Coronary Artery Flow Research Articles

Patient-specific modeling of blood flow in the coronary arteries

Patient-specific models of blood flow in the coronary arteries have entered clinical practice worldwide to aid in the diagnosis and management of heart disease. This technology leverages modern AI-based image segmentation methods to extract the geometry of the coronary arteries from noninvasive computed tomography volumetric imaging, computational physiology methods to define boundary conditions and computational fluid dynamic techniques to compute coronary artery flow and pressure. The methods described herein have been used to compute the fractional flow reserve (FFR) in the coronary arteries, namely the ratio of pressure in a coronary artery to the reference aortic pressure under conditions of maximum hyperemia induced by the intravenous administration of a vasodilator to mimic increased coronary artery blood flow as occurs during physical activity. The fractional flow reserve derived from coronary computed tomography angiography (CCTA) using patient-specific models of coronary artery blood flow is referred to as FFRCT and has been validated against invasive measurements using pressure wires in several hundred patients and subsequently evaluated in clinical trials in several thousand patients. Patient-specific models of coronary artery blood flow can be used to predict outcomes of coronary artery revascularization procedures, to identify patients at risk of having a heart attack, and to model tissue perfusion of the microcirculation by coupling with emerging models of cardiac function. This paper provides a state-of-the-art review of computational methods for, and applications of, quantifying blood flow in patient-specific models of the coronary arteries.

Preoperative angiography-derived fractional flow reserve may predict coronary artery bypass grafting occlusion and disease progression.

Graft occlusion after coronary artery bypass grafting (CABG) has been associated with competitive flow of native coronary arteries. To assess with coronary computed tomography angiography (CCTA) graft occlusion and coronary artery disease (CAD) progression of native vessels after CABG and their relationship with angiography-derived vessel fractional flow reserve (vFFR) performed before surgery. Between 2006 and 2018, serial vFFR analyses were obtained before CABG in each major native coronary vessel from two institutions. All patients underwent follow-up CCTA. In 171 consecutive patients, serial preoperative angiograms were suitable for vFFR analysis of 298 grafted and 59 nongrafted vessels. Median time between CABG and CCTA was 2.1 years. Preoperative vFFR was assessed in 131 left anterior descending artery (LAD), 132 left circumflex artery (LCX) and 94 right coronary aretry (RCA) and was less than 0.80 in 255 of 298 bypassed vessels. Graft occlusion was observed at CCTA in 28 of 298 grafts. The median preoperative vFFR value of native coronaries was higher in occluded compared with patent grafts (0.75 vs. 0.60, P < 0.001) and was associated with graft. The best vFFR cut-off to predict graft occlusion was 0.67. Progression of CAD was higher in grafted than in nongrafted vessels (89.6 vs. 47.5%, P < 0.001). Pre-CABG vFFR predicted disease progression of grafted native vessels (AUC = 0.83). Preoperative vFFR derived from invasive coronary angiography was able to predict graft occlusion and CAD progression of grafted coronary arteries.

Computational fluid dynamics as supporting technology for coronary artery disease diagnosis and treatment: an international survey.

Computational fluid dynamics (CFD) is emerging as an effective technology able to improve procedural outcomes and enhance clinical decision-making in patients with coronary artery disease (CAD). The present study aims to assess the state of knowledge, use and clinical acceptability of CFD in the diagnosis and treatment of CAD. We realized a 20-questions international, anonymous, cross-sectional survey to cardiologists to test their knowledge and confidence on CFD as a technology applied to patients suffering from CAD. Responses were recorded between May 18, 2022, and June 12, 2022. A total of 466 interventional cardiologists (mean age 48.4 ± 8.3 years, males 362), from 42 different countries completed the survey, for a response rate of 45.9%. Of these, 66.6% declared to be familiar with the term CFD, especially for optimization of existing interventional techniques (16.1%) and assessment of hemodynamic quantities related with CAD (13.7%). About 30% of respondents correctly answered to the questions exploring their knowledge on the pathophysiological role of some CFD-derived quantities such as wall shear stress and helical flow in coronary arteries. Among respondents, 85.9% would consider patient-specific CFD-based analysis in daily interventional practice while 94.2% declared to be interested in receiving a brief foundation course on the basic CFD principles. Finally, 87.7% of respondents declared to be interested in a cath-lab software able to conduct affordable CFD-based analyses at the point-of-care. Interventional cardiologists reported to be profoundly interested in adopting CFD simulations as a technology supporting decision making in the treatment of CAD in daily practice.

