Detection by near-infrared spectroscopy of large lipid core plaques at culprit sites in patients with acute ST-segment elevation myocardial infarction. JACC Cardiovasc Interv. 2013;6:838-846. [PMID: 23871513 DOI: 10.1016/j.jcin.2013.04.012]

The role of near-infrared spectroscopy in the detection of vulnerable atherosclerotic plaques

Coronary artery disease is the leading cause of mortality worldwide. Most acute coronary syndromes are caused by a rupture of a vulnerable atherosclerotic plaque which can be characterized by a lipid-rich necrotic core with an overlying thin fibrous cap. Many vulnerable plaques can cause angiographically mild stenoses due to positive remodelling, which is why the extent of coronary artery disease may be seriously underestimated. In recent years, we have witnessed a paradigm shift in interventional cardiology. We no longer focus solely on the degree of stenosis; rather, we seek to determine the true extent of atherosclerotic disease. We seek to identify high-risk plaques for improvement in risk stratification of patients and prevention. Several imaging methods have been developed for this purpose. Intracoronary near-infrared spectroscopy is one of the most promising. Here, we discuss the possible applications of this diagnostic method and provide a comprehensive overview of the current knowledge.

Impact of Longitudinal Lesion Geometry on Location of Plaque Rupture and Clinical Presentations

OBJECTIVES

This study sought to investigate the impact of longitudinal lesion geometry on the location of plaque rupture and clinical presentation and its mechanism.

BACKGROUND

The relationships among lesion geometry, external hemodynamic forces acting on the plaque, location of plaque rupture, and clinical presentation have not been comprehensively investigated.

METHODS

This study enrolled 125 patients with plaque rupture documented by intravascular ultrasound. Longitudinal locations of plaque rupture were identified and categorized by intravascular ultrasound. Patients' clinical presentations and TIMI (Thrombolysis In Myocardial Infarction) flow grade in an initial angiogram were compared according to the location of plaque rupture. Longitudinal lesion asymmetry was quantitatively assessed by the luminal radius change over the segment length (radius gradient [RG]). Lesions with a steeper radius change in the upstream segment compared with the downstream segment (RG_upstream > RG_downstream) were defined as upstream-dominant lesions.

RESULTS

On the basis of the site of maximum rupture aperture, 56.0%, 16.0%, and 28.0% of the patients had upstream, minimal lumen area, and downstream rupture, respectively. Patients with upstream rupture more frequently presented with ST-segment elevation myocardial infarction (45.7%, 40.0%, 22.9%; p = 0.030) and with TIMI flow grade <3 (32.9%, 20.0%, 17.1%; p = 0.042). According to the ratio of upstream and downstream RG, 69.5% of lesions were classified as upstream-dominant lesions, and 30.5% were classified as downstream-dominant lesions. Among the 66 upstream-dominant lesions, 65 cases (98.5%) had upstream rupture, and the RG ratio (RG_upstream/RG_downstream) was an independent predictor of upstream rupture (odds ratio: 1.481; 95% confidence interval: 1.035 to 2.120; p = 0.032). Upstream-dominant lesions more frequently manifested with ST-segment elevation myocardial infarction than did downstream-dominant lesions (48.5% vs. 24.1%; p = 0.026).

CONCLUSIONS

Both clinical presentation and degree of flow limitation were associated with the location of plaque rupture. Longitudinal lesion asymmetry assessed by RG, which can affect regional distribution of hemodynamic stress, was associated with the location of rupture and with clinical presentation.

Stenting precision: "Image small, miss small"

Stenting by angiography alone predisposes to geographic miss STEMI culprit lesions are most susceptible to Geographic Miss Direct coronary imaging assures procedural precision and perfection.

Fully Automated Lipid Pool Detection Using Near Infrared Spectroscopy

Background. Detecting and identifying vulnerable plaque, which is prone to rupture, is still a challenge for cardiologist. Such lipid core-containing plaque is still not identifiable by everyday angiography, thus triggering the need to develop a new tool where NIRS-IVUS can visualize plaque characterization in terms of its chemical and morphologic characteristic. The new tool can lead to the development of new methods of interpreting the newly obtained data. In this study, the algorithm to fully automated lipid pool detection on NIRS images is proposed. Method. Designed algorithm is divided into four stages: preprocessing (image enhancement), segmentation of artifacts, detection of lipid areas, and calculation of Lipid Core Burden Index. Results. A total of 31 NIRS chemograms were analyzed by two methods. The metrics, total LCBI, maximal LCBI in 4 mm blocks, and maximal LCBI in 2 mm blocks, were calculated to compare presented algorithm with commercial available system. Both intraclass correlation (ICC) and Bland-Altman plots showed good agreement and correlation between used methods. Conclusions. Proposed algorithm is fully automated lipid pool detection on near infrared spectroscopy images. It is a tool developed for offline data analysis, which could be easily augmented for newer functions and projects.

