International standardization of diagnostic criteria for microvascular angina

Coronary microvascular dysfunction and myocardial infarction with non-obstructive coronary arteries: Where do we stand?

In the past decade, scientific and clinical research has provided a translational perspective on myocardial infarction (MI) with non-obstructive coronary arteries (MINOCA). MINOCA is characterized by clinical documentation of an acute MI but angiography shows no significant coronary artery obstruction (stenosis <50%). The prevalence of MINOCA is estimated to range from approximately 6 to 10% among MI patients, and those with this condition have a poor prognosis, experiencing high rates of mortality, rehospitalization, and socioeconomic burden. MINOCA represents a major unmet need in cardiovascular medicine, with uncertain clinical management. It is a complex condition that can be caused by various factors, including atherosclerosis, plaque rupture, coronary vasospasm, and microvascular dysfunction. Effective management of MINOCA depends on identifying the underlying mechanism of the infarction, thus a systematic diagnostic approach is recommended. Contemporary data shows that a significant number of patients exhibit structural and functional abnormalities in coronary microcirculation, which is referred to as coronary microvascular dysfunction (CMD). CMD plays a crucial role in patients with signs and symptoms of myocardial ischemia and non-obstructive coronary artery stenosis, including MINOCA. Furthermore, conducting a thorough evaluation of coronary function can have significant prognostic and therapeutic implications, since personalized patient management strategies based on this assessment have been shown to improve symptoms and prognosis. Therefore, an accurate and timely diagnosis of CMD is essential for effective patient management, which can be achieved through various invasive and non-invasive methods. This review will discuss the pathophysiological understanding, current diagnostic techniques, and management strategies of patients with MINOCA and CMD.

Sex differences in diagnostic modalities of coronary artery disease: Evidence from coronary microcirculation

Although atherosclerosis is usually considered a disease of the large arteries, risk factors for atherosclerosis also trigger structural and functional abnormalities at a microvascular level. In cardiac disease, microvascular dysfunction is especially relevant in women, among whom the manifestation of ischemic disease due to impaired coronary microcirculation is more common than in men. This sex-specific clinical phenotype has important clinical implications and, given the higher pre-test probability of coronary microvascular dysfunction in females, different diagnostic modalities should be used in women compared to men. In this review, we summarize invasive and non-invasive diagnostic modalities to assess coronary microvascular function, ranging from catheter-based evaluation of endothelial function to Doppler echocardiography and positron emission tomography. Moreover, we discuss different clinical settings in which microvascular disease plays an important role, underlining the importance of choosing the right diagnostic modality depending on the sex of the patients.

Microvascular arterial disease of the brain and the heart: a shared pathogenesis

Microvascular arterial disease in the heart manifest as coronary microvascular dysfunction. This condition causes microvascular angina and is associated increased morbidity and mortality. Microvascular arterial disease in the brain is referred to as cerebrovascular small vessel disease. This is responsible for 45% of dementias and 25% of ischaemic strokes. The heart and brain share similar vascular anatomy and common pathogenic risk factors are associated with the development of both coronary microvascular dysfunction and cerebrovascular small vessel disease. Microvascular disease in the heart and brain also appear to share common multisystem pathophysiological mechanisms. Further studies on diagnostic approaches, epidemiology and development of disease-modifying therapy seem warranted.

#FullPhysiology: a systematic step-by-step guide to implement intracoronary physiology in daily practice

#FullPhysiology is a comprehensive and systematic approach to evaluate patients with suspected coronary disease using PressureWire technology (Abbott Vascular, Santa Clara, CA, USA). This advancement in technology enables the investigation of each component of the coronary circulation, including epicardial, microvascular, and vasomotor function, without significantly increasing procedural time or technical complexity. By identifying the predominant physiopathology responsible for myocardial ischemia, #FullPhysiology enhances precision medicine by providing accurate diagnosis and facilitating tailored interventional or medical treatments. This overview aims to provide insights into modern coronary physiology and describe a systematic approach to assess epicardial flow-limiting disease, longitudinal physiological vessel analysis, microvascular and vasomotor dysfunction, as well as post- percutaneous coronary intervention (PCI) physiological results.

Invasive Coronary Assessment in Myocardial Ischemia with No Obstructive Coronary Arteries

PURPOSE OF REVIEW

The purpose of this review is threefold: (i) to give an overview of well-established invasive methods for assessing patients with ischemia with no obstructive coronary arteries (INOCA) in the cardiac catheterization laboratory; (ii) to describe the prognostic and treatment implications based on these findings, and (iii) to discuss current knowledge gaps and future perspectives.

RECENT FINDINGS

Recent studies have demonstrated that invasive coronary function testing not only allows for risk stratification of patients with INOCA but also guides medical therapy with improvement in symptoms and quality of life. Based on these findings, invasive coronary function assessment is now a class 2a recommendation in the 2021 ACC/AHA chest pain guideline to improve the diagnosis of coronary microvascular dysfunction and to enhance risk stratification. Invasive functional testing for patients with INOCA is well established and easily performed in the catheterization laboratory. Comprehensive invasive assessment is a key to differentiating INOCA endotypes and optimizing both medical therapy and preventive strategies including lifestyle modification.

Molecular mechanisms of endothelial dysfunction in coronary microcirculation dysfunction

Coronary microvascular endothelial cells (CMECs) react to changes in coronary blood flow and myocardial metabolites and regulate coronary blood flow by balancing vasoconstrictors-such as endothelin-1-and the vessel dilators prostaglandin, nitric oxide, and endothelium-dependent hyperpolarizing factor. Coronary microvascular endothelial cell dysfunction is caused by several cardiovascular risk factors and chronic rheumatic diseases that impact CMEC blood flow regulation, resulting in coronary microcirculation dysfunction (CMD). The mechanisms of CMEC dysfunction are not fully understood. However, the following could be important mechanisms: the overexpression and activation of nicotinamide adenine dinucleotide phosphate oxidase (Nox), and mineralocorticoid receptors; the involvement of reactive oxygen species (ROS) caused by a decreased expression of sirtuins (SIRT3/SIRT1); forkhead box O3; and a decreased SKCA/IKCA expression in the endothelium-dependent hyperpolarizing factor electrical signal pathway. In addition, p66Shc is an adapter protein that promotes oxidative stress; although there are no studies on its involvement with cardiac microvessels, it is possible it plays an important role in CMD.

Pharmacotherapy in patients with vasomotor disorders

Background

Anginal symptoms in patients with non-obstructive coronary artery disease are frequently related to vasomotor disorders of the coronary circulation. Although frequently overlooked, a distinct diagnosis of different vasomotor disorders can be made by intracoronary function testing. Early detection and treatment seems beneficial, but little evidence is available for the medical treatment of these disorders. Nevertheless, there are several pharmacotherapeutic options available to treat these patients and improve quality of life.

Methods & findings

We performed an extensive yet non-systematic literature search to explore available pharmacotherapeutic strategies for addressing vasomotor disorders in individuals experiencing angina and non-obstructive coronary artery disease. This article presents a comprehensive overview of therapeutic possibilities for patients exhibiting abnormal vasoconstriction (such as spasm) and abnormal vasodilation (like coronary microvascular dysfunction).

Conclusion

Treatment of vasomotor disorders can be very challenging, but a general treatment algorithm based on the existing evidence and the best available current practice is feasible.

