Comprehensive assessment of local and regional aortic stiffness in patients with tricuspid or bicuspid aortic valve aortopathy using magnetic resonance imaging

Association of Impaired Left Ventricular Mitral Filling from 4D Flow Cardiac MRI and Prognosis of Hypertrophic Cardiomyopathy

Purpose To investigate whether the peak early filling rate normalized to the filling volume (PEFR/FV) estimated from four-dimensional (4D) flow cardiac MRI may be used to assess impaired left ventricular (LV) filling and predict clinical outcomes in individuals with hypertrophic cardiomyopathy (HCM). Materials and Methods Cardiac MRI with a 4D flow sequence and late gadolinium enhancement (LGE), as well as echocardiography, was performed in 88 individuals: 44 participants with HCM from a French prospective registry (ClinicalTrials.gov; NCT01091480) and 44 healthy volunteers matched for age and sex. In participants with HCM, a composite primary end point was assessed at follow-up, including unexplained syncope, new-onset atrial fibrillation, hospitalization for congestive heart failure, ischemic stroke, sustained ventricular arrhythmia, septal reduction therapy, and cardiac death. A Cox proportional hazard model was used to analyze associations with the primary end point. Results PEFR/FV was significantly lower in the HCM group (mean age, 51.8 years ± 18.5 [SD]; 29 male participants) compared with healthy volunteers (mean, 3.35 sec-1 ± 0.99 [0.90-5.20] vs 4.42 sec-1 ± 1.68 [2.74-11.86]; P < .001) and correlated with both B-type natriuretic peptide (BNP) level (r = -0.31; P < .001) and the ratio of pulsed Doppler early transmitral inflow to Doppler tissue imaging annulus velocities (E/E'; r = -0.54; P < .001). At a median follow-up of 2.3 years (IQR, 1.7-3.3 years), the primary end point occurred in 14 (32%) participants. A PEFR/FV of 2.61 sec-1 or less was significantly associated with occurrence of the primary end point (hazard ratio, 9.46 [95% CI: 2.61, 45.17; P < .001] to 15.21 [95% CI: 3.51, 80.22; P < .001]), independently of age, BNP level, E/E', LGE extent, and LV and left atrial strain according to successive bivariate models. Conclusion In HCM, LV filling evaluated with 4D flow cardiac MRI correlated with Doppler and biologic indexes of diastolic dysfunction and predicted clinical outcomes. Keywords: Diastolic Function, Left Ventricular Filling, Hypertrophic Cardiomyopathy, Cardiac MRI, 4D Flow Sequence Clinical trial registration no. NCT01091480 Supplemental material is available for this article. © RSNA, 2024.

Type III aortic arch angulation increases aortic stiffness: Analysis from an ex vivo porcine model

Objective

The relationship among increased aortic arch angulation, aortic flow dynamics, and vessel wall stiffness remains unclear. This experimental ex vivo study investigated how increased aortic arch angulation affects aortic stiffness and stent-graft induced aortic stiffening, assessed by pulse wave velocity (PWV).

Methods

Porcine thoracic aortas were connected to a circulatory mock loop in a Type I and Type III aortic arch configuration. Baseline characteristics and blood pressures were measured. Proximal and distal flow curves were acquired to calculate PWV in both arch configurations. After that, a thoracic stent-graft (VAMF2626C100TU) was deployed in aortas with adequate proximal landing zone diameters to reach 10% t0 20% oversizing. Acquisitions were repeated for both arch configurations after stent-graft deployment.

Results

Twenty-four aortas were harvested, surgically prepared, and mounted. Cardiac output was kept constant for both arch configurations (Type I: 4.74 ± 0.40 and Type III: 4.72 ± 0.38 L/minute; P = .703). Compared with a Type I arch, aortic PWV increased significantly in the Type III arch (3.53 ± 0.40 vs 3.83 ± 0.40 m/second; P < .001), as well as blood pressures. A stent-graft was deployed in 15 aortas. After deployment, Type I arch PWV increased (3.55 ± 0.39 vs 3.81 ± 0.44 m/second; P < .001) and Type III arch PWV increased although not significantly (3.86 ± 0.42 vs 4.03 ± 0.46 m/second; P = .094). Type III arch PWV resulted the highest and significantly higher compared with the Type I arch after stent-graft deployment (3.81 ± 0.44 vs 4.03 ± 0.46 m/second; P = .023).

