Optical Coherence Tomography or Intravascular Ultrasound?⁎⁎Editorials published in JACC: Cardiovascular Interventions reflect the views of the authors and do not necessarily represent the views of JACC: Cardiovascular Interventions or the American College of Cardiology

The evolving role of cardiac imaging in patients with myocardial infarction and non-obstructive coronary arteries

Myocardial infarction (MI) with non-obstructive coronary arteries (MINOCA) represents a heterogeneous clinical conundrum accounting for about 6%-8% of all acute MI who are referred for coronary angiography. Current guidelines and consensus documents recommend that these patients are appropriately diagnosed, uncovering the causes of MINOCA, so that specific therapies can be prescribed. Indeed, there are a variety of causes that can result in this clinical condition, and for this reason diagnostic cardiac imaging has an emerging critical role in the assessment of patients with suspected or confirmed MINOCA. In last years, different cardiac imaging techniques have been evaluated in this context, and the comprehension of their strengths and limitations is of the utmost importance for their effective use in clinical practice. Moreover, recent evidence is clearly suggesting that a multimodality cardiac imaging approach, combining different techniques, seems to be crucial for a proper management of MINOCA. However, great variability still exists in clinical practice in the management of patients with suspected MINOCA, also depending on the availability of diagnostic tools and local expertise. Herein, we review the current knowledge supporting the use of different cardiac imaging techniques in patients with MINOCA, underscoring the importance of a comprehensive multimodality cardiac imaging approach and proposing a practical diagnostic algorithm to properly identify and treat the specific causes of MINOCA, in order to improve prognosis and the quality of life in these patients.

Application of physics-based flow models in cardiovascular medicine: Current practices and challenges

Personalized physics-based flow models are becoming increasingly important in cardiovascular medicine. They are a powerful complement to traditional methods of clinical decision-making and offer a wealth of physiological information beyond conventional anatomic viewing using medical imaging data. These models have been used to identify key hemodynamic biomarkers, such as pressure gradient and wall shear stress, which are associated with determining the functional severity of cardiovascular diseases. Importantly, simulation-driven diagnostics can help researchers understand the complex interplay between geometric and fluid dynamic parameters, which can ultimately improve patient outcomes and treatment planning. The possibility to compute and predict diagnostic variables and hemodynamics biomarkers can therefore play a pivotal role in reducing adverse treatment outcomes and accelerate development of novel strategies for cardiovascular disease management.

Cardiac allograft vasculopathy: Differences of absolute and relative intimal hyperplasia in children versus adults in optical coherence tomography

BACKGROUND

Intracoronary imaging enables an early detection of intimal changes. To what extend the development of absolute and relative intimal hyperplasia in intracoronary imaging differs depending on age and post-transplant time is not known.

METHODS

Aim of our retrospective study was to compare findings between 24 pediatric (cohort P) and 21 adult HTx patients (cohort A) using optical coherence tomography (OCT) at corresponding post-transplant intervals (≤5 years: P1 (n = 11) and A1 (n = 10); >5 and ≤ 10 years: P2 (n = 13) and A2 (n = 11),. Coronary intima thickness (IT), media thickness (MT) and intima to media ratio (I/M) were assessed per quadrant. Maximal IT >0.3 mm was considered absolute, I/M > 1 relative intimal hyperplasia.

RESULTS

Compared to A1, I/M was significantly higher in P1 (maximal I/M: P1: 5.41 [2.81-13.39] vs. A1: 2.30 [1.55-3.62], p = 0.005), whereas absolute IT values were comparable. In contrast, I/M was comparable between P2 and A2, but absolute IT were significantly higher in A2 (maximal IT: P2: 0.16 mm [0.11-0.25] vs. A2: 0.40 mm [0.30-0.71], p < 0.001). A2 presented with higher absolute IT (maximal: A1: 0.16 mm [0.12-0.44] vs. A2: 0.40 mm [0.30-0.71], p = 0.02) and I/M (maximal I/M A1: 2.30 [1.55-3.62] vs. A2: 3.79 [3.01-5.62], p = 0.04).