Cardiac allograft vasculopathy diagnosed by vasodilator myocardial contrast echocardiography perfusion imaging

Cardiac allograft vasculopathy (CAV) remains a common long-term complication of cardiac transplantation. While invasive coronary angiography is considered the gold standard, it is also invasive and lacks sensitivity to detect early, distal CAV. Although vasodilator stress myocardial contrast echocardiography perfusion imaging (MCE) is used in the detection of microvascular disease in non-transplant patients, there is little data guiding its use in transplant recipients. Herein is a case series of four heart transplant recipients that had vasodilator stress MCE performed in addition to invasive coronary angiography for CAV surveillance. MCE at rest and after regadenason was performed using a continuous infusion of lipid-shelled microbubbles. We describe a case of normal microvascular function, diffuse microvascular dysfunction, patchy sub-endocardial perfusion defects and a focal sub-endocardial perfusion defect. Cardiac allograft vasculopathy can be heralded by several different perfusion patterns on MCE in patients after orthotopic heart transplant. The varying prognoses and potential interventions for these different patterns require further investigation.

Diagnostic Puzzles and Cause-Targeted Treatment Strategies in Myocardial Infarction with Non-Obstructive Coronary Arteries: An Updated Review

Myocardial infarction with nonobstructive coronary arteries (MINOCA) is a distinct subtype of myocardial infarction (MI), occurring in about 8-10% of spontaneous MI cases referred for coronary angiography. Unlike MI with obstructive coronary artery disease, MINOCA's pathogenesis is more intricate and heterogeneous, involving mechanisms such as coronary thromboembolism, coronary vasospasm, microvascular dysfunction, dissection, or plaque rupture. Diagnosing MINOCA presents challenges and includes invasive and non-invasive strategies aiming to differentiate it from alternative diagnoses and confirm the criteria of elevated cardiac biomarkers, non-obstructive coronary arteries, and the absence of alternate explanations for the acute presentation. Tailored management strategies for MINOCA hinge on identifying the underlying cause of the infarction, necessitating systematic diagnostic approaches. Furthermore, determining the optimal post-MINOCA medication regimen remains uncertain. This review aims to comprehensively address the current state of knowledge, encompassing diagnostic and therapeutic approaches, in the context of MINOCA while also highlighting the evolving landscape and future directions for advancing our understanding and management of this intricate myocardial infarction subtype.

Comprehensive Management of ANOCA, Part 1-Definition, Patient Population, and Diagnosis: JACC State-of-the-Art Review

Angina with nonobstructive coronary arteries (ANOCA) is increasingly recognized and may affect nearly one-half of patients undergoing invasive coronary angiography for suspected ischemic heart disease. This working diagnosis encompasses coronary microvascular dysfunction, microvascular and epicardial spasm, myocardial bridging, and other occult coronary abnormalities. Patients with ANOCA often face a high burden of symptoms and may experience repeated presentations to multiple medical providers before receiving a diagnosis. Given the challenges of establishing a diagnosis, patients with ANOCA frequently experience invalidation and recidivism, possibly leading to anxiety and depression. Advances in scientific knowledge and diagnostic testing now allow for routine evaluation of ANOCA noninvasively and in the cardiac catheterization laboratory with coronary function testing (CFT). CFT includes diagnostic coronary angiography, assessment of coronary flow reserve and microcirculatory resistance, provocative testing for endothelial dysfunction and coronary vasospasm, and intravascular imaging for identification of myocardial bridging, with hemodynamic assessment as needed.

Comprehensive Management of ANOCA, Part 2-Program Development, Treatment, and Research Initiatives: JACC State-of-the-Art Review

Centers specializing in coronary function testing are critical to ensure a systematic approach to the diagnosis and treatment of angina with nonobstructive coronary arteries (ANOCA). Management leveraging lifestyle, pharmacology, and device-based therapeutic options for ANOCA can improve angina burden and quality of life in affected patients. Multidisciplinary care teams that can tailor and titrate therapies based on individual patient needs are critical to the success of comprehensive programs. As coronary function testing for ANOCA is more widely adopted, collaborative research initiatives will be fundamental to improve ANOCA care. These efforts will require standardized symptom assessments and data collection, which will propel future large-scale clinical trials.

Characterization and implications of intracoronary hemodynamic assessment during coronary spasm provocation testing

BACKGROUND

Current diagnostic criteria for coronary spasm are based on patient's symptoms, ECG shifts and epicardial vasoconstriction during acetylcholine (ACh) spasm testing.

AIMS

To assess the feasibility and diagnostic value of coronary blood flow (CBF) and resistance (CR) assessment as objective parameters during ACh testing.

METHODS

Eighty-nine patients who underwent intracoronary reactivity testing including ACh testing with synchronous Doppler wire-based measurements of CBF and CR were included. Coronary microvascular and epicardial spasm, respectively, were diagnosed based on COVADIS criteria.

RESULTS

Patients were 63 ± 13 years old, predominantly female (69%) and had preserved LV ejection fraction (64 ± 8%). Overall, assessment of CBF and CR during ACh testing revealed a decrease in CBF of 0.62 (0.17-1.53)-fold and an increase of CR of 1.45 [0.67-4.02]-fold in spasm patients compared to 2.08 (1.73-4.76) for CBF and 0.45 (0.44-0.63) for CR in patients without coronary spasm (both p < 0.01). Receiver operating characteristic revealed a high diagnostic ability of CBF and CR (AUC 0.86, p < 0.001, respectively) in identifying patients with coronary spasm. However, in 21% of patients with epicardial spasm and 42% of patients with microvascular spasm a paradoxical response was observed.

CONCLUSIONS

This study demonstrates feasibility and potential diagnostic value of intracoronary physiology assessments during ACh testing. We observed opposite responses of CBF and CR to ACh in patients with positive vs. negative spasm test. While a decrease in CBF and an increase in CR during ACh seem pathognomonic for spasm, some patients with coronary spasm demonstrate paradoxical ACh response demanding further scientific investigations.

The relationships between acetylcholine-induced chest pain, objective measures of coronary vascular function and symptom status

Background

Acetylcholine-induced chest pain is routinely measured during the assessment of microvascular function.

Aims

The aim was to determine the relationships between acetylcholine-induced chest pain and both symptom burden and objective measures of vascular function.

Methods

In patients with angina but no obstructive coronary artery disease, invasive studies determined the presence or absence of chest pain during both acetylcholine and adenosine infusion. Thermodilution-derived coronary blood flow (CBF) and index of microvascular resistance (IMR) was determined at rest and during both acetylcholine and adenosine infusion. Patients with epicardial spasm (>90%) were excluded; vasoconstriction between 20% and 90% was considered endothelial dysfunction.

Results

Eighty-seven patients met the inclusion criteria. Of these 52 patients (60%) experienced chest pain during acetylcholine while 35 (40%) did not. Those with acetylcholine-induced chest pain demonstrated: (1) Increased CBF at rest (1.6 ± 0.7 vs. 1.2 ± 0.4, p = 0.004) (2) Decreased IMR with acetylcholine (acetylcholine-IMR = 29.7 ± 16.3 vs. 40.4 ± 17.1, p = 0.004), (3) Equivalent IMR following adenosine (Adenosine-IMR: 21.1 ± 10.7 vs. 21.8 ± 8.2, p = 0.76), (4) Increased adenosine-induced chest pain (40/52 = 77% vs. 7/35 = 20%, p < 0.0001), (5) Increased chest pain during exercise testing (30/46 = 63% vs. 4/29 = 12%, p < 0.00001) with no differences in exercise duration or electrocardiographic changes, and (6) Increased prevalence of epicardial endothelial dysfunction (33/52 = 63% vs. 14/35 = 40%, p = 0.03).

