Stent-Graft Deployment Increases Aortic Stiffness in an Ex Vivo Porcine Model

Initial Single-Center Experience With the Knickerbocker Technique During Thoracic Endovascular Aortic Repair to Block Retrograde False Lumen Flow in Patients With Type B Aortic Dissection

OBJECTIVE

Effectiveness of thoracic endovascular aortic repair in type B aortic dissection is impaired by persistent retrograde false lumen flow via distal re-entry tears. Controlled, stentgraft-assisted balloon dilatation of the true lumen at its lower end, or Knickerbocker technique, may block retrograde false lumen flow and consequently improve effectiveness by inducing immediate thrombosis along the entire descending thoracic aorta.

MATERIALS AND METHODS

A single-center retrospective analysis was performed for all consecutive patients with aortic dissection treated with the Knickerbocker technique to block retrograde false lumen flow.

RESULTS

Eleven patients were included for analysis. Intraoperative control angiography showed successful occlusion of the false lumen at the level of balloon dilatation in 9 out of 11 patients (82%). There was one perioperative mortality (9%), due to stroke. There were 2 early reinterventions, due to retroperitoneal bleeding and due to chyle leakage in the neck after left subclavian artery bypass. Median clinical follow-up duration was 6 (interquartile range [IQR] 2-11] months. There were 2 deaths during follow-up, one at 2 months after TEVAR from unknown cause of death, and one after 11 months due to rupture of an ascending aortic pseudoaneurysm. The Knickerbocker technique led to positive aortic remodeling. At 3 months follow-up, 100% of patients showed complete false lumen thrombosis in the thoracic aorta proximal to the level of balloon dilatation, with decreasing false lumen diameters (100%) and stable (44%) or decreasing (56%) total aortic diameters. In most patients, the false lumen distal to the stentgraft (i.e. at visceral level) remained patent (11% false lumen thrombosis rate), leading to ≥2 mm dilatation at this level (78% of patients) and in the infrarenal abdominal aorta (56% of patients) at 3 months postoperatively. No distal stent-graft-induced new entry tears were noticed during follow-up.

CONCLUSION

The Knickerbocker technique is feasible and effective, leading to positive aortic remodeling of the aorta covered by stentgraft in all of a small cohort of patients.

CLINICAL IMPACT

Persistent, retrograde false lumen perfusion from distal re-entries following thoracic endovascular aortic repair (TEVAR) for Stanford type B aortic dissection, may lead to progressive, aneurysmal dilatation. Controlled, stent graft-assisted balloon dilatation of the true lumen in the distal descending aorta (i.e. Knickerbocker technique) during TEVAR effectively excludes the false lumen from persistent flow resulting in positive aortic remodeling in our small cohort of patients, and hence potentially eliminates the risk of late post-dissection aneurysm formation in the descending thoracic aorta.

Review of Systemic Mock Circulation Loops for Evaluation of Implantable Cardiovascular Devices and Biological Tissues

CLINICAL IMPACT

On needs-based ex vivo monitoring of implantable devices or tissues/organs in cardiovascular simulators provides new insights and paves new paths for device prototypes. The insights gained could not only support the needs of patients, but also inform engineers, scientists and clinicians about undiscovered aspects of diseases (during routine monitoring). We analyze seminal and current work and highlight a variety of opportunities for developing preclinical tools that would improve strategies for future implantable devices. Holistically, mock circulation loop studies can bridge the gap between in vivo and in vitro approaches, as well as clinical and laboratory settings, in a mutually beneficial manner.

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.

Thoracic Endovascular Aortic RepairAcutely Augments Left Ventricular Biomechanics in An Animal Model: A Mechanism for Postoperative Heart Failure and Hypertension

BACKGROUND

Thoracic aortic stent grafts are thought to decrease aortic compliance and may contribute to hypertension and heart failure after thoracic endovascular aortic repair (TEVAR). Left ventricular (LV) biomechanics immediately after TEVAR, however, have not been quantified. Pressure-volume (PV) loop analysis provides gold-standard LV functional information. The aim of this study is to use an LV PV loop catheter and analysis to characterize the LV biomechanics before and acutely after TEVAR.

