Mesh neural networks for SE(3)-equivariant hemodynamics estimation on the artery wall.

Computational fluid dynamics (CFD) is a valuable asset for patient-specific cardiovascular-disease diagnosis and prognosis, but its high computational demands hamper its adoption in practice. Machine-learning methods that estimate blood flow in individual patients could accelerate or replace CFD simulation to overcome these limitations. In this work, we consider the estimation of vector-valued quantities on the wall of three-dimensional geometric artery models. We employ group-equivariant graph convolution in an end-to-end SE(3)-equivariant neural network that operates directly on triangular surface meshes and makes efficient use of training data. We run experiments on a large dataset of synthetic coronary arteries and find that our method estimates directional wall shear stress (WSS) with an approximation error of 7.6% and normalised mean absolute error (NMAE) of 0.4% while up to two orders of magnitude faster than CFD. Furthermore, we show that our method is powerful enough to accurately predict transient, vector-valued WSS over the cardiac cycle while conditioned on a range of different inflow boundary conditions. These results demonstrate the potential of our proposed method as a plugin replacement for CFD in the personalised prediction of hemodynamic vector and scalar fields.

HTK vs. HTK-N for Coronary Endothelial Protection during Hypothermic, Oxygenated Perfusion of Hearts Donated after Circulatory Death.

Protection of the coronary arteries during donor heart maintenance is pivotal to improve results and prevent the development of coronary allograft vasculopathy. The effect of hypothermic, oxygenated perfusion (HOP) with the traditional HTK and the novel HTK-N solution on the coronary microvasculature of donation-after-circulatory-death (DCD) hearts is known. However, the effect on the coronary macrovasculature is unknown. Thus, we maintained porcine DCD hearts by HOP with HTK or HTK-N for 4 h, followed by transplantation-equivalent reperfusion with blood for 2 h. Then, we removed the left anterior descending coronary artery (LAD) and compared the endothelial-dependent and -independent vasomotor function of both groups using bradykinin and sodium-nitroprusside (SNP). We also determined the transcriptome of LAD samples using microarrays. The endothelial-dependent relaxation was significantly better after HOP with HTK-N. The endothelial-independent relaxation was comparable between both groups. In total, 257 genes were expressed higher, and 668 genes were expressed lower in the HTK-N group. Upregulated genes/pathways were involved in endothelial and vascular smooth muscle cell preservation and heart development. Downregulated genes were related to ischemia/reperfusion injury, oxidative stress, mitochondrion organization, and immune reaction. The novel HTK-N solution preserves the endothelial function of DCD heart coronary arteries more effectively than traditional HTK.

Considering the Influence of Coronary Motion on Artery-Specific Biomechanics Using Fluid-Structure Interaction Simulation.

The endothelium in the coronary arteries is subject to wall shear stress and vessel wall strain, which influences the biology of the arterial wall. This study presents vessel-specific fluid-structure interaction (FSI) models of three coronary arteries, using directly measured experimental geometries and boundary conditions. FSI models are used to provide a more physiologically complete representation of vessel biomechanics, and have been extended to include coronary bending to investigate its effect on shear and strain. FSI both without- and with-bending resulted in significant changes in all computed shear stress metrics compared to CFD (p = 0.0001). Inclusion of bending within the FSI model produced highly significant changes in Time Averaged Wall Shear Stress (TAWSS) + 9.8% LAD, + 8.8% LCx, - 2.0% RCA; Oscillatory Shear Index (OSI) + 208% LAD, 0% LCx, + 2600% RCA; and transverse wall Shear Stress (tSS) + 180% LAD, + 150% LCx and + 200% RCA (all p < 0.0001). Vessel wall strain was homogenous in all directions without-bending but became highly anisotropic under bending. Changes in median cyclic strain magnitude were seen for all three vessels in every direction. Changes shown in the magnitude and distribution of shear stress and wall strain suggest that bending should be considered on a vessel-specific basis in analyses of coronary artery biomechanics.

