Farhad Rikhtegar Nezami- PhD
- Professor (Assistant) at Harvard Medical School
Farhad Rikhtegar Nezami
- PhD
- Professor (Assistant) at Harvard Medical School
About
76
Publications
29,488
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
1,285
Citations
Introduction
Farhad Rikhtegar currently works as a lead investigator and faculty member at BWH, Harvard Medical school. He is also affiliated to the Harvard-MIT Center for Biomedical Engineering, Massachusetts Institute of Technology. Farhad does research in Bioinformatics, Biotechnology, Bioengineering and Biomechanics.
Current institution
Additional affiliations
October 2014 - March 2020
November 2013 - March 2014
September 2009 - October 2013
Publications
Publications (76)
We present RAGnosis, a fully offline, retrieval-augmented framework for interpreting unstructured clinical text using open-weight large language models. As a proof of concept, we apply RAGnosis to the task of paravalvular leak (PVL) classification from cardiac catheterization reports, a process that typically requires slow, expert-driven interpreta...
Accurate segmentation of the left ventricle (LV) in cardiac CT images is crucial for assessing ventricular function and diagnosing cardiovascular diseases. Common semi-automatic segmentation often includes unwanted structures, such as papillary muscles, due to low contrast between the LV wall and surrounding tissues. In this study, we address this...
Freeze casting, a manufacturing technique widely applied in biomedical fields for fabricating biomaterial scaffolds, poses challenges for predicting directional solidification due to its highly nonlinear behavior and complex interplay of process parameters. Conventional numerical methods, such as computational fluid dynamics (CFD), require adequate...
Virtual interventions enable the physics-based simulation of device deployment within coronary arteries. This framework allows for counterfactual reasoning by deploying the same device in different arterial anatomies. However, current methods to create such counterfactual arteries face a trade-off between controllability and realism. In this study,...
Despite recent advances in diagnosis and treatment, atherosclerotic coronary artery diseases remain a leading cause of death worldwide. Various imaging modalities and metrics can detect lesions and predict patients at risk; however, identifying unstable lesions is still difficult. Current techniques cannot fully capture the complex morphology-modul...
Despite recent advances in diagnosis and treatment, atherosclerotic coronary artery diseases remain a leading cause of death worldwide. Various imaging modalities and metrics can detect lesions and predict patients at risk; however, identifying unstable lesions is still difficult. Current techniques cannot fully capture the complex morphology-modul...
Introduction Coronary artery disease poses a significant global health challenge, often leading to major adverse cardiac events, with acute coronary syndrome being its most perilous form. Despite advancements, current imaging methods struggle to effectively diagnose and predict the complex mechanical responses underlying plaque destabilization. Whi...
BACKGROUND
Endothelial cells (ECs) are capable of quickly responding in a coordinated manner to a wide array of stresses to maintain vascular homeostasis. Loss of EC cellular adaptation may be a potential marker for cardiovascular disease and a predictor of poor response to endovascular pharmacological interventions such as drug-eluting stents. Her...
Despite recent advances in diagnosis and treatment, atherosclerotic coronary artery diseases remain a leading cause of death worldwide. Various imaging modalities and metrics can detect lesions and predict patients at risk; however, identifying unstable lesions is still difficult. Current techniques cannot fully capture the complex morphology-modul...
Aortic stenosis (AS) is the most prevalent heart valve disease in western countries that poses a significant public health challenge due to the lack of a medical treatment to prevent valve calcification. Given the aging population demographic, the prevalence of AS is projected to rise, resulting in a progressively significant healthcare and economi...
As an FDA-approved biopolymer, silk has been contemplated for a wide range of applications based on its unique merits, such as biocompatibility, biodegradability, and piezoelectricity. As silk, in both crystalline structure and amorphous state, exhibits unique physical, mechanical, and biological properties (promoting cell migration, differentiatio...