METHODS

Anesthetized Yorkshire swine (N = 6) were percutaneously instrumented with an LV PV loop catheter. A 20 mm × 10 cm stent graft was deployed distal to the left subclavian via the femoral artery under fluoroscopy. Cardiac biomechanics were assessed before and after TEVAR. As a sensitivity analysis, inferior vena cava occlusion with PV loop assessment was performed pre and post-TEVAR in 1 animal to obtain preload and afterload-independent end-systolic and end-diastolic PV relationships (ESPVR and EDPVR).

RESULTS

All animals underwent successful instrumentation and TEVAR. Post-TEVAR, all 6 animals had higher mean LV ESP (106 vs. 118 mm Hg, P = 0.04), with no change in the EDPVR. inferior vena cava occlusion also moved the ESPVR curve upward and leftward, indicating increased LV work per unit time. There was no augmentation of EDPVR following TEVAR (P > 0.05). Postmortem exams in all animals revealed appropriate stent placement and no technical complications.

CONCLUSIONS

TEVAR was associated with an acute increase in LV end-systolic pressure and shift in the ESPVR, indicating increased ventricular work. This data provides potential mechanistic insights into the development of post-TEVAR hypertension and heart failure. Future stent graft innovation should focus on minimizing the changes in cardiac physiology.

Depressed Ejection Fraction Does Not Affect Perioperative Mortality After Thoracic Endovascular Aortic Repair for Type B Aortic Dissection

BACKGROUND

Despite the expanded application of thoracic endovascular aortic repair (TEVAR) in patients with significant cardiac comorbidities, the effect of decreased left ventricular ejection fraction (EF) on outcomes remains unknown. The aim of this study was to compare outcomes in patients with normal and abnormal EFs undergoing TEVAR for type-B aortic dissection (TBAD).

METHODS

The Vascular Quality Initiative database was reviewed from 2012 to 2020. Patients were categorized into severely reduced (EF ≤ 30%), reduced (EF 30-50%) and normal EF (EF>50%). Baseline characteristics, procedural details and 18-month outcomes were compared. Multivariable logistic regression identified factors associated with mortality, major adverse cardiac events (MACEs), and aortic-related reintervention.

RESULTS

Of 1,993 patients, 38 (2%) and 208 (10%) patients had severely reduced ejection fraction (SREF) and reduced ejection fraction (REF). Patients with abnormal EF were more likely to have cardiac comorbidities and be prescribed angiotensin-converting enzyme inhibitors and anticoagulants. Perioperatively, patients with SREF were more likely to experience mortality (13.2% vs. 6.7% vs. 4.4%, P = 0.018), MACE (26.3% vs. 11.5% vs. 8%, P < 0.001), hemodialysis (13.5% vs. 5% vs. 2.9%, P = 0.001) and aortic related reintervention (21.1% vs. 13% vs. 10%, P = 0.041), compared to REF and normal ejection fraction (NEF) patients. However, these associations were not present on multivariable analysis. At 18 months, mortality was significantly higher in patients with SREF, which was confirmed on multivariable analysis, but depressed EF was not associated with increased aortic reintervention compared to NEF.

CONCLUSIONS

SREF was not independently associated with perioperative mortality or MACE compared to NEF. REF had similar risk of morbidity and mortality compared to NEF in both the perioperative and early postoperative periods. TEVAR-related complications were similar among the cohorts. As such, TEVAR may be offered to appropriately selected patients regardless of EF.

Three-Dimensional Characterization of Aortic Root Motion by Vascular Deformation Mapping

The aorta is in constant motion due to the combination of cyclic loading and unloading with its mechanical coupling to the contractile left ventricle (LV) myocardium. This aortic root motion has been proposed as a marker for aortic disease progression. Aortic root motion extraction techniques have been mostly based on 2D image analysis and have thus lacked a rigorous description of the different components of aortic root motion (e.g., axial versus in-plane). In this study, we utilized a novel technique termed vascular deformation mapping (VDM(D)) to extract 3D aortic root motion from dynamic computed tomography angiography images. Aortic root displacement (axial and in-plane), area ratio and distensibility, axial tilt, aortic rotation, and LV/Ao angles were extracted and compared for four different subject groups: non-aneurysmal, TAA, Marfan, and repair. The repair group showed smaller aortic root displacement, aortic rotation, and distensibility than the other groups. The repair group was also the only group that showed a larger relative in-plane displacement than relative axial displacement. The Marfan group showed the largest heterogeneity in aortic root displacement, distensibility, and age. The non-aneurysmal group showed a negative correlation between age and distensibility, consistent with previous studies. Our results revealed a strong positive correlation between LV/Ao angle and relative axial displacement and a strong negative correlation between LV/Ao angle and relative in-plane displacement. VDM(D)-derived 3D aortic root motion can be used in future studies to define improved boundary conditions for aortic wall stress analysis.

