Morphological Characteristics of Culprit Atheromatic Plaque Are Associated With Coronary Flow After Thrombolytic Therapy

Correlates of Residual Thrombus Burden in Successfully Thrombolysed Patients of ST-Elevation Myocardial Infarction Receiving Dual Anti-Platelet Therapy

Background

Variable residual thrombus ranging from minimal to a large thrombus is seen in the culprit vessel after successful thrombolysis in ST-elevation myocardial infarction (STEMI). Factors associated with residual thrombus in thrombolysed patients are poorly understood. The objective of our study was to determine the correlates of residual thrombus burden in successfully thrombolysed STEMI patients receiving dual antiplatelet therapy.

Methods

In this prospective observational study of 60 successfully thrombolysed STEMI patients receiving dual antiplatelet therapy, various clinical and coronary angiographic features like residual thrombus burden, residual stenosis, and thrombolysis in myocardial infarction (TIMI) flow grade in the infarct-related artery were evaluated.

Results

Out of 60 patients, 49 and 11 patients, respectively, had low and high thrombus burden. Thirty-seven (75.5%) patients amongst low-grade thrombus had TIMI 3 flow, whereas seven (63.6%) amongst high thrombus burden had TIMI 2 flow indicating an association between residual thrombus burden and TIMI flow grade, which was statistically significant (p=0.009). Further, amongst the 39 patients who were 45 years old, a statistically significant association of age and residual stenosis (p = 0.039) was observed.

Conclusion

In successfully thrombolysed STEMI patients receiving dual antiplatelet therapy, there is an inverse correlation between residual thrombus burden and TIMI flow grade with high-grade residual thrombus associated with more frequent low TIMI flow. Further, significant residual stenosis is more common in patients older than 45 years of age, underscoring the necessity for invasive evaluation after successful thrombolysis.

Association of culprit lesion plaque characteristics with flow restoration post-fibrinolysis in ST-segment elevation myocardial infarction: an intravascular ultrasound-virtual histology study

Background

Not every patient achieves normal coronary flow following fibrinolysis in STEMI (ST-segment elevation myocardial infarction). The culprit lesion plaque characteristics play a prominent role in the coronary flow before and during percutaneous coronary intervention. The main purpose was to determine the culprit lesion plaque features by virtual histology-intravascular ultrasound (VH-IVUS) in patients with STEMI following fibrinolysis in relation to baseline coronary angiogram TIMI (thrombolysis in myocardial infarction) flow. Pre-intervention IVUS was undertaken in 61 patients with STEMI after successful fibrinolysis. After the coronary angiogram, they were separated into the TIMI1–2 flow group (n = 31) and TIMI 3 flow group (n = 30). Culprit lesion plaque composition was evaluated by VH-IVUS.

Results

On gray-scale IVUS, the lesion external elastic membrane cross-sectional area (EEM CSA) was significantly higher in the TIMI 1–2 groups as compared to the TIMI 3 group (15.71 ± 3.73 mm² vs 13.91 ± 2.94 mm², p = 0.041) with no significant difference in plaque burden (82.42% vs. 81.65%, p = 0.306) and plaque volume (108.3 mm³ vs. 94.3 mm³, p = 0.194). On VH-IVUS, at the minimal luminal area site (MLS), the fibrous area (5.83 mm² vs. 4.37 mm², p = 0.024), necrotic core (NC) area (0.95 mm² vs. 0.59 mm², p < 0.001), and NC percentage (11% vs. 7.1%, p = 0.024) were higher in the TIMI 1–2 groups in contrast to the TIMI 3 group. The absolute necrotic core (NC) volume (8.3 mm³ vs. 3.65 mm³, p < 0.001) and NC percentage (9.3% vs. 6.0%, p = 0.007) were significantly higher in the TIMI 1–2 groups as compared to the TIMI 3 group. Absolute dense calcium (DC) volume was higher in TIMI 1–2 groups with a trend towards significance (1.0 mm³ vs.0.75 mm³, p = 0.051). In multivariate analysis, absolute NC volume was the only independent predictor of TIMI 1–2 flow (odds ratio = 1.561; 95% CI 1.202–2.026, p = 0.001). Receiver operating characteristic curves showed absolute NC volume has best diagnostic accuracy (AUC = 0.816, p < 0.001) to predict TIMI 1–2 flow with an optimal cutoff value of 4.5 mm³ with sensitivity and specificity of 79% and 61%, respectively.

Conclusions

This study exemplifies that the necrotic core component of the culprit lesion plaque in STEMI is associated with the coronary flow after fibrinolysis. The absolute necrotic core volume is a key determinant of flow restoration post-fibrinolysis and aids in prognostication of less than TIMI 3 flow.

