The Belgian Registry on Coronary Function Testing (BELmicro Registry): Study Population, Prevalence of Coronary Vascular Dysfunction, and Procedural Safety

Coronary function testing (CFT) plays a pivotal role in the diagnosis of coronary vascular dysfunction and providing patients with tailored therapy. The Belgian registry on CFT (BELmicro registry) is a prospective, observational, multicenter registry including 14 centers in Belgium. All patients who underwent clinically indicated CFT were included in the registry. Baseline characteristics, CFT data, and clinical outcomes were collected. This analysis aimed to describe the baseline characteristics of a real-world population of patients who underwent CFT, evaluate the prevalence of coronary vascular dysfunction, and assess the safety of CFT in daily clinical practice. Between October 2021 and September 2023, 449 patients were enrolled. The mean age was 65 ± 10 years, and 47.4% of patients were men. A total of 59% of patients had hypertension, 18.7% had diabetes, 69.5% had hypercholesterolemia, and 40.1% had a smoking habit. Angina and nonobstructive coronary arteries (ANOCAs) were identified in 85.1% of the patients. Microvascular physiology assessment was performed in 95.5% of patients, vasoreactivity test in 28.5%, and both in 24.0%. coronary microvascular dysfunction was diagnosed in 23.4% of patients with ANOCA, epicardial vasospasm in 26.3%, and microvascular spasm in 14.9%. Rates of major complications were 0.7% for microvascular physiology assessment and 0% for vasoreactivity test. In conclusion, participants in the BELmicro registry represented a real-world population of patients, characterized by a high burden of cardiovascular risk factors. Coronary microvascular dysfunction and coronary vasospasm were frequent in patients with ANOCA. Performing CFT in daily clinical practice was feasible, with a low rate of complications.

Coronary Microvascular Spasm: Clinical Presentation and Diagnosis

Professor Maseri pioneered the research and treatment of coronary vasomotion abnormalities represented by coronary vasospasm and coronary microvascular dysfunction (CMD). These mechanisms can cause myocardial ischaemia even in the absence of obstructive coronary artery disease, and have been appreciated as an important aetiology and therapeutic target with major clinical implications in patients with ischaemia with non-obstructive coronary artery disease (INOCA). Coronary microvascular spasm is one of the key mechanisms responsible for myocardial ischaemia in patients with INOCA. Comprehensive assessment of coronary vasomotor reactivity by invasive functional coronary angiography or interventional diagnostic procedure is recommended to identify the underlying mechanisms of myocardial ischaemia and to tailor the best treatment and management based on the endotype of INOCA. This review highlights the pioneering works of Professor Maseri and contemporary research on coronary vasospasm and CMD with reference to endothelial dysfunction, Rho-kinase activation and inflammation.

Pathophysiology and Outcomes of Endothelium Function in Coronary Microvascular Diseases: A Systematic Review of Randomized Controlled Trials and Multicenter Study

BACKGROUND

Coronary macrovascular disease is a concept that has been well-studied within the literature and has long been the subject of debates surrounding coronary artery bypass grafting (CABG) vs. Percutaneous Coronary Intervention (PCI). ISCHEMIA trial reported no statistical difference in the primary clinical endpoint between initial invasive management and initial conservative management, while in the ORBITA trial PCI did not improve angina frequency score significantly more than placebo, albeit PCI resulted in more patient-reported freedom from angina than placebo. However, these results did not prove the superiority of the PCI against OMT, therefore do not indicate the benefit of PCI vs. the OMT. Please rephrase the sentence. We reviewed the role of different factors responsible for endothelial dysfunction from recent randomized clinical trials (RCTs) and multicentre studies.

METHODS

A detailed search strategy was performed using a dataset that has previously been published. Data of pooled analysis include research articles (human and animal models), CABG, and PCI randomized controlled trials (RCTs). Details of the search strategy and the methods used for data pooling have been published previously and registered with Open-Source Framework.