Dilation of the Infarct-Related Coronary Artery to Reduce the Incidence of the No-Reflow Phenomenon in STEMI Patients

Background: The pathogenesis of slow/no-reflow phenomena is a critical socio-medical problem due to high mortality and work disability rates in patients with ST-segment elevation myocardial infarction (STEMI). Slow/no-reflow phenomena are multifactorial involving 4 key elements: 1) distal embolization of the coronary bed of the infarct-related coronary artery; 2) ischemic damage to the myocardium; 3) reperfusion injury of the heart muscle; 4) individual (genetic) susceptibility of the microcirculation to injury. Objective: To analyze the outcomes of percutaneous coronary interventions (PCI) in patients with STEMI and TIMI 0 blood flow of an infarct-related coronary artery based on the strategy to restore antegrade blood flow (balloon predilation or dilation of an infarctrelated artery). Materials and methods: We analyzed treatment outcomes of 209 patients with STEMI and TIMI 0 blood flow. The patients were grouped based on the PCI strategy: group 1 included 147 patients who underwent balloon angioplasty to restore antegrade blood flow, and group 2 included 62 patients who underwent dilation of an infarct-related coronary artery. Results: Our study found that direct stenting in STEMI patients was associated with statistically significantly lower risk of slow/noreflow phenomena (P = 0.001, Pearson’s χ2) and, as a result, better functional outcomes of treatment (chronic heart failure grade classified according to Strazhesko-Vasilenko and by left ventricular ejection fraction) that were also statistically significant (P = 0.001, Pearson’s χ2). Conclusions: Our study demonstrated that the risk of slow/no-reflow phenomena in patients with TIMI 0 blood flow of an infarctrelated coronary artery was statistically significantly lower (P = .001, Pearson’s χ2) in the group of patients who underwent dilation of an infarct-related coronary artery to restore antegrade blood flow. Functional outcomes (chronic heart failure grade and overall survival) were also better in this group of patients (P = .001, Pearson’s Chi-square). Moreover, dilation of an infarct-related coronary artery was associated with preserved left ventricular ejection fraction compared with the group of patients who underwent balloon angioplasty to restore antegrade blood flow (P &lt; 0.001, Pearson’s χ2).

Abstract P1170: Changes In Endothelin Signaling In A Long-term Rat Coronary Culture Resembles Chronic Coronary Syndrome

Background: Coronary artery disease generates changes in the structure and function of the blood vessels. 48hrs organ culture (mimicking the acute loss of blood flow) of coronary arteries induces the upregulation of contractile endothelin type B (ETB) receptors, resembling the pattern seen in ischemic heart disease. MEK inhibitors (U0126 and Trametinib), can acutely inhibit the upregulation of these receptors, illustrating the importance of this pathway. The 48hrs organ culture model has been proven successful for translation in acute ischemic disease, but arterial changes have not been studied in a long-term chronic model which could be important for chronic coronary syndrome. Purpose: 1) Investigate the changes of ETB receptors after incubation in a long-term optimized medium for organ culture, mimicking the reduction of blood flow in chronic coronary syndrome and 2) determine whether Trametinib, would have treatment effect on the upregulation of ETB receptors in both long term and short term culture. Methods: Rat coronary arteries were incubated in organ culture for 48hrs in DMEM ± trametinib (“acute”) or in a long-term optimized medium for organ culture for 14 days (“chronic”). After the incubation, arteries were mounted stainless steel wires (40 μm) on a Mulvany-Halpern arterial wire myograph and cumulative concentration response curves were made to measure arterial contractility to the ETB receptor specific agonist Sarafotoxin (S6c). Trametinib was added at time 0 (for both the acute and chronic organ culture) or 7 days delayed. Results: For the “acute” culture, we observed a high contractile effect in response to S6c (Emax=136.5±18%). The presence of Trametinib greatly reduced this contractile effect (Emax=10±1.9%) and arteries were comparable to fresh (Emax=0.8±0.7%). The rat coronary arteries in the “chronic” culture maintained their ability to contract in response to potassium, and S6c had a strong contractile effect (Emax=74.64±17%). Interestingly, neither trametinib addition at time 0 nor at day 7 could inhibit the functional upregulation of ETB in the chronic model. Conclusion: Chronic coronary syndrome may require new inhibitors of ETB receptor upregulation. This could be investigated with our new long-term rat coronary artery model.