Characterization of coronary atherosclerosis by intravascular imaging modalities

Coronary artery disease (CAD) is highly prevalent in Western countries and is associated with morbidity, mortality, and a significant economic burden. Despite the development of anti-atherosclerotic medical therapies, many patients still continue to suffer from coronary events. This residual risk indicates the need for better risk stratification and additional therapies to achieve more reductions in cardiovascular risk. Recent advances in imaging modalities have contributed to visualizing atherosclerotic plaques and defining lesion characteristics in vivo. This innovation has been applied to refining revascularization procedure, assessment of anti-atherosclerotic drug efficacy and the detection of high-risk plaques. As such, intravascular imaging plays an important role in further improvement of cardiovascular outcomes in patients with CAD. The current article reviews available intravascular imaging modalities with regard to its method, advantage and disadvantage.

Management of Multivessel Coronary Disease in ST-segment Elevation Myocardial Infarction

Primary PCI of infarct-related arteries is the preferred reperfusion strategy in patients presenting with ST-segment elevation myocardial infarction (STEMI). Up to 40 % of such patients demonstrate evidence of multivessel, non-infarct-related artery coronary disease. Previous non-randomised observational studies and their associated meta-analyses have suggested that in such cases only the culprit infarct-related artery (IRA) lesion should be treated. However, recent randomised controlled trials have demonstrated improved clinical outcomes with lower major adverse cardiovascular events (MACE) rates when complete revascularisation is undertaken either at index primary percutaneous coronary intervention (PPCI) or during index admission. These trials suggest that current guidelines pertaining to treatment of non-infarct-related artery (N-IRA) lesions in STEMI patients with multivessel disease may need to be reconsidered depending on future trials. However, issues remain around timing of N-IRA intervention, the use of fractional flow reserve (FFR) or intravascular imaging to guide intervention in N-IRA lesions and the need to demonstrate reductions in hard clinical endpoints (death and MI) after complete revascularisation; these issues will need to be addressed through future trials. Clinicians must judge on the currently available data, whether it is still safer to leave important stenosis in N-IRA untreated.

Intracoronary near-infrared spectroscopy: an overview of the technology, histologic validation, and clinical applications

Intracoronary near-infrared spectroscopy (NIRS) imaging, which is now clinically available in a combined NIRS and intravascular ultrasound catheter, is a novel catheter-based imaging modality capable of identifying lipid core plaque within the coronary arteries of living patients. The present manuscript provides an overview of intracoronary NIRS imaging with a focus on several concepts essential to individuals seeking to better understand this novel imaging modality. One of the major assets of NIRS is that it has been rigorously validated against the gold standard of histopathology and has been shown to accurately identify histologically-proven fibroatheroma. Clinical studies of NIRS have demonstrated its ability to accurately identify large lipid core plaques at culprit lesions across the spectrum of acute coronary syndromes. NIRS has also been shown to detect lesions at increased risk of causing peri-procedural myocardial infarction during PCI. With regards to predicting future risk, NIRS is seemingly capable of identifying vulnerable patients at increased risk of experiencing subsequent patient-level cardiovascular events. In addition to these clinical applications of NIRS, there are several large prospective observational studies underway to determine if NIRS imaging will be able to identify vulnerable plaques at increased risk of triggering site-specific future coronary events. These studies, once completed, are anticipated to provide valuable data regarding the ability of NIRS imaging to identify plaque vulnerability.

Imaging of coronary atherosclerosis - evolution towards new treatment strategies

Coronary atherosclerosis and the precipitation of acute myocardial infarction are highly complex processes, which makes accurate risk prediction challenging. Rapid developments in invasive and noninvasive imaging technologies now provide us with detailed, exquisite images of the coronary vasculature that allow direct investigation of a wide range of these processes. These modalities include sophisticated assessments of luminal stenoses and myocardial perfusion, complemented by novel measures of the atherosclerotic plaque burden, adverse plaque characteristics, and disease activity. Together, they can provide comprehensive, individualized assessments of coronary atherosclerosis as it occurs in patients. Not only can this information provide important pathological insights, but it can also potentially be used to guide personalized treatment decisions. In this Review, we describe the latest advances in both established and emerging imaging techniques, focusing on the strengths and weakness of each approach. Moreover, we discuss how these technological advances might be translated from attractive images into novel imaging strategies and definite improvements in clinical risk prediction and patient outcomes. This process will not be easy, and the many potential barriers and difficulties are also reviewed.