RESULTS

The roles of nitric oxide (NO), endothelium-derived contracting factors (EDCFs), and vasodilator prostaglandins (e.g., prostacyclin), as well as endothelium-dependent hyperpolarization (EDH) factors, are crucial for the maintenance of vasomotor tone within the coronary vasculature. These homeostatic mechanisms are affected by sheer forces and other several factors that are currently being studied, such as vaping. The role of intracoronary testing is crucial when determining the effects of therapeutic medications with further studies on the horizon.

CONCLUSION

The true impact of coronary microvascular dysfunction (CMD) is perhaps underappreciated, which supports the role of medical therapy in determining outcomes. Ongoing trials are underway to further investigate the role of therapeutic agents in secondary prevention.

Machine Learning From Quantitative Coronary Computed Tomography Angiography Predicts Fractional Flow Reserve-Defined Ischemia and Impaired Myocardial Blood Flow

BACKGROUND

A pathophysiological interplay exists between plaque morphology and coronary physiology. Machine learning (ML) is increasingly being applied to coronary computed tomography angiography (CCTA) for cardiovascular risk stratification. We sought to assess the performance of a ML score integrating CCTA-based quantitative plaque features for predicting vessel-specific ischemia by invasive fractional flow reserve (FFR) and impaired myocardial blood flow (MBF) by positron emission tomography (PET).

METHODS

This post-hoc analysis of the PACIFIC trial (Prospective Comparison of Cardiac Positron Emission Tomography/Computed Tomography [CT]' Single Photon Emission Computed Tomography/CT Perfusion Imaging and CT Coronary Angiography with Invasive Coronary Angiography) included 208 patients with suspected coronary artery disease who prospectively underwent CCTA' [15O]H2O PET, and invasive FFR. Plaque quantification from CCTA was performed using semiautomated software. An ML algorithm trained on the prospective NXT trial (484 vessels) was used to develop a ML score for the prediction of ischemia (FFR≤0.80), which was then evaluated in 581 vessels from the PACIFIC trial. Thereafter, the ML score was applied for predicting impaired hyperemic MBF (≤2.30 mL/min per g) from corresponding PET scans. The performance of the ML score was compared with CCTA reads and noninvasive FFR derived from CCTA (FFRCT).

RESULTS

One hundred thirty-nine (23.9%) vessels had FFR-defined ischemia, and 195 (33.6%) vessels had impaired hyperemic MBF. For the prediction of FFR-defined ischemia, the ML score yielded an area under the receiver-operating characteristic curve of 0.92, which was significantly higher than that of visual stenosis grade (0.84; P<0.001) and comparable with that of FFRCT (0.93; P=0.34). Quantitative percent diameter stenosis and low-density noncalcified plaque volume had the greatest ML feature importance for predicting FFR-defined ischemia. When applied for impaired MBF prediction, the ML score exhibited an area under the receiver-operating characteristic curve of 0.80; significantly higher than visual stenosis grade (area under the receiver-operating characteristic curve 0.74; P=0.02) and comparable with FFRCT (area under the receiver-operating characteristic curve 0.77; P=0.16).

CONCLUSIONS

An externally validated ML score integrating CCTA-based quantitative plaque features accurately predicts FFR-defined ischemia and impaired MBF by PET, performing superiorly to standard CCTA stenosis evaluation and comparably to FFRCT.