Microcirculatory changes as a hallmark of aging in the heart and kidney / Cambios microcirculatorios como sello distintivo del envejecimiento en el corazón y riñón

SUMMARY: Changes in the microcirculation of multiple tissues and organs have been implicated as a possible mechanism in physiological aging. In particular, vascular endothelial growth factor is a secretory protein responsible for regulating angiogenesis via altering endothelial proliferation, survival, migration, extracellular matrix degradation and cell permeability. The aim of the present study was to evaluate the role of vascular endothelial growth factor in the progression of morphological alterations caused by physiological aging in the heart and kidney and to examine its relation to changes in capillary density. We used two age groups of healthy Wistar rats - 6- and 12-month- old. The expression of vascular endothelial growth factor was examined through immunohistochemistry and immunofluorescence and assessed semi-quantitatively. Changes in capillary density were evaluated statistically and correlated with the expression of vascular endothelial growth factor. We reported stronger immunoreactivity for vascular endothelial growth factor in the left compared to the right ventricle and also observed an increase in its expression in both ventricles in older animals. Contrasting results were reported for the renal cortex and medulla. Capillary density decreased statistically in all examined structures as aging progressed. The studied correlations were statistically significant in the two ventricles in 12-month-old animals and in the renal cortex of both age groups. Our results shed light on some changes in the microcirculation that take place as aging advances and likely contribute to impairment in the function of the examined organs.

Los cambios en la microcirculación de múltiples tejidos y órganos se han implicado como un posible mecanismo en el envejecimiento fisiológico. En particular, el factor de crecimiento endotelial vascular es una proteína secretora responsable de regular la angiogénesis mediante la alteración de la proliferación endotelial, la supervivencia, la migración, la degradación de la matriz extracelular y la permeabilidad celular. El objetivo del presente estudio fue evaluar el papel del factor de crecimiento del endotelio vascular en la progresión de las alteraciones morfológicas causadas por el envejecimiento fisiológico en el corazón y riñón y examinar su relación con los cambios en la densidad capilar. Utilizamos dos grupos de ratas Wistar sanas: 6 y 12 meses de edad. La expresión del factor de crecimiento del endotelio vascular se examinó mediante inmunohistoquímica e inmunofluorescencia y se evaluó semicuantitativamente. Los cambios en la densidad capilar se evaluaron estadísticamente y se correlacionaron con la expresión del factor de crecimiento del endotelio vascular. Informamos una inmunorreactividad más fuerte para el factor de crecimiento endotelial vascular en el ventrículo izquierdo en comparación con el derecho y también observamos un aumento en su expresión en ambos ventrículos en animales mayores. Se informaron resultados contrastantes para la corteza renal y la médula. La densidad capilar disminuyó estadísticamente en todas las estructuras examinadas a medida que avanzaba el envejecimiento. Las correlaciones estudiadas fueron estadísticamente significativas en los dos ventrículos en animales de 12 meses y en la corteza renal de ambos grupos de edad. Nuestros resultados arrojan luz sobre algunos cambios en la microcirculación que tienen lugar a medida que avanza el envejecimiento y probablemente contribuyan a un deterioro en la función de los órganos examinados.

The role of HIV as a risk modifier for coronary endothelial function in young adults.

