Histopathologic validation of the intravascular ultrasound diagnosis of calcified coronary artery nodules

Clinical outcomes of percutaneous coronary intervention for severely calcified lesions: comparison between the morphologies of severely calcified coronary lesions

Existing studies evaluating the comparison of clinical outcome of percutaneous coronary intervention (PCI) for severe calcified coronary lesions are limited, and the clinical outcomes of PCI for different morphologies of calcified lesions are controversial. Overall, consecutive 576 lesions with severe calcification that were treated with PCI from 2010 to 2021 at Nagoya Heart Center were investigated. All lesions were assessed using invasive coronary angiogram (CAG) or computed tomography-CAG at 12 months after DES implantation. We divided the patients into three groups based on the results of intravascular ultrasound (IVUS) imaging (concentric calcified lesion [CC] n = 273, eccentric calcified lesion [EC] n = 217, calcified nodule [CN] n = 86). The clinical and angiographic outcomes of each group were investigated retrospectively to compare the prognosis between the three groups and identify predictive factors for the device-oriented composite end points (DoCE). There were no differences in patient characteristics among the three groups, except that there were significantly more patients on dialysis in the CN group. The incidence of DoCE was significantly higher in the CN group than in the other groups (CC; 18.3% vs. EC; 23.5% vs. CN; 36.0%; Log-Rank test; p = 0.001). Cox regression analysis showed that the independent predictors of DoCE were CN, insulin use, hemodialysis, right coronary artery lesions, and calcium cracks. The incidence of DoCE was significantly higher in the CN group. Calcium cracks are crucial for improving outcomes in severely calcified lesions, being key predictors of DoCE.

Calcified Nodule in Percutaneous Coronary Intervention: Therapeutic Challenges

Calcified nodules (CNs) are among the most challenging lesions to treat in contemporary percutaneous coronary intervention. CNs may be divided into 2 subtypes, eruptive and noneruptive, which have distinct histopathological and prognostic features. An eruptive CN is a biologically active lesion with a disrupted fibrous cap and possibly adherent thrombus, whereas a noneruptive CN has an intact fibrous cap and no adherent thrombus. The use of intravascular imaging may allow differentiation between the 2 subtypes, thus potentially guiding treatment strategy. Compared with noneruptive CNs, eruptive CNs are more likely to be deformable, resulting in better stent expansion, but are paradoxically associated with worse clinical outcomes, in part because of their frequent initial presentation as an acute coronary syndrome and subsequent reprotrusion of the CN into the vessel lumen through the stent struts. Pending the results of ongoing studies, a tailored therapeutic approach based on the distinct features of the different CNs may be of value.

Coronary artery calcification: concepts and clinical applications

Vascular calcification is an important hallmark of atherosclerosis. Coronary artery calcification (CAC) implies the presence of coronary artery disease (CAD), irrespective of risk factors or symptoms, is concomitant with the development of advanced atherosclerosis. Coronary thrombosis is the most common clinical end event leading to acute coronary syndrome (ACS). The least common type of pathology associated with thrombosis is the calcified nodule (CN). It usually occurs in elderly patients with severely calcified and tortuous arteries. The prevalence of calcified nodules in patients with ACS may be underestimated due to the lack of easily recognisable diagnostic methods. In this review, the authors will focus on the classification, clinical significance, pathogenesis, and diagnostic evaluation and treatment of CAC to further explore the clinical significance of CN.

Ostial right coronary artery lesion morphology and outcomes after treatment with drug-eluting stents

BACKGROUND

Outcomes after percutaneous coronary intervention (PCI) for de novo ostial right coronary artery (RCA) lesions are poor.

AIMS

We used intravascular ultrasound (IVUS) to clarify the morphological patterns of de novo ostial RCA lesions and their associated clinical outcome.

METHODS

Among 5,102 RCA IVUS studies, 170 de novo ostial RCA stenoses (within 3 mm from the aorto-ostium) were identified. These were classified as 1) isolated ostial lesions (no disease extending beyond 10 mm from the ostium and without a calcified nodule [CN]); 2) ostial CN, typically with diffuse disease (disease extending beyond 10 mm); and 3) ostial lesions with diffuse disease but without a CN. The primary outcome was target lesion failure (TLF: cardiac death, target vessel myocardial infarction, definite stent thrombosis, and ischaemia-driven target lesion revascularisation).

RESULTS

The prevalence of an isolated ostial lesion was 11.8% (n=20), 47.6% (n=81) were ostial CN, and 40.6% (n=69) were ostial lesions with diffuse disease. Compared to ostial lesions with diffuse disease, isolated lesions were more common in women (75.0% vs 42.0%; p=0.01), and CN were associated with older age (median [first, third quartile] 76 [70, 83] vs 69 [63, 81] years old; p=0.002). The Kaplan-Meier rate of TLF at 2 years was significantly higher in patients with CN (21.6%) compared to diffuse lesions (8.2%) (p=0.04), and patients with isolated lesions had no events. A multivariable Cox proportional hazard model revealed that CN were significantly associated with TLF (hazard ratio 6.63, 95% confidence interval: 1.28-34.3; p=0.02).

CONCLUSIONS

Ostial RCA lesions have specific morphologies - detectable by IVUS - that may be associated with long-term clinical outcomes.

SCAI Expert Consensus Statement on the Management of Calcified Coronary Lesions

The prevalence of calcification in obstructive coronary artery disease is on the rise. Percutaneous coronary intervention of these calcified lesions is associated with increased short-term and long-term risks. To optimize percutaneous coronary intervention results, there is an expanding array of treatment modalities geared toward calcium modification prior to stent implantation. The Society for Cardiovascular Angiography and Interventions, herein, puts forth an expert consensus document regarding methods to identify types of calcified coronary lesions, a central algorithm to help guide use of the various calcium modification strategies, tips for when using each treatment modality, and a look at future studies and trials for treating this challenging lesion subset.

Feasibility of rotational atherectomy in patients with acute coronary syndrome: favorable in-hospital outcomes and clinical importance of complexed coronary atherosclerosis

The feasibility of rotational atherectomy (RA) during percutaneous coronary intervention (PCI) in patients who present with acute coronary syndrome (ACS) remains fully unsettled. We retrospectively evaluated 198 consecutive patients who underwent RA during PCI from 2009 to 2020. All patients underwent intracoronary imaging (intravascular ultrasound 96.5%, optical coherence tomography 9.1%, both 5.6%) during PCI. Patients who underwent RA during PCI were divided into two groups: ACS (n = 49; unstable angina pectoris, n = 27; non-ST-elevation myocardial infarction, n = 18, and ST-elevation myocardial infarction, n = 4) and chronic coronary syndrome (CCS) (n = 149). The RA procedural success rate was comparable between in the ACS and CCS groups (93.9 vs. 89.9%, P = 0.41). No significant differences were observed in procedural complications and in-hospital death between the groups. The incidence of major adverse cardiovascular event (MACE) after 2 years was significantly higher in ACS group compared with CCS group (38.7 vs. 17.4%, log-rank P = 0.002). Multivariable Cox regression analysis identified SYNTAX score or CABG SYNTAX score > 22 (hazard ratio (HR) 2.66, 95% confidence interval (CI) 1.40-5.06, P = 0.002) and mechanical circulatory support during the procedure (HR 2.61, 95% CI 1.21-5.59, P = 0.013) as predictors of MACE at 2 years, but not ACS on index admission (HR 1.58, 95% CI 0.84-2.99, P = 0.151). RA procedure is feasible as a bail-out strategy for ACS lesions. However, more complexed coronary atherosclerosis and mechanical circulatory support during RA procedure, but no ACS lesions were associated with worse mid-term clinical outcomes.