A Broadband Polyvinylidene Difluoride-Based Hydrophone with Integrated Readout Circuit for Intravascular Photoacoustic Imaging

Intravascular photoacoustic (IVPA) imaging can visualize the coronary atherosclerotic plaque composition on the basis of the optical absorption contrast. Most of the photoacoustic (PA) energy of human coronary plaque lipids was found to lie in the frequency band between 2 and 15 MHz requiring a very broadband transducer, especially if a combination with intravascular ultrasound is desired. We have developed a broadband polyvinylidene difluoride (PVDF) transducer (0.6 × 0.6 mm, 52 μm thick) with integrated electronics to match the low capacitance of such a small polyvinylidene difluoride element (<5 pF/mm(2)) with the high capacitive load of the long cable (∼100 pF/m). The new readout circuit provides an output voltage with a sensitivity of about 3.8 μV/Pa at 2.25 MHz. Its response is flat within 10 dB in the range 2 to 15 MHz. The root mean square (rms) output noise level is 259 μV over the entire bandwidth (1-20 MHz), resulting in a minimum detectable pressure of 30 Pa at 2.25 MHz.

Invasive coronary imaging: any role in primary and secondary prevention?

This review discusses the possibilities offered by new modalities of non-invasive and invasive coronary imaging in an effort to optimize risk stratification for coronary artery disease, and identify subgroups at high risk that may benefit from an aggressive, personalized approach, with access to a growing number of novel drugs and interventions. Special emphasis is placed on the progress of novel invasive imaging techniques such as near infrared spectroscopy and optical coherence tomography that can reliably identify thin-capped fibroatheromas. Multiple trials are exploring the feasibility of these techniques to guide modulation of risk factor control and treatment of non-flow limiting lesions at high risk of destabilization and progression in patients undergoing clinically mandated angioplasty of angiographically critical lesions. Asymptomatic patients at high risk of cardiovascular ischaemic events may also benefit, with the intermediate step of a wider application of calcium score and angiography with multi-slice computed tomography, by a selective use of invasive imaging.

Clinical Characterization of Coronary Atherosclerosis With Dual-Modality OCT and Near-Infrared Autofluorescence Imaging

OBJECTIVES

The authors present the clinical imaging of human coronary arteries in vivo using a multimodality optical coherence tomography (OCT) and near-infrared autofluorescence (NIRAF) intravascular imaging system and catheter.

BACKGROUND

Although intravascular OCT is capable of providing microstructural images of coronary atherosclerotic lesions, it is limited in its capability to ascertain the compositional/molecular features of plaque. A recent study in cadaver coronary plaque showed that endogenous NIRAF is elevated in necrotic core lesions. The combination of these 2 technologies in 1 device may therefore provide synergistic data to aid in the diagnosis of coronary pathology in vivo.

METHODS

We developed a dual-modality intravascular imaging system and 2.6-F catheter that can simultaneously acquire OCT and NIRAF data from the same location on the artery wall. This technology was used to obtain volumetric OCT-NIRAF images from 12 patients with coronary artery disease undergoing percutaneous coronary intervention. Images were acquired during a brief, nonocclusive 3- to 4-ml/s contrast purge at a speed of 100 frames/s and a pullback rate of 20 or 40 mm/s. OCT-NIRAF data were analyzed to determine the distribution of the NIRAF signal with respect to OCT-delineated plaque morphological features.

RESULTS

High-quality intracoronary OCT and NIRAF image data (>50-mm pullback length) were successfully acquired without complication in all patients (17 coronary arteries). The maximum NIRAF signal intensity of each plaque was compared with OCT-defined type, showing a statistically significant difference between plaque types (1-way analysis of variance, p < 0.0001). Interestingly, coronary arterial NIRAF intensity was elevated only focally in plaques with a high-risk morphological phenotype (p < 0.05), including OCT fibroatheroma, plaque rupture, and fibroatheroma associated with in-stent restenosis.

CONCLUSIONS

This OCT-NIRAF study demonstrates that dual-modality microstructural and fluorescence intracoronary imaging can be safely and effectively conducted in human patients. Our findings show that NIRAF is associated with a high-risk morphological plaque phenotype. The focal distribution of NIRAF in these lesions furthermore suggests that this endogenous imaging biomarker may provide complementary information to that obtained by structural imaging alone.

