Absolute zero-contrast percutaneous coronary interventions: An intravascular ultrasound-guided case series and literature review

PURPOSE

Contrast media (CM)-associated adverse effects including mainly acute kidney injury and hypersensitivity reactions still remain a significant treatment burden to vulnerable patients requiring percutaneous coronary intervention (PCI). The complete omission of CM administration accompanied by intravascular ultrasound (IVUS) guidance may offer an appropriate revascularization treatment.

METHODS

We hereby present a case series of four patients with challenging coronary lesions and relative/absolute contraindications to CM use [(hypersensitivity reaction owning to CM, history of contrast-induced acute kidney injury, solitary kidney, or advanced chronic kidney disease (CKD)] who underwent absolute zero-contrast IVUS-guided PCI following a predetermined protocol.

RESULTS

The initial diagnostic angiography was reviewed for landmark identification, and multiple guidewires created a metallic road map providing additional landmarks and protected side branches. IVUS imaging was performed to determine lesion length, reference segments and landing zones, assess stent expansion/apposition and identify major complications. All procedures were successfully completed without any CM administration, renal function deterioration, pericardial effusion, or stent edge dissection.

CONCLUSIONS

We demonstrated the feasibility of absolute zero-contrast IVUS-guided PCI in patients with complex coronary lesions susceptible to CM-associated adverse effects. Since the safety of this strategy is well-documented in patients with CKD and challenging lesions morphology even in acute settings, evidence-based validation of this approach is capable of changing the otherwise conservative treatment of vulnerable patients where even minimum doses of CM may have detrimental effects.

SUMMARY FOR THE ANNOTATED TABLE OF CONTENTS

Patients with vulnerable renal function as well as former hypersensitivity reaction to contrast media encounter a significant treatment burden regarding coronary artery disease. Zero-contrast IVUS-guided strategy based on a predetermined protocol provides a feasible alternative approach in patients susceptible to contrast media-associated adverse effects even in the presence of complex coronary lesions.

Virtual Hemodynamic Assessment of Coronary Lesions: The Advent of Functional Angiography and Coronary Imaging

The fractional flow reserve (FFR) is well recognized as a gold standard measure for the estimation of functional coronary stenosis. Technological progressions in image processing have empowered the reconstruction of three-dimensional models of the coronary arteries via both non-invasive and invasive imaging modalities. The application of computational fluid dynamics (CFD) techniques to coronary 3D anatomical models allows the virtual evaluation of the hemodynamic significance of a coronary lesion with high diagnostic accuracy.

METHODS

Search of the bibliographic database for articles published from 2011 to 2023 using the following search terms: invasive FFR and non-invasive FFR. Pooled analysis of the sensitivity and specificity, with the corresponding confidence intervals from 32% to 94%. In addition, the summary processing times were determined.

RESULTS

In total, 24 studies published between 2011 and 2023 were included, with a total of 13,591 patients and 3345 vessels. The diagnostic accuracy of the invasive and non-invasive techniques at the per-patient level was 89% (95% CI, 85-92%) and 76% (95% CI, 61-80%), respectively, while on the per-vessel basis, it was 92% (95% CI, 82-88%) and 81% (95% CI, 75-87%), respectively.

CONCLUSION

These opportunities providing hemodynamic information based on anatomy have given rise to a new era of functional angiography and coronary imaging. However, further validations are needed to overcome several scientific and computational challenges before these methods are applied in everyday clinical practice.

Role of FGF21 and Leptin for the Diagnosis of Metabolic Health in Children with and without Obesity

Obesity and unfavorable metabolic profiles increase the risk for cardiovascular complications in adults. Although it is important to distinguish different metabolic health states at an early stage, there are limited data on the related value of biomarkers in childhood. We aimed to identify biomarkers for the detection of different metabolic health states in children with and without obesity. The serum levels of metabolic regulators (fibroblast growth factor 21 [FGF21], leptin, adiponectin and insulin-like growth factor binding protein 1) and vascular indices (flow-mediated dilation [FMD] and carotid intima-media thickness) were assessed in 78 children. Differences between the metabolically healthy and unhealthy state within children with normal weight (MHN vs. MUN), and within children with overweight/obesity (MHO vs. MUO) were investigated; the discriminatory power of the biomarkers was studied. Both MUN and MUO groups expressed altered lipid and glucose homeostasis compared to their healthy counterparts. The metabolic unhealthy state in children with normal weight was linked to higher FGF21 levels which had good discriminatory ability (area under the curve [AUC]: 0.71, 95% CI: 0.54-0.88; p = 0.044). In overweight/obese children, leptin was increased in the metabolically unhealthy subgroup (AUC: 0.81, 95% CI: 0.68-0.95; p = 0.01). There was a decrease in FMD indicating worse endothelial function in overweight/obese children versus those with normal weight. Distinct states of metabolic health exist in both children with normal weight and overweight/obese children. FGF21 and leptin may help to identify the metabolic unhealthy state in children with normal weight and in overweight/obese children, respectively, early in life.

The role of endothelial shear stress, shear stress gradient, and plaque topography in plaque erosion

BACKGROUND AND AIMS

Plaque erosion is a common underlying cause of acute coronary syndromes. The role of endothelial shear stress (ESS) and endothelial shear stress gradient (ESSG) in plaque erosion remains unknown. We aimed to determine the role of ESS metrics and maximum plaque slope steepness in plaques with erosion versus stable plaques.

METHODS

This analysis included 46 patients/plaques from TOTAL and COMPLETE trials and Brigham and Women's Hospital's database who underwent angiography and OCT. Plaques were divided into those with erosion (n = 24) and matched stable coronary plaques (n = 22). Angiographic views were used to generate a 3-D arterial reconstruction, with centerlines merged from angiography and OCT pullback. Local ESS metrics were assessed by computational fluid dynamics. Among plaque erosions, the up- and down-slope (Δ lumen area/frame) was calculated for each culprit plaque.

RESULTS

Compared with stable plaque controls, plaques with an erosion were associated with higher max ESS (8.3 ± 4.8 vs. 5.0 ± 1.9 Pa, p = 0.02) and max ESSG any direction (9.2 ± 7.5 vs. 4.3 ± 3.11 Pa/mm, p = 0.005). Proximal erosion was associated with a steeper plaque upslope while distal erosion with a steeper plaque downslope. Max ESS and Max ESSG any direction were independent factors in the development of plaque erosion (OR 1.32, 95%CI 1.06-1.65, p = 0.014; OR 1.22, 95% CI 1.03-1.45, p = 0.009, respectively).