Lifetime management of severely calcified coronary lesions: the treatment algorithm focused on the shape of calcification

The concept of lifetime management has not been discussed in the field of percutaneous coronary intervention (PCI), because the durability of drug-eluting stent (DES) is considered to be long enough for most patients. Furthermore, even if in-stent restenosis occurs, the treatment for in-stent restenosis is simple in most cases. On the other hand, the long-term clinical outcomes after DES implantation are worse in severely calcified coronary lesions than in non-calcified lesions. Moreover, the treatment for in-stent calcified restenosis or restenosis due to stent underexpansion is not simple. The concept of lifetime management of severely calcified lesions may be necessary like that of aortic stenosis. Recently, several algorithms have been published in PCI to severely calcified lesions, partly because of the emergence of IVL. These algorithms focus on the selection of cracking and debulking devices for the preparation of stenting. However, the optimal stent expansion does not guarantee the long-term patency, when the target lesion includes calcified nodules. Stent restenosis due to calcified nodules is difficult to manage. In this review article, we propose the algorithm for severely calcified lesions focused on the shape of calcification. We do not need to hesitate stenting when multiple cracks on circumferential calcification are observed by intravascular imaging devices. However, DCB may be an option as final device in some situations, when lifetime management of severely calcified lesions is considered.

Novel Imaging-Based Biomarkers for Identifying Carotid Plaque Vulnerability

Carotid artery disease has traditionally been assessed based on the degree of luminal narrowing. However, this approach, which solely relies on carotid stenosis, is currently being questioned with regard to modern risk stratification approaches. Recent guidelines have introduced the concept of the "vulnerable plaque," emphasizing specific features such as thin fibrous caps, large lipid cores, intraplaque hemorrhage, plaque rupture, macrophage infiltration, and neovascularization. In this context, imaging-based biomarkers have emerged as valuable tools for identifying higher-risk patients. Non-invasive imaging modalities and intravascular techniques, including ultrasound, computed tomography, magnetic resonance imaging, intravascular ultrasound, optical coherence tomography, and near-infrared spectroscopy, have played pivotal roles in characterizing and detecting unstable carotid plaques. The aim of this review is to provide an overview of the evolving understanding of carotid artery disease and highlight the significance of imaging techniques in assessing plaque vulnerability and informing clinical decision-making.

Intravascular Ultrasound in Vulnerable Plaque and Acute Coronary Syndrome

Vulnerable plaque plays a pivotal role in the pathogenesis of acute coronary syndrome (ACS), being responsible for most ACS. The concept of vulnerable plaque has evolved with advancements in basic and clinical investigations along with developments and rapid expansion of coronary imaging modalities. Intravascular ultrasound (IVUS) is the first widely applied clinical technology with sufficient tissue penetration and enables us to identify vulnerable plaque and comprehensively understand the pathophysiology of ACS. In this review, we summarize current clinical evidence established by IVUS and the recent advancements in our understanding of vulnerable plaque and its role in ACS management.

Characteristics and Pattern of Calcified Nodule and/or Nodular Calcification Detected by Intravascular Ultrasound on the Device-Oriented Composite Endpoint (DoCE) in Patients with Heavily Calcified Lesions Who Underwent Rotational Atherectomy-Assisted Percutaneous Coronary Intervention

Objectives

This study aimed to determine characteristics and pattern of a calcified nodule (CN) and/or nodular calcification (NC) detected by intravascular ultrasound (IVUS) on the device-oriented composite endpoint (DoCE) in patients with calcified lesions who underwent rotational atherectomy (RA)-assisted percutaneous coronary intervention (PCI).

Background

The characteristics and pattern of a CN and/or NC on clinical outcome remain unknown.

Methods

We retrospectively enrolled patients who underwent RA-assisted PCI at Siriraj Hospital during August 2016 to April 2020. Preprocedural IVUS imaging was mandatory. CN/NC was defined as convex shape of luminal surface and luminal side of calcium with protrusion into the coronary artery lumen as assessed by IVUS. The primary outcome was cumulative of DoCE, defined as the composite of cardiovascular death, myocardial infarction, and clinically-driven target lesion revascularization.

Results

Two hundred patients were included. Primary outcome occurred in 14%. The cumulative DoCE was significantly higher in the CN/NC group than that in the non-CN/NC group (20.7% vs. 8.8%, p = 0.022). CN/NC (p = 0.023) and MSA ≤ 5.5 mm² (p = 0.047) were correlated with a significantly higher cumulative DoCE. CN/NC was the independent predictor for the cumulative DoCE (HR = 2.96, 95% CI 1.08-8.11, p = 0.035). Pattern and characteristic of CN/NC have a prognostic value. Patients with an eccentric CN/NC had a significantly higher cumulative DoCE compared to those CN/NC with concentric calcification (p = 0.014).

Conclusion

The presence of a CN/NC in patients with heavily calcified lesions who underwent RA-assisted PCI was found to be associated with increased cumulative 5 year DoCE, especially in patients with an eccentric CN/NC. The clinical trial is registered with TCTR20210616001.

Impact of ultrasound reverberation in calcified coronary arteries: Intravascular ultrasound study

BACKGROUND AND AIMS

Intravascular ultrasound (IVUS) often allows us to observe reverberations behind calcification in percutaneous coronary intervention (PCI) to heavily calcified lesions. However, clinical significance of reverberations remains unknown. The aim of this study was to assess the impact of reverberations on stent expansion and clinical outcomes after PCI with rotational atherectomy (RA) to heavily calcified lesions.

METHODS

We considered 250 calcified lesions that underwent IVUS-guided PCI with RA. According to the number of reverberations (NR), those lesions were divided into the high NR (≥3) group (n = 36) and the low NR (≤2) group (n = 214). Stent expansion and the cumulative incidence of ischemia-driven target lesion revascularization (ID-TLR) were compared between the high and low NR groups.

RESULTS

The high NR group showed significantly smaller stent expansion rate than the low NR group (67.7% vs. 75.9%, respectively, p=0.02). The multivariate logistic regression analysis showed that high NR and calcified nodule were significantly associated with stent underexpansion. The incidence of ID-TLR was significantly higher in the high NR group than in the low NR group (p=0.03). In multivariate Cox hazard analysis, high NR and acute coronary syndrome were significantly associated with ID-TLR.

