Coronary microvascular dysfunction: A review of recent progress and clinical implications

An updated review on therapeutic strategies in coronary microvascular dysfunction

Coronary microvascular dysfunction (CMD) is well-known cause of angina, yet treatment options remain limited. This systematic review and meta-analysis examines the current literature and provides a contemporary evaluation of treatments using a stringent definition for CMD with accurate methods of microvascular assessment in accordance with recent consensus guidelines. Methods and Results: A search strategy was conducted independently by two authors (CK and RR). Studies were required to be prospective trials in adult patients with documented CMD by IC doppler wire, thermodilution techniques, or perfusion imaging via PET/MRI. CMD was defined as either coronary flow reserve (CFR)/myocardial perfusion reserve (MPR) < 2.5, and/or index of microvascular resistance (IMR) > 25. Methodological quality of studies was assessed via the Cochrane Risk of Bias tool. The primary and secondary endpoints were change in CFR/MPR/IMR and change in Seattle Angina Questionnaire (SAQ) scores respectively. Two-sided p-values were used and considered significant if p < 0.05. A total of 11,360 records were identified, from which 14 were included in this review covering 9 different treatments. Two treatments (quinapril and ranolazine) showed significant improvement in both CFR and angina. Three ranolazine trials were pooled in meta-analysis. The standardised mean difference showed a weak positive effect (0.24) with wide intervals (-0.21 to 0.26) which was not statistically significant (p = 0.20). We subsequently reviewed all treatments as mentioned in recent European consensus statements. Conclusions: The overall quality of evidence surrounding treatments for CMD is of "low", with lack of robust data highlighting the dire need for higher quality trials in this area.

Microvascular dysfunction causing myocardial ischemia in obstructive hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is characterized by myocardial hypertrophy and can lead to significant complications including left ventricular outflow tract obstruction (LVOTO) and myocardial ischemia. Microvascular dysfunction (MVD) is a less recognized but crucial cause of myocardial ischemia in HCM, contributing to myocardial injury in the absence of obstructive coronary artery disease. We presented a case of a 48-year-old male with retrosternal chest tightness radiating to the left arm for 3 h. Electrocardiography revealed left ventricular (LV) hypertrophy with ST-segment depression and T wave inversion. High-sensitivity troponin T levels were elevated. Echocardiography showed marked LV wall thickness, predominantly at the basal septum, with systolic anterior motion of anterior mitral valve leaflet causing LVOTO. Adenosine stress cardiac magnetic resonance imaging demonstrated faint patchy scars in the hypertrophied ventricular septum and significant stress-induced perfusion defects beyond the area of myocardial scarring. Coronary angiography showed normal epicardial arteries, suggesting MVD as the underlying cause of ischemia. The patient was treated with nebivolol and verapamil, leading to symptom relief and a reduction in the pressure gradient of LVOTO at follow-up. This case highlights the role of MVD in causing myocardial ischemia in patients with HCM. Effective management of HCM with MVD includes pharmacological therapy to alleviate outflow obstruction and improve myocardial perfusion. Comprehensive diagnostic and treatment approaches are essential for optimizing outcomes in patients with this complex condition.

Advances in the diagnosis and management of post-percutaneous coronary intervention coronary microvascular dysfunction: Insights into pathophysiology and metabolic risk interactions

Percutaneous coronary intervention (PCI), as an essential treatment for coronary artery disease, has significantly improved the prognosis of patients with large coronary artery lesions. However, some patients continue to experience myocardial ischemic symptoms post-procedure, largely due to coronary microvascular dysfunction (CMD). The pathophysiological mechanisms of CMD are complex and involve endothelial dysfunction, microvascular remodeling, reperfusion injury, and metabolic abnormalities. Moreover, components of metabolic syndrome, including obesity, hyperglycemia, hypertension, and dyslipidemia, exacerbate the occurrence and progression of CMD through multiple pathways. This review systematically summarizes the latest research advancements in CMD after PCI, including its pathogenesis, diagnostic techniques, management strategies, and future research directions. For diagnosis, invasive techniques such as coronary flow reserve and the index of microcirculatory resistance, as well as non-invasive imaging modalities (positron emission tomography and cardiac magnetic resonance), provide tools for early CMD detection. In terms of management, a multi-level intervention strategy is emphasized, incorporating lifestyle modifications (diet, exercise, and weight control), pharmacotherapy (vasodilators, hypoglycemic agents, statins, and metabolic modulators), traditional Chinese medicine, and specialized treatments (enhanced external counterpulsation, metabolic surgery, and lipoprotein apheresis). However, challenges remain in CMD treatment, including limitations in diagnostic tools and the lack of personalized treatment strategies. Future research should focus on the complex interactions between CMD and metabolic risks, aiming to optimize diagnostic and therapeutic strategies to improve the long-term prognosis of patients post-PCI.