CONCLUSION

Our results suggest an age- and time-dependent difference in the prevalence of absolute and relative intimal hyperplasia in OCT, with an early peak in children and a progressive increase in adults.

Imaging during percutaneous coronary intervention for optimizing outcomes

Angiography is the current gold standard for imaging during percutaneous coronary interventions but has significant limitations. Catheter-based intravascular imaging techniques such as intravascular ultrasound and the more recent optical coherence tomography have the potential to overcome these limitations and thus optimize clinical outcomes. In this update, we discussed the current applications of the available imaging techniques, existing evidence, continuing unmet needs, and potential areas for further research.

Plaque burden influences accurate classification of fibrous cap atheroma by in vivo optical coherence tomography in a porcine model of advanced coronary atherosclerosis

AIMS

In vivo validation of coronary optical coherence tomography (OCT) against histology and the effects of plaque burden (PB) on plaque classification remain unreported. We aimed to investigate this in a porcine model with human-like coronary atherosclerosis.

METHODS AND RESULTS

Five female Yucatan D374Y-PCSK9 transgenic hypercholesterolaemic minipigs were implanted with a coronary shear-modifying stent to induce advanced atherosclerosis. OCT frames (n=201) were obtained 34 weeks after implantation. Coronary arteries were perfusion-fixed, serially sectioned and co-registered with OCT using a validated algorithm. Lesions were adjudicated using the Virmani classification and PB assessed from histology. OCT had a high sensitivity, but modest specificity (92.9% and 74.6%), for identifying fibrous cap atheroma (FCA). The reduced specificity for OCT was due to misclassification of plaques with histologically defined pathological intimal thickening (PIT) as FCA (46.1% of the frames with histological PIT were misclassified). PIT lesions misclassified as FCA by OCT had a statistically higher PB than in other OCT frames (median 32.0% versus 13.4%; p<0.0001). Misclassification of PIT lesions by OCT occurred when PB exceeded approximately 20%.

CONCLUSIONS

Compared with histology, in vivo OCT classification of FCA had high sensitivity but reduced specificity due to misclassification of PITs with high PB.

Position Paper Computational Cardiology

Computational cardiology is the scientific field devoted to the development of methodologies that enhance our mechanistic understanding, diagnosis and treatment of cardiovascular disease. In this regard, the field embraces the extraordinary pace of discovery in imaging, computational modeling, and cardiovascular informatics at the intersection of atherogenesis and vascular biology. This paper highlights existing methods, practices, and computational models and proposes new strategies to support a multidisciplinary effort in this space. We focus on the means by that to leverage and coalesce these multiple disciplines to advance translational science and computational cardiology. Analyzing the scientific trends and understanding the current needs we present our perspective for the future of cardiovascular treatment.

Morphological Features and Plaque Composition in Culprit Atheromatous Plaques of Patients with Acute Coronary Syndromes

Background: The independent role of each plaque feature in relation to plaque vulnerability is still the subject of ongoing research. This study aimed to compare the morphologic characteristics of vulnerable atheromatous coronary plaques with the ones of stable, non-vulnerable plaques, and in plaques with different locations in the coronary tree, in order to identify the most relevant imaging-based biomarkers associated with coronary plaque vulnerability.

Material and methods: This was a prospective observational, non-randomized study that included 50 patients with unstable angina who underwent computed tomography angiography for assessment of the entire coronary artery tree followed by complex morphologic analysis of all lesions, divided into two groups: group 1 – 25 patients with vulnerable plaque (VP) and group 2 – 25 age- and gender-matched patients with non-vulnerable plaque (NVP).