CONCLUSIONS

High NR was significantly associated with stent underexpansion and ID-TLR. When high NR was detected by IVUS, the PCI strategy was be planned carefully to avoid stent underexpansion. The follow-up program of the patients with high NR might need to be scheduled prudently because of the high risk of TLR.

Serum marker and CT characteristics of coronary calcified nodule assessed by intravascular ultrasound

Background

Calcified nodule (CN) is a type of potentially vulnerable plaque. Its formation mechanism remains unknown. This study was to assess serum marker and computed tomography angiography (CTA) characteristics of CN validated by intravascular ultrasound (IVUS).

Methods

Patients who underwent coronary CTA followed by invasive coronary angiography and IVUS were retrospectively analyzed. Serum levels of alkaline phosphatase (ALP), gamma-glutamyltransferase, and calcium were collected.

Results

IVUS detected 128 de novo calcified lesions in 79 patients with coronary artery disease (CAD). CNs were identified in 11.4% (9/79) of patients and 9.4% (12/128) of lesions. Compared with patients with non-nodular calcified plaques, CN patients had higher serum level of ALP (82.00 vs 65.00 U/L, P = 0.022) and total plaque volume (673.00 vs 467.50 mm3, P = 0.021). Multivariable analyses revealed that serum ALP level and total plaque volume were independently associated with the prevalence of CN in CAD patients with calcified plaques. At lesion level, the CN group had a higher frequency of moderate to heavy calcification on angiography (75.00% vs 40.52%, P = 0.017). In terms of CTA characteristics, plaques with CN had a more severe diameter stenosis (79.00% vs 63.00%, P = 0.007), higher plaque burden (85.40% vs 77.05%, P = 0.005), total plaque density (398.00 vs 283.50 HU, P = 0.008), but lower lipid percentage (14.65% vs 19.75%, P = 0.010) and fiber percentage (17.90% vs 25.65%, P = 0.011). Mean plaque burden is an independent predictor of the prevalence of CN in calcified plaques (odds ratio = 1.102, 95% confidence interval: 1.025–1.185, P = 0.009). The AUC is 0.753 (95% confidence interval: 0.615–0.890, P = 0.004). When using 84.85% as the best cutoff value, the diagnostic sensitivity and specificity of mean plaque burden for predicting the presence of CN within calcified plaques were 66.7% and 80.2%, respectively.

Conclusions

CN had different CTA imaging features from non-nodular coronary calcification. The presence of a CN was associated with a higher serum ALP level and plaque burden.

Prevalence and outcomes of stent thrombosis with in-stent calcified nodules: substudy from the REAL-ST registry

BACKGROUND

The relationship between in-stent calcified nodules (IS-CN) and second-generation drug-eluting stent (G2-DES) stent thrombosis (ST) remains uncertain.

AIMS

We aimed to evaluate the prevalence, clinical demographic and long-term clinical outcomes after G2-DES ST with IS-CN.

METHODS

The prespecified substudy of the REAL-ST registry (a retrospective, multicentre registry of patients with definite ST after first- and G2-DES implantation) enrolled patients who experienced definite G2-DES ST and who underwent pre-intervention intravascular ultrasound imaging at index ST events.

RESULTS

IS-CN was observed in 15 out of 118 (13%) definite G2-DES ST cases. The multiple logistic regression model demonstrated that haemodialysis (odds ratio [OR] 12.27, 95% confidence interval [CI]: 1.56-94.54; p=0.02), proximal or mid-right coronary artery lesions (OR 12.79, 95% CI: 1.78-92.13; p=0.01) and severe calcification (OR 13.01, 95% CI: 1.18-142.94; p=0.04) were independently associated with ST with IS-CN. The cumulative 5-year incidence of target lesion revascularisation (TLR) after ST was significantly higher in the IS-CN group than in the non-IS-CN group (p=0.02). Independent predictors of TLR after the index ST events were female sex (hazard ratio [HR] 3.05, 95% CI: 1.20-7.74; p=0.02), diabetes mellitus (HR 3.26, 95% CI: 1.26-8.41; p=0.01) and IS-CN (HR 3.07, 95% CI: 1.16-8.14; p=0.02).

CONCLUSIONS

IS-CN may be one of the underlying mechanisms of G2-DES ST. Notably, IS-CN was associated with a higher TLR rate after the index ST events, suggesting the need for careful clinical follow-up of ST patients with IS-CN.

Clinical Outcomes and Unique Restenosis of Calcified Nodule in Heavily Calcified Coronary Artery

AIMS

Calcified nodule (CN) has been known as the advanced stage of coronary calcification. However, clinical outcomes following percutaneous coronary intervention (PCI) to CN remain unknown. This study aimed to compare clinical outcomes, including target lesion revascularization (TLR), between calcified coronary lesions with and without CN.

METHODS

Two hundred forty-nine lesions undergoing intravascular ultrasound-guided PCI with rotational atherectomy (RA) were enrolled and divided into the CN group (n=100) and the non-CN group (n=149) according to the presence of CN. The cumulative incidence of clinically driven TLR (CD-TLR) and the reasons for CD-TLR were compared between the CN and non-CN groups.

RESULTS

The incidence of CD-TLR was significantly higher in the CN group than in the non-CN group. In the landmark analysis at 1 year, the CN group showed a significantly higher incidence of CD-TLR within 1 year. However, the incidence of CD-TLR beyond 1 year was numerically lower in the CN group than in the non-CN group. In the multivariate Cox hazard model, CN was significantly associated with CD-TLR. In the CN group, in-stent CN was the major reason for CD-TLR (52%) and was observed mainly within 1 year (90%).

CONCLUSIONS

In the heavily calcified lesions requiring RA, CN was the factor associated with the higher rate of CD-TLR especially within 1 year. The timing of CD-TLR in lesions with CN may indicate that the process of CN protruding through the struts was progressed monthly.

High-definition intravascular ultrasound versus optical frequency domain imaging for the detection of calcium modification and fracture in heavily calcified coronary lesion

While optical frequency domain imaging (OFDI) can delineate calcium modification and fracture, the capability of high-definition intravascular ultrasound (HD-IVUS) for detecting these remains unclear. This study evaluated diagnostic accuracy of HD-IVUS for assessing calcium modification and fracture as compared to OFDI. HD-IVUS and OFDI were used during orbital or rotational atherectomy procedures conducted for 21 heavily calcified coronary lesions in 19 patients. With OFDI assessment used as the gold standard, diagnostic accuracies of HD-IVUS for calcium modification and fracture were compared every 1 mm to the matched pre-stenting images (n = 1129). Calcium modification, as assessed by OFDI, was defined as polished and concave-shaped calcium. For HD-IVUS, calcium modification was defined as the presence of reverberation with concave-shaped calcium. In both assessments, the definition of calcium fracture was defined as a slit or complete break in the calcium plate. Calcified plaque was found in 86.4% of analyzed OFDI images. Calcium modification and fracture were detected in 20.6% and 11.0% of detected calcified plaques. Sensitivity, specificity, positive and negative predictive values of HD-IVUS detection for calcium modification and fracture were 54.4%, 97.8%, 86.7%, 89.1% and 86.0%, 94.5%, 58.2%, 96.8%, respectively. Discordance cases between both assessments demonstrated that heterogeneous calcium visualized by OFDI, separated calcium, and guide wire artifact can be misdiagnosed. Diagnostic accuracies of HD-IVUS for assessing calcium modification and fracture were acceptable as compared to OFDI. Such findings can be of utility during imaging guided interventional procedures with atherectomy.

