Prognostic Value of Coronary CT Angiography With Selective PET Perfusion Imaging in Coronary Artery Disease

Polygenic Risk Scores in Predicting Coronary Artery Disease in Symptomatic Patients. A Validation Study

AIM

Clinical risk scores for coronary artery disease (CAD) are used in clinical practice to select patients for diagnostic testing and therapy. Several studies have proposed that polygenic risk scores (PRSs) can improve the prediction of CAD, but the scores need to be validated in clinical populations with accurately characterized phenotypes. We assessed the predictive power of the three most promising PRSs for the prediction of coronary atherosclerosis and obstructive CAD.

METHODS

This study was conducted on 943 symptomatic patients with suspected CAD for whom the phenotype was accurately characterized using anatomic and functional imaging. Previously published genome-wide polygenic scores were generated to compare a genetic model based on PRSs with a model based on clinical data. The test and PRS cohorts were predominantly Caucasian of northern European ancestry.

RESULTS

All three PRSs predicted coronary atherosclerosis and obstructive CAD statistically significantly. The predictive accuracy of the models combining clinical data and different PRSs varied between 0.778 and 0.805 in terms of the area under the receiver operating characteristic (AUROC), being close to the model including only clinical variables (AUROC 0.769). The difference between the clinical model and combined clinical + PRS model was not significant for PRS1 (p=0.627) and PRS3 (p=0.061). Only PRS2 slightly improved the predictive power of the model (p=0.04). The likelihood ratios showed the very weak diagnostic power of all PRSs.

CONCLUSION

The addition of PRSs to conventional risk factors did not clinically significantly improve the predictive accuracy for either coronary atherosclerosis or obstructive CAD, showing that current PRSs are not justified for routine clinical use in CAD.

Incremental prognostic value of downstream positron emission tomography perfusion imaging after coronary computed tomography angiography: a study using machine learning

AIMS

To evaluate the incremental value of positron emission tomography (PET) myocardial perfusion imaging (MPI) over coronary computed tomography angiography (CCTA) in predicting short- and long-term outcome using machine learning (ML) approaches.

METHODS AND RESULTS

A total of 2411 patients with clinically suspected coronary artery disease (CAD) underwent CCTA, out of whom 891 patients were admitted to downstream PET MPI for haemodynamic evaluation of obstructive coronary stenosis. Two sets of Extreme Gradient Boosting (XGBoost) ML models were trained, one with all the clinical and imaging variables (including PET) and the other with only clinical and CCTA-based variables. Difference in the performance of the two sets was analysed by means of area under the receiver operating characteristic curve (AUC). After the removal of incomplete data entries, 2284 patients remained for further analysis. During the 8-year follow-up, 210 adverse events occurred including 59 myocardial infarctions, 35 unstable angina pectoris, and 116 deaths. The PET MPI data improved the outcome prediction over CCTA during the first 4 years of the observation time and the highest AUC was at the observation time of Year 1 (0.82, 95% confidence interval 0.804-0.827). After that, there was no significant incremental prognostic value by PET MPI.

CONCLUSION

PET MPI variables improve the prediction of adverse events beyond CCTA imaging alone for the first 4 years of follow-up. This illustrates the complementary nature of anatomic and functional information in predicting the outcome of patients with suspected CAD.

Hybridizing machine learning in survival analysis of cardiac PET/CT imaging

BACKGROUND

Machine Learning (ML) allows integration of the numerous variables delivered by cardiac PET/CT, while traditional survival analysis can provide explainable prognostic estimates from a restricted number of input variables. We implemented a hybrid ML-and-survival analysis of multimodal PET/CT data to identify patients who developed myocardial infarction (MI) or death in long-term follow up.

METHODS

Data from 739 intermediate risk patients who underwent coronary CT and selectively stress 15O-water-PET perfusion were analyzed for the occurrence of MI and all-cause mortality. Images were evaluated segmentally for atherosclerosis and absolute myocardial perfusion through 75 variables that were integrated through ML into an ML-CCTA and an ML-PET score. These scores were then modeled along with clinical variables through Cox regression. This hybridized model was compared against an expert interpretation-based and a calcium score-based model.

RESULTS

Compared with expert- and calcium score-based models, the hybridized ML-survival model showed the highest performance (CI .81 vs .71 and .64). The strongest predictor for outcomes was the ML-CCTA score.

CONCLUSION

Prognostic modeling of PET/CT data for the long-term occurrence of adverse events may be improved through ML imaging score integration and subsequent traditional survival analysis with clinical variables. This hybridization of methods offers an alternative to traditional survival modeling of conventional expert image scoring and interpretation.

Should we choose CT angiography first instead of SPECT/PET first for the diagnosis and management of coronary artery disease?

In patients presenting with chest pain, current guidelines recommend the use of coronary computed tomography angiography and single-photon emission tomography/positron emission tomography, both with equal class 1 indication and level of evidence A. There is no clear recommendation on which test should be used as a first-line test. The choice of the test should be based on individualized clinical risk assessment, patient characteristics, local expertise/availability, and patient preferences. In this context, it is fair to ask which non-invasive imaging test to choose. The debate reproduced in this article answers this question by summarizing the considerations in selecting present state-of-the-art criteria of the right test for the right patient to ensure efficient resource utilization, minimize unnecessary testing, and maximize diagnostic accuracy and therapeutic efficacy.

Prognostic value of combined coronary CT angiography and myocardial perfusion imaging in women and men

AIMS

Combined anatomical and functional imaging enables detection of non-obstructive and obstructive coronary artery disease (CAD) as well as myocardial ischaemia. We evaluated sex differences in disease profile and outcomes after combined computed tomography angiography (CTA) and positron emission tomography (PET) perfusion imaging in patients with suspected obstructive CAD.

METHODS AND RESULTS

We retrospectively evaluated 1948 patients (59% women) referred for coronary CTA due to suspected CAD during the years 2008-2016. Patients with a suspected obstructive lesion on coronary CTA (n = 657) underwent 15O-water PET to assess stress myocardial blood flow (MBF). During a mean follow-up of 6.8 years, 182 adverse events (all-cause death, myocardial infarction, or unstable angina) occurred. Women had more often normal coronary arteries (42% vs. 22%, P < 0.001) and less often abnormal stress MBF (9% vs. 28%, P < 0.001) than men. The annual adverse event rate was lower in women vs. men (1.2% vs. 1.7%, P = 0.02). Both in women and men, coronary calcification, non-obstructive CAD, and abnormal stress MBF were independent predictors of events. Abnormal stress MBF was associated with 5.0- and 5.6-fold adverse event rates in women and men, respectively. There was no interaction between sex and coronary calcification, non-obstructive CAD, or abnormal stress MBF in terms of predicting adverse events.

