Arch Flow Research Articles

Hemodynamic and anatomic changes after fetal aortic valvuloplasty are associated with procedural success and postnatal biventricular circulation.

There are minimal data characterizing the trajectory of left heart growth and hemodynamics following fetal aortic valvuloplasty (FAV). This retrospective study included patients who underwent FAV between 2000 and 2019, with echocardiograms performed pre-FAV, immediately post-FAV, and in late gestation. Of 118 fetuses undergoing FAV, 106 (90%) underwent technically successful FAV, of which 55 (52%) had biventricular circulation. Technically successful FAV was associated with improved aortic valve growth (p<0.001), sustained antegrade aortic arch (AoA) flow (p=0.02), improved mitral valve (MV) inflow pattern (p=0.002), and favorable patent foramen ovale (PFO) flow pattern (p=0.004) from pre-FAV to late gestation. Compared to patients with univentricular outcome, patients with biventricular outcome had less decrement in size of the left ventricle (LV) (p<0.001) and aortic valve (p=0.005), as well as more physiologic PFO flow (p<0.001) and antegrade AoA flow (p<0.001) from pre-FAV to late gestation. In multivariable analysis, echocardiographic predictors of biventricular outcome were less decline in LV end diastolic dimension (p<0.001), improved PFO flow (p=0.004), and sustained antegrade AoA flow (p=0.002) from pre-FAV to late gestation. Stabilization of left heart growth and improved hemodynamics following successful FAV through late gestation are associated with postnatal biventricular circulation.

Fluid Mechanics of Fetal Left Ventricle During Aortic Stenosis with Evolving Hypoplastic Left Heart Syndrome

In cases of fetal aortic stenosis and evolving Hypoplastic Left Heart Syndrome (feHLHS), aortic stenosis is associated with specific abnormalities such as retrograde or bidirectional systolic transverse arch flow. Many cases progressed to hypoplastic left heart syndrome (HLHS) malformation at birth, but fetal aortic valvuloplasty can prevent the progression in many cases. Since both disease and intervention involve drastic changes to the biomechanical environment, in-vivo biomechanics likely play a role in inducing and preventing disease progression. However, the fluid mechanics of feHLHS is not well-characterized. Here, we conduct patient-specific echocardiography-based flow simulations of normal and feHLHS left ventricles (LV), to understand the essential fluid dynamics distinction between the two cohorts. We found high variability across feHLHS cases, but also the following unifying features. Firstly, feHLHS diastole mitral inflow was in the form of a narrowed and fast jet that impinged onto the apical region, rather than a wide and gentle inflow in normal LVs. This was likely due to a malformed mitral valve with impaired opening dynamics. This altered inflow caused elevated vorticity dynamics and wall shear stresses (WSS) and reduced oscillatory shear index at the apical zone rather than mid-ventricle. Secondly, feHLHS LV also featured elevated systolic and diastolic energy losses, intraventricular pressure gradients, and vortex formation numbers, suggesting energy inefficiency of flow and additional burden on the LV. Thirdly, feHLHS LV had poor blood turnover, suggesting a hypoxic environment, which could be associated with endocardial fibroelastosis that is often observed in these patients.

Hemodynamic patterns associated with activation of bradykinin-sensitive pericardial afferents.

The heart is endowed with reflexogenic areas capable of powerful blood pressure responses. Relatively little work has studied the hemodynamic mechanisms underlying these responses and whether these are sexually dimorphic. We hypothesized that activation of bradykinin-sensitive pericardial afferents would produce a sexually dimorphic cardiac output response. Male and female Sprague Dawley rats were anesthetized and instrumented with catheters for recording arterial pressure, with an aortic arch flow probe to record cardiac output and with a catheter in the pericardial sac. Mean arterial pressure (MAP), cardiac index (CI) and total peripheral resistance index (TPRI) responses to pericardial bradykinin injection (0.1, 1 μg/kg) were recorded. Pericardial bradykinin injection caused similar increases in MAP in male and female rats. However, the underlying hemodynamic patterns varied considerably. We identified a cluster of CI responders and TPRI responders in both male and female rats. Within CI responders, females exhibited greater CI increases than males. Conversely, in TPRI responders, males exhibited a greater TPRI increase than females. We conclude that aggregate activation of bradykinin-sensitive pericardial afferents is associated with a relatively uniform pressor response but different hemodynamic patterns with males exhibiting a more robust vascular response and females a more robust cardiac output response.