Brain-Derived Neurotrophic Factor And Coronary Artery Disease

Coronary artery disease (CAD) is defined as myocardial damage developing as a result of its organic and functional changes, and leading to impaired blood flow through the coronary arteries. An important pathogenetic component of CAD is atherosclerosis. Currently, key aspects of the molecular relationship between inflammation and atherosclerosis are being actively studied, the immunometabolic theory of atherosclerosis is being discussed, along with an involvement of perivascular adipose tissue in the pathogenesis of this pathology, due to its ability to respond to atherogenic stimuli via developing inflammatory reactions. Evidence has been accumulated that in patients with CAD, both in their blood and perivascular adipose tissue, the level of neurotrophic factors (in particular, brain-derived neurotrophic factor, BDNF) changes, which may be a promising area of research from the standpoint of studying this factor as a therapeutic target for atherosclerosis in CAD. Neurotrophic growth factors control the functioning of both immune and nervous systems, and the balance of energy metabolism and innervation of adipose tissue. They affect vascular homeostasis, and are also involved in causing and stopping inflammation. Currently, there are data on the role of BDNF in the pathogenesis of cardiovascular, neurodegenerative and metabolic diseases, and on the effect of polyunsaturated fatty acids and eicosanoids on the level of BDNF and, accordingly, the development and progression of coronary artery atherosclerosis. Our review summarizes published data (2019-2021) on the pathophysiological and pathogenetic mechanisms of the relationship between BDNF and CAD (atherosclerosis).

Plasma Ceramide Levels Are Elevated in Patients With Early Coronary Atherosclerosis and Endothelial Dysfunction

Background

Elevated plasma ceramides are independent predictors of cardiovascular disease and mortality in patients with advanced epicardial coronary artery disease. Our understanding of plasma ceramides in early epicardial coronary artery disease, however, remains limited. We examined the role of plasma ceramides in early coronary atherosclerosis characterized by coronary endothelial dysfunction.

Methods and Results

Participants presenting with chest pain and nonobstructive epicardial coronary artery disease underwent coronary endothelial function. Patients (n=90) demonstrated abnormal coronary endothelial function with acetylcholine (≥20% decrease in coronary artery diameter or ≤50% increase in coronary blood flow). A total of 30 controls had normal coronary endothelial function. Concentrations of plasma ceramide 18:0 (P=0.038), 16:0 (P=0.021), and 24:0 (P=0.019) differed between participants with normal and abnormal coronary endothelial function. Ceramide 24:0 (odds ratio [OR], 2.23 [95% CI, 1.07–4.66]; P=0.033) and 16:0 (OR, 1.91×10⁶ [95% CI, 11.93–3.07×10¹¹]; P=0.018) were independently associated with coronary endothelial dysfunction. Among participants with endothelium‐dependent coronary dysfunction (n=78), ceramides 16:0 (OR, 5.17×10⁵ [95% CI, 2.83–9.44×10¹⁰]; P=0.033), 24:0 (OR, 2.98 [95% CI, 1.27–7.00]; P=0.012), and 24:1/24:0 (OR, 4.39×10⁻⁴ [95% CI, 4×10⁻⁷–0.48]; P=0.030) were more likely to be elevated.

Conclusions

The current study demonstrated an association between increased circulating ceramide levels and coronary endothelial dysfunction in the absence of epicardial coronary artery disease. This study supports the role of plasma ceramides as a potential biomarker or a therapeutic target for early coronary atherosclerosis in humans.

Prevalence of Coronary Microvascular Disease and Coronary Vasospasm in Patients With Nonobstructive Coronary Artery Disease: Systematic Review and Meta-Analysis

Background

A relevant proportion of patients with suspected coronary artery disease undergo invasive coronary angiography showing normal or nonobstructive coronary arteries. However, the prevalence of coronary microvascular disease (CMD) and coronary spasm in patients with nonobstructive coronary artery disease remains to be determined. The objective of this study was to determine the prevalence of coronary CMD and coronary vasospastic angina in patients with no obstructive coronary artery disease.

Methods and Results

A systematic review and meta‐analysis of studies assessing the prevalence of CMD and vasospastic angina in patients with no obstructive coronary artery disease was performed. Random‐effects models were used to determine the prevalence of these 2 disease entities. Fifty‐six studies comprising 14 427 patients were included. The pooled prevalence of CMD was 0.41 (95% CI, 0.36–0.47), epicardial vasospasm 0.40 (95% CI, 0.34–0.46) and microvascular spasm 24% (95% CI, 0.21–0.28). The prevalence of combined CMD and vasospastic angina was 0.23 (95% CI, 0.17–0.31). Female patients had a higher risk of presenting with CMD compared with male patients (risk ratio, 1.45 [95% CI, 1.11–1.90]). CMD prevalence was similar when assessed using noninvasive or invasive diagnostic methods.