Conclusions

After excluding epicardial spasm, acetylcholine-induced chest pain is associated with increased pain during exercise and adenosine infusion, increased coronary blood flow at rest, decreased microvascular resistance in response to acetylcholine and increased prevalence of epicardial endothelial dysfunction. These findings raise questions about the mechanisms underlying acetylcholine-induced chest pain.

Evaluation of Ischemia with No Obstructive Coronary Arteries (INOCA) and Contemporary Applications of Cardiac Magnetic Resonance (CMR)

Ischemia with no obstructive coronary arteries (INOCA) is a relatively newly discovered ischemic phenotype that affects patients similarly to obstructive coronary artery disease (CAD) but has a unique pathophysiology and epidemiology. Patients with INOCA present with ischemic signs and symptoms but no obstructive CAD seen on coronary CTA or invasive coronary angiography, which can assess epicardial vessels. The mechanisms of INOCA can be grouped into three endotypes: coronary microvascular dysfunction, epicardial coronary vasospasm, or a combination of both. Accurate and comprehensive assessment of both epicardial and microvascular disease in suspected cases of INOCA is crucial for providing targeted therapy and improving outcomes in this underrepresented population. This review aims to clarify the complex pathophysiology of INOCA, present an overview of invasive and non-invasive diagnostic methods, and examine contemporary approaches for coronary perfusion assessment using cardiac magnetic resonance (CMR). We also explore how recent advancements in quantitative CMR can potentially revolutionize the evaluation of suspected INOCA by offering a rapid, accurate, and non-invasive diagnostic approach, thereby reducing the alarming number of cases that go undetected.

2023 AHA/ACC/ACCP/ASPC/NLA/PCNA Guideline for the Management of Patients With Chronic Coronary Disease: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2023 AHA/ACC/ACCP/ASPC/NLA/PCNA Guideline for the Management of Patients With Chronic Coronary Disease" provides an update to and consolidates new evidence since the "2012 ACCF/AHA/ACP/AATS/PCNA/SCAI/STS Guideline for the Diagnosis and Management of Patients With Stable Ischemic Heart Disease" and the corresponding "2014 ACC/AHA/AATS/PCNA/SCAI/STS Focused Update of the Guideline for the Diagnosis and Management of Patients With Stable Ischemic Heart Disease."

METHODS

A comprehensive literature search was conducted from September 2021 to May 2022. Clinical studies, systematic reviews and meta-analyses, and other evidence conducted on human participants were identified that were published in English from MEDLINE (through PubMed), EMBASE, the Cochrane Library, Agency for Healthcare Research and Quality, and other selected databases relevant to this guideline.

STRUCTURE

This guideline provides an evidenced-based and patient-centered approach to management of patients with chronic coronary disease, considering social determinants of health and incorporating the principles of shared decision-making and team-based care. Relevant topics include general approaches to treatment decisions, guideline-directed management and therapy to reduce symptoms and future cardiovascular events, decision-making pertaining to revascularization in patients with chronic coronary disease, recommendations for management in special populations, patient follow-up and monitoring, evidence gaps, and areas in need of future research. Where applicable, and based on availability of cost-effectiveness data, cost-value recommendations are also provided for clinicians. Many recommendations from previously published guidelines have been updated with new evidence, and new recommendations have been created when supported by published data.

2023 AHA/ACC/ACCP/ASPC/NLA/PCNA Guideline for the Management of Patients With Chronic Coronary Disease: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2023 AHA/ACC/ACCP/ASPC/NLA/PCNA Guideline for the Management of Patients With Chronic Coronary Disease" provides an update to and consolidates new evidence since the "2012 ACCF/AHA/ACP/AATS/PCNA/SCAI/STS Guideline for the Diagnosis and Management of Patients With Stable Ischemic Heart Disease" and the corresponding "2014 ACC/AHA/AATS/PCNA/SCAI/STS Focused Update of the Guideline for the Diagnosis and Management of Patients With Stable Ischemic Heart Disease."

METHODS

A comprehensive literature search was conducted from September 2021 to May 2022. Clinical studies, systematic reviews and meta-analyses, and other evidence conducted on human participants were identified that were published in English from MEDLINE (through PubMed), EMBASE, the Cochrane Library, Agency for Healthcare Research and Quality, and other selected databases relevant to this guideline.

STRUCTURE

This guideline provides an evidenced-based and patient-centered approach to management of patients with chronic coronary disease, considering social determinants of health and incorporating the principles of shared decision-making and team-based care. Relevant topics include general approaches to treatment decisions, guideline-directed management and therapy to reduce symptoms and future cardiovascular events, decision-making pertaining to revascularization in patients with chronic coronary disease, recommendations for management in special populations, patient follow-up and monitoring, evidence gaps, and areas in need of future research. Where applicable, and based on availability of cost-effectiveness data, cost-value recommendations are also provided for clinicians. Many recommendations from previously published guidelines have been updated with new evidence, and new recommendations have been created when supported by published data.

The effect of ticagrelor on coronary microvascular function after PCI in patients with ACS compared to clopidogrel: A systematic review and meta-analysis

BACKGROUND

The function of coronary microcirculation is an important factor in predicting the prognosis of patients with acute coronary syndrome (ACS) who receive percutaneous coronary intervention (PCI) therapy. Ticagrelor, a type of oral P2Y12 inhibitor, is widely prescribed to ACS patients and can improve prognosis compared to clopidogrel. However, the efficacy of ticagrelor on coronary microcirculation, compared to clopidogrel, remains unclear. The objective of this meta-analysis was to determine the efficacy of ticagrelor on coronary microcirculation.

METHODS

The PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), and ClinicalTrials.gov databases were comprehensively searched to identify studies until November 2022. Data was pooled using the fixed effects model or random effects model based on the level of heterogeneity. Sensitivity analyses were performed to measure the effects of potential confounders.

RESULTS

After screening, 16 trials with a total of 3676 participants were ultimately included in the analysis. The meta-analysis revealed that compared to clopidogrel, patients receiving ticagrelor exhibited a more significant reduction in the IMR (WMD: -6.23, 95% CI: -8.41 to -4.04), a reduction in the cTFC (WMD: -1.88; 95% CI: -3.32 to -0.45), and greater increases in CFR (WMD: 0.38; 95% CI: 0.18 to 0.57), MBG (RR 1.29, 95% CI 1.12 to 1.48), and TIMI (RR 1.03, 95% CI 1.00 to 1.06).

CONCLUSION

Our findings suggest that, compared to clopidogrel, ticagrelor has a significant effect in reducing coronary microcirculatory resistance, enhancing coronary blood flow reserve, and improving myocardial perfusion.

