Limitations of angiography in the assessment of plaque distribution in coronary artery disease: a systematic study of target lesion eccentricity in 1446 lesions

Tandem lesions associate with angiographic progression of coronary artery stenoses

Background

Although the clinical factors associated with progression of coronary artery disease have been well studied, the angiographic predictors are less defined.

Objectives

Our objective was to study the clinical and angiographic factors that associate with progression of coronary artery stenoses.

Methods

We conducted a retrospective analysis of consecutive patients undergoing multiple, clinically indicated invasive coronary angiograms with an interval greater than 6 months, between January 2013 and December 2016. Lesion segments were analysed using Quantitative Coronary Angiography (QCA) if a stenosis ≥ 20 % was identified on either angiogram. Stenosis progression was defined as an increase ≥ 10 % in stenosis severity, with progressor groups analysed on both patient and lesion levels. Mixed-effects regression analyses were performed to evaluate factors associated with progression of individual stenoses.

Results

199 patients were included with 881 lesions analysed. 108 (54.3 %) patients and 186 (21.1 %) stenoses were classified as progressors. The median age was 65 years (IQR 56-73) and the median interval between angiograms was 2.1 years (IQR 1.2-3.0). On a patient level, age, number of lesions and presence of multivessel disease at baseline were each associated with progressor status. On a lesion level, presence of a stenosis downstream (OR 3.07, 95 % CI 2.04-4.63, p < 0.001) and circumflex artery stenosis location (OR 1.81, 95 % CI 1.21-2.7, p = 0.004) were associated with progressor status. Other lesion characteristics did not significantly impact progressor status or change in stenosis severity.

Conclusion

Coronary lesions which have a downstream stenosis may be at increased risk of stenosis progression. Further research into the mechanistic basis of this finding is required, along with its implications for plaque vulnerability and clinical outcomes.

Lesion Eccentricity Plays a Key Role in Determining the Pressure Gradient of Serial Stenotic Lesions: Results from a Computational Hemodynamics Study

PURPOSE

In arterial disease, the presence of two or more serial stenotic lesions is common. For mild lesions, it is difficult to predict whether their combined effect is hemodynamically significant. This study assessed the hemodynamic significance of idealized serial stenotic lesions by simulating their hemodynamic interaction in a computational flow model.

MATERIALS AND METHODS

Flow was simulated with SimVascular software in 34 serial lesions, using moderate (15 mL/s) and high (30 mL/s) flow rates. Combinations of one concentric and two eccentric lesions, all 50% area reduction, were designed with variations in interstenotic distance and in relative direction of eccentricity. Fluid and fluid-structure simulations were performed to quantify the combined pressure gradient.

RESULTS

At a moderate flow rate, the combined pressure gradient of two lesions ranged from 3.8 to 7.7 mmHg, which increased to a range of 12.5-24.3 mmHg for a high flow rate. Eccentricity caused an up to two-fold increase in pressure gradient relative to concentric lesions. At a high flow rate, the combined pressure gradient for serial eccentric lesions often exceeded the sum of the individual lesions. The relative direction of eccentricity altered the pressure gradient by 15-25%. The impact of flow pulsatility and wall deformability was minor.

CONCLUSION

This flow simulation study revealed that lesion eccentricity is an adverse factor in the hemodynamic significance of isolated stenotic lesions and in serial stenotic lesions. Two 50% lesions that are individually non-significant can combine more often than thought to hemodynamic significance in hyperemic conditions.

Automatic assessment of atherosclerotic plaque features by intracoronary imaging: a scoping review

Background

The diagnostic performance and clinical validity of automatic intracoronary imaging (ICI) tools for atherosclerotic plaque assessment have not been systematically investigated so far.

Methods

We performed a scoping review including studies on automatic tools for automatic plaque components assessment by means of optical coherence tomography (OCT) or intravascular imaging (IVUS). We summarized study characteristics and reported the specifics and diagnostic performance of developed tools.

Results

Overall, 42 OCT and 26 IVUS studies fulfilling the eligibility criteria were found, with the majority published in the last 5 years (86% of the OCT and 73% of the IVUS studies). A convolutional neural network deep-learning method was applied in 71% of OCT- and 34% of IVUS-studies. Calcium was the most frequent plaque feature analyzed (26/42 of OCT and 12/26 of IVUS studies), and both modalities showed high discriminatory performance in testing sets [range of area under the curve (AUC): 0.91-0.99 for OCT and 0.89-0.98 for IVUS]. Lipid component was investigated only in OCT studies (n = 26, AUC: 0.82-0.86). Fibrous cap thickness or thin-cap fibroatheroma were mainly investigated in OCT studies (n = 8, AUC: 0.82-0.94). Plaque burden was mainly assessed in IVUS studies (n = 15, testing set AUC reported in one study: 0.70).

Conclusion

A limited number of automatic machine learning-derived tools for ICI analysis is currently available. The majority have been developed for calcium detection for either OCT or IVUS images. The reporting of the development and validation process of automated intracoronary imaging analyses is heterogeneous and lacks critical information.

Systematic Review Registration

Open Science Framework (OSF), https://osf.io/nps2b/.Graphical AbstractCentral Illustration.

Guiding Intervention for Complex Coronary Lesions by Optical Coherence Tomography or Intravascular Ultrasound

BACKGROUND

Optical coherence tomography (OCT) and intravascular ultrasound (IVUS) have shown comparable outcomes in guiding percutaneous coronary intervention (PCI). However, their comparative effectiveness in complex coronary artery lesions remains unclear.

OBJECTIVES

This study compared the effectiveness and safety of OCT-guided vs IVUS-guided PCI for complex coronary artery lesions.

METHODS

This was a prespecified, main subgroup analysis of complex coronary artery lesions in the OCTIVUS (Optical Coherence Tomography Versus Intravascular Ultrasound Guided Percutaneous Coronary Intervention) trial, which included unprotected left main disease, bifurcation disease, an aorto-ostial lesion, a chronic total occlusion, a severely calcified lesion, an in-stent restenotic lesion, a diffuse long lesion, or multivessel PCI. The primary endpoint was a composite of death from cardiac causes, target vessel-related myocardial infarction, or ischemia-driven target vessel revascularization.

RESULTS

In 2,008 randomized patients, 1,475 (73.5%) underwent imaging-guided PCI for complex coronary artery lesions; 719 (48.7%) received OCT-guided and 756 (51.3%) IVUS-guided PCI. At a median follow-up of 2.0 years, primary endpoint event had occurred in 47 patients (6.5%) in the OCT-guided group and in 56 patients (7.4%) in the IVUS-guided group (HR: 0.87; 95% CI: 0.59-1.29; P = 0.50). These findings were consistent in adjusted analyses. The incidence of contrast-induced nephropathy was similar between the 2 groups (1.9% vs 1.5%; P = 0.46). The incidence of major procedural complications was lower in the OCT-guided group than in the IVUS-guided group (1.7% vs 3.4%; P = 0.03).