A mouse model of hypoplastic left heart syndrome demonstrating left heart hypoplasia and retrograde aortic arch flow.

ABSTRACTIn hypoplastic left heart syndrome (HLHS), the mechanisms leading to left heart hypoplasia and their associated fetal abnormalities are largely unknown. Current animal models have limited utility in resolving these questions as they either do not fully reproduce the cardiac phenotype, do not survive to term and/or have very low disease penetrance. Here, we report the development of a surgically induced mouse model of HLHS that overcomes these limitations. Briefly, we microinjected the fetal left atrium of embryonic day (E)14.5 mice with an embolizing agent under high-frequency ultrasound guidance, which partially blocks blood flow into the left heart and induces hypoplasia. At term (E18.5), all positively embolized mice exhibit retrograde aortic arch flow, non-apex-forming left ventricles and hypoplastic ascending aortas. We thus report the development of the first mouse model of isolated HLHS with a fully penetrant cardiac phenotype and survival to term. Our method allows for the interrogation of previously intractable questions, such as determining the mechanisms of cardiac hypoplasia and fetal abnormalities observed in HLHS, as well as testing of mechanism-based therapies, which are urgently lacking.

Fetal Echocardiography in Predicting Postnatal Outcome in Borderline Left Ventricle.

Prenatal prediction of postnatal univentricular versus biventricular circulation in patients with borderline left ventricle (bLV) remains challenging. This study investigated prenatal fetal echocardiographic parameters and postnatal outcome of patients with a prenatally diagnosed bLV. We report a retrospective study of bLV patients at four prenatal centers with a follow-up of one year. BLV was defined as z-scores of the left ventricle (LV) between -2 and -4. Single-ventricle palliation (SVP), biventricular repair (BVR), and no surgical or catheter-based intervention served as the dependent outcome. Prenatal ultrasound parameters were used as independent variables. Cut-off values from receiver operating characteristic curves (ROC) were determined for significant discrimination between outcomes. A total of 54 patients were diagnosed with bLV from 2010 to 2018. All were live births. Out of the entire cohort, 8(15 %) received SVP, 34 (63 %) BVR, and 12 (22 %) no intervention. There was no significant difference with regard to genetic or extracardiac anomalies. There were significantly more patients with endocardial fibroelastosis (EFE) in the SVP group compared to the BVR group (80 % vs. 10 %), (p < 0.001). Apex-forming LV (100 % vs. 70 %) and lack of retrograde arch flow (20 % vs. 80 %) were associated with no intervention (p < 0.001). With respect to BVR vs. SVP, the LV sphericity index provided the highest specificity (91.7 %) using a cutoff value of ≤ 0.5. The majority of bLV patients maintained biventricular circulation. EFE, retrograde arch flow, and LV sphericity can be helpful parameters for counseling parents and further prospective studies can be developed.

Fetal cerebrovascular response to maternal hyperoxygenation in congenital heart disease: effect of cardiac physiology.