Systemic and local factors associated with reduced thrombolysis in myocardial infarction flow in ST-segment elevation myocardial infarction patients with plaque erosion detected by intravascular optical coherence tomography

Local factors of plaque rupture (e.g. lipid burden) are related to preprocedural thrombolysis in myocardial infarction (TIMI) flow grade during primary percutaneous coronary intervention (PCI). However, the pathological mechanism differs between plaque erosion and rupture. We aimed to identify the factors associated with reduced TIMI flow in plaque erosion. A total of 329 ST-segment elevation myocardial infarction (STEMI) patients with optical coherence tomography (OCT) identified plaque erosion were divided into 2 groups by preprocedural TIMI flow grade [TIMI 0-1 group (n = 219) and TIMI 2-3 group (n = 110)]. Patients in TIMI 0-1 group were older (age > 50 years, 68.5% vs. 51.8%, P = 0.003), and had more diabetes mellitus (18.3% vs. 8.2%, P = 0.015). Plaque erosion with TIMI flow 0-1 was less frequently located in the left anterior descending artery (LAD, 58.4% vs. 72.7%, P = 0.011), but more frequently located in the right coronary artery (RCA, 34.2% vs. 7.3%, P = 0.001) than those with TIMI flow 2-3. TIMI 0-1 group had more lipid plaques (53.9% vs. 41.8%, P = 0.039), macrophage accumulation (59.8% vs. 41.8%, P = 0.002), and calcification (34.2% vs. 21.8%, P = 0.020). In the multivariable analysis, age > 50 years, diabetes mellitus, RCA location, and macrophage accumulation were the independent predictors of reduced TIMI flow grade in STEMI patients with plaque erosion. Systemic factors (older age and diabetes mellitus) and local factors (RCA location and macrophage accumulation) were independently associated with reduced coronary flow in STEMI patients with plaque erosion. CLINICAL TRIAL REGISTRATION : ClinicalTrials.gov NCT03084991 May 17, 2017 (retrospectively registered).

Evaluation of stent length on the outcome of ST-segment elevation myocardial infarction receiving primary percutaneous coronary intervention

BACKGROUND

A longer stent length is known to be a predictor of adverse events after a percutaneous coronary intervention (PCI). However, the evaluation of the stent length on the outcome of ST-segment elevation myocardial infarction (STEMI) patients is not enough.

PATIENTS AND METHODS

A total of 686 STEMI patients who underwent primary PCI were divided into four groups according to the total stent length as follows: short (<18 mm, n=183), lower-medium (18-23 mm, n=256), upper-medium (24-31 mm, n=155), and long (≥32 mm, n=92). We compared the all-cause mortality, major adverse cardiovascular events (MACEs; composite of cardiovascular death, myocardial infarction, and stroke after discharge), target lesion revascularization, and target vessel revascularization with a median follow-up of 1213 days among these four groups.

RESULTS

There were no significant differences in MACEs (10.4% in the short, 7.0% in the lower-medium, 6.5% in the upper-medium, 7.6% in the long, P=0.633) among the different stent length groups. The all-cause mortality, target lesion revascularization, and target vessel revascularization also did not differ among the four groups. In the drug-eluting stent (n=237) and bare-metal stent subgroups (n=449), all outcomes were comparable among the groups. However, in the diabetes subgroup (n=265), the rate of MACEs was higher in the long group than in the other groups, although the difference was not significant (6.6% in the short, 9.6% in the lower-medium, 3.4% in upper-medium, 16.7% in long group, P=0.095).

CONCLUSION

A long stent length was not associated with adverse clinical outcomes in STEMI patients who underwent primary PCI.

Plaque erosion versus rupture characterization by optical frequency domain imaging before and after coronary stenting following successful fibrinolysis for ST-segment elevation myocardial infarction

Intracoronary thrombus burden affects the quality of myocardial reperfusion in the setting of ST-elevation myocardial infarction (STEMI). We aimed to study the characteristics of the plaque and thrombus assessed by intracoronary optical frequency domain imaging (OFDI) according to the presence of plaque rupture or erosion in STEMI patients treated with successful fibrinolysis. Pre-stenting thrombus and post-stenting atherothrombotic burden were compared between plaque rupture and erosion. Twenty-seven consecutive patients were included: 17 (63%) had OFDI-plaque rupture and 10 (37%) had OFDI-erosion. Thrombus volume and burden were significantly higher in case of rupture compared to erosion at baseline (13.4 ± 18.4 vs 2.8 ± 2.3 mm³; p = 0.03 and 33.8 ± 17.5 vs 17.5 ± 9.9%; p = 0.007, respectively). In the rupture group, the core of the thrombus consisted dominantly of red thrombus evenly distributed along the entire culprit plaque. In the erosion group, it consisted dominantly of white thrombus with a focal distribution near the minimal lumen area zone. After stenting, the atherothrombotic volume, burden and its distribution, as well as angiographic estimators of myocardial reperfusion were similar between groups. Our study showed that pre-PCI thrombus amount, typesetting and distribution are mainly linked to the underlying mechanism of STEMI. After stenting, the atherothrombotic burden and its distribution were similar between the groups.

