Image-based modeling of hemodynamics in coronary artery aneurysms caused by Kawasaki disease

SeqSeg: Learning Local Segments for Automatic Vascular Model Construction

Computational modeling of cardiovascular function has become a critical part of diagnosing, treating and understanding cardiovascular disease. Most strategies involve constructing anatomically accurate computer models of cardiovascular structures, which is a multistep, time-consuming process. To improve the model generation process, we herein present SeqSeg (sequential segmentation): a novel deep learning-based automatic tracing and segmentation algorithm for constructing image-based vascular models. SeqSeg leverages local U-Net-based inference to sequentially segment vascular structures from medical image volumes. We tested SeqSeg on CT and MR images of aortic and aortofemoral models and compared the predictions to those of benchmark 2D and 3D global nnU-Net models, which have previously shown excellent accuracy for medical image segmentation. We demonstrate that SeqSeg is able to segment more complete vasculature and is able to generalize to vascular structures not annotated in the training data.

Hemodynamic influence of mild stenosis morphology in different coronary arteries: a computational fluid dynamic modelling study

Introduction: Mild stenosis [degree of stenosis (DS) < 50%] is commonly labeled as nonobstructive lesion. Some lesions remain stable for several years, while others precipitate acute coronary syndromes (ACS) rapidly. The causes of ACS and the factors leading to diverse clinical outcomes remain unclear. Method: This study aimed to investigate the hemodynamic influence of mild stenosis morphologies in different coronary arteries. The stenoses were modeled with different morphologies based on a healthy individual data. Computational fluid dynamics analysis was used to obtain hemodynamic characteristics, including flow waveforms, fractional flow reserve (FFR), flow streamlines, time-average wall shear stress (TAWSS), and oscillatory shear index (OSI). Results: Numerical simulation indicated significant hemodynamic differences among different DS and locations. In the 20%-30% range, significant large, low-velocity vortexes resulted in low TAWSS (<4 dyne/cm2) around stenoses. In the 30%-50% range, high flow velocity due to lumen area reduction resulted in high TAWSS (>40 dyne/cm2), rapidly expanding the high TAWSS area (averagely increased by 0.46 cm2) in left main artery and left anterior descending artery (LAD), where high OSI areas remained extensive (>0.19 cm2). Discussion: While mild stenosis does not pose any immediate ischemic risk due to a FFR > 0.95, 20%-50% stenosis requires attention and further subdivision based on location is essential. Rapid progression is a danger for lesions with 20%-30% DS near the stenoses and in the proximal LAD, while lesions with 30%-50% DS can cause plaque injury and rupture. These findings support clinical practice in early assessment, monitoring, and preventive treatment.

Myocardial perfusion impairment in children with Kawasaki disease: assessment with cardiac magnetic resonance first-pass perfusion

Background

Kawasaki disease (KD) potentially increases the risk of myocardial ischemia. This study aimed to semi-quantitatively evaluate myocardial perfusion impairment using cardiac magnetic resonance (CMR) first-pass perfusion in children with KD and explore the association between coronary artery (CA) dilation and myocardial perfusion.

Methods

From December 2018 to July 2021, 77 patients with KD (48 male, 5.71±2.80 years) and 37 age- and sex-matched normal controls (20 male, 6.19±3.32 years) who underwent CMR in West China Second University Hospital were enrolled in this cross-sectional study with prospective data collection. A total of 30 of these patients completed the follow-up CMR, with a median interval of 13 months. Myocardial perfusion parameters including perfusion index (PI) and maximum signal intensity (Max SI) were obtained through rest first-pass perfusion. The internal diameter of the CA was assessed via coronary magnetic resonance angiography (CMRA) to calculate the coronary Z score. The global and regional myocardial parameters among the subgroups were compared. Statistical analysis included one-way analysis of variance (ANOVA), Pearson's correlation, and multivariate linear regression.

Results

The global Max SI and regional Max SI of all segments in patients with and without CA dilation decreased compared with those in controls (P=0.19 and P<0.001, respectively). The global PI of patients with CA dilation and regional PI in segments subtended by dilated CA were lower than that of controls (P=0.002 and P<0.001, respectively) and were negatively correlated with the Z score (global: r=-0.576; regional: r=-0.351, both P<0.001). Multivariate analysis revealed that the Z score was negatively associated with global PI in KD (β=-0.409, P=0.02, model R2=0.170). The global Max SI of patients with and without CA dilation during the follow-up CMR decreased compared with that of the first CMR (42.18±9.84 vs. 34.48±8.24, P=0.02; 44.82±7.13 vs. 36.61±7.67, P=0.03, respectively).

Conclusions

CMR myocardial first-pass perfusion imaging can semi-quantitatively evaluate impaired myocardial perfusion in KD patients. Not only patients with CA dilation and segments subtended by dilated CA but also those without CA dilation and segments subtended by non-dilated CA developed myocardial perfusion impairment, the severity of myocardial perfusion impairment is associated with the degree of CA dilation.

Impact of minimal lumen segmentation uncertainty on patient-specific coronary simulations: A look at FFRCT

We examined the effect of minimal lumen segmentation uncertainty on Fractional Flow Reserve obtained from Coronary Computed Tomography AngiographyFFR CT . A total of 14 patient-specific coronary models with different stenosis locations and degrees of severity were enrolled in this study. The optimal segmented coronary lumens were disturbed using intra± 6 % and inter-operator± 15 % variations on the segmentation threshold.FFR CT was evaluated in each case by 3D-OD CFD simulations. The findings suggest that the sensitivity ofFFR CT to this type of uncertainty increases distally and with the stenosis severity. Cases with moderate or severe distal coronary lesions should undergo either exact and thorough segmentation operations or invasive FFR measurements, particularly if theFFR CT is close to the cutoff (0.80). Therefore, we conclude that it is crucial to consider the lesion's location and degree of severity when evaluatingFFR CT results.

Review of cardiac-coronary interaction and insights from mathematical modeling

Cardiac-coronary interaction is fundamental to the function of the heart. As one of the highest metabolic organs in the body, the cardiac oxygen demand is met by blood perfusion through the coronary vasculature. The coronary vasculature is largely embedded within the myocardial tissue which is continually contracting and hence squeezing the blood vessels. The myocardium-coronary vessel interaction is two-ways and complex. Here, we review the different types of cardiac-coronary interactions with a focus on insights gained from mathematical models. Specifically, we will consider the following: (1) myocardial-vessel mechanical interaction; (2) metabolic-flow interaction and regulation; (3) perfusion-contraction matching, and (4) chronic interactions between the myocardium and coronary vasculature. We also provide a discussion of the relevant experimental and clinical studies of different types of cardiac-coronary interactions. Finally, we highlight knowledge gaps, key challenges, and limitations of existing mathematical models along with future research directions to understand the unique myocardium-coronary coupling in the heart. This article is categorized under: Cardiovascular Diseases > Computational Models Cardiovascular Diseases > Biomedical Engineering Cardiovascular Diseases > Molecular and Cellular Physiology.