Fetal cerebrovascular resistance is influenced by several factors in the setting of intact autoregulation to allow for normal cerebral blood flow and oxygenation. Maternal hyperoxygenation (MH) allows for acute alterations in fetal physiology and can be a tool to test cerebrovascular reactivity in late-gestation fetuses. In this study, we utilized MH to evaluate cerebrovascular reactivity in fetuses with specific congenital heart disease (CHD). This was a cross-sectional study of fetuses with complex CHD compared to controls without CHD. CHD cases were grouped according to physiology into: left-sided obstructive lesion (LSOL), right-sided obstructive lesion (RSOL) or dextro-transposition of the great arteries (d-TGA). Subjects underwent MH testing during the third-trimester fetal echocardiogram. The pulsatility index (PI) was calculated for the fetal middle cerebral artery (MCA), umbilical artery (UA) and branch pulmonary artery (PA). The change in PI from baseline to during MH was compared between each CHD group and controls. Sixty pregnant women were enrolled (CHD, n = 43; control, n = 17). In the CHD group, there were 27 fetuses with LSOL, seven with RSOL and nine with d-TGA. Mean gestational age was 33.9 (95% CI, 33.6-34.2) weeks. At baseline, MCA-PI Z-score was lowest in the LSOL group (-1.8 (95% CI, -2.4 to -1.2)) compared with the control group (-0.8 (95% CI, -1.3 to -0.3)) (P = 0.01). In response to MH, MCA-PI Z-score increased significantly in the control and d-TGA groups but did not change significantly in the LSOL and RSOL groups. The change in MCA-PI Z-score was significantly higher in the control group than in the LSOL group (0.9 (95% CI, 0.42-1.4) vs 0.12 (95% CI, -0.21 to 0.45); P = 0.03). This difference was more pronounced in the LSOL subgroup with retrograde aortic arch flow. Branch PA-PI decreased significantly in response to MH in all groups, with no difference in the change from baseline to MH between the groups, while UA-PI was unchanged during MH compared with at baseline. The fetal cerebrovascular response to MH varies based on the underlying CHD diagnosis, suggesting that cardiovascular physiology may influence the autoregulatory capacity of the fetal brain. Further studies are needed to determine the clinical implications of these findings on long-term neurodevelopment in these at-risk children. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Late gestation predictors of a postnatal biventricular circulation after fetal aortic valvuloplasty.

Fetal aortic valvuloplasty (FAV) for severe aortic stenosis (AS) has shown promise in averting progression to hypoplastic left heart syndrome. After FAV, predicting which fetuses will achieve a biventricular (BiV) circulation after birth remains challenging. Identifying predictors of postnatal circulation on late gestation echocardiography will improve parental counseling. Liveborn patients who underwent FAV and had late gestation echocardiography available were included (2000-2017, n=96). Multivariable logistic regression and classification and regression tree analysis were utilized to identify independent predictors of BiV circulation. Among 96 fetuses, 50 (52.1%) had BiV circulation at the time of neonatal discharge. In multivariable analysis, independent predictors of biventricular circulation included left ventricular (LV) long axis z-score (OR 3.2, 95% CI 1.8-5.7, p<0.001), LV ejection fraction (OR 1.3, 95% CI 1.0-1.8, p=0.023), anterograde aortic arch flow (OR 5.0, 95% CI 1.2-20.4, p=0.024), and bidirectional or right-to-left foramen ovale flow (OR 4.6, 95% CI 1.4-15.8, p=0.015). Several anatomic and physiologic parameters in late gestation were found to be independent predictors of BiV circulation after FAV. Identifying these predictors adds to our understanding of LV growth and hemodynamics after FAV and may improve parental counseling.

Aortic cannula orientation and flow impacts embolic trajectories: computational cardiopulmonary bypass.

Emboli events are associated with the aortic cannula insertion and final position in the ascending aorta. However, the impact of subtle changes in aortic cannula movement and flow influencing embolic transport throughout the aortic arch is not well understood. The present study evaluated the aortic cannula's outflow and orientation effect on emboli entering the aortic branch arteries. A simplified aortic computational model was anteriorly cannulated in the distal ascending aorta with a 21-French straight aortic cannula, and two orientations were analysed by injecting gaseous and solid emboli at pump flows 2, 3 and 5 L/minute. The first aortic cannula orientation (forward flow cannula) was directed towards the lesser curvature. The second aortic cannula orientation (rear flow cannula) was tilted slightly backwards by 15°, providing flow in the retrograde direction. Forward flow cannula produced a primary arch flow, whereas rear flow cannula produced a secondary arch flow resulting in four times longer emboli arch resident times than forward flow cannula. The rear flow cannula had the highest percentage of gaseous emboli entering the brachiocephalic artery of 8%, 12% and 36% (at 2, 3 and 5 L/minute, respectively). Rear flow cannula provided a positive aortic branch arterial flow at all pump flows, whereas at forward flow cannula, the brachiocephalic artery experienced retrograde flows of -1.0% (3 L/minute) and -4.0% (5 L/minute), with the left common carotid -0.23% (5 L/minute). No significant number of solid emboli entered the aortic branch arteries. This numerical study illustrated distinct trajectory behaviours between gaseous and solid emboli where slight changes in aortic cannula orientation influenced idealised emboli direction with higher pump flows magnifying the effects.