CONCLUSIONS

In plaques with similar luminal stenosis, plaque erosion was strongly associated with higher ESS, ESS gradients, and plaque slope as compared with stable plaques. These data support that ESS and slope metrics play a key role in the development of plaque erosion and may help prognosticate individual plaques at risk for future erosion.

Preventing and Managing Radial Artery Occlusion following Transradial Procedures: Strategies and Considerations

Τransradial artery access has recently gained widespread acceptance as the preferred approach for coronary angiography and interventions, due to its lower incidence of bleeding and vascular complications compared to transfemoral access. However, thrombotic occlusion of the radial artery has emerged as the most common complication of this method, impeding its use in future interventions, and in the creation of arteriovenous fistulae for hemodialysis patients, or as a graft for coronary artery bypasses grafting. In this comprehensive review, we delve into the anatomy of the radial artery, the pathophysiology and diagnosis of radial artery occlusion, the identification of potential risk factors and, finally, prevention and treatment strategies. We acknowledge that distal transradial access provides an effective alternative for coronary angiography and catheterizations, with a reduced incidence of radial artery occlusion.

Current Toolset in Predicting Acute Coronary Thrombotic Events: The “Vulnerable Plaque” in a “Vulnerable Patient” Concept

Despite major advances in pharmacotherapy and interventional procedures, coronary artery disease (CAD) remains a principal cause of morbidity and mortality worldwide. Invasive coronary imaging along with the computation of hemodynamic forces, primarily endothelial shear stress and plaque structural stress, have enabled a comprehensive identification of atherosclerotic plaque components, providing a unique insight into the understanding of plaque vulnerability and progression, which may help guide patient treatment. However, the invasive-only approach to CAD has failed to show high predictive value. Meanwhile, it is becoming increasingly evident that along with the “vulnerable plaque”, the presence of a “vulnerable patient” state is also necessary to precipitate an acute coronary thrombotic event. Non-invasive imaging techniques have also evolved, providing new opportunities for the identification of high-risk plaques, the study of atherosclerosis in asymptomatic individuals, and general population screening. Additionally, risk stratification scores, circulating biomarkers, immunology, and genetics also complete the armamentarium of a broader “vulnerable plaque and patient” concept approach. In the current review article, the invasive and non-invasive modalities used for the detection of high-risk plaques in patients with CAD are summarized and critically appraised. The challenges of the vulnerable plaque concept are also discussed, highlighting the need to shift towards a more interdisciplinary approach that can identify the “vulnerable plaque” in a “vulnerable patient”.

Cerebro-/Cardiovascular Collateral Damage During the COVID-19 Pandemic: Fact or Fiction?

Numerous observational studies have identified a decline in cerebro-/cardiovascular (CV) admissions during the initial phase of the COVID-19 pandemic. Recent studies and meta-analyses indicated that the overall decrease was smaller than that found in initial studies during the first months of 2020. Two years later we still do not have clear evidence about the potential causes and impacts of the reduction of CV hospitalizations during the COVID-19 pandemic. It has becoming increasingly evident that collateral damage (i.e., incidental damage to the public and patients) from the COVID-19 outbreak is the main underlying cause that at least somewhat reflects the effects of imposed measures such as social distancing and self-isolation. However, a smaller true decline in CV events in the community due to a lack of triggers associated with such acute syndromes cannot be excluded. There is currently indirect epidemiological evidence about the immediate impact that the collateral damage had on excess mortality, but possible late consequences including a rebound increase in CV events are yet to be observed. In the present narrative review, we present the reporting milestones in the literature of the rates of CV admissions and collateral damage during the last 2 years, and discuss all possible factors contributing to the decline in CV hospitalizations during the COVID-19 pandemic. Healthcare systems need to be prepared so that they can cope with the increased hospitalization rates for CV events in the near future.

Optical coherence tomography in coronary atherosclerosis assessment and intervention

Since optical coherence tomography (OCT) was first performed in humans two decades ago, this imaging modality has been widely adopted in research on coronary atherosclerosis and adopted clinically for the optimization of percutaneous coronary intervention. In the past 10 years, substantial advances have been made in the understanding of in vivo vascular biology using OCT. Identification by OCT of culprit plaque pathology could potentially lead to a major shift in the management of patients with acute coronary syndromes. Detection by OCT of healed coronary plaque has been important in our understanding of the mechanisms involved in plaque destabilization and healing with the rapid progression of atherosclerosis. Accurate detection by OCT of sequelae from percutaneous coronary interventions that might be missed by angiography could improve clinical outcomes. In addition, OCT has become an essential diagnostic modality for myocardial infarction with non-obstructive coronary arteries. Insight into neoatherosclerosis from OCT could improve our understanding of the mechanisms of very late stent thrombosis. The appropriate use of OCT depends on accurate interpretation and understanding of the clinical significance of OCT findings. In this Review, we summarize the state of the art in cardiac OCT and facilitate the uniform use of this modality in coronary atherosclerosis. Contributions have been made by clinicians and investigators worldwide with extensive experience in OCT, with the aim that this document will serve as a standard reference for future research and clinical application.

Sex-related differences in plaque characteristics and endothelial shear stress related plaque-progression in human coronary arteries

BACKGROUND AND AIMS

Clinical atherosclerosis manifestations are different in women compared to men. Since endothelial shear stress (ESS) is known to play a critical role in coronary atherosclerosis development, we investigated differences in anatomical characteristics and endothelial shear stress (ESS)-related plaque growth in human coronary arteries in men compared to women.

METHODS

1183 coronary arteries (male/female: 944/239) from the PREDICTION study were studied for differences in artery/plaque and ESS characteristics, and ESS-related plaque progression (6-10 months follow-up) among men and women and after stratification for age. All characteristics were derived from IVUS-based vascular profiling and reported per 3 mm-segments (13,030 3-mm-segments (male/female: 10,465/2,565)).

RESULTS

Coronary arteries and plaques were significantly smaller in females compared to males; but no important differences were observed in plaque burden, ESS and rate of plaque progression. Change in plaque burden was inversely related to ESS (p<0.001) with no difference between women versus men (β: -0.62 ± 0.13 vs -0.68 ± 0.05, p=0.62). However, stratification for age demonstrated that ESS-related plaque growth was more marked in young women compared to men (<55 years, β: -2.02 ± 0.61 vs -0.33 ± 0.10, p=0.007), reducing in magnitude over the age-categories up till 75 years.

CONCLUSIONS

Coronary artery and plaque size are smaller in women compared to men, but ESS and ESS- related plaque progression were similar. Sex-related differences in ESS-related plaque growth were evident after stratification for age. These observations suggest that although the fundamental processes of atherosclerosis progression are similar in men versus women, plaque progression may be influenced by age within gender.