Preclinical validation of the advection diffusion flow estimation method using computational patient specific coronary tree phantoms.

Coronary computed tomography angiography (CCTA) does not allow the quantification of reduced blood flow due to coronary artery disease (CAD). In response, numerical methods based on the CCTA image have been developed to compute coronary blood flow and assess the impact of disease. However to compute blood flow in the coronary arteries, numerical methods require specification of boundary conditions that are difficult to estimate accurately in a patient-specific manner. We describe herein a new noninvasive flow estimation method, called Advection Diffusion Flow Estimation (ADFE), to compute coronary artery flow from CCTA to use as boundary conditions for numerical models of coronary blood flow. ADFE uses image contrast variation along the tree-like structure to estimate flow in each vessel. For validating this method we used patient specific software phantoms on which the transport of contrast was simulated. This controlled validation setting enables a direct comparison between estimated flow and actual flow and a detailed investigation of factors affecting accuracy. A total of 10 CCTA image data sets were processed to extract all necessary information for simulating contrast transport. A spectral element method solver was used for computing the ground truth simulations with high accuracy. On this data set, the ADFE method showed a high correlation coefficient of between estimated flow and the ground truth flow together with an average relative error of only . Comparing the ADFE method with the best method currently available (TAFE) for image-based blood flow estimation, which showed a correlation coefficient of and average error of , it can be concluded that the ADFE method has the potential to significantly improve the quantification of coronary artery blood flow derived from contrast gradients in CCTA images.

A large arteriovenous fistula steals a considerable part of systemic blood flow during veno-arterial extracorporeal circulation support in a porcine model.

Background: Veno-arterial extracorporeal membrane oxygenation (V-A ECMO) is one of the most frequently used mechanical circulatory support devices. Distribution of extracorporeal membrane oxygenation flow depends (similarly as the cardiac output distribution) on regional vascular resistance. Arteriovenous fistulas (AVFs), used frequently as hemodialysis access, represent a low-resistant circuit which steals part of the systemic perfusion. We tested the hypothesis that the presence of a large Arteriovenous fistulas significantly changes organ perfusion during a partial and a full Veno-arterial extracorporeal membrane oxygenation support. Methods: The protocol was performed on domestic female pigs held under general anesthesia. Cannulas for Veno-arterial extracorporeal membrane oxygenation were inserted into femoral artery and vein. The Arteriovenous fistulas was created using another two high-diameter extracorporeal membrane oxygenation cannulas inserted in the contralateral femoral artery and vein. Catheters, flow probes, flow wires and other sensors were placed for continuous monitoring of haemodynamics and organ perfusion. A stepwise increase in extracorporeal membrane oxygenation flow was considered under beating heart and ventricular fibrillation (VF) with closed and opened Arteriovenous fistulas. Results: Opening of a large Arteriovenous fistulas (blood flow ranging from 1.1 to 2.2L/min) resulted in decrease of effective systemic blood flow by 17%-30% (p < 0.01 for all steps). This led to a significant decrease of carotid artery flow (ranging from 13% to 25% after Arteriovenous fistulas opening) following VF and under partial extracorporeal membrane oxygenation support. Cerebral tissue oxygenation measured by near infrared spectroscopy also decreased significantly in all steps. These changes occurred even with maintained perfusion pressure. Changes in coronary artery flow were driven by changes in the native cardiac output. Conclusion: A large arteriovenous fistula can completely counteract Veno-arterial extracorporeal membrane oxygenation support unless maximal extracorporeal membrane oxygenation flow is applied. Cerebral blood flow and oxygenation are mainly compromised by the effect of the Arteriovenous fistulas. These effects could influence brain function in patients with Arteriovenous fistulas on Veno-arterial extracorporeal membrane oxygenation.