A Computational Model of Ventricular Dimensions and Hemodynamics in Growing Infants

Previous computer models have successfully predicted cardiac growth and remodeling in adults with pathologies. However, applying these models to infants is complicated by the fact that they also undergo normal, somatic cardiac growth and remodeling. Therefore, we designed a computational model to predict ventricular dimensions and hemodynamics in healthy, growing infants by modifying an adult canine left ventricular growth model. The heart chambers were modeled as time-varying elastances coupled to a circuit model of the circulation. Circulation parameters were allometrically scaled and adjusted for maturation to simulate birth through 3 yrs of age. Ventricular growth was driven by perturbations in myocyte strain. The model successfully matched clinical measurements of pressures, ventricular and atrial volumes, and ventricular thicknesses within two standard deviations of multiple infant studies. To test the model, we input 10th and 90th percentile infant weights. Predicted volumes and thicknesses decreased and increased within normal ranges and pressures were unchanged. When we simulated coarctation of the aorta, systemic blood pressure, left ventricular thickness, and left ventricular volume all increased, following trends in clinical data. Our model enables a greater understanding of somatic and pathological growth in infants with congenital heart defects. Its flexibility and computational efficiency when compared to models employing more complex geometries allow for rapid analysis of pathological mechanisms affecting cardiac growth and hemodynamics.

Predictors of Myocardial Ischemia in Patients with Kawasaki Disease: Insights from Patient-Specific Simulations of Coronary Hemodynamics

Current treatments for patients with coronary aneurysms caused by Kawasaki disease (KD) are based primarily on aneurysm size. This ignores hemodynamic factors influencing myocardial ischemic risk. We performed patient-specific computational hemodynamics simulations for 15 KD patients, with parameters tuned to patients' arterial pressure and cardiac function. Ischemic risk was evaluated in 153 coronary arteries from simulated fractional flow reserve (FFR), wall shear stress, and residence time. FFR correlated weakly with aneurysm [Formula: see text]-scores (correlation coefficient, [Formula: see text]) but correlated better with the ratio of maximum-to-minimum aneurysmal lumen diameter ([Formula: see text]). FFR dropped more rapidly distal to aneurysms, and this correlated more with the lumen diameter ratio ([Formula: see text]) than [Formula: see text]-score ([Formula: see text]). Wall shear stress correlated better with the diameter ratio ([Formula: see text]), while residence time correlated more with [Formula: see text]-score ([Formula: see text]). Overall, the maximum-to-minimum diameter ratio predicted ischemic risk better than [Formula: see text]-score. Although FFR immediately distal to aneurysms was nonsignificant, its rapid rate of decrease suggests elevated risk.

Improved characterization of lenticulostriate arteries using compressed sensing time-of-flight at 7T

OBJECTIVES

To evaluate the feasibility of 0.2-mm isotropic lenticulostriate arteries (LSAs) imaging using compressed sensing time-of-flight (CS TOF) at around 10 min on 7T, and compare the delineation and characterization of LSAs using conventional TOF and CS TOF.

METHODS

Thirty healthy volunteers were examined with CS TOF and conventional TOF at 7T for around 10 min each. CS TOF was optimized to achieve 0.2-mm isotropic LSA imaging. The numbers of LSA stems and branches were counted and compared on a vascular skeleton. The length and distance were measured and compared on the most prominent branch in each hemisphere. Another patient with intracranial artery stenosis was studied to compare LSA delineation in CS TOF and digital subtraction angiography (DSA).

RESULTS

The number of stems visualized with CS TOF was significantly higher than with conventional TOF in both left (p = 0.002, ICC = 0.884) and right (p < 0.001, ICC = 0.938) hemispheres. The number of branches visualized by conventional TOF was significantly lower than that by CS TOF in both left (p < 0.001, ICC = 0.893) and right (p < 0.001, ICC = 0.896) hemispheres. The lengths were statistically higher in CS TOF than in conventional TOF (left: p < 0.001, ICC = 0.868; right: p < 0.001, ICC = 0.876).

CONCLUSIONS

The high-resolution CS TOF improves the delineation and characterization of LSAs over conventional TOF. High-resolution LSA imaging using CS TOF can be a promising tool for clinical research and applications in patients with neurologic diseases.

KEY POINTS

• 0.2-mm isotropic LSA imaging for around 10 min using CS TOF at 7T is feasible. • More stems and branches of LSAs with longer lengths can be delineated with CS TOF than with conventional TOF at the same scan time. • High-resolution CS TOF can be a promising tool for research and applications on LSA.

A comprehensive mathematical model for cardiac perfusion

The aim of this paper is to introduce a new mathematical model that simulates myocardial blood perfusion that accounts for multiscale and multiphysics features. Our model incorporates cardiac electrophysiology, active and passive mechanics, hemodynamics, valve modeling, and a multicompartment Darcy model of perfusion. We consider a fully coupled electromechanical model of the left heart that provides input for a fully coupled Navier-Stokes-Darcy Model for myocardial perfusion. The fluid dynamics problem is modeled in a left heart geometry that includes large epicardial coronaries, while the multicompartment Darcy model is set in a biventricular myocardium. Using a realistic and detailed cardiac geometry, our simulations demonstrate the biophysical fidelity of our model in describing cardiac perfusion. Specifically, we successfully validate the model reliability by comparing in-silico coronary flow rates and average myocardial blood flow with clinically established values ranges reported in relevant literature. Additionally, we investigate the impact of a regurgitant aortic valve on myocardial perfusion, and our results indicate a reduction in myocardial perfusion due to blood flow taken away by the left ventricle during diastole. To the best of our knowledge, our work represents the first instance where electromechanics, hemodynamics, and perfusion are integrated into a single computational framework.

Effect of Beta Blockers on the Hemodynamics and Thrombotic Risk of Coronary Artery Aneurysms in Kawasaki Disease

This study aims to simulate beta blockers' (BB) effects on coronary artery aneurysms' (CAA) hemodynamics and thrombotic risk in Kawasaki disease (KD). BB are recommended in cases of large aneurysms due to their anti-ischemic effect. Coronary blood flow (CBF) was simulated in KD patient-specific CAA models using computational fluid dynamics. Hemodynamic indices that correlate with thrombotic risk were calculated following two possible responses to BB: (1) preserved coronary flow (third BB generation) and (2) reduction in coronary flow (first and second BB generations) at reduced heart rate. Following CBF reduction scenario, mean TAWSS and HOLMES significantly decreased compared to normal conditions, leading to a potential increase in thrombotic risk. Preserved CBF at lower heart rates, mimicking the response to vasodilating BBs, does not significantly affect local CAA hemodynamics compared with baseline, while achieving the desired anti-ischemic effects. Different BB generations lead to different hemodynamic responses in CAA.

Recasting Current Knowledge of Human Fetal Circulation: The Importance of Computational Models

Computational hemodynamic simulations are becoming increasingly important for cardiovascular research and clinical practice, yet incorporating numerical simulations of human fetal circulation is relatively underutilized and underdeveloped. The fetus possesses unique vascular shunts to appropriately distribute oxygen and nutrients acquired from the placenta, adding complexity and adaptability to blood flow patterns within the fetal vascular network. Perturbations to fetal circulation compromise fetal growth and trigger the abnormal cardiovascular remodeling that underlies congenital heart defects. Computational modeling can be used to elucidate complex blood flow patterns in the fetal circulatory system for normal versus abnormal development. We present an overview of fetal cardiovascular physiology and its evolution from being investigated with invasive experiments and primitive imaging techniques to advanced imaging (4D MRI and ultrasound) and computational modeling. We introduce the theoretical backgrounds of both lumped-parameter networks and three-dimensional computational fluid dynamic simulations of the cardiovascular system. We subsequently summarize existing modeling studies of human fetal circulation along with their limitations and challenges. Finally, we highlight opportunities for improved fetal circulation models.