Impact of thoracic endovascular aortic repair on aortic biomechanics: Integration of in silico and ex vivo analysis using porcine model

Thoracic endovascular aortic repair (TEVAR) is widespread in clinical practice for treating aortic diseases but it has relevant systemic complications, such as increase of the cardiac workload due to post-TEVAR aortic stiffening, and local issues such as re-entry tears due to the tissue damage caused by endograft interaction. The present study aims to elucidate these aortic biomechanical mechanisms by coupling ex vivo and in silico analysis. By ex vivo tests, the pulse wave velocity before and after TEVAR is measured. Uni-axial tensile tests are performed to measure regional mechanical response of tissue samples, supplied as input data for the in silico analysis. Numerical analysis is finally performed to compute the wall stress induced by the stent-graft deployment and the arterial pressurization. The ex vivo results highlight an increase of baseline PWV by a mean .78 m/s or 12% after TEVAR with a 100 mm stent-graft (p <.013). In the in silico analysis, the average von Mises stress in the landing zone increases of about 15% and 20% using, respectively stent-graft with radial oversizing of 10% and 20%. This work shows the effectiveness of integrated framework to analyze the biomechanical post TEVAR mechanisms. Moreover, the obtained results quantify the effect of prosthesis selection on the stiffening of the aorta after TEVAR and on the local increase of the aortic wall stress that is proportional to the stent-graft oversizing.

Global and local stiffening of ex vivo-perfused stented human thoracic aortas: A mock circulation study

The effects of thoracic endovascular repair (TEVAR) on the biomechanical properties of aortic tissue have not been adequately studied. Understanding these features is important for the management of endograft-triggered complications of a biomechanical nature. This study aims to examine how stent-graft implantation affects the elastomechanical behavior of the aorta. Non-pathological human thoracic aortas (n=10) were subjected to long-standing perfusion (8h) within a mock circulation loop under physiological conditions. To quantify compliance and its mismatch in the test periods without and with a stent, the aortic pressure and the proximal cyclic circumferential displacement were measured. After perfusion, biaxial tension tests (stress-stretch) were carried out to examine the stiffness profiles between non-stented and stented tissue, followed by a histological assessment. Experimental evidence shows: (i) a significant reduction in aortic distensibility after TEVAR, indicating aortic stiffening and compliance mismatch, (ii) a stiffer behavior of the stented samples compared to the non-stented samples with an earlier entry into the nonlinear part of the stress-stretch curve and (iii) strut-induced histological remodeling of the aortic wall. The biomechanical and histological comparison of the non-stented and stented aortas provides new insights into the interaction between the stent-graft and the aortic wall. The knowledge gained could refine the stent-graft design to minimize the stent-induced impacts on the aortic wall and the resulting complications. STATEMENT OF SIGNIFICANCE: Stent-related cardiovascular complications occur the moment the stent-graft expands on the human aortic wall. Clinicians base their diagnosis on the anatomical morphology of CT scans while neglecting the endograft-triggered biomechanical events that compromise aortic compliance and wall mechanotransduction. Experimental replication of endovascular repair in cadaver aortas within a mock circulation loop may have a catalytic effect on biomechanical and histological findings without an ethical barrier. Demonstrating interactions between the stent and the wall can help clinicians make a broader diagnosis such as ECG-triggered oversizing and stent-graft characteristics based on patient-specific anatomical location and age. In addition, the results can be used to optimize towards more aortophilic stent grafts.

Comparison of Two Generations of Thoracic Aortic Stent Grafts and Their Impact on Aortic Stiffness in an Ex Vivo Porcine Model

Objective

Little is known about the cardiovascular changes after TEVAR and regarding the impact on aortic stiffness for different stent graft generations specifically, following changes in device design. The present study evaluated the stent graft induced aortic stiffening of two generations of the Valiant thoracic aortic stent graft.