Numerical investigation of the effect of changes in blood viscosity on parameters hemodynamic blood flow in the left coronary artery with consideration capturing fluid–solid interaction

Cardiovascular diseases are unfortunately one of the leading causes of death in today's society. It is important to analyze blood flow in various parts of the circulatory system. The coronary artery is made up of four main arteries, and the left coronary artery is responsible for delivering blood to the heart muscle. This research utilizes computational fluid dynamics and finite element methods to investigate and analyze coronary vessels by studying changes in blood characteristics. The aim of this study is to analyze and model the flow of blood under different conditions of the coronary vessels, with a particular focus on the vessels on the left side. This is in response to changes in hematocrit, which can cause an increase or decrease in blood viscosity (μp) (N.s/m2). In general, by applying condition flexibility for the vessel, it is possible to reduce pressure distribution on the wall when compared to the rigid model. When considering changes in viscosity (μ) (kg/m. s), such as an increase from 0.0029 to 0.0067, this can lead to changes in the shear stress distribution (N/m2) on the wall. Specifically, this increase in blood viscosity (μp) (N.s/m2) causes maximum tension, resulting in the wall shear WSS (N/m2) rising from 60 to 154 Pascal's, which is a 140% increase. Based on the current data, it appears that there is a high flow pressure in the artery, resulting in maximum relative pressure values of 6300 and 6450 Pascal's for the rigid and flexible models, respectively, at the separating joint of the bifurcation.

The cardioprotective effects of pharmacological postconditioning with mangafodipir in ST-elevation myocardial infarction, a 4–7 years follow up study

Abstract Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): Futurum - the academy for health and care, Jönköping. Background/Introduction The prevalence of heart failure is increasing as more patients survive a myocardial infarction (MI). MI scar extent is a strong predictor of the development of heart failure due to left ventricular adverse remodeling. Reperfusion injury occurs in the early phase of reperfusion and is linked to the increase of reactive oxygen species (ROS) with calcium overload disrupting the mitochondrial structure, which in turn results in further cell necrosis. Manganese dipyridoxyl diphosphate (mangafodipir) has superoxide dismutase mimetics and may act as a ROS scavenger in the acute phase of myocardial ischemia, hence supporting the myocardial cells in the neutralization of the chemically reactive molecules reducing the MI extent [1–3]. Purpose Our aim was to investigate the cardioprotective role of pharmacological postconditioning with mangafidipir in patients with ST-elevation myocardial infarction (STEMI). Methods Twenty patients with acute STEMI were enrolled between 2009–2014 and followed up 2017. The subjects were randomized in the cath lab into blinded treatment with i.v mangafodipir or control treatment receiving i.v saline prior to restoration of blood flow in the occluded coronary artery. Cardiac magnetic resonance imaging (CMR) at baseline and at follow-up (4–7 years) was performed to evaluate MI scar, LV end diastolic volume (LVEDV), LV end systolic volume (LVESV), LV stroke volume (LVSV), LV ejection fraction (LVEF) and LV mass (LVM). The study was approved by the ethical review board in Linkoping (Dnr 2016/212-31) and registered in the public database at clinicaltrials.gov (NCT 00966563). Results There was no significant difference between the groups in MI scar or LV geometrical and functional properties at baseline, although the duration of ischemia was significantly longer in the mangafodipir group (206 min vs. 144 min, p &amp;lt; 0.05) and a better TIMI grade before pPCI was observed in the control group. The group that underwent pharmacological postconditioning with mangafodipir had lower volumes and higher LVEF (p &amp;lt; 0.05) at follow-up, while the placebo group showed increased LV volumes, see Table 1 and Figure 1. Conclusion Pharmacological postconditioning with mangafodipir in STEMI may have a cardioprotective role in the development of left ventricular adverse remodeling. Due to the limited number of participants, the benefit of mangafodipir needs confirmation in larger studies.

Long-term outcomes after lower extremity bypass in the actively smoking claudicant