In-Silico and In-Vitro Analysis of the Novel Hybrid Comprehensive Stage II Operation for Single Ventricle Circulation

Single ventricle (SV) anomalies account for one-fourth of all congenital heart disease cases. The existing palliative treatment for this anomaly achieves a survival rate of only 50%. To reduce the trauma associated with surgical management, the hybrid comprehensive stage II (HCSII) operation was designed as an alternative for a select subset of SV patients with the adequate antegrade aortic flow. This study aims to provide better insight into the hemodynamics of HCSII patients utilizing a multiscale Computational Fluid Dynamics (CFD) model and a mock flow loop (MFL). Both 3D-0D loosely coupled CFD and MFL models have been tuned to match baseline hemodynamic parameters obtained from patient-specific catheterization data. The hemodynamic findings from clinical data closely match the in-vitro and in-silico measurements and show a strong correlation (r = 0.9). The geometrical modification applied to the models had little effect on the oxygen delivery. Similarly, the particle residence time study reveals that particles injected in the main pulmonary artery (MPA) have successfully ejected within one cardiac cycle, and no pathological flows were observed.

Automated generation of 0D and 1D reduced-order models of patient-specific blood flow

Three-dimensional (3D) cardiovascular fluid dynamics simulations typically require hours to days of computing time on a high-performance computing cluster. One-dimensional (1D) and lumped-parameter zero-dimensional (0D) models show great promise for accurately predicting blood bulk flow and pressure waveforms with only a fraction of the cost. They can also accelerate uncertainty quantification, optimization, and design parameterization studies. Despite several prior studies generating 1D and 0D models and comparing them to 3D solutions, these were typically limited to either 1D or 0D and a singular category of vascular anatomies. This work proposes a fully automated and openly available framework to generate and simulate 1D and 0D models from 3D patient-specific geometries, automatically detecting vessel junctions and stenosis segments. Our only input is the 3D geometry; we do not use any prior knowledge from 3D simulations. All computational tools presented in this work are implemented in the open-source software platform SimVascular. We demonstrate the reduced-order approximation quality against rigid-wall 3D solutions in a comprehensive comparison with N = 72 publicly available models from various anatomies, vessel types, and disease conditions. Relative average approximation errors of flows and pressures typically ranged from 1% to 10% for both 1D and 0D models, measured at the outlets of terminal vessel branches. In general, 0D model errors were only slightly higher than 1D model errors despite requiring only a third of the 1D runtime. Automatically generated ROMs can significantly speed up model development and shift the computational load from high-performance machines to personal computers.

Predicting hemodynamic indices in coronary artery aneurysms using response surface method: An application in Kawasaki disease

BACKGROUND AND OBJECTIVES

Coronary artery aneurysms (CAA), such as those in Kawasaki Disease (KD), induce hemodynamic alterations associated with thrombosis and atherosclerosis. Current clinical routines assess the risk level of the CAA cases based on the Z-Score, which considers the body surface area (BSA) and the CAA's diameter. A full geometric characterization and impact on hemodynamic metrics and their correlation with thrombotic risks have not been systematically investigated. The goal of this study was to investigate the effect of CAA shape indices on local hemodynamics using the response surface method (RSM) through considering KD applications.

METHODS

Transient computational fluid dynamics (CFD) simulations have been performed on idealized CAA geometries defined by geometrical ratios combining neck diameter, CAA diameter and CAA length. The results were used to develop full quadratic regression models of the indices using the response surface method (RSM). Validation using patient-specific KD models was performed.

RESULTS

The results indicated that the aneurysm diameter is the main determining factor in the thrombotic risk of CAA patients, which is consistent with clinical guidelines. Furthermore, it was observed that in most CAA cases having the same diameter, the one with the shorter length experiences higher RRT values, indicating flow stagnation and circulation.

CONCLUSIONS

The developed regression models can be used to ultimately assess the thrombotic risk of CAA cases from the hemodynamic perspective. The applicability of these models was tested on 2 KD patient specific models, with close values achieved between the models and the patient-specific results.

Fractional Flow Reserve (FFR) Estimation from OCT-Based CFD Simulations: Role of Side Branches

The computational fluid dynamic method has been widely used to quantify the hemodynamic alterations in a diseased artery and investigate surgery outcomes. The artery model reconstructed based on optical coherence tomography (OCT) images generally does not include the side branches. However, the side branches may significantly affect the hemodynamic assessment in a clinical setting, i.e., the fractional flow reserve (FFR), defined as the ratio of mean distal coronary pressure to mean aortic pressure. In this work, the effect of the side branches on FFR estimation was inspected with both idealized and optical coherence tomography (OCT)-reconstructed coronary artery models. The electrical analogy of blood flow was further used to understand the impact of the side branches (diameter and location) on FFR estimation. Results have shown that the side branches decrease the total resistance of the vessel tree, resulting in a higher inlet flowrate. The side branches located at the downstream of the stenosis led to a lower FFR value, while the ones at the upstream had a minimal impact on the FFR estimation. Side branches with a diameter larger than one third of the main vessel diameter are suggested to be considered for a proper FFR estimation. The findings in this study could be extended to other coronary artery imaging modalities and facilitate treatment planning.

A Hemodynamic Analysis of the Thrombosis Within Occluded Coronary Arterial Fistulas With Terminal Aneurysms Using a Blood Stasis Model

Objective: The aim of this study is to numerically evaluate thrombosis risk within occluded coronary arterial fistulas (CAF) with terminal aneurysms, and provide guidance in choosing occlusion positions, with clinical observations as reference. Method: Four patients with CAF were studied, with different occlusion positions in actual treatments. Hemodynamics simulations were conducted, with blood residue predicted using the blood stasis model. Three types of models (untreated model, aneurysm-reserved model and aneurysm-removed model) were studeid for each patient. Four metrics, i.e., proportion of high oscillatory shear index (OSI), area of high OSI, old blood volume fraction (OBVF)) and old blood volume (OBV) was obtained to distinguish the thrombosis risk of different treatments (proximal or distal occlusion), comparing with the follow-up CTA. Results: For all the postopertive models, the high OBVF, high OSI(>0.3) and low time-averaged wall shear stress (TAWSS) regions were mainly at the distal fistula, indicating these regions were prone to thrombosis. The regions where blood residue remains are roughly regions of high OSI, corresponding well with clinical observations. In contrast, TAWSS failed to distinguish the difference in thrombosis risk. Absolute values (area of high OSI, OBV) can better reflect the degree of thrombosis risk between treatment types compared with percentage values (proportion of high OSI, OBVF). By comparing with the actual clinical treatments and observations, the OBV is superior to the area of high OSI in determining treatment type. Conclusion: The OBV, a volumetric parameter for blood stasis, can better account for the CAF thrombosis and reflect the degree of blood stasis compared with OSI or TAWSS, is a more appropriate metric for thrombosis in the fistula. Together with morphological parameters, the OBV could guide clinicians to formulate more appropriate surgical plans, which is of great significance for the preoperative evaluation and treatment prognosis of CAF patients.

Imaging the delayed complications of childhood Kawasaki disease

This review will discuss the long-term complications of Kawasaki disease with a particular focus on imaging surveillance of the coronary arteries in adolescence and adult life. The relative advantages and disadvantages of each modality will be illustrated with practical examples, demonstrating that, in many cases, a multimodality imaging strategy may be required.