Association of fibroblast growth factor 21 with metabolic syndrome and endothelial function in children: a prospective cross-sectional study on novel biomarkers

PURPOSE

Metabolic and cardiovascular disease prevention starting in childhood is critical for reducing morbidity later in life. In the present study, the association of novel biomarkers with metabolic syndrome (MS) and vascular function/structure indices of early atherosclerosis in children was investigated.

METHODS

This was a prospective study of 78 children (8-16 years of age) grouped based on the presence or absence of MS. The serum biomarkers investigated included fibroblast growth factor 21 (FGF21), leptin, adiponectin, and insulinlike growth factor binding protein-1 (IGFBP1). Endothelial function and carotid atherosclerosis were assessed based on brachial artery flow-mediated dilation (FMD) and carotid intima-media thickness, respectively.

RESULTS

Children with MS (n=12) had higher levels of FGF21 (median [interquartile range]: 128 [76-189] pg/mL vs. 60 [20-98] pg/mL, P=0.003) and leptin (18.1 [11-34.8] pg/mL vs. 7.5 [1.9-16.5] ng/mL, P=0.003), and lower levels of IGFBP1 (1.5 [1.2-2.1] ng/mL vs. 2.3 [1.5-6] ng/mL, P=0.028) compared with children without MS. FMD inversely correlated with FGF21 (Spearman rho= -0.24, P=0.035) and leptin (rho= -0.24, P=0.002) in all children. The best cutoff value of FGF21 levels for MS diagnosis was above 121.3 pg/mL (sensitivity/specificity, 58/86%). Only FGF21 was significantly associated with the presence of MS after adjustment for body mass index, age, and sex (odds ratio per 10 pg/mL increase: 1.10 [95% confidence interval, 1.01-1.22]; P=0.043).

CONCLUSION

Increased FGF21 levels were associated with the presence of MS and worse endothelial function in children. Larger studies are needed to evaluate the potential value of FGF21 as a biomarker that could predict future metabolic/cardiovascular disease at an early stage.

Elderly patients with non-cardiac admissions and elevated high-sensitivity troponin: the prognostic value of renal function

BACKGROUND

High-sensitivity cardiac troponin (hs-cTn) levels are frequently elevated in elderly patients presenting to the emergency department for non-cardiac events. However, most studies on the role of elevated hs-cTn in elderly populations have investigated the prognostic value of hs-cTn in patients with a specific diagnosis or have assessed the relationship between hs-cTn and comorbidities.

AIM

To investigate the in-hospital prognosis of consecutive elderly patients admitted to the Internal Medicine Department with acute non-cardiac events and increased hs-cTnI levels.

METHODS

In this retrospective study, we selected patients who were aged ≥ 65 years and admitted to the Internal Medicine Department of our hospital between January 2019 and December 2019 for non-cardiac reasons. Eligible patients were those who had hs-cTnI concentrations ≥ 100 ng/L. We investigated the independent predictors of in-hospital mortality by multivariable logistic regression analysis.

RESULTS

One hundred and forty-six patients (59% female) were selected with an age range from 65 to 100 (mean ± SD: 85.4 ± 7.61) years. The median hs-cTnI value was 284.2 ng/L. For 72 (49%) patients the diagnosis of hospitalization was an infectious disease. The overall in-hospital mortality was 32% (47 patients). Individuals who died did not have higher hs-cTnI levels compared with those who were discharged alive (median: 314.8 vs 282.5 ng/L; P = 0.565). There was no difference in mortality in patients with infectious vs non-infectious disease (29% vs 35%). Multivariable analysis showed that age (OR 1.062 per 1 year increase, 95%CI: 1.000-1.127; P = 0.048) and creatinine levels (OR 2.065 per 1 mg/dL increase, 95%CI: 1.383-3.085; P < 0.001) were the only independent predictors of death. Mortality was 49% in patients with eGFR < 30 mL/min/1.73 m².

CONCLUSION

Myocardial injury is a malignant condition in elderly patients admitted to the hospital for non-cardiac reasons. The presence of severe renal impairment is a marker of extremely high in-hospital mortality.

Exercise-mediated adaptations in vascular function and structure: Beneficial effects in coronary artery disease

Exercise exerts direct effects on the vasculature via the impact of hemodynamic forces on the endothelium, thereby leading to functional and structural adaptations that lower cardiovascular risk. The patterns of blood flow and endothelial shear stress during exercise lead to atheroprotective hemodynamic stimuli on the endothelium and contribute to adaptations in vascular function and structure. The structural adaptations observed in arterial lumen dimensions after prolonged exercise supplant the need for acute functional vasodilatation in case of an increase in endothelial shear stress due to repeated exercise bouts. In contrast, wall thickness is affected by rather systemic factors, such as transmural pressure modulated during exercise by generalized changes in blood pressure. Several mechanisms have been proposed to explain the exercise-induced benefits in patients with coronary artery disease (CAD). They include decreased progression of coronary plaques in CAD, recruitment of collaterals, enhanced blood rheological properties, improvement of vascular smooth muscle cell and endothelial function, and coronary blood flow. This review describes how exercise via alterations in hemodynamic factors influences vascular function and structure which contributes to cardiovascular risk reduction, and highlights which mechanisms are involved in the positive effects of exercise on CAD.

SmartFFR, a New Functional Index of Coronary Stenosis: Comparison With Invasive FFR Data

Aims: In this study, we evaluate the efficacy of SmartFFR, a new functional index of coronary stenosis severity compared with gold standard invasive measurement of fractional flow reserve (FFR). We also assess the influence of the type of simulation employed on smartFFR (i.e. Fluid Structure Interaction vs. rigid wall assumption). Methods and Results: In a dataset of 167 patients undergoing either computed tomography coronary angiography (CTCA) and invasive coronary angiography or only invasive coronary angiography (ICA), as well as invasive FFR measurement, SmartFFR was computed after the 3D reconstruction of the vessels of interest and the subsequent blood flow simulations. 202 vessels were analyzed with a mean total computational time of seven minutes. SmartFFR was used to process all models reconstructed by either method. The mean FFR value of the examined dataset was 0.846 ± 0.089 with 95% CI for the mean of 0.833-0.858, whereas the mean SmartFFR value was 0.853 ± 0.095 with 95% CI for the mean of 0.84-0.866. SmartFFR was significantly correlated with invasive FFR values (R_CCTA = 0.86, p _CCTA < 0.0001, R_ICA = 0.84, p _ICA < 0.0001, R _overall = 0.833, p _overall < 0.0001), showing good agreement as depicted by the Bland-Altman method of analysis. The optimal SmartFFR threshold to diagnose ischemia was ≤0.83 for the overall dataset, ≤0.83 for the CTCA-derived dataset and ≤0.81 for the ICA-derived dataset, as defined by a ROC analysis (AUC_overall = 0.956, p < 0.001, AUC_ICA = 0.975, p < 0.001, AUC_CCTA = 0.952, p < 0.001). Conclusion: SmartFFR is a fast and accurate on-site index of hemodynamic significance of coronary stenosis both at single coronary segment and at two or more branches level simultaneously, which can be applied to all CTCA or ICA sequences of acceptable quality.