Conclusions

In patients with no obstructive coronary artery disease, approximately half of the cases were reported to have CMD and/or coronary spasm. CMD was more prevalent among female patients. Greater awareness among physicians of ischemia with no obstructive coronary arteries is urgently needed for accurate diagnosis and patient‐tailored management.

Endothelium in Coronary Macrovascular and Microvascular Diseases

ABSTRACT

The endothelium plays a pivotal role in the regulation of vascular tone by synthesizing and liberating endothelium-derived relaxing factors inclusive of vasodilator prostaglandins (eg, prostacyclin), nitric oxide (NO), and endothelium-dependent hyperpolarization factors in a distinct blood vessel size-dependent manner. Large conduit arteries are predominantly regulated by NO and small resistance arteries by endothelium-dependent hyperpolarization factors. Accumulating evidence over the past few decades has demonstrated that endothelial dysfunction and coronary vasomotion abnormalities play crucial roles in the pathogenesis of various cardiovascular diseases. Structural and functional alterations of the coronary microvasculature have been coined as coronary microvascular dysfunction (CMD), which is highly prevalent and associated with adverse clinical outcomes in many clinical settings. The major mechanisms of coronary vasomotion abnormalities include enhanced coronary vasoconstrictive reactivity at epicardial and microvascular levels, impaired endothelium-dependent and endothelium-independent coronary vasodilator capacities, and elevated coronary microvascular resistance caused by structural factors. Recent experimental and clinical research has highlighted CMD as the systemic small artery disease beyond the heart, emerging modulators of vascular functions, novel insights into the pathogenesis of cardiovascular diseases associated with CMD, and potential therapeutic interventions to CMD with major clinical implications. In this article, we will summarize the current knowledge on the endothelial modulation of vascular tone and the pathogenesis of coronary macrovascular and microvascular diseases from bench to bedside, with a special emphasis placed on the mechanisms and clinical implications of CMD.

Machine learning aids clinical decision-making in patients presenting with angina and non-obstructive coronary artery disease

Aims

The current gold standard comprehensive assessment of coronary microvascular dysfunction (CMD) is through a limited-access invasive catheterization lab procedure. We aimed to develop a point-of-care tool to assist clinical guidance in patients presenting with chest pain and/or an abnormal cardiac functional stress test and with non-obstructive coronary artery disease (NOCAD).

Methods and results

This study included 1893 NOCAD patients (<50% angiographic stenosis) who underwent CMD evaluation as well as an electrocardiogram (ECG) up to 1-year prior. Endothelial-independent CMD was defined by coronary flow reserve (CFR) ≤2.5 in response to intracoronary adenosine. Endothelial-dependent CMD was defined by a maximal percent increase in coronary blood flow (%ΔCBF) ≤50% in response to intracoronary acetylcholine infusion. We trained algorithms to distinguish between the following outcomes: CFR ≤2.5, %ΔCBF ≤50, and the combination of both. Two classes of algorithms were trained, one depending on ECG waveforms as input, and another using tabular clinical data. Mean age was 51 ± 12 years and 66% were females (n = 1257). Area under the curve values ranged from 0.49 to 0.67 for all the outcomes. The best performance in our analysis was for the outcome CFR ≤2.5 with clinical variables. Area under the curve and accuracy were 0.67% and 60%. When decreasing the threshold of positivity, sensitivity and negative predictive value increased to 92% and 90%, respectively, while specificity and positive predictive value decreased to 25% and 29%, respectively.

Conclusion

An artificial intelligence-enabled algorithm may be able to assist clinical guidance by ruling out CMD in patients presenting with chest pain and/or an abnormal functional stress test. This algorithm needs to be prospectively validated in different cohorts.

