Effect of Aortic Valve Disease on 3D Hemodynamics in Patients With Aortic Dilation and Trileaflet Aortic Valve Morphology

Pathophysiology of the ascending aorta: Impact of dilation and valve phenotype on large-scale blood flow coherence detected by 4D flow MRI

BACKGROUND AND OBJECTIVE

The evidence on the role of hemodynamics in aorta pathophysiology has yet to be robustly translated into clinical applications, to improve risk stratification of aortic diseases. Motivated by the need to enrich the current understanding of the pathophysiology of the ascending aorta (AAo), this study evaluates in vivo how large-scale aortic flow coherence is affected by AAo dilation and aortic valve phenotype.

METHODS

A complex networks-based approach is applied to 4D flow MRI data to quantify subject-specific AAo flow coherence in terms of correlation between axial velocity waveforms and the aortic flow rate waveform along the cardiac cycle. The anatomical length of persistence of such correlation is quantified using the recently proposed network metric average weighted curvilinear distance (AWCD). The analysis considers 107 subjects selected to allow an ample stratification in terms of aortic valve morphology, absence/presence of AAo dilation and of aortic valve stenosis.

RESULTS

The analysis highlights that the presence of AAo dilation as well as of bicuspid aortic valve phenotype breaks the physiological AAo flow coherence, quantified in terms of AWCD. Of notice, it emerges that cycle-average blood flow rate and relative AAo dilation are main determinants of AWCD, playing opposite roles in promoting and hampering the persistence of large-scale flow coherence in AAo, respectively.

CONCLUSIONS

The findings of this study can contribute to broaden the current mechanistic link between large-scale blood flow coherence and aortic pathophysiology, with the prospect of enriching the existing tools for the in vivo non-invasive hemodynamic risk assessment for aortic diseases onset and progression.

Aortic Valve Dysfunction and Aortopathy Based on the Presence of Raphe in Patients with Bicuspid Aortic Valve Disease

(1) Background: To identify the association between the presence or absence of a raphe and aortic valve dysfunction, as well as the presence of aortopathy in patients with a bicuspid aortic valve (BAV); (2) Methods: This retrospective study enrolled 312 participants (mean (SD) age, 52.7 (14.3) years; 227 men (72.8%)) with BAV. The BAVs were divided into those with the presence (raphe+) or absence (raphe-) of a raphe. Valvular function was classified as normal, aortic regurgitation (AR), or aortic stenosis (AS) using TTE. The pattern of BAV aortopathy was determined by the presence of dilatation at the sinus of Valsalva and the middle ascending aorta using CCT; (3) Results: BAVs with raphe+ had a higher prevalence of AR (148 (79.5%) vs. 48 (37.8%), p < 0.001), but a lower prevalence of AS (90 (48.6%) vs. 99 (78.0%), p < 0.001) compared with those with raphe-. The types of BAV aortopathy were significantly different (p = 0.021) according to those with BAV-raphe+ and BAV-raphe-; (4) Conclusions: The presence of a raphe was significantly associated with a higher prevalence of AR, but a lower prevalence of AS and combined dilatation of the aortic root and middle ascending aorta. The presence of a raphe was an independent determinant of AR.

GUCCI - Guided Cardiac Cohort Investigation of Blood Flow Data

We present the framework GUCCI (Guided Cardiac Cohort Investigation), which provides a guided visual analytics workflow to analyze cohort-based measured blood flow data in the aorta. In the past, many specialized techniques have been developed for the visual exploration of such data sets for a better understanding of the influence of morphological and hemodynamic conditions on cardiovascular diseases. However, there is a lack of dedicated techniques that allow visual comparison of multiple data sets and defined cohorts, which is essential to characterize pathologies. GUCCI offers visual analytics techniques and novel visualization methods to guide the user through the comparison of predefined cohorts, such as healthy volunteers and patients with a pathologically altered aorta. The combination of overview and glyph-based depictions together with statistical cohort-specific information allows investigating differences and similarities of the time-dependent data. Our framework was evaluated in a qualitative user study with three radiologists specialized in cardiac imaging and two experts in medical blood flow visualization. They were able to discover cohort-specific characteristics, which supports the derivation of standard values as well as the assessment of pathology-related severity and the need for treatment.

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

Ascending thoracic aortic aneurysm is a life-threatening disease, which is difficult to detect prior to the occurrence of a catastrophe. Epidemiology patterns of ascending thoracic aortic dilations/aneurysms remain understudied, whereas the risk assessment of it may be improved. The electronic databases PubMed/Medline 1966–2022, Web of Science 1975–2022, Scopus 1975–2022, and RSCI 1994–2022 were searched. The current guidelines recommend a purely aortic diameter-based assessment of the thoracic aortic aneurysm risk, but over 80% of the ascending aorta dissections occur at a size that is lower than the recommended threshold of 55 mm. Moreover, a 55 mm diameter criterion could exclude a vast majority (up to 99%) of the patients from preventive surgery. The authors review several visualization-based and alternative approaches which are proposed to better predict the risk of dissection in patients with borderline dilated thoracic aorta. The imaging-based assessments of the biomechanical aortic properties, the Young’s elastic modulus, the Windkessel function, compliance, distensibility, wall shear stress, pulse wave velocity, and some other parameters have been proposed to improve the risk assessment in patients with ascending thoracic aortic aneurysm. While the authors do not argue for shifting the diameter threshold to the left, they emphasize the need for more personalized solutions that integrate the imaging data with the patient’s genotypes and phenotypes in this heterogeneous pathology.