CONCLUSION

Among patients evaluated for chronic chest pain, women have a lower prevalence of ischaemic CAD and a lower rate of adverse events. Combined coronary CTA and PET myocardial perfusion imaging predict outcomes equally in women and men.

Carimas: An Extensive Medical Imaging Data Processing Tool for Research

Carimas is a multi-purpose medical imaging data processing tool, which can be used to visualize, analyze, and model different medical images in research. Originally, it was developed only for positron emission tomography data in 2009, but the use of this software has extended to many other tomography imaging modalities, such as computed tomography and magnetic resonance imaging. Carimas is especially well-suited for analysis of three- and four-dimensional image data and creating polar maps in modeling of cardiac perfusion. This article explores various parts of Carimas, including its key features, program structure, and application possibilities.

Computed tomography and nuclear medicine for the assessment of coronary inflammation: clinical applications and perspectives

There is increasing evidence that in patients with atherosclerotic cardiovascular disease (ASCVD) under optimal medical therapy, a persisting dysregulation of the lipid and glucose metabolism, associated with adipose tissue dysfunction and inflammation, predicts a substantial residual risk of disease progression and cardiovascular events. Despite the inflammatory nature of ASCVD, circulating biomarkers such as high-sensitivity C-reactive protein and interleukins may lack specificity for vascular inflammation. As known, dysfunctional epicardial adipose tissue (EAT) and pericoronary adipose tissue (PCAT) produce pro-inflammatory mediators and promote cellular tissue infiltration triggering further pro-inflammatory mechanisms. The consequent tissue modifications determine the attenuation of PCAT as assessed and measured by coronary computed tomography angiography (CCTA). Recently, relevant studies have demonstrated a correlation between EAT and PCAT and obstructive coronary artery disease, inflammatory plaque status and coronary flow reserve (CFR). In parallel, CFR is well recognized as a marker of coronary vasomotor function that incorporates the haemodynamic effects of epicardial, diffuse and small-vessel disease on myocardial tissue perfusion. An inverse relationship between EAT volume and coronary vascular function and the association of PCAT attenuation and impaired CFR have already been reported. Moreover, many studies demonstrated that 18F-FDG PET is able to detect PCAT inflammation in patients with coronary atherosclerosis. Importantly, the perivascular FAI (fat attenuation index) showed incremental value for the prediction of adverse clinical events beyond traditional risk factors and CCTA indices by providing a quantitative measure of coronary inflammation. As an indicator of increased cardiac mortality, it could guide early targeted primary prevention in a wide spectrum of patients. In this review, we summarize the current evidence regarding the clinical applications and perspectives of EAT and PCAT assessment performed by CCTA and the prognostic information derived by nuclear medicine.

Plaque volume, composition, and fraction versus ischemia and outcomes in patients with coronary artery disease

BACKGROUND

The various plaque components have been associated with ischemia and outcomes in patients with coronary artery disease (CAD). The main goal of this analysis was to test the hypothesis that, at patient level, the fraction of non-calcified plaque volume (PV) of total PV is associated with ischemia and outcomes in patients with CAD. This ratio could be a simple and clinically useful parameter, if predicting outcomes.

METHODS

Consecutive patients with suspected CAD undergoing coronary computed tomography angiography with selective positron emission tomography perfusion imaging were selected. Plaque components were quantitatively analyzed at patient level. The fraction of various plaque components were expressed as percentage of total PV and examined among patients with non-obstructive CAD, suspected stenosis with normal perfusion, and those with reduced myocardial perfusion. Clinical outcomes included all-cause mortality and myocardial infarction.

RESULTS

In total, 494 patients (age 63 ​± ​9 years, 55% male) were included. Total PV and all plaque components were significantly larger in patients with reduced myocardial perfusion compared to patients with normal perfusion and those with non-obstructive CAD. During follow-up 35 events occurred. Patients with any plaque component ​≥ ​median showed worse outcomes (log-rank p ​< ​0.001 for all). In addition, low-attenuation plaque ​≥ ​median was associated with worse outcomes independent of total PV (adjusted HR: 2.754, 95% CI: 1.022-7.0419, p ​= ​0.045). The fractions of the various plaque components were not associated with outcomes.

CONCLUSION

Larger total PV or any plaque component at patient level are associated with abnormal myocardial perfusion and adverse events. The various plaque components as fraction of total PV lack additional prognostic value.

Warranty period of coronary computed tomography angiography and [15O]H2O positron emission tomography in symptomatic patients

AIMS

Data on the warranty period of coronary computed tomography angiography (CTA) and combined coronary CTA/positron emission tomography (PET) are scarce. The present study aimed to determine the event-free (warranty) period after coronary CTA and the potential additional value of PET.

METHOD AND RESULTS

Patients with suspected but not previously diagnosed coronary artery disease (CAD) who underwent coronary CTA and/or [15O]H2O PET were categorized based upon coronary CTA as no CAD, non-obstructive CAD, or obstructive CAD. A hyperaemic myocardial blood flow (MBF) ≤ 2.3 mL/min/g was considered abnormal. The warranty period was defined as the time for which the cumulative event rate of death and non-fatal myocardial infarction (MI) was below 5%. Of 2575 included patients (mean age 61.4 ± 9.9 years, 41% male), 1319 (51.2%) underwent coronary CTA only and 1237 (48.0%) underwent combined coronary CTA/PET. During a median follow-up of 7.0 years 163 deaths and 68 MIs occurred. The warranty period for patients with no CAD on coronary CTA was ≥10 years, whereas patients with non-obstructive CAD had a 5-year warranty period. Patients with obstructive CAD and normal hyperaemic MBF had a 2-year longer warranty period compared to patients with obstructive CAD and abnormal MBF (3 years vs. 1 year).

CONCLUSION

As standalone imaging, the warranty period for normal coronary CTA is ≥10 years, whereas patients with non-obstructive CAD have a warranty period of 5 years. Normal PET yielded a 2-year longer warranty period in patients with obstructive CAD.