CONCLUSIONS

Among patients with complex coronary artery lesions, OCT-guided PCI showed a similar risk of primary composite event of death from cardiac causes, target vessel-related myocardial infarction, or target vessel revascularization as compared with IVUS-guided PCI. (Optical Coherence Tomography Versus Intravascular Ultrasound Guided Percutaneous Coronary Intervention [OCTIVUS]; NCT03394079).

Diabetes Mellitus in Acute Coronary Syndrome

The global prevalence of diabetes mellitus (DM) has led to a pandemic, with significant microvascular and macrovascular complications including coronary artery disease (CAD), which worsen clinical outcomes and cardiovascular prognosis. Patients with both acute coronary syndrome (ACS) and DM have worse prognosis and several pathophysiologic mechanisms have been implicated including, insulin resistance, hyperglycemia, endothelial dysfunction, platelet activation and aggregations as well as plaque characteristics and extent of coronary lesions. Therefore, regarding reperfusion strategies in the more complex anatomies coronary artery bypass surgery may be the preferred therapeutic strategy over percutaneous coronary intervention while both hyperglycemia and hypoglycemia should be avoided with closed monitoring of glycemic status during the acute phase of myocardial infraction. However, the best treatment strategy remains undefined. Non-insulin therapies, due to the low risk of hypoglycemia concurrently with the multifactorial CV protective effects, may be proved to be the best treatment option in the future. Nevertheless, evidence for the beneficial effects of glucagon like peptide-1 receptor agonists, dipeptidyl-peptidase 4 inhibitors and sodium glycose cotransporter 2 inhibitors, despite accumulating, is not robust and future randomized control trials may provide more definitive data.

Optical Coherence Tomography-Guided or Intravascular Ultrasound-Guided Percutaneous Coronary Intervention: The OCTIVUS Randomized Clinical Trial

BACKGROUND

Intravascular imaging-guided percutaneous coronary intervention (PCI) with intravascular ultrasound (IVUS) or optical coherence tomography (OCT) showed superior clinical outcomes compared with angiography-guided PCI. However, the comparative effectiveness of OCT-guided and IVUS-guided PCI regarding clinical outcomes is unknown.

METHODS

In this prospective, multicenter, open-label, pragmatic trial, we randomly assigned 2008 patients with significant coronary artery lesions undergoing PCI in a 1:1 ratio to undergo either an OCT-guided or IVUS-guided PCI. The primary end point was a composite of death from cardiac causes, target vessel-related myocardial infarction, or ischemia-driven target-vessel revascularization at 1 year, which was powered for noninferiority of the OCT group compared with the IVUS group. Safety outcomes were also assessed.

RESULTS

At 1 year, primary end point events occurred in 25 of 1005 patients (Kaplan-Meier estimate, 2.5%) in the OCT group and in 31 of 1003 patients (Kaplan-Meier estimate, 3.1%) in the IVUS group (absolute difference, -0.6 percentage points; upper boundary of one-sided 97.5% CI, 0.97 percentage points; P<0.001 for noninferiority). The incidence of contrast-induced nephropathy was similar (14 patients [1.4%] in the OCT group versus 15 patients [1.5%] in the IVUS group; P=0.85). The incidence of major procedural complications was lower in the OCT group than in the IVUS group (22 [2.2%] versus 37 [3.7%]; P=0.047), although imaging procedure-related complications were not observed.

CONCLUSIONS

In patients with significant coronary artery lesions, OCT-guided PCI was noninferior to IVUS-guided PCI with respect to the incidence of a composite of death from cardiac causes, target vessel-related myocardial infarction, or ischemia-driven target-vessel revascularization at 1 year. The selected study population and lower-than-expected event rates should be considered in interpreting the trial.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique number: NCT03394079.

Integration of fractional flow reserve derived from CT into clinical practice

Fractional flow reserve (FFR) is currently considered as the gold standard for revascularization decision-making in patients with stable coronary artery disease (CAD). The application of computational fluid dynamics to coronary computed tomography (CT) angiography (CCTA) enables calculation of FFR without additional testing, radiation exposure, contrast medium injection, and hyperemia (FFR_CT). Although multiple diagnostic and clinical studies have enriched the scientific evidence, it is still challenging to integrate FFR_CT into clinical practice. Both meticulous scientific backgrounds and precise anatomical data derived from CCTA are fundamental for FFR_CT computation, and there are numerous factors impacting on FFR_CT calculation and interpretation: coronary artery stenosis, calcium, atherosclerosis, luminal volume, and left ventricular myocardial mass. Further, there is a gap that clinicians using FFR_CT need to recognize in interpretation of FFR_CT results between diagnostic studies and clinical studies. In this review, we summarize multiple evidence related to FFR_CT computation and interpretation to refine the FFR_CT strategy in patients with stable CAD.

Decision-Making During Percutaneous Coronary Intervention Guided by Optical Coherence Tomography: Insights From the LightLab Initiative

BACKGROUND

Use of intracoronary imaging is associated with improved outcomes in patients undergoing percutaneous coronary intervention (PCI). Yet, the impact of intracoronary imaging on real-time physician decision-making during PCI is not fully known.

METHODS

The LightLab Initiative is a multicenter, prospective, observational study designed to characterize the use of a standardized optical coherence tomography (OCT) workflow during PCI. Participating physicians performed pre-PCI and post-PCI OCT in accordance with this workflow and operator assessments of lesion characteristics and treatment plan were recorded for each lesion based on angiography alone and following OCT. Physicians were categorized as having low (n=15), intermediate (n=13), or high (n=14) OCT use in the year preceding participation.

RESULTS

Among 925 patients with 1328 lesions undergoing PCI, the prescribed OCT workflow was followed in 773 (84%) of patients with 836 lesions. Operator lesion assessment and decision-making during PCI changed with OCT use in 86% (721/836) of lesions. Pre-PCI OCT use changed operator decision-making in 80% of lesions, including lesion assessment (45%), vessel preparation strategy (27%), stent diameter (37%), and stent length (36%). Post-PCI OCT changed stent optimization decision-making in 31% of lesions. These findings were consistent across strata of physician prior OCT experience.