Results: Lesions with a stenosis degree >70% were significantly longer than those with a stenosis degree <70% (8.27 ± 2.74 mm vs. 5.56 ± 4.11 mm, p = 0.04). VP presented significantly higher values of plaque thickness (p = 0.0005), plaque burden (p = 0.0004), and higher total plaque volume (p = 0.0005) than NVP. The remodeling index was not significantly different between the groups (p = 0.6), but the eccentricity index was (0.24 ± 0.14 compared to 0.14 ± 0.17, p = 0.023). Linear regression analysis revealed a significant correlation between plaque burden and plaque components in VP (r = 0.76, p <0.0001 for necrotic core; r = 0.62, p = 0.0008 for fibro-fatty tissue; and r = 0.5, p = 0.01 for fibrotic tissue volume). Culprit plaques located in the right coronary artery presented significantly larger plaque burden volumes (91.17 ± 4.88 mm3 vs. 83.35 ± 8.47 mm3, p = 0.04), larger volumes of necrotic core (82.03 ± 47.85 mm3 vs. 45.84 ± 43.72 mm3, p = 0.02) and fibrofatty tissue (53.23 ± 31.92 mm3 vs. 23.76 ± 20.90 mm3, p = 0.02) than the ones situated in the left coronary artery.

Conclusions: VPs from the culprit lesions exhibit a different phenotype than non-vulnerable ones, and vulnerability features are present in a significantly larger extent in VPs from the right coronary artery as compared to those from the left coronary artery.

Original research. The Assessment of Epicardial Adipose Tissue in Acute Coronary Syndrome Patients. A Systematic Review

Background: This systematic review seeks to evaluate the role of epicardial adipose tissue (EAT), quantified either by thickness, assessed by transthoracic echocardiography, or by volume, assessed by cardiac computed tomography (CT), in the follow-up of patients with acute coronary syndromes (ACS). Method: One-hundred forty-four articles were screened, from which 56 were reviewed in full-text. From those, 47 studies were excluded for the following reasons: they did not meet the inclusion criteria; they were either reviews or meta-analyses; the study cohorts included only stable coronary artery disease patients; they did not state a clear and concise study design, endpoints, or follow-up. The final draft included nine studies for systematic evaluation. Results: Of the 2,306 patients included in the review, 170 underwent cardiac CT while the remaining 2,136 underwent transthoracic echocardiography for the measurement of EAT. The analysis found that the EAT thickness was significantly associated with major adverse cardiovascular events (MACE) rates during hospitalization (OR: -1.3, 95% CI: 1.05-1.62, p = 0.020) and at three years (HR: 1.524, 95% CI: 1.0-2.2, p = 0.038). The included studies found that EAT was correlated with the following clinical and angiographic risk scores for ACS: GRACE (r = 0.438, p <0.001), TIMI risk score (r = 0.363, p = 0.001), SYNTAX score (r = 0.690, p <0.0001; r = 0.610, p <0.01), and Gensini score (r = 0.438, p = 0.001). There was an inverse correlation between ST-segment resolution of <70% after revascularization and EAT (r = −0.414, p = 0.01), and the myocardial blush grade (r = −0.549, p <0.001). The EF aggregation ranged between 2.65 mm and 4.7 mm within the included studies. Conclusions: EAT, evaluated either by echocardiography or cardiac CT, correlates with the severity of coronary lesions, with the clinical and angiographic risk scores for acute coronary syndromes, with indicators for coronary reperfusion, and with short- and long-term MACE rates. Further studies are required to fully elucidate the role of this extensively studied but still novel cardiovascular biomarker as part of a risk prediction tool.

Review. Automatic Segmentation Techniques of the Coronary Artery Using CT Images in Acute Coronary Syndromes

Coronary artery disease represents one of the leading reasons of death worldwide, and acute coronary syndromes are their most devastating consequences. It is extremely important to identify the patients at risk for developing an acute myocardial infarction, and this goal can be achieved using noninvasive imaging techniques. Coronary computed tomography angiography (CCTA) is currently one of the most reliable methods used for assessing the coronary arteries; however, its use in emergency settings is sometimes limited due to time constraints. This paper presents the main characteristics of plaque vulnerability, the role of CCTA in the assessment of vulnerable plaques, and automatic segmentation techniques of the coronary artery tree based on CT angiography images. A detailed inventory of existing methods is given, representing the state-of-the-art of computational methods applied in vascular system segmentation, focusing on the current applications in acute coronary syndromes.