Tissue characterisation and primary percutaneous coronary intervention guidance using intravascular ultrasound: rationale and design of the SPECTRUM study

Introduction

Intravascular ultrasound (IVUS) improves clinical outcome in patients undergoing percutaneous coronary intervention (PCI) but dedicated prospective studies assessing the safety and efficacy of IVUS guidance during primary PCI are lacking.

Methods and analysis

The SPECTRUM study is a prospective investigator-initiated single-centre single-arm observational cohort study aiming to enrol 200 patients presenting with ST-segment elevation myocardial infarct undergoing IVUS-guided primary PCI. IVUS will be performed at baseline, postintervention and postoptimisation (if applicable), using a 40–60 MHz high-definition (HD) system. Baseline tissue characterisation includes the morphological description of culprit lesion plaque characteristics and thrombus as assessed with HD-IVUS. The primary endpoint is target vessel failure at 12 months (defined as a composite of cardiac death, target vessel myocardial infarction and clinically driven target vessel revascularisation). The secondary outcome of interest is IVUS-guided optimisation, defined as IVUS-guided additional balloon dilatation or stent placement. Other endpoints include clinical and procedural outcomes along with post-PCI IVUS findings.

Ethics and dissemination

The protocol of this study was approved by the Ethics Committee of the Erasmus University Medical Center, Rotterdam, the Netherlands. Written informed consent is obtained from all patients. Study findings will be submitted to international peer-reviewed journals in the field of cardiovascular imaging and interventions and will be presented at international scientific meetings.

Trial registration number

NCT05007535.

Intravascular ultrasound-factors associated with slow flow following rotational atherectomy in heavily calcified coronary artery

Intravascular ultrasound (IVUS) can provide useful information in patients undergoing complex percutaneous coronary intervention with rotational atherectomy (RA). The association between IVUS findings and slow flow following rotational atherectomy (RA) has not been investigated, although slow flow has been shown to be an unfavorable sign with worse outcomes. The aim of this study was to determine the IVUS-factors associated with slow flow just after RA. We retrospectively enrolled 290 lesions (5316 IVUS-frames) with RA, which were divided into the slow flow group (n = 43 with 1029 IVUS-frames) and the non-slow flow group (n = 247 with 4287 IVUS-frames) based on the presence of slow flow. Multivariate regression analysis assessed the IVUS-factors associated with slow flow. Slow flow was significantly associated with long lesion length, the maximum number of reverberations [odds ratio (OR) 1.49; 95% confidence interval (CI) 1.07–2.07, p = 0.02] and nearly circumferential calcification at minimal lumen area (MLA) (≥ 300°) (OR, 2.21; 95% CI 1.13–4.32; p = 0.02). According to the maximum number of reverberations, the incidence of slow flow was 2.2% (n = 0), 11.9% (n = 1), 19.5% (n = 2), 22.5% (n = 3), and 44.4% (n = 4). In conclusion, IVUS findings such as longer lesion length, the maximum number of reverberations, and the greater arc of calcification at MLA may predict slow flow after RA. The operators need to pay more attention to the presence of reverberations to enhance the procedure safety.

Combined Use of Multiple Intravascular Imaging Techniques in Acute Coronary Syndrome

Recent advances in intravascular imaging techniques have made it possible to assess the culprit lesions of acute coronary syndrome (ACS) in the clinical setting. Intravascular ultrasound (IVUS) is the most commonly used intravascular imaging technique that provides cross-sectional images of coronary arteries. IVUS can assess plaque burden and vessel remodeling. Optical coherence tomography (OCT) is a high-resolution (10 μm) intravascular imaging technique that uses near-infrared light. OCT can identify key features of atheroma, such as lipid core and thin fibrous cap. Near-infrared spectroscopy (NIRS) can detect lipid composition by analyzing the near-infrared absorption properties of coronary plaques. NIRS provides a chemogram of the coronary artery wall, which allows for specific quantification of lipid accumulation. These intravascular imaging techniques can depict histological features of plaque rupture, plaque erosion, and calcified nodule in ACS culprit lesions. However, no single imaging technique is perfect and each has its respective strengths and limitations. In this review, we summarize the implications of combined use of multiple intravascular imaging techniques to assess the pathology of ACS and guide lesion-specific treatment.

Effects of Patient Background and Treatment Strategy on Clinical Outcomes After Coronary Intervention for Calcified Nodule Lesions

Background: The presence of a calcified nodule (CN) is associated with unfavorable clinical outcomes after percutaneous coronary intervention (PCI). This study clarified the optimal management of CNs by reassessing the PCI strategy in association with patient background characteristics and clinical outcomes.

Methods and Results: Among 5,332 consecutive PCI cases managed using intra-coronary imaging, CNs were found in 167 lesions (3.1%). CNs were predominantly located at the proximal or mid-right coronary artery (RCA; 62%). More than half presented clinically as acute coronary syndrome (ACS; 56%). All-cause mortality and the target lesion revascularization (TLR) rate at 1 year were 13% and 23%, respectively. Multivariate analysis revealed that hemodialysis, diabetes, and ACS were independent risk factors for all-cause death, whereas hemodialysis and RCA location were independent risk factors for TLR. Regarding the PCI strategy, not using rotational atherectomy (RA) was significantly associated with restenosis, whereas placing a drug-eluting stent (DES) was not.

Conclusions: Both hemodialysis and RCA location were strong predictors of poor outcomes after PCI for CN. Because not using RA was significantly associated with restenosis, it may be better to use RA whenever possible.

Intravascular Ultrasound-Derived Calcium Score to Predict Stent Expansion in Severely Calcified Lesions

[Figure: see text].

Optical Coherence Tomography of Coronary Plaque Progression and Destabilization: JACC Focus Seminar Part 3/3

The development of optical coherence tomography (OCT) has revolutionized our understanding of coronary artery disease. In vivo OCT research has paralleled with advances in computational fluid dynamics, providing additional insights in the various hemodynamic factors influencing plaque growth and stability. Recent OCT studies introduced a new concept of plaque healing in relation to clinical presentation. In addition to known mechanisms of acute coronary syndromes such as plaque rupture and plaque erosion, a new classification of calcified plaque was recently reported. This review will focus on important new insights that OCT has provided in recent years into coronary plaque development, progression, and destabilization, with a focus on the role of local hemodynamics and endothelial shear stress, the layered plaque (signature of previous subclinical plaque destabilization and healing), and the calcified culprit plaque.