Effects of remote ischemic preconditioning on coronary blood flow and microcirculation

This study aimed to determine the effect of short-term remote ischemic preconditioning (RIPC) on coronary blood flow and microcirculation function using the quantitative flow ratio (QFR) and index of microcirculatory resistance (IMR). We randomly divided 129 patients undergoing coronary angiography (CAG) into RIPC and control groups. Following the first CAG, we randomly divided the patients further into the unilateral upper limb and lower limb groups for four cycles of ischemia/reperfusion circulation; subsequently, we performed the second CAG. During each CAG, contrast-flow QFR (cQFR), fixed-flow QFR (fQFR), and IMR (in patients with cardiac syndrome X) were calculated and compared. We measured 253 coronary arteries in 129 patients. Compared to the control group, the average cQFR of the RIPC group increased significantly after RIPC. Additionally, 23 patients with cardiac syndrome X (IMR > 30) were included in this study. Compared to the control group, IMR and the difference between cQFR and fQFR (cQFR-fQFR) both decreased significantly after receiving RIPC. The application of RIPC can increase coronary blood flow and improve coronary microcirculation function.

Cardioprotective and Antianginal Efficacy of Nicorandil: A Comprehensive Review

ABSTRACT

Angina pectoris remains a significant burden despite advances in medical therapy and coronary revascularization. Many patients (up to 30%) with angina have normal coronary arteries, with coronary microvascular disease and/or coronary artery vasospasm being major drivers of the myocardial demand-supply mismatch. Even among patients revascularized for symptomatic epicardial coronary stenosis, recurrent angina remains highly prevalent. Medical therapy for angina currently centers around 2 disparate goals, viz secondary prevention of hard clinical outcomes and symptom control. Vasodilators, such as nitrates, have been first-line antianginal agents for decades, along with beta-blockers and calcium channel blockers. However, efficacy in symptoms control is heterogenous, depending on underlying mechanism(s) of angina in an individual patient, often necessitating multiple agents. Nicorandil (NCO) is an antianginal agent first discovered in the late 1970s with a uniquely dual mechanism of action. Like a typical nitrate, it mediates medium-large vessel vasodilation through nitric oxide. In addition, NCO has adenosine triphosphate (ATP)-dependent potassium channel agonist activity (K ATP ), mediating microvascular dilatation. Hence, it has proven effective in both coronary artery vasospasm and coronary microvascular disease, typically challenging patient populations. Moreover, emerging evidence suggests that cardiomyocyte protection against ischemia through ischemic preconditioning may be mediated through K ATP agonism. Finally, there is now fairly firm evidence in favor of NCO in terms of hard event reduction among patients with stable coronary artery disease, following myocardial infarction, and perhaps even among patients with congestive heart failure. This review aims to summarize the mechanism of action of NCO, its efficacy as an antianginal, and current evidence behind its impact on hard outcomes. Finally, we review other cardiac and emerging noncardiac indications for NCO use.

Echocardiographic assessment of primary microvascular angina and primary coronary microvascular dysfunction

There is an increasing interest in the role of echocardiography in the evaluation of primary microvascular angina, which is attributed to primary coronary microvascular dysfunction. Valid echocardiographic techniques are expected to facilitate the diagnosis and follow-up of these patients and would be valuable for research purposes and therapy evaluation. However, adequate echocardiographic data are lacking, and the interpretation of the limited available literature is hindered by the previous addition of microvascular angina under more inclusive entities, such as cardiac syndrome X. In experienced hands, the assessment of primary coronary microvascular dysfunction in patients with suspected primary microvascular angina, using multiple echocardiographic techniques is feasible, relatively inexpensive, and safe. Exclusion of obstructive epicardial coronary artery disease is, however, a prerequisite for diagnosis. Two-dimensional transthoracic echocardiography, routine stress echocardiography, and speckle-tracking echocardiography indirectly assess primary coronary microvascular dysfunction by evaluating potential impairment in myocardial function and lack diagnostic sensitivity and specificity. Conversely, certain echocardiographic techniques, including Doppler-derived coronary flow velocity reserve and myocardial contrast echocardiography, assess some coronary microvascular dysfunction parameters and have exhibited diagnostic and prognostic potentials. Doppler-derived coronary flow velocity reserve is the best studied and only guideline-approved echocardiographic technique for documenting coronary microvascular dysfunction in patients with suspected microvascular angina. Myocardial contrast echocardiography, by comparison, can detect heterogeneous and patchy myocardial involvement by coronary microvascular dysfunction, which is an advantage over the common practice of coronary flow velocity reserve assessment in a single vessel (commonly the left anterior descending artery) which only reflects regional microvascular function. However, there is no consensus regarding the diagnostic criteria, and expertise performing this technique is limited. Echocardiography remains underexplored and inadequately utilized in the setting of microvascular angina and coronary microvascular dysfunction. Appraisal of the current echocardiographic literature regarding coronary microvascular dysfunction and microvascular angina is important to stay current with the progress in its clinical recognition and create a basis for future research and technological advancements.

Efficacy and safety of the endothelin-1 receptor antagonist macitentan in epicardial and microvascular vasospasm; a proof-of-concept study

Background

Treatment of patients diagnosed with angina due to epicardial or microvascular coronary artery spasm (CAS) is challenging because patients often remain symptomatic despite conventional pharmacological therapy. In this prospective, randomized, double-blind, placebo-controlled, sequential cross-over proof-of-concept study, we compared the efficacy and safety of macitentan, a potent inhibitor of the endothelin-1 receptor, to placebo in symptomatic patients with CAS despite background pharmacological treatment.

Methods

Patients with CAS diagnosed by invasive spasm provocation testing with >3 anginal attacks per week despite pharmacological treatment were considered for participation. Participants received either 10 mg of macitentan or placebo daily for 28 days as add-on treatment. After a wash-out period patients were crossed over to the alternate treatment arm. The primary endpoint was the difference in anginal burden calculated as [1] the duration (in minutes) * severity (on a Visual Analogue Scale (VAS) pain scale 1-10); and [2] the frequency of angina attacks * severity during medication use compared to the run-in phase.

Results

28 patients of whom 22 females (79%) and a mean age of 55.3 ± 7.6 completed the entire study protocol (epicardial CAS n = 19 (68), microvascular CAS n = 9 (32)). Change in both indices of anginal burden were not different during treatment with add-on macitentan as compared to add-on placebo (duration*severity: -9 [-134 78] vs -45 [-353 11], p = 0.136 and frequency*severity: -1.7 [-5.8 1.2] vs -1.8 [-6.2 0.3], p = 0.767). The occurrence and nature of self-reported adverse events were closely similar between the treatment phase with macitentan and placebo.

Conclusion

In patients with angina due to epicardial or microvascular CAS despite background pharmacological treatment, 28 days of add-on treatment with the ET-1 receptor antagonist, macitentan 10 mg daily, did not reduce anginal burden compared to add-on treatment with placebo.Trial Registrationhttps://trialsearch.who.int/, Identifier: EUCTR2018-002623-42-NL. Registration date: 20 February 2019.