Quantitative assessment of aortic regurgitation following transcatheter aortic valve replacement

Introduction: Transcatheter aortic valve replacement (TAVR) is expanding to lower risk and younger patients with severe symptomatic aortic valve disease. Despite clinical and technological improvements, post-procedural aortic regurgitation (AR) remains a limitation of TAVR, particularly when compared to surgical aortic valve replacement. Although several methods for AR quantification after TAVR are currently available, its exact graduation in everyday clinical practice remains challenging.Areas covered: This review describes the currently available evaluation methods of AR after TAVR, with a special emphasis on the quantitative assessment using videodensitometric angiography, echocardiography and cardiac magnetic resonance imaging.Expert opinion: In the majority of clinical scenarios, satisfactory evaluation of post-TAVR AR can be achieved with a combination of post-procedural angiography, hemodynamic indices and transthoracic echocardiography. Nevertheless, some TAVR patients show 'intermediate' forms of post-procedural AR, in which quantitative evaluation is mandatory for prognostic purposes and further decision-making. Notably, interpretation of quantitative measures early post-TAVR is challenging because of the lack of left ventricular enlargement. Video-densitometric angiography is an emerging method that appears to be clinically attractive for immediate post-TAVR assessment, but requires further validation in everyday clinical practice.

Hemodynamic change in patients with hypertrophic obstructive cardiomyopathy before and after alcohol septal ablation using 4D flow magnetic resonance imaging: a retrospective observational study

Background

The hemodynamics in the left ventricle (LV) and the ascending aorta (AAO) before and after alcohol septal ablation (ASA) in patients with hypertrophic obstructive cardiomyopathy (HOCM) is elucidated. Our objective was to evaluate the pattern changes in AAO and intra-LV flow assessed by four-dimensional (4D) flow magnetic resonance imaging (MRI) before and after ASA and to clarify the association between 4D flow MRI-derived hemodynamic characteristics and the peak pressure gradient (PPG) in patients with drug-refractory HOCM.

Methods

In this retrospective observational study, 11 patients with HOCM underwent 4D flow MRI before and a week after ASA. The 4D flow MRI included blood flow visualization and quantification using streamline images. The combined score of vortex and helix in AAO was analyzed. The duration and phase count of the AAO vortex or helix flow and the size of the intra-LV anterior vortex were quantified. The correlation between the changes in hemodynamics and the resting PPG at LV outflow tract was also analyzed. We used the paired t-test for the comparison between before and after ASA and the Pearson’s correlation coefficient for the analysis.

Results

The combined score for the incidence of vortex and/or helix flow in AAO after ASA was significantly lower than that before ASA (1.45 ± 0.52 vs. 1.09 ± 0.30, p = 0.046). The duration (744 ± 291 ms vs. 467 ± 258 ms, p < 0.001) and phase count (14.8 ± 4.4 phases vs. 10.5 ± 5.8 phases, p < 0.001) of the vortex or helix flow in AAO were significantly decreased after ASA. The LV anterior vortex area after ASA was significantly larger than that before ASA (1628 ± 420 mm² vs. 2974 ± 539 mm², p = 0.009). The delta phase count of the AAO vortex or helix before and a week after ASA was significantly correlated with delta PPG before and a week after ASA (R = 0.79, p = 0.004) and with delta PPG before and 6 months after ASA (R = 0.83, p = 0.002).

Conclusions

Lower vortex or helix flow in AAO and larger diastolic vortex flow in LV were observed after ASA, which suggests the possibility to detect the changes of aberrant hemodynamics in HOCM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02003-8.

Prognostic significance of myocardial fibrosis and CMR characteristics in bicuspid aortic valve with moderate and severe aortic insufficiency

OBJECTIVES

This study attempted to evaluate the characteristics and prognostic value of myocardial fibrosis (MF) in aortic insufficiency (AI) patients with bicuspid aortic valve (BAV) or tricuspid aortic valve (TAV) by cardiac magnetic resonance (CMR).

METHODS

A total of 314 adults with CMR-diagnosed AI were retrospectively retrieved. Of them, 166 patients with moderate or severe AI were included and divided into two groups: BAV group (N = 46) and a TAV group (N = 120). The presence and characteristics of MF were assessed with CMR. The patients were followed for adverse clinical events. The prognostic capability of the parameters was assessed using Cox regression model.

