Mechanisms of Myocardial Ischemia Inducing Sudden Cardiac Death in Athletes with Anomalous Coronary Origin from the Opposite Sinus: Insights from a computational fluid dynamic study

Introducing a Novel Innovative Technique for the Recording and Interpretation of Dynamic Coronary Angiography

In the study of coronary artery disease (CAD), the mechanism of plaque formation and development is still an important subject for investigation. A limitation of current coronary angiography (CAG) is that it can only show static images of the narrowing of arterial channels without identifying the mechanism of the disease or predicting its progression or regression. To address this limitation, the CAG technique has been modified. The new approach emphasizes identifying and analyzing blood flow patterns, employing methodologies akin to those used by hydraulic engineers for fluid or gas movement through domestic or industrial pipes and pumps. With the new technique, various flow patterns and arterial phenomena-such as laminar, turbulent, antegrade, retrograde, and recirculating flow and potentially water hammer shock and vortex formation-are identified, recorded, and classified. These phenomena are then correlated with the presence of lesions at different locations within the coronary vasculature. The formation and growth of these lesions are explained from the perspective of fluid mechanics. As the pathophysiology of CAD and other cardiovascular conditions becomes clearer, new medical, surgical, and interventional treatments could be developed to reverse abnormal coronary flow dynamics and restore laminar flow, leading to improved clinical outcomes.

Lumped-parameter model as a non-invasive tool to assess coronary blood flow in AAOCA patients

Anomalous aortic origin of the coronary artery (AAOCA) is a rare disease associated with sudden cardiac death, usually related to physical effort in young people. Clinical routine tests fail to assess the ischemic risk, calling for novel diagnostic approaches. To this aim, some recent studies propose to assess the coronary blood flow (CBF) in AAOCA by computational simulations but they are limited by the use of data from literature retrieved from normal subjects. To overcome this limitation and obtain a reliable assessment of CBF, we developed a fully patient-specific lumped parameter model based on clinical imaging and in-vivo data retrieved during invasive coronary functional assessment of subjects with AAOCA. In such a way, we can estimate the CBF replicating the two hemodynamic conditions in-vivo analyzed. The model can mimic the effective coronary behavior with high accuracy and could be a valuable tool to quantify CBF in AAOCA. It represents the first step required to move toward a future clinical application with the aim of improving patient care. The study was registered at Clinicaltrial.gov with (ID: NCT05159791, date 2021-12-16).

Application of Patient-Specific Computational Fluid Dynamics in Anomalous Aortic Origin of Coronary Artery: A Systematic Review

Anomalous aortic origin of a coronary artery (AAOCA) is a rare congenital heart condition with fixed and dynamic stenotic elements, potentially causing ischemia. Invasive coronary angiography under stress is the established method for assessing hemodynamics in AAOCA, yet it is costly, technically intricate, and uncomfortable. Computational fluid dynamics (CFD) simulations offer a noninvasive alternative for patient-specific hemodynamic analysis in AAOCA. This systematic review examines the role of CFD simulations in AAOCA, encompassing patient-specific modeling, noninvasive imaging-based boundary conditions, and flow characteristics. Screening articles using AAOCA and CFD-related terms prior to February 2023 yielded 19 publications, covering 370 patients. Over the past four years, 12 (63%) publications (259 patients) employed dedicated CFD models, whereas 7 (37%) publications (111 patients) used general-purpose CFD models. Dedicated CFD models were validated for fixed stenosis but lacked dynamic component representation. General-purpose CFD models exhibited variability and limitations, with fluid-solid interaction models showing promise. Interest in CFD modeling of AAOCA has surged recently, mainly utilizing dedicated models. However, these models inadequately replicate hemodynamics, necessitating novel CFD approaches to accurately simulate pathophysiological changes in AAOCA under stress conditions.

Patient-Specific Fluid-Structure Simulations of Anomalous Aortic Origin of Right Coronary Arteries

Objectives

Anomalous aortic origin of the right coronary artery (AAORCA) may cause ischemia and sudden death. However, the specific anatomic indications for surgery are unclear, so dobutamine-stress instantaneous wave-free ratio (iFR) is increasingly used. Meanwhile, advances in fluid–structure interaction (FSI) modeling can simulate the pulsatile hemodynamics and tissue deformation. We sought to evaluate the feasibility of simulating the resting and dobutamine-stress iFR in AAORCA using patient-specific FSI models and to visualize the mechanism of ischemia within the intramural geometry and associated lumen narrowing.