Methods

This was an ex vivo porcine investigation using an experimental mock circulatory loop. Thoracic aortas of young healthy pigs were harvested and connected to the mock circulatory loop. At a 60 bpm heart rate and stable mean arterial pressure, baseline aortic characteristics were obtained. Pulse wave velocity (PWV) was calculated before and after stent graft deployment. Paired and independent sample t tests or their non-parametric alternatives were performed to test for differences where appropriate.

Results

Twenty porcine thoracic aortas were divided into two equal subgroups, in which a Valiant Captivia or a Valiant Navion stent graft was deployed. Both stent grafts were similar in diameter and length. Baseline aortic characteristics did not differ between the subgroups. Mean arterial pressure values did not change after either stent graft, while pulse pressures increased statistically significantly after Captivia (mean 44 ± 10 mmHg to 51 ± 13 mmHg, p = .002) but not after Navion. Mean baseline PWV increased after both Captivia (4.4 ± 0.6 m/s to 4.8 ± 0.7 m/s, p = .007) and Navion (4.6 ± 0.7 m/s to 4.9 ± 0.7 m/s, p = .002). There was no statistically significant difference in the mean percentage increase in PWV for either subgroup (8 ± 4% vs. 6 ± 4%, p = .25).

Conclusion

These experimental findings showed no statistically significant difference in the percentage increase of aortic PWV after either stent graft generation and confirm that TEVAR increases aortic PWV. As a surrogate for aortic stiffness, this calls for further improvements in future thoracic aortic stent graft designs regarding device compliance.

Fluid-structure interaction: Insights into biomechanical implications of endograft after thoracic endovascular aortic repair

Thoracic endovascular aortic repair (TEVAR) has developed to be the most effective treatment for aortic diseases. This study aims to evaluate the biomechanical implications of the implanted endograft after TEVAR. We present a novel image-based, patient-specific, fluid-structure computational framework. The geometries of blood, endograft, and aortic wall were reconstructed based on clinical images. Patient-specific measurement data was collected to determine the parameters of the three-element Windkessel. We designed three postoperative scenarios with rigid wall assumption, blood-wall interaction, blood-endograft-wall interplay, respectively, where a two-way fluid-structure interaction (FSI) method was applied to predict the deformation of the composite stent-wall. Computational results were validated with Doppler ultrasound data. Results show that the rigid wall assumption fails to predict the waveforms of blood outflow and energy loss (EL). The complete storage and release process of blood flow energy, which consists of four phases is captured by the FSI method. The endograft implantation would weaken the buffer function of the aorta and reduce mean EL by 19.1%. The closed curve area of wall pressure and aortic volume could indicate the EL caused by the interaction between blood flow and wall deformation, which accounts for 68.8% of the total EL. Both the FSI and endograft have a slight effect on wall shear stress-related-indices. The deformability of the composite stent-wall region is remarkably limited by the endograft. Our results highlight the importance of considering the interaction between blood flow, the implanted endograft, and the aortic wall to acquire physiologically accurate hemodynamics in post-TEVAR computational studies and the deformation of the aortic wall is responsible for the major EL of the blood flow.

Influence of shape-memory stent grafts on local aortic compliance

The effect of repair techniques on the biomechanics of the aorta is poorly understood, resulting in significant levels of postoperative complications for patients worldwide. This study presents a computational analysis of the influence of Nitinol-based devices on the biomechanical performance of a healthy patient-specific human aorta. Simulations reveal that Nitinol stent-grafts stretch the artery wall so that collagen is stretched to a straightened high-stiffness configuration. The high-compliance regime (HCR) associated with low diastolic lumen pressure is eliminated, and the artery operates in a low-compliance regime (LCR) throughout the entire cardiac cycle. The slope of the lumen pressure–area curve for the LCR post-implantation is almost identical to that of the native vessel during systole. This negligible change from the native LCR slope occurs because the stent-graft increases its diameter from the crimped configuration during deployment so that it reaches a low-stiffness unloading plateau. The effective radial stiffness of the implant along this unloading plateau is negligible compared to the stiffness of the artery wall. Provided the Nitinol device unloads sufficiently during deployment to the unloading plateau, the degree of oversizing has a negligible effect on the pressure–area response of the vessel, as each device exerts approximately the same radial force, the slope of which is negligible compared to the LCR slope of the native artery. We show that 10% oversizing based on the observed diastolic diameter in the mid descending thoracic aorta results in a complete loss of contact between the device and the wall during systole, which could lead to an endoleak and stent migration. 20% oversizing reaches the Dacron enforced area limit (DEAL) during the pulse pressure and results in an effective zero-compliance in the later portion of systole.