Incorporating coronary artery calcium scoring in the prediction of obstructive coronary artery disease with myocardial ischemia: a study with sequential use of coronary computed tomography angiography and positron emission tomography imaging

BACKGROUND

Additional strategies are needed to refine the referral for diagnostic testing of symptomatic patients with suspected coronary artery disease (CAD). We aimed to compare various models to predict hemodynamically obstructive CAD.

METHODS AND RESULTS

Symptomatic patients with suspected CAD who underwent coronary artery calcium scoring (CACS) and sequential coronary computed tomography angiography (CCTA) and [15O]H2O positron emission tomography (PET) myocardial perfusion imaging were analyzed. Obstructive CAD was defined as a suspected coronary artery stenosis on CCTA with myocardial ischemia on PET (absolute stress myocardial perfusion ≤ 2.4 mL/g/min in ≥ 1 segment). Three models were developed to predict obstructive CAD-induced myocardial ischemia using logistic regression analysis: (1) basic model: including age, sex and cardiac symptoms, (2) risk factor model: adding number of risk factors to the basic model, and (3) CACS model: adding CACS to the risk factor model. Model performance was evaluated using discriminatory ability with area under the receiver-operating characteristic curves (AUC). A total of 647 patients (mean age 62 ± 9 years, 45% men) underwent CACS and sequential CCTA and PET myocardial perfusion imaging. Obstructive CAD with myocardial ischemia on PET was present in 151 (23%) patients. CACS was independently associated with myocardial ischemia (P < .001). AUC for the discrimination of ischemia for the CACS model was superior over the basic model and risk factor model (P < .001).

CONCLUSIONS

Adding CACS to the model including age, sex, cardiac symptoms and number of risk factors increases the accuracy to predict obstructive CAD with myocardial ischemia on PET in symptomatic patients with suspected CAD.

Coronary computed tomography angiography-based endothelial wall shear stress in normal coronary arteries

Endothelial wall shear stress (ESS) is a biomechanical force which plays a role in the formation and evolution of atherosclerotic lesions. The purpose of this study is to evaluate coronary computed tomography angiography (CCTA)-based ESS in coronary arteries without atherosclerosis, and to assess factors affecting ESS values. CCTA images from patients with suspected coronary artery disease were analyzed to identify coronary arteries without atherosclerosis. Minimal and maximal ESS values were calculated for 3-mm segments. Factors potentially affecting ESS values were examined, including sex, lumen diameter and distance from the ostium. Segments were categorized according to lumen diameter tertiles into small (< 2.6 mm), intermediate (2.6-3.2 mm) or large (≥ 3.2 mm) segments. A total of 349 normal vessels from 168 patients (mean age 59 ± 9 years, 39% men) were included. ESS was highest in the left anterior descending artery compared to the left circumflex artery and right coronary artery (minimal ESS 2.3 Pa vs. 1.9 Pa vs. 1.6 Pa, p < 0.001 and maximal ESS 3.7 Pa vs. 3.0 Pa vs. 2.5 Pa, p < 0.001). Men had lower ESS values than women, also after adjusting for lumen diameter (p < 0.001). ESS values were highest in small segments compared to intermediate or large segments (minimal ESS 3.8 Pa vs. 1.7 Pa vs. 1.2 Pa, p < 0.001 and maximal ESS 6.0 Pa vs. 2.6 Pa vs. 2.0 Pa, p < 0.001). A weak to strong correlation was found between ESS and distance from the ostium (ρ = 0.22-0.62, p < 0.001). CCTA-based ESS values increase rapidly and become widely scattered with decreasing lumen diameter. This needs to be taken into account when assessing the added value of ESS beyond lumen diameter in highly stenotic lesions.

Detailed behaviour of endothelial wall shear stress across coronary lesions from non-invasive imaging with coronary computed tomography angiography

AIMS

Evolving evidence suggests that endothelial wall shear stress (ESS) plays a crucial role in the rupture and progression of coronary plaques by triggering biological signalling pathways. We aimed to investigate the patterns of ESS across coronary lesions from non-invasive imaging with coronary computed tomography angiography (CCTA), and to define plaque-associated ESS values in patients with coronary artery disease (CAD).

METHODS AND RESULTS

Symptomatic patients with CAD who underwent a clinically indicated CCTA scan were identified. Separate core laboratories performed blinded analysis of CCTA for anatomical and ESS features of coronary atherosclerosis. ESS was assessed using dedicated software, providing minimal and maximal ESS values for each 3 mm segment. Each coronary lesion was divided into upstream, start, minimal luminal area (MLA), end and downstream segments. Also, ESS ratios were calculated using the upstream segment as a reference. From 122 patients (mean age 64 ± 7 years, 57% men), a total of 237 lesions were analyzed. Minimal and maximal ESS values varied across the lesions with the highest values at the MLA segment [minimal ESS 3.97 Pa (IQR 1.93-8.92 Pa) and maximal ESS 5.64 Pa (IQR 3.13-11.21 Pa), respectively]. Furthermore, minimal and maximal ESS values were positively associated with stenosis severity (P < 0.001), percent atheroma volume (P < 0.001), and lesion length (P ≤ 0.023) at the MLA segment. Using ESS ratios, similar associations were observed for stenosis severity and lesion length.

CONCLUSIONS

Detailed behaviour of ESS across coronary lesions can be derived from routine non-invasive CCTA imaging. This may further improve risk stratification.

Time-resolved fluorescence based direct two-site apoA-I immunoassays and their clinical application in patients with suspected obstructive coronary artery disease

Objective

High-density lipoprotein (HDL) is a heterogeneous group of subpopulations differing in protein/lipid composition and in their anti-atherogenic function. There is a lack of assays that can target the functionality of HDL particles related to atherosclerosis. The objective of this study was to construct two-site apolipoprotein A-I (apoA-I) assays and to evaluate their clinical performance in patients with suspected obstructive coronary artery disease (CAD).