PC058. A Novel Aortic Arch Flow Model to Test the Efficacy of Cerebral Embolic Protection Devices Using Transcranial Doppler

Clinically apparent stroke occurs in up to 6% of patients undergoing thoracic endovascular aortic repair and up to 4% of patients undergoing carotid artery stenting. However, clinically silent cerebral infarction is seen on postoperative diffusion-weighted magnetic resonance imaging in >60% of patients undergoing thoracic endovascular aortic repair and leads to an increased risk of future stroke and dementia. Embolic protection devices are associated with lower stroke rates and smaller volume of ischemic lesions on diffusion-weighted magnetic resonance imaging. We created a novel aortic arch flow model and tested the efficacy of the FilterWire EZ (Boston Scientific, Marlborough, Mass) using transcranial Doppler ultrasound. By employing a three-dimensional printed aortic arch, we created a closed-circuit flow model that can simulate continuous and pulsatile blood flow (Fig, A-C). Dissolved cornstarch particles simulate circulating red and white blood cells, which typically range in size from 6 to 15 μm, to provide a background signal for detection of solid and gaseous emboli on transcranial Doppler ultrasound (Fig, D and E). A 38-μm filter placed in series ensures that injected microparticles do not recirculate and the circuit is deaired. We then prepared and deployed a FilterWire EZ, a uniform 110-μm pore filter commonly used during carotid artery stenting, according to the instructions for use. Embozene Microspheres (Boston Scientific) of known sizes were diluted in saline to 1 mL of particles per 10 mL of solution. High-intensity transient signals (HITS) were recorded during filter deployment, injection of 1 mL of solution, and filter retrieval. This process was repeated for Embozene particles of 75-, 100-, 250-, and 400-μm diameters. Each continuous 1-second shower of emboli was counted as 15 HITS. Despite preparation of the FilterWire EZ according to instructions for use, there were on average 41 ± 7 (range, 31-49) HITS during filter deployment and 7 ± 7 (range, 1-17) HITS during filter retrieval. Average number of HITS during injection was 87 ± 130 (range, 4-315), and more HITS were seen distal to the filter on injection of microparticles that were smaller than the 110-μm pore size (142 ± 150 vs 5 ± 1; P = .31). Mean velocity (cm/s) of the fluid decreased by 18% ± 2% after filter deployment and 50% ± 34% during injection of microparticles and returned to baseline after filter retrieval. We created and validated a novel aortic arch flow model. HITS were seen during all stages of the procedure using the FilterWire EZ. This model can be used to test the efficacy of all available embolic protection devices and methods of deairing stent grafts.

Head Biometry in Fetuses with Isolated Congenital Heart Disease.