Spatial relationships among hemodynamic, anatomic, and biochemical plaque characteristics in patients with coronary artery disease

BACKGROUND AND AIMS

We aimed to characterize the spatial proximity of plaque destabilizing features local endothelial shear stress (ESS), minimal luminal area (MLA), plaque burden (PB), and near-infrared spectroscopy (NIRS) lipid signal in high- vs. low-risk plaques.

METHODS

Coronary arteries imaged with angiography and NIRS-intravascular ultrasound (IVUS) underwent 3D reconstruction and computational fluid dynamics calculations of local ESS. ESS, PB, MLA, and lipid core burden index (LCBI), for each 3-mm arterial segment were obtained in arteries with large lipid-rich plaque (LRP) vs. arteries with smaller LRP. The locations of the MLA, minimum ESS (minESS), maximum ESS (maxESS), maximum PB (maxPB), and maximum LCBI in a 4-mm segment (maxLCBI_4mm) were determined along the length of each plaque.

RESULTS

The spatial distributions of minESS, maxESS, maxPB, and maxLCBI_4mm, in reference to the MLA, were significantly heterogeneous within and between each variable. The location of maxLCBI_4mm was spatially discordant from sites of the MLA (p<0.0001), minESS (p = 0.003), and maxESS (p = 0.003) in arteries with large LRP (maxLCBI_4mm ≥ 400) and non-large LRP. Large LRP arteries had higher maxESS (9.31 ± 4.78 vs. 6.32 ± 5.54 Pa; p = 0.023), lower minESS (0.41 ± 0.16 vs. 0.61 ± 0.26 Pa; p = 0.007), smaller MLA (3.54 ± 1.22 vs. 5.14 ± 2.65 mm²; p = 0.002), and larger maxPB (70.64 ± 9.95% vs. 56.70 ± 13.34%, p<0.001) compared with non-large LRP arteries.

CONCLUSIONS

There is significant spatial heterogeneity of destabilizing plaque features along the course of both large and non-large LRPs. Large LRPs exhibit significantly more abnormal destabilizing plaque features than non-large LRPs. Prospective, longitudinal studies are required to determine which patterns of heterogeneous destabilizing features act synergistically to cause plaque destabilization.

"Missing" acute coronary syndrome hospitalizations during the COVID-19 era in Greece: Medical care avoidance combined with a true reduction in incidence?

Background

Reports from countries severely hit by the COVID‐19 pandemic suggest a decline in acute coronary syndrome (ACS)‐related hospitalizations. The generalizability of this observation on ACS admissions and possible related causes in countries with low COVID‐19 incidence are not known.

Hypothesis

ACS admissions were reduced in a country spared by COVID‐19.

Methods

We conducted a nationwide study on the incidence rates of ACS‐related admissions during a 6‐week period of the COVID‐19 outbreak and the corresponding control period in 2019 in Greece, a country with strict social measures, low COVID‐19 incidence, and no excess in mortality.

Results

ACS admissions in the COVID‐19 (n = 771) compared with the control (n = 1077) period were reduced overall (incidence rate ratio [IRR]: 0.72, P < .001) and for each ACS type (ST‐segment elevation myocardial infarction [STEMI]: IRR: 0.76, P = .001; non‐STEMI: IRR: 0.74, P < .001; and unstable angina [UA]: IRR: 0.63, P = .002). The decrease in STEMI admissions was stable throughout the COVID‐19 period (temporal correlation; R² = 0.11, P = .53), whereas there was a gradual decline in non‐STEMI/UA admissions (R² = 0.75, P = .026) following the progressively stricter social measures. During the COVID‐19 period, patients admitted with ACS presented more frequently with left ventricular systolic impairment (22.2 vs 15.5% control period; P < .001).

Conclusions

We observed a reduction in ACS hospitalizations during the COVID‐19 outbreak in a country with strict social measures, low community transmission, and no excess in mortality. Medical care avoidance behavior is an important factor for these observations, while a true reduction of the ACS incidence due to self‐isolation/quarantining may have also played a role.

Simultaneous Transcatheter Aortic Valve Implantation and Infrarenal Aortic Aneurysm Repair for Severe Aortic Stenosis and Abdominal Aortic Aneurysm: Report of 2 Cases and Literature Review

The prevalence of concomitant abdominal aortic aneurysm (AAA) and severe aortic stenosis (AS) has been increasing in the elderly population. Both conditions have adverse outcomes, if not adequately managed. No clear recommendations are available in the literature until today, in regards of the management sequence making thus the decision-making challenging. We report 2 cases of AAA and significant AS treated with endovascular aortic repair (EVAR) and transcatheter aortic valve implantation (TAVI) during the same procedure and a review of the literature on this topic. Based on our experience, the combined procedure with TAVI followed by EVAR seems to be feasible, safe, and effective while detailed preoperative planning and a carefully tailored management strategy by a multidisciplinary team are essential.

Characterization of functionally significant coronary artery disease by a coronary computed tomography angiography-based index: a comparison with positron emission tomography

Aims

To test the hypothesis that virtual functional assessment index (vFAI) is related with regional flow parameters derived by quantitative positron emission tomography (PET) and can be used to assess abnormal vasodilating capability in coronary vessels with stenotic lesions at coronary computed tomography angiography (CCTA).