Conclusions

Increased aortic arch angulation-as in a Type III arch-is associated with higher aortic PWV and blood pressures and this may negatively influence cardiovascular health.

Mechanisms of Aortic Dilation in Patients With Bicuspid Aortic Valve: JACC State-of-the-Art Review

Bicuspid aortic valve is the most common congenital heart disease and exposes patients to an increased risk of aortic dilation and dissection. Aortic dilation is a slow, silent process, leading to a greater risk of aortic dissection. The prevention of adverse events together with optimization of the frequency of the required lifelong imaging surveillance are important for both clinicians and patients and motivated extensive research to shed light on the physiopathologic processes involved in bicuspid aortic valve aortopathy. Two main research hypotheses have been consolidated in the last decade: one supports a genetic basis for the increased prevalence of dilation, in particular for the aortic root, and the second supports the damaging impact on the aortic wall of altered flow dynamics associated with these structurally abnormal valves, particularly significant in the ascending aorta. Current opinion tends to rule out mutually excluding causative mechanisms, recognizing both as important and potentially clinically relevant.

A clinician's guide to understanding aortic 4D flow MRI

Four-dimensional flow magnetic resonance imaging is an emerging technique which may play a role in diagnosis and risk-stratification of aortic disease. Some knowledge of flow dynamics and related parameters is necessary to understand and apply this technique in clinical workflows. The purpose of the current review is to provide a guide for clinicians to the basics of flow imaging, frequently used flow-related parameters, and their relevance in the context of aortic disease.Clinical relevance statement Understanding normal and abnormal aortic flow could improve clinical care in patients with aortic disease.

Global Aortic Pulse Wave Velocity is Unchanged in Bicuspid Aortopathy With Normal Valve Function but Elevated in Patients With Aortic Valve Stenosis: Insights From a 4D Flow MRI Study of 597 Subjects

BACKGROUND

Aortopathy is common with bicuspid aortic valve (BAV), and underlying intrinsic tissue abnormalities are believed causative. Valve-mediated hemodynamics are altered in BAV and may contribute to aortopathy and its progression. The contribution of intrinsic tissue defects versus altered hemodynamics to aortopathy progression is not known.

PURPOSE

To investigate relative contributions of tissue-innate versus hemodynamics in progression of BAV aortopathy.

STUDY TYPE

Retrospective.

SUBJECTS

Four hundred seventy-three patients with aortic dilatation (diameter ≥40 mm; comprised of 281 BAV with varied AS severity, 192 tricuspid aortic valve [TAV] without AS) and 124 healthy controls. Subjects were 19-91 years (141/24% female).

FIELD STRENGTH/SEQUENCE

1.5T, 3T; time-resolved gradient-echo 3D phase-contrast (4D flow) MRI.

ASSESSMENT

A surrogate measure for global aortic wall stiffness, pulse wave velocity (PWV), was quantified from MRI by standardized, automated technique based on through-plane flow cross-correlation maximization. Comparisons were made between BAV patients with aortic dilatation and varying aortic valve stenosis (AS) severity and healthy subjects and aortopathy patients with normal TAV.

STATISTICAL TESTS

Multivariable regression, analysis of covariance (ANCOVA), Tukey's, student's (t), Mann-Whitney (U) tests, were used with significance levels P < 0.05 or P < 0.01 for post-hoc Bonferroni-corrected t/U tests. Bland-Altman and ICC calculations were performed.

RESULTS

Multivariable regression showed age with the most significant association for increased PWV in all groups (increase 0.073-0.156 m/sec/year, R²  = 0.30-48). No significant differences in aortic PWV were observed between groups without AS (P = 0.20-0.99), nor were associations between PWV and regurgitation or Sievers type observed (P = 0.60, 0.31 respectively). In contrast, BAV AS patients demonstrated elevated PWV and a significant relationship for AS severity with increased PWV (covariate: age, R²  = 0.48). BAV and TAV patients showed no association between aortic diameter and PWV (P = 0.73).