Pathophysiology and Diagnosis of Coronary Functional Abnormalities

Approximately one-half of patients undergoing diagnostic coronary angiography for angina have no significant coronary atherosclerotic stenosis. This clinical condition has recently been described as ischaemia with non-obstructive coronary arteries (INOCA). Coronary functional abnormalities are central to the pathogenesis of INOCA, including epicardial coronary spasm and coronary microvascular dysfunction composed of a variable combination of increased vasoconstrictive reactivity and/or reduced vasodilator function. During the last decade - in INOCA patients in particular - evidence for the prognostic impact of coronary functional abnormalities has accumulated and various non-invasive and invasive diagnostic techniques have enabled the evaluation of coronary vasomotor function in a comprehensive manner. In this review, the authors briefly summarise the recent advances in the understanding of pathophysiology and diagnosis of epicardial coronary artery spasm and coronary microvascular dysfunction.

Prognostic impact and clinical outcomes of coronary flow reserve and hyperaemic microvascular resistance

BACKGROUND

Most studies dichotomise indices of coronary microvascular function to assess their prognostic values.

AIMS

We aimed to investigate whether coronary flow reserve (CFR) and hyperaemic microvascular resistance (HMR) as continua predict major adverse cardiovascular events (MACE), comprising all-cause death, myocardial infarction, revascularisation, and stroke in patients with ischaemia and non-obstructive coronary artery disease.

METHODS

A total of 610 patients were included and followed up over a median of 8.0 years (199 individual MACE in 174 patients).

RESULTS

Both CFR and HMR as continua predicted MACE with an odds ratio (OR) of 0.70 (per 1-unit increase, 95% confidence interval [CI]: 0.53, 0.92; p=0.01) and 1.63 (per 1 mmHg/cm/s, 95% CI: 1.20, 2.21; p=0.002), respectively. This relationship remained significant after adjustment for age and sex with an adjusted OR of 0.66 (per 1 unit increase, 95% CI: 0.49, 0.89; p=0.01) and 1.42 (per 1 mmHg/cm/s, 95% CI: 1.03, 1.94; p=0.03). HMR added prognostic value to CFR in predicting MACE (net reclassification index 0.17, 95% CI: 0.02, 0.31; p=0.03; integrated discrimination improvement 0.01, 95% CI: 0.0001, 0.02; p=0.046).

CONCLUSIONS

Both CFR and HMR as continuous variables predict future risk of MACE.

Peripheral microvascular dysfunction is associated with plaque progression and adverse long-term outcomes in heart transplant patients

Aims

Cardiac allograft vasculopathy (CAV) is the major cause of increased morbidity and mortality after heart transplantation. Peripheral endothelial dysfunction (PED) is associated with early atherosclerosis and future risk of major adverse cardiovascular events (MACE) in non‐heart transplant population. We aimed to investigate the association of PED with future MACE, and plaque progression assessed by intravascular ultrasound (IVUS) after heart transplantation.

Methods and results

We included 66 transplant patients who underwent serial IVUS surveillance for CAV and baseline assessment of peripheral endothelial function using reactive hyperaemia peripheral arterial tonometry. PED was defined as reactive hyperaemia index < 2. The primary endpoint of the study was to investigate the association of PED with CAV progression assessed by intravascular ultrasound (IVUS). CAV progression was assessed as the change (Δ) in plaque volume divided by segment length, and Δ plaque index (plaque volume/vessel volume), adjusted for the time between IVUS measurements (median 3.0 [2.2, 3.1] years). The secondary endpoint was to investigate the association between PED and future MACE, which was defined as any incident of revascularization, heart failure hospitalization, stroke, myocardial infarction, re‐transplantation, and death. Patients with PED (n = 27) had more yearly plaque progression (0.50 ± 0.66 vs. 0.15 ± 0.50 mm³/mm/year, P = 0.02) and a higher Δ plaque index (2.41 ± 2.53% vs. 0.69 ± 2.22%, P = 0.01). Patients with PED were more likely to experience MACE during a median follow‐up of 8.2 years (interquartile range [7.6, 8.4]), after adjustment for potential cofounders such as age, high‐density lipoprotein cholesterol levels, total rejection score, baseline International Society for Heart & Lung Transplantation CAV grade, and indication of transplantation. (hazard ratio 2.15, 95% confidence interval [1.09, 4.23], P = 0.03).