Purpose Altered cerebral hemodynamics are involved in changes in head biometry in fetuses with congenital heart disease (CHD). We compared head growth in different CHD groups with published normative values and investigated whether CHD groups differ from each other in terms of head circumference (HC) development over gestational age (GA). Materials and Methods Retrospective cohort study consisting of 248 CHD fetuses. Subgroups were generated according to the expected ascending aorta oxygen saturation: Low placental blood content (BC) and therefore low oxygen delivery to the brain (group 1: n = 108), intermediate placental and systemic BC due to intracardiac mixing of blood (group 2: n = 103), high placental BC (group 3: n = 13) and low placental BC and low oxygen delivery to the brain without mixing of blood (group 4: n = 24). Furthermore, group 1 was divided into antegrade (n = 34) and retrograde (n = 74) flow through the aortic arch. Comparisons were made at a GA of 22, 30 and 38 weeks. Results Estimated values of zHC (z-score transformed) were not significantly different between the four CHD groups at the three time points in gestation (all p > 0.05). Within group 1 fetuses with retrograde aortic arch flow showed a significant negative association between HC and GA compared to reference values (b = –0.054, p Conclusion Our data do not confirm that CHD fetuses in general have a significantly smaller HC. HC becomes smaller throughout gestation depending on the direction of aortic arch flow.

Increased rotational flow in the proximal aortic arch is associated with its dilation in bicuspid aortic valve disease.

Aortic dilation in bicuspid aortic valve (BAV) might extend to the proximal arch. Arch flow dynamics and their relationship with this segment dilation are still unexplored. Using 4D-flow cardiovascular magnetic resonance, we analysed flow dynamics in the arch for each BAV morphotype and their association with this segment dilation. One hundred and eleven BAV patients (aortic diameters ≤55 mm, non-severe valvular disease), 21 age-matched tricuspid aortic valve (TAV) patients with dilated arch and 24 healthy volunteers (HV) underwent 4D-flow. BAV were classified per fusion morphotype: 75% right-left (RL-BAV), and per arch dilation: 57% dilated, mainly affecting the right-noncoronary (RN) BAV (86% dilated vs. 47% in RL-BAV). Peak velocity, jet angle, normalized displacement, in-plane rotational flow (IRF), wall shear stress, and systolic flow reversal ratio (SFRR) were calculated along the thoracic aorta. ANCOVA and multivariate linear regression analyses were used to identify correlates of arch dilation. BAV had higher rotational flow and eccentricity than TAV in the proximal arch. Dilated compared with non-dilated BAV had higher IRF being more pronounced in the RN-morphotype. RN-BAV, IRF, and SFRR were independently associated with arch dilation. Aortic stenosis and male sex were independently associated with arch dilation in RL-BAV. Flow parameters associated with dilation converged to the values found in HV in the distal arch. Increased rotational flow could explain dilation of the proximal arch in RN-BAV and in RL-BAV patients of male sex and with valvular stenosis. These patients may benefit from a closer follow-up with cardiac magnetic resonance or computed tomography.

Strokes in LVADS. Insights from Modelling Flow in the Circle of Willis

Purpose Strokes are a serious complication of LVADs and are especially known to occur with hypertension. Hypoperfusion of the innominate artery has been described in LVADS, especially in smaller diameter outflow grafts. (1) The normal circle of Willis is often incomplete and Hypoplasia of the posterior communicating artery is a common variant. Modelling flow in the circle of Willis may shed light on strokes in LVADS ( 1) Effect of Outflow Graft Size on Flow in the Aortic Arch and Cerebral Blood Flow in Continuous Flow Pumps: Possible Relevance to Strokes.ASAIO 63:2,144-149 Methods The arterial pulse wave propagation model was used to compare pressure and flow in the circle of Willis for 1.Normal pulsatile and nonpulsatile flow at 5 litres per minute 2. varying degrees of pulsatility in LVADS 3.Flow in the right and left cerebral arteries when the right carotid artery is having no flow, with and without a patent right posterior communicating artery Results The mean pressure in all the vessels is significantly higher for a non pulsatile compared to a pulsatile flow . Mean pressures are lower with increasing pulsatility. Absence of Posterior communicating AND Right common carotid artery flow lowered the pressure and flow drastically in the all the Right sided cerebral arteries but not the left. Conclusion Nonpulsatile flow increases the mean pressure in all the vessels including cerebral vessels . Increasing pulsatility attenuates this effect. Anatomical variations in the circle of willis may increase the vulnerability to strokes. Identifying these factors may help in lowering the risk of of strokes and diminition of cognitive function in long term LVAD therapy.