Tissue characterization and phenotype classification in patients presenting with acute myocardial infarction: Insights from the iWonder study

OBJECTIVES

We sought to assess a new modality of radiofrequency intravascular ultrasound (IVUS) called iMAP-IVUS (Boston Scientific, Santa Clara, California) during the evaluation of patients presenting with high-risk acute coronary syndromes.

BACKGROUND

There are limited data on plaque tissue characterization and phenotype classification using iMAP-IVUS.

METHODS

In the iWonder study patients presenting with ST-elevation myocardial infarction (STEMI) or non-STEMI underwent three-vessel grayscale IVUS and iMAP-IVUS tissue characterization prior to percutaneous intervention. In total 385 lesions from 100 patients were divided into culprit (n = 100) and nonculprit (n = 285) lesions. Lesion phenotype was classified as (i) thin-cap fibroatheroma (iMAP-derived TCFA); (ii) thick-cap fibroatheroma; (iii) pathological intimal thickening; (iv) fibrotic plaque; and (v) fibrocalcific plaque.

RESULTS

Culprit lesions had smaller minimum lumen cross-sectional area (MLA) with greater plaque burden compared to non-culprit lesions. Volumetric analysis showed that culprit lesions had longer length and larger vessel and plaque volumes compared to non-culprit lesions. iMAP-IVUS revealed that culprit lesions presented more NC and fibrofatty volume, both at lesion level and at the MLA site (all P < 0.001). Any fibroatheroma was more frequently identified in culprit lesions compared with non-culprit lesions (93% vs. 78.9%, P = 0.001), anywhere within the lesion 19.0%, P < 0.001) as well as at the MLA site (18.0% vs. 9.5%, P = 0.07).

CONCLUSIONS

Three-vessel radiofrequency iMAP-IVUS demonstrated a greater plaque burden and higher prevalence of any fibroatheroma as well as iMAP-derived TCFAs in culprit versus non-culprit lesions in patients presenting with STEMI or non-STEMI undergoing percutaneous coronary intervention. © 2017 Wiley Periodicals, Inc.

Matrix Metalloproteinase-9 as a Marker for Plaque Rupture and a Predictor of Adverse Clinical Outcome in Patients with Acute Coronary Syndrome: An Optical Coherence Tomography Study

OBJECTIVES

The present study sought to clarify the relationship between matrix metalloproteinase-9 (MMP-9) levels and plaque morphology demonstrated by optical coherence tomography (OCT), and to examine their prognostic impacts in patients with acute coronary syndrome (ACS).

METHODS

MMP-9 levels were measured for patients with ACS (n = 249). Among 249 patients, 120 with evaluable OCT images were categorized into patients with ruptured plaques (n = 65) and those with nonruptured plaques (n = 55) on the basis of culprit lesion plaque morphology demonstrated by OCT.

RESULTS

MMP-9 levels on admission were significantly higher in the rupture group than in the nonrupture group (p = 0.029). Although creatine kinase-MB (CK-MB) on admission was comparable between the groups, peak CK-MB was higher in the rupture group than in the nonrupture group (p < 0.001). By receiver operating characteristic curve analysis, the optimal cut-off value of MMP-9 to detect ruptured plaques was 65.5 ng/ml (p = 0.029). There was a nonstatistically significant trend toward increased cardiac death at 2 years (5.9 vs. 1.0%, p = 0.059) in patients with high MMP-9 (≥65.5 ng/ml) compared to those with low MMP-9 (<65.5 ng/ml).

CONCLUSIONS

MMP-9 can differentiate ACS with ruptured plaques from nonruptured plaques, and MMP-9 may be a valuable predictor of long-term cardiac mortality in patients with ACS reflecting plaque rupture.