Geometric, Biomechanic and Haemodynamic Aortic Abnormalities Assessed by 4D Flow Cardiovascular Magnetic Resonance in Patients Treated by TEVAR Following Blunt Traumatic Thoracic Aortic Injury

OBJECTIVE

Thoracic endovascular aortic repair (TEVAR) is widely used for the treatment of patients with blunt traumatic thoracic aortic injury (BTAI). However, aortic haemodynamic and biomechanical implications of this intervention are poorly investigated. This study aimed to assess whether patients treated by TEVAR following BTAI have thoracic aortic abnormalities in geometry, stiffness, and haemodynamics.

METHODS

Patients with BTAI treated by TEVAR at Vall d'Hebron Hospital between 1999 and 2019 were compared with propensity score matched healthy volunteers (HVs). All subjects underwent cardiovascular magnetic resonance (CMR) comprising a 4D flow CMR sequence. Spatially resolved aortic diameter, length, volume, and curvature were assessed. Pulse wave velocity, distensibility, and longitudinal strain (all measurements of aortic stiffness) were determined regionally. Moreover, advanced haemodynamic descriptors were quantified: systolic flow reversal ratio (SFRR), quantifying backward flow during systole, and in plane rotational flow (IRF), measuring in plane strength of helical flow.

RESULTS

Twenty-six BTAI patients treated by TEVAR were included and matched with 26 HVs. They did not differ in terms of age, sex, and body surface area. Patients with TEVAR had a larger and longer ascending aorta (AAo) and marked abnormalities in local curvature. Aortic stiffness was greater in the aortic segments proximal and distal to TEVAR compared with controls. Moreover, TEVAR patients presented strongly altered flow dynamics compared with controls: a reduced IRF from the distal AAo to the proximal descending aorta and an increased SFRR in the whole thoracic aorta. These differences persisted adjusting for cardiovascular risk factors and were independent of time elapsed since TEVAR implantation.

CONCLUSION

At long term follow up, previously healthy patients who underwent TEVAR implantation following BTAI had increased diameter, length and volume of the ascending aorta, and increased aortic stiffness and abnormal flow patterns in the whole thoracic aorta compared with matched controls. Further studies should address whether these alterations have clinical implications.

Reflected wave intensity increases based on aortic diameter after endovascular aortic therapy in a goat model

Reflected wave increases after endovascular aortic repair (EVAR) in patients with aortic aneurysm. This affects the left ventricular (LV) diastolic function and leads to a poor prognosis. This study aimed to evaluate the relationship between increased reflected wave amplitude and aortic diameter after EVAR. EVAR was performed in seven healthy goats. We assessed wave intensity (WI), aortic diameter, and stiffness parameter β. Moreover, we evaluated the relationship between negative reflected wave (NW, reflected waves toward the heart from the periphery by WI) and other parameters after EVAR. Results showed an increase in stiffness parameter β (3.5 ± 0.3 vs 15.9 ± 4.7, p = 0.018) and a decrease in the change of aortic diameter (6.9 ± 0.7 vs 2.7 ± 0.4%, p = 0.018) after EVAR. The NW was significantly amplified after EVAR from baseline (−589.8 ± 143.4 to  − 1192.3 ± 303.7 mmHg-m/sec³, p = 0.043). The NW showed a significant correlation with maximum aortic diameter (R = 0.707, p = 0.038) and minimum aortic diameter (R = 0.724, p = 0.033). The reflected wave was enhanced after EVAR and was correlated to the aortic diameter at the stent-graft site. It is important to consider that patients with smaller aortic diameters in landing zone who undergo EVAR may develop LV dysfunction.

Determinants of Changes in Arterial Stiffness after Thoracic Endovascular Aortic Repair

BACKGROUND

Aortic stent grafting can cause aortic stiffening and increase pulse wave velocity (PWV), which can potentially affect long-term cardiovascular outcomes. The aim of this study was to clarify the factors contributing to increases in PWV after thoracic endovascular aortic repair (TEVAR).