ObjectiveSmoking is known to increase complications, including poor wound healing, coagulation abnormalities, and cardiac and pulmonary ramifications. Across specialties, elective surgical procedures are commonly denied to active smokers. Given the base population of active smokers with vascular disease, smoking cessation is encouraged but is not required the way it is for elective general surgery procedures. We aim to study the outcomes of elective lower extremity bypass (LEB) in actively smoking claudicants. MethodsWe queried the Vascular Quality Initiative Vascular Implant Surveillance and Interventional Outcomes Network LEB database from 2003 to 2019. In this database we found 609 (10.0%) never smokers (NS), 3388 (55.3%) former smokers (FS), and 2123 (34.7%) current smokers (CS) who underwent LEB for claudication. We performed two separate propensity score matches without replacement on 36 clinical variables (age, gender, race, ethnicity, obesity, insurance, hypertension, diabetes, coronary artery disease, congestive heart failure, chronic obstructive pulmonary disease, chronic kidney disease, previous coronary artery bypass graft, carotid endarterectomy, major amputation, inflow treatment, preoperative medications and treatment type), one of FS to NS and a second analysis of CS to FS. Primary outcomes included 5-year overall survival (OS), limb salvage (LS), freedom from reintervention (FR), and amputation-free survival (AFS). ResultsPropensity score matches resulted in 497 well-matched pairs of NS and FS. In this analysis we found no difference in terms of OS (HR, 0.93; 95% CI, 0.70-1.24; P = .61), LS (HR, 1.07; 95% CI, 0.63-1.82; P = .80), FR (HR, 0.9; 95% CI,0.71-1.21; P = .59), or AFS (HR, 0.93; 95% CI,0.71-1.22; P = .62). In the second analysis, we had 1451 well-matched pairs of CS and FS. There was no difference in LS (HR, 1.36; 95% CI,0.94-1.97; P = .11) or FR (HR, 1.02; 95% CI,0.88-1.19; P = .76). However, we did find a significant increase in OS (HR, 1.37; 95% CI,1.15-1.64, P <.001) and AFS (HR, 1.38; 95% CI,1.18-1.62; P < .001) in FS compared with CS. ConclusionsClaudicants represent a unique nonemergent vascular patient population that may require LEB. Our study found that FS have better OS and AFS when compared with CS. Additionally, FS mimic nonsmokers at 5-year outcomes for OS, LS, FR, and AFS. Therefore, structured smoking cessation should be a more prominent part of vascular office visits before elective LEB procedures in claudicants.

A novel physics-based model for fast computation of blood flow in coronary arteries

Blood flow and pressure calculated using the currently available methods have shown the potential to predict the progression of pathology, guide treatment strategies and help with postoperative recovery. However, the conspicuous disadvantage of these methods might be the time-consuming nature due to the simulation of virtual interventional treatment. The purpose of this study is to propose a fast novel physics-based model, called FAST, for the prediction of blood flow and pressure. More specifically, blood flow in a vessel is discretized into a number of micro-flow elements along the centerline of the artery, so that when using the equation of viscous fluid motion, the complex blood flow in the artery is simplified into a one-dimensional (1D) steady-state flow. We demonstrate that this method can compute the fractional flow reserve (FFR) derived from coronary computed tomography angiography (CCTA). 345 patients with 402 lesions are used to evaluate the feasibility of the FAST simulation through a comparison with three-dimensional (3D) computational fluid dynamics (CFD) simulation. Invasive FFR is also introduced to validate the diagnostic performance of the FAST method as a reference standard. The performance of the FAST method is comparable with the 3D CFD method. Compared with invasive FFR, the accuracy, sensitivity and specificity of FAST is 88.6%, 83.2% and 91.3%, respectively. The AUC of FFRFAST is 0.906. This demonstrates that the FAST algorithm and 3D CFD method show high consistency in predicting steady-state blood flow and pressure. Meanwhile, the FAST method also shows the potential in detecting lesion-specific ischemia.

Diastolic Left Main Coronary Artery Flow Reversal

In patients undergoing percutaneous cardiac interventions, perioperative transesophageal echocardiography is used routinely, often revealing an unusual pathology that was not previously detected with transthoracic echocardiography. In this e-challenge, the authors present a patient undergoing percutaneous transcatheter aortic valve replacement, with preprocedural transesophageal echocardiography revealing an abnormal color Doppler signal near the left main coronary artery during diastole.

Impact of TAVR on coronary artery hemodynamics using clinical measurements and image‐based patient‐specific in silico modeling