Approach and results

Direct two-site apoA-I assays (named 109-121 and 110-525) were developed to identify the presence of apoA-I in the HDL of patients with CAD using apoA-I antibodies as a single-chain variable fragment fused with alkaline phosphatase. ApoA-I^109-121 and apoA-I^110-525 were measured in 197 patients undergoing coronary computed tomography angiography (CTA) and myocardial positron emission tomography perfusion imaging due to suspected obstructive CAD. Among patients not using lipid-lowering medication (LLM, n = 125), the level of apoA-I^110-525 was higher in the presence than in the absence of coronary atherosclerosis [21.88 (15.89-27.44) mg/dl vs. 17.66 (13.38-24.48) mg/dl, P = 0.01)], whereas there was no difference in apoA-I^109-121, HDL cholesterol, and apoA-I determined using a polyclonal apoA-I antibody. The levels of apoA-I^109-121 and apoA-I^110-525 were similar in the presence or absence of obstructive CAD. Among patients not using LLM, apoA-I^110-525 adjusted for age and sex identified individuals with coronary atherosclerosis with a similar accuracy to traditional risk factors [area under the curve [AUC] (95% CI): 0.75(0.66-0.84) 0.71 (0.62-0.81)]. However, a combination of apoA-I^110-525 with risk factors did not improve the accuracy [AUC (95% CI): 0.73 (0.64-0.82)].

Conclusion

Direct two-site apoA-I assays recognizing heterogeneity in reactivity with apoA-I could provide a potential approach to identify individuals at a risk of coronary atherosclerosis. However, their clinical value remains to be studied in larger cohorts.

Importance of plaque volume and composition for the prediction of myocardial ischaemia using sequential coronary computed tomography angiography/positron emission tomography imaging

AIMS

Coronary atherosclerosis with a large necrotic core has been postulated to reduce the vasodilatory capacity of vascular tissue. In the present analysis, we explored whether total plaque volume and necrotic core volume on coronary computed tomography angiography (CCTA) are independently associated with myocardial ischaemia on positron emission tomography (PET).

METHODS AND RESULTS

From a registry of symptomatic patients with suspected coronary artery disease and clinically indicated CCTA with sequential [15O]H2O PET myocardial perfusion imaging, we quantitatively measured diameter stenosis, total and compositional plaque volumes on CCTA. Primary endpoint was myocardial ischaemia on PET, defined as an absolute stress myocardial blood flow ≤2.4 mL/g/min in ≥1 segment. Multivariable prediction models for myocardial ischaemia were consecutively created using logistic regression analysis (stenosis model: diameter stenosis ≥50%; plaque volume model: +total plaque volume; plaque composition model: +necrotic core volume). A total of 493 patients (mean age 63 ± 8 years, 54% men) underwent sequential CCTA/PET imaging. In 153 (31%) patients, myocardial ischaemia was detected on PET. Diameter stenosis ≥50% (P < 0.001) and necrotic core volume (P = 0.029) were independently associated with myocardial ischaemia, while total plaque volume showed borderline significance (P = 0.052). The plaque composition model (χ2 = 169) provided incremental value for the prediction of ischaemia when compared with the stenosis model (χ2 = 138, P < 0.001) and plaque volume model (χ2 = 164, P = 0.021).

CONCLUSION

The volume of necrotic core on CCTA independently and incrementally predicts myocardial ischaemia on PET, beyond diameter stenosis alone.

Assessment of a digital and an analog PET/CT system for accurate myocardial perfusion imaging with a flow phantom

In Myocardial Perfusion Imaging (MPI) with Positron Emission Tomography/Computed Tomography (PET/CT) systems, accurate quantification is essential. We assessed flow quantification accuracy over various injected activities using a flow phantom.

METHODS

The study was performed on the digital 4-ring Discovery MI (DMI-20) and analog Discovery 690 (D690) PET/CT systems, using 325-1257 MBq of [15O]H2O. PET performance and flow quantification accuracy were assessed in terms of count-rates, dead-time factors (DTF), scatter fractions (SF), time-activity curves (TACs), areas-under-the-curves (AUCs) and flow values.

RESULTS

On DMI-20, prompts of 12.8 Mcps, DTF of 2.06 and SF of 46.1% were measured with 1257 MBq of activity. On the D690, prompts of 6.85 Mcps, DTF of 1.57 and SF of 32.5% were measured with 1230 MBq of activity. AUC values were linear over all activities. Mean wash-in flow error was - 9% for both systems whereas wash-out flow error was - 5% and - 6% for DMI-20 and D690. With the highest activity, wash-out flow error was - 12% and - 7% for the DMI-20 and D690.

CONCLUSION

DMI-20 and D690 preserved accurate flow quantification over all injected activities, with maximum error of - 12%. In the future, flow quantification accuracy over the activities and count-rates evaluated in this study should be assessed.

Perspectives in noninvasive imaging for chronic coronary syndromes

Both the latest European guidelines on chronic coronary syndromes and the American guidelines on chest pain have underlined the importance of noninvasive imaging to select patients to be referred to invasive angiography. Nevertheless, although coronary stenosis has long been considered the main determinant of inducible ischemia and symptoms, growing evidence has demonstrated the importance of other underlying mechanisms (e.g., vasospasm, microvascular disease, energetic inefficiency). The search for a pathophysiology-driven treatment of these patients has therefore emerged as an important objective of multimodality imaging, integrating "anatomical" and "functional" information. We here provide an up-to-date guide for the choice and the interpretation of the currently available noninvasive anatomical and/or functional tests, focusing on emerging techniques (e.g., coronary flow velocity reserve, stress-cardiac magnetic resonance, hybrid imaging, functional-coronary computed tomography angiography, etc.), which could provide deeper pathophysiological insights to refine diagnostic and therapeutic pathways in the next future.

Coronary Revascularization in Patients With Stable Coronary Artery Disease: The Role of Imaging

In the last decades, the effective management of some cardiovascular risk factors in the general population has led to a progressive decrease in the prevalence of coronary artery disease (CAD). Nevertheless, coronary heart disease remains the major cause of death in developed and developing countries and chronic coronary syndromes (CCS) are still a major target of utilization of non-invasive cardiac imaging and invasive procedures. Current guidelines recommend the use of non-invasive imaging in patients with CCS to identify subjects at higher risk to be referred for invasive coronary angiography and possible revascularization. These recommendations are challenged by two opposite lines of evidence. Recent trials have somewhat questioned the efficacy of coronary revascularization as compared with optimal medical therapy in CCS. As a consequence the role of imaging in these patients and in in patients with ischemic cardiomyopathy is under debate. On the other hand, real-life data indicate that a consistent proportion of patients undergo invasive procedure and are revascularized without any previous non-invasive imaging characterization. On top of this, the impact of COVID-19 pandemic on the sanitary systems caused a change in the current management of patients with CAD. In the present review we will discuss these conflicting data analyzing the evidence which has been recently accumulated as well as the gaps of knowledge which should still be filled.