RESULTS

LV fibrosis was more common in the BAV group than in the TAV group (65.2% vs. 45.0%; p = 0.020). There was a strong association between BAV and MF even after adjusting for clinical and imaging variables (odds ratio: 3.57; p = 0.031). Kaplan-Meier analysis showed a higher rate of clinical adverse events in AI+BAV patients with MF during a median follow-up of 4.7 years. Multivariate Cox regression analysis showed that late gadolinium enhancement (LGE) was an independent predictor of clinical adverse outcome.

CONCLUSION

MF is more common in AI with BAV than with TAV and is a predictor of clinical adverse events.

KEY POINTS

• The presence and extent of late gadolinium enhancement of left ventricular were more common and severer in the bicuspid aortic valve group than in the tricuspid aortic valve group in aortic insufficiency patients. • Bicuspid aortic valve was an independent factor for myocardial fibrosis in aortic insufficiency patients. • Late gadolinium enhancement could be used as an independent predictor of adverse clinical events in this population.

Fully quantitative mapping of abnormal aortic velocity and wall shear stress direction in patients with bicuspid aortic valves and repaired coarctation using 4D flow cardiovascular magnetic resonance

BACKGROUND

Helices and vortices in thoracic aortic blood flow measured with 4D flow cardiovascular magnetic resonance (CMR) have been associated with aortic dilation and aneurysms. Current approaches are semi-quantitative or when fully quantitative based on 2D plane placement. In this study, we present a fully quantitative and three-dimensional approach to map and quantify abnormal velocity and wall shear stress (WSS) at peak systole in patients with a bicuspid aortic valve (BAV) of which 52% had a repaired coarctation.

METHODS

4D flow CMR was performed in 48 patients with BAV and in 25 healthy subjects at a spatiotemporal resolution of 2.5 × 2.5 × 2.5mm3/ ~ 42 ms and TE/TR/FA of 2.1 ms/3.4 ms/8° with k-t Principal Component Analysis factor R = 8. A 3D average of velocity and WSS direction was created for the normal subjects. Comparing BAV patient data with the 3D average map and selecting voxels deviating between 60° and 120° and > 120° yielded 3D maps and volume (in cm3) and surface (in cm2) quantification of abnormally directed velocity and WSS, respectively. Linear regression with Bonferroni corrected significance of P < 0.0125 was used to compare abnormally directed velocity volume and WSS surface in the ascending aorta with qualitative helicity and vorticity scores, with local normalized helicity (LNH) and quantitative vorticity and with patient characteristics.

RESULTS

The velocity volumes > 120° correlated moderately with the vorticity scores (R ~ 0.50, P < 0.001 for both observers). For WSS surface these results were similar. The velocity volumes between 60° and 120° correlated moderately with LNH (R = 0.66) but the velocity volumes > 120° did not correlate with quantitative vorticity. For abnormal velocity and WSS deviating between 60° and 120°, moderate correlations were found with aortic diameters (R = 0.50-0.70). For abnormal velocity and WSS deviating > 120°, additional moderate correlations were found with age and with peak velocity (stenosis severity) and a weak correlation with gender. Ensemble maps showed that more than 60% of the patients had abnormally directed velocity and WSS. Additionally, abnormally directed velocity and WSS was higher in the proximal descending aorta in the patients with repaired coarctation than in the patients where coarctation was never present.

CONCLUSION

The possibility to reveal directional abnormalities of velocity and WSS in 3D provides a new tool for hemodynamic characterization in BAV disease.

Bicuspid aortic valve patients show specific epigenetic tissue signature increasing extracellular matrix destruction

OBJECTIVES

Patients with a bicuspid aortic valve (BAV) have an increased risk for developing thoracic aortic aneurysm, which is characterized by the destruction of the elastic media of the aortic wall. Several important enzymes have been characterized to play key roles in extracellular matrix homeostasis, namely matrix metalloproteinases (MMPs). In this study, we investigated MMP-2 levels and their epigenetic regulation via the miR-29 family.

METHODS

Aortic tissue samples from 58 patients were collected during cardiac surgery, of which 30 presented with a BAV and 28 with a tricuspid aortic valve. Polymerase chain reaction, western blot analysis and immunohistochemistry were performed to analyse MMP-2. In addition, enzyme-linked immunosorbent assay measurements were carried out to investigate both MMP-2 and tissue inhibitor of metalloproteinase-2 levels. To examine the epigenetic regulation of aortic extracellular matrix homeostasis, we furthermore studied the expression levels of miR-29 via qRT-PCR.

RESULTS

Patients with a BAV were significantly younger at the time of surgery, presented significantly less frequently with arterial hypertension and displayed more often with an additional valvular disease. On a molecular level, we found that MMP-2 is increased on gene and protein level in BAV patients. Tissue inhibitor of metalloproteinase-2 levels do not differ between the groups. Interestingly, we also found that only miR-29A is significantly downregulated in BAVs.

CONCLUSIONS

Our findings highlight the importance of MMP-2 in the context of extracellular matrix destruction in BAV patients. We present new evidence that miR-29A is a crucial epigenetic regulator of these pathomechanistic processes and might hold promise for future translational research.