Invasive evaluation of plaque morphology of symptomatic superficial femoral artery stenoses using combined near-infrared spectroscopy and intravascular ultrasound

The purpose of this study is to characterize the plaque morphology of severe stenoses in the superficial femoral artery (SFA) employing combined near-infrared spectroscopy and intravascular ultrasound (NIRS-IVUS). Atherosclerosis is the most common cause of symptomatic peripheral arterial disease. Plaque composition of SFA stenoses has been characterized as primarily fibrous or fibrocalcific by non-invasive and autopsy studies. NIRS has been validated to detect lipid-core plaque (LCP) in the coronary circulation. We imaged severe SFA stenoses with NIRS-IVUS prior to revascularization in 31 patients (46 stenoses) with Rutherford claudication ⩾ class 3. Angiographic parameters included lesion location and stenosis severity. IVUS parameters included plaque burden and presence of calcium. NIRS images were analyzed for LCP and maximum lipid-core burden index in a 4-mm length of artery (maxLCBI4mm). By angiography, 38 (82.6%) lesions were calcified and 9 (19.6%) were chronic total occlusions. Baseline stenosis severity and lesion length were 86.0 ± 11.0% and 36.5 ± 46.5 mm, respectively. NIRS-IVUS identified calcium in 45 (97.8%) lesions and LCP in 17 (37.0%) lesions. MaxLCBI4mm was 433 ± 244. All lesions with LCP also contained calcium; there were no non-calcified lesions with LCP. In conclusion, this is the first study of combined NIRS-IVUS in patients with PAD. NIRS-IVUS demonstrates that nearly all patients with symptomatic severe SFA disease have fibrocalcific plaque, and one-third of such lesions contain LCP. These findings contrast with those in patients with acute coronary syndromes, and may have implications regarding the pathophysiology of atherosclerosis in different vascular beds.

Confirmation of the Intracoronary Near-Infrared Spectroscopy Threshold of Lipid-Rich Plaques That Underlie ST-Segment-Elevation Myocardial Infarction

OBJECTIVE

In a previous exploratory analysis, intracoronary near-infrared spectroscopy (NIRS) found the majority of culprit lesions in ST-segment-elevation myocardial infarction (STEMI) to contain a maximum lipid core burden index in 4 mm (maxLCBI4mm) of >400. This initial study was limited by a small sample size, enrollment at a single center, and post hoc selection of the maxLCBI4mm ≥400 threshold. This study was designed a priori to substantiate the ability of NIRS to discriminate STEMI culprit from nonculprit segments and to confirm the performance of the maxLCBI4mm ≥400 threshold.

APPROACH AND RESULTS

At 2 centers in the United States and Sweden, 75 STEMI patients underwent intracoronary NIRS imaging after establishing thrombolysis in myocardial infarction 3 flow, but before stenting. Blinded core laboratory analysis defined the culprit segment as the 10-mm segment distal to the proximal angiographic culprit margin. The remaining vessel was divided into contiguous 10-mm nonculprit segments. The maxLCBI4mm of culprit segments (median [interquartile range]: 543 [273-756]) was 4.4-fold greater than nonculprit segments (median [interquartile range]: 123 [0-307]; P<0.001). Receiver-operating characteristic analysis demonstrated that maxLCBI4mm differentiated culprit from nonculprit segments with high accuracy (c-statistic=0.83; P<0.001). A threshold maxLCBI4mm ≥400 identified STEMI culprit segments with a sensitivity of 64% and specificity of 85%.

CONCLUSIONS

This study substantiates the ability of NIRS to accurately differentiate STEMI culprit from nonculprit segments and confirms that a threshold maxLCBI4mm ≥400 is detected by NIRS in the majority of STEMI culprits.

The value of imaging in subclinical coronary artery disease

Although the treatment of acute coronary syndromes (ACS) has advanced considerably, the ability to detect, predict, and prevent complications of atherosclerotic plaques, considered the main cause of ACS, remains elusive. Several imaging tools have therefore been developed to characterize morphological determinants of plaque vulnerability, defined as the propensity or probability of plaques to complicate with coronary thrombosis, able to predict patients at risk. By utilizing both intravascular and noninvasive imaging tools, indeed prospective longitudinal studies have recently provided considerable knowledge, increasing our understanding of determinants of plaque formation, progression, and instabilization. In the present review we aim at 1) critically analyzing the incremental utility of imaging tools over currently available "traditional" methods of risk stratification; 2) documenting the capacity of such modalities to monitor atherosclerosis progression and regression according to lifestyle modifications and targeted therapy; and 3) evaluating the potential clinical relevance of advanced imaging, testing whether detection of such lesions may guide therapeutic decisions and changes in treatment strategy. The current understanding of modes of progression of atherosclerotic vascular disease and the appropriate use of available diagnostic tools may already now gauge the selection of patients to be enrolled in primary and secondary prevention studies. Appropriate trials should now, however, evaluate the cost-effectiveness of an aggressive search of vulnerable plaques, favoring implementation of such diagnostic tools in daily practice.