Methods

We developed 6 patient-specific FSI models of AAORCA using SimVascular software. Three-dimensional geometries were segmented from coronary computed tomography angiography. Vascular outlets were coupled to lumped-parameter networks that included dynamic compression of the coronary microvasculature and were tuned to each patient's vitals and cardiac output.

Results

All cases were interarterial, and 5 of 6 had an intramural course. Measured iFRs ranged from 0.95 to 0.98 at rest and 0.80 to 0.95 under dobutamine stress. After we tuned the distal coronary resistances to achieve a stress flow rate triple that at rest, the simulations adequately matched the measured iFRs (r = 0.85, root-mean-square error = 0.04). The intramural lumen remained narrowed with simulated stress and resulted in lower iFRs without needing external compression from the pulmonary root.

Conclusions

Patient-specific FSI modeling of AAORCA is a promising, noninvasive method to assess the iFR reduction caused by intramural geometries and inform surgical intervention. However, the models’ sensitivity to distal coronary resistance suggests that quantitative stress-perfusion imaging may augment virtual and invasive iFR studies.

Applications of computational fluid dynamics to congenital heart diseases: a practical review for cardiovascular professionals

INTRODUCTION

The increased survival rate of patients with congenital heart disease (CHD) has made it likely that 70%-95% of infants with CHDs surviving into adulthood often require careful follow-up and (repeat) interventions. Patients with CHDs often have abnormal blood flow patterns, due to both primary cardiac defect and the consequent surgical or endovascular repair.

AREA COVERED

Computational fluid dynamics (CFD) alone or coupled with advanced imaging tools can assess blood flow patterns of CHDs to both understand their pathophysiology and anticipate the results of surgical or interventional repair.

EXPERT OPINION

CFD is a mathematical technique that quantifies and describes the characteristics of fluid flow using the laws of physics. Through dedicated software based on virtual reconstruction and simulation and patients' real data coming from computed tomography, magnetic resonance imaging, and 3/4 D-ultrasound, reconstruction of models of circulation of most CHD can be accomplished. CFD can provide insights about the pathophysiology of coronary artery anomalies, interatrial shunts, coarctation of the aorta and aortic bicuspid valve, tetralogy of Fallot and univentricular heart, with the capability in some cases of simulating different types of surgical or interventional repair and tailoring the treatment on the basis of these findings.

Transient numerical simulation of the right coronary artery originating from the left sinus and the effect of its acute take-off angle on hemodynamics

Background

An anomalous origin of the right coronary artery from the left coronary artery sinus is usually characterized by an acute take-off angle. Most affected patients have no clinical symptoms; however, some patients have decreased blood flow into the right coronary artery during exercise, which can lead to symptoms such as myocardial ischemia. Most researchers who have studied an anomalous origin of the right coronary artery from the left coronary artery sinus have done so through clinical cases. In this study, we used numerical simulation to evaluate the hemodynamics of this condition and the effect of an acute take-off angle on hemodynamic parameters. We expect that the results of this study will help in further understanding the clinical symptoms of this anomaly and the hemodynamic impact of an acute take-off angle.

Methods

Three-dimensional models were reconstructed based on the computed tomography images from 16 patients with a normal right coronary artery and 26 patients with an anomalous origin of the right coronary artery from the left coronary artery sinus. A numerical simulation of a two-way fluid-structure interaction was executed with ANSYS Workbench software. The blood was assumed to be an incompressible Newtonian fluid, and the vessel was assumed to be an isotropic, linear elastic material. Hemodynamic parameters and the effect of an acute take-off angle were statistically analyzed.

Results

During the systolic period, the wall pressure in the right coronary artery was significantly reduced in patients with an anomalous origin of the right coronary artery (t =1.32 s, P=0.0001; t =1.34-1.46 s, P<0.0001). The wall shear stress in the abnormal group was higher at the beginning of the systolic period (t =1.24 s, P=0.0473; t =1.26 s, P=0.0193; t =1.28 s, P=0.0441). The acute take-off angle was smaller in patients with clinical symptoms (27.81°±4.406°) than in patients without clinical symptoms (31.86°±2.789°; P=0.017). In the symptomatic group, pressure was negatively correlated with the acute take-off angle (P=0.0185-0.0341, r=-0.459 to -0.4167).

Conclusions

This study shows that an anomalous origin of the right coronary artery from the left coronary artery sinus causes changes in hemodynamic parameters, and that an acute take-off angle in patients with this anomaly is associated with terminal ischemia of the right coronary artery.