In recent years, transcatheter aortic valve replacement (TAVR) has become the leading method for treating aortic stenosis. While the procedure has improved dramatically in the past decade, there are still uncertainties about the impact of TAVR on coronary blood flow. Recent research has indicated that negative coronary events after TAVR may be partially driven by impaired coronary blood flow dynamics. Furthermore, the current technologies to rapidly obtain non-invasive coronary blood flow data are relatively limited. Herein, we present a lumped parameter computational model to simulate coronary blood flow in the main arteries as well as a series of cardiovascular hemodynamic metrics. The model was designed to only use a few inputs parameters from echocardiography, computed tomography and a sphygmomanometer. The novel computational model was then validated and applied to 19 patients undergoing TAVR to examine the impact of the procedure on coronary blood flow in the left anterior descending (LAD) artery, left circumflex (LCX) artery and right coronary artery (RCA) and various global hemodynamics metrics. Based on our findings, the changes in coronary blood flow after TAVR varied and were subject specific (37% had increased flow in all three coronary arteries, 32% had decreased flow in all coronary arteries, and 31% had both increased and decreased flow in different coronary arteries). Additionally, valvular pressure gradient, left ventricle (LV) workload and maximum LV pressure decreased by 61.5%, 4.5% and 13.0% respectively, while mean arterial pressure and cardiac output increased by 6.9% and 9.9% after TAVR. By applying this proof-of-concept computational model, a series of hemodynamic metrics were generated non-invasively which can help to better understand the individual relationships between TAVR and mean and peak coronary flow rates. In the future, tools such as these may play a vital role by providing clinicians with rapid insight into various cardiac and coronary metrics, rendering the planning for TAVR and other cardiovascular procedures more personalized.

Numerical study on biomechanics in bifurcated coronary artery with plaques of different scenarios considering cardiac motion

During the development of atherosclerosis, plaques of different scenarios are formed at the bifurcation of the coronary arteries, which causes patients to exhibit different symptoms. The purpose of this study was to analyze the effect of plaque in different scenarios on the biomechanics of the bifurcated left coronary artery. In order to reflect the blood flow in the atherosclerotic coronary arteries more exactly, five vivid coronary artery models with a plaque of different scenarios are created based on Computed Tomography (CT) and anatomical images. Furthermore, the three-dimensional artery motion equations are created and fitted to the distal end of the coronary artery to describe the cardiac motion. The reciprocal influence of fluid and solid is also taken into account, constituting a fluid–structure interaction study. The risk of plaques in different scenarios was assessed by analyzing different physical parameters of arteries and blood. The results show that the effect of plaque on arterial stress is concentrated in the proximal coronary artery while the impact on blood flow is mainly focused on the narrow area and downstream of plaque. Wall shear stress promotes plaque growth in the early stages of atherosclerosis and drives plaque rupture after stenosis formation. There is a negative correlation between relative residence time and the degree of coronary artery stenosis and stiffness.

Ticagrelor Treatment is Associated With Increased Coronary Flow Reserve in Survivors of Myocardial Infarction.

The pleiotropic action of ticagrelor, with effects in addition to platelet inhibition, has been shown to improve endothelial function in patients with coronary artery disease. These positive effects are possibly adenosine mediated. This study investigated the association of ticagrelor therapy and coronary artery flow reserve in survivors of myocardial infarction (MI). This was an exploratory, cross-sectional, open substudy of PROFLOW. High-risk individuals with a history of MI were identified. Coronary flow reserve (CFR) was measured non-invasively in the left anterior descending artery using transthoracic Doppler echocardiography. Coronary flow velocity was measured at rest and at maximal flow after induction of hyperaemia by intravenous infusion of adenosine at 140 μg/kg/min. Patients receiving ticagrelor (n=75) were compared with those not receiving ticagrelor (n=506), using simple and multiple linear regression models. Most patients in both groups were treated with aspirin (97% in the ticagrelor and 94% in the non-ticagrelor group). Adjustment for traditional risk factors was conducted. The mean age at study inclusion was 68.5±6.8 years, and most patients were male (81.8%). The simple linear regression analysis showed ticagrelor treatment to be significantly associated with increased CFR: ticagrelor 2.95±0.76 (mean±SD), non-ticagrelor 2.70±0.77, (coefficient 0.25; 95% CI 0.063-0.438; p=0.009). This association was significant in two of the three multiple linear regression models with increasing numbers of variables: Model 1 (0.28; 0.06-0.50; p=0.014), Model 2 (0.26; 0.03-0.48; p=0.025), and borderline significant in Model 3 (0.21; -0.01 to 0.43; p=0.058). Ticagrelor treatment was associated with increased CFR in this high-risk population. Increased CFR may be a clinically important therapeutic effect of ticagrelor in addition to platelet inhibition.

