Morphometric Analysis of the Aorto-Esophageal Relationship in Swine for Trans-Esophageal Aortic Blood Flow Occlusion

Background Trans-esophageal aortic blood flow occlusion (TEABO) is an emerging technology undergoing laboratory research that offers a strategy for temporary hemorrhage control. The purpose of this study was to evaluate the anatomical relationship between the esophagus and descending thoracic aorta in two breeds of swine to support a porcine model for future TEABO investigations. Methods Thoracoabdominal CT scans were compared in Hanford miniature swine and Yorkshire swine. Measurements were taken at the five vertebral levels proximal to the gastroesophageal junction. Data collected included the distance between the center of the esophagus and the center of the descending aorta, the angle between the vertebral column, descending aorta, and esophagus, and the length the thoracic esophagus travels anteriorly to the descending aorta. Results Ten Hanford swine and ten Yorkshire swine were compared. In Hanford swine, the distal thoracic esophagus travels anteriorly to the descending aorta for a mean distance of 11.5 ± 2.3 cm. In Yorkshire swine, the thoracic esophagus travels to the right of the descending aorta. The mean angle between the vertebral body, descending aorta, and esophagus was 79.6 to 97.8 degrees higher in Hanfords compared to Yorkshires (p<0.0001 at all five vertebral levels compared). The mean distance between the esophagus and descending aorta was 0.2 to 0.6 cm higher in Hanfords compared to Yorkshires with a significant difference found at only two vertebral levels (p=0.01 and p=0.02). Conclusion Hanford miniature swine possess an aorto-esophageal relationship comparable to humans and should be the preferred animal model for TEABO studies.

Does the Intraluminal Thrombus Provoke the Rupture of the Abdominal Aortic Aneurysm Wall?

The role of intraluminal thrombus (ILT) in the rupture of abdominal aortic aneurysms (AAA) is controversial, and it is unclear whether it increases or decreases the risk of rupture. This research aims to find a clear answer to this question. Previous computer modelling suggests that an ILT lowers oxygen dissemination to the AAA wall, contributing to wall thinning. The methodology used in this study determines the amount of oxygen reaching the aneurysm wall after passing through the ILT by using the porous nature of the ILT to recreate the condition as closely as feasible. Using computed tomographic images, patient-specific three-dimensional (3D) AAA geometries were recreated. Modelling blood and oxygen flow in AAA was obtained using a computational fluid dynamics (CFD) approach. Our findings indicated that the oxygen volume percentage had completely reached the aneurysm wall. Only at the inlet and outflow did the greatest wall shear stress (WSS) occur, with a significant drop in the central region of the aneurysm wall. CFD was used to calculate the velocity, pressure, and WSS of aortic blood flow. ILT had no effect on oxygen flow to the aneurysm wall, disproving the theory that it produces local hypoxia.

Non-intrusive data-driven ROM framework for hemodynamics problems

Reduced order modeling (ROM) techniques are numerical methods that approximate the solution of parametric partial differential equation (PED) by properly combining the high-fidelity solutions of the problem obtained for several configurations, i.e. for several properly chosen values of the physical/geometrical parameters characterizing the problem. By starting from a database of high-fidelity solutions related to a certain values of the parameters, we apply the proper orthogonal decomposition with interpolation (PODI) and then reconstruct the variables of interest for new values of the parameters, i.e. different values from the ones included in the database. Furthermore, we present a preliminary web application through which one can run the ROM with a very user-friendly approach, without the need of having expertise in the numerical analysis and scientific computing field. The case study we have chosen to test the efficiency of our algorithm is represented by the aortic blood flow pattern in presence of a left ventricular (LVAD) assist device when varying the pump flow rate.

End-organ saturations correlate with aortic blood flow estimates by echocardiography in the extremely premature newborn – an observational cohort study

Background Near-infrared spectroscopy (NIRS) measures of cerebral saturation (Csat) and renal saturation (Rsat) in extreme premature newborns may be affected by systemic blood flow fluctuations. Despite increasing clinical use of NIRS to monitor tissue saturation in the premature infant, validation of NIRS measures as a correlate of blood flow is still needed. We compared echocardiography (ECHO) derived markers of ascending aorta (AscAo) and descending aorta (DesAo) blood flow with NIRS measurements obtained during the ECHO. Methods Newborns < 29 weeks’ gestation (2013–2017) underwent routine NIRS monitoring. Csat, Rsat and systemic saturation at the time of ECHO were retrospectively analyzed and compared with Doppler markers of aortic flow. Renal and cerebral fractional tissue oxygen extraction (rFTOE and cFTOE, respectively) were calculated. Mixed effects models evaluated the association between NIRS and Doppler markers. Results Forty-nine neonates with 75 Csat-ECHO and 62 Rsat-ECHO observations were studied. Mean post-menstrual age was 28.3 ± 3.8 weeks during the ECHO. Preductal measures including AscAo velocity time integral (VTI) and AscAo output were correlated with Csat or cFTOE, while postductal measures including DesAo VTI, DesAo peak systolic velocity, and estimated DesAo output were more closely correlated with Rsat or rFTOE. Conclusions NIRS measures are associated with aortic blood flow measurements by ECHO in the extremely premature population. NIRS is a tool to consider when following end organ perfusion in the preterm infant.