CONCLUSIONS

A standardized OCT workflow impacted PCI decision-making in 86% of lesions, with a predominant effect on pre-PCI lesion assessment and planning of treatment strategy. This finding was consistent regardless of operator experience level and provides insight into mechanisms by which intravascular imaging might improve PCI outcomes.

Investigating real-world impact of optical coherence tomography workflow-guided coronary interventions: Design and rationale of the LightLab Clinical Initiative

OBJECTIVE

The LightLab Clinical Initiative was designed to examine adoption of optical coherence tomography (OCT) imaging during routine percutaneous coronary intervention (PCI) practice, and enable identification and reduction of barriers to broader adoption of intracoronary imaging in real-world practice.

BACKGROUND

Intracoronary imaging guidance during PCI has been shown to improve clinical outcomes and features as a recommendation in societal guidelines, yet widespread routine adoption remains low. Perceived barriers to utilization include familiarity with, and ability to interpret imaging, concerns over added procedure time and contrast load, alongside a lack of actionable outcome data.

METHODS AND RESULTS

LightLab was a multicenter prospective observational data-gathering project, conducted between January 2019, and June 2021, with 17 participating hospitals and physicians. Data were gathered in real-time, where OCT guidance was employed during PCI using a standardized OCT-guided workflow algorithm, MLD MAX (where MLD stands for plaque Morphology, lesion Length, vessel Diameter and MAX for Medial dissection, stent Apposition, stent eXpansion) which was developed to simplify and integrate information from OCT throughout the PCI procedure. Integration of this workflow/algorithm was implemented through a series of phases, focusing on physician decision-making, efficiency, and safety improvements during the procedure.

CONCLUSIONS

Through real-time, prospective procedural data acquisition in the cardiac catheterization laboratory setting, the LightLab Clinical Initiative demonstrates the impact of a standardized OCT-guided workflow on procedural metrics, including time, contrast use, radiation exposure, as well as financial efficiencies such as device utilization. These results can potentially mitigate underlying concerns over the utility of adoption of intracoronary imaging guidance during PCI.

Comparison of Invasive Coronary Angiography Versus Computed Tomography Angiography to Assess Mehran Classification of In-Stent Restenosis in Bifurcation Percutaneous Coronary Intervention

The Mehran classification is used to determine the presence of in-stent restenosis (ISR) and characterization of its subtypes in invasive coronary angiography (ICA). The utility of computed tomography angiography (CTA) for the assessment of Mehran classification is unknown. We aimed to compare the agreement and reproducibility of Mehran classification between ICA and CTA and evaluate the sensitivity and specificity of both imaging methods. Consecutive patients who had ISR on ICA preceded with CTA before intervention were enrolled in our study. Modified Mehran's classification was employed by CTA and ICA to classify ISR into 4 subtypes: focal (type I [A, B, C]), intra-stent (type II [A, B, C]), proliferative (type III [A, B, C]), and total occlusion (type IV). Agreement between ISR classification and main vessel lesion length, reference vessel diameter, and bifurcation angles were compared. A total of 405 patients with 431 bifurcation percutaneous coronary interventions with ISR were included in this investigation. The total agreement between CTA and ICA for assessment of Mehran class was poor (kappa = 0.168). Proliferative ISR (25% vs 10%, p = 0.012) and total occlusions (24% vs 5%, p <0.001) were reclassified more often between ICA and CTA, respectively. CTA assessment of lesion length was significantly longer than that of ICA measurements in all subtypes of ISR (32.15 ± 5.23 vs 27.41 ± 3.63, p = 0.004). Receiver operating characteristic curve expressed CTA to be more sensitive and specific than ICA in diagnosing ISR. In conclusion, Mehran classification was significantly affected by imaging modality, and CTA results were more reproducible than ICA. Therefore, CTA evaluation of ISR may facilitate treatment options and generate a sound plan before the procedure.

Clinical Outcomes and Prevalence of Intravascular Ultrasound Use at a Tertiary Care Hospital in a South Asian Country

Objectives:

Intravascular ultrasound (IVUS) plays a pivotal role in the current era of coronary interventions. We aimed to determine the prevalence of IVUS use and clinical outcomes of IVUS-guided percutaneous treatment of coronary arteries lesions in a South Asian country.

Material and Methods:

It is a retrospective observational study, a total of 134 consecutive patients having done IVUS, was enrolled from January 2013 to March 2020 at a single center.

Results:

Out of 134 patients, 97 (72.4%) were male with a mean age of 63.1 ± 12.9 years. The prevalence of IVUS in our center was 3.0%. The most frequent comorbidity observed was dyslipidemia, n = 111 (82.8%). Non-ST-elevation myocardial infarction, n = 50 (37.3%), was the common mode of presentation. On coronary angiogram, the left main (LM) disease was found in n = 46 (34.3%), however, single-vessel disease, n = 51 (38.1%), was most commonly noted. IVUS utilization was higher in the left anterior descending, n = 94 (70.1%), followed by LM, n = 46 (34.3%). The LM mean minimal luminal area was 6.0 ± 2.6 mm² and minimal luminal diameter was 4.53 mm ± 0.6 (mean). The coronary artery dissection was noted in n = 15 (11.2%). The mean duration of follow-up in our study was 40.3 ± 30.1 months. Major adverse cardiac events (MACEs) were recorded in n = 13 (9.7%), which included heart failure, n = 4 (3%). Cardiovascular death and target vessel revascularization occurred in n = 3 (2.2%).

Conclusion:

IVUS results in a significant decrease in MACE. Our data might support the broader use of IVUS in both developed and in our part of the world.

Predictors and outcomes of acute recoil after ultrathin bioresorbable polymer sirolimus-eluting stents implantation: an intravascular ultrasound in native coronary arteries

BACKGROUND

Ultrathin bioresorbable polymer sirolimus-eluting stents (BP-SESs) may easily lead to acute recoil. This study investigated acute recoil after BP-SES implantation on the basis of intravascular ultrasound (IVUS).

METHODS

We enrolled 40 consecutive stents. Absolute acute recoil by quantitative coronary angiography was defined as the difference between the mean diameter of the last inflated balloon (X) and mean lumen diameter of the BP-SES immediately after balloon deflation (Y). Percent (%) acute recoil was defined as (X-Y)×100/X. IVUS was performed within the culprit lesion. Plaque eccentricity, % plaque burden and calcification grade score were assessed using IVUS. Calcification grade was scored on the basis of quadrants. On the basis of the median acute recoil value of 5.0%, the stents were divided into two groups: low (LAR, n = 20) and high % acute recoil (HAR, n = 20).