BACKGROUND: People living with HIV have an increased risk of cardiovascular disease (CVD). Although coronary endothelial function (CEF) is an early direct indicator of CVD, only a few studies have been able to interrogate CEF directly. Most studies have examined vascular endothelial function through indirect assessment of brachial flow-mediated dilatation (FMD). However, peripheral arteries are significantly larger and manifest atherogenesis differently from the coronary arteries, and so produce conflicting results. Additionally, none of these studies focused on young adults who acquired HIV perinatally or in early childhood. OBJECTIVE: The present study investigates CEF in a unique population of young adults with lifelong HIV using direct magnetic resonance imaging (MRI) of coronary FMD (corFMD) with an in-house developed MRI-integrated isometric handgrip exercise system with continuous feedback and monitoring mechanisms (fmIHE). METHODS: Young adults who acquired HIV perinatally or in early childhood (n = 23) and group-matched healthy participants (n = 12) completed corFMD-MRI with fmIHE. CorFMD was measured as the coronary cross-sectional area response to the fmIHE. RESULTS: In univariable and multivariable regression analysis, HIV status was a significant risk modifier. CD8+ T-cell count and smoking pack-years and their interaction with HIV status were independently associated with impaired coronary artery response to fmIHE. In people living with HIV, corFMD was significantly inversely correlated with CD8+ T-cells and smoking pack-years. In a multivariable regression analysis adjusted for age and body mass index, CD8+ T-cells and smoking and their interaction with HIV status remained significant independent predictors of coronary endothelial dysfunction. DISCUSSION: In this unique population of young adults, HIV status was a significant risk modifier, and immune activation and smoking were associated with decreased CEF, directly measured from the coronary vascular response to fmIHE. CONCLUSIONS: Management of CVD risk factors such as smoking and developing strategies that target immune activation in people living with HIV are warranted.

Tissue-growth-based synthetic tree generation and perfusion simulation.

Biological tissues receive oxygen and nutrients from blood vessels by developing an indispensable supply and demand relationship with the blood vessels. We implemented a synthetic tree generation algorithm by considering the interactions between the tissues and blood vessels. We first segment major arteries using medical image data and synthetic trees are generated originating from these segmented arteries. They grow into extensive networks of small vessels to fill the supplied tissues and satisfy the metabolic demand of them. Further, the algorithm is optimized to be executed in parallel without affecting the generated tree volumes. The generated vascular trees are used to simulate blood perfusion in the tissues by performing multiscale blood flow simulations. One-dimensional blood flow equations were used to solve for blood flow and pressure in the generated vascular trees and Darcy flow equations were solved for blood perfusion in the tissues using a porous model assumption. Both equations are coupled at terminal segments explicitly. The proposed methods were applied to idealized models with different tree resolutions and metabolic demands for validation. The methods demonstrated that realistic synthetic trees were generated with significantly less computational expense compared to that of a constrained constructive optimization method. The methods were then applied to cerebrovascular arteries supplying a human brain and coronary arteries supplying the left and right ventricles to demonstrate the capabilities of the proposed methods. The proposed methods can be utilized to quantify tissue perfusion and predict areas prone to ischemia in patient-specific geometries.

Combined use of hyperemic and non-hyperemic pressure ratios for revascularization decision-making: From the ILIAS registry.

OBJECTIVE: The aim of this study is to evaluate the diagnostic and prognostic value of non-hyperaemic Pd/Pa and to determine its additional value when combined with the gold standard hyperaemic pressure ratio (FFR) to guide revascularization. METHODS: In a large, multi-center, retrospective registry, we included a total of 2141 patients with a clinical indication for coronary angiography providing physiological data in 2726 vessels. A classification was made based on the FFR (cut-off value: 0.80) and non-hyperaemic Pd/Pa (cut-off value: 0.92) values and the primary outcome was target-vessel failure (TVF) at 5-year follow-up. RESULTS: Mean age was 63 ± 10.0 and 75% of the study population were men. Regression analysis showed an overall good correlation between FFR and non-hyperaemic Pd/Pa (r = 0.73, p < 0.005) and discordance was present in 17% of the vessels. Resting Pd/Pa was independently associated with TVF at 5-year follow-up (HR 0.08, 95%CI: 0.02-0.27; p < 0.005). The risk for TVF was the lowest in vessles with concordant normal pressure ratio's, with the highest risk in vessels with any abnormal pressure ratio in which revascularization was deferred. In these vessels, there was no difference in risk for TVF between the discordant and concordant abnormal values. CONCLUSION: Abnormal pressure ratios in both non-hyperemic and hyperemic conditions portend important prognostic value. Combined application of FFR and non-hyperemic Pd/Pa efficiently identifies those vessels with concordant normal resting and hyperemic pressure ratios of which long-term clinical outcomes are excellent. These data lead to hypothesize that the decision to defer revascularization should potentially be based on combined non-hyperemic and hyperemic pressure ratios. CLINICAL TRIAL REGISTRATION: Inclusive Invasive Physiological Assessment in Angina Syndromes Registry (ILIAS Registry), NCT04485234.