Role of nuclear cardiology in diagnosis and risk stratification of coronary microvascular disease

Coronary flow reserve (CFR) with positron emission tomography/computed tomography (PET/CT) has an important role in the diagnosis of coronary microvascular disease (CMD), aids risk stratification and may be useful in monitoring therapy. CMD contributes to symptoms and a worse prognosis in patients with coronary artery disease (CAD), nonischemic cardiomyopathies, and heart failure. CFR measurements may improve our understanding of the role of CMD in symptoms and prognosis in CAD and other cardiovascular diseases. The clinical presentation of CAD has changed. The prevalence of nonobstructive CAD has increased to about 50% of patients with angina undergoing angiography. Ischemia with nonobstructive arteries (INOCA) is recognized as an important cause of symptoms and has an adverse prognosis. Patients with INOCA may have ischemia due to CMD, epicardial vasospasm or diffuse nonobstructive CAD. Reduced CFR in patients with INOCA identifies a high-risk group that may benefit from management strategies specific for CMD. Although measurement of CFR by PET/CT has excellent accuracy and repeatability, use is limited by cost and availability. CFR measurement with single-photon emission tomography (SPECT) is feasible, validated, and would increase availability and use of CFR. Patients with CMD can be identified by reduced CFR and selected for specific therapies.

Coronary Microvascular Dysfunction: What Clinicians and Investigators Should Know

PURPOSE OF REVIEW

Abnormal structure and function of the coronary microvasculature have been implicated in the pathophysiology of multiple cardiovascular disease processes. This article reviews recent research progress related to coronary microvascular dysfunction (CMD) and salient clinical takeaways.

RECENT FINDINGS

CMD is prevalent in patients with signs and symptoms of ischemia and no obstructive epicardial coronary artery disease (INOCA), particularly in women. CMD is associated with adverse outcomes, including most frequently the development of heart failure with preserved ejection fraction. It is also associated with adverse outcomes in patient populations including hypertrophic cardiomyopathy, dilated cardiomyopathy, and acute coronary syndromes. In patients with INOCA, stratified medical therapy guided by invasive coronary function testing to define the subtype of CMD leads to improved symptoms. There are invasive and non-invasive methodologies to diagnose CMD that provide prognostic information and mechanistic information to direct treatment. Available treatments improve symptoms and myocardial blood flow; ongoing investigations aim to develop therapy to improve adverse outcomes related to CMD.

J wave dynamicity during coronary angiography and intracoronary acetylcholine administration

BACKGROUND

J-waves may be observed during coronary angiography (CAG) or intracoronary acetylcholine (ACh) administration, but their significance is unknown.

METHODS

Forty-nine patients, 59.1 ± 11.5 years old and 59% male, were studied on suspicion of vasospastic angina, and J wave dynamicity was compared between CAG and Ach administration.

RESULTS

Diagnostic (≥0.1 mV) or nondiagnostic (<0.1 mV) J waves in 9 and 3 patients, respectively, were augmented, and J waves were newly observed in 2 patients during CAG and Ach administration. Similar changes in the J-wave amplitude were observed: from 0.10 ± 0.09 mV to 0.20 ± 0.15 mV (p < .002) and from 0.10 ± 0.10 mV to 0.20 ± 0.16 mV (p < .001) during CAG and Ach administration, respectively. J waves were located in the inferior leads and changed only during the right coronary interventions. In the remaining 35 patients, J waves were absent before and during the coronary interventions. Augmentation of J waves was found when the RR interval was shortened in some patients. Injection of anoxic media into the coronary artery might induce a conduction delay from myocardial ischemia that manifests as augmentation or new occurrence of J waves.

CONCLUSIONS

Both CAG and intracoronary Ach administration affected J waves similarly in the same individuals. A myocardial ischemia-induced conduction delay may be responsible for the changes in J waves, but further studies are needed.

Coronary Vascular (DYS) Function and Invasive Physiology Assessment: Insights into Bolus and Continuous Thermodilution Methods

A considerable number of patients with angina or myocardial ischemia have no significant coronary artery disease on invasive angiography. In recent years, several steps towards a better comprehension of the pathophysiology of these conditions, angina or ischemia with non-obstructive coronary arteries (ANOCA/INOCA), have been made. Nevertheless, several gaps in knowledge still remain. This review is intended to provide a comprehensive overview of ANOCA and INOCA, with a particular focus on pathophysiology, recent diagnostic innovations, gaps in knowledge and treatment modalities.

Exploring the active ingredients and mechanism of Shenzhi Tongxin capsule against microvascular angina based on network pharmacology and molecular docking

BACKGROUND

Microvascular angina (MVA) substantially threatens human health, and the Shenzhi Tongxin (SZTX) capsule demonstrates a remarkable cardioprotective effect, making it a potential treatment option for MVA. However, the precise mechanism of action for this medication remains unclear. This study utilized network pharmacology and molecular docking technology to investigate the active components and potential mechanisms underlying the efficacy of the SZTX capsule in alleviating MVA.

METHODS

The main ingredients of the SZTX capsule, along with their targets proteins and potential disease targets associated with MVA, were extracted from public available databases. This study utilized the STRING database and Cytoscape 3.7.2 software to establish a protein-protein interaction network and determine key signaling pathway targets. Subsequently, the DAVID database was utilized to conduct Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes analyses on the intersection targets. To further investigate the molecular interactions, Autodock and PyMOL software were employed to perform molecular docking and visualize the resulting outcomes.

RESULTS

A total of 130 and 142 bioactive ingredients and intersection targets were identified respectively. Six core targets were obtained through protein-protein interaction network analysis. Gene Ontology enrichment analysis showed that 610 biological processes, 75 cellular components, and 92 molecular functions were involved. The results of Kyoto Encyclopedia of Genes and Genomes enrichment analyses indicated that SZTX capsule molecular mechanism in the treatment of MVA may be related to several pathways, including mitogen-activated protein kinases, PI3K-Akt, HIF-1, and others. The results of molecular docking showed that the 7 key active ingredients of SZTX capsule had good binding ability to 6 core proteins.

CONCLUSION

SZTX capsule potentially exerts its effects by targeting multiple signaling pathways, including the mitogen-activated protein kinases signaling pathway, PI3K-Akt signaling pathway, and HIF-1 signaling pathway. This multi-target approach enables SZTX capsule to inhibit inflammation, alleviate oxidative stress, regulate angiogenesis, and enhance endothelial function.

The Role of Non-Invasive Multimodality Imaging in Chronic Coronary Syndrome: Anatomical and Functional Pathways

Coronary artery disease (CAD) is one of the major causes of mortality and morbidity worldwide, with a high socioeconomic impact. Currently, various guidelines and recommendations have been published about chronic coronary syndromes (CCS). According to the recent European Society of Cardiology guidelines on chronic coronary syndrome, a multimodal imaging approach is strongly recommended in the evaluation of patients with suspected CAD. Today, in the current practice, non-invasive imaging methods can assess coronary anatomy through coronary computed tomography angiography (CCTA) and/or inducible myocardial ischemia through functional stress testing (stress echocardiography, cardiac magnetic resonance imaging, single photon emission computed tomography-SPECT, or positron emission tomography-PET). However, recent trials (ISCHEMIA and REVIVED) have cast doubt on the previous conception of the management of patients with CCS, and nowadays it is essential to understand the limitations and strengths of each imaging method and, specifically, when to choose a functional approach focused on the ischemia versus a coronary anatomy-based one. Finally, the concept of a pathophysiology-driven treatment of these patients emerged as an important goal of multimodal imaging, integrating 'anatomical' and 'functional' information. The present review aims to provide an overview of non-invasive imaging modalities for the comprehensive management of CCS patients.