Practical Workflow for Cardiovascular Assessment and Follow-Up in Kawasaki Disease Based on Expert Opinion

BACKGROUND

Approximately 25% of the patients with a history of Kawasaki disease (KD) develop coronary artery pathology if left untreated, with coronary artery aneurysms (CAA) as an early hallmark. Depending on the severity of CAAs, these patients are at risk of myocardial ischemia, infarction and sudden death. In order to reduce cardiac complications it is crucial to accurately identify patients with coronary artery pathology by an integrated cardiovascular program, tailored to the severity of the existing coronary artery pathology.

METHODS

The development of this practical workflow for the cardiovascular assessment of KD patients involve expert opinions of pediatric cardiologists, infectious disease specialists and radiology experts with clinical experience in a tertiary KD reference center of more than 1000 KD patients. Literature was analyzed and an overview of the currently most used guidelines is given.

CONCLUSIONS

We present a patient-specific step-by-step, integrated cardiovascular follow-up approach based on expert opinion of a multidisciplinary panel with expertise in KD.

Association of left ventricular systolic dysfunction with coronary artery dilation in Kawasaki disease patients: Assessment with cardiovascular magnetic resonance

PURPOSE

To quantify global and regional left ventricular (LV) strain parameters in patients with Kawasaki disease (KD) using cardiovascular magnetic resonance (CMR) tissue tracking and assess the association of coronary artery dilation (CA dilation) with LV systolic dysfunction.

METHODS

Thirty-one KD patients with CA dilation, 22 patients without CA dilation and 27 age- and sex-matched normal controls underwent 3.0 T CMR examination. Z score of >2 was defined as CA dilation. Global LV strain parameters and regional LV strain parameters in 16 American Heart Association segmentation, including radial, circumferential and longitudinal peak strain (PS) and LV function were measured and compared among groups.

RESULTS

No significant difference in LV ejection fraction has been observed among controls, KD patients with CA dilation and without CA dilation (all p > 0.05). However, global longitudinal PS (GLPS) was lower in groups with CA dilation than those without CA dilation (-12.6 ± 4.1% vs -14.9 ± 2.6%, p < 0.05). For regional strain parameters, the segments with CA dilation (n = 301) were lower than those in both normal controls (n = 416) and segments without CA dilation (n = 547) in regional radial, circumferential and longitudinal PS (all p < 0.05). The severity of CA dilation was positively correlated to GLPS and regional longitudinal PS (r = 0.388 and r = 0.222; both p < 0.05) in KD patients. After adjusting for clinical characteristics, the multivariate analysis demonstrated that Z score was independently associated with GLPS in KD patients (β = 0.469, p = 0.000, model R² = 0.355).

CONCLUSIONS

CMR tissue tracking could sensitively identify subclinical LV dysfunction in KD patients with CA dilation. LV systolic dysfunction occurs particularly in the myocardium dominated by the dilated coronary artery. CA dilation is an independent predictor of LV systolic dysfunction.

Prevalence and Long-term Outcomes of Patients with Coronary Artery Ectasia Presenting with Acute Myocardial Infarction

Coronary artery ectasia (CAE) is described in 5% of patients undergoing coronary angiography. Previous studies have shown controversial results regarding the prognostic impact of CAE. The prevalence and prognostic value of CAE in patients with acute myocardial infarction (AMI) remain unknown. In 4788 patients presenting with AMI referred for coronary angiography the presence of CAE (defined as dilation of a coronary segment with a diameter ≥1.5 times of the adjacent normal segment) was confirmed in 174 (3.6%) patients (age 62 ± 12 years; 81% male), and was present in the culprit vessel in 79.9%. Multivessel CAE was frequent (67%). CAE patients were more frequently male, had high thrombus burden and were treated more often with thrombectomy and less often was stent implantation. Markis I was the most frequent angiographic phenotype (43%). During a median follow-up of 4 years (1-7), 1243 patients (26%) experienced a major adverse cardiovascular event (MACE): 282 (6%) died from a cardiac cause, 358 (8%) had a myocardial infarction, 945 (20%) underwent coronary revascularization and 58 (1%) presented with a stroke. Patients with CAE showed higher rates of MACE as compared to those without CAE (36.8% versus 25.6%; p <0.001). On multivariable analysis, CAE was associated with MACE (HR 1.597; 95% CI 1.238-2.060; p <0.001) after adjusting for risk factors, type of AMI and number of narrowed coronary arteries. In conclusion, the prevalence of CAE in patients presenting with AMI is relatively low but was independently associated with an increased risk of MACE at follow-up.

Computational modeling of blood component transport related to coronary artery thrombosis in Kawasaki disease

Coronary artery thrombosis is the major risk associated with Kawasaki disease (KD). Long-term management of KD patients with persistent aneurysms requires a thrombotic risk assessment and clinical decisions regarding the administration of anticoagulation therapy. Computational fluid dynamics has demonstrated that abnormal KD coronary artery hemodynamics can be associated with thrombosis. However, the underlying mechanisms of clot formation are not yet fully understood. Here we present a new model incorporating data from patient-specific simulated velocity fields to track platelet activation and accumulation. We use a system of Reaction-Advection-Diffusion equations solved with a stabilized finite element method to describe the evolution of non-activated platelets and activated platelet concentrations [AP], local concentrations of adenosine diphosphate (ADP) and poly-phosphate (PolyP). The activation of platelets is modeled as a function of shear-rate exposure and local concentration of agonists. We compared the distribution of activated platelets in a healthy coronary case and six cases with coronary artery aneurysms caused by KD, including three with confirmed thrombosis. Results show spatial correlation between regions of higher concentration of activated platelets and the reported location of the clot, suggesting predictive capabilities of this model towards identifying regions at high risk for thrombosis. Also, the concentration levels of ADP and PolyP in cases with confirmed thrombosis are higher than the reported critical values associated with platelet aggregation (ADP) and activation of the intrinsic coagulation pathway (PolyP). These findings suggest the potential initiation of a coagulation pathway even in the absence of an extrinsic factor. Finally, computational simulations show that in regions of flow stagnation, biochemical activation, as a result of local agonist concentration, is dominant. Identifying the leading factors to a pro-coagulant environment in each case—mechanical or biochemical—could help define improved strategies for thrombosis prevention tailored for each patient.

Computational studies aiming to model thrombosis often rely on an arterial wall injury. Collagen and other extracellular matrix components are exposed to the bloodstream, which facilitates platelet adhesion to the wall and subsequent clot formation. However, these models are not adequate to explain thrombosis in other settings where even in the absence of a focal lesion, clots may still form under certain flow conditions. Coronary artery aneurysm thrombosis following KD is an example of the need to understand the mechanisms of thrombus initiation in the absence of an extrinsic factor. This study provides a new framework to investigate thrombus initiation in KD from a patient-specific perspective, which integrates fluid mechanics and biochemistry and which could help quantify the pro-coagulant environment induced by the aneurysm and become a predictive tool. The work presented here has broad relevance to other clinical situations where flow stagnation and transport are driving factors in thrombus formation.

Hemodynamic Characteristics of Patients With Suspected Coronary Heart Disease at Their Initial Visit

Purpose

It is difficult for doctors to decide whether patients with suspected coronary heart disease classified as Coronary Artery Disease Reporting and Data System (CAD-RADS) < 3 should be administered preventive treatment, or whether non-atherosclerotic chest pain should be considered. The aim of the current study was to investigate coronary hemodynamic characteristics in such patients, which may provide more information on their stenosis and be helpful for initial diagnoses.