Microvascular Resistance Reserve and Prognosis After Heart Transplantation

BACKGROUND

Impaired microcirculatory function after heart transplantation is associated with increased risk for acute cellular rejection. Microvascular resistance reserve (MRR) is a novel index for assessing microcirculatory function, irrespective of epicardial coronary artery stenosis, but it has not been validated in transplanted hearts.

OBJECTIVES

The aim of this study was to investigate the prognostic impact of MRR in heart transplantation.

METHODS

The present study prospectively enrolled 154 heart transplant recipients who underwent scheduled coronary angiography and invasive coronary physiological assessment 1 month after transplantation. Coronary microcirculatory dysfunction was defined as MRR ≤3.0. Elevated microcirculatory resistance was defined as an index of microcirculatory resistance ≥15. The presence of epicardial coronary stenosis was assessed by fractional flow reserve. The primary outcome was a composite of death or biopsy-proven acute cellular rejection of grade ≥ 2R after transplantation.

RESULTS

Among the total patients, 22.1% (34 of 154) had impaired microcirculatory function (MRR ≤3.0), and 77.9% (122 of 154) had preserved microcirculatory function (MRR >3.0). During median follow-up of 730 days (Q1-Q3: 730-730 days), patients with MRR ≤3.0 showed increased risk for a composite of death or acute cellular rejection (adjusted HR: 5.31; 95% CI: 2.65-10.64; P < 0.001), acute cellular rejection (adjusted HR: 4.83; 95% CI: 2.20-10.60; P < 0.001), and death (adjusted HR: 5.19; 95% CI: 1.24-21.62; P = 0.024). MRR was significantly associated with increased risk for death or acute cellular rejection, regardless of epicardial coronary artery stenosis (HR adjusted for fractional flow reserve: 1.89 per 1-U decrease in MRR; 95% CI: 1.46-2.46; P < 0.001) or elevated microcirculatory resistance (HR adjusted for index of microcirculatory resistance: 1.90 per 1-U decrease in MRR; 95% CI: 1.43-2.52; P < 0.001).

CONCLUSIONS

Impaired microcirculatory function, determined by MRR early after heart transplantation, identified patients at high risk for death or acute cellular rejection, regardless of epicardial coronary artery stenosis or elevated microcirculatory resistance. (Physiologic Assessment of Microvascular Function in Heart Transplant Patients; NCT02798731).

Coronary Microvascular Dysfunction and Vasospastic Angina-Pathophysiology, Diagnosis and Management Strategies

Coronary artery disease is one of the leading public health problems in the world in terms of mortality and economic burden from the disease. Traditionally, the focus of research and clinical pathways leading to the diagnosis and treatment of coronary artery disease was on the more common variant of the disease resulting from atherosclerosis in the epicardial coronary arteries. However, coronary microvasculature, representing the vast majority of the total heart circulation, has the greatest influence on overall coronary resistance and, therefore, blood flow. Coronary microvascular dysfunction (CMD), characterized by structural or functional abnormalities in the microvasculature, significantly impacts myocardial perfusion. Endothelial dysfunction results in inadequate coronary dilation during exercise or spontaneous spasm in the microvasculature or epicardial arteries. A significant proportion of people presenting for coronary angiography in the context of angina have unobstructed epicardial coronary arteries yet are falsely reassured about the benign nature of their condition. Meanwhile, increasing evidence indicates that patients diagnosed with CMD as well as vasospastic angina (VSA) face an increased risk of Major Adverse Cardiovascular Events (MACEs), including death. The aim of this review is to outline the current practice with regard to invasive and non-invasive methods of CMD and VSA diagnosis and assess the evidence supporting the existing treatment strategies. These include endotype-specific pharmacological therapies, a holistic approach to lifestyle modifications and risk factor management and novel non-pharmacological therapies. Furthermore, the review highlights critical gaps in research and suggests potential areas for future investigation, to improve understanding and management of these conditions.