Cardiac Imaging in Women with Ischemic Heart Disease

Cardiac diseases are the main cause of death for both sexes worldwide. Treatment varies widely according to the sex of a patient, as there are differences in physiopathology, epidemiology, clinical presentation and management. However, women have been largely excluded from research studies in this field. At present, differences are starting to be recognized and more attention is being paid to the identification of female-specific (or emergent) atherosclerotic risk factors. Diagnostic testing also merits attention because cardiac imaging offers important information to help diagnosis and guide cardiac disease management. In this sense, multimodal imaging should be used with the most cost-effective approach, integrating this information into the clinical sphere according to the pretest probability of the disease. In this review, we address sex-specific features of ischemic heart disease that should be considered in the clinical assessment of women, as well as the value of different imaging techniques (including technical and clinical aspects) for management of women with ischemic heart disease, and identify future areas of action concerning ischemic heart disease in women.

Invasive Evaluation for Coronary Vasospasm

Vasospastic angina (VSA) occurs at rest and on exertion, with transient electrocardiographic ischemic changes. VSA presents with spontaneous coronary artery spasm (CAS); it has been associated with stable angina, acute coronary syndromes, and sudden cardiac death. CAS can be identified in normal arteries or non-obstructive coronary atherosclerosis, but is also prevalent in patients with coronary artery disease. The diagnosis is made with invasive coronary reactivity testing with provocation using acetylcholine (Ach). Epicardial spasms can be visualized through coronary angiography as a reversible epicardial vessel narrowing, while the diagnosis of microvascular spasm can be made when angina symptoms and ECG changes happen following intracoronary Ach without epicardial spasm. Identification of CAS allows for risk stratification and specific therapies targeting endothelial dysfunction and paradoxical vascular smooth muscle cell constriction. Therapies include calcium channel blockers as monotherapy or in a combination of a dihydropyridine and non-dihydropyridine. Short-acting nitrates offer acute symptomatic relief but long-acting nitrates should be used sparingly. This current update on invasive evaluation of VSA discusses unified Ach protocols.

Coronary Spasm: Ethnic and Sex Differences

Coronary spasm (CS), which may occur at the epicardial (focal or diffuse spasm) and/or microvascular (microvascular spasm) level, is a well-established cause of myocardial ischaemia, in particular in patients with anginal chest pain despite unobstructed coronary arteries. The diagnosis of CS can be confirmed during coronary angiography by an additional provocation test with vasoactive substances such as acetylcholine. Due to partially inconsistent data from large clinical studies, especially between Asian and white CS patients, ethnic differences concerning the prevalence and angiographic patterns of CS seem to exist. Furthermore, several studies in patients with coronary vasomotor disorders pointed towards differences among male and female CS patients. This article gives an overview of ethnic- and sex-related differences in patients with CS.

Entropy-based reliable non-invasive detection of coronary microvascular dysfunction using machine learning algorithm

PURPOSE

Coronary microvascular dysfunction (CMD) is emerging as an important cause of myocardial ischemia, but there is a lack of a non-invasive method for reliable early detection of CMD.

AIM

To develop an electrocardiogram (ECG)-based machine learning algorithm for CMD detection that will lay the groundwork for patient-specific non-invasive early detection of CMD.

METHODS

Vectorcardiography (VCG) was calculated from each 10-second ECG of CMD patients and healthy controls. Sample entropy (SampEn), approximate entropy (ApEn), and complexity index (CI) derived from multiscale entropy were extracted from ST-T segments of each lead in ECGs and VCGs. The most effective entropy subset was determined using the sequential backward selection algorithm under the intra-patient and inter-patient schemes, separately. Then, the corresponding optimal model was selected from eight machine learning models for each entropy feature based on five-fold cross-validations. Finally, the classification performance of SampEn-based, ApEn-based, and CI-based models was comprehensively evaluated and tested on a testing dataset to investigate the best one under each scheme.

RESULTS

ApEn-based SVM model was validated as the optimal one under the intra-patient scheme, with all testing evaluation metrics over 0.8. Similarly, ApEn-based SVM model was selected as the best one under the intra-patient scheme, with major evaluation metrics over 0.8.

CONCLUSIONS

Entropies derived from ECGs and VCGs can effectively detect CMD under both intra-patient and inter-patient schemes. Our proposed models may provide the possibility of an ECG-based tool for non-invasive detection of CMD.

MINOCA and INOCA: Role in Heart Failure

PURPOSE OF REVIEW

Infarction (MINOCA) and ischaemia (INOCA) with non-obstructive coronary disease are recent non-conventional presentations of coronary syndromes that are increasingly recognised in the clinical arena, particularly with the availability of new cardiovascular imaging techniques. Both are related to heart failure (HF). MINOCA is not associated with benign outcomes, and HF is among the most prevalent events. Regarding INOCA, microvascular dysfunction has also been found to associate with HF, particularly with preserved ejection fraction (HFpEF).

RECENT FINDINGS

Regardless of the several aetiologies underlying HF in MINOCA, it is likely related to LV dysfunction, where secondary prevention is not yet clearly established. Regarding INOCA, coronary microvascular ischaemia has been associated to endothelial dysfunction leading ultimately to diastolic dysfunction and HFpEF. MINOCA and INOCA are clearly related to HF. In both, there is a lack of studies on the identification of the risk factors for HF, diagnostic workup and, importantly, the appropriate primary and secondary prevention strategies.

Evaluation of Outpatients in the Post-COVID-19 Period in Terms of Autonomic Dysfunction and Silent Ischemia

INTRODUCTION AND OBJECTIVE

In this context, the objective of this study is to evaluate the 24-hour ambulatory electrocardiography (ECG) recordings, autonomous function with heart rate variability (HRV), and silent ischemia (SI) attacks with ST depression burden (SDB) and ST depression time (SDT) of post-COVID-19 patients.  Materials and methods: The 24-hour ambulatory ECG recordings obtained >12 weeks after the diagnosis of COVID-19 were compared between 55 consecutive asymptomatic and 73 symptomatic post-COVID-19 patients who applied to the cardiology outpatient clinic with complaints of palpitation and chest pain in comparison with asymptomatic post-COVID-19 patients in Kars Harakani state hospital. SDB, SDT, and HRV parameters were analyzed. Patients who had been on medication that might affect HRV, had comorbidities that might have caused coronary ischemia, and were hospitalized with severe COVID-19 were excluded from the study.

RESULTS

There was no significant difference between symptomatic and asymptomatic post-COVID-19 patients in autonomic function. On the other hand, SDB and SDT parameters were significantly higher in symptomatic post-COVID-19 patients than in asymptomatic post-COVID-19 patients. Multivariate analysis indicated that creatine kinase-myoglobin binding (CK-MB) (OR:1.382, 95% CI:1.043-1.831; p=0.024) and HRV index (OR: 1.033, 95% CI:1.005-1.061; p=0.019) were found as independent predictors of palpitation and chest pain symptoms in post-COVID-19 patients.

CONCLUSION

The findings of this study revealed that parasympathetic overtone and increased HRV were significantly higher in symptomatic patients with a history of COVID-19 compared to asymptomatic patients with a history of COVID-19 in the post-COVID-19 period. Additionally, 24-hour ambulatory ECG recordings and ST depression analysis data indicated that patients who experienced chest pain in the post-COVID-19 period experienced silent ischemia (SI) attacks.