Methods

Two patient-specific models were reconstructed based on the coronary computed tomographic angiography underwent in 2012. Patient 1 was classified as CAD-RADS 0, and was readmitted to hospital due to coronary artery disease within 5 years. Patient 2 was classified as CAD-RADS 2, and has experienced no adverse events to date. Computational fluid dynamics (CFD) analysis was used to obtain hemodynamic parameters including flow rate waveform, flow streamlines, time-average wall shear stress (TAWSS), and oscillatory shear index (OSI).

Results

Patient 1 exhibited no physiological characteristics of right coronary artery flow waveform, large areas of low TAWSS, and slow blood flow in the proximal and middle segments of the left anterior descending branch. Patient 2 exhibited reduced coronary supply, small and separate areas of abnormal TAWSS, and a higher left anterior descending branch OSI than patient 1.

Conclusion

Hemodynamic abnormalities may play an important role in the prognosis of patients with coronary stenosis, and patient-specific hemodynamic characteristics may facilitate more accurate initial diagnosis, and better management. Overall hemodynamics (along the whole vessel) warranted attention at the time of the initial visit in patients classified as CAD-RADS < 3.

Coronary CT angiography-based estimation of myocardial perfusion territories for coronary artery FFR and wall shear stress simulation

This study aims to apply a CCTA-derived territory-based patient-specific estimation of boundary conditions for coronary artery fractional flow reserve (FFR) and wall shear stress (WSS) simulation. The non-invasive simulation can help diagnose the significance of coronary stenosis and the likelihood of myocardial ischemia. FFR is often regarded as the gold standard to evaluate the functional significance of stenosis in coronary arteries. In another aspect, proximal wall shear stress (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm{{WSS}_{prox}}$$\end{document}WSSprox) can also be an indicator of plaque vulnerability. During the simulation process, the mass flow rate of the blood in coronary arteries is one of the most important boundary conditions. This study utilized the myocardium territory to estimate and allocate the mass flow rate. 20 patients are included in this study. From the knowledge of anatomical information of coronary arteries and the myocardium, the territory-based FFR and the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm{{WSS}_{prox}}$$\end{document}WSSprox can both be derived from fluid dynamics simulations. Applying the threshold of distinguishing between significant and non-significant stenosis, the territory-based method can reach the accuracy, sensitivity, and specificity of 0.88, 0.90, and 0.80, respectively. For significantly stenotic cases (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm{FFR}_{m}$$\end{document}FFRm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\le$$\end{document}≤ 0.80), the vessels usually have higher wall shear stress in the proximal region of the lesion.

CRIMSON: An open-source software framework for cardiovascular integrated modelling and simulation

In this work, we describe the CRIMSON (CardiovasculaR Integrated Modelling and SimulatiON) software environment. CRIMSON provides a powerful, customizable and user-friendly system for performing three-dimensional and reduced-order computational haemodynamics studies via a pipeline which involves: 1) segmenting vascular structures from medical images; 2) constructing analytic arterial and venous geometric models; 3) performing finite element mesh generation; 4) designing, and 5) applying boundary conditions; 6) running incompressible Navier-Stokes simulations of blood flow with fluid-structure interaction capabilities; and 7) post-processing and visualizing the results, including velocity, pressure and wall shear stress fields. A key aim of CRIMSON is to create a software environment that makes powerful computational haemodynamics tools accessible to a wide audience, including clinicians and students, both within our research laboratories and throughout the community. The overall philosophy is to leverage best-in-class open source standards for medical image processing, parallel flow computation, geometric solid modelling, data assimilation, and mesh generation. It is actively used by researchers in Europe, North and South America, Asia, and Australia. It has been applied to numerous clinical problems; we illustrate applications of CRIMSON to real-world problems using examples ranging from pre-operative surgical planning to medical device design optimization.

Multimodal cardiovascular model for hemodynamic analysis: Simulation study on mitral valve disorders

Valvular heart diseases are a prevalent cause of cardiovascular morbidity and mortality worldwide, affecting a wide spectrum of the population. In-silico modeling of the cardiovascular system has recently gained recognition as a useful tool in cardiovascular research and clinical applications. Here, we present an in-silico cardiac computational model to analyze the effect and severity of valvular disease on general hemodynamic parameters. We propose a multimodal and multiscale cardiovascular model to simulate and understand the progression of valvular disease associated with the mitral valve. The developed model integrates cardiac electrophysiology with hemodynamic modeling, thus giving a broader and holistic understanding of the effect of disease progression on various parameters like ejection fraction, cardiac output, blood pressure, etc., to assess the severity of mitral valve disorders, naming Mitral Stenosis and Mitral Regurgitation. The model mimics an adult cardiovascular system, comprising a four-chambered heart with systemic, pulmonic circulation. The simulation of the model output comprises regulated pressure, volume, and flow for each heart chamber, valve dynamics, and Photoplethysmogram signal for normal physiological as well as pathological conditions due to mitral valve disorders. The generated physiological parameters are in agreement with published data. Additionally, we have related the simulated left atrium and ventricle dimensions, with the enlargement and hypertrophy in the cardiac chambers of patients with mitral valve disorders, using their Electrocardiogram available in Physionet PTBI dataset. The model also helps to create 'what if' scenarios and relevant analysis to study the effect in different hemodynamic parameters for stress or exercise like conditions.

Multilevel and multifidelity uncertainty quantification for cardiovascular hemodynamics

Standard approaches for uncertainty quantification in cardiovascular modeling pose challenges due to the large number of uncertain inputs and the significant computational cost of realistic three-dimensional simulations. We propose an efficient uncertainty quantification framework utilizing a multilevel multifidelity Monte Carlo (MLMF) estimator to improve the accuracy of hemodynamic quantities of interest while maintaining reasonable computational cost. This is achieved by leveraging three cardiovascular model fidelities, each with varying spatial resolution to rigorously quantify the variability in hemodynamic outputs. We employ two low-fidelity models (zero- and one-dimensional) to construct several different estimators. Our goal is to investigate and compare the efficiency of estimators built from combinations of these two low-fidelity model alternatives and our high-fidelity three-dimensional models. We demonstrate this framework on healthy and diseased models of aortic and coronary anatomy, including uncertainties in material property and boundary condition parameters. Our goal is to demonstrate that for this application it is possible to accelerate the convergence of the estimators by utilizing a MLMF paradigm. Therefore, we compare our approach to single fidelity Monte Carlo estimators and to a multilevel Monte Carlo approach based only on three-dimensional simulations, but leveraging multiple spatial resolutions. We demonstrate significant, on the order of 10 to 100 times, reduction in total computational cost with the MLMF estimators. We also examine the differing properties of the MLMF estimators in healthy versus diseased models, as well as global versus local quantities of interest. As expected, global quantities such as outlet pressure and flow show larger reductions than local quantities, such as those relating to wall shear stress, as the latter rely more heavily on the highest fidelity model evaluations. Similarly, healthy models show larger reductions than diseased models. In all cases, our workflow coupling Dakota's MLMF estimators with the SimVascular cardiovascular modeling framework makes uncertainty quantification feasible for constrained computational budgets.