Non-invasive Imaging in Coronary Syndromes - Recommendations of the European Association of Cardiovascular Imaging and the American Society of Echocardiography, in Collaboration with the American Society of Nuclear Cardiology, Society of Cardiovascular Computed Tomography and Society for Cardiovascular Magnetic Resonance

Coronary artery disease (CAD) is one of the major causes of mortality and morbidity worldwide, with a high socioeconomic impact.(1) Non-invasive imaging modalities play a fundamental role in the evaluation and management of patients with known or suspected CAD. Imaging end-points have served as surrogate markers in many observational studies and randomized clinical trials that evaluated the benefits of specific therapies for CAD.(2) A number of guidelines and recommendations have been published about coronary syndromes by cardiology societies and associations, but have not focused on the excellent opportunities with cardiac imaging. The recent European Society of Cardiology (ESC) 2019 guideline on chronic coronary syndromes (CCS) and 2020 guideline on acute coronary syndromes in patients presenting with non-ST-segment elevation (NSTE-ACS) highlight the importance of non-invasive imaging in the diagnosis, treatment, and risk assessment of the disease.(3)(4) The purpose of the current recommendations is to present the significant role of non-invasive imaging in coronary syndromes in more detail. These recommendations have been developed by the European Association of Cardiovascular Imaging (EACVI) and the American Society of Echocardiography (ASE), in collaboration with the American Society of Nuclear Cardiology, the Society of Cardiovascular Computed Tomography, and the Society for Cardiovascular Magnetic Resonance, all of which have approved the final document.

Anatomical and functional coronary imaging to predict long-term outcome in patients with suspected coronary artery disease: the EVINCI-outcome study

AIMS

To investigate the prognostic relevance of coronary anatomy, coronary function, and early revascularization in patients with stable coronary artery disease (CAD).

METHODS AND RESULTS

From March 2009 to June 2012, 430 patients with suspected CAD (61 ± 9 years, 62% men) underwent coronary anatomical imaging by computed tomography coronary angiography (CTCA) and coronary functional imaging followed by invasive coronary angiography (ICA) if at least one non-invasive test was abnormal. Obstructive CAD was documented by ICA in 119 patients and 90 were revascularized within 90 days of enrolment. Core laboratory analysis showed that 134 patients had obstructive CAD by CTCA (>50% stenosis in major coronary vessels) and 79 significant ischaemia by functional imaging [>10% left ventricular (LV) myocardium]. Over mean follow-up of 4.4 years, major adverse events (AEs) (all-cause death, non-fatal myocardial infarction, or hospital admission for unstable angina or heart failure) or AEs plus late revascularization (LR) occurred in 40 (9.3%) and 58 (13.5%) patients, respectively. Obstructive CAD at CTCA was the only independent imaging predictor of AEs [hazard ratio (HR) 3.2, 95% confidence interval (CI) 1.10-9.30; P = 0.033] and AEs plus LR (HR 4.3, 95% CI 1.56-11.81; P = 0.005). Patients with CAD in whom early revascularization was performed in the presence of ischaemia and deferred in its absence had fewer AEs, similar to patients without CAD (HR 2.0, 95% CI 0.71-5.51; P = 0.195).

CONCLUSION

Obstructive CAD imaged by CTCA is an independent predictor of clinical outcome. Early management of CAD targeted to the combined anatomical and functional disease phenotype improves clinical outcome.

Incremental prognostic value of hybrid [15O]H2O positron emission tomography-computed tomography: combining myocardial blood flow, coronary stenosis severity, and high-risk plaque morphology

Aims 

This study sought to determine the prognostic value of combined functional testing using positron emission tomography (PET) perfusion imaging and anatomical testing using coronary computed tomography angiography (CCTA)-derived stenosis severity and plaque morphology in patients with suspected coronary artery disease (CAD).

Methods and results 

In this retrospective study, 539 patients referred for hybrid [¹⁵O]H₂O PET-CT imaging because of suspected CAD were investigated. PET was used to determine myocardial blood flow (MBF), whereas CCTA images were evaluated for obstructive stenoses and high-risk plaque (HRP) morphology. Patients were followed up for the occurrence of all-cause death and non-fatal myocardial infarction (MI). During a median follow-up of 6.8 (interquartile range 4.8–7.8) years, 42 (7.8%) patients experienced events, including 23 (4.3%) deaths, and 19 (3.5%) MIs. Annualized event rates for normal vs. abnormal results of PET MBF, CCTA-derived stenosis, and HRP morphology were 0.6 vs. 2.1%, 0.4 vs. 2.1%, and 0.8 vs. 2.8%, respectively (P < 0.001 for all). Cox regression analysis demonstrated prognostic values of PET perfusion imaging [hazard ratio (HR) 3.75 (1.84–7.63), P < 0.001], CCTA-derived stenosis [HR 5.61 (2.36–13.34), P < 0.001], and HRPs [HR 3.37 (1.83–6.18), P < 0.001] for the occurrence of death or MI. However, only stenosis severity [HR 3.01 (1.06–8.54), P = 0.039] and HRPs [HR 1.93 (1.00–3.71), P = 0.049] remained independently associated.

Conclusion 

PET-derived MBF, CCTA-derived stenosis severity, and HRP morphology were univariably associated with death and MI, whereas only stenosis severity and HRP morphology provided independent prognostic value.

Cardiac perfusion by positron emission tomography

Myocardial perfusion imaging (MPI) with positron emission tomography (PET) is an established tool for evaluation of obstructive coronary artery disease (CAD). The contemporary 3-dimensional scanner technology and the state-of-the-art MPI radionuclide tracers and pharmacological stress agents, as well as the cutting-edge image reconstruction techniques and data analysis software, have all enabled accurate, reliable and reproducible quantification of absolute myocardial blood flow (MBF), and henceforth calculation of myocardial flow reserve (MFR) in several clinical scenarios. In patients with suspected coronary artery disease, both absolute stress MBF and MFR can identify myocardial territories subtended by epicardial coronary arteries with haemodynamically significant stenosis, as defined by invasive coronary fractional flow reserve measurement. In particular, absolute stress MBF and MFR offered incremental prognostic information for predicting adverse cardiac outcome, and hence for better patient risk stratification, over those provided by traditional clinical risk predictors. This article reviews the available evidence to support the translation of the current techniques and technologies into a useful decision-making tool in real-world clinical practice.