Relationship of Plaque Features at Coronary CT to Coronary Hemodynamics and Cardiovascular Events.

Background Plaque assessments with coronary CT angiography (CCTA) and coronary flow indexes have prognostic implications. Purpose To investigate the association and additive prognostic value of plaque burden and characteristics at CCTA with coronary pressure and flow. Materials and Methods Data of patients with coronary artery disease who underwent CCTA within 90 days before physiologic assessments at tertiary cardiovascular centers between January 2011 and December 2018 were retrospectively analyzed, which included fractional flow reserve (FFR), resting distal coronary artery pressure (Pd)-to-aortic pressure (Pa) ratio (hereafter, Pd/Pa), coronary flow reserve (CFR), hyperemic flow (1/hyperemic mean transit time [Tmn]), resting flow (1/resting Tmn), and index of microcirculatory resistance (IMR). Four high-risk plaque (HRP) attributes at CCTA defined high disease burden (plaque burden, ≥70%; minimum lumen area, <4 mm2) and adverse plaque (low-attenuation plaque, positive remodeling). Their lesion-specific relationships with coronary hemodynamic parameters and major adverse cardiovascular events (MACE) were investigated using a generalized estimating equation and marginal Cox model. Results Among 406 lesions from 335 patients (mean age, 67 years ± 10 [SD]; 259 men), high disease burden is predicted by FFR (odds ratio [OR], 0.55; P < .001), resting Pd/Pa (OR, 0.47; P < .001), CFR (OR, 0.85; P = .004), and hyperemic flow (OR, 0.91; P = .03), and adverse plaque by FFR (OR, 0.67; P < .001), resting Pd/Pa (OR, 0.69; P = .001), hyperemic flow (OR, 0.76; P = .006), resting flow (OR, 0.54; P = .001), and IMR (OR, 1.27; P = .008). High disease burden (hazard ratio [HR], 4.0; P = .004) and adverse plaque (HR, 2.7; P = .02) were associated with a higher risk of MACE (n = 27) over median 2.9-year follow-up. In six lesion subsets with normal flow or pressure, at least three HRP attributes predicted a higher MACE rate (HR range, 2.6-6.3). Conclusion High-risk plaque features and plaque burden at coronary CT angiography were associated with cardiovascular events independent of coronary hemodynamic parameters. Clinical trial registration no. NCT04037163 © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Leipsic and Tzimas in this issue.

Study of Non-Newtonian blood flow - heat transfer characteristics in the human coronary system with an external magnetic field.

This paper proposes a novel mathematical model of non-Newtonian blood flow and heat transfer in the human coronary system with an external magnetic field. As the blood viscosity is assumed to depend not only on shear rate but also on temperature and magnet strength, the modified Carreau-Yasuda viscosity model is formulated. The computational domain includes the base of the aorta, the right coronary artery, and the left coronary artery, with the left circumflex and left anterior descending arteries. The element-based finite volume method is derived for the solution of the proposed model. Numerical simulations are carried out to investigate the magnetic field effect on the blood flow-heat transfer characteristic in the human coronary system. It is found that the magnetic field has a significant impact on fluid viscosity, leading to enhanced fluid velocity.

Transient wall shear stress estimation in coronary bifurcations using convolutional neural networks.