Head Biometry in Fetuses with Isolated Congenital Heart Disease.

Altered cerebral hemodynamics are involved in changes in head biometry in fetuses with congenital heart disease (CHD). We compared head growth in different CHD groups with published normative values and investigated whether CHD groups differ from each other in terms of head circumference (HC) development over gestational age (GA). Retrospective cohort study consisting of 248 CHD fetuses. Subgroups were generated according to the expected ascending aorta oxygen saturation: Low placental blood content (BC) and therefore low oxygen delivery to the brain (group 1: n = 108), intermediate placental and systemic BC due to intracardiac mixing of blood (group 2: n = 103), high placental BC (group 3: n = 13) and low placental BC and low oxygen delivery to the brain without mixing of blood (group 4: n = 24). Furthermore, group 1 was divided into antegrade (n = 34) and retrograde (n = 74) flow through the aortic arch. Comparisons were made at a GA of 22, 30 and 38 weeks. Estimated values of zHC (z-score transformed) were not significantly different between the four CHD groups at the three time points in gestation (all p > 0.05). Within group 1 fetuses with retrograde aortic arch flow showed a significant negative association between HC and GA compared to reference values (b = -0.054, p < 0.001) and had significantly lower zHC values at 38 weeks (-0.836) compared to fetuses with antegrade flow (0.366, p = 0.009). Our data do not confirm that CHD fetuses in general have a significantly smaller HC. HC becomes smaller throughout gestation depending on the direction of aortic arch flow.

Early hemodynamic changes after fetal aortic stenosis valvuloplasty predict biventricular circulation at birth.

To describe the early hemodynamic changes after fetal aortic valvuloplasty (FAV) for evolving hypoplastic left heart syndrome due to mid-gestational aortic stenosis and to assess whether these early changes predict biventricular (BiV) circulation at neonatal discharge. We retrospectively reviewed all technically successful FAV cases resulting in live birth between 2000 and 2015 (n=93, 45% BiV circulation at neonatal discharge). Paired testing methods were used to compare pre-intervention and post-intervention measures of left ventricular hemodynamics. Logistic regression was used to determine whether these changes were predictive of post-natal outcome. Measures of left heart physiology were markedly abnormal pre-FAV and improved significantly post-FAV. No subjects had systolic antegrade transverse aortic arch flow pre-FAV and 65% of subjects had antegrade flow post-FAV. The number of subjects with abnormal left-to-right patent foramen ovale flow decreased, and the number with biphasic mitral valve inflow increased. The median left ventricular ejection fraction improved after intervention. Amongst the pre-post changes, gaining partially or exclusively antegrade systolic arch flow was the most significant independent predictor of BiV circulation (OR 9.80 and 19.83, respectively, both P<0.001). Technically successful FAV is associated with immediate improvements in left heart physiology that are predictive of BiV circulation at neonatal discharge.

P1424Differences in aortic arch flow dynamics in bicuspid aortic valve based on cusp fusion phenotypes

P1424Differences in aortic arch flow dynamics in bicuspid aortic valve based on cusp fusion phenotypes

Fetal Right Ventricular Prominence: Associated Postnatal Abnormalities and Coarctation Clinical Prediction Tool.

Fetal right ventricular (RV) prominence is a known indicator of possible left-sided structural heart disease with a low positive predictive value for aortic coarctation. There is a paucity of data on identifying which fetuses with RV prominence will have postnatal arch obstruction. Our study objectives were to create a clinical prediction tool for coarctation and to describe the diagnostic outcomes of our cohort with fetal RV prominence. We performed a retrospective review of patients referred with fetal RV prominence from January 2009 to October 2015. Recorded fetal echocardiographic variables included gestational age, semilunar and atrioventricular valve dimensions, left and right ventricular mid-cavitary dimensions, foramen ovale and aortic arch flow direction, and isthmal diameter. Postnatal cardiac and non-cardiac diagnoses were documented. We performed descriptive analysis for postnatal outcomes and classification tree analysis to create a clinical prediction tool. Eighty-eight patients were reviewed; 58 (66%) had abnormal postnatal echocardiograms, 45 (51%) had left-sided lesions, including 26 (30%) with coarctation, and 6 (7%) had pulmonary hypertension. Our clinical prediction tool employs gestational age, RV mid-cavitary dimension z-score, and isthmal diameter z-score to predict coarctation with 85% accuracy, 95% confidence interval [75.3, 92.4%]. Our model correctly classified 45/54 non-coarctation and 19/21 coarctation cases, with 90% sensitivity and 83% specificity. Developing an accurate prediction tool for coarctation in cases of fetal RV prominence is an important first step in improving our management of these challenging cases.