DATA CONCLUSION

No significant PWV differences were observed between BAV patients with normal valve function and control groups. However, AS severity and age in BAV patients were directly associated with PWV increases.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: Stage 3.

Patients with Bicuspid Aortopathy and Aortic Dilatation

(1) Background: Bicuspid aortic valve (BAV) is the most frequent congenital cardiac disease. Alteration of ascending aorta diameter is a consequence of shear stress alterations due to haemodynamic abnormalities developed from inadequate valve cusp coaptation. (2) Objective: This narrative review aims to discuss anatomical, pathophysiological, genetical, ultrasound, and radiological aspects of BAV disease, focusing on BAV classification related to imaging patterns and flux models involved in the onset and developing vessel dilatation. (3) Methods: A comprehensive search strategy was implemented in PubMed from January to May 2022. English language articles were selected independently by two authors and screened according to the following criteria. (4) Key Contents and Findings: Ultrasound scan is the primary step in the diagnostic flowchart identifying structural and doppler patterns of the valve. Computed tomography determines aortic vessel dimensions according to the anatomo-pathology of the valve. Magnetic resonance identifies hemodynamic alterations. New classifications and surgical indications derive from these diagnostic features. Currently, indications correlate morphological results, dissection risk factors, and genetic alterations. Surgical options vary from aortic valve and aortic vessel substitution to aortic valve repair according to the morphology of the valve. In selected patients, transcatheter aortic valve replacement has an even more impact on the treatment choice. (5) Conclusions: Different imaging approaches are an essential part of BAV diagnosis. Morphological classifications influence the surgical outcome.

Clinical implications of the biomechanics of bicuspid aortic valve and bicuspid aortopathy

Bicuspid aortic valve (BAV), which affects up to 2% of the general population, results from the abnormal fusion of the cusps of the aortic valve. Patients with BAV are at a higher risk for developing aortic dilatation, a condition known as bicuspid aortopathy, which is associated with potentially life-threatening sequelae such as aortic dissection and aortic rupture. Although BAV biomechanics have been shown to contribute to aortopathy, their precise impact is yet to be delineated. Herein, we present the latest literature related to BAV biomechanics. We present the most recent definitions and classifications for BAV. We also summarize the current evidence pertaining to the mechanisms that drive bicuspid aortopathy. We highlight how aberrant flow patterns can contribute to the development of aortic dilatation. Finally, we discuss the role cardiac magnetic resonance imaging can have in assessing and managing patient with BAV and bicuspid aortopathy.

Deep Learning-based Automated Aortic Area and Distensibility Assessment: the Multi-Ethnic Study of Atherosclerosis (MESA)

This study details application of deep learning for automatic segmentation of the ascending and descending aorta from 2D phase-contrast cine magnetic resonance imaging for automatic aortic analysis on the large MESA cohort with assessment on an external cohort of thoracic aortic aneurysm (TAA) patients. This study includes images and corresponding analysis of the ascending and descending aorta at the pulmonary artery bifurcation from the MESA study. Train, validation, and internal test sets consisted of 1123 studies (24,282 images), 374 studies (8067 images), and 375 studies (8069 images), respectively. The external test set of TAAs consisted of 37 studies (3224 images). CNN performance was evaluated utilizing a dice coefficient and concordance correlation coefficients (CCC) of geometric parameters. Dice coefficients were as high as 97.55% (CI: 97.47-97.62%) and 93.56% (CI: 84.63-96.68%) on the internal and external test of TAAs, respectively. CCC for maximum and minimum and ascending aortic area were 0.969 and 0.950, respectively, on the internal test set and 0.997 and 0.995, respectively, for the external test. The absolute differences between manual and deep learning segmentations for ascending and descending aortic distensibility were 0.0194 × 10^-4 ± 9.67 × 10^-4 and 0.002 ± 0.001 mmHg^-1, respectively, on the internal test set and 0.44 × 10^-4 ± 20.4 × 10^-4 and 0.002 ± 0.001 mmHg^-1, respectively, on the external test set. We successfully developed a U-Net-based aortic segmentation and analysis algorithm in both MESA and in external cases of TAA.