Optical Coherence Tomography For the Detection of the Vulnerable Plaque

Morphological characteristics of the atheromatous plaque have been associated with the development of plaque rupture and the pathogenesis of acute coronary syndromes (ACS). Plaques with a specific morphological phenotype that are at high risk of causing ACS are called vulnerable plaques, and can be identified in vivo through the use of intracoronary imaging. Optical coherence tomography (OCT) is a high-resolution intravascular imaging modality that enables detailed visualization of atheromatous plaques. Consequently, OCT is a valuable research tool for examining the role of morphological characteristics of atheromatous plaques in the progression of coronary artery disease and plaque destabilisation, which leads to the clinical manifestation of ACS. This article summarises the pathophysiological insights obtained by OCT imaging in the formation and rupture of the vulnerable plaque.

Comparison of plaque characteristics in narrowings with ST-elevation myocardial infarction (STEMI), non-STEMI/unstable angina pectoris and stable coronary artery disease (from the ADAPT-DES IVUS Substudy)

Assessment of Dual Antiplatelet Therapy With Drug-Eluting Stents (ADAPT-DES) was a prospective, multicenter registry of 8,582 consecutive stable and unstable patients who underwent percutaneous coronary intervention using a drug-eluting stent. We sought to identify key morphologic features leading to ST-segment elevation myocardial infarction (STEMI) versus non-STEMI (NSTEMI) or unstable angina pectoris (UA) versus stable coronary artery disease (CAD) presentation. In the prespecified grayscale and virtual histology (VH) substudy of ADAPT-DES, preintervention imaging identified 676 patients with a single culprit lesion. The relation between lesion morphology and clinical presentation was compared among patients with (1) STEMI, (2) NSTEMI or UA, and (3) stable CAD. Intravascular ultrasound identified more plaque rupture and VH thin-cap fibroatheroma (TCFA) in STEMI lesions compared with NSTEMI/UA or stable CAD lesions; conversely, fibroatheromas appeared more often calcified with a thick fibrous cap in stable CAD. Minimum lumen cross-sectional area (MLA) was smaller with larger plaque burden and positive remodeling in STEMI lesions. Lesions with plaque rupture versus those without plaque rupture showed higher prevalence of VH-TCFA and larger plaque burden with positive remodeling, especially in patients with STEMI. Multivariate analysis showed that in the lesions with plaque rupture, plaque burden at the MLA site was the only independent predictor for STEMI (cutoff of plaque burden = 85%) and in lesions without plaque rupture, MLA was the only independent predictor for STEMI (cutoff of MLA = 2.3 mm(2)). In conclusion, culprit lesions causing STEMI have smaller lumen areas, greater plaque burden, and more plaque rupture or VH-TCFA compared with NSTEMI/UA or stable CAD; in lesions with plaque rupture, only plaque burden predicted STEMI, and in lesions without plaque rupture, only MLA area predicted STEMI.

Differences determined by optical coherence tomography volumetric analysis in non-culprit lesion morphology and inflammation in ST-segment elevation myocardial infarction and stable angina pectoris patients

BACKGROUND

While the current methodology for determining fibrous cap (FC) thickness of lipid plaques is based on manual measurements of arbitrary points, which could lead to high variability and decreased accuracy, it ignores the three-dimensional (3-D) morphology of coronary artery disease.

OBJECTIVE

To compare, utilizing optical coherence tomography (OCT) assessments, volumetric quantification of FC, and macrophage detection using both visual assessment and automated image processing algorithms in non-culprit lesions of STEMI and stable angina pectoris (SAP) patients.

METHODS

Lipid plaques were selected from 67 consecutive patients (1 artery/patient). FC was manually delineated by a computer-aided method and automatically classified into three thickness categories: FC < 65 μm (i.e., thin-cap fibroatheroma [TCFA]), 65-150 μm, and >150 μm. Minimum thickness, absolute categorical surface area, and fractional luminal area of FC were analyzed. Automated detection and quantification of macrophage was performed within the segmented FC.

RESULTS

A total of 5,503 cross-sections were analyzed. STEMI patients when compared with SAP patients had more absolute categorical surface area for TCFA (0.43 ± 0.45 mm(2) vs. 0.15 ± 0.25 mm(2) ; P = 0.011), thinner minimum FC thickness (31.63 ± 17.09 µm vs. 47.27 ± 26.56 µm, P = 0.012), greater fractional luminal area for TCFA (1.65 ± 1.56% vs. 0.74 ± 1.2%, P = 0.046), and greater macrophage index (0.0217 ± 0.0081% vs. 0.0153 ± 0.0045%, respectively, P < 0.01).

CONCLUSION

The novel OCT-based 3-D quantification of the FC and macrophage demonstrated thinner FC thickness and larger areas of TCFA coupled with more inflammation in non-culprit sites of STEMI compared with SAP.