Coronary artery disease persists as the world’s leading cause of death and often associated with atherosclerotic plaque disruption in the face of excessive plaque structure stress (PSS). Lesion tolerance of PSS correlates with the material and morphological properties of the arterial constituents. 2D-Finite Element Analysis (FEA) performed on model...
Aortic stenosis (AS) is the most common valvular heart disease in the western world, particularly worrisome with an ever-aging population wherein postoperative outcome for aortic valve replacement is strongly related to the timing of surgery in the natural course of disease. Yet, guidelines for therapy planning overlook insightful, quantified measu...
The global burden of cardiovascular disease is immense. Within this broad category of diseases, heart failure is recognized as a major contributor to both adverse patient events and healthcare spending. As western populations age, epidemiologic data projects significant increases in the prevalence of heart failure. The gap between those with end-st...
Cardiovascular diseases are the leading cause of mortality, morbidity, and hospitalization around the world. Recent technological advances have facilitated analyzing, visualizing, and monitoring cardiovascular diseases using emerging computational fluid dynamics, blood flow imaging, and wearable sensing technologies. Yet, computational cost, limite...
Coronary Computed Tomography Angiography (CCTA) provides information on the presence, extent, and severity of obstructive coronary artery disease. Large-scale clinical studies analyzing CCTA-derived metrics typically require ground-truth validation in the form of high-fidelity 3D intravascular imaging. However, manual rigid alignment of intravascul...
Purpose: Modern medical imaging enables clinicians to effectively diagnose, monitor, and treat diseases. However, clinical decision-making often relies on combined evaluation of either longitudinal or disparate image sets, necessitating coregistration of multiple acquisitions. Promising coregistration techniques have been proposed; however, availab...
The aim of this study was to determine whether specific three-dimensional aortic shape features, extracted via statistical shape analysis (SSA), correlate with the development of thoracic ascending aortic dissection (TAAD) risk and associated aortic hemodynamics. Thirty-one patients followed prospectively with ascending thoracic aortic aneurysm (AT...
Extracorporeal membrane oxygenation (ECMO) is a vital mechanical circulatory support modality capable of restoring perfusion for the patient in circulatory failure. Despite increasing adoption of ECMO, there is incomplete understanding of its effects on systemic hemodynamics and how the vasculature responds to varying levels of continuous retrograd...
Atherosclerosis is a complex disease altering vasculature morphology, and subsequently flow, with progressive plaque formation, mural disruption, and lumen occlusion. Determination of clinically-relevant plaque components—particularly calcium, lipid, and fibrous tissue—has driven automated image-based tissue characterization. Atherosclerotic tissue...
Background
Extracorporeal membrane oxygenation (ECMO) via femoral cannulation is a vital intervention capable of rapidly restoring perfusion for patients in shock. Despite increasing use to provide circulatory support, its hemodynamic effects are poorly understood and the impact of patient-specific anatomical variation on perfusion is unknown. This...
The increasing prevalence of finite element (FE) simulations in the study of atherosclerosis has spawned numerous inverse FE methods for the mechanical characterization of diseased tissue in vivo. Current approaches are however limited to either homogenized or simplified material representations. This paper presents a novel method to account for ti...
The introduction of Bioresorbable Vascular Scaffolds (BVS) has revolutionized the treatment of atherosclerosis. InSilc is an in silico clinical trial (ISCT) platform in a Cloud-based environment used for the design, development and evaluation of BVS. Advanced multi-disciplinary and multiscale models are integrated in the platform towards predicting...
Recent concern for local drug delivery and withdrawal of the first Food and Drug Administration-approved bioresorbable scaffold emphasizes the need to optimize the relationships between stent design and drug release with imposed arterial injury and observed pharmacodynamics. In this study, we examine the hypothesis that vascular injury is predictab...
The pathophysiology of atherosclerotic lesions, including plaque rupture triggered by mechanical failure of the vessel wall, depends directly on the plaque morphology-modulated mechanical response. The complex interplay between lesion morphology and structural behaviour can be studied with high-fidelity computational modelling. However, constructio...