Methods and results

vFAI, stress myocardial blood flow (MBF), and myocardial flow reserve (MFR) were assessed in 78 patients (mean age 62.2 ± 7.7 years) with intermediate pre-test likelihood of coronary artery disease (CAD). Coronary stenoses ≥50% were considered angiographically significant. PET was considered positive for significant CAD, when more than one contiguous segments showed stress MBF ≤2.3 mL/g/min for 15O-water or <1.79 mL/g/min for 13N-ammonia. MFR thresholds were ≤2.5 and ≤2.0, respectively. vFAI was lower in vessels with abnormal stress MBF (0.76 ± 0.10 vs. 0.89 ± 0.07, P < 0.001) or MFR (0.80 ± 0.10 vs. 0.89 ± 0.07, P < 0.001). vFAI had an accuracy of 78.6% and 75% in unmasking abnormal stress MBF and MFR in 15O-water and 82.7% and 71.2% in 13N-ammonia studies, respectively. Addition of vFAI to anatomical CCTA data increased the ability for predicting abnormal stress MBF and MFR in 15O-water studies [AUCccta + vfai = 0.866, 95% confidence interval (CI) 0.783–0.949; P = 0.013 and AUCccta + vfai = 0.737, 95% CI 0.648–0.825; P = 0.007, respectively]. An incremental value was also demonstrated for prediction of stress MBF (AUCccta + vfai = 0.887, 95% CI 0.799–0.974; P = 0.001) in 13N-ammonia studies. A similar trend was recorded for MFR (AUCccta + vfai = 0.780, 95% CI 0.632–0.929; P = 0.13).

Conclusion

vFAI identifies accurately the presence of impaired vasodilating capability. In combination with anatomical data, vFAI enhances the diagnostic performance of CCTA.

Association between fractional flow reserve, instantaneous wave-free ratio and dobutamine stress echocardiography in patients with stable coronary artery disease

AIMS

The association between fractional flow reserve (FFR) and dobutamine stress echocardiography (DSE) in real-world stable angina patients is scant and controversial whereas no such comparison exists with instantaneous wave-free ratio (iFR). The current retrospective study aimed to investigate the associations among these modalities in patients with stable coronary artery disease (CAD) and intermediate coronary lesions.

METHODS AND RESULTS

We studied 62 consecutive stable angina patients who underwent DSE and subsequently coronary angiography with FFR (in all 62) and iFR (in 46/62 patients) assessment of intermediate single-vessel lesions between 2014 and 2015. Using receiver operating characteristic (ROC) curves we sought to identify the optimal FFR and iFR cut-off points with the highest discriminative power to predict the DSE result. The kappa coefficient was used to assess the agreement between FFR, iFR and DSE. The mean age of the study cohort was 63.5±12 years and 35 (56.5%) were males. Thirteen (21%) lesions were adjudicated as causing reversible ischaemia on DSE. Using ROC (FFR predicting DSE result), the area under the curve was 0.952 (95% CI: 0.902 to 1), whereas for iFR it was 0.743 (95% CI: 0.560 to 0.927), pAUC comparison=0.03. The optimal FFR cut-off point predicting positive DSE was 0.80. There was strong agreement between DSE and FFR (kappa 0.682, p<0.001). There was only modest agreement between iFR and DSE (kappa 0.258, p=0.068) using a cut-off value of 0.9.

CONCLUSIONS

In patients referred for evaluation of stable CAD, there was good agreement between DSE and FFR (87%) but less so with iFR (71.7%).

Art care: A multi-modality coronary 3D reconstruction and hemodynamic status assessment software

BACKGROUND

Due to the incremental increase of clinical interest in the development of software that allows the 3-dimensional (3D) reconstruction and the functional assessment of the coronary vasculature, several software packages have been developed and are available today.

OBJECTIVE

Taking this into consideration, we have developed an innovative suite of software modules that perform 3D reconstruction of coronary arterial segments using different coronary imaging modalities such as IntraVascular UltraSound (IVUS) and invasive coronary angiography images (ICA), Optical Coherence Tomography (OCT) and ICA images, or plain ICA images and can safely and accurately assess the hemodynamic status of the artery of interest.

METHODS

The user can perform automated or manual segmentation of the IVUS or OCT images, visualize in 3D the reconstructed vessel and export it to formats, which are compatible with other Computer Aided Design (CAD) software systems. We employ finite elements to provide the capability to assess the hemodynamic functionality of the reconstructed vessels by calculating the virtual functional assessment index (vFAI), an index that corresponds and has been shown to correlate well to the actual fractional flow reserve (FFR) value.

RESULTS

All the modules of the proposed system have been thoroughly validated. In brief, the 3D-QCA module, compared to a successful commercial software of the same genre, presented very good correlation using several validation metrics, with a Pearson's correlation coefficient (R) for the calculated volumes, vFAI, length and minimum lumen diameter of 0.99, 0.99, 0.99 and 0.88, respectively. Moreover, the automatic lumen detection modules for IVUS and OCT presented very high accuracy compared to the annotations by medical experts with the Pearson's correlation coefficient reaching the values of 0.94 and 0.99, respectively.

CONCLUSIONS

In this study, we have presented a user-friendly software for the 3D reconstruction of coronary arterial segments and the accurate hemodynamic assessment of the severity of existing stenosis.

Computational estimation of the hemodynamic significance of coronary stenoses in arterial branches deriving from CCTA: A proof-of-concept study

The development of non-invasive methods for the accurate hemodynamic assessment of the coronary vasculature has become a non-trivial matter for the everyday clinical practice. Virtual Functional Assessment Index has already been suggested as a valid alternative to the invasively measured FFR but only on coronary arterial segments. In this work, we propose a novel method for the estimation of the severity of coronary lesions in arterial branches from CCTA derived images. Four left arterial branches were reconstructed in 3D using our in-house developed 3D reconstruction algorithm, and were subjected to computational blood flow simulations for the final calculation of the vFAI through the whole arterial branch. Strong correlation was found (r=0.82) between the two methods. A small relative error of 3.2% and a small trend of overestimation (0.023, SD=0.088) were also observed. All pathological cases presenting ischemia, were correctly discriminated by our method as hemodynamically significant lesions.

Virtual Resting Pd/Pa From Coronary Angiography and Blood Flow Modelling: Diagnostic Performance Against Fractional Flow Reserve

BACKGROUND

Fractional flow reserve (FFR) has been established as a useful diagnostic tool. The distal coronary pressure to aortic pressure (Pd/Pa) ratio at rest is a simpler physiologic index but also requires the use of the pressure wire, whereas recently proposed virtual functional indices derived from coronary imaging require complex blood flow modelling and/or are time-consuming. Our aim was to test the diagnostic performance of virtual resting Pd/Pa using routine angiographic images and a simple flow model.

METHODS

Three-dimensional quantitative coronary angiography (3D-QCA) was performed in 139 vessels (120 patients) with intermediate lesions assessed by FFR. The resting Pd/Pa for each lesion was assessed by computational fluid dynamics.

RESULTS

The discriminatory power of virtual resting Pd/Pa against FFR (reference: ≤0.80) was high (area under the receiver operator characteristic curve [AUC]: 90.5% [95% CI: 85.4-95.6%]). Diagnostic accuracy, sensitivity and specificity for the optimal virtual resting Pd/Pa cut-off (≤0.94) were 84.9%, 90.4% and 81.6%, respectively. Virtual resting Pd/Pa demonstrated superior performance (p<0.001) versus 3D-QCA %area stenosis (AUC: 77.5% [95% CI: 69.8-85.3%]). There was a good correlation between virtual resting Pd/Pa and FFR (r=0.69, p<0.001).