Conclusions

Peripheral endothelial dysfunction is associated with increased plaque progression and adverse long‐term cardiovascular outcomes in transplant patients. PED assessment might be a useful clinical tool for risk stratification after heart transplantation.

Prognostic Links Between OCT-Delineated Coronary Morphologies and Coronary Functional Abnormalities in Patients With INOCA

OBJECTIVES

Whether there are prognostic links between coronary morphologies and coronary functional abnormalities was examined in ischemia and nonobstructive coronary artery disease (INOCA) patients.

BACKGROUND

Although INOCA has attracted much attention, little is known about the prognostic impact of coronary morphologies in this disorder.

METHODS

A total of 329 consecutive INOCA patients were enrolled and underwent spasm provocation testing combined with lactate sampling for diagnosis of epicardial and microvascular spasm (MVS). On the basis of the functional tests, the patients were classified into 4 groups: a control group without epicardial spasm or MVS (n = 32), MVS alone (n = 51), diffuse spasm in ≥2 coronary segments (n = 204), and focal spasm in 1 segment (n = 42). In this population, optical coherence tomography imaging of the left anterior descending coronary artery was performed for evaluation of adventitial vasa vasorum (AVV) and intraplaque neovessels (IPN). Index of microcirculatory resistance was also measured.

RESULTS

MVS frequently coexisted with diffuse (70%) and focal spasm (68%) with a good correlation between AVV and index of microcirculatory resistance (R = 0.353; p = 0.022). For a median follow-up of 1,043 days, focal spasm showed the worst prognosis (log rank p = 0.005), for which IPN was a significant prognostic factor. By contrast, diffuse spasm showed the greatest AVV with an intermediate prognosis. The prognostic value of INOCA was significantly enhanced by adding AVV and IPN to the physiological indices (area under the curve = 0.88 vs. 0.76; p = 0.048).

CONCLUSIONS

These results provide the first evidence that there are important prognostic links between coronary morphologies (evaluated by optical coherence tomography) and coronary functional abnormalities in patients with INOCA, indicating the importance of both evaluations in this population.

Circulating Progenitor Cells Are Associated With Plaque Progression And Long-Term Outcomes In Heart Transplant Patients

AIMS

Circulating progenitor cells (CPCs) play a role in vascular repair and plaque stability, while osteocalcin (OC) expressing CPCs have been linked to unstable plaque and adverse cardiovascular outcomes. However, their role in cardiac allograft vasculopathy (CAV) has not been elucidated. This cohort study aimed to investigate the contribution of CPCs on CAV progression and cardiovascular events after heart transplantation.

METHODS AND RESULTS

A total of 80 heart transplant patients (mean age 55 ± 14 years, 72% male) undergoing annual intravascular ultrasound (IVUS) had fresh CPCs marked by CD34, CD133, and OC counted in peripheral blood using flow cytometry, on the same day as baseline IVUS. CAV progression was assessed by IVUS as the change (Δ) in plaque volume divided by segment length (PV/SL), adjusted for the time between IVUS measurements (median 3.0, interquartile range (IQR) [2.8, 3.1] years), and was defined as ΔPV/SL that is above the median ΔPV/SL of study population. Major adverse cardiac events (MACE) was defined as any incident of revascularization, myocardial infarction, heart failure admission, re-transplantation, stroke and death. Patients with higher CD34+CD133+ CPCs had a decreased risk of CAV progression (odds ratio 0.58, 95% confidence interval [CI] [0.37, 0.92], p = 0.01) and MACE (hazard ratio [HR] 0.79, 95% CI [0.66, 0.99], p = 0.05) during a median (IQR) follow up of 8.0 years (7.2, 8.3). Contrarily, higher OC+ cell counts were associated with an increased risk of MACE (HR 1.26, 95% CI [1.03, 1.57], p = 0.02).