INOCA/ANOCA: Mechanisms and novel treatments

Angina or ischemia with no obstructive coronary disease (ANOCA/INOCA) is a common but under-treated condition due to poorly understood pathophysiologic mechanisms, limited diagnostic tools, and lack of proven targeted therapy. Coronary microvascular dysfunction (CMD) occurs when the microvasculature inadequately perfuses the myocardium under stress, or at rest in the case of microvascular spasm resulting in ANOCA/INOCA. Coronary functional angiography (CFA) measures endothelial independent microvascular dysfunction (coronary flow reduction <2.5) in response to adenosine and endothelial dependent microvascular dysfunction (lack of dilation and/or constriction) to acetylcholine testing as well as epicardial and microvascular spasm. Current treatment for coronary microvascular dysfunction is limited to renin-angiotensin system (RAS) inhibitors and statins as well as antianginal medications. Novel therapies targeting the underlying pathology are under development and include the coronary sinus reducer, CD34+ stem cell therapy, and novel pharmacologic agents such as sGC stimulators or endothelin-receptor blockers. We review the current understanding of pathophysiology, diagnostic tools, and novel therapies for coronary microvascular dysfunction in ANOCA/INOCA.

Coronary Microvascular Disease in Contemporary Clinical Practice

Coronary microvascular disease (CMD) causes myocardial ischemia in a variety of clinical scenarios. Clinical practice guidelines support routine testing for CMD in patients with ischemia with nonobstructive coronary artery disease. Invasive testing to identify CMD requires Doppler or thermodilution measures of flow to determine the coronary flow reserve and measures of microvascular resistance. Acetylcholine coronary reactivity testing identifies concomitant endothelial dysfunction, microvascular spasm, or epicardial coronary spasm. Comprehensive testing may improve symptoms, quality of life, and patient satisfaction by establishing a diagnosis and guiding-targeted medical therapy and lifestyle measures. Beyond ischemia with nonobstructive coronary artery disease, testing for CMD may play a role in patients with acute myocardial infarction, angina following coronary revascularization, heart failure with preserved ejection fraction, Takotsubo syndrome, and after heart transplantation. Additional education and provider awareness of CMD and its role in cardiovascular disease is needed to improve patient-centered outcomes of ischemic heart disease.

Contemporary Diagnosis and Management of Patients with MINOCA

PURPOSE OF REVIEW

Myocardial infarction with nonobstructive coronary arteries (MINOCA) is defined as acute myocardial infarction (MI) with angiographically no obstructive coronary artery disease or stenosis ≤ 50%. MINOCA is diagnostically challenging and complex, making it difficult to manage effectively. This condition accounts for 6-8% of all MI and poses an increased risk of morbidity and mortality after diagnosis. Prompt recognition and targeted management are essential to improve outcomes and our understanding of this condition, but this process is not yet standardized. This article offers a comprehensive review of MINOCA, delving deep into its unique clinical profile, invasive and noninvasive diagnostic strategies for evaluating MINOCA in light of the lack of widespread availability for comprehensive testing, and current evidence surrounding targeted therapies for patients with MINOCA.

RECENT FINDINGS

MINOCA is not uncommon and requires comprehensive assessment using various imaging modalities to evaluate it further. MINOCA is a heterogenous working diagnosis that requires thoughtful approach to diagnose the underlying disease responsible for MINOCA further.

PET-determined prevalence of coronary microvascular dysfunction and different types in a cardio-metabolic risk population

Background

The aim was to investigate the prevalence of "classical" (predominantly related to alterations in hyperemic MBFs) and "endogen" (predominantly related to alterations in resting MBF) normal coronary microvascular function (nCMF) or coronary microvascular dysfunction (CMD) in a clinical population without flow-limiting obstructive CAD.

Methods

We prospectively enrolled 239 symptomatic patients with normal pharmacologically-stress and rest myocardial perfusion on ¹³N-ammonia PET/CT. ¹³N-ammonia PET/CT concurrently assessed myocardial flow reserve (MFR = MBF stress/MBF rest). Normal nCMF was defined by a MFR of ≥ 2.0, while an abnormal MFR of < 2.0 signified CMD. In addition, patients were subgrouped into classical and endogen type of nCMF and CMD, respectively.

Results

In the whole study population, CMD was present in 54% (130/239). The classical type was more prevalent than the endogen type of CMD (65% vs 35%, p ≤ 0.008). The classical type of CMD was paralleled by a high prevalence of diabetes mellitus, metabolic syndrome, and obesity, while the endogen type of CMD was accompanied by a higher prevalence of arterial hypertension, obesity, and/or morbid obesity. Further, the classical type of nCMF was more frequently observed that the endogen type (74% vs. 26%, p ≤ 0.007). The endogen type of nCMF was related to lower heart rate and/or arterial blood pressures.

Conclusions

In this contemporary clinical study population, slightly more than half of symptomatic patients had CMD with predominance of the classical type. These observations emphasize the need for standardized reporting of CMD to gear individualized and/or intensified medical treatment to improve symptoms and/or clinical outcome in these patients.

MINOCA Associated with a Myocardial Bridge: Pathogenesis, Diagnosis and Treatment

Myocardial bridging (MB) is the most frequent congenital coronary anomaly characterized by a segment of an epicardial coronary artery that passes through the myocardium. MB is an important cause of myocardial ischemia and is also emerging as a possible cause of myocardial infarction with non-obstructed coronary arteries (MINOCA). There are multiple mechanisms underlying MINOCA in patients with MB (i.e., MB-mediated increased risk of epicardial or microvascular coronary spasm, atherosclerotic plaque disruption and spontaneous coronary artery dissection). The identification of the exact pathogenetic mechanism is crucial in order to establish a patient-tailored therapy. This review provides the most up-to-date evidence regarding the pathophysiology of MINOCA in patients with MB. Moreover, it focuses on the available diagnostic tools that could be implemented at the time of coronary angiography to achieve a pathophysiologic diagnosis. Finally, it focuses on the therapeutic implications associated with the different pathogenetic mechanisms of MINOCA in patients with MB.

Mechanisms of Coronary Artery Spasm

Recent clinical trials have highlighted that percutaneous coronary intervention in patients with stable angina provides limited additional benefits on top of optimal medical therapy. This has led to much more attention being paid to coronary vasomotion abnormalities regardless of obstructive or non-obstructive arterial segments. Coronary vasomotion is regulated by multiple mechanisms that include the endothelium, vascular smooth muscle cells (VSMCs), myocardial metabolic demand, autonomic nervous system and inflammation. Over the years, several animal models have been developed to explore the central mechanism of coronary artery spasm. This review summarises the landmark studies on the mechanisms of coronary vasospasm demonstrating the central role of Rho-kinase as a molecular switch of VSMC hypercontraction and the important role of coronary adventitial inflammation for Rho-kinase upregulation in VSMCs.

Myocardial Infarction with Non-Obstructive Coronary Arteries (MINOCA): Focus on Coronary Microvascular Dysfunction and Genetic Susceptibility

Among the most common causes of death worldwide, ischemic heart disease (IHD) is recognized to rank first. Even if atherosclerotic disease of the epicardial arteries is known as the leading cause of IHD, the presence of myocardial infarction with non-obstructive coronary artery disease (MINOCA) is increasingly recognized. Notwithstanding the increasing interest, MINOCA remains a puzzling clinical entity that can be classified by distinguishing different underlying mechanisms, which can be divided into atherosclerotic and non-atherosclerotic. In particular, coronary microvascular dysfunction (CMD), classifiable in non-atherosclerotic mechanisms, is a leading factor for the pathophysiology and prognosis of patients with MINOCA. Genetic susceptibility may have a role in primum movens in CMD. However, few results have been obtained for understanding the genetic mechanisms underlying CMD. Future studies are essential in order to find a deeper understanding of the role of multiple genetic variants in the genesis of microcirculation dysfunction. Progress in research would allow early identification of high-risk patients and the development of pharmacological, patient-tailored strategies. The aim of this review is to revise the pathophysiology and underlying mechanisms of MINOCA, focusing on CMD and actual knowledge about genetic predisposition to it.