Treatment strategy of different enhanced external counterpulsation frequencies for coronary heart disease and cerebral ischemic stroke: A hemodynamic numerical simulation study

Background and objectivesCurrently, enhanced external counterpulsation (EECP) devices mainly produce one counterpulsation per cardiac cycle. However, the effect of other frequencies of EECP on the hemodynamics of coronary and cerebral arteries is still unclear. It should be investigated whether one counterpulsation per cardiac cycle leads to the optimal therapeutic effect in patients with different clinical indications. Therefore, we measured the effects of different frequencies of EECP on the hemodynamics of coronary and cerebral arteries to determine the optimal counterpulsation frequency for the treatment of coronary heart disease and cerebral ischemic stroke. MethodsWe established 0D/3D geometric multi-scale hemodynamics model of coronary and cerebral arteries in two healthy individuals, and performed clinical trials of EECP to verify the accuracy of the multi-scale hemodynamics model. The pressure amplitude (35 kPa) and pressurization duration (0.6 s) were fixed. The global and local hemodynamics of coronary and cerebral arteries were studied by changing counterpulsation frequency. Three frequency modes, including one counterpulsation in one, two and three cardiac cycles, were applied. Global hemodynamic indicators included diastolic / systolic blood pressure (D/S), mean arterial pressure (MAP), coronary artery flow (CAF), and cerebral blood flow (CBF), whereas local hemodynamic effects included area-time-averaged wall shear stress (ATAWSS) and oscillatory shear index (OSI). The optimal counterpulsation frequency was verified by analyzing the hemodynamic effects of different frequency modes of counterpulsation cycles and full cycles. ResultsIn the full cycle, CAF, CBF and ATAWSS of coronary and cerebral arteries were the highest when one counterpulsation per cardiac cycle was applied. However, in the counterpulsation cycle, the global and local hemodynamic indicators of coronary and cerebral artery reached the highest when one counterpulsation in one cardiac cycle or two cardiac cycles was applied. ConclusionsFor clinical application, the results of global hemodynamic indicators in the full cycle have more clinical practical significance. Combined with the comprehensive analysis of local hemodynamic indicators, it can be concluded that for coronary heart disease and cerebral ischemic stroke, applying one counterpulsation per cardiac cycle may provide the optimal benefit.

Long-term Outcomes in the Smoking Claudicant After Elective Lower Extremity Bypass

Smoking is known to increase complications, including poor wound healing, coagulation abnormalities, and cardiac and pulmonary ramifications. Across specialties, elective surgical procedures are commonly denied to active smokers. Given the base population of active smokers with vascular disease, smoking cessation is encouraged but is not required the way it is in general surgery. We aim to study the outcomes of elective lower extremity bypass (LEB) in actively smoking claudicants. We queried the Vascular Quality Initiative VISION LEB database from 2003 to 2019. In this database we found 609 (10.0%) never smokers (NS), 3388 (55.3%) former smokers (FS), and 2123 (34.7%) current smokers (CS) who underwent LEB for claudication. We performed two separate propensity score matches without replacement on 25 clinical variables (age, gender, race, ethnicity, treatment setting, obesity, insurance, hypertension, diabetes, coronary artery disease, congestive heart failure, chronic obstructive pulmonary disease, chronic kidney disease, previous coronary artery bypass grafting, carotid endarterectomy, major amputation, inflow treatment, preoperative medications and treatment type), one of FS to NS and a second analysis of CS to FS. Primary outcomes included 5-year overall survival (OS), limb salvage (LS), freedom from target lesion reintervention (FTR) and amputation-free survival (AFS). Propensity score matches resulted in 497 well-matched pairs of NS and FS. In this analysis we found no difference in terms of OS (hazard ratio [HR], 0.93; 95% confidence interval [CI], 0.70-1.24; P = .61), LS (HR, 1.08; 95% CI, 0.63-1.82; P = .80), FTR (HR, 0.95; 95% CI, 0.73-1.23; P = .69), or AFS (HR, 0.93; 95% CI, 0.71-1.2; P = .62) (Fig 1). In the second analysis, we had 1451 well-matched pairs of CS and FS. There was no difference in LS (HR, 1.36; 95% CI, 0.94-1.97; P = .10) or FTR (HR, 1.02; 95% CI, 0.87-1.19; P = .85). However, we did find a significant increase in OS (HR, 1.37; 95% CI, 1.15-1.64; P < .001) and AFS (HR, 1.38; 95% CI, 1.18-1.62; P < .001) (Fig 2) in FS compared to CS. Claudicants represent a unique nonemergent vascular patient population who can require LEB. Our study found that former smokers have better overall survival and amputation free survival when compared to current smokers, while former smokers mimic never smokers at 5-year outcomes for OS, LS, FTR, and AFS. Therefore, structured smoking cessation should be a more prominent part of vascular office visits before and after LEB and can even be considered a requirement prior to elective LEB procedures in claudicants.Fig 2Amputation-free survival (AFS) (5 years) for former smokers (FS) and current smokers (CS) after propensity score matching.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Evaluation of cardiac chamber functions by speckle‐tracking echocardiography in the presence of coronary artery flow disturbances other than stenosis: A review