Echocardiographic Screening of Anomalous Origin of Coronary Arteries in Athletes with a Focus on High Take-Off

Anomalous aortic origin of coronary arteries (AAOCA) represents a rare congenital heart disease. However, this disease is the second most common cause of sudden cardiac death in apparently healthy athletes. The aim of this systematic review is to analyze the feasibility and the detection rate of AAOCA by echocardiography in children and adults. A literature search was performed within the National Library of Medicine using the following keywords: coronary artery origin anomalies and echocardiography; then, the search was redefined by adding the keywords: athletes, children, and high take-off. Nine echocardiographic studies investigating AAOCA and a total of 33,592 children and adults (age range: 12–49 years) were included in this review. Of these, 6599 were athletes (12–49 years). All studies demonstrated a high feasibility and accuracy of echocardiography for the evaluation of coronary arteries origin as well as their proximal tracts. However, some limitations exist: the incidence of AAOCA varied from 0.09% to 0.39% (up to 0.76%) and was lower than described in computed tomography series (0.3–1.8%). Furthermore, echocardiographic views for the evaluation of AAOCA and the definition of “minor” defects (e.g., high take-off coronary arteries) have not been standardized. An echocardiographic protocol to diagnose the high take-off of coronary arteries is proposed in this article. In conclusion, the screening of AAOCA by echocardiography is feasible and accurate when appropriate examinations are performed; however, specific acoustic windows and definitions of defects other than AAOCA need to be standardized to improve sensitivity and specificity.

Computed Tomography-based Patient-specific Biomechanical and Fluid Dynamic Study of Anomalous Coronary Arteries with Origin from the Opposite Sinus and Intramural Course

BACKGROUND

The anomalous coronary arteries originating from the opposite sinus of Valsalva (ACAOS) constitutes one of the most clinically relevant coronary artery anomalies in adults. Exact pathophysiology and the impact of intramural (IM) course segment stenting in ACAOS with IM course (ACAOS-IM) has not been clarified. We aimed to elucidate the pathophysiology and impact of stenting applying biomechanical and computational fluid dynamics to computed tomography (CT) in patient-specific coronary vessel reconstruction.

METHODS

We separated coronary artery (left or L-, right or R-) ACAOS-IM into segments (proximal, mid and distal), based on coronary angiography and coronary CT angiography features, in a series of patients at Rovigo General Hospital, Italy, between 1 January 2003 and 1 January 2018. Blood pressure gradient across the coronary circulation, calculated blood flow, vorticity magnitude, wall shear stress (WSS) and IM segment deformation were analysed by simulating exercise, before and after virtual stent implantation.

RESULTS

In 21 symptomatic patients (13 males, mean age 46.1 ± 8.1 years, L-ACAOS-IM in 9 and R-ACAOS-IM in 12 patients), computational fluid dynamic analysis in both L- and R-ACAOS demonstrated higher basal WSS values in the IM course (9.5 ± 0.2 and 8.6 ± 0.2 Pa for R- and L-ACAOS, respectively), than in the rest of the vessels. These values decreased after stenting. Vorticity magnitude significantly decreased after stenting as well, compared with baseline. Biomechanical deformation analysis revealed not only compression, but also a twisting of the IM segment with a mean distal pressure drop of 32% and 35% in R- and L-ACAOS, respectively, which was corrected by stent implantation.

CONCLUSIONS

In both L- and R-ACAOS subtypes, the IM segment appeared to be phasically compressed and deformed with a degree of twisting that causes resting and exercise cross-sectional deformation and a drop in distal pressure. Stenting of the IM segment results in normalisation of the flow profile, correction of the IM segment deformation and reverses the drop in pressure, for both variants of ACAOS.

SPECT Versus PET Myocardial Perfusion Imaging in Patients with Equivocal CT

PURPOSE OF REVIEW

The most pertinent clinical question in post-coronary computed tomography angiography (CCTA) patients is the assessment of the physiological significance of an anatomically identified stenosis. The clinical application of radionuclide MPI using single-photon emission computed tomography (SPECT) versus positron emission tomography (PET) in the evaluation and management of patients with an inconclusive CCTA is reviewed using a case-based approach.

RECENT FINDINGS

Recent evidence suggests that CCTA is the most sensitive non-invasive test to exclude angiographic CAD and may be an effective first-line test especially among symptomatic low-intermediate risk patients. However, in the presence of angiographic atherosclerosis, its specificity and positive predictive value for identifying flow-limiting stenosis are modest. Radionuclide myocardial perfusion imaging offers accurate quantitative assessment of myocardial ischemia, which helps with risk stratification and patient management especially the potential need for revascularization. Routine accurate quantifications of myocardial blood flow and flow reserve are major advantages of PET MPI, which are especially useful when used in patients at intermediate-high clinical risk.