CONCLUSIONS

Lower levels of CD34+CD133+ CPCs are associated with plaque progression and adverse long-term outcomes in patients who underwent allograft heart transplantation. In contrast, higher circulating OC+ levels are associated with adverse long term outcomes. Thus, CPCs might play a role in amelioration of transplant vasculopathy, while OC expression by these cells might play a role in progression.

TRANSLATIONAL PERSPECTIVE

The results of the current study suggest lower levels of circulating CD34+CD133+ cell levels are associated with cardiac allograft vasculopathy progression and future adverse cardiovascular events, while higher OC+ cell levels are associated with a greater risk of future cardiovascular events. Further studies confirming our findings might elucidate the role of circulating progenitor cells in the pathophysiology of CAV. Moreover, our findings might support the use of circulating progenitors as biomarkers, as well as the notion of cell therapy as potential treatment option for CAV, a disease with severe burden and limited treatment options.

Coronary Microvascular Dysfunction

[Figure: see text].

Role of Inflammation in Coronary Epicardial and Microvascular Dysfunction

There is accumulating evidence highlighting a close relationship between inflammation and coronary microvascular dysfunction (CMD) in various experimental and clinical settings, with major clinical implications. Chronic low-grade vascular inflammation plays important roles in the underlying mechanisms behind CMD, especially in patients with coronary artery disease, obesity, heart failure with preserved ejection fraction and chronic inflammatory rheumatoid diseases. The central mechanisms of coronary vasomotion abnormalities comprise enhanced coronary vasoconstrictor reactivity, reduced endothelium-dependent and -independent coronary vasodilator capacity and increased coronary microvascular resistance, where inflammatory mediators and responses are substantially involved. How to modulate CMD to improve clinical outcomes of patients with the disorder and whether CMD management by targeting inflammatory responses can benefit patients remain challenging questions in need of further research. This review provides a concise overview of the current knowledge of the involvement of inflammation in the pathophysiology and molecular mechanisms of CMD from bench to bedside.

Coronary Microvascular Endothelial Dysfunction in Patients With Angina and Nonobstructive Coronary Artery Disease Is Associated With Elevated Serum Homocysteine Levels

Background Elevated levels of serum homocysteine, via impaired nitric oxide production, and coronary microvascular dysfunction are associated with increased risk of major adverse cardiovascular events. However, whether serum homocysteine levels and coronary microvascular endothelial dysfunction (CMED) are linked remains unknown. Methods and Results This study included 1418 patients with chest pain or an abnormal functional stress test and with nonobstructive coronary artery disease (<40% angiographic stenosis), who underwent CMED evaluation with functional angiography and had serum homocysteine levels measured. Patients were classified as having normal microvascular function versus CMED. Patients in the CMED group (n=743; 52%) had higher mean age (52.1±12.2 versus 50.0±12.4 years; P<0.0001), higher body mass index (29.1 [25.0-32.8] versus 27.5 [24.2-32.4]; P=0.001), diabetes mellitus (12.5% versus 9.4%; P=0.03), and fewer women (63.5% versus 68.7%; P=0.04) compared with patients in the normal microvascular function group. However, they had lower rates of smoking history, and mildly lower low-density lipoprotein cholesterol levels. Serum homocysteine levels were significantly higher in patients with CMED, and the highest quartile of serum homocysteine level (>9 µmol/L) was an independent predictor of CMED (odds ratio, 1.34 [95% CI, 1.03-1.75]; P=0.03) after adjustment for age; sex; body mass index; chronic kidney disease (CKD); diabetes mellitus; smoking exposure; low-density lipoprotein cholesterol; high-density lipoprotein cholesterol and triglycerides; and aspirin, statin, and B vitamin use. Conclusions Patients with CMED have significantly higher levels of serum homocysteine. Elevated serum homocysteine levels were associated with a significantly increased odds of an invasive diagnosis of CMED. The current study supports a potential role for homocysteine for diagnosis and target treatment in the patients with early coronary atherosclerosis.