CONCLUSIONS

Virtual resting Pd/Pa using routine angiographic data and a simple flow model provides fast functional assessment of coronary lesions without requiring the pressure-wire and hyperaemia induction. The high diagnostic performance of virtual resting Pd/Pa for predicting FFR shows promise for using this simple/fast virtual index in clinical practice.

Computational estimation of the severity of coronary lesions with intravascular ultrasound images: a pilot study

The fast and accurate hemodynamic functional assessment of the coronary vasculature is of utmost importance in clinical practice due to the fact that Cardiovascular Diseases have become the leading cause of death globally. In this work we propose a novel method that combines two of the most efficient methods of hemodynamic status assessment of coronary arteries, Intravascular UtraSound and virtual Functional Assessment Index, an index that correlates well to the measured Fractional Flow Reserve. One Left Anterior Descending segment was reconstructed both in a straight manner (using only IVUS images) as well as using the actual 3D geometry of the vessel (using IvUS images combined with the respective coronary angiographic images [2]). The generated vFAI values were almost identical (Straight=0.80, 3D=0.79), presenting a relative error of 1.27%, thus proving the efficacy of the proposed method. We also calculated the Endothelial Shear Stress for the two models under rest (i.e. flow rate of 1 ml/s), observing a similar trend throughout the artery, but with a statistically important relative error of 13.49%, as expected.

Natural History of Carotid Atherosclerosis in Relation to the Hemodynamic Environment

Carotid atherosclerosis may lead to devastating clinical outcomes such as stroke. Data on the value of local factors in predicting progression in carotid atherosclerosis are limited. Our aim was to investigate the association of local endothelial shear stress (ESS) and low-density lipoprotein (LDL) accumulation with the natural history of atherosclerotic disease using a series of 3 time points of human magnetic resonance data. Three-dimensional lumen/wall reconstruction was performed in 12 carotids, and blood flow and LDL mass transport modeling were performed. Our results showed that an increase in plaque thickness and a decrease in lumen size were associated with low ESS and high LDL accumulation in the arterial wall. Low ESS (odds ratio [OR]: 2.99; 95% confidence interval [CI]: 2.31-3.88; P < .001 vs higher ESS) and high LDL concentration (OR: 3.26; 95% CI: 2.44-4.36; P < .001 vs higher LDL concentration) were significantly associated with substantial local plaque growth. Low ESS and high LDL accumulation both presented a diagnostic accuracy of 67% for predicting plaque growth regions. Modeling of blood flow and LDL mass transport show promise in predicting progression of carotid atherosclerosis.

Effects of Low Endothelial Shear Stress After Stent Implantation on Subsequent Neointimal Hyperplasia and Clinical Outcomes in Humans

Background

In‐stent hyperplasia (ISH) may develop in regions of low endothelial shear stress (ESS), but the relationship between the magnitude of low ESS, the extent of ISH, and subsequent clinical events has not been investigated.

Methods and Results

We assessed the association of poststent ESS with neointimal ISH and clinical outcomes in patients treated with percutaneous coronary interventions (PCI). Three‐dimensional coronary reconstruction was performed in 374 post‐PCI patients at baseline and 6 to 10 months follow‐up as part of the PREDICTION Study. Each vessel was divided into 1.5‐mm‐long segments, and we calculated the local ESS within each stented segment at baseline. At follow‐up, we assessed ISH and the occurrence of a clinically indicated repeat PCI for in‐stent restenosis. In 246 total stents (54 overlapping), 100 (40.7%) were bare‐metal stents (BMS), 104 (42.3%) sirolimus‐eluting stents, and 42 (17.1%) paclitaxel‐eluting stents. In BMS, low ESS post‐PCI at baseline was independently associated with ISH (β=1.47 mm² per 1‐Pa decrease; 95% CI, 0.38–2.56; P<0.01). ISH was minimal in drug‐eluting stents. During follow‐up, repeat PCI in BMS was performed in 21 stents (8.5%). There was no significant association between post‐PCI ESS and in‐stent restenosis requiring PCI.

Conclusions

Low ESS after BMS implantation is associated with subsequent ISH. ISH is strongly inhibited by drug‐eluting stents. Post‐PCI ESS is not associated with in‐stent restenosis requiring repeat PCI. ESS is an important determinant of ISH in BMS, but ISH of large magnitude to require PCI for in‐stent restenosis is likely attributed to factors other than ESS within the stent.

Atherosclerotic plaque behind the stent changes after bare-metal and drug-eluting stent implantation in humans: Implications for late stent failure?

BACKGROUND AND AIMS

The natural history and the role of atherosclerotic plaque located behind the stent (PBS) are still poorly understood. We evaluated the serial changes in PBS following bare-metal (BMS) compared to first-generation drug-eluting stent (DES) implantation and the impact of these changes on in-stent neointimal hyperplasia (NIH).

METHODS

Three-dimensional coronary reconstruction by angiography and intravascular ultrasound was performed after intervention and at 6-10-month follow-up in 157 patients with 188 lesions treated with BMS (n = 89) and DES (n = 99).

RESULTS

There was a significant decrease in PBS area (-7.2%; p < 0.001) and vessel area (-1.7%; p < 0.001) after BMS and a respective increase in both areas after DES implantation (6.1%; p < 0.001 and 4.1%; p < 0.001, respectively). The decrease in PBS area significantly predicted neointimal area at follow-up after BMS (β: 0.15; 95% confidence interval [CI]: 0.10-0.20, p < 0.001) and DES (β: 0.09; 95% CI: 0.07-0.11; p < 0.001) implantation. The decrease in PBS area was the most powerful predictor of significant NIH after BMS implantation (odds ratio: 1.13; 95% CI: 1.02-1.26; p = 0.02).

CONCLUSIONS

The decrease in PBS area after stent implantation is significantly associated with the magnitude of NIH development at follow-up. This finding raises the possibility of a communication between the lesion within the stent and the underlying native atherosclerotic plaque, and may have important implications regarding the pathobiology of in-stent restenosis and late/very late stent thrombosis.

Anatomically correct three-dimensional coronary artery reconstruction using frequency domain optical coherence tomographic and angiographic data: head-to-head comparison with intravascular ultrasound for endothelial shear stress assessment in humans

AIMS

To develop a methodology that permits accurate 3-dimensional (3D) reconstruction from FD-OCT and angiographic data enabling reliable evaluation of the ESS distribution, and to compare the FD-OCT-derived models against the established models based on angiography/IVUS.