Large lipid-rich coronary plaques detected by near-infrared spectroscopy at non-stented sites in the target artery identify patients likely to experience future major adverse cardiovascular events

AIMS

A recent study demonstrated that intracoronary near-infrared spectroscopy (NIRS) findings in non-target vessels are associated with major adverse cardiovascular and cerebrovascular events (MACCE). It is unknown whether NIRS findings at non-stented sites in target vessels are similarly associated with future MACCE. This study evaluated the association between large lipid-rich plaques (LRP) detected by NIRS at non-stented sites in a target artery and subsequent MACCE.

METHODS AND RESULTS

This study evaluated 121 consecutive registry patients undergoing NIRS imaging in a target artery. After excluding stented segments, target arteries were evaluated for a large LRP, defined as a maximum lipid core burden index in 4 mm (maxLCBI4 mm) ≥400. Excluding events in stented segments, Cox regression analysis was performed to evaluate for an association between a maxLCBI4 mm ≥400 and future MACCE, defined as all-cause mortality, non-fatal acute coronary syndrome, and cerebrovascular events. NIRS detected a maxLCBI4 mm ≥400 in a non-stented segment of the target artery in 17.4% of patients. The only baseline clinical variable marginally associated with MACCE was ejection fraction (HR 0.96, 95% CI 0.93-1.00, P = 0.054). A maxLCBI4 mm ≥400 in a non-stented segment at baseline was significantly associated with MACCE during follow-up (HR 10.2, 95% CI 3.4-30.6, P < 0.001).

CONCLUSION

Detection of large LRP by NIRS at non-stented sites in a target artery was associated with an increased risk of future MACCE. These findings support ongoing prospective studies to further evaluate the ability of NIRS to identify vulnerable patients.

Plaque disruption by coronary computed tomographic angiography in stable patients vs. acute coronary syndrome: a feasibility study

AIMS

This study was designed to determine whether coronary CT angiography (CTA) can detect features of plaque disruption in clinically stable patients and to compare lesion prevalence and features between stable patients and those with acute coronary syndrome (ACS).

METHODS

We retrospectively identified patients undergoing CTA, followed by invasive coronary angiography (ICA) within 60 days. Quantitative 3-vessel CTA lesion analysis was performed on all plaques ≥25% stenosis to assess total plaque volume, low attenuation plaque (LAP, <50 HU) volume, and remodelling index. Plaques were qualitatively assessed for CTA features of disruption, including ulceration and intra-plaque dye penetration (IDP). ICA was employed as a reference standard for disruption. A total of 145 (94 ACS and 51 stable) patients were identified. By CTA, plaque disruption was evident in 77.7% of ACS cases. Although more common among those with ACS, CTA also detected plaque disruption in 37.3% of clinically stable patients (P < 0.0001).

CONCLUSIONS

Clinically stable patients commonly manifest plaques with features of disruption as determined by CTA. Though the prevalence of plaque disruption is less than patients with ACS, these findings support the concept that some clinically stable patients may harbour 'silent' disrupted plaques. These findings may have implications for detection of 'at risk' plaques and patients.

Increased coronary lipid accumulation in heart transplant recipients with prior high-grade cellular rejection: novel insights from near-infrared spectroscopy

Cardiac allograft vasculopathy is a major cause of morbidity and mortality among patients after heart transplantation. We sought to assess the amount of lipid accumulation in the coronary arteries of transplant patients according to rejection grade. Overall, 39 consecutive heart transplant recipients undergoing annual routine surveillance coronary angiography underwent near-infrared spectroscopy and intravascular ultrasound imaging of 1 coronary artery. Rejection history was graded according to the International Society of Heart and Lung Transplantation (ISHLT) classification as none/mild/moderate-grade rejection (ISHLT 0, 1A/1B, or 2) compared to high-grade rejection (≥3A). Patients with prior history of high-grade rejection had larger plaque burden in the distal coronary segments [45.7 % (25.5-63.7) vs 25.1 % (19.9-37.8), p = 0.02] and a higher maximum lipid core burden index in any 4-mm long segment (maxLCBI(4mm)) [243 (91-400) vs 41 (1-170), p = 0.016] as compared with patients with prior history of none/mild/moderate-grade rejection. By multivariable linear regression analysis, prior history of high-grade rejection was an independent predictor for maxLCBI(4mm). A maxLCBI(4mm) >200 distinguished prior history of high-grade from none/mild/moderate rejection with a sensitivity of 61.5 % and specificity of 84.6 %. The current study demonstrates that the coronary arteries of post heart-transplant patients with a prior history of high-grade cellular rejection have increasing amounts of lipid-rich plaque. MaxLCBI(4mm) >200 might differentiate patients with previous high-grade cellular rejection from heart transplant recipients with none/mild/moderate-grade rejection.