The Accuracy and Reliability of Cardiac Output Assessment by Measuring Descending Aortic Blood Flow in Patients Undergoing Cardiac Surgery

Background To investigate the accuracy and reliability of cardiac output (CO) assessment by transesophageal echocardiographic (TEE) measuring descending aortic blood flow (DABF) in patients undergoing cardiac surgery under cardiopulmonary bypass (CPB). And the influence of DABF/CO on the accuracy and reliability of CO assessment were also analyzed. Methods Paired CO measured by both thermodilution (TCO) and Doppler method (DCO) were obtained before incision, immediately after CPB, 15 minutes after CPB, 30 minutes after CPB, 45 minutes after CPB, and at the end of surgery. The DCO was converted from TEE measured DABF using theoretical proportion (70%) of DABF/CO. Regression analysis, Bland-Altman graph, and Polar plot were used to analyze the correlation and agreement between the CO measurements by the two methods. Parameters were compared by one-way ANOVA among different time points. Results A total of 132 pairs of CO measurements were obtained from 22 patients. The average proportion of DABF/TCO ranged from 54% before CPB to 63% after CBP. A good correlation between DCO and TCO (r = 0.81) was found. The Bland-Altman analysis showed a large positive bias between the TCO and DCO. The Polar plot also showed a poor concordance between changes of DCO and TCO. The proportion of DABF/TCO had a mild negative correlation with systemic vascular resistance index (SVRI) but not with cardiac output index (CI). Conclusions The CO, converted from TEE measured DABF, was underestimated in patients undergoing cardiac surgery. The varied proportion between DABF and CO mainly influenced the accuracy and reliability of CO assessment. Trial registration: Chinese Clinical Trials Register Identifier: ChiCTR-OCS-12002789 (retrospective registered). Date: 2012.12.21

Pediatric Sized REBOA Catheter Testing in a Pulsatile Aortic Flow Model

Background – Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) in the management of pediatric abdomino-pelvic hemorrhage from trauma or iatrogenic injury is limited by a lack of appropriately sized balloon catheters that can be delivered through less than a 7 French sheath. Methods – We bench tested the occlusion capability of eight commercially available balloon catheters deliverable through 4Fr, 5Fr and 6Fr sheaths in an anatomic pulsatile flow model of the pediatric aorta with variable luminal diameters (5mm, 6mm, 7mm, 8mm, 9mm, 10mm, and 12mm). Inflated balloon migration and the deflated balloon’s effect on aortic flow were recorded. The flow chamber was calibrated to approximate size-appropriate physiologic aortic blood flow. Results – Seven of eight devices were able to occlude the test lumen diameter corresponding to their manufacture specifications. Deflated luminal flow restriction in the smallest test lumen was lowest in the Fogarty devices (0-3%) followed by Cordis (8-10%) and Numed (14-26%) devices. The Fogarty devices demonstrated the most distal migration (10-15mm) followed by Numed (1-5mm). Device migration was undetectable in the Cordis devices. Conclusion – There are commercially available balloon catheters, deliverable through smaller than 7Fr sheaths which can occlude pediatric sized aortic test lumens in the setting of physiologic pulsatile flow. These results will help inform future research, device development and practice in the field of pediatric REBOA.

Bicuspid aortic valve fusion length correlates with maximum aortic diameter and heamodynamic abnormalities: a 4D flow CMR study

Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Guala A. received funding from the Spanish Ministry of Science, Innovation and Universities. Background Bicuspid aortic valve (BAV), a congenital heart defect, is associated with ascending aorta dilation, possibly via alteration of aortic blood flow [1]. In BAV abnormal flow condition have been associated with aortic extracellular matrix dysregulation and elastic fiber degeneration [2]. Current morphological classification of BAV patients with aortic valve with a single fusion between two adjacent leaflets does not allow for risk stratification. Purpose This research work tested whether the extent of fusion between leaflets is related to AAo diameter and flow alterations. Methods Ninety BAV patients free from moderate and severe aortic valve disease and with no previous aortic or aortic valve surgery or replacement were prospectively enrolled. A comprehensive magnetic resonance protocol comprised a stack of double-oblique 2D balanced steady-state free-precession (bSSFP) cine CMR of the aortic valve, which was used to measure the length of the fusion between leaflets, a cine CMR at the level of the pulmonary bifurcation to assess aortic diameter and 4D flow MRI sequence to assess flow characteristics and regional stiffness [3]. Jet angle and flow radial displacement, quantifying the extent of flow eccentricity, and systolic flow reversal ratio (SFRR), assessing the relative amount of backward flow during systole, were computed at 8 equidistant planes in the ascending aorta and 4 equidistant planes in the aortic arch [4]. A two-tailed p-value &lt; 0.05 was considered statistically significant. Results The length of leaflet fusion varied widely (median 7.7 mm, inter-quartile range [5.5; 10.2]), Table 1). In bivariate analysis, fusion length was also associated to ascending aortic diameter (R = 0.391, p &lt; 0.001), age (R = 0.313, p = 0.005) and body surface area (R = 0.396, p &lt; 0.001). It was also positively related to flow abnormalities: like displacement in the proximal and distal ascending aorta, jet angle in the mid ascending aorta, and SFRR in the ascending aorta and the aortic arch (see Figure 1). The association between fusion length and ascending aorta diameter persisted in multivariate analysis after correction for age (p = 0.006). Conclusions Bicuspid aortic valve fusion extent varies greatly and it is associated with aortic diameter, possibly through flow alterations. Prospective longitudinal studies are needed to establish whether fusion length may allow for risk stratification in bicuspid aortic valve patients.