BACKGROUND AND OBJECTIVE: Haemodynamic metrics, such as blood flow induced shear stresses at the inner vessel lumen, are associated with the development and progression of coronary artery disease. Understanding these metrics may therefore improve the assessment of an individual's coronary disease risk. However, the calculation of such luminal Wall Shear Stress (WSS) using traditional Computational Fluid Dynamics (CFD) methods is relatively slow and computationally expensive. As a result, CFD based haemodynamic computation is not suitable for integrated and large-scale use in clinical settings. METHODS: In this work, deep learning techniques are proposed as an alternative method to CFD, whereby luminal WSS magnitude can be predicted in coronary bifurcations throughout the cardiac cycle based on the steady state solution (which takes <120 seconds to calculate including preprocessing), vessel geometry and additional global features. The deep learning model is trained on a dataset of 101 patient-specific and 2626 synthetic left main bifurcation models with 26 separate patient-specific cases used as the test set. RESULTS: The model showed high fidelity predictions with <5% (normalised against mean WSS magnitude) deviation to CFD derived values as the gold-standard method, while being orders of magnitude faster with on average <2 minutes versus 3 hours computation for transient CFD. CONCLUSIONS: This method therefore offers a new approach to substantially reduce the computational cost involved in, for example, large-scale population studies of coronary haemodynamic metrics, and may therefore open the pathway for future clinical integration.

Linking the region-specific tissue microstructure to the biaxial mechanical properties of the porcine left anterior descending artery.

Coronary atherosclerosis is the main cause of death worldwide. Advancing the understanding of coronary microstructure-based mechanics is fundamental for the development of therapeutic tools and surgical procedures. Although the passive biaxial properties of the coronary arteries have been extensively explored, their regional differences and the relationship between tissue microstructure and mechanics have not been fully characterized. In this study, we characterized the passive biaxial mechanical properties and microstructural properties of the proximal, medial, and distal regions of the porcine left anterior descending artery (LADA). We also attempted to relate the biaxial stress-stretch response of the LADA and its respective birefringent responses to the polarized light for obtaining information about the load-dependent microstructural variations. We found that the LADA extensibility is reduced in the proximal-to-distal direction and that the medial region exhibits more heterogeneous mechanical behavior than the other two regions. We have also observed highly dynamic microstructural behavior where fiber families realign themselves depending on loading. In addition, we found that the microstructure of the distal region exhibited highly aligned fibers along the longitudinal axis of the artery. To verify this microstructural feature, we imaged the LADA specimens with multi-photon microscopy and observed that the adventitia microstructure transitioned from a random fiber network in the proximal region to highly aligned fibers in the distal region. Our findings could offer new perspectives for understanding coronary mechanics and aid in the development of tissue-engineered vascular grafts, which are currently limited due to their mismatch with native tissue in terms of mechanical properties and microstructural features. STATEMENT OF SIGNIFICANCE: The tissue biomechanics of coronary arteries is fundamental for the development of revascularization techniques such as coronary artery bypass. These therapeutics require a deep understanding of arterial mechanics, microstructure, and mechanobiology to prevent graft failure and reoperation. The present study characterizes the unique regional mechanical and microstructural properties of the porcine left anterior descending artery using biaxial testing, polarized-light imaging, and confocal microscopy. This comprehensive characterization provides an improved understanding of the collagen/elastin architecture in response to mechanical loads using a region-specific approach. The unique tissue properties obtained from this study will provide guidance for the selection of anastomotic sites in coronary artery bypass grafting and for the design of tissue-engineered vascular grafts.

Numerical study of the effect of hemodynamic variables on LDL concentration through the single layer of the Left Anterior Descending coronary artery (LAD) under the heart pulse.

Heart attack is one of the most common causes of death in the world. Coronary artery disease is the most recognized cause of heart attack whose onset and progression have been attributed to low-density lipoprotein (LDL) passing through the wall of the artery. In this paper, hemodynamic variables as well as the concentration of LDL through the coronary porous artery at the Left Anterior Descending coronary artery (LAD), and its first diagonal branch (D1) under the heart motion investigated using computational simulation. The geometry that has been studied in this paper is the first bifurcation of Left Anterior Descending (LAD) that has been placed on a perimeter of hypothetical sphere representative of the heart geometry. Sinusoidal variations of sphere radii, simulated pulsating movement of the heart. Blood has been considered as a Newtonian and incompressible flow with pulsatile flow rate and real physiological profile. The plasma filtration boundary condition used over the walls in order to simulate the concentration of LDL to a one-layer artery wall. Variations in the concentration of LDL on the artery wall and its relation to oscillation on shear stress on the artery wall under different conditions are presented. Moreover, the effects of the pulsating inlet flow and dynamic movement of the artery are explored. The results declared that minimum shear stress and maximum LDL concentration take place at the bifurcation and on the myocardial wall which is in complete agreement with clinical studies. Furthermore, it has been shown that the heart pulse has a slight effect on the average time of concentration (0.1% increase); however, by analyzing all time steps, one could observe that the maximum concentration rises in some time steps; where this increases the possibility of LDL presence and helps them diffuse inside the artery wall.