Assessment of Coronary Plaque Vulnerability in Acute Coronary Syndromes using Optical Coherence Tomography and Intravascular Ultrasound. A Systematic Review

The aim of this systematic review was to analyze studies characterizing vulnerable coronary plaques using optical coherence tomography (OCT) and intravascular ultrasound (IVUS), in order to identify the most efficient invasive technique permitting plaque characterization in patients with acute myocardial infarction.

Method: A total number of 432 studies were identified, 420 through database searching and 12 through manual searching. Eight duplicate studies were removed, leaving a total number of 424 studies to be screened. Twenty-six studies only available in Abstract-only form were excluded, resulting in 398 studies checked for eligibility. Eleven studies fulfilled the eligibility criteria and were included in this systematic analysis. Plaque vulnerability was investigated in plaques with thin cap fibroatheroma (TCFA) versus those with thick cap fibroatheroma, in ruptured coronary plaques versus non-ruptured coronary plaques, in culprit versus non-culprit lesions and in lipid-rich versus non-lipid-rich plaques.

Results: A total of 1,568 coronary plaques in 1,225 patients with acute coronary syndromes (ACS) who underwent both IVUS and OCT for analysis of plaque features were included in the final analysis. The review identified the following IVUS-derived features as significantly correlated with plaque vulnerability: plaque burden (p <0.001), remodeling index (p <0.001), external elastic membrane cross-sectional area (p <0.001), and the amount of necrotic core (p <0.001), while OCT-derived features characterizing unstable plaque were TCFA (p <0.001), lipid arch (p <0.001), accumulation of macrophages (p = 0.03), and presence of intracoronary thrombus (p <0.001).

Conclusion: Both IVUS and OCT are invasive imaging techniques able to provide relevant information on the vulnerability of coronary atheromatous plaques, identifying, as they do, various plaque features significantly associated with unstable plaques. Information provided by the two techniques is complementary, and both methods can serve as a useful clinical diagnostic tool, especially in cases of ACS patients undergoing a revascularization procedure.

Associations between the Framingham Risk Score and coronary plaque characteristics as assessed by three-vessel optical coherence tomography

OBJECTIVES

This study sought to explore the association between the Framingham Risk Score (FRS) and coronary plaque characteristics assessed by optical coherence tomography (OCT) imaging.

BACKGROUND

Clinical prediction models are useful for identifying high-risk patients. However, coronary events often occur in individuals estimated to be at low risk.

METHODS

A total of 254 patients with coronary artery disease who underwent three-vessel OCT were divided into tertiles according to FRS. Nonculprit plaque characteristics were compared among the three groups.

RESULTS

A total of 663 plaques were analyzed. FRS was significantly associated with calcification [37% (low FRS) vs. 46% (intermediate FRS) vs. 70% (high FRS); P<0.001] and neovascularization [39% (low FRS) vs. 41% (intermediate FRS) vs. 56% (high FRS); P<0.001], but not with lipid-rich plaques or thin-cap fibroatheroma (TCFA). On multivariate analysis, FRS was an independent predictor of the presence of both calcification and neovascularization. There were no deaths, two acute myocardial infarctions, and 15 nontarget lesion revascularizations at the 1-year follow-up. The event rate increased progressively across FRS tertiles [2.4% (low FRS) vs. 7.1% (intermediate FRS) vs. 8.6% (high FRS); P=0.186]. The c-statistic for FRS to predict future clinical events was 0.628 (95% confidence interval, 0.500-0.757). The addition of both calcification and TCFA to FRS provided incremental prognostic value [c-statistics: 0.761 (95% confidence interval, 0.631-0.890)].