Specific imaging of atherosclerotic plaque lipids with two-wavelength intravascular photoacoustics

The lipid content in plaques is an important marker for identifying atherosclerotic lesions and disease states. Intravascular photoacoustic (IVPA) imaging can be used to visualize lipids in the artery. In this study, we further investigated lipid detection in the 1.7-µm spectral range. By exploiting the relative difference between the IVPA signal strengths at 1718 and 1734 nm, we could successfully detect and differentiate between the plaque lipids and peri-adventitial fat in human coronary arteries ex vivo. Our study demonstrates that IVPA imaging can positively identify atherosclerotic plaques using only two wavelengths, which could enable rapid data acquisition in vivo.

Intravascular Near-Infrared Spectroscopy: A Possible Tool for Optimizing the Management of Carotid Artery Disease

Stroke is the second most common cause of morbidity and mortality in the Western nations. It is estimated that approximately one-fifth of all strokes or transient ischemic attacks are caused by carotid artery disease. Thus, treatment of carotid artery disease as a mean of stroke prevention is extremely important. Since the introduction of carotid endarterectomy, debate has persisted over the treatment strategy for carotid artery disease. Current recommendations have many potential flaws because they are often based on older trials performed before the introduction of modern pharmacotherapy and are mostly based on the angiographic degree of stenosis, without an emphasis on the pathophysiology of the disease. Most carotid events are caused by rupture or distal embolization of the content of an unstable atherosclerotic plaque with a large lipid pool. Thus, it is plausible that the information regarding the composition of the atherosclerotic plaque could play an important role in deciding on a treatment strategy. In this review article, we provide information about near-infrared spectroscopy, a new invasive imaging modality, which seems to be capable of providing such information.

Near-infrared spectroscopy for intracoronary detection of lipid-rich plaques to understand atherosclerotic plaque biology in man and guide clinical therapy

Ischaemic heart disease is the leading cause of death worldwide. The common denominator for plaques causing acute coronary syndrome (ACS) is lipid accumulation, either as a lipid core or lipid pools. An intracoronary imaging device to detect lipid-rich plaques (LRPs) could therefore identify most of the plaques causing ACS and sudden death. Near-infrared spectroscopy combined with intravascular ultrasound (NIRS-IVUS) is a promising new intracoronary imaging method that is able to specifically quantify lipid accumulation measured as the lipid core burden index (LCBI). NIRS-IVUS is highly specific for the identification of ST-elevation myocardial infarction (STEMI) and non-ST-elevation myocardial infarction (NSTEMI) culprit plaques usually in the form of a circular LRP. NIRS-IVUS may assist in defining the aetiology of coronary events. The effect of cholesterol-lowering therapy on the lipid core can be measured in coronary plaques in patients, and NIRS-IVUS may be a useful tool for drug development in phase II studies as a surrogate end-point for future ACS. Plaques with a high LCBI have an increased risk of peri-procedural events. NIRS-IVUS can help to define the diameter and length of stents to avoid procedure-related complications. Increased coronary LCBI predicts a higher risk of future cardiovascular events. Lipid core detection using NIRS may help to identify vulnerable plaques to treat them before they cause ACS or sudden death.

Stent edge dissection: depth of injury and adverse outcome

Deep stent edge dissection by OCT predicts adverse outcome. STEMI culprit lesions are most susceptible to edge dissection. Procedural performance influences edge dissection.

Role of near-infrared spectroscopy in intravascular coronary imaging

Near-infrared spectroscopy is an intracoronary imaging modality that has been validated in preclinical and clinical studies to help quantify the lipid content of the coronary plaque and provide information regarding its vulnerability. It has the potential to develop into a valuable tool for the risk stratification of a vulnerable plaque and, furthermore, a vulnerable patient. In addition, in the future this technology may help in the development of novel therapies that impact vascular biology.