RESULTS

Mean % acute recoil was 5.8 ± 5.3%. Plaque eccentricity, % plaque burden and stent/artery ratio were significantly higher in the HAR group than in the LAR group. Significant differences in % acute recoil were not observed regarding the types of stent diameter. In multivariate logistic regression and multiple linear regression analysis, plaque eccentricity and % plaque burden in the culprit plaque were significant positive predictors for the occurrence of % acute recoil. No significant differences, including clinical outcomes, were found between both groups at follow-up.

CONCLUSION

Acute recoil of BP-SESs may be influenced by an eccentric plaque with a large burden, which did not affect long-term outcomes. However, the present study might suggest the proper strategy (e.g. a more exhaustive plaque preparation) before BP-SES implantation in a case with these IVUS characteristics.

Optical Coherence Tomography: Current Applications for the Assessment of Coronary Artery Disease and Guidance of Percutaneous Coronary Interventions

INTRODUCTION

Coronary angiography (CAG) is the standard modality for assessment of coronary stenoses and intraprocedural guidance of percutaneous coronary interventions (PCI). However, the limitations of CAG are well recognized. Intracoronary imaging (ICI) can potentially overcome these limitations. Intravascular ultrasound (IVUS) and optical coherence tomography (OCT) are the main ICI techniques utilized in clinical practice.

AIM

This narrative literature review addresses the current clinical applications of OCT in relation to IVUS and CAG in patients with coronary artery disease (CAD). Items reviewed are: technical implications of OCT and IVUS, lesion characterization and decision-making, stent optimization criteria, post-stenting results, safety in terms of procedural complications, clinical outcomes, and indications.

MAIN FINDINGS

OCT is able to reveal more detail than IVUS due to its higher resolution. However, this higher resolution comes at the cost of a lower penetration depth. Pre-stenting OCT results in procedural change in more than 50% of the cases in terms of stent length and diameter. Post-stenting OCT resulting in stent optimization is reported in at least 27% of the cases. Malapposition and under-expansion are treated with post-dilatations, while edge dissections are treated with additional stent placement. Stent expansion, stent apposition, distal stent edge dissections, and reference lumen areas seem to be the most important stent optimization criteria for both decision-making and for reducing the risk of adverse events during follow-up. Both OCT and IVUS are superior in terms of post-stenting results compared with CAG alone. However, there is no consensus about whether OCT guidance results in better stent expansion than IVUS guidance. OCT, IVUS, and CAG are safe procedures with few reported procedural complications. In general, OCT guidance seems to contribute to favorable clinical outcomes compared with CAG guidance only. However, OCT guidance results in similar clinical outcomes as with IVUS guidance. OCT could be considered for lumen assessment and stent-related morphology in more complex cases in which CAG interpretation remains uncertain. Since OCT and IVUS have distinct characteristics, these techniques are complementary and should be considered carefully for each patient case based on the benefits and limitations of both techniques.

Fundamentals and role of intravascular ultrasound in percutaneous coronary intervention

Intravascular ultrasound (IVUS) is a catheter-based invasive imaging modality that has become an essential adjunctive tool to percutaneous coronary intervention (PCI) over the past 20 years. Clinical applications of IVUS in PCI include assessment of lesion severity, characterizing plaque morphology, optimization of acute stent results and clarification of mechanisms of stent failure. Numerous meta-analyses of large observational and randomized studies support the role of IVUS-guided PCI in reducing short and long-term adverse outcomes, including mortality and stent failure, particularly in patients receiving drug-eluting stents (DESs) and in complex lesion subsets. The current review provides a summary of the fundamental aspects and current clinical roles of IVUS in coronary intervention.

In-vitro and in-vivo imaging of coronary artery stents with Heartbeat OCT

To quantify the impact of cardiac motion on stent length measurements with Optical Coherence Tomography (OCT) and to demonstrate in vivo OCT imaging of implanted stents, without motion artefacts. The study consists of: clinical data evaluation, simulations and in vivo tests. A comparison between OCT-measured and nominal stent lengths in 101 clinically acquired pullbacks was carried out, followed by a simulation of the effect of cardiac motion on stent length measurements, experimentally and computationally. Both a commercial system and a custom OCT, capable of completing a pullback between two consecutive ventricular contractions, were employed. A 13 mm long stent was implanted in the left anterior descending branch of two atherosclerotic swine and imaged with both OCT systems. The analysis of the clinical OCT images yielded an average difference of 1.1 ± 1.6 mm, with a maximum difference of 7.8 mm and the simulations replicated the statistics observed in clinical data. Imaging with the custom OCT, yielded an RMS error of 0.14 mm at 60 BPM with the start of the acquisition synchronized to the cardiac cycle. In vivo imaging with conventional OCT yielded a deviation of 1.2 mm, relative to the length measured on ex-vivo micro-CT, while the length measured in the pullback acquired by the custom OCT differed by 0.20 mm. We demonstrated motion artefact-free OCT-imaging of implanted stents, using ECG triggering and a rapid pullback.

The impact of Objective Mathematical Analysis during Fractional Flow Reserve measurement: results from the OMA-FFR study

AIMS

Fractional flow reserve (FFR), the reference standard for guiding coronary revascularisation, is most commonly acquired during intravenous adenosine infusion. Results may be sensitive to system- and operator-dependent variability in how pressure data are analysed and interpreted. To quantify FFR objectively, we developed a computational protocol to process the recorded pressure signals in a consistent manner. We studied the impact on lesion (re)classification and compared this with the operator-selected FFR obtained during cardiac catheterisation.

METHODS AND RESULTS

The algorithm used a moving average and Fourier transformation to identify the Pd/Pa ratio at its nadir (FFRmin) and during the stable hyperaemic period (FFRstable) in <2 s with 100% repeatability, in 163 coronary stenoses (93 patients). The mean operator-selected FFR (FFRCL) was higher than FFRmin and lower than FFRstable (0.779 vs. 0.762 vs. 0.806, p=<0.01). Compared with FFRmin, FFRstable resulted in 16.5% of all lesions being reclassified, all from significant to non-significant (p<0.01). FFRCL classified lesion significance differently from both FFRstable and FFRmin (11.7% and 6.1% lesions reclassified, respectively, p<0.01).

CONCLUSIONS

Subtle differences in how pressure data are analysed and interpreted by the operator during adenosine infusion result in significant differences in the classification of physiological lesion significance. An algorithmic analysis may be helpful in standardising FFR analysis, providing an objective and repeatable result.

The relationship between segmental wall shear stress and lipid core plaque derived from near-infrared spectroscopy

BACKGROUND AND AIMS

Wall shear stress (WSS) has an important role in the natural history of coronary atherosclerosis. The aim of this study is to investigate the relationship between WSS and the lipid content of atherosclerotic plaques as assessed by near-infrared spectroscopy (NIRS).