Impact of counterbalance between macrophage migration inhibitory factor and its inhibitor Gremlin-1 in patients with coronary artery disease

OBJECTIVE

Monocyte infiltration is a critical step in the pathophysiology of plaque instability in coronary artery disease (CAD). Macrophage migration inhibitory factor (MIF) is involved in atherosclerotic plaque progression and instability leading to intracoronary thrombosis. Gremlin-1 (Grem1) has been recently identified as endogenous inhibitor of MIF. To date there are no data on the clinical impact of this interaction in cardiovascular patients.

METHODS AND RESULTS

Plasma levels of MIF and Grem1 were determined by enzyme-linked immunoassay in patients with acute coronary syndromes (ACS, n = 120; stable CAD, n = 166 and healthy control subjects, n = 25). MIF levels were significantly increased in ACS compared to stable CAD and healthy control (ACS: median 2.85; IQR 3.52 ng/ml; versus SAP: median 1.22; IQR 2.99 ng/ml; versus healthy control: median 0.10; IQR 0.09 ng/ml, p < 0.001). Grem1 levels were significantly higher in ACS and stable CAD patients compared to healthy control (ACS: median 211.00; IQR 130.47 ng/ml; SAP: median 220.20; IQR 120.93 ng/ml, versus healthy control: median 90.57; IQR 97.68 ng/ml, p < 0.001). Grem1/MIF ratio was independently associated with ACS, whereas the single parameters were not associated with the presence of ACS. Furthermore, Grem1/MIF ratio was associated with angiographic signs of intracoronary thrombi and severity of thrombus burden.

CONCLUSION

These novel findings suggest a potential role of Grem1/MIF ratio to indicate acuity of CAD and the grade of plaque stability. Prospective angiographic cohort studies involving plaque imaging techniques are warranted to further characterize the prognostic role of this novel risk marker in CAD patients.

Evolution of intravascular assessment of coronary anatomy and physiology: from ultrasound imaging to optical and flow assessment

The fact that coronary angiography has limitations in terms of precise estimation and progression of atherosclerosis has been partially overcome during the last years by the use of new techniques. Catheter-based invasive modalities are of a profound clinical importance in regard to accurate assessment of coronary anatomy and physiology and the choice of the appropriate treatment strategy for each patient. Also their potential in clinical investigation projects is of great interest. This current review summarizes the basic principles of these methodologies and evidently highlights not only their use in clinical practice but also their contribution in clinical outcomes.

Subsequent development of fibroatheromas with inflamed fibrous caps can be predicted by intracoronary near infrared spectroscopy

OBJECTIVE

To prospectively evaluate whether the development of fibroatheromas exhibiting features of potential instability can be detected and predicted by serial invasive imaging.

METHODS AND RESULTS

Multivessel intravascular ultrasound and near infrared spectroscopy (NIRS) were performed in diabetic/hypercholesterolemic pigs 3, 6, and 9 months after induction. Animals were euthanized at 9 months and histological/immunohistochemical evaluation of the arteries was performed (n=304 arterial segments). Intravascular ultrasound demonstrated, over time, a progressive increase in plaque + media and necrotic core areas and positive vascular remodeling. By histology, NIRS+ lesions were significantly more likely to be a high-risk fibroatheroma (P=0.0001) containing larger plaque (P<0.0001) and necrotic core areas (P<0.0019) and thinner fibrous caps (P=0.04). NIRS + fibroatheromas possessed a greater concentration of inflammatory cells demonstrating protease activity (P=0.006), and proliferating (P=0.016), and apoptotic cells (P=0.04) within the fibrous cap. Eighty-eight percent of NIRS+ lesions at 3 and 6 months subsequently developed into a fibroatheroma at 9 months (P<0.01). By multivariate analysis NIRS positivity at 6 months predicted the subsequent presence of a fibroatheroma at 9 months (P=0.005; odds ratio, 2.71).

CONCLUSIONS

The future development of inflamed fibroatheromas with thinner fibrous caps, greater plaque, and necrotic core areas, and posessing characteristics of increased plaque instability were detected by intravascular ultrasound/NIRS imaging.

Optical coherence tomography: from research to practice

Optical coherence tomography (OCT) is a high-resolution imaging technique with great versatility of applications. In cardiology, OCT has remained hitherto as a research tool for characterization of vulnerable plaques and evaluation of neointimal healing after stenting. However, OCT is now successfully applied in different clinical scenarios, and the introduction of frequency domain analysis simplified its application to the point it can be considered a potential alternative to intravascular ultrasound for clinical decision-making in some cases. This article reviews the use of OCT for assessment of lesion severity, characterization of acute coronary syndromes, guidance of intracoronary stenting, and evaluation of long-term results.