Eruptive Calcified Nodules as a Potential Mechanism of Acute Coronary Thrombosis and Sudden Death

BACKGROUND

Calcified nodule (CN) has a unique plaque morphology, in which an area of nodular calcification causes disruption of the fibrous cap with overlying luminal thrombus. CN is reported to be the least frequent cause of acute coronary thrombosis, and the pathogenesis of CN has not been well studied.

OBJECTIVES

The purpose of this study is to provide a comprehensive morphologic assessment of the CN in addition to providing an evolutionary perspective as to how CN causes acute coronary thrombosis in patients with acute coronary syndromes.

METHODS

A total of 26 consecutive CN lesions from 25 subjects from our autopsy registry were evaluated. Detailed morphometric analysis was performed to understand the plaque characteristics of CN and nodular calcification.

RESULTS

The mean age was 70 years, with a high prevalence of diabetes and chronic kidney disease. CNs were equally distributed between men and women, with 61.5% of CNs found in the right coronary artery (n = 16), mainly within its mid-portion (56%). All CNs demonstrated surface nonocclusive luminal thrombus, consisting of multiple nodular fragments of calcification, protruding and disrupting the overlying fibrous cap, with evidence of endothelial cell loss. The degree of circumferential sheet calcification was significantly less in the culprit section (89° [interquartile range: 54° to 177°]) than in the adjacent proximal (206° [interquartile range: 157° to 269°], p = 0.0034) and distal (240° [interquartile range: 178° to 333°], p = 0.0004) sections. Polarized picrosirius red staining showed the presence of necrotic core calcium at culprit sites of CNs, whereas collagen calcium was more prevalent at the proximal and distal regions of CNs.

CONCLUSIONS

Our study suggests that fibrous cap disruption in CN with overlying thrombosis is initiated through the fragmentation of necrotic core calcifications, which is flanked-proximally and distally-by hard, collagen-rich calcification in coronary arteries, which are susceptible to mechanical stress.

Epidemiological Research Advances in Vascular Calcification in Diabetes

Vascular calcification is the transformation of arterial wall mesenchymal cells, particularly smooth muscle cells (SMCs), into osteoblast phenotypes by various pathological factors. Additionally, vascular transformation mediates the abnormal deposition of calcium salts in the vascular wall, such as intimal and media calcification. Various pathological types have been described, such as calcification and valve calcification. The incidence of vascular calcification in patients with diabetes is much higher than that in nondiabetic patients, representing a critical cause of cardiovascular events in patients with diabetes. Because basic research on the clinical transformation of vascular calcification has yet to be conducted, this study systematically expounds on the risk factors for vascular calcification, vascular bed differences, sex differences, ethnic differences, diagnosis, severity assessments, and treatments to facilitate the identification of a new entry point for basic research and subsequent clinical transformation regarding vascular calcification and corresponding clinical evaluation strategies.

NIRS-IVUS for Differentiating Coronary Plaque Rupture, Erosion, and Calcified Nodule in Acute Myocardial Infarction

OBJECTIVES

This study sought to investigate the ability of combined near-infrared spectroscopy and intravascular ultrasound (NIRS-IVUS) to differentiate plaque rupture (PR), plaque erosion (PE), or calcified nodule (CN) in acute myocardial infarction (AMI).

BACKGROUND

Most acute coronary syndromes occur from coronary thrombosis based on PR, PE, or CN. In vivo differentiation among PR, PE, and CN is a major challenge for intravascular imaging.

METHODS

The study enrolled 244 patients with AMI who had a de novo culprit lesion in a native coronary artery. The culprit lesions were assessed by both NIRS-IVUS and optical coherence tomography (OCT). Maximum lipid core burden index in 4 mm (maxLCBI_4mm) was measured by NIRS. Plaque cavity and convex calcium was detected by IVUS. The OCT diagnosis of PR (n = 175), PE (n = 44), and CN (n = 25) was used as a reference standard.

RESULTS

In the development cohort, IVUS-detected plaque cavity showed a high specificity (100%) and intermediate sensitivity (62%) for identifying OCT-PR. IVUS-detected convex calcium showed a high sensitivity (93%) and specificity (100%) for identifying OCT-CN. NIRS-measured maxLCBI_4mm was largest in OCT-PR (705 [interquartile range (IQR): 545 to 854]), followed by OCT-CN (355 [IQR: 303 to 478]) and OCT-PE (300 [IQR: 126 to 357]) (p < 0.001). The optimal cutoff value of maxLCBI_4mm was 426 for differentiating between OCT-PR and -PE; 328 for differentiating between OCT-PE and -CN; and 579 for differentiating between OCT-PR and -CN. In the validation cohort, the NIRS-IVUS classification algorithm using plaque cavity, convex calcium, and maxLCBI_4mm showed a sensitivity and specificity of 97% and 96% for identifying OCT-PR, 93% and 99% for OCT-PE, and 100% and 99% for OCT-CN, respectively.

CONCLUSIONS

By evaluating plaque cavity, convex calcium, and maxLCBI_4mm, NIRS-IVUS can accurately differentiate PR, PE, and CN.

Cardiac outcomes in patients with acute coronary syndrome attributable to calcified nodule

BACKGROUND AND AIMS

Calcified nodule (CN) is an eruptive calcified mass causing acute coronary syndrome (ACS). Since coronary calcification is associated with an elevated cardiac event's risk, ACS attributable to CN may exhibit worse clinical outcome following percutaneous coronary intervention (PCI).

METHODS

We retrospectively analyzed 657 ACS patients receiving PCI with newer-generation drug-eluting stent (DES) implantation under intravascular ultrasound (IVUS) guidance. CN was defined as (1) protruding calcification with its irregular surface and (2) the presence of calcification at adjacent proximal and distal segments. The primary endpoint was a composite of major adverse cardiac event [MACE = cardiac death + ACS recurrence + target lesion revascularization (TLR)].

RESULTS

CN was identified in 5.3% (=35/657) of the study subjects. CN patients were more likely to have coronary risk factors including hypertension (p = 0.005), chronic kidney disease (p < 0.001), maintenance hemodialysis (p < 0.001) and a history of PCI (p < 0.001). During the observational period (median = 1304 days), CN was associated with an increased risk of MACE (HR = 7.68, 95%CI = 4.61-12.80, p < 0.001), ACS recurrence (HR = 12.32, 95%CI = 6.05-25.11, p < 0.001) and TLR (HR = 10.48, 95%CI = 5.80-18.94, p < 0.001). These cardiac risks related to CN were consistently observed by Cox proportional hazards model (MACE: p < 0.001, ACS recurrence: p < 0.001, TLR: p < 0.001) and a propensity score-matched cohort analysis (MACE: p = 0.002, ACS recurrence: p = 0.01, TLR: p = 0.005). Of note, over 80% of TLR at the CN lesion was driven by its re-appearance within the implanted DES.