METHODS

We performed serial NIRS and intravascular ultrasound (IVUS) upon Doppler coronary flow guidewire of coronary plaques at baseline and after 12-18 months in 28 patients with <30% angiographic stenosis, who presented with coronary artery disease. Segmental WSS, plaque burden and NIRS-derived lipid rich plaque (LRP) were evaluated at both time-points in 482 consecutive 2-mm coronary segments.

RESULTS

Segments with LRP at baseline (n = 106) had a higher average WSS (1.4 ± 0.6 N/m²), compared to those without LRP (n = 376) (1.2 ± 0.6 N/m², p<0.001). In segments without baseline LRP, WSS was higher in those who subsequently developed new LRP (n = 35) than those who did not (n = 341) (1.4 ± 0.8 vs. 1.1 ± 0.6 N/m², p=0.002). Conversely, in segments with baseline LRP, WSS was lower in those who had regression of lipid content (n = 41) than those who did not (n = 65) (1.2 ± 0.4 vs. 1.6 ± 0.7 N/m², p=0.007). Segments with the highest tertile of WSS displayed greater progression of LCBI irrespective of baseline lipid content (p<0.001). Multivariate analysis revealed that baseline WSS (p=0.017), PAV (p<0.001) and LCBI (p<0.001) were all independent predictors of change in LCBI over time.

CONCLUSIONS

Coronary segments with high WSS associate with progression of lipid content over time, which may indicate transformation to a more vulnerable phenotype.

Eye tracking in catheter-based cardiovascular interventions: early results

Visual x-ray image processing (XRIP) represents a fundamental component of catheter-based cardiovascular interventions (CBCVIs). To date, no data are available to define XRIP in this setting. To characterize CBCVI XRIP, we developed a computer-based method allowing continuous temporal–spatial analysis of data recorded by a head-mounted eye-tracking device. Quantitative analysis of gaze duration of an expert operator (EO) revealed that the average time in minutes spent viewing the images on the display screen was 39.5%±13.6% and 41.5%±18.3% of the total recorded time in coronary angiography (CA) and in CA followed by CBCVI, respectively. Qualitative analysis of gaze data of the EO revealed consistent focus on the center point of the screen. Only if suspicious findings were detected did gaze move toward the target. In contrast, a novice operator (NO) observing a subset of cases viewed coronary artery segments separately and sequentially. The developed methodology allows continuous registration and analysis of gaze data for analysis of XRIP strategies of EOs in live-cases scenarios and may assist in the transfer of experts’ reading skills to novices.

Local coronary wall eccentricity and endothelial function are closely related in patients with atherosclerotic coronary artery disease

BACKGROUND

Coronary endothelial function (CEF) in patients with coronary artery disease (CAD) varies among coronary segments in a given patient. Because both coronary vessel wall eccentricity and coronary endothelial dysfunction are predictors of adverse outcomes, we hypothesized that local coronary endothelial dysfunction is associated with local coronary artery eccentricity.

METHODS

We used 3 T coronary CMR to measure CEF as changes in coronary cross-sectional area (CSA) and coronary blood flow (CBF) during isometric handgrip exercise (IHE), a known endothelial-dependent stressor, in 29 patients with known CAD and 16 healthy subjects. Black-blood MRI quantified mean coronary wall thickness (CWT) and coronary eccentricity index (EI) and CEF was determined in the same segments.

RESULTS

IHE-induced changes in CSA and CBF in healthy subjects (10.6 ± 6.6% and 38.3 ± 29%, respectively) were greater than in CAD patients 1.3 ± 7.7% and 6.5 ± 19.6%, respectively, p < 0.001 vs. healthy for both measures), as expected. Mean CWT and EI in healthy subjects (1.1 ± 0.3 mm 1.9 ± 0.5, respectively) were less than those in CAD patients (1.6 ± 0.4 mm, p < 0.0001; and 2.6 ± 0.6, p = 0.006 vs. healthy). In CAD patients, we observed a significant inverse relationship between stress-induced %CSA change and both EI (r = -0.60, p = 0.0002), and CWT (r = -0.54, p = 0.001). Coronary EI was independently and significantly related to %CSA change with IHE even after controlling for mean CWT (adjusted r = -0.69, p = 0.0001). For every unit increase in EI, coronary CSA during IHE is expected to change by -6.7 ± 9.4% (95% confidence interval: -10.3 to -3.0, p = 0.001).

CONCLUSION

There is a significant inverse and independent relationship between coronary endothelial macrovascular function and the degree of local coronary wall eccentricity in CAD patients. Thus anatomic and physiologic indicators of high-risk coronary vascular pathology are closely related. The noninvasive identification of coronary eccentricity and its relationship with underlying coronary endothelial function, a marker of vascular health, may be useful in identifying high-risk patients and culprit lesions.

Optical coherence tomography compared with intravascular ultrasound and with angiography to guide coronary stent implantation (ILUMIEN III: OPTIMIZE PCI): a randomised controlled trial

BACKGROUND

Percutaneous coronary intervention (PCI) is most commonly guided by angiography alone. Intravascular ultrasound (IVUS) guidance has been shown to reduce major adverse cardiovascular events (MACE) after PCI, principally by resulting in a larger postprocedure lumen than with angiographic guidance. Optical coherence tomography (OCT) provides higher resolution imaging than does IVUS, although findings from some studies suggest that it might lead to smaller luminal diameters after stent implantation. We sought to establish whether or not a novel OCT-based stent sizing strategy would result in a minimum stent area similar to or better than that achieved with IVUS guidance and better than that achieved with angiography guidance alone.

METHODS

In this randomised controlled trial, we recruited patients aged 18 years or older undergoing PCI from 29 hospitals in eight countries. Eligible patients had one or more target lesions located in a native coronary artery with a visually estimated reference vessel diameter of 2·25-3·50 mm and a length of less than 40 mm. We excluded patients with left main or ostial right coronary artery stenoses, bypass graft stenoses, chronic total occlusions, planned two-stent bifurcations, and in-stent restenosis. Participants were randomly assigned (1:1:1; with use of an interactive web-based system in block sizes of three, stratified by site) to OCT guidance, IVUS guidance, or angiography-guided stent implantation. We did OCT-guided PCI using a specific protocol to establish stent length, diameter, and expansion according to reference segment external elastic lamina measurements. All patients underwent final OCT imaging (operators in the IVUS and angiography groups were masked to the OCT images). The primary efficacy endpoint was post-PCI minimum stent area, measured by OCT at a masked independent core laboratory at completion of enrolment, in all randomly allocated participants who had primary outcome data. The primary safety endpoint was procedural MACE. We tested non-inferiority of OCT guidance to IVUS guidance (with a non-inferiority margin of 1·0 mm²), superiority of OCT guidance to angiography guidance, and superiority of OCT guidance to IVUS guidance, in a hierarchical manner. This trial is registered with ClinicalTrials.gov, number NCT02471586.