Artificial intelligence (AI) offers great promise in cardiology, and medicine broadly, for its ability to tirelessly integrate vast amounts of data. Applications in medical imaging are particularly attractive, as images are a powerful means to convey rich information and are extensively utilized in cardiology practice. Departing from other AI appro...
The bicuspid aortic valve (BAV) is a common and heterogeneous congenital heart abnormality that is often complicated by aortic stenosis. Although initially developed for tricuspid aortic valves (TAV), transcatheter aortic valve replacement (TAVR) devices are increasingly applied to the treatment of BAV stenosis. It is known that patient-device rela...
Conjugated heat transfer and hydraulic performance for nanofluid flow in a rectangular microchannel heat sink with LVGs (longitudinal vortex generators) are numerically investigated using at different ranges of Reynolds numbers. Three-dimensional simulations are performed on a microchannel heated by a constant heat flux with a hydraulic diameter of...
Bioresorbable vascular scaffolds were considered the fourth generation of endovascular implants deemed to revolutionize cardiovascular interventions. Yet, unexpected high risk of scaffold thrombosis and post-procedural myocardial infractions quenched the early enthusiasm and highlighted the gap between benchtop predictions and clinical observations...
Extracorporeal membrane oxygenation (ECMO) is increasingly deployed to provide percutaneous mechanical circulatory support despite incomplete understanding of its complex interactions with the failing heart and its effects on hemodynamics and perfusion. Using an idealized geometry of the aorta and its major branches and a peripherally inserted retu...
In the recent years, Bioresorbable Vascular Scaffolds (BVS) for the treatment of atherosclerosis have been introduced. InSilc is a cloud based in silico clinical trial (ISCT) platform for drug-eluting BVS. The platform integrates multidisciplinary and multiscale models predicting the BVS performance. In this study, we present a use case scenario an...
Background
Mixed valvular disease (MVD), mitral regurgitation (MR) from pre‐existing disease in conjunction with paravalvular leak (PVL) following transcatheter aortic valve replacement (TAVR), is one of the most important stimuli for left ventricle (LV) dysfunction, associated with cardiac mortality. Despite the prevalence of MVD, the quantitative...
BACKGROUND: Computational modeling is revolutionizing device design and evaluation. While great progress has been made in virtual stent angioplasty and computational hemodynamics, drug delivery modeling in patient-specific geometries remains a challenge owing to its inherently-dynamic nature.
METHODS: We developed a drug-delivery computational mod...
Stents have changed medicine and the treatment of obstructive vascular disease. Technology advancement and outcomes of numerous clinical trials have led to development of different generations of stents and other novel endovascular implants. Herewith, we briefly discuss the evolution of coronary intervention from balloon angioplasty to contemporary...
Aortic dissections are challenging for it remains perplexing to determine when surgical, endovascular, or medical therapies are optimal. We studied the effect of the multilayer flow modulator (MFM) device in patients with different forms of type-B aortic dissections. CT scans were performed pre-, immediately post-MFM implantation, and multiple time...
Compliance mismatch between the graft and the host artery of an end-to-side (ETS) arterial bypass graft increases the intramural stress in the ETS graft-artery junction, and thus may compromise its long-term patency. The present study takes into account the effects of collagen fibers to demonstrate how their orientations alter the stresses. The str...
Disrupted flow initiates and aggravates intimal thickening in the end-to-side (ETS) coronary artery bypass grafting (CABG), which may lead to failure. To enhance the post-intervention hemodynamics, the geometry is either optimized or totally reconfigured. Majority of configurations proposed by researchers have not suited CABG surgery, for they enta...
Automated analysis of vascular imaging techniques is limited by the inability to precisely determine arterial borders. Intravascular optical coherence tomography (OCT) offers unprecedented detail of artery wall structure and composition, but does not provide consistent visibility of the outer border of the vessel due to limited penetration depth. E...