Heart failure and microvascular dysfunction: an in-depth review of mechanisms, diagnostic strategies, and innovative therapies

Microvascular dysfunction (MVD) is increasingly recognized as a critical contributor to the pathogenesis of heart failure (HF), particularly in heart failure with preserved ejection fraction (HFpEF) and heart failure with reduced ejection fraction (HFrEF). Coronary microvascular dysfunction (CMD) significantly impacts HFpEF by reducing coronary flow reserve and myocardial perfusion reserve, leading to adverse outcomes such as myocardial ischemia, diastolic dysfunction, and increased risk of major cardiovascular events, including atrial fibrillation. In HFrEF, microvascular impairment is linked to heightened oxidative stress, reduced nitric oxide production, and activation of the renin-angiotensin-aldosterone system, further driving disease progression and contributing to poor prognosis. Advancements in diagnostic techniques, such as positron emission tomography, cardiac magnetic resonance imaging, and biomarker analysis, improve our ability to assess CMD in heart failure patients, enabling earlier diagnosis and risk stratification. Emerging therapies, including sodium-glucose cotransporter-2 inhibitors, angiotensin receptor-neprilysin inhibitors, and endothelial-targeted interventions, enhance microvascular function and improve patient outcomes. The role of personalized medicine is becoming increasingly important, as individualized therapeutic approaches tailored to patient-specific microvascular abnormalities are essential for optimizing treatment effectiveness. This review underscores the pivotal role of MVD in HF. It highlights the urgent need for innovative therapeutic strategies and diagnostic tools to address this complex condition and improve clinical outcomes for HF patients.

Complete versus culprit-only percutaneous coronary intervention in elderly patients with acute coronary syndrome and multivessel coronary artery disease: A systematic review and meta-analysis

BACKGROUND

Culprit-only percutaneous coronary intervention (PCI) is commonly performed for acute coronary syndrome (ACS) with multivessel coronary artery disease (MVD) in the elderly. Complete revascularization has been shown to benefit the general population, yet its safety and efficacy in older patients are uncertain.

METHODS

Following PRISMA guidelines, we systematically searched PubMed, Embase, and Cochrane databases for randomized controlled trials (RCTs) comparing complete versus culprit-only PCI in patients ≥65 years old with ACS and MVD. The primary outcome was major adverse cardiovascular events (MACE). Secondary outcomes included myocardial infarction (MI), ischemia-driven revascularization (IDR), all-cause mortality, and cardiovascular mortality. Data were pooled using a random effects model with a restricted maximum likelihood estimator to generate risk ratios (RRs).

RESULTS

Five RCTs with 4105 patients aged ≥65 years were included. Compared with culprit-only PCI, complete revascularization reduced MI (RR 0.65; 95 % CI 0.49-0.85; p < 0.01). MACE (RR 0.75; 95 % CI 0.54-1.05; p = 0.09) and IDR (RR 0.41; 95 % CI 0.16-1.04; p = 0.06) were not significantly different between both strategies among those aged ≥65. However, there was a significant reduction in MI (RR 0.69; 95 % CI 0.49-0.96; p-value = 0.03), MACE (RR 0.78; 95 % CI 0.65-0.94; p < 0.01), and IDR (RR 0.60; 95 % CI 0.41-0.89; p < 0.01) in those aged ≥75.

CONCLUSIONS

In elderly patients aged ≥65 years with ACS and MVD, a strategy of complete revascularization by PCI reduces MI compared to culprit-only PCI with no significant difference in MACE and IDR. However, complete revascularization reduced MI, MACE, and IDR in those aged ≥75 years suggesting a possible benefit in this age group.

Test-retest reproducibility of absolute myocardial blood flow obtained using stress dynamic CT myocardial perfusion imaging

Background

Coronary artery disease (CAD) and coronary microvascular disease (CMD) are significant contributors to angina pectoris, necessitating reliable diagnostic techniques for effective management. While positron emission tomography has been the non-invasive gold standard for myocardial blood flow (MBF) quantification, stress dynamic CT myocardial perfusion imaging (CTMPI) has emerged as a promising alternative. This study aimed to evaluate the test-retest reproducibility of MBF measurements obtained using dynamic CTMPI.