FINDINGS

Between May 13, 2015, and April 5, 2016, we randomly allocated 450 patients (158 [35%] to OCT, 146 [32%] to IVUS, and 146 [32%] to angiography), with 415 final OCT acquisitions analysed for the primary endpoint (140 [34%] in the OCT group, 135 [33%] in the IVUS group, and 140 [34%] in the angiography group). The final median minimum stent area was 5·79 mm² (IQR 4·54-7·34) with OCT guidance, 5·89 mm² (4·67-7·80) with IVUS guidance, and 5·49 mm² (4·39-6·59) with angiography guidance. OCT guidance was non-inferior to IVUS guidance (one-sided 97·5% lower CI -0·70 mm²; p=0·001), but not superior (p=0·42). OCT guidance was also not superior to angiography guidance (p=0·12). We noted procedural MACE in four (3%) of 158 patients in the OCT group, one (1%) of 146 in the IVUS group, and one (1%) of 146 in the angiography group (OCT vs IVUS p=0·37; OCT vs angiography p=0·37).

INTERPRETATION

OCT-guided PCI using a specific reference segment external elastic lamina-based stent optimisation strategy was safe and resulted in similar minimum stent area to that of IVUS-guided PCI. These data warrant a large-scale randomised trial to establish whether or not OCT guidance results in superior clinical outcomes to angiography guidance.

FUNDING

St Jude Medical.

Geographical predisposition influences on the distribution and tissue characterisation of eccentric coronary plaques in non-branching coronary arteries: cross-sectional study of coronary plaques analysed by intravascular ultrasound

BACKGROUND

We investigated the influence of geographical predisposition on the spatial distribution and composition of coronary plaques.

METHODS

Thirty coronary arteries were evaluated. A total of 1441 cross-sections were collected from intravascular ultrasound (IVUS) and radio-frequency signal-based virtual histology (VH-IVUS) imaging. To exclude complex geographical effects of side branches and to localise the plaque distribution, we analysed only eccentric plaques in non-branching regions. The spatial distribution of eccentric plaques in the coronary artery was classified into myocardial, lateral, and epicardial regions. The composition of eccentric plaques was analysed using VH-IVUS.

RESULTS

The plaque was concentric in 723 sections (50.2%) and eccentric in 718 (49.9%). Eccentric plaques were more frequently distributed towards the myocardial side than towards the epicardial side (46.7 ± 7.5% vs. 12.5 ± 4.2%, p = 0.003). No significant difference was observed between the myocardial and lateral sides (46.7 ± 7.5% vs. 20.8 ± 5.0%) or between the lateral and epicardial sides. Eccentric thin-capped fibroatheromas were more frequently distributed towards the myocardial side than towards the lateral side (p = 0.024) or epicardial side (p = 0.005).

CONCLUSION

Geographical predisposition is associated with distribution, tissue characterisation, and vulnerability of plaques in non-branching coronary arteries.

Physiological assessment of coronary lesion severity: fractional flow reserve versus nonhyperaemic indices

Coronary angiography alone cannot accurately identify the haemodynamic impact of a coronary artery stenosis. Current international guidelines for myocardial revascularization recommend that inducible ischaemia should be demonstrated before the consideration of percutaneous coronary intervention. Invasive physiological assessment of coronary stenosis severity has increasingly been utilized for this purpose and use of the best validated technique, fractional flow reserve (FFR), has been shown to improve clinical outcomes in patients with stable and unstable coronary artery disease. This has led to the use of FFR being recommended in international revascularization guidelines, despite which, clinical uptake has been limited. One potential reason for slow adoption has been the requirement for maximal hyperaemia at the time of FFR measurement, usually achieved by the administration of pharmacological vasodilators such as adenosine. In some healthcare systems, adenosine is expensive and, in addition, its use can be associated with significant, albeit transient, adverse effects that patients (and some operators) find uncomfortable. Consequently, several methods of nonhyperaemic lesion assessment and their potential role in decision making have been reported. In this review we will review and discuss the current evidence for hyperaemic and nonhyperaemic methods of lesion assessment. We will also look at hybrid strategies that utilize both hyperaemic and nonhyperaemic methods as a means of potentially maintaining diagnostic accuracy while minimizing the requirement for adenosine administration and discuss whether or not they represent viable clinical alternatives.

The Prognosis of Patients With Nonobstructive Coronary Artery Disease Versus Normal Arteries Determined by Invasive Coronary Angiography or Computed Tomography Coronary Angiography: A Systematic Review

Limited data exist regarding the outcomes of patients with nonobstructive coronary artery disease (CAD) detected by computed tomography coronary angiography (CTCA) or invasive coronary angiography (ICA). Our aim was to compare the prognosis of patients with nonobstructive coronary artery plaques with that of patients with entirely normal arteries. The MEDLINE, Cochrane Library, and Embase databases were searched. Studies comparing the prognosis of individuals with nonobstructive CAD versus normal coronary arteries detected by CTCA or ICA were included. The primary outcome was major adverse cardiac events (MACE) including cardiac death, nonfatal myocardial infarction, hospitalization due to unstable angina or revascularization. A fixed effects model was chosen to pool the estimates of odds ratios (ORs). Forty-eight studies with 64,905 individuals met the inclusion criteria. Patients in the nonobstructive CAD arm had a significantly higher risk of MACE compared to their counterparts in the normal artery arm (pooled OR, 3.17, 95% confidence interval, 2.77-3.63). When excluding revascularization as an endpoint, hard cardiac composite outcomes were also more frequent among patients with nonobstructive CAD (pooled OR, 2.10; 95%CI, 1.79-2.45). All subgroups (age, sex, follow-up duration, different outcomes, diagnostic modality, and CAD risk factor) consistently showed a poorer prognosis with nonobstructive CAD than with normal arteries. When dividing the studies into a CTCA and ICA group for further analysis based on the indications for diagnostic tests, we also found nonobstructive CAD to be associated with a higher risk of MACE in both stable and acute chest pain. Patients with nonobstructive CAD had a poorer prognosis compared with their counterparts with normal arteries.