Near-infrared spectroscopy combined with intravascular ultrasound in carotid arteries

Limited insights into the pathophysiology of the atherosclerotic carotid stenosis are available in vivo. We conducted a prospective study to assess safety and feasibility of intravascular ultrasound (IVUS) combined with near-infrared spectroscopy (NIRS) in carotid arteries. In addition, we described the size and the distribution of lipid rich plaques in significant atherosclerotic carotid stenoses. In a prospective single centre study 45 consecutive patients (mean age 66 ± 8 years) with symptomatic (≥50 %) or asymptomatic (≥70 %) stenosis of internal carotid artery (ICA) amendable to carotid stenting were enrolled. A 40 mm long NIRS-IVUS pullback through the stenosis was performed. IVUS and NIRS data were analyzed to assess minimal luminal area (MLA), plaque burden (PB), remodeling index (RI), calcifications, lipid core burden index (LCBI), maximal LCBI in any 4 mm segment of the artery (LCBImx) and LCBI in the 4 mm segment at the site of minimal luminal area (LCBImxMLA). NIRS-IVUS pullbacks were safely performed without overt clinical events. LCBImx was significantly higher than LCBImxMLA (369.1 ± 221.1 vs. 215.7 ± 2589; p = 0.004). Conversely, PB was significantly larger at the site of MLA (87.4 ± 4.8 % vs. 58.3 ± 18.2 %; p < 0001). Distance of the NIRS-IVUS frame with the highest LCBI from the site of MLA was 6.5 ± 7.7 mm. Eighty percent of frames with maximal LCBI were localized within 10 mm from the site of MLA and 67 % proximally to or at the site of MLA. This study suggested safety and feasibility of the NIRS-IVUS imaging of the carotid stenosis and provided insights on the distribution of lipids in the carotid stenosis. Lipid rich plaques were more often located in the sites with a milder stenosis and smaller plaque burden than at the site of MLA.

Non-invasive volumetric assessment of aortic atheroma: a core laboratory validation using computed tomography angiography

Aortic atherosclerosis has been linked with worse peri- and post-procedural outcomes following a range of aortic procedures. Yet, there are currently no standardized methods for non-invasive volumetric pan-aortic plaque assessment. We propose a novel means of more accurately assessing plaque volume across whole aortic segments using computed tomography angiography (CTA) imaging. Sixty patients who underwent CTA prior to trans-catheter aortic valve implantation were included in this analysis. Specialized software analysis (3mensio Vascular™, Pie Medical, Maastricht, Netherlands) was used to reconstruct images using a centerline approach, thus creating true cross-sectional aortic images, akin to those images produced with intravascular ultrasonography. Following aortic segmentation (from the aortic valve to the renal artery origin), atheroma areas were measured across multiple contiguous evenly spaced (10 mm) cross-sections. Percent atheroma volume (PAV), total atheroma volume (TAV) and calcium score were calculated. In our populations (age 79.9 ± 8.5 years, male 52 %, diabetes 27 %, CAD 84 %, PVD 20 %), mean ± SD number of cross sections measured for each patient was 35.1 ± 3.5 sections. Mean aortic PAV and TAV were 33.2 ± 2.51 % and 83,509 ± 17,078 mm(3), respectively. Median (IQR) calcium score was 1.5 (0.7-2.5). Mean (SD) inter-observer coefficient of variation and agreement for plaque area among 4 different analysts was 14.1 (5.4), and the mean (95 % CI) Lin's concordance correlation coefficient was 0.79 (0.62-0.89), effectively simulating a Core Laboratory scenario. We provide an initial validation of cross-sectional volumetric aortic atheroma assessment using CTA. This proposed methodology highlights the potential for utilizing non-invasive aortic plaque imaging for risk prediction across a range of clinical scenarios.

Practical application of coronary imaging devices in cardiovascular intervention

The significant morbidity and mortality associated with coronary artery disease has spurred the development of intravascular imaging devices to optimize the detection and assessment of coronary lesions and percutaneous coronary interventions. Intravascular ultrasound (IVUS) uses reflected ultrasound waves to quantitatively and qualitatively assess lesions; integrated backscatter and virtual histology IVUS more precisely characterizes plaque composition; angioscopy directly visualize thrombus and plaque; optical coherence tomography using near-infrared (NIR) light with very high spatial resolution provides more accurate images; and the recently introduced NIR spectroscopy identifies chemical components in coronary artery plaques based on differential light absorption in the NIR spectrum. This article reviews usefulness of these devices and hybrids thereof.

Pathophysiology of coronary artery disease leading to acute coronary syndromes

Acute myocardial infarction (AMI) and sudden cardiac death (SCD) are among the most serious and catastrophic of acute cardiac disorders, accounting for hundreds of thousands of deaths each year worldwide. Although the incidence of AMI has been decreasing in the US according to the American Heart Association, heart disease is still the leading cause of mortality in adults. In most cases of AMI and in a majority of cases of SCD, the underlying pathology is acute intraluminal coronary thrombus formation within an epicardial coronary artery leading to total or near-total acute coronary occlusion. This article summarizes our current understanding of the pathophysiology of these acute coronary syndromes and briefly discusses new approaches currently being researched in an attempt to define and ultimately reduce their incidence.