CONCLUSIONS

ACS patients attributable to CN have an increased risk of ACS recurrence and TLR, mainly driven by the continuous growth and protrusion of the calcified mass.

Comparison of clinical outcomes of intravascular ultrasound-calcified nodule between percutaneous coronary intervention with versus without rotational atherectomy in a propensity-score matched analysis

OBJECTIVES

This study aimed to compare the mid-term clinical outcomes of intravascular ultrasound (IVUS)-calcified nodules between percutaneous coronary intervention (PCI) with and without rotational atherectomy (RA).

BACKGROUND

There has been a debate whether to use RA for the revascularization of calcified nodule. Although RA can ablate the calcified structure within calcified nodule and may facilitate adequate stent expansion, RA may provoke severe coronary perforation, because calcified nodule typically shows eccentric calcification.

METHODS

We included 204 lesions with IVUS-calcified nodule, and divided into 73 lesions treated with RA (RA group) and 131 lesions without RA (non-RA group). After propensity-score matching, 42 lesions with RA (matched RA group) and 42 lesions without RA (matched non-RA group) were selected. We compared the clinical characteristics and outcomes between the 2 groups before and after propensity-score matching. The primary endpoint was ischemia-driven target vessel revascularization (TVR) within 1 year.

RESULTS

Acute lumen area gain on IVUS was comparable between the matched RA group and matched non-RA group (3.9 ± 2.1 mm2 vs. 3.4 ± 1.6 mm2, p = 0.18). The stent malapposition at calcified nodules was frequently observed in both groups. The ischemia-driven TVR was not different between the 2 groups before (p = 0.82) and after propensity score-matching (p = 0.87).

CONCLUSIONS

The use of RA could not reduce the incidence of ischemia-driven TVR in lesions with IVUS-calcified nodule. Our results do not support the routine use of RA for lesions with IVUS-calcified nodule.

Refractory In-Stent Restenosis Attributable to Eruptive Calcified Nodule

A 75-year-old female patient on hemodialysis presented with non-ST-segment elevation myocardial infarction. After successful primary percutaneous coronary intervention, in-stent restenosis (ISR) occurred 3 consecutive times. Intravascular imaging assessment during the repeated percutaneous coronary intervention indicated that the ISR was not associated with neointimal hyperplasia but was mainly attributed to a calcified nodule, which protruded into the lumen. We applied excimer laser catheter ablation to avoid another ISR. (Level of Difficulty: Intermediate.).

Culprit lesion morphology in patients with ST-segment elevation myocardial infarction assessed by optical coherence tomography

AIMS

This study sought to evaluate the incidence of ruptured plaques and nonruptured plaques (NRP) and to compare patient characteristics and detailed plaque morphology features between the two culprit types in ST-segment elevation myocardial infarction (STEMI) patients, using optical coherence tomography (OCT).

METHODS AND RESULTS

Using OCT, the culprit lesions in patients with STEMI were assessed prior to stent implantation. The culprit lesion was categorized as ruptured plaques or NRP, and the plaque components were evaluated. Fifty-two patients (69.3%) presented with ruptured plaques and 23 (30.7%) with NRP. Patients with NRP were younger (58.0 ± 10.4 vs 64.7 ± 9.9 years, P = 0.01) and more often smokers (72.7% vs 37.1%, P = 0.001), compared to ruptured plaques. NRP contained significantly more fibrotic plaque (20.0% [interquartile range (IQR) 13.7-29.8] vs 11.3% [IQR 6.9-18.1], P = 0.005), but less lipidic plaque (44.0% ± 13.7 vs 59.3% ± 13.6, P < 0.001), less superficial [5.0% (IQR 2.8-7.5) vs 8.1% (IQR 5.7-11.0), P = 0.005] and profound macrophages [0.9% (IQR 0.0-1.7) vs 2.2% (IQR 0.9-4.7), P = 0.003]. The prevalence, numbers and lengths of thin-cap fibroatheroma (TCFA) were significantly lower in NRP, compared to ruptured plaques [47.8% vs 88.5%, 0 (IQR 0-1) vs 1 (IQR 1-2) and 0 mm (IQR 0-2.7) vs 4.5 mm (IQR 2.3-7.7), P < 0.001].

CONCLUSIONS

One-third of STEMI patients had culprit lesions without an OCT-detectable ruptured plaque. Culprit lesions with NRP contained less vulnerable plaque components, such as lipid plaque, TCFAs and macrophages compared to ruptured plaques.

Clinical impact of calcified nodule in patients with heavily calcified lesions requiring rotational atherectomy

OBJECTIVES

We sought to evaluate the incidence and clinical impact of calcified nodule (CN) in patients with heavily calcified lesions requiring rotational atherectomy (RA).

BACKGROUND

It remains unclear whether CN impacts adversely on clinical outcomes in patients with heavily calcified lesions.

METHODS

Between January 2011 and February 2014, 264 patients after second-generation drug-eluting stent (DES) implantation following RA were retrospectively enrolled. CN was defined as a convex shape of the luminal side of calcium as assessed by intravascular ultrasound. The primary endpoint was the cumulative 5-year incidence of major adverse cardiac events (MACE), defined as a composite of cardiac death, clinically driven target lesion revascularization (CDTLR), and definite stent thrombosis (ST).

RESULTS

CN was observed in 128 patients (48.5%) with heavily calcified lesions. Cumulative 5-year incidence of MACE was significantly higher in the CN group than in the non-CN group, mainly driven by a higher rate of CDTLR and ST (35.4% vs. 18.8%, p < .001; 23.2% vs. 7.9%, p < .001; 7.0% vs. 0.93%, p = .009, respectively). Independent risk factors of 5-year MACE included hemodialysis (hazard ratio [HR] = 3.39, 95% confidence intervals [CI]: 2.00-5.73, p < .001), CN (HR = 2.53, 95% CI: 1.49-4.27, p < .001), ostial lesion (HR = 3.02, 95% CI: 1.58-5.78, p = .001), left ventricular ejection fraction ≤40% (HR = 2.17, 95% CI: 1.27-3.70, p = .005), and right coronary artery lesion (HR = 1.82, 95% CI: 1.07-3.11, p = .03).

CONCLUSIONS

CN was observed in 48.5% of heavily calcified lesions, resulting in unfavorable long-term clinical outcomes after second-generation DES implantation following RA.

Calcification in Atherosclerotic Plaque Vulnerability: Friend or Foe?