SCAI Expert consensus statement: Evaluation, management, and special considerations of cardio-oncology patients in the cardiac catheterization laboratory (endorsed by the cardiological society of india, and sociedad Latino Americana de Cardiologıa intervencionista)

In the United States alone, there are currently approximately 14.5 million cancer survivors, and this number is expected to increase to 20 million by 2020. Cancer therapies can cause significant injury to the vasculature, resulting in angina, acute coronary syndromes (ACS), stroke, critical limb ischemia, arrhythmias, and heart failure, independently from the direct myocardial or pericardial damage from the malignancy itself. Consequently, the need for invasive evaluation and management in the cardiac catheterization laboratory (CCL) for such patients has been increasing. In recognition of the need for a document on special considerations for cancer patients in the CCL, the Society for Cardiovascular Angiography and Interventions (SCAI) commissioned a consensus group to provide recommendations based on the published medical literature and on the expertise of operators with accumulated experience in the cardiac catheterization of cancer patients.

Co-registration of angiography and intravascular ultrasound images through image-based device tracking

OBJECTIVES

To determine the feasibility of automated co-registration of angiography and intravascular ultrasound (IVUS) to facilitate integration of these two imaging modalities in a synchronous manner.

BACKGROUND

IVUS provides cross-sectional imaging of coronary arteries but lacks overview of the vascular territory provided by angiography. Co-registration of angiography and IVUS would increase utility of IVUS in the clinical setting.

METHODS

Forty-nine consecutive patients undergoing surveillance for cardiac allograft vasculopathy with angiography and IVUS of the left anterior descending artery (LAD) were enrolled. A pre-IVUS angiogram of the LAD was performed followed by an ECG-triggered fluoroscopy (ECGTF) during IVUS pullback at 0.5 mm/s using an automatic pullback device. ECGTF was used to track the IVUS catheter during pullback and establish a spatial relationship to the pre-IVUS angiogram. Angio-IVUS co-registration was performed with a research prototype (Siemens Healthcare, Germany) and accuracy was evaluated by distance mismatch between angiography and IVUS images at vessel bifurcations.

RESULTS

Median age was 54 (44.5, 67) years. The population was 82.6% male with minimal risk factors. The median (IQR) co-registration distance mismatch measured at 108 bifurcations in 42 (85%) patients was 0.35 (0.00-1.16) mm. Seven patients were excluded due to inappropriate data acquisition (n = 3) and failure of tracking (n = 4), e.g., due to overlapping sternal wires. Estimated effective radiation dose for ECGTF was 0.09 mSv.

CONCLUSION

This study demonstrates the feasibility of angio-IVUS co-registration which may be used as a clinical tool for localizing IVUS cross-sections along an angiographic roadmap. © 2015 Wiley Periodicals, Inc.

Wall thickening pattern in atherosclerotic basilar artery stenosis

Our aim was to investigate wall thickening (WT) pattern of atherosclerotic basilar artery stenosis with three-dimensional volumetric isotropic turbo spin echo acquisition (3D VISTA), and the relationship with clinical characteristics. Twenty consecutive patients with atherosclerotic basilar artery stenosis were prospectively enrolled. All cross-sectional slices on VISTA images of basilar arteries were assessed, and classified as eccentric or concentric WT. Clinical characteristics and degree of stenosis were compared between the patients with different wall WT pattern. Wall abnormalities were identified in 568 cross-sectional slices in basilar arteries of 20 patients including eccentric WT in 497 (87.5 %) slices, and concentric WT in 71 (12.5 %) slices. In 11 of 20 patients, all the cross-sectional slices (293 slices) showed eccentric WT. In 9 of 20 patients, the cross-sectional slices (275 slices) showed both eccentric WT (204 slices, 74.2 %) and concentric WT (71 slices, 25.8 %). No lesion showed only concentric WT. At the slices of maximum luminal narrowing sites, only one patient showed concentric WT. Symptomatic stenosis was more common in the patients with mixed WT (eccentric and concentric), compared to patients with only eccentric WT (100 vs 54.5 %, p = 0.038). Atherosclerotic basilar artery stenosis could show both eccentric and concentric WT based on each slice analysis. Concentric WT was found in near half of the patients, but tended to locate in minimal slices. No lesion was entirely concentric. Lesions with mixed WT (concentric and eccentric) might represent advanced atherosclerosis with high risk of ischemic event.

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.

Three-dimensional quantitative coronary angiography and quantification of jeopardised myocardium to predict functional significance of intermediate coronary artery stenosis

AIMS

Despite the fact that fractional flow reserve (FFR) is better than angiography in guiding PCI, in the real world the choice to perform PCI is generally based on angiography. Three-dimensional quantitative coronary angiography (3D-QCA) may increase the accuracy of angiography, especially in intermediate coronary artery stenosis (ICAS). The aim of the study was to assess the best cut-off values of area stenosis % (AS%) and the extent of jeopardised myocardium for predicting FFR and for excluding the need to perform FFR.

METHODS AND RESULTS

FFR, AS% and Myocardial Jeopardy Index (MJI) were assessed in 211 ICAS. MJI (=-0.36; p=0.001), AS% (=-0.35; p=0.001) and presence of a chronic total occlusion (CTO) (=-0.15; p=0.01) were independent predictors of FFR. In patients without CTO (174 lesions), the best cut-offs for the detection of FFR ≤0.80 for AS% and MJI were 61% (AUC=0.76; p<0.001) and 30% (AUC=0.71; p<0.001), respectively. More importantly, the cut-offs of AS% safely to exclude (100% sensitivity) an FFR ≤0.80 were 40% (AUC=0.85, p<0.001) for an MJI ≥30% and 50% (AUC=0.70, p<0.04) for an MJI <30%, respectively.

CONCLUSIONS

AS%, MJI and the presence of a CTO predicted FFR values. 3D-QCA in addition to MJI allows the safe exclusion of FFR ≤0.80, limiting FFR assessment to doubtful cases with considerable reduction of costs.

Role of intravascular ultrasound in unprotected left main percutaneous coronary intervention

Percutaneous coronary intervention (PCI) to the unprotected left main stem offers an attractive alternative to bypass grafting, but is associated with a significant clinical risk and therefore demands special consideration. Successful left main PCI is dependent upon the morphology of the lesion and the technical quality of the procedure. For these reasons, intravascular ultrasound (IVUS) has been the most popular adjunct to coronary angiography during left main PCI. However, trials of IVUS in left main PCI have produced inconclusive results, and most data predate the use of drug-eluting stents. Despite this, IVUS offers practical benefits in both case selection, and in guiding angioplasty and stenting. Here, we review the arguments for the present and future role of IVUS in left main PCI.