Coronary Arterial Function and Disease in Women With No Obstructive Coronary Arteries.

Ischemic heart disease (IHD) is the leading cause of mortality in women. While traditional cardiovascular risk factors play an important role in the development of IHD in women, women may experience sex-specific IHD risk factors and pathophysiology, and thus female-specific risk stratification is needed for IHD prevention, diagnosis, and treatment. Emerging data from the past 2 decades have significantly improved the understanding of IHD in women, including mechanisms of ischemia with no obstructive coronary arteries and myocardial infarction with no obstructive coronary arteries. Despite this progress, sex differences in IHD outcomes persist, particularly in young women. This review highlights the contemporary understanding of coronary arterial function and disease in women with no obstructive coronary arteries, including coronary anatomy and physiology, mechanisms of ischemia with no obstructive coronary arteries and myocardial infarction with no obstructive coronary arteries, noninvasive and invasive diagnostic strategies, and management of IHD.

Sex Differences in Myocardial and Vascular Aging.

It is well known that cardiovascular disease manifests differently in women and men. The underlying causes of these differences during the aging lifespan are less well understood. Sex differences in cardiac and vascular phenotypes are seen in childhood and tend to track along distinct trajectories related to dimorphism in genetic factors as well as response to risk exposures and hormonal changes during the life course. These differences underlie sex-specific variation in cardiovascular events later in life, including myocardial infarction, heart failure, ischemic stroke, and peripheral vascular disease. With respect to cardiac phenotypes, females have intrinsically smaller body size-adjusted cardiac volumes and they tend to experience greater age-related wall thickening and myocardial stiffening with aging. With respect to vascular phenotypes, sexual dimorphism in both physiology and pathophysiology are also seen, including overt differences in blood pressure trajectories. The majority of sex differences in myocardial and vascular alterations that manifest with aging seem to follow relatively consistent trajectories from the very early to the very later stages of life. This review aims to synthesize recent cardiovascular aging-related research to highlight clinically relevant studies in diverse female and male populations that can inform approaches to improving the diagnosis, management, and prognosis of cardiovascular disease risks in the aging population at large.

Coronary Artery Stenting Affects Wall Shear Stress Topological Skeleton.

Despite the important advancements in the stent technology for the treatment of diseased coronary arteries, major complications still affect the postoperative long-term outcome. The stent-induced flow disturbances, and especially the altered wall shear stress (WSS) profile at the strut level, play an important role in the pathophysiological mechanisms leading to stent thrombosis (ST) and in-stent restenosis (ISR). In this context, the analysis of the WSS topological skeleton is gaining more and more interest by extending the current understanding of the association between local hemodynamics and vascular diseases. This study aims to analyze the impact that a deployed coronary stent has on the WSS topological skeleton. Computational fluid dynamics (CFD) simulations were performed in three stented human coronary artery geometries reconstructed from clinical images. The selected cases presented stents with different designs (i.e., two contemporary drug-eluting stents and one bioresorbable scaffold) and included regions with stent malapposition or overlapping. A recently proposed Eulerian-based approach was applied to analyze the WSS topological skeleton features. The results highlighted that the presence of single or multiple stents within a coronary artery markedly impacts the WSS topological skeleton. In particular, repetitive patterns of WSS divergence were observed at the luminal surface, highlighting a WSS contraction action exerted proximal to the stent struts and a WSS expansion action distal to the stent struts. This WSS action pattern was independent from the stent design. In conclusion, these findings could contribute to a deeper understanding of the hemodynamics-driven processes underlying ST and ISR.