Computational Hemodynamic Modeling of Arterial Aneurysms: A Mini-Review

Arterial aneurysms are pathological dilations of blood vessels, which can be of clinical concern due to thrombosis, dissection, or rupture. Aneurysms can form throughout the arterial system, including intracranial, thoracic, abdominal, visceral, peripheral, or coronary arteries. Currently, aneurysm diameter and expansion rates are the most commonly used metrics to assess rupture risk. Surgical or endovascular interventions are clinical treatment options, but are invasive and associated with risk for the patient. For aneurysms in locations where thrombosis is the primary concern, diameter is also used to determine the level of therapeutic anticoagulation, a treatment that increases the possibility of internal bleeding. Since simple diameter is often insufficient to reliably determine rupture and thrombosis risk, computational hemodynamic simulations are being developed to help assess when an intervention is warranted. Created from subject-specific data, computational models have the potential to be used to predict growth, dissection, rupture, and thrombus-formation risk based on hemodynamic parameters, including wall shear stress, oscillatory shear index, residence time, and anomalous blood flow patterns. Generally, endothelial damage and flow stagnation within aneurysms can lead to coagulation, inflammation, and the release of proteases, which alter extracellular matrix composition, increasing risk of rupture. In this review, we highlight recent work that investigates aneurysm geometry, model parameter assumptions, and other specific considerations that influence computational aneurysm simulations. By highlighting modeling validation and verification approaches, we hope to inspire future computational efforts aimed at improving our understanding of aneurysm pathology and treatment risk stratification.

HEMODYNAMIC STUDY OF CORONARY ARTERY ANEURYSMS

Background: When the coronary artery expands more than two times its diameter, it will form a coronary artery aneurysm (CAA). CAA can lead to myocardial ischemia. In this paper, the mechanism of myocardial ischemia induced by CAA was studied by geometric multiscale method. Methods: Four kinds of three-dimensional models of CAA with different dilation diameters were established on the basis of normal three-dimensional models. The dilation diameters were 2, 3, 5 and 7 times, capacitance was added after the CAA to simulate the elasticity of the vascular wall. Results:A large number of eddies exist in CAA. 2–7 times model: 1.1–14.4% reduction of blood flow downstream of CAA and 5, 7 times model showed upstream diastolic backward flow, the backward flow rate was 1.1% and 5.6%, respectively. The aveWSS at the CAA was 1.76–0.35[Formula: see text]Pa; the relative retention time was 1.1–14.6[Formula: see text]Pa[Formula: see text]; the average vorticity was 0.0085–231.7[Formula: see text]s[Formula: see text]. Conclusion:CAA can store blood, and the elasticity of the wall of CAA results in the flow of blood upstream. These two reasons make the downstream flow of CAA decrease and easily form intratumoral thrombosis, which may lead to myocardial ischemia.

Out-of-hospital cardiac arrest in a young adult survivor with sequelae of childhood Kawasaki disease: A case report

BACKGROUND

Kawasaki disease (KD) is an acute type of systemic vasculitis involving small to medium-sized muscular arteries and outbreaks during childhood. KD can cause myocardial ischemia, infarction, and sudden cardiac arrest. We present a case of a young adult survivor of out-of-hospital cardiac arrest as late KD sequelae.

CASE SUMMARY

A 29-year-old man with presumed acute KD history at the age of 5 suddenly lost consciousness while jogging and was diagnosed a sudden cardiac arrest by an emergency doctor. After about 10 min cardiopulmonary resuscitation, return of spontaneous circulation was achieved, and the patient was transferred to our hospital. A coronary computed tomography angiogram and coronary angiography revealed extensive calcifications of left anterior descending and right coronary artery aneurysms. The patient was an active individual who took exercise regularly and claimed no previous symptoms of chest pain or shortness of breath on exertion. The most possible cause of his sudden cardiac arrest could be presumed as a thrombus within the coronary artery aneurysms. After that, a thromboembolism induced extensive ischemia, and this ischemia-induced arrhythmia led to a cardiac arrest.

CONCLUSION

Few patients who suffer a late sequela of KD can survive from out-of-hospital cardiac arrest. Medications, surgical intervention, and active follow-up are extremely important for this patient to prevent occurrence of adverse events in the future.

Performance of preconditioned iterative linear solvers for cardiovascular simulations in rigid and deformable vessels

Computing the solution of linear systems of equations is invariably the most time consuming task in the numerical solutions of PDEs in many fields of computational science. In this study, we focus on the numerical simulation of cardiovascular hemodynamics with rigid and deformable walls, discretized in space and time through the variational multiscale finite element method. We focus on three approaches: the problem agnostic generalized minimum residual (GMRES) and stabilized bi-conjugate gradient (BICGS) methods, and a recently proposed, problem specific, bi-partitioned (BIPN) method. We also perform a comparative analysis of several preconditioners, including diagonal, block-diagonal, incomplete factorization, multigrid, and resistance based methods. Solver performance and matrix characteristics (diagonal dominance, symmetry, sparsity, bandwidth and spectral properties) are first examined for an idealized cylindrical geometry with physiologic boundary conditions and then successively tested on several patient-specific anatomies representative of realistic cardiovascular simulation problems. Incomplete factorization preconditioners provide the best performance and results in terms of both strong and weak scalability. The BIPN method was found to outperform other methods in patient-specific models with rigid walls. In models with deformable walls, BIPN was outperformed by BICG with diagonal and Incomplete LU preconditioners.

[Clinical effect and safety of clopidogrel combined with aspirin in antithrombotic therapy for children with Kawasaki disease complicated by small/medium-sized coronary artery aneurysms]

OBJECTIVE

To study the clinical effect and safety of clopidogrel combined with aspirin in antithrombotic therapy for children with Kawasaki disease (KD) complicated by coronary artery aneurysm (CAA).

METHODS

A total of 77 KD children who were diagnosed with multiple small/medium-sized CAAs by echocardiography between January 2013 and June 2018 were enrolled. They were randomly divided into observation group with 38 children (treated with clopidogrel and aspirin) and control group with 39 children (treated with low-molecular-weight heparin and aspirin). All children were followed up regularly, and the first 3 months of the course of the disease was the observation period. The children were observed in terms of the change of the coronary artery and the incidence of complications.

RESULTS

At month 3 of follow-up, among the children in the observation group, 6 had normal coronary artery, 11 had coronary artery retraction, 19 had stable coronary artery, and 2 progressed to giant coronary aneurysm; among the children in the control group, 7 had normal coronary artery, 12 had coronary artery retraction, 19 had stable coronary artery, and 1 progressed to giant coronary aneurysm; there was no significant difference in the change of the coronary artery between the two groups (P>0.05). There were 2 cases of epistaxis and 6 cases of skin ecchymosis in the observation group, and 1 case of epistaxis and 7 cases of petechiae and ecchymosis at the injection site in the control group, and no other serious bleeding events were observed in either group.

CONCLUSIONS

Clopidogrel combined with low-dose aspirin is safe and effective in antithrombotic therapy for children with KD complicated by CAA.

[Clinical effect and safety of clopidogrel combined with aspirin in antithrombotic therapy for children with Kawasaki disease complicated by small/medium-sized coronary artery aneurysms]

OBJECTIVE

To study the clinical effect and safety of clopidogrel combined with aspirin in antithrombotic therapy for children with Kawasaki disease (KD) complicated by coronary artery aneurysm (CAA).

METHODS

A total of 77 KD children who were diagnosed with multiple small/medium-sized CAAs by echocardiography between January 2013 and June 2018 were enrolled. They were randomly divided into observation group with 38 children (treated with clopidogrel and aspirin) and control group with 39 children (treated with low-molecular-weight heparin and aspirin). All children were followed up regularly, and the first 3 months of the course of the disease was the observation period. The children were observed in terms of the change of the coronary artery and the incidence of complications.