Computational cardiology is the scientific field devoted to the development of methodologies that enhance our mechanistic understanding, diagnosis and treatment of cardiovascular disease. In this regard, the field embraces the extraordinary pace of discovery in imaging, computational modeling and cardiovascular informatics at the intersection of at...
Polymeric bioresorbable scaffolds (BRS), at their early stages of invention, were considered as a promising revolution in interventional cardiology. However, they failed dramatically compared to metal stents showing substantially higher incidence of device failure and clinical events, especially thrombosis. One problem is that use of paradigms inhe...
This article studies buoyancy-driven natural convection of a nanofluid affected by a magnetic field within a square enclosure with an individual conductive pin fin. The effects of electromagnetic forces, thermal conductivity, and inclination angle of pin fin were investigated using non-dimensional parameters. An extensive sensitivity analysis was c...
Management of aortic dissections (AD) is still challenging, with no universally-approved guideline among possible surgical, endovascular or medical therapies. Approximately 25% of AD patients suffer post-intervention malperfusion syndrome or hemodynamic instability, with the risk of sudden death if left untreated. Part of the issue is that vascular...
Polymeric endovascular implants are the next step in minimally invasive vascular interventions. As an alternative to traditional metallic drug-eluting stents, these often-erodible scaffolds present opportunities and challenges for patients and clinicians. Theoretically, as they resorb and are absorbed over time, they obviate the long-term complicat...
We present a novel and time-efficient method for intracoronary lumen detection which produces three-dimensional (3D) coronary arteries using Optical Coherence Tomographic (OCT) images. OCT images are acquired for multiple patients and longitudinal cross-section (LOCS) images are reconstructed using different acquisition angles. The lumen contours f...
Bioresorbable vascular scaffolds (BVS), the next step in the continuum of minimally invasive vascular interventions present new opportunities for patients and clinicians but challenges as well. As they are comprised of polymeric materials standard imaging is challenging. This is especially problematic as modalities like optical coherence tomography...
Bioresorbable vascular scaffolds (BVS), the next step in the continuum of minimally invasive vascular interventions present new opportunities for patients and clinicians but challenges as well. As they are comprised of polymeric materials standard imaging is challenging. This is especially problematic as modalities like optical coherence tomography...
Optical coherence tomography (OCT) provides high-resolution cross-sectional images of arterial luminal morphology. Traditionally lumen segmentation of OCT images is performed manually by expert observers; a laborious, time consuming effort, sensitive to inter-observer variability process. Although several automated methods have been developed, the...
OBJECTIVES: To investigate the impact of transcatheter intervention on left ventricular (LV) function and aortic hemodynamics in patients with mild coarctation of the aorta (COA).
BACKGROUND: The optimal method and timing of transcatheter intervention for COA remains unclear, especially when the severity of COA is mild (peak-to-peak trans-coarctati...
Key Points
Cardiovascular innovation, and the coronary stent in particular, has played a key role in advancing our understanding of biocompatibility
Stent biocompatibility is contextual and must be measured relative to clinical performance; what is biocompatible in some settings need not be in others.
Along with biomaterial innovation, advanc...
Drug-eluting stents are accepted as mainstream endovascular therapy, yet concerns for their safety may be under-appreciated. While failure from restenosis has dropped to below 5%, the risk of stent thrombosis and associated mortality remain relatively high. Further optimization of drug release is required to minimize thrombosis risk while maintaini...
Introduction: Coarctation of the aorta (COA) is an obstruction of the aorta distal to the left subclavian artery. A peak-to-peak trans-coarctation pressure gradient (P K dP) of greater than 20 mmHg warns of severe COA and the need for interventional/surgical repair. The optimal method and timing of the intervention remain uncertain especially when...