Improving patient identification for advanced cardiac imaging through machine learning-integration of clinical and coronary CT angiography data

BACKGROUND

Standard computed tomography angiography (CTA) outputs a myriad of interrelated variables in the evaluation of suspected coronary artery disease (CAD). But an important proportion of obstructive lesions does not cause significant myocardial ischemia. Nowadays, machine learning (ML) allows integration of numerous variables through complex interdependencies that optimize classification and prediction at the individual level. We evaluated ML performance in integrating CTA and clinical variables to identify patients that demonstrate myocardial ischemia through PET and those who ultimately underwent early revascularization.

METHODS AND RESULTS

830 patients with CTA and selective PET were analyzed. Nine clinical and 58 CTA variables were integrated through ensemble-boosting ML to identify patients with ischemia and those who underwent early revascularization. ML performance was compared against expert CTA interpretation, calcium score and clinical variables. While ML using all CTA variables achieved an AUC = 0.85, it was outperformed by expert CTA interpretation (AUC = 0.87, p < 0.01 for comparison), comparable to ML integration of CTA variables with clinical variables. However, the best performance was achieved by ML integration of expert CTA interpretation and clinical variables for both dependent variables (AUCs = 0.91 and 0.90, p < 0.001).

CONCLUSIONS

Machine learning integration of diagnostic CTA and clinical data may improve identification of patients with myocardial ischemia and those requiring early revascularization at the individual level. This could potentially aid in sparing the need for subsequent advanced imaging and better identifying patients in ultimate need for revascularization. While ML integrating all CTA variables did not outperform expert CTA interpretation, ML data integration from different sources consistently improves diagnostic performance.

Global and segmental absolute stress myocardial blood flow in prediction of cardiac events: [15O] water positron emission tomography study

Purpose

We evaluated the value of reduced global and segmental absolute stress myocardial blood flow (sMBF) quantified by [¹⁵O] water positron emission tomography (PET) for predicting cardiac events in patients with suspected obstructive coronary artery disease (CAD).

Methods

Global and segmental sMBF during adenosine stress were retrospectively quantified in 530 symptomatic patients who underwent [¹⁵O] water PET for evaluation of coronary stenosis detected by coronary computed tomography angiography.

Results

Cardiovascular death, myocardial infarction, or unstable angina occurred in 28 (5.3%) patients at a 4-year follow-up. Reduced global sMBF was associated with events (area under the receiver operating characteristic curve 0.622, 95% confidence interval (95% CI) 0.538–0.707, p = 0.006). Reduced global sMBF (< 2.2 ml/g/min) was found in 22.8%, preserved global sMBF despite segmentally reduced sMBF in 35.3%, and normal sMBF in 41.9% of patients. Compared with normal sMBF, reduced global sMBF was associated with the highest risk of events (adjusted hazard ratio (HR) 6.970, 95% CI 2.271–21.396, p = 0.001), whereas segmentally reduced sMBF combined with preserved global MBF predicted an intermediate risk (adjusted HR 3.251, 95% CI 1.030–10.257, p = 0.044). The addition of global or segmental reduction of sMBF to clinical risk factors improved risk prediction (net reclassification index 0.498, 95% CI 0.118–0.879, p = 0.010, and 0.583, 95% CI 0.203–0.963, p = 0.002, respectively).

Conclusion

In symptomatic patients evaluated for suspected obstructive CAD, reduced global sMBF by [¹⁵O] water PET identifies those at the highest risk of adverse cardiac events, whereas segmental reduction of sMBF with preserved global sMBF is associated with an intermediate event risk.

EANM procedural guidelines for PET/CT quantitative myocardial perfusion imaging

The use of cardiac PET, and in particular of quantitative myocardial perfusion PET, has been growing during the last years, because scanners are becoming widely available and because several studies have convincingly demonstrated the advantages of this imaging approach. Therefore, there is a need of determining the procedural modalities for performing high-quality studies and obtaining from this demanding technique the most in terms of both measurement reliability and clinical data. Although the field is rapidly evolving, with progresses in hardware and software, and the near perspective of new tracers, the EANM Cardiovascular Committee found it reasonable and useful to expose in an updated text the state of the art of quantitative myocardial perfusion PET, in order to establish an effective use of this modality and to help implementing it on a wider basis. Together with the many steps necessary for the correct execution of quantitative measurements, the importance of a multiparametric approach and of a comprehensive and clinically useful report have been stressed.

[Surgery 4.0-are we ready?]

The increasing networking of data systems in medicine is not only leading to modern interdisciplinarity in the sense of cooperation between different medical departments, but also poses new challenges regarding the building and room infrastructure. The surgical operating room of the future expands or augments its reality, away from the pure building characteristics, towards an intelligent and communicative space platform. The building infrastructure (operating theatre) serves as sensor and actuator. Thus, it is possible to inform about missing diagnostics as well as to register them directly in the contextualization of the planned surgical intervention or to integrate them into the processes. Integrated operating theatres represent a comprehensive computer platform based on a corresponding system architecture with software-based protocols. An underlying modular system consisting of various modules for image acquisition and analysis, interaction and visualization supports the integration and merging of heterogeneous data that are generated in a hospital operation. Integral building data (e.g., air conditioning, lighting control, device registration) are merged with patient-related data (age, type of illness, concomitant diseases, existing diagnostic CT and MRI images). New systems coming onto the market, as well as already existing systems will have to be measured by the extent to which they will be able to guarantee this integration of information-similar to the development from mobile phone to smartphone. Cost reduction should not be the only legitimizing argument for the market launch, but the vision of a new quality of surgical perception and action.

Percutaneous or surgical revascularization is associated with survival benefit in stable coronary artery disease

Aims 

We assessed the association between early invasive therapy, burden of ischaemia, and survival benefit separately for percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG). Ischaemia involving more than 10% of the left ventricular myocardium may identify patients who benefit from revascularization. However, it is not clear whether this association exists with both PCI and CABG.