Calcification is a clinical marker of atherosclerosis. This review focuses on recent findings on the association between calcification and plaque vulnerability. Calcified plaques have traditionally been regarded as stable atheromas, those causing stenosis may be more stable than non-calcified plaques. With the advances in intravascular imaging technology, the detection of the calcification and its surrounding plaque components have evolved. Microcalcifications and spotty calcifications represent an active stage of vascular calcification correlated with inflammation, whereas the degree of plaque calcification is strongly inversely related to macrophage infiltration. Asymptomatic patients have a higher content of plaque calcification than that in symptomatic patients. The effect of calcification might be biphasic. Plaque rupture has been shown to correlate positively with the number of spotty calcifications, and inversely with the number of large calcifications. There may be certain stages of calcium deposition that may be more atherogenic. Moreover, superficial calcifications are independently associated with plaque rupture and intraplaque hemorrhage, which may be due to the concentrated and asymmetrical distribution of biological stress in plaques. Conclusively, calcification of differential amounts, sizes, shapes, and positions may play differential roles in plaque homeostasis. The surrounding environments around the calcification within plaques also have impacts on plaque homeostasis. The interactive effects of these important factors of calcifications and plaques still await further study.

Imaging assessment and accuracy in coronary artery autopsy: comparison of frequency-domain optical coherence tomography with intravascular ultrasound and histology

Optical coherence tomography (OCT) is a coronary artery imaging technique with high resolution. Second-generation frequency-domain OCT (FD-OCT) technology allows safer and faster clinical application compared with first-generation time-domain OCT (TD-OCT). Only limited validation studies compare FD-OCT with other modes of analysis: histology, which is the current gold standard, and intravascular ultrasound (IVUS). This study therefore aims to demonstrate the accuracy of FD-OCT images compared with IVUS and histology. FD-OCT and IVUS images were acquired from 203 segments from 31 coronary arteries obtained at autopsy from 20 cadavers. Of these, 30 randomly-selected pairs were used to create three classifications of plaque type based on morphological features in FD-OCT and IVUS compared with corresponding histopathology. The remaining 173 pairs were used to demonstrate the diagnostic accuracy for classification of coronary plaques by FD-OCT. Plaque type distributions were 27% fibroatheroma, 22% fibrocalcific plaque and 51% fibrous plaque. The diagnostic accuracies of FD-OCT for fibroatheroma, fibrocalcific plaque and fibrous plaque were 90, 95 and 93%, respectively. Those of IVUS were 81, 89 and 84%, respectively. FD-OCT achieved high diagnostic accuracy for the classification of coronary plaques comparable to TD-OCT. Physicians should consider the differences in the ability to classify plaque morphology of OCT of imaging devices when applying their use.

Density and morphology of coronary artery calcium for the prediction of cardiovascular events: insights from the Framingham Heart Study

OBJECTIVES

To investigate the association between directly measured density and morphology of coronary artery calcium (CAC) with cardiovascular disease (CVD) events, using computed tomography (CT).

METHODS

Framingham Heart Study (FHS) participants with CAC in noncontrast cardiac CT (2002-2005) were included and followed until 2016. Participants with known CVD or uninterpretable CT scans were excluded. We assessed and correlated (Spearman) CAC density, CAC volume, and the number of calcified segments. Moreover, we counted morphology features including shape (cylindrical, spherical, semi-tubular, and spotty), location (bifurcation, facing pericardium, or facing myocardium), and boundary regularity. In multivariate Cox regression analyses, we associated all CAC characteristics with CVD events (CVD-death, myocardial infarction, stroke).

RESULTS

Among 1330 included participants (57.8 ± 11.7 years; 63% male), 73 (5.5%) experienced CVD events in a median follow-up of 9.1 (7.8-10.1) years. CAC density correlated strongly with CAC volume (Spearman's ρ = 0.75; p < 0.001) and lower number of calcified segments (ρ = - 0.86; p < 0.001; controlled for CAC volume). In the survival analysis, CAC density was associated with CVD events independent of Framingham risk score (HR (per SD) = 2.09; 95%CI, 1.30-3.34; p = 0.002) but not after adjustment for CAC volume (p = 0.648). The extent of spherically shaped and pericardially sided calcifications was associated with fewer CVD events accounting for the number of calcified segments (HR (per count) = 0.55; 95%CI, 0.31-0.98; p = 0.042 and HR = 0.66; 95%CI, 0.45-0.98; p = 0.039, respectively).

CONCLUSIONS

Directly measured CAC density does not predict CVD events due to the strong correlation with CAC volume. The spherical shape and pericardial-sided location of CAC are associated with fewer CVD events and may represent morphological features related to stable coronary plaques.

KEY POINTS

• Coronary calcium density may not be independently associated with cardiovascular events. • Coronary calcium density correlates strongly with calcium volume. • Spherical shape and pericardial-sided location of CAC are associated with fewer CVD events.

Intravascular Ultrasound Assessment of In-Stent Restenosis in Saphenous Vein Grafts

Outcomes after percutaneous coronary interventions (PCI) in saphenous vein grafts (SVG) are inferior compared with native coronary arteries, but the mechanisms of SVG in-stent restenosis (ISR) have not been well-described. Thus, we aimed to evaluate the patterns of SVG ISR using intravascular ultrasound (IVUS) in 54 SVG ISR lesions. Stent underexpansion was defined as minimum stent area (MSA) <5 mm². The time from stent implantation to presentation with ISR (9 BMS, 18 first-generation DES, and 27 second-generation DES) was 3.7 ± 3.0 years. IVUS-defined ISR patterns were categorized as mechanical (33%) or biological (67%). Mechanical patterns comprised 10 cases of stent underexpansion (MSA = 4.2 ± 0.9 mm²), 6 stent fractures or deformations, and 2 uncovered aorto-anastomotic lesions. Biological patterns comprised 19 cases of neoatherosclerosis, 13 excessive neointimal hyperplasia (NIH, 65 ± 11%), and 4 thrombi. Compared with biological patterns of ISR, mechanical patterns were more frequently located at the SVG anastomosis (72% vs 39%, p = 0.04) and at the SVG hinge motion site (55% vs 21%, p = 0.02). Although patients with mechanical patterns of ISR presented earlier than those with biological patterns (2.3 vs 4.4 years, p = 0.009), 61% of them were diagnosed >1 year after stent implantation. In conclusion, SVG ISR is dominated by biological patterns including neoatherosclerosis. Mechanical patterns of SVG ISR are associated with earlier presentation and location at graft anastomosis or hinge motion site.