Nitinol stent oversizing is frequently performed in peripheral arteries to ensure a desirable lumen gain. However, the clinical effect of mis-sizing remains controversial. The goal of this study was to provide a better understanding of the structural and hemodynamic effects of Nitinol stent oversizing. Five patient-specific numerical models of non-...
The interpretation of the function of the ammonoid phragmocone as a buoyancy device is now widely accepted among ammonoid researchers. During the 20th century, several theoretical models were proposed for the role of the chambered shell (phragmocone); accordingly, the phragmocone had hydrostatic properties, which enabled it to attain neutral buoyan...
Introduction: Coarctation of the aorta (COA) is an obstruction of the aorta distal to the left subclavian artery. A peak-to-peak trans-coarctation pressure gradient (PKdP) of greater than 20 mmHg warns of severe COA and the need for interventional/surgical repair. The optimal method and timing of the intervention remain uncertain especially when th...
The aim of this paper is to present the development of a multi-scale and multiphysics approach to tumor growth. An existing biomodel used for clinical tumor growth and response to treatment has been coupled with a biomechanical model. The macroscopic mechanical model is used to provide directions of least pressure in the tissue, which drives the ge...
A key problem in X-ray computed tomography is choosing photon energies for postmortem specimens containing both soft and hard tissues. Increasing X-ray energy reduces image artifacts from highly absorbing hard tissues including plaque, but it simultaneously decreases contrast in soft tissues including the endothelium. Therefore, identifying the lum...
A key problem in X-ray computed tomography is choosing photon energies for postmortem specimens containing both soft and hard tissues. Increasing X-ray energy reduces image artifacts from highly absorbing hard tissues including plaque, but it simultaneously decreases contrast in soft tissues including the endothelium. Therefore, identifying the lum...
Coronary artery stenosis is commonly treated by stent placement via percutaneous intervention, at times requiring multiple stents that may overlap. Stent overlap is associated with increased risk of adverse clinical outcome. While changes in local blood flow are suspected to play a role therein, hemodynamics in arteries with overlapping stents rema...
Background / Purpose:
Coronary artery disease is the main cause of death in the developed world. Although the hemodynamics and shear stress parameters proved to be closely related to the biological cascade of events in atherosclerosis and negative clinical outcomes of conventional treatments, thorough investigations on hemodynamics of stented art...
Hemodynamic factors such as low wall shear stress have been shown to influence endothelial healing and atherogenesis in stent-free vessels. However, in stented vessels, a reliable quantitative analysis of such relations has not been possible due to the lack of a suitable method for the accurate acquisition of blood flow. The objective of this work...
While the correlation of atherosclerotic plaque locations with local wall shear stress magnitude has been evaluated previously by other investigators in both right (RCA) and left coronary arteries (LCA), the relative performance of average wall shear stress (AWSS), average wall shear stress gradient (AWSSG), oscillatory shear index (OSI) and relati...
If the hydrodynamic diameter of a channel is comparable with the mean free path of the gas molecules moving inside the channel, the fluid can no longer be considered to be in thermodynamic equilibrium and a variety of non-continuum or rarefaction effects can occur. To avoid enormous complexity and extensive numerical cost encountered in modeling of...
Questions
Questions (3)
To model the drug transfer from a stent coated with paclitaxel, I am very eager to know whether the paclitaxel released from the stent coating inside the lumen can pass the endothelial barrier. I know that LDL passes only through vesicular pathways and leaky junctions as the endothelial layer blocks any solute with radius bigger than 2nm, and it is not soluble in cell membrane. I want to know if paclitaxel behaves similarly. I could not find any explicit value for bound-free paclitaxel size, and pathways.
This calculation can be done before and after stenting, but what about an already-stented artery without any knowledge of pre-stenting status? Obviously the size of artery is not the same in the proximal and distal side of a single stent. It is also tapering before and after stent tips and the ratio depends on that.
I am interested to segment it (somehow) and get the motion information from an echo of the heart. Any comment also on this part?