RESULTS

At month 3 of follow-up, among the children in the observation group, 6 had normal coronary artery, 11 had coronary artery retraction, 19 had stable coronary artery, and 2 progressed to giant coronary aneurysm; among the children in the control group, 7 had normal coronary artery, 12 had coronary artery retraction, 19 had stable coronary artery, and 1 progressed to giant coronary aneurysm; there was no significant difference in the change of the coronary artery between the two groups (P>0.05). There were 2 cases of epistaxis and 6 cases of skin ecchymosis in the observation group, and 1 case of epistaxis and 7 cases of petechiae and ecchymosis at the injection site in the control group, and no other serious bleeding events were observed in either group.

CONCLUSIONS

Clopidogrel combined with low-dose aspirin is safe and effective in antithrombotic therapy for children with KD complicated by CAA.

A Re-Engineered Software Interface and Workflow for the Open-Source SimVascular Cardiovascular Modeling Package

Patient-specific simulation plays an important role in cardiovascular disease research, diagnosis, surgical planning and medical device design, as well as education in cardiovascular biomechanics. simvascular is an open-source software package encompassing an entire cardiovascular modeling and simulation pipeline from image segmentation, three-dimensional (3D) solid modeling, and mesh generation, to patient-specific simulation and analysis. SimVascular is widely used for cardiovascular basic science and clinical research as well as education, following increased adoption by users and development of a GATEWAY web portal to facilitate educational access. Initial efforts of the project focused on replacing commercial packages with open-source alternatives and adding increased functionality for multiscale modeling, fluid-structure interaction (FSI), and solid modeling operations. In this paper, we introduce a major SimVascular (SV) release that includes a new graphical user interface (GUI) designed to improve user experience. Additional improvements include enhanced data/project management, interactive tools to facilitate user interaction, new boundary condition (BC) functionality, plug-in mechanism to increase modularity, a new 3D segmentation tool, and new computer-aided design (CAD)-based solid modeling capabilities. Here, we focus on major changes to the software platform and outline features added in this new release. We also briefly describe our recent experiences using SimVascular in the classroom for bioengineering education.

A Framework for Comparing Vascular Hemodynamics at Different Points in Time

Computational simulations of blood flow contribute to our understanding of the interplay between vascular geometry and hemodynamics. With an improved understanding of this interplay from computational fluid dynamics (CFD), there is potential to improve basic research and the targeting of clinical care. One avenue for further analysis concerns the influence of time on the vascular geometries used in CFD simulations. The shape of blood vessels changes frequently, as in deformation within the cardiac cycle, and over long periods of time, such as the development of a stenotic plaque or an aneurysm. These changes in the vascular geometry will, in turn, influence flow within these blood vessels. By performing CFD simulations in geometries representing the blood vessels at different points in time, the interplay of these geometric changes with hemodynamics can be quantified. However, performing CFD simulations on different discrete grids leads to an additional challenge: how does one directly and quantitatively compare simulation results from different vascular geometries? In a previous study, we began to address this problem by proposing a method for the simplified case where the two geometries share a common centerline. In this companion paper, we generalize this method to address geometric changes which alter the vessel centerline. We demonstrate applications of this method to the study of wall shear stress in the left coronary artery. First, we compute the difference in wall shear stress between simulations using vascular geometries derived from patient imaging data at two points in the cardiac cycle. Second, we evaluate the relationship between changes in wall shear stress and the progressive development of a coronary aneurysm or stenosis.

Hemodynamic variables in aneurysms are associated with thrombotic risk in children with Kawasaki disease

BACKGROUND

Thrombosis is a major adverse outcome associated with coronary artery aneurysms (CAAs) resulting from Kawasaki disease (KD). Clinical guidelines recommend initiation of anticoagulation therapy with maximum CAA diameter (D_max) ≥8 mm or Z-score ≥ 10. Here, we investigate the role of aneurysm hemodynamics as a superior method for thrombotic risk stratification in KD patients.

METHODS AND RESULTS

We retrospectively studied ten KD patients with CAAs, including five patients who developed thrombosis. We constructed patient-specific anatomic models from cardiac magnetic resonance images and performed computational hemodynamic simulations using SimVascular. Our simulations incorporated pulsatile flow, deformable arterial walls and boundary conditions automatically tuned to match patient-specific arterial pressure and cardiac output. From simulation results, we derived local hemodynamic variables including time-averaged wall shear stress (TAWSS), low wall shear stress exposure, and oscillatory shear index (OSI). Local TAWSS was significantly lower in CAAs that developed thrombosis (1.2 ± 0.94 vs. 7.28 ± 9.77 dynes/cm², p = 0.006) and the fraction of CAA surface area exposed to low wall shear stress was larger (0.69 ± 0.17 vs. 0.25 ± 0.26%, p = 0.005). Similarly, longer residence times were obtained in branches where thrombosis was confirmed (9.07 ± 6.26 vs. 2.05 ± 2.91 cycles, p = 0.004). No significant differences were found for OSI or anatomical measurements such us D_max and Z-score. Assessment of thrombotic risk according to hemodynamic variables had higher sensitivity and specificity compared to standard clinical metrics (D_max, Z-score).

CONCLUSIONS

Hemodynamic variables can be obtained non-invasively via simulation and may provide improved thrombotic risk stratification compared to current diameter-based metrics, facilitating long-term clinical management of KD patients with persistent CAAs.

Visualization of the lenticulostriate arteries at 3T using black-blood T1-weighted intracranial vessel wall imaging: comparison with 7T TOF-MRA

OBJECTIVES

The objective of this study was to explore the feasibility of using intracranial T1-weighted vessel wall imaging (VWI) to visualize the lenticulostriate arteries (LSAs) at 3T.

MATERIAL AND METHODS

Thirteen healthy volunteers were examined with VWI at 3T and TOF-MRA at 7T during the same day. On the vascular skeletons obtained by manual tracing, the number of stems and branches of LSAs were counted. On the most prominent branch in every hemisphere, the contrast-to-noise ratio (CNR), the full length and the local length (5-15 mm above MCAs) were measured and compared between the two methods. Nine stroke patients with intracranial artery stenosis were also recruited into the study. The branches of LSAs were compared between the symptomatic and asymptomatic side.

RESULTS

The extracted vascular trees were in good agreement between 7T TOF-MRA and 3T VWI. The two acquisitions showed similar numbers of the LSA stems. The number of branches revealed by 3T VWI was slightly lower than 7T TOF. The full lengths were slightly lower by VWI at 3T (p = 0.011, ICC = 0.917). The measured local lengths (5-15 mm from MCAs) showed high coherence between VWI and TOF-MRA (p = 0.098, ICC = 0.970). In stroke patients, 12 plaques were identified on MCA segments, and nine plaques were located on the symptomatic side. The average numbers of LSA visualized by 3T VWI were 4.3±1.3 on the symptomatic side and 5.0±1.1 on the asymptomatic side.

CONCLUSION

3T VWI is capable of depicting LSAs, particularly the stems and the proximal segments, with comparable image quality to that of 7T TOF-MRA.

KEY POINTS

• T1-weighted intracranial VWI at 3T allows for black-blood MR angiography of lenticulostriate artery. • 3T intracranial VWI depicts the stems and proximal segments of the lenticulostriate arteries comparable to 7T TOF-MRA. • It is feasible to assess both large vessel wall lesions and lenticulostriate vasculopathy in one scan.

Dynamic flow imaging using 320-detector row CT and motion coherence analysis in coronary aneurysms associated with Kawasaki disease

Introduction We propose a new dynamic flow imaging using 320-detector row CT, and investigate the assessment of coronary flow in aneurysms of Kawasaki disease in adulthood.