Chronic Kidney Disease Is Linked to Carotid Nodular Calcification, An Unstable Plaque Not Correlated to Inflammation

The incidence and the different type of carotid calcifications, nodular and non-nodular, and their role in the acute cerebrovascular disease has not yet been defined. Various studies have correlated the presence of specific risk factors, in particular the chronic kidney disease, with the presence of calcification, but not with the type of calcification. Since it is likely that carotid nodular calcifications rather than those with non-nodular aspect may represent a plaque at high risk of rupture, the purpose of our study was to evaluate the role of nodular calcification in the pathogenesis of cerebrovascular syndromes and their possible correlation with specific risk factors. A total of 168 carotid plaques from symptomatic and asymptomatic patients submitted to endarterectomy, whom complete clinical and laboratory assessment of major cardiovascular risk factors was available, were studied. In 21 endarterectomies (5 from symptomatic and 16 from asymptomatic patients) an eruptive calcified nodule, consisting of calcified plates associated to a small amount of fibrous tissue without extracellular lipids and inflammatory cells, was found protruding into the lumen. Nodular calcifications were significantly observed in patients affected by chronic kidney disease (with GFR<60 ml / min / 1.73 m²), with a normal lipidic and glycemic profile. On the contrary, non-nodular calcification, mainly correlated to diabetes, were stable lesions. Results of our study suggest that the mechanisms and the clinical significance of carotid atherosclerotic calcification may be different. The nodular calcification could represent a type of unstable plaque, significantly related to chronic kidney disease, without inflammation, morphologically different from the classical vulnerable plaques.

Automated lipid-rich plaque detection with short wavelength infra-red OCT system

Aims

Vulnerable coronary plaque is characterized by a large lipid core. Although commercially-available optical coherence tomography (OCT) systems use near-infrared light at 1300 nm wavelength, lipid shows characteristic absorption at 1700 nm. Therefore, we developed a novel, short wavelength infra-red, spectroscopic, spectral-domain OCT. The aim of the present study is to evaluate the accuracy of short wavelength (1700 nm) infra-red optical coherence tomography (SWIR-OCT) for identification of lipid tissue within coronary plaques.

Methods and results

Twenty-three coronary arteries from 10 cadavers were imaged at physiological pressure with 2.7 Fr SWIR-OCT catheter. When a blood-free image was observed, the SWIR-OCT imaging core was withdrawn at a rate of 20 mm/s using an automatic pullback device. SWIR-OCT images were acquired at 94 frames/s and digitally archived. SWIR-OCT generated grey-scale cross sectional images and colour tissue maps of all of the plaque by using a lipid analysis algorithm. After SWIR-OCT imaging, the arteries were pressure-fixed, sliced by cryostat and stained with Oil Red O, and then corresponding histology was collected in matched images. Regions of interest, selected from histology, were 117 lipidic and 34 fibrotic/calcified regions. SWIR-OCT showed high sensitivity (89%) and specificity (92%) for identifying lipid tissue within coronary plaques. The positive predictive value and negative predictive value were 97% and 74%, respectively.

Conclusion

SWIR-OCT accurately identified lipid tissue in coronary autopsy specimens. This new technique may hold promise for identifying histopathological features of coronary plaque at risk for rupture.

Advances in Intravascular Imaging: New Insights into the Vulnerable Plaque from Imaging Studies

The term “vulnerable plaque” denotes the plaque characteristics that are susceptible to coronary thrombosis. Previous post-mortem studies proposed 3 major mechanisms of coronary thrombosis: plaque rupture, plaque erosion, and calcified nodules. Of those, characteristics of rupture-prone plaque have been extensively studied. Pathology studies have identified the features of rupture-prone plaque including thin fibrous cap, large necrotic core, expansive vessel remodeling, inflammation, and neovascularization. Intravascular imaging modalities have emerged as adjunctive tools of angiography to identify vulnerable plaques. Multiple devices have been introduced to catheterization laboratories to date, including intravascular ultrasound (IVUS), virtual-histology IVUS, optical coherence tomography (OCT), coronary angioscopy, and near-infrared spectroscopy. With the use of these modalities, our understanding of vulnerable plaque has rapidly grown over the past several decades. One of the goals of intravascular imaging is to better predict and prevent future coronary events, for which prospective observational data is still lacking. OCT delineates microstructures of plaques, whereas IVUS visualizes macroscopic vascular structures. Specifically, plaque erosion, which has been underestimated in clinical practice, is gaining an interest due to the potential of OCT to make an in vivo diagnosis. Another potential future avenue for intravascular imaging is its use to guide treatment. Feasibility of tailored therapy for acute coronary syndromes (ACS) guided by OCT is under investigation. If it is proven to be effective, it may potentially lead to major shift in the management of millions of patients with ACS every year.

Intravascular ultrasound enhances the safety of rotational atherectomy

Intravascular ultrasound (IVUS) is mainly used in PCI to treat complex lesions, such as left main bifurcation, chronic total occlusion and calcified lesions. Although IVUS yields useful information such as the presence of napkin-ring calcification, the role of IVUS in rotational atherectomy (RA) is not fully appreciated. Recently, since the deliverability and crossability of IVUS catheters have improved, IVUS should be attempted before RA. Even if the IVUS catheter cannot cross the lesion, IVUS provides information just proximal to the target lesion, which would be useful in the selection of the appropriate guidewire and burr size. IVUS can be repeated following RA, which may influence the decision to continue RA with larger burrs. Circumferential calcification is a good indication for RA, since RA can create a calcium crack that facilitates balloon dilatation. However, if the distribution of calcification is not circumferential, the indication for RA can more safely be determined based on IVUS images than angiographic information alone. Because RA burrs usually follow the route taken by the IVUS catheter, the positional relationship between the IVUS imaging core and calcification would be similar to that between the RA burrs and calcification. The relationship between the RA burrs and distribution of calcification is discussed in this review.

Does calcium burden impact culprit lesion morphology and clinical results? An ADAPT-DES IVUS substudy

BACKGROUND

Increasing coronary lesion calcification is thought to be associated with adverse percutaneous coronary intervention (PCI) and clinical outcomes. We investigated the effects of calcium burden on culprit lesion morphology and clinical events after intravascular ultrasound (IVUS)-guided PCI in the ADAPT-DES study.

METHODS

ADAPT-DES was a prospective, multicenter registry of 8582 consecutive patients undergoing successful PCI using DES. A pre-specified virtual histology (VH)-IVUS substudy of 638 culprit lesions (638 patients) had both pre- and post-PCI VH-IVUS. We divided lesions into tertiles according to pre-PCI percent dense calcium volume (DCV%=dense calcium/plaque volume×100).

RESULTS

Compared with low and intermediate DCV% tertiles, patients in the high DCV% tertile had the largest arc of superficial calcium, highest percentage of necrotic core volume, and smallest remodeling index; they were also more likely to have advanced lesion morphology such as attenuated plaque and VH thin-cap fibroatheromas. In the high DCV% tertile IVUS guidance was associated with a minimum stent area that was smaller than tertiles with less calcium (p=0.01), but acceptable range, and similar stent expansion (73.8±16.8% vs. 74.0±19.2% vs. 72.4±17.3%, p=0.62) after more frequent use of rotational atherectomy and higher maximum inflation pressure. There was no significant association between pre-PCI DCV% and 2-year target lesion revascularization or major adverse cardiac events (cardiac death, myocardial infarction, or stent thrombosis).

CONCLUSIONS

Increasing coronary artery calcification burden was associated with more advanced, complex VH-IVUS lesion morphology, but not with adverse clinical outcomes, perhaps due to more aggressive PCI techniques that optimized stent expansion.