Materials and results

Patients who underwent single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) between 1992 and 2012 were identified. Early revascularization was defined as PCI or CABG performed within 90 days of SPECT MPI. The association between early PCI or CABG and all-cause mortality was assessed using a doubly robust, propensity score matching analysis. In total, 54 522 patients were identified, with median follow-up 8.0 years. Early PCI was performed in 2688 patients and early CABG in 1228. In the matched cohorts, early revascularization was associated with improved survival compared to medical therapy in patients with more than 15% ischaemia for both PCI [adjusted hazard ratio (HR) 0.70, P = 0.002] and CABG (adjusted HR 0.73, P = 0.008).

Conclusion 

In this observational analysis, both PCI and CABG were associated with reduced all-cause mortality in the presence of moderate to severe ischaemia after adjusting for factors leading to revascularization. As the threshold for improved outcomes with revascularization was similar for PCI and CABG, our results suggest that decisions for PCI vs. CABG for early revascularization should be determined by coronary anatomy, patient characteristics, and shared decision making, but not by the burden of ischaemia.

15O-Water PET MPI: Current Status and Future Perspectives

Myocardial perfusion imaging with 15O-water positron emission tomography (PET) is a validated tool for quantitative measurement of myocardial blood flow (MBF) and myocardial flow reserve (MFR). Current scanner and software technology enable quantification of global and regional MBF in clinical PET myocardial perfusion imaging studies. Reduced stress MBF or MFR measured by 15O-water PET accurately detects hemodynamically significant coronary artery stenosis defined by intracoronary fractional flow reserve (FFR) measurement in patients with suspected obstructive coronary artery disease (CAD). Furthermore, MBF and MFR provide prognostic information on mortality and risk of myocardial infarction. Clinical experience in some centers indicates that clinical application of 15O-water PET in evaluation of CAD is feasible and guides management decisions on revascularization. This review discusses basic concepts of measuring MBF with 15O-water PET and reviews clinical studies on its application in evaluation of obstructive CAD.

The performance of non-invasive tests to rule-in and rule-out significant coronary artery stenosis in patients with stable angina: a meta-analysis focused on post-test disease probability

Aims

To determine the ranges of pre-test probability (PTP) of coronary artery disease (CAD) in which stress electrocardiogram (ECG), stress echocardiography, coronary computed tomography angiography (CCTA), single-photon emission computed tomography (SPECT), positron emission tomography (PET), and cardiac magnetic resonance (CMR) can reclassify patients into a post-test probability that defines (>85%) or excludes (<15%) anatomically (defined by visual evaluation of invasive coronary angiography [ICA]) and functionally (defined by a fractional flow reserve [FFR] ≤0.8) significant CAD.

Methods and results

A broad search in electronic databases until August 2017 was performed. Studies on the aforementioned techniques in >100 patients with stable CAD that utilized either ICA or ICA with FFR measurement as reference, were included. Study-level data was pooled using a hierarchical bivariate random-effects model and likelihood ratios were obtained for each technique. The PTP ranges for each technique to rule-in or rule-out significant CAD were defined. A total of 28 664 patients from 132 studies that used ICA as reference and 4131 from 23 studies using FFR, were analysed. Stress ECG can rule-in and rule-out anatomically significant CAD only when PTP is ≥80% (76-83) and ≤19% (15-25), respectively. Coronary computed tomography angiography is able to rule-in anatomic CAD at a PTP ≥58% (45-70) and rule-out at a PTP ≤80% (65-94). The corresponding PTP values for functionally significant CAD were ≥75% (67-83) and ≤57% (40-72) for CCTA, and ≥71% (59-81) and ≤27 (24-31) for ICA, demonstrating poorer performance of anatomic imaging against FFR. In contrast, functional imaging techniques (PET, stress CMR, and SPECT) are able to rule-in functionally significant CAD when PTP is ≥46-59% and rule-out when PTP is ≤34-57%.

Conclusion

The various diagnostic modalities have different optimal performance ranges for the detection of anatomically and functionally significant CAD. Stress ECG appears to have very limited diagnostic power. The selection of a diagnostic technique for any given patient to rule-in or rule-out CAD should be based on the optimal PTP range for each test and on the assumed reference standard.

Prognostic value of [15O]H2O positron emission tomography-derived global and regional myocardial perfusion

Aims

To evaluate the prognostic value of global and regional quantitative [15O]H2O positron emission tomography (PET) perfusion.

Methods and results

In this retrospective study, 648 patients with suspected or known coronary artery disease (CAD) who underwent [15O]H2O PET were followed for the occurrence of death and myocardial infarction (MI). Global and regional hyperaemic myocardial blood flow (hMBF) and coronary flow reserve (CFR) were obtained from [15O]H2O PET. During median follow-up of 6.9 (5.0–7.9) years, 64 (9.9%) patients experienced the composite of death (36–5.6%) and MI (28–4.3%). Impaired global hMBF (&lt;2.65 mL/min/g) and CFR (&lt;2.88) were both significant prognostic factors for death/MI after adjusting for clinical characteristics (both P &lt; 0.001). However, after adjusting for clinical parameters and the combined use of hMBF and CFR, only hMBF remained an independent prognostic factor (P = 0.04). For regional perfusion, both impaired hMBF (&lt;2.10 mL/min/g) and CFR (&lt;2.07) demonstrated prognostic value for events (both P &lt; 0.001). Similarly, after adjusting for clinical characteristics and combined use of hMBF and CFR, only hMBF had independent prognostic value (P = 0.04). The combination of global and regional perfusion did not improve prognostic performance over either global (P = 0.55) or regional perfusion (P = 0.37) alone.

Conclusion

Global and regional hMBF and CFR were all prognostic factors for death and MI. However, for both global and regional perfusion, hMBF remained the only independent prognostic factor after adjusting for the combined use of hMBF and CFR. Additionally, integrating global and regional perfusion did not increase prognostic performance compared to either regional or global perfusion alone.

The clinical utility of hybrid imaging for the identification of vulnerable plaque and vulnerable patients

Despite decades of research and major innovations in technology, cardiovascular disease remains the leading cause of death globally. Our understanding of major cardiovascular events and their prevention is centred around the atherosclerotic plaque and the processes that ultimately lead to acute plaque rupture. Recent advances in hybrid imaging technology allow the combination of high spatial resolution and anatomical detail with molecular assessments of disease activity. This provides the ability to identify vulnerable plaque characteristics and differentiate active and quiescent disease, with the potential to improve patient risk stratification. Combined positron emission tomography and computed tomography is the prototypical non-invasive hybrid imaging technique for coronary artery plaque assessment. In this review we discuss the current state of play in the field of hybrid coronary atherosclerosis imaging.