CONCLUSION

The present study showed significant associations between FRS and the presence of coronary calcification and neovascularization in nonculprit plaques. The combination of FRS and OCT-detected calcifications and TCFA provides improved prognostic ability in identifying patients with known coronary artery disease who are at risk of recurrent events.

Optical Coherence Tomography Imaging: Novel Insights into the Vascular Response After Coronary Stent Implantation

Optical coherence tomography (OCT) is a high-resolution imaging technique that is increasingly used for intracoronary imaging to characterize coronary atherosclerotic plaques and vascular responses after coronary stent implantation. Introduction of optical frequency-domain imaging (OFDI; second generation OCT) has simplified practical use of this novel imaging modality resulting in a more widespread availability in interventional cardiology. Here we highlight recent insights into the acute and chronic vascular response after coronary stent implantation by OCT imaging. OCT provides cross-sectional images with approximately 10-fold higher resolution as compared to intravascular-ultrasound (IVUS), allowing for precise evaluation of tissue coverage and malapposition of coronary stent struts. More than 30 studies using OCT to compare vascular responses to different stents have now been reported. Recent studies have examined the relation between OCT-image characteristics and tissue composition around stent struts. OCT is used for evaluation of novel stent concepts, such as bioengineered stents and bioabsorbable stents, where it provides more accurate information than IVUS. While intracoronary OCT imaging is further developed, including faster 3D-OCT-image-reconstruction, larger OCT studies/registries with standardized analysis will provide more insights into clinical implications of observations from OCT-imaging after coronary stent implantation.

Intracoronary optical diagnostics current status, limitations, and potential

Optical coherence tomography (OCT), is a novel intravascular imaging modality analogous to intravascular ultrasound but uses light instead of sound. This review details the background, development, and status of current investigation using OCT, and discusses advantages, limitations, and likely future developments. It provides indications for possible future clinical use, and places OCT in the context of current intravascular imaging in what is a rapidly changing field of investigation.

Predictors of Periprocedural (Type IVa) Myocardial Infarction, as Assessed by Frequency-Domain Optical Coherence Tomography

Background—

Frequency-domain optical coherence tomography (FD-OCT) is easily able to define both pre- and post-stenting features of the atherosclerotic plaque that can potentially be related to periprocedural complications. We sought to examine which FD-OCT-defined characteristics, assessed both before and after stent deployment, predicted periprocedural (type IVa) myocardial infarction (MI).

Methods and Results—

FD-OCT was performed before and after coronary stenting in 50 patients undergoing percutaneous coronary intervention (PCI) for either non-ST segment elevation MI (NSTEMI) or stable angina. All patients underwent single-vessel stenting, and only drug-eluting stents were implanted. Troponin T was analyzed on admission, before PCI, and at 12 and 24 hours after PCI, and type IVa MI was defined in stable angina as a rise of at least 3× upper reference limit and in NSTEMI as a pre-PCI troponin T fall, followed by post-PCI troponin T rise >20%. Type IVa MI was diagnosed in 21 patients, while the remaining 29 represented the control group. FD-OCT analysis showed that thin-cap fibroatheroma (76.2% versus 41.4%; P =0.017) prior to PCI, intrastent thrombus (61.9% versus 20.7%; P =0.04), and intrastent dissection (61.9% versus 31%; P =0.03) after PCI were significantly more frequent in type IVa MI than in the control group. Multivariate logistic regression analysis confirmed thin-cap fibroatheroma (OR 29.7, 95% CI 1.4 to 32.1), intrastent thrombus (OR 5.5, CI 1.2 to 24.9) and intrastent dissection (OR 5.3, CI 1.2 to 24.3) as independent predictors of type IVa MI.

Conclusions—

In conclusion, presence of thin-cap fibroatheroma at pre-PCI FD-OCT and of intrastent thrombus and intrastent dissection at post-PCI FD-OCT predict type IVa MI in a contemporary sample of patients treated with second-generation drug-eluting stents. Interestingly, 2 of the 3 predictors of type IVa MI were not apparent at pre-PCI FD-OCT.