Methods

The study retrospectively analyzed MBF values from two dynamic CTMPI examinations conducted in the same patient cohort (n = 30) to examine the consistency of MBF quantification and the ability to visually detect and grade abnormal perfusion suggesting ischemia between the tests. Global and remote MBF were defined as the mean MBF and the maximum MBF of all segments, respectively.

Results

MBF quantification revealed strong linear correlations between the tests (r = 0.89 for global MBF, r = 0.88 for remote MBF, and r = 0.82 for all segments), and intraclass correlation coefficients reflected high agreement between the tests (0.94 for global MBF, 0.93 for remote MBF, and 0.90 for all segments). Bland-Altman plots indicated a negligible mean difference with acceptable limits of agreements between the tests for global MBF, remote MBF, and all segments. Visual assessment of the CTMPI maps for abnormal perfusion suggesting ischemia yielded a good inter-test agreement with a weighted kappa value of 0.80.

Conclusion

Dynamic CTMPI can consistently reproduce absolute MBF values and reliably detect myocardial perfusion abnormalities, potentially making it a robust diagnostic tool for evaluating the presence and severity of CAD and CMD.

Mesenchymal precursor cells reduce mortality and major morbidity in ischaemic heart failure with inflammation: DREAM-HF

AIMS

Progressive heart failure with reduced ejection fraction (HFrEF) is adversely affected by alterations in the myocardial balance between bone marrow-derived pro-inflammatory cardiac macrophages and embryo-derived reparative cardiac resident macrophages. Mesenchymal precursor cells (MPCs) may restore this balance and improve clinical outcomes when inflammation is present. The purpose was to (i) identify risk factors for cardiovascular death (CVD) in control patients with HFrEF in the DREAM-HF trial, and (ii) determine if MPCs improve major clinical outcomes (CVD, myocardial infarction [MI], stroke) in high-risk patients with ischaemic HFrEF and inflammation.

METHODS AND RESULTS

Cause-specific regression analyses were used to identify CVD risk factors in DREAM-HF control patients. Aalen-Johansen cumulative incidence curves were used to examine CVD, 2-point major adverse cardiovascular events (MACE) (MI or stroke), and 3-point MACE (CVD or MI or stroke) by treatment group in ischaemic vs non-ischaemic HFrEF and in patients with or without baseline inflammation. In control DREAM-HF patients, factors portending the greatest risk for CVD were inflammation (baseline plasma high-sensitivity C-reactive protein ≥2 mg/L; p = 0.003) and ischaemic HFrEF aetiology (p = 0.097), with increased CVD risk of 61% and 38%, respectively. Over 30-month mean follow-up, MPCs reduced 2-point and 3-point MACE by 88% (p = 0.005) and 52% (p = 0.018), respectively, in patients with ischaemic HFrEF and inflammation compared to controls.

CONCLUSION

Ischaemic aetiology and inflammation were identified as major risk factors for MACE in control DREAM-HF patients. A single intramyocardial MPC administration produced the most significant, sustained reduction in 2-point and 3-point MACE in patients with ischaemic HFrEF and inflammation.

Association of Coronary Microvascular Rarefaction and Myocardial Fibrosis With Coronary Artery Disease

BACKGROUND

To evaluate, in a cohort study, whether coronary microvasculature and myocardial structure differ between people with and without coronary artery disease (CAD).

METHODS AND RESULTS

We performed histological analysis of left ventricle free wall obtained at autopsy from 25 men and 23 women with ≥1 coronary artery with ≥75% area stenosis, and 25 men and 25 women without (no or minimal) CAD, matched for sex and age, who died suddenly from noncardiac causes. Decedents with myocardial infarction or other cardiac abnormality were excluded. Decedents with and without CAD had similar height and weight. Heart weight of decedents with CAD was higher than that of decedents without CAD (mean, 391 versus 364 g; mean difference, 27 g [95% CI, 0.3-54.0], P=0.048). Decedents with CAD had lower arteriole density (mean, 1.4 per mm2 versus 1.8 per mm2; mean difference, -0.4 per mm2 [95% CI, -0.6 to -0.2], P=0.