Quantitative myocardial perfusion evaluation with positron emission tomography and the risk of cardiovascular events in patients with coronary artery disease: a systematic review of prognostic studies

Aims

To evaluate the prognostic value of quantitative myocardial perfusion imaging with positron emission tomography (PET) for adverse cardiovascular outcomes in patients with known or suspected coronary artery disease (CAD).

Methods and results

A search in MEDLINE and Embase was conducted for studies that evaluated (i) myocardial perfusion in absolute terms with PET, (ii) prognostic value for the development of major adverse cardiovascular events (MACE), cardiac death, and/or all-cause mortality, and (iii) patients with known or suspected CAD. Studies were divided according to the radiotracer utilized and their included population (patients with and without previous infarction). Comprehensive description and a selected instance of pooling were performed. Eight studies (n = 6804) were analysed and documented clear variability in population, quantitative PET variables operationalization [stress myocardial blood flow (sMBF) and flow reserve (MFR)], statistical covariate structure, follow-up, and radiotracer utilized. MFR was independently associated with MACE in eight studies [range of adjusted hazard ratios (HRs): 1.19–2.93]. The pooling instance demonstrated that MFR significantly associates with the development of MACEs (HR: 1.92 [1.29, 2.84]; P = 0.001). sMBF was only associated with MACE in two studies that evaluated it, and only one study documented sMBF as a better predictor than MFR.

Conclusion

This systematic review demonstrates the prognostic value of quantitative myocardial perfusion evaluated with PET, in the form of MFR and sMBF, for the development of major adverse cardiovascular outcomes in populations with known or suspected CAD. In the qualitative comparison, MFR seems to outperform sMBF as an independent prognostic factor. Evidence is still lacking for assessing quantitative PET for the occurrence of cardiac death and all-cause mortality. There is clear heterogeneity in predictor operationalization and study performances.

Influence of Cardiac CT based disease severity and clinical symptoms on the diagnostic performance of myocardial perfusion

We aimed to identify factors influencing the sensitivity of perfusion imaging after an initial positive coronary computed tomography angiography (CCTA) using invasive coronary angiography (ICA) with conditional fractional flow reserve (FFR) as reference. Secondly we aimed to identify factors associated with revascularisation and to evaluate treatment outcome after ICA. We analysed 292 consecutive patients with suspected significant coronary artery disease (CAD) at CCTA, who underwent perfusion imaging with either cardiac magnetic resonance (CMR) or myocardial perfusion scintigraphy (MPS) followed by ICA with conditional FFR. Stratified analysis and uni- and multiple logistic regression analyses were performed to identify predictors of diagnostic agreement between perfusion scans and ICA and predictors of revascularisation. Myocardial ischemia evaluated with perfusion scans was present in 65/292 (22%) while 117/292 (40%) had obstructive CAD evaluated by ICA. Revascularisation rate was 90/292 (31%). The overall sensitivity for perfusion scans was 39% (30-48), specificity 89% (83-93), PPV 69% (57-80) and NPV 68% (62-74). Stratified analysis showed higher sensitivities in patients with multi-vessel disease at CCTA 49% (37-60) and typical chest pain 50% (37-60). Predictors of revascularisation were multi-vessel disease by CCTA (OR 3.51 [1.91-6.48]) and a positive perfusion scan (OR 4.69 [2.49-8.83]). The sensitivity for perfusion scans after CCTA was highest in patients with typical angina and multiple lesions at CCTA and predicted diagnostic agreement between perfusion scans and ICA. Abnormal perfusion and multi vessel disease at CCTA predicted revascularisation.

PET-Based Imaging of Ischemic Heart Disease

PET-based cardiac nuclear imaging plays a large role in the management of ischemic heart disease. Compared with conventional single-photon emission CT myocardial perfusion imaging, PET provides superior accuracy in diagnosis of coronary artery disease and, with the incorporation of myocardial blood flow and coronary flow reserve, adds value in assessing prognosis for established coronary and microvascular disease. This review describes these and other uses of PET in ischemic heart disease, including assessing myocardial viability in ischemic cardiomyopathy. Developments in novel PET flow tracers and molecular imaging tools to assess atherosclerotic plaque vulnerability, vascular calcification, and vascular remodeling also are described.

Hybrid coronary computed tomography angiography and positron emission tomography myocardial perfusion imaging in evaluation of recurrent symptoms after coronary artery bypass grafting

Aims

Recurrent chest pain after coronary artery bypass grafting (CABG) poses a diagnostic challenge. We hypothesized that combining anatomy of bypass grafts and native coronary arteries with ischaemia detection by hybrid imaging could be used to gain valuable and complementary information in patients with recurrent symptoms after CABG.

Methods and results

We analysed 36 consecutive patients (67 ± 9 years, 81% male) who had undergone hybrid imaging using coronary computed tomography angiography (CCTA) and [15O]H2O positron emission tomography (PET) myocardial perfusion imaging due to recurrent symptoms after CABG. Coronary tree and left ventricular myocardium were divided into three main territories, yielding a total of 108 coronary territories in 36 patients. The presence of obstructive (≥50%) stenosis and the patency of grafts were evaluated by CCTA, while myocardial ischaemia was assessed by quantitative adenosine-stress PET. Altogether 28 (78%) of the 36 study patients presented with matched PET/CCTA abnormalities. Forty-one coronary territories were supplied by non-obstructed bypass grafts or native coronary arteries (protected territory). However, 12 (29%) of these presented with a perfusion defect. In six cases, the perfusion defect involved myocardium distal to the graft-coronary anastomosis, as interpreted on the PET/CCTA fusion images. In turn, in 48 coronary territories the supplying artery was obstructed on CCTA (unprotected territory). Of these, 41 (85%, P < 0.001 vs. protected) presented with abnormal perfusion, involving myocardium distal to the anastomosis in 29 cases.

Conclusion

Hybrid imaging provides complementary information on the presence and localization of atherosclerotic lesions and myocardial perfusion abnormalities in symptomatic patients with previous CABG.