Scaling laws and the left main coronary artery bifurcation. A combination of geometric and simulation analyses.

The geometry of coronary arteries is believed to play the role as an atherosclerotic risk factor on its own. The full characterization of the normal coronary network has been reported in the literature. Reports on the integration of geometry and functional data for normal coronary vessels started to proliferate more recently. In this work, we analyze and integrate the geometric data retrieved from angiography images of the left main coronary bifurcation in angiographically normal patients and hemodynamic data generated from blood flow models to analyze the role of allometric laws and the connection between flow distribution and wall shear stress loads on the left anterior descending and left circumflex arteries. This in-silico study contributes to the characterization of normal coronary anatomy and its impact on the hemodynamic shear stresses acting over the vessel wall, shedding light on the impact of geometry-based versus simulation-based hypotheses to define boundary conditions for numerical simulations. We discuss the role of the wall shear stress corresponding to scenarios adopted by the scientific community and the ones proposed in this study. For the simulation-based hypothesis, we propose an iterative strategy to define boundary conditions at the main left coronary bifurcation, such that wall shear stresses are matched between the left descending and left circumflex arteries. From this study, we conclude that a one-fits-all power law exponent of 7/3 results in an good trade-off between computational cost and wall shear stress balance between daughter vessels.

Comparison between OPCABG and CABG Surgical Revascularization Using Transit Time Flow Measurement (TTFM).

OBJECTIVE: To compare the intraoperative quality of coronary anastomoses performed with or without cardiopulmonary bypass using transit time flow measurement (TTFM) parameters. METHODS: We collected data from 588 consecutive patients who underwent surgical revascularization. We retrospectively reviewed data from two groups: 411 with cardiopulmonary bypass (CABG group) and 177 off-pump (OPCABG group). Transit time flow measurement parameters: mean graft flow (MGF), pulsatile index (PI), and diastolic filing (DF) were measured for each graft and patient. RESULTS: Patients in the OPCABG group had higher EuroSCORE compared with the CABG group (3.53 ± 2.32 versus 2.84 ± 2.15, P = .002). Overall comparison of TTFM parameters showed no statistical difference between the two surgical techniques except for PI in circumflex artery territory, which was higher in the OPCABG group for all types of grafts 3.0 ± 4.9 versus 2.4 ± 2.0 in, P = .026. CONCLUSION: The comparison between OPCABG and CABG in this study showed comparable results with both surgical techniques. PI was higher in the OPCABG group in harder-to-reach vessel territories. Measurement of transit time may improve the quality, safety, and efficacy of coronary artery bypass grafting and should be considered as a routine procedure.

Increased and continuous coronary arterial flow was induced by LV uncoupling condition using combined treatment of a microaxial heart pump and venoarterial extracorporeal membrane oxygenation.

An emerging therapeutic modality, ECPELLA, which combines a transvalvular microaxial left ventricular (LV) assist device, Impella, and venoarterial membrane oxygenation (VA-ECMO), has been applied for patients with refractory cardiogenic shock. During ECPELLA support, VA-ECMO increases the LV load, whereas the Impella reduces the LV load. Studies reported that coronary perfusion is influenced by LV unloading conditions, and the effective degree of LV unloading to increase the coronary perfusion on ECPELLA support remains to be determined. Here, we reported a cardiogenic shock case whose coronary arterial flow was assessed by transesophageal echocardiography during ECPELLA support. The left anterior descending coronary artery (LAD) peak blood flow velocity and the velocity time integral (VTI) were not significantly increased when blood was ejected from the LV (partial LV unloading). When the LV blood ejection was completely bypassed by Impella confirmed by non-pulsatile aortic pressure with significantly reduced LV pressure with no aortic valve opening (LV uncoupling: no blood ejection from the LV), both peak velocity and VTI of the LAD were markedly increased and the blood flow became continuous throughout the cardiac cycle. Our case suggests that the coronary arterial flow in the injured myocardium is sensitive to degrees of LV unloading on ECPELLA support.