Conditions other than stenosis also disturb the coronary flow. Such conditions include the coronary slow flow phenomenon, coronary artery ectasia, and coronary artery tortuosity. Evidence exists regarding myocardial dysfunction in these conditions. In this review, we present studies that have used speckle-tracking echocardiography to determine whether coronary flow disturbances are accompanied by myocardial dysfunction. Additionally, we seek to show the gaps in knowledge concerning this issue and the dimensions that future studies should consider.

A novel method for calculating CTFFR based on the flow ratio between stenotic coronary and healthy coronary

BackgroundEpicardial coronary stenosis may lead to myocardial ischaemia, and the resulting obstructive coronary artery disease is one of the leading causes of death. CT-derived fractional flow reserve (CT-FFR) has been clinically shown to be an effective method for the noninvasive assessment of coronary artery stenosis. However, this method has the problem that the measurement result is affected by the selected measurement position. ObjectivesThis study was to obtain a novel flow-based approach to coronary CTFFR (CTQFFR), which was not affected by the measurement location. MethodsThis study established healthy-assumed coronary arteries based on narrowed coronary arteries. Based on the assumption that the microvascular resistance remains unchanged in the short term after coronary stenosis treatment, the blood flow in the stenotic coronary artery and the healthy-assumed coronary artery was obtained by numerical simulation, and the CTQFFR based on the blood flow ratio was calculated. The functional relationship between CTQFFR and FFR was fitted by the results of 20 cases. ResultsIn this study, the functional relationship between CTQFFR and FFR was fitted by a quadratic curve, and the variance was 0.8744; the functional relationship between CTQFFR and pressure-based approach to coronary CTFFR (CTPFFR) was fitted by a primary curve, and the variance was 0.9971. There was coronary artery growth in all 20 cases. Preliminary validation results using 10 cases showed 100% accuracy in determining whether coronary artery stenosis required for clinical intervention. The relative error of the coefficient with the results proposed in a previous study was 0.316%. ConclusionThis study proposes a new method for calculating coronary CTFFR, namely, coronary CTQFFR, which is the flow ratio between stenotic coronary and healthy-assumed coronary. This method solves the problem that the downstream CTFFR of coronary stenosis is related to the selected location, which effectively improves the CTFFR at the critical value (CTFFR= 0.8) near reliability. Preliminary research results show that the method obtained in this study has a high accuracy for determining whether there is significant coronary stenosis. However, large multi-centre validation for the feasibility of this method was necessary in our future work.

Patient-specific computational simulation of coronary artery bypass grafting.

Coronary artery bypass graft surgery (CABG) is an intervention in patients with extensive obstructive coronary artery disease diagnosed with invasive coronary angiography. Here we present and test a novel application of non-invasive computational assessment of coronary hemodynamics before and after bypass grafting. We tested the computational CABG platform in n = 2 post-CABG patients. The computationally calculated fractional flow reserve showed high agreement with the angiography-based fractional flow reserve. Furthermore, we performed multiscale computational fluid dynamics simulations of pre- and post-CABG under simulated resting and hyperemic conditions in n = 2 patient-specific anatomies 3D reconstructed from coronary computed tomography angiography. We computationally created different degrees of stenosis in the left anterior descending artery, and we showed that increasing severity of native artery stenosis resulted in augmented flow through the graft and improvement of resting and hyperemic flow in the distal part of the grafted native artery. We presented a comprehensive patient-specific computational platform that can simulate the hemodynamic conditions before and after CABG and faithfully reproduce the hemodynamic effects of bypass grafting on the native coronary artery flow. Further clinical studies are warranted to validate this preliminary data.