METHODS

We included 64 patients with thoracic aortic pathology (51 men; mean age, 73 years) who underwent elective TEVAR, in this study. TEVAR was performed for degenerative aortic aneurysm (n = 43) or aortic dissection (n = 21), and the treatment length was 175 ± 52 mm. Brachial-ankle PWV (baPWV) was obtained before and 1 week after TEVAR. Univariable and multivariable logistic regression analyses were used to determine the predictors of increases in baPWV of ≥100 cm/sec after TEVAR.

RESULTS

baPWV increased from 1,851 ± 392 cm/sec to 2,047 ± 479 cm/sec, and the change in baPWV (ΔbaPWV) was 195 ± 339 cm/sec (95% confidence interval, 111-280). Thirty-seven patients (58%) had ΔbaPWV ≥100 cm/sec after TEVAR. In the multivariable analysis, in addition to Δheart rate and Δsystolic blood pressure, age (odds ratio, 1.21/year; 95% confidence interval, 1.05-1.40) and coronary artery disease (odds ratio, 12.0; 95% confidence interval, 1.20-121) were independent determinants of ΔbaPWV ≥100 cm/sec after TEVAR, whereas ΔbaPWV ≥100 cm/sec was not associated with treatment length or device type.

CONCLUSIONS

TEVAR was associated with PWV progression, especially in older patients with coronary artery disease, whereas treatment length or device type was not a predictor of PWV progression after TEVAR.

Aortic Remodeling and Clinical Outcomes Following Thoracic Endovascular Aortic Repair for Blunt Thoracic Aortic Injury

BACKGROUND

There is currently limited data assessing the long-term consequences of thoracic endovascular aortic repair (TEVAR) in otherwise healthy aortic segments remote from the site of endograft coverage. The aim of this study is to retrospectively evaluate aortic remodeling and long-term outcomes of blunt thoracic aortic injury (BTAI) patients treated with TEVAR. Our hypothesis is that significant changes to the aorta proximal to the graft-covered segment are suspected following TEVAR.

METHODS

An institutional review board-approved retrospective review of patients who underwent TEVAR for BTAI at a level I trauma center from 2004 to 2018 was performed. Forty-six patients were identified and of these, 32 patients with high-resolution computed tomographic angiography imaging follow-up were included in the study. Computed tomographic angiography measurements of aortic dimensions and branch vessels proximal, distal, and adjacent to the stent grafted segment were recorded preprocedure and postprocedure and analyzed. Primary device-related outcomes such as birdbeaking, mural thrombus, stent migration, and persistent endoleak were assessed. Patient outcomes including mortality, graft-related morbidity, and need for secondary interventions were also analyzed.

RESULTS

Mean follow-up of the selected patients in the study was 1.52 y (range, 0.06-8.0 y). Following TEVAR, the ascending aortic length increased significantly (mean 5.7 ± 4.6 mm, P < 0.001). The mean diameters of the ascending aorta (1.5 ± 1.5, P < 0.001 mm), the midaortic arch (1.3 ± 1.7 mm, P < 0.001), and proximal and the distal endograft landing zones (1.9 ± 2.1 mm and 2.2 ± 1.6 mm, respectively, P < 0.001) also increased significantly following TEVAR. Clinically relevant device-related outcomes occurred with the presence of endograft infolding and subsequent development of endograft mural thrombus (P < 0.001). The need for secondary intervention following TEVAR for BTAI was associated with endograft mural thrombus (P < 0.05).

CONCLUSIONS

TEVAR for BTAI causes significant geometric changes in the aorta proximal to the stented grafted segment of the aorta. Direct consequences of the graft at the stented segment includes mural thrombus development within the endograft which was associated with the need for secondary intervention. Although clinical significance is yet to be determined, post-TEVAR changes in aortic architecture warrant continued aortic surveillance following BTAI.

Decreased biventricular function following thoracic endovascular aortic repair

OBJECTIVES

Preclinical studies have suggested acute stiffening of the aorta following experimental thoracic endovascular aortic repair (TEVAR), resulting in acute elevated pulse pressure, hypertension and possibly heart failure. The aim of this study was to evaluate cardiac remodelling following TEVAR.