METHODS AND RESULTS

Fifteen patients (17 coronary arteries) who underwent angiography, FD-OCT and IVUS examination during the same procedure were studied. The FD-OCT and IVUS lumen borders were placed onto the 3D luminal centreline derived from angiographic data. Three-dimensional geometry algorithms and anatomical landmarks were used to estimate the orientation of the borders appropriately. ESS was calculated using computational fluid dynamics. In 188 corresponding consecutive 3-mm segments, FD-OCT- and IVUS-derived models were highly correlated for lumen area (r=0.96) and local ESS (r=0.89) measurements. FD-OCT-based 3D reconstructions had a high diagnostic accuracy for detecting regions exposed to proatherogenic low ESS identified on the IVUS-based 3D models, considered as the gold standard (receiver operator characteristic area under the curve: 94.9%).

CONCLUSIONS

FD-OCT-based 3D coronary reconstruction provides anatomically correct models and permits reliable ESS computation. ESS assessment in combination with the superior definition of plaque characteristics by FD-OCT is expected to provide valuable insights into the effect of the haemodynamic environment on the development and destabilisation of high-risk plaques.

Validation study of a 3D-QCA coronary reconstruction method using a hybrid intravascular ultrasound and angiography reconstruction method and patient-specific Fractional Flow Reserve data

The estimation of the severity of coronary lesions is of utmost importance in today's clinical practice, since Cardiovascular diseases often have fatal consequences. The most efficient method to estimate the severity of a lesion is the calculation of the Fractional Flow Reserve. The necessary use of a pressure wire, however, makes this method invasive and strenuous for the patient. In this work, we present a novel 3-Dimensional Quantitative Coronary Analysis coronary reconstruction method and a framework for the computation of the virtual Functional Assessment Index (vFAI). In a dataset of 5 coronary arterial segments, we use the aforementioned method to reconstruct them in 3D, and compare them to the respective 3D models reconstructed from our already validated hybrid IVUS-angiography reconstruction method [2]. The obtained results indicate a high correlation between the two methods in terms of the calculated FFR values, presenting a difference of 3.19% in the worst case scenario. Furthermore, when compared to the actual FFR values that derive from a pressure wire, the differences were statistically insignificant.

A proof-of-concept study for predicting the region of atherosclerotic plaque development based on plaque growth modeling in carotid arteries

In this work, we present a computational model for plaque growth utilizing magnetic resonance data of a patient's carotid artery. More specifically, we model blood flow utilizing the Navier-Stokes equations, as well as LDL and HDL transport using the convection-diffusion equation in the arterial lumen. The accumulated LDL in the arterial wall is oxidized considering the protective effect of HDL. Macrophages recruitment and foam cells formation are the final step of the proposed multi-level modeling approach of the plaque growth. The simulated results of our model are compared with the follow-up MRI findings in 12 months regarding the change to the arterial wall thickness. WSS and LDL may indicate potential regions of plaque growth (R(2)=0.35), but the contribution of foam cells formation, macrophages and oxidized LDL increased the prediction significantly (R(2)=0.75).

Finite element analysis of stent implantation in a three-dimensional reconstructed arterial segment

Endovascular stent deployment is a mechanical procedure used to rehabilitate a diseased arterial segment by restoring blood flow in occluded regions. The success or failure of the stent implantation depends on the stent device and the deployment technique. The optimal stent deployment can be predicted by investigating the factors that influence this minimally invasive procedure. In this study, we propose a methodology which evaluates the alterations in the arterial environment caused by stent deployment. A finite element model of a reconstructed right coronary artery with a stenosis was created based on anatomical information provided by intravascular ultrasound and angiography. The model was used to consider placement and performance after intervention with a commercially available Leader Plus stent. The performance of the stent, within this patient-specific arterial segment is presented, as well as the induced arterial deformation and straightening. The arterial stress distribution is analyzed with respect to possible regions of arterial injury. Our approach can be used to optimize stent deployment and to provide cardiologists with a valuable tool to visually select the position and deploy stents in patient-specific reconstructed arterial segments, thereby enabling new methods for optimal cardiovascular stent positioning.

Fibroblast growth factors in cardiovascular disease: The emerging role of FGF21

Early detection of risk factors for enhanced primary prevention and novel therapies for treating the chronic consequences of cardiovascular disease are of the utmost importance for reducing morbidity. Recently, fibroblast growth factors (FGFs) have been intensively studied as potential new molecules in the prevention and treatment of cardiovascular disease mainly attributable to metabolic effects and angiogenic actions. Members of the endocrine FGF family have been shown to increase metabolic rate, decrease adiposity, and restore glucose homeostasis, suggesting a multiple metabolic role. Serum levels of FGFs have been associated with established cardiovascular risk factors as well as with the severity and extent of coronary artery disease and could be useful for prediction of cardiovascular death. Furthermore, preclinical investigations and clinical trials have tested FGF administration for therapeutic angiogenesis in ischemic vascular disease, demonstrating a potential role in improving angina and limb function. FGF21 has lately emerged as a potent metabolic regulator with multiple effects that ultimately improve the lipoprotein profile. Early studies show that FGF21 is associated with the presence of atherosclerosis and may play a protective role against plaque formation by improving endothelial function. The present review highlights recent investigations suggesting that FGFs, in particular FGF21, may be useful as markers of cardiovascular risk and may also serve as protective/therapeutic agents in cardiovascular disease.

Computational assessment of the fractional flow reserve from intravascular ultrasound and coronary angiography data: a pilot study

Cardiovascular disease is one of the primary causes of morbidity and mortality around the globe. Thus, the diagnosis of critical lesions in coronary arteries is of utmost importance in clinical practice. One useful and efficient method to assess the functional severity of one or multiple lesions in a coronary artery is the calculation of the fractional flow reserve (FFR). In the current work, we present a method which allows the calculation of the FFR value computationally, without the use of a pressure wire and the induction of hyperemia, using intravascular ultrasound (IVUS) and biplane angiography images for three-dimensional (3D) coronary artery reconstruction and measurements of the volumetric flow rate derived from angiographic sequences. The simulated FFR values were compared to the invasively measured FFR values in 7 cases, presenting high correlation (r=0.85) and good agreement (mean difference=0.002). FFR assessment without employing a pressure wire and the induction of hyperemia is feasible using 3D reconstructed coronary artery models from angiographic and IVUS data coupled with computational fluid dynamics.