Head growth in fetuses with isolated congenital heart defects: lack of influence of aortic arch flow and ascending aorta oxygen saturation

Congenital heart defects (CHDs) are reported to be associated with a smaller fetal head circumference (HC) and neurodevelopmental delay. Recent studies suggest that altered intrauterine brain hemodynamics may explain these findings. Our objectives were to evaluate the pattern of head growth in a large cohort of fetuses with various types of CHD, analyze these patterns according to the type of CHD and estimate the effect of cerebral hemodynamics with advancing gestation in the second and third trimesters. Singleton fetuses with an isolated CHD were selected from three fetal medicine units (n = 436). Cases with placental insufficiency or genetic syndromes were excluded. CHD types were clustered according to the flow and oxygen saturation in the aorta. Z-scores of biometric data were constructed using growth charts of a normal population. HC at different gestational ages was evaluated and univariate and multivariate mixed regression analyses were performed to examine the patterns of prenatal HC growth. Fetuses with severe and less severe types of CHD demonstrated statistically significant HC growth restriction with increasing gestational age (slope of -0.017/day); however, there was no statistically significant effect of fetal hemodynamics on HC growth. Fetuses with CHD but normal brain oxygenation and normal aortic flow showed a significant decrease in HC growth (slope of -0.024/day). Only fetuses with isolated tetralogy of Fallot demonstrated a smaller HC z-score at 20 weeks of gestation (-0.67 (95% CI, -1.16 to -0.18)). Despite the decline in head growth in fetuses with a prenatally detected isolated CHD, HC values were within the normal range, raising the question of its clinical significance. Furthermore, in contrast to other studies, this large cohort did not establish a significant correlation between aortic flow or oxygen saturation and HC growth. Factors other than altered fetal cerebral hemodynamics may contribute to HC growth restriction with increasing gestational age, such as (epi)genetic or placental factors. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Abstract 18055: Induced Growth of Hypoplastic Cardiac Structures to Facilitate Repair of Congenital Defects

Introduction: Congenital heart defects (CHD) may include hypoplastic valves, ventricles and vessels which complicate repairs. Our hypotheses were that hypoplastic structures are developmental rather than primarily genetic in origin and the correct biomechanical signal would induce catch up growth. Our corollary hypothesis was that the growth signal is provided by flow, not pressure. First stage operations, therefore, were designed to increase flow and induce growth. Once growth was sufficient, a second operation would often complete the repair. We report our results using flow induced growth of hypoplastic structures to facilitate repair in 3 types of CHD. Methods: Three groups of CHD patients with associated hypoplastic structures: unbalanced atrioventricular canal defects (UAVC); pulmonary atresia with intact ventricular septum (PAIVS); and coarctation of the aorta (CoA) were reviewed. Operations increased flow through the hypoplastic structures, such as creating restrictive septal defects to increase flow through the hypoplastic AV valves and ventricles (UAVC, PAIVS) or relieving obstruction (CoA) to enhance aortic valve and arch flow. Results: On follow up, virtually all (85/90) hypoplastic structures reached normal size and the rest had nearly comparable growth (Table). Conclusions: 1) Operations designed to increase flow through hypoplastic structures reliably induced catch up growth of UAVC, PAIVS and CoA lesions. 2) The growth response supported underdevelopment as the cause of hypoplasia and flow as the growth signal to reverse it. 3) Growth induction allowed two ventricle repairs in UAVC and PAIVS patients and avoided extended arch repairs in CoA; all with decreased operative risk. 4) Following catch up growth of the hypoplastic lesions, the outlook improved to that of patients with balanced AVCs, normal sized RVs in pulmonary atresia and well repaired CoA. 5) Once normal size was reached growth continued, producing a durable result.