METHODS

From 2005 to 2018, 519 TEVAR procedures were performed at a single centre. Transthoracic echocardiography was performed pre- and post-TEVAR in 31 patients without previous replacement of the thoracic aorta. Patient characteristics, drug information, radiographic and follow-up data were evaluated. Aortic details were measured in multiplanar reconstruction.

RESULTS

Transthoracic echocardiography was performed 2 ± 2 years after TEVAR. At this time, patients received significantly more antihypertensive drugs compared to the pre-TEVAR intake (beta-blocker therapy: P = 0.037; calcium channel blocker: P = 0.022). Compared to pre-TEVAR, there was a significant reduction in the left ventricular ejection fraction (P = 0.008) and tricuspid annular plane systolic excursion (P = 0.013) post-TEVAR. A significant increase in the left ventricular mass was not detected in this study (P = 0.95). The mean distance of 163 ± 66 mm of the descending aorta was covered.

CONCLUSIONS

This study suggests negative cardiac remodelling with a decrease in the left and right ventricular function following TEVAR despite an increase in oral antihypertensive medication. The impact of stiffer endovascular grafts compared with the native aortic wall should be considered by endovascular specialists and manufacturers.

Geometric Deformations of the Thoracic Aorta and Supra-Aortic Arch Branch Vessels Following Thoracic Endovascular Aortic Repair

Objective:

To utilize 3-D modeling techniques to better characterize geometric deformations of the supra-aortic arch branch vessels and descending thoracic aorta after thoracic endovascular aortic repair.

Methods:

Eighteen patients underwent endovascular repair of either type B aortic dissection (n = 10) or thoracic aortic aneurysm (n = 8). Computed tomography angiography was obtained pre- and postprocedure, and 3-D geometric models of the aorta and supra-aortic branch vessels were constructed. Branch angle of the supra-aortic branch vessels and curvature metrics of the ascending aorta, aortic arch, and stented thoracic aortic lumen were calculated both at pre- and postintervention.

Results:

The left common carotid artery branch angle was lower than the left subclavian artery angles preintervention ( P < .005) and lower than both the left subclavian and brachiocephalic branch angles postintervention ( P < .05). From pre- to postoperative, no significant change in branch angle was found in any of the great vessels. Maximum curvature change of the stented lumen from pre- to postprocedure was greater than those of the ascending aorta and aortic arch ( P < .05).

Conclusion:

Thoracic endovascular aortic repair results in relative straightening of the stented aortic region and also accentuates the native curvature of the ascending aorta when the endograft has a more proximal landing zone. Supra-aortic branch vessel angulation remains relatively static when proximal landing zones are distal to the left common carotid artery.

Changes in aortic pulse wave velocity of four thoracic aortic stent grafts in an ex vivo porcine model

Objectives

Thoracic endovascular aortic repair (TEVAR) has been shown to lead to increased aortic stiffness. The aim of this study was to investigate the effect of stent graft type and stent graft length on aortic stiffness in a controlled, experimental setting.

Methods

Twenty porcine thoracic aortas were connected to a pulsatile mock loop system. Intraluminal pressure was recorded at two sites in order to measure pulse wave velocity (PWV) for each aorta: before stent graft deployment (t₁); after deployment of a 100-mm long stent graft (t₂); and after distal extension through deployment of a second 100-mm long stent graft (t₃). Four different types of stent grafts (Conformable Gore^® TAG^® Device, Bolton Relay^® Device, Cook Zenith Alpha^™, and Medtronic Valiant^®) were evaluated.

Results

For the total cohort of 20 aortas, PWV increased by a mean 0.6 m/s or 8.9% of baseline PWV after deployment of a 100-mm proximal stent graft (P<0.001), and by a mean 1.4 m/s or 23.0% of baseline PWV after distal extension of the stent graft (P<0.001). Univariable regression analysis showed a significant correlation between aortic PWV and extent of stent graft coverage, (P<0.001), but no significant effect of baseline aortic length, baseline aortic PWV, or stent graft type on the percentual increase in PWV at t₂ or at t₃.

Conclusions

In this experimental set-up, aortic stiffness increased significantly after stent graft deployment with each of the four types of stent graft, with the increase in aortic stiffness depending on the extent of stent graft coverage.