The relationship among extent of lipid-rich plaque, lesion characteristics, and plaque progression/regression in patients with coronary artery disease: a serial near-infrared spectroscopy and intravascular ultrasound study

AIMS

To evaluate the relationship between lipid content and plaque morphometry as well as the process of lesion progression and regression in patients with significant coronary artery disease.

METHODS AND RESULTS

The present study, using data from the YELLOW trial, was conducted in patients having significant coronary lesions (fractional flow reserve <0.8) who underwent serial intravascular ultrasound (IVUS) and near-infrared spectroscopy (NIRS) at baseline and after 7 weeks. For each coronary plaque (≥50% plaque burden that was ≥5 mm in length), we evaluated plaque characteristics and the extent of lipid-rich plaque [LRP, defined as the 4 mm long segment with the maximum lipid-core burden index (maxLCBI4 mm)] on NIRS. Among 66 patients (age 63.0 ± 10.1 years; 82% statin use at baseline), 94 plaques were identified. The extent of LRP at baseline was positively correlated with IVUS plaque burden (r = 0.317, P = 0.002). A large LRP (maxLCBI4 mm ≥500) was present only in plaques with a large plaque burden (≥70%). Multivariate analysis demonstrated that plaque burden was the best predictor of the extent of LRP (P < 0.001). In lesions with a large plaque burden and a large amount of LRP at baseline, a reduction in LRP was seen in all lesions in patients receiving intensive statin therapy (P = 0.004) without a significant change in plaque burden.

CONCLUSIONS

Coronary lesions containing a large amount of LRP also had a large plaque burden. Short-term regression of LRP (without a change in plaque burden) was observed mainly in plaques with a large plaque burden and a large amount of LRP at baseline.

CLINICAL TRIAL REGISTRATION

http://www.clinicaltrials.gov. Unique identifier: NCT01567826.

Mapping intravascular ultrasound controversies in interventional cardiology practice

Intravascular ultrasound is a catheter-based imaging modality that was developed to investigate the condition of coronary arteries and assess the vulnerability of coronary atherosclerotic plaques in particular. Since its introduction in the clinic 20 years ago, use of intravascular ultrasound innovation has been relatively limited. Intravascular ultrasound remains a niche technology; its clinical practice did not vastly expand, except in Japan, where intravascular ultrasound is an appraised tool for guiding percutaneous coronary interventions. In this qualitative research study, we follow scholarship on the sociology of innovation in exploring both the current adoption practices and perspectives on the future of intravascular ultrasound. We conducted a survey of biomedical experts with experience in the technology, the practice, and the commercialization of intravascular ultrasound. The collected information enabled us to map intravascular ultrasound controversies as well as to outline the dynamics of the international network of experts that generates intravascular ultrasound innovations and uses intravascular ultrasound technologies. While the technology is praised for its capacity to measure coronary atherosclerotic plaque morphology and is steadily used in clinical research, the lack of demonstrated benefits of intravascular ultrasound guided coronary interventions emerges as the strongest factor that prevents its expansion. Furthermore, most of the controversies identified were external to intravascular ultrasound technology itself, meaning that decision making at the industrial, financial and regulatory levels are likely to determine the future of intravascular ultrasound. In light of opinions from the responding experts', a wider adoption of intravascular ultrasound as a stand-alone imaging modality seems rather uncertain, but the appeal for this technology may be renewed by improving image quality and through combination with complementary imaging modalities.

Clinical utility of intravascular imaging and physiology in coronary artery disease

Intravascular imaging and physiology techniques and technologies are moving beyond the framework of research to inform clinical decision making. Currently available technologies and techniques include fractional flow reserve; grayscale intravascular ultrasound (IVUS); IVUS radiofrequency tissue characterization; optical coherence tomography, the light analogue of IVUS; and near-infrared spectroscopy that detects lipid within the vessel wall and that has recently been combined with grayscale IVUS in a single catheter as the first combined imaging device. These tools can be used to answer questions that occur during daily practice, including: Is this stenosis significant? Where is the culprit lesion? Is this a vulnerable plaque? What is the likelihood of distal embolization or periprocedural myocardial infarction during stent implantation? How do I optimize acute stent results? Why did thrombosis or restenosis occur in this stent? One of the legacies of coronary angiography is to presume that one technique will answer all of these questions; however, that often has been proved inaccurate in contemporary practice.