical risks and likelihood of early recurrent disease. Our objective in this work was to carry out a cross-sectional study to demonstrate that rapid evaporative ionization mass spectrometry (REIMS) of electrosurgical aerosol is able to empirically discriminate ex vivo aneurysmal human thoracic aorta from normal aorta, thus providing supportive evidence for the development of the technique as a point-of-care test guiding intraoperative surgical decision-making.

METHODS

Human aortic tissue was obtained from patients undergoing surgery for thoracic aortic aneurysms (n = 44). Normal aorta was obtained from a mixture of post-mortem and punch biopsies from patients undergoing coronary surgery (n = 13). Monopolar electrocautery was applied to samples and surgical aerosol aspirated and analysed by REIMS to produce mass spectral data.

RESULTS

Models generated from REIMS data can discriminate aneurysmal from normal aorta with accuracy and precision of 88.7% and 85.1%, respectively. In addition, further analysis investigating aneurysmal tissue from patients with bicuspid and tricuspid aortic valves was discriminated from normal tissue and each other with accuracies and precision of 93.5% and 91.4% for control, 83.8% and 76.7% for bicuspid aortic valve and 89.3% and 86.0% for tricuspid aortic valve, respectively.

CONCLUSIONS

Analysis of electrosurgical aerosol from ex vivo aortic tissue using REIMS allowed us to discriminate aneurysmal from normal aorta, supporting its development as a point-of-care test (Intelligent Knife) for guiding surgical intraoperative decision-making.