METHODS

Six patients with Kawasaki disease and coronary aneurysms associated (26.7 years old) and six controls were enrolled. Dynamic coronary CT angiography with 320-row CT was continuously performed at mid-diastole throughout 15-25 cardiac cycles with prospective Electrocardiogram gating after injection of contrast media. Dynamic data sets of 15-25 cycles were computed into 90-100 data sets by motion coherence image processing. Next, time-density curves for coronary arteries were calculated for all the phases. On the basis of the maximum slope method, coronary flow index was defined as the ratio of the maximum upslope of the attenuation of coronary arteries to the upslope of the attenuation of ascending aorta on the time-density curves. Coronary flow indexes for the proximal and distal sites of coronary arteries and intra-aneurysm were measured.

A method to quantify mechanobiologic forces during zebrafish cardiac development using 4-D light sheet imaging and computational modeling

Blood flow and mechanical forces in the ventricle are implicated in cardiac development and trabeculation. However, the mechanisms of mechanotransduction remain elusive. This is due in part to the challenges associated with accurately quantifying mechanical forces in the developing heart. We present a novel computational framework to simulate cardiac hemodynamics in developing zebrafish embryos by coupling 4-D light sheet imaging with a stabilized finite element flow solver, and extract time-dependent mechanical stimuli data. We employ deformable image registration methods to segment the motion of the ventricle from high resolution 4-D light sheet image data. This results in a robust and efficient workflow, as segmentation need only be performed at one cardiac phase, while wall position in the other cardiac phases is found by image registration. Ventricular hemodynamics are then quantified by numerically solving the Navier-Stokes equations in the moving wall domain with our validated flow solver. We demonstrate the applicability of the workflow in wild type zebrafish and three treated fish types that disrupt trabeculation: (a) chemical treatment using AG1478, an ErbB2 signaling inhibitor that inhibits proliferation and differentiation of cardiac trabeculation; (b) injection of gata1a morpholino oligomer (gata1aMO) suppressing hematopoiesis and resulting in attenuated trabeculation; (c) weak-atriumm58 mutant (wea) with inhibited atrial contraction leading to a highly undeveloped ventricle and poor cardiac function. Our simulations reveal elevated wall shear stress (WSS) in wild type and AG1478 compared to gata1aMO and wea. High oscillatory shear index (OSI) in the grooves between trabeculae, compared to lower values on the ridges, in the wild type suggest oscillatory forces as a possible regulatory mechanism of cardiac trabeculation development. The framework has broad applicability for future cardiac developmental studies focused on quantitatively investigating the role of hemodynamic forces and mechanotransduction during morphogenesis.

Assessment of Coronary Artery Aneurysms Caused by Kawasaki Disease Using Transluminal Attenuation Gradient Analysis of Computerized Tomography Angiograms

Patients with coronary artery aneurysms (CAAs) resulting from Kawasaki disease (KD) are at risk for thrombosis and myocardial infarction. Current guidelines recommend CAA diameter ≥8 mm as the criterion for initiating systemic anticoagulation. Transluminal attenuation gradient (TAG) analysis has been proposed as a noninvasive method for evaluating functional significance of coronary stenoses using computerized tomography angiography (CTA), but has not previously been used in CAA. We hypothesized that abnormal hemodynamics in CAA caused by KD could be quantified using TAG analysis. We studied 23 patients with a history of KD who had undergone clinically indicated CTA. We quantified TAG in the major coronary arteries and aneurysm geometry was characterized using maximum diameter, aneurysm shape index, and sphericity index. A total of 55 coronary arteries were analyzed, 25 of which had at least 1 aneurysmal region. TAG in aneurysmal arteries was significantly lower than in normal arteries (-23.5 ± 10.7 vs -10.5 ± 9.0, p = 0.00002). Aneurysm diameter, aneurysm shape index, and sphericity index were weakly correlated with TAG (r² = 0.01, p = 0.6; r² = 0.15, p = 0.06; r² = 0.16, p = 0.04). This is the first application of TAG analysis to CAA caused by KD, and demonstrates significantly different TAG values in aneurysmal versus normal arteries. Lack of correlation between TAG and CAA geometry suggests that TAG may provide hemodynamic information not available from anatomy alone. TAG represents a possible extension to standard CTA for KD patients who may improve thrombotic risk stratification and aid in clinical decision making.

Computed tomography predict regression of coronary artery aneurysm in patients with Kawasaki disease

BACKGROUND/PURPOSE

The study evaluated possible factors influencing the regression of coronary artery aneurysm (CAA) in patients with Kawasaki disease (KD) through electrocardiographically gated cardiac computed tomography (CT).

METHODS

18 patients with KD exhibited CAAs in at least 2 CT examinations conducted from December 2004 to September 2015, and 37 aneurysms were observed. Every aneurysm was corrected through the descending aorta at the origin level of the left main coronary artery under a normal distribution and measured under a fixed window level. These aneurysms were divided into 2 groups according to regression. Clinical symptoms, laboratory data, and imaging characteristics of both groups were analyzed.

RESULTS

All the aneurysms of 4 patients decreased in size, and totally, 14 aneurysms (37%) regressed. CAA regression tends to occur early after disease onset. No significant differences were observed in sex, aneurysm location, and the distance to the orifice between the 2 groups. The aneurysms with no calcification (p = 0.012), smaller diameter (p = 0.004), younger disease onset age (p = 0.048), and ectatic shape (p < 0.001) were more likely to regress according to univariate analysis. Receiver operating characteristic analysis revealed that the possible cut-off point of the maximal diameter to yield the highest sensitivity (91.3%) and specificity (92.9%) to predict CAA regression was 5.6 mm.

CONCLUSION

Calcified CAAs in patients with KD was less likely to regress. The aneurysm size and shape as well as disease onset age were possible factors influencing regression.

Diagnosis, Treatment, and Long-Term Management of Kawasaki Disease: A Scientific Statement for Health Professionals From the American Heart Association

BACKGROUND

Kawasaki disease is an acute vasculitis of childhood that leads to coronary artery aneurysms in ≈25% of untreated cases. It has been reported worldwide and is the leading cause of acquired heart disease in children in developed countries.

METHODS AND RESULTS

To revise the previous American Heart Association guidelines, a multidisciplinary writing group of experts was convened to review and appraise available evidence and practice-based opinion, as well as to provide updated recommendations for diagnosis, treatment of the acute illness, and long-term management. Although the cause remains unknown, discussion sections highlight new insights into the epidemiology, genetics, pathogenesis, pathology, natural history, and long-term outcomes. Prompt diagnosis is essential, and an updated algorithm defines supplemental information to be used to assist the diagnosis when classic clinical criteria are incomplete. Although intravenous immune globulin is the mainstay of initial treatment, the role for additional primary therapy in selected patients is discussed. Approximately 10% to 20% of patients do not respond to initial intravenous immune globulin, and recommendations for additional therapies are provided. Careful initial management of evolving coronary artery abnormalities is essential, necessitating an increased frequency of assessments and escalation of thromboprophylaxis. Risk stratification for long-term management is based primarily on maximal coronary artery luminal dimensions, normalized as Z scores, and is calibrated to both past and current involvement. Patients with aneurysms require life-long and uninterrupted cardiology follow-up.

CONCLUSIONS

These recommendations provide updated and best evidence-based guidance to healthcare providers who diagnose and manage Kawasaki disease, but clinical decision making should be individualized to specific patient circumstances.