A new methodology for accurate 3-dimensional coronary artery reconstruction using routine intravascular ultrasound and angiographic data: implications for widespread assessment of endothelial shear stress in humans

AIMS

To develop and validate a new methodology that allows accurate 3-dimensional (3-D) coronary artery reconstruction using standard, simple angiographic and intravascular ultrasound (IVUS) data acquired during routine catheterisation enabling reliable assessment of the endothelial shear stress (ESS) distribution.

METHODS AND RESULTS

Twenty-two patients (22 arteries: 7 LAD; 7 LCx; 8 RCA) who underwent angiography and IVUS examination were included. The acquired data were used for 3-D reconstruction using a conventional method and a new methodology that utilised the luminal 3-D centreline to place the detected IVUS borders and anatomical landmarks to estimate their orientation. The local ESS distribution was assessed by computational fluid dynamics. In corresponding consecutive 3 mm segments, lumen, plaque and ESS measurements in the 3-D models derived by the centreline approach were highly correlated to those derived from the conventional method (r>0.98 for all). The centreline methodology had a 99.5% diagnostic accuracy for identifying segments exposed to low ESS and provided similar estimations to the conventional method for the association between the change in plaque burden and ESS (centreline method: slope= -1.65%/Pa, p=0.078; conventional method: slope= -1.64%/Pa, p=0.084; p =0.69 for difference between the two methodologies).

CONCLUSIONS

The centreline methodology provides geometrically correct models and permits reliable ESS computation. The ability to utilise data acquired during routine coronary angiography and IVUS examination will facilitate clinical investigation of the role of local ESS patterns in the natural history of coronary atherosclerosis.

Effect of the local hemodynamic environment on the de novo development and progression of eccentric coronary atherosclerosis in humans: insights from PREDICTION

BACKGROUND

Eccentric distribution of atheroma has been associated with plaques likely to rupture and cause an acute coronary syndrome, but the factors responsible for the development of eccentricity remain unknown. Endothelial shear stress (ESS) drives plaque formation. We aimed to investigate the role of the local ESS characteristics in the de novo development and progressive worsening of plaque eccentricity in humans.

METHODS

Vascular profiling (3-vessel 3D coronary reconstruction by angiography/intravascular ultrasound, and blood flow simulation for ESS computation) was performed in 374 patients at baseline & 6-10 months follow-up. At baseline, we identified (i) disease-free segments (n=2157), and (ii) diseased regions of luminal obstructions (n=408).

RESULTS

In disease-free regions, baseline low ESS magnitude (p<0.001), marked ESS circumferential heterogeneity (p=0.001), and their interaction (p=0.026) were associated with an increased probability of de novo eccentric plaque formation at follow-up. In diseased regions, baseline low ESS (odds ratio [OR]: 2.33, p=0.003) and large plaque burden (OR: 2.46, p=0.002) were independent predictors of substantially increasing plaque eccentricity index with worsening lumen encroachment. This combined outcome was more frequent in obstructions with both features vs. all others (33 vs. 12%; p<0.001). The incidence of percutaneous coronary intervention in worsening obstructions with increasing plaque eccentricity was higher (13.3 vs. 4.3%, p=0.011).

CONCLUSIONS

The local hemodynamic environment has a critical effect on the development of eccentric coronary plaques at both an early and advanced stage of atherosclerosis. Local ESS assessment could help in predicting sites prone to plaque disruption and acute coronary syndromes in humans.

Assessing the hemodynamic influence between multiple lesions in a realistic right coronary artery segment: A computational study

Coronary artery disease is the primary cause of morbidity and mortality worldwide. Therefore, detailed assessment of lesions in the coronary vasculature is critical in current clinical practice. Fractional flow reserve (FFR) has been proven as an efficient method for assessing the hemodynamic severity of a coronary stenosis. However, functional assessment of a coronary segment with multiple stenoses (≥ 2) remains complex for guiding the strategy of percutaneous coronary intervention due to the hemodynamic interplay between adjacent stenoses. In this work, we created four 3-dimensional (3D) arterial models that derive from a healthy patient-specific right coronary artery segment. The initial healthy model was reconstructed using fusion of intravascular ultrasound (IVUS) and biplane angiographic patient data. The healthy 3D model presented a measured FFR value of 0.96 (pressure-wire) and a simulated FFR value of 0.98. We then created diseased models with two artificial sequential stenoses of 90% lumen area reduction or with the proximal and distal stenosis separately. We calculated the FFR value for each case: 0.65 for the case with the two stenoses, 0.73 for the case with the distal stenosis and 0.90 for the case with the proximal stenosis. This leads to the conclusion that although both stenoses had the same degree of lumen area stenosis, there was a large difference in hemodynamic severity, thereby indicating that angiographic lumen assessment by itself is often not adequate for accurate assessment of coronary lesions.

Endothelial Shear Stress and Coronary Plaque Characteristics in Humans

Background—

Despite the exposure of the entire vasculature to the atherogenic effects of systemic risk factors, atherosclerotic plaques preferentially develop at sites with disturbed flow. This study aimed at exploring in vivo the relationship between local endothelial shear stress (ESS) and coronary plaque characteristics in humans using computational fluid dynamics and frequency-domain optical coherence tomography.

Methods and Results—

Three-dimensional coronary artery reconstruction was performed in 21 patients (24 arteries) presenting with acute coronary syndrome using frequency-domain optical coherence tomography and coronary angiography. Each coronary artery was divided into sequential 3-mm segments and analyzed for the assessment of local ESS and plaque characteristics. A total of 146 nonculprit segments were evaluated. Compared with segments with higher ESS [≥1 Pascal (Pa)], those with low ESS (<1 Pa) showed higher prevalence of lipid-rich plaques (37.5% versus 20.0%; P =0.019) and thin-cap fibroatheroma (12.5% versus 2.0%; P =0.037). Overall, lipid plaques in segments with low ESS had thinner fibrous cap (115 μm [63–166] versus 170 μm [107–219]; P =0.004) and higher macrophage density (normalized standard deviation: 8.4% [4.8–12.6] versus 6.2% [4.2–8.8]; P =0.017). Segments with low ESS showed more superficial calcifications (minimum calcification depth: 93 μm [50–140] versus 152 μm [105–258]; P =0.049) and tended to have higher prevalence of spotty calcifications (26.0% versus 12.0%; P =0.076).

Conclusions—

Coronary regions exposed to low ESS are associated with larger lipid burden, thinner fibrous cap, and higher prevalence of thin-cap fibroatheroma in humans. Frequency-domain optical coherence tomography–based assessment of ESS and wall characteristics may be useful in identifying vulnerable coronary regions.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT01110538.