Impact of Intravascular Ultrasound in Clinical Practice

Intravascular ultrasound (IVUS) has expanded our understanding of atherosclerotic plaque morphology, and provides an opportunity to guide cardiovascular interventions and evaluate results. Use of this technique requires understanding of ultrasound physics, catheter differences, skills in vessel, plaque and stent quantification and knowledge of artifacts and various physiologic and pathologic findings. Optimal cardiovascular interventions should result in absence of inflow or outflow obstruction, precise geographic landing, while attaining the largest feasible luminal gain without plaque protrusion, vessel dissection or perforation and, if deployed, with complete stent expansion and apposition to the vessel wall. IVUS is safe, cost efficient and effectively optimises cardiovascular interventions. In addition, IVUS improves outcomes when used to guide coronary interventions using bare metal stents (BMS) and drug eluting stents (DES). The role of IVUS in endovascular therapy is rapidly expanding. This review will focus on the impact of IVUS in clinical practice.

Long-term follow-up of patients with deferred coronary intervention guided by measurement of fractional flow reserve

INTRODUCTION AND AIMS

The functional significance of coronary lesions can be assessed in the cardiac catheterization laboratory by determination of fractional flow reserve (FFR), thus overcoming one of the major limitations of conventional angiography. The aim of this study was to analyze the long-term clinical course of patients with intermediate coronary stenosis (50-70%) deferred for intervention based on FFR <0.80.

METHODS

Between May 1999 and December 2009, 300 lesions in 231 patients (mean age 65 ± 10 years, 68% male and 75.3% with multivessel disease) were studied by FFR. Intervention was deferred in 282 (94%) lesions and 18 were treated based on FFR <0.80. We assessed the occurrence of major adverse cardiovascular events (MACE), defined as cardiovascular death, non-fatal acute coronary syndrome and target lesion revascularization (TLR).

RESULTS

During a median follow-up of 637 days (interquartile range 455-1160), there were 15 (6.5%) MACE in the subgroup of patients with target lesion intervention deferred based on FFR: one cardiovascular death, four hospitalizations for acute coronary syndrome and 14 TLR (12 patients were treated percutaneously and two underwent coronary artery bypass grafting). MACE-free survival at one year follow-up was 97.8%.

CONCLUSION

These results, in a real-world population, support the current trend to base the decision to treat on functional rather than purely anatomical criteria, in order to improve safety and efficiency.

The importance of functional tests in personalized medicine

Cardiovascular disease is the most prevalent disease mainly in the Western society and becoming the leading cause of death worldwide. Standard methods by which healthcare providers screen for cardiovascular disease have only minimally reduced the burden of disease while exponentially increasing costs. As such, more specific and individualized methods for functionally assessing cardiovascular threats are needed to identify properly those at greatest risk, and appropriately treat these patients so as to avoid a fate such as heart attack, stroke, or death. Currently, endothelial function testing-in both the coronary and peripheral circulation-is well established as being associated with the disease process and future cardiovascular events. Improving such testing can lead to a reduction in the risk of future events. Combining this functional assessment of vascular fitness with other, more personalized, testing methods should serve to identify those at the greatest risk of cardiovascular disease earlier and subsequently reduce the affliction of such diseases worldwide.

Numerical flow analysis of coronary arteries through concentric and eccentric stenosed geometries

In this study, the flow characteristics through specific concentric and eccentric plaque formations are investigated via Large Eddy Simulation (LES) turbulence technique considering pulsatile flow conditions adjusted for a single frequency-sinusoidal motion (SIN) and for the coronary arteries namely the Left Anterior Descending (LAD) and Right Coronary Artery (RCA). This specific plaque formation is a combination of a highly eccentric shape with triangular-like cross-section for which the flow behaviour has not been studied before. The pulsatile flow behaviour in conjunction with non-Newtonian blood model for SIN, RCA and LAD is found to have considerable effect on formation of separation bubbles and jets, coherent structures associated with vortex rings and horseshoe vortices, wall shear and pressure drop. It should be stated that the quantitative outcome from this study has been the extra pressure load estimated on the heart which was approximately 17% of eccentric model and 9% of concentric model both in RCA or LAD case for a 75% occlusion scenario.

Coronary β2-adrenoreceptors mediate endothelium-dependent vasoreactivity in humans: novel insights from an in vivo intravascular ultrasound study

AIMS

The interaction between coronary β(2)-adrenoreceptors and segmental plaque burden is complex and poorly understood in humans. We aimed to validate intracoronary (IC) salbutamol as a novel endothelium-dependent vasodilator utilizing intravascular ultrasound (IVUS), and thus assess relationships between coronary β(2)-adrenoreceptors, regional plaque burden and segmental endothelial function.

METHODS AND RESULTS

In 29 patients with near-normal coronary angiograms, IVUS-upon-Doppler Flowire imaging protocols were performed. Protocol 1: incremental IC salbutamol (0.15, 0.30, 0.60 μg/min) infusions (15 patients, 103 segments); protocol 2: salbutamol (0.30 μg/min) infusion before and after IC administration of N(G)-monomethyl-L-arginine (L-NMMA) (10 patients, 82 segments). Vehicle infusions (IC dextrose) were performed in 4 patients (21 segments). Macrovascular response [% change segmental lumen volume (ΔSLV)] and plaque burden [per cent atheroma volume (PAV)] were studied in 5-mm coronary segments. Microvascular response [per cent change in coronary blood flow (ΔCBF)] was calculated following each infusion. Intracoronary salbutamol demonstrated significant dose-response ΔSLV and ΔCBF from baseline, respectively (0.15 μg/min: 3.5 ± 1.3%, 28 ± 14%, P = 0.04, P = NS; 0.30 μg/min: 5.5 ± 1.4%, 54 ± 17%, P = 0.001, P < 0.0001; 0.60 μg/min: 4.8 ± 1.6%, 66 ± 15%, P = 0.02, P < 0.0001), with ΔSLV responses further exemplified in low vs. high plaque burden groups. Salbutamol vasomotor responses were suppressed by l-NMMA, supporting nitric oxide-dependent mechanisms. Vehicle infusions resulted in no significant ΔSLV or ΔCBF. Multivariate analysis including conventional cardiovascular risk factors, PAV, segmental remodelling and plaque eccentricity indices identified PAV as the only significant predictor of a ΔSLV to IC salbutamol (coefficient -0.18, 95% CI -0.32 to -0.044, P = 0.015). Conclusions Intracoronary salbutamol is a novel endothelium-dependent epicardial and microvascular coronary vasodilator. Intravascular ultrasound-derived regional plaque burden is a major determinant of segmental coronary endothelial function.