Positron Emission Tomography in Heart Failure: From Pathophysiology to Clinical Application

Imaging modalities are increasingly being used to evaluate the underlying pathophysiology of heart failure. Positron emission tomography (PET) is a non-invasive imaging technique that uses radioactive tracers to visualize and measure biological processes in vivo. PET imaging of the heart uses different radiopharmaceuticals to provide information on myocardial metabolism, perfusion, inflammation, fibrosis, and sympathetic nervous system activity, which are all important contributors to the development and progression of heart failure. This narrative review provides an overview of the use of PET imaging in heart failure, highlighting the different PET tracers and modalities, and discussing fields of present and future clinical application.

Intermuscular Adiposity is Associated with Coronary Microvascular Dysfunction Independently of Body Mass Index and Modifies its Effect on Adverse Cardiovascular Outcomes

Background: Skeletal muscle (SM) fat infiltration, or intermuscular adipose tissue (IMAT), reflects muscle quality and is associated with inflammation, a key determinant in cardiometabolic disease. Coronary flow reserve (CFR), a marker of coronary microvascular dysfunction (CMD), is independently associated with BMI, inflammation and risk of heart failure, myocardial infarction and death. We sought to investigate the relationship between skeletal muscle quality, CMD and cardiovascular outcomes. Methods: Consecutive patients (N=669) undergoing evaluation for CAD with cardiac stress PET demonstrating normal perfusion and preserved left ventricular ejection fraction were followed over median 6 years for major adverse cardiovascular events (MACE), including death and hospitalization for myocardial infarction or heart failure. CFR was calculated as stress/rest myocardial blood flow and CMD defined as CFR<2. Subcutaneous adipose tissue (SAT), SM and IMAT areas (cm ² ) were obtained from simultaneous PET attenuation correction CTs using semi-automated segmentation at the twelfth thoracic vertebra (T12) level. Results: Median age was 63 years, 70% were female and 46% nonwhite. Nearly half of patients were obese (46%, BMI 30-61) and BMI correlated highly with SAT and IMAT (r=0.84 and 0.71, respectively, p<0.001) and moderately with SM (r=0.52, p<0.001). Decreased SM and increased IMAT, but not BMI or SAT, remained independently associated with decreased CFR (adjusted p=0.03 and p=0.04, respectively). In adjusted analyses, both lower CFR and higher IMAT were associated with increased MACE [HR 1.78 (1.23-2.58) per -1U CFR and 1.53 (1.30-1.80) per +10 cm ² IMAT, adjusted p=0.002 and p<0.0001, respectively], while higher SM and SAT were protective [HR 0.89 (0.81-0.97) per +10 cm ² SM and 0.94 (0.91-0.98) per +10 cm ² SAT, adjusted p=0.01 and 0.003, respectively]. Every 1% increase in fatty muscle fraction [IMAT/(SM+IMAT)] conferred an independent 2% increased odds of CMD [CFR<2, OR 1.02 (1.01-1.04), adjusted p=0.04] and a 7% increased risk of MACE [HR 1.07 (1.04-1.09), adjusted p<0.001]. There was a significant interaction between CFR and IMAT, not BMI, such that patients with both CMD and fatty muscle demonstrated highest MACE risk (adjusted p=0.02). Conclusion: Increased intermuscular fat is associated with CMD and adverse cardiovascular outcomes independently of BMI and conventional risk factors. The presence of CMD and skeletal muscle fat infiltration identified a novel at-risk cardiometabolic phenotype.

Assessment of hemodynamic indices of conjunctival microvascular function in patients with coronary microvascular dysfunction

OBJECTIVE

Coronary microvascular dysfunction (CMD) is a cause of ischaemia with non-obstructive coronary arteries (INOCA). It is notoriously underdiagnosed due to the need for invasive microvascular function testing. We hypothesized that systemic microvascular dysfunction could be demonstrated non-invasively in the microcirculation of the bulbar conjunctiva in patients with CMD.

METHODS

Patients undergoing coronary angiography for the investigation of chest pain or dyspnoea, with physiologically insignificant epicardial disease (fractional flow reserve ≥0.80) were recruited. All patients underwent invasive coronary microvascular function testing. We compared a cohort of patients with evidence of CMD (IMR ≥25 or CFR <2.0); to a group of controls (IMR <25 and CFR ≥2.0). Conjunctival imaging was performed using a previously validated combination of a smartphone and slit-lamp biomicroscope. This technique allows measurement of vessel diameter and other indices of microvascular function by tracking erythrocyte motion.

RESULTS

A total of 111 patients were included (43 CMD and 68 controls). There were no differences in baseline demographics, co-morbidities or epicardial coronary disease severity. The mean number of vessel segments analysed per patient was 21.0 ± 12.8 (3.2 ± 3.5 arterioles and 14.8 ± 10.8 venules). In the CMD cohort, significant reductions were observed in axial/cross-sectional velocity, blood flow, wall shear rate and stress.

CONCLUSION

The changes in microvascular function linked to CMD can be observed non-invasively in the bulbar conjunctiva. Conjunctival vascular imaging may have utility as a non-invasive tool to both diagnose CMD and augment conventional cardiovascular risk assessment.

Significance of coronary artery calcification for predicting major adverse cardiovascular events: results from the NADESICO study in Japan

BACKGROUND

We aimed to determine the usefulness and sex differences of assessment of coronary artery calcification (CAC) with cardiovascular risk factors and major adverse cardiovascular events (MACE) in Japanese patients.

METHODS

In a nationwide, multicenter, prospective cohort study, 1187 patients with suspected coronary artery disease who underwent coronary computed tomography were enrolled. MACE included cardiovascular death, myocardial infarction, stroke, revascularization, and hospitalization for unstable angina, heart failure, or aortic disease. The concordance (C)-statistics were used to assess the relationships among the Suita risk score, CAC score, and incident MACE, with emphasis on sex differences.

RESULTS

The final analysis included 982 patients (mean age, 64.7 ± 6.6 years; 53.9 % male patients). MACE developed in 65 male and 21 female patients during a median follow-up of 1480 days. The C-statistics calculated using Suita score for MACE were 0.650, 0.633, and 0.569 in overall, male, and female patients, respectively. In overall patients, the C-statistic significantly increased in combined models of Agatston CAC scores of ≥100, 200, 300, or 400 and the Suita score. In each sex, the C-statistics significantly increased in the model that added an Agatston CAC score of ≥100 and ≥ 200 (+0.049 and + 0.057) in male patients, and ≥ 400 (+0.119) in females, respectively.

CONCLUSIONS

Adding assessment of Agatston CAC scores to Suita score was useful to improve the predictive ability for future MACE in Japanese patients. Agatston CAC scores of ≥100 or 200 in male and ≥ 400 in female patients in addition to Suita score improved the MACE risk prediction.