Comparison Between Bench-Top and Computational Modelling of Cerebral Thromboembolism in Ventricular Assist Device Circulation

Despite improvements in ventricular assist devices (VAD) design, VAD-induced stroke rates remain remarkably high at 14-47%. We previously employed computational fluid dynamics (CFD) to propose adjustment of VAD outflow graft (VAD-OG) implantation to reduce stoke. Herein, we present an in-vitro model of cerebral vessel embolization in VAD-assisted circulation, and compare benchtop results to CFD predictions. The benchtop flow-loop consists of a 3D printed aortic bed using Accura 60 polymer driven by a continuous-flow pump. Three hundred spherical particles simulating thrombi of 2, 3.5, and 5 mm diameters were injected at the mock VAD-OG inlet. A water and glycerin mixture (3.8 cP viscosity) synthetically mimicked blood. The flowrate was adjusted to match the CFD Reynolds number. Catch cans were used to capture and count particles reaching cerebral vessels. VAD-OG geometries were evaluated using comparison of means Z-score range of -1.96 ≤ Z ≤ 1.96 to demonstrate overall agreement between computational and in-vitro techniques. Z-scores were: (i) Z = -1.05 for perpendicular (0°), (ii) Z = 0.32 for intermediate (30°), and (iii) Z = -0.52 for shallow (60°) anastomosis and confirmed agreement for all geometries. This study confirmed added benefits of using a left carotid artery bypass-graft with percent embolization reduction: 22.6% for perpendicular, 21.2% for intermediate, and 11.9% for shallow anastomoses. The shallow anastomosis demonstrated lower degrees of aortic arch flow recirculation, consistent with steady-flow computations. Quantitatively and qualitatively, contemporary steady-flow computational models for predicting VAD-induced cerebral embolization can be achieved in-vitro to validate the CFD equivalent.

Severe left heart obstruction with retrograde arch flow influences fetal cerebral and placental blood flow

Decreased middle cerebral artery (MCA) pulsatility index (PI) is a marker of fetal brain-sparing in placental insufficiency and it is also found in fetuses with severe congenital heart disease. This study sought to explore the impact of anatomical subtypes in fetal heart disease on MCA-PI and head growth. We retrospectively reviewed fetal echocardiograms of pregnancies complicated by fetal hypoplastic left heart syndrome (HLHS; n = 42) with and without anatomic coarctation (n = 28 and n = 10, respectively), isolated severe aortic coarctation (n = 21), D-transposition of the great arteries (TGA; n = 11) and pulmonary outflow tract obstruction without forward flow across the pulmonary valve (POTO; n = 15), comparing observations with gestational age-matched controls (n = 89). No fetus had major extracardiac pathology or aneuploidy. MCA and umbilical artery (UA) PI, the cerebral placental ratio (CPR = MCA-PI/ UA-PI) and neonatal head circumference were obtained and expressed as Z-scores. Lower MCA-PI, higher UA-PI and lower CPR were observed in fetal HLHS and isolated coarctation with reversed arch flow (n = 6) (P < 0.001) but not TGA, POTO or isolated coarctation with antegrade arch flow (n = 15) compared with controls. No difference was found between HLHS with anatomical coarctation and those without; however, MCA-PI correlated positively with neonatal head circumference in HLHS with reversed distal arch flow (r = 0.33, P < 0.05). Severe left heart obstruction with reversed aortic arch flow is associated with altered fetal cerebral blood flow, and in these conditions, MCA-PI positively correlates with head growth. Anatomical arch obstruction itself may not be a contributing factor to altered MCA flow in fetal HLHS.