Thoracic endovascular aortic repair for recurrent stroke due to atheromatic plaque in the proximal descending aorta: a case report

Background Diastolic retrograde flow in the descending aorta (DAo) may occur in the presence of atherosclerosis and may be overlooked as a mechanism of retrograde embolization in patients with stroke. We performed thoracic endovascular aortic repair (TEVAR) in a patient with recurrent cerebral infarctions for treatment of aortic aneurysm with atheromatic plaque, which was considered as the source of embolism. Case presentation A 56-year-old man with a history of idiopathic thrombocytopenia and hypertension was referred to our hospital with paralysis of the right upper and lower limbs. Multiple cerebral infarctions were found and treated; however, 1 month later, another cerebral infarction developed. A small saccular aortic aneurysm with plaque was found beyond the left subclavian artery, and this site was deemed as the source of embolism. We performed TEVAR to prevent further recurrence of cerebral infarctions. No cerebral infarctions were observed 6 months post-operation. Conclusions TEVAR is a useful treatment for not only aortic aneurysm and dissection, but also cerebral infarctions caused by an embolic source proximal to the DAo due to retrograde aortic blood flow.

Doppler examination of aorta after therapeutic hypothermia and administering MSCs in experimental myocardial infarction

Background. At present, there are attempts aimed at repairing the myocardium affected by acute myocardial infarction (MI) via biologically sourced drugs, which are able to stimulate reparative regeneration, including the use of mesenchymal stromal cells (MSCs). On the other hand, therapeutic hypothermia initially after the occurrence of impaired blood flow in the coronary arteries aids in reducing the level of metabolism in cardiomyocytes and, accordingly, suppressing the formation of free radicals and inhibiting apoptosis. Purpose – рerforming and analysing Doppler sonography of the ascending aorta in rats with experimental MI in order to assess the systolic function of the left ventricular myocardium influenced by the combined use of therapeutic hypothermia and administering allogeneic MSCs. Materials and methods. The study involved 90 outbred white rats weighing 240–270 g. Myocardial infarction was reproduced by ligating the left coronary artery. Therapeutic hypothermia was performed in a cold chamber, 60 minutes long. The local skin temperature of the neck area was maintained at +4 оС. A suspension of allogeneic cryopreserved MSCs of the placenta was administered once intravenously. Sonography of the ascending aorta on day 7 and day 30 after ligating the coronary artery was carried out by means of «Сономед 500» ultrasound scanner in B-mode with the Doppler (PW-mode). Results. Studying the aortic blood flow showed that on day 7 after ligating the coronary artery, rats had a decrease in max systolic velocity and a tendency to increase diastolic blood flow velocity. Those changes influenced the pulsatility index and systolic-diastolic ratio. A 19 % decrease in the Stewart index confirmed the development of systolic dysfunction in the control group, the severity of which did not decrease until day 30 of the experiment. The impact of allogeneic MSCs on the process of remodeling the heart of rats after ligating the left coronary artery was evident on day 7 (acute stage of myocardial infarction) via abnormally low (below control) blood flow in the aorta with complete hemodynamics restoring on day 30 of the experiment. The combination of therapeutic hypothermia and administering allogeneic MSCs aided in the minimal deviation of hemodynamic parameters from the normal range. On day 7, there was only an increase in the average aortic blood flow rate by 29%, and a decrease in systolic-diastolic ratio by 12% compared to the corresponding normal range, suggesting compensation of the pumping function of the myocardium. Conclusions. Doppler assessment of systolic and diastolic blood flow velocities in the ascending aorta of rats makes it possible to indirectly record the presence and severity of systolic dysfunction of the left ventricle and follow up myocardial contractile function affected by MI. The combination of therapeutic hypothermia and administering allogeneic MSCs after ligating the left coronary artery helps to maintain hemodynamic parameters in the aorta at a level close to normal range during the acute phase of myocardial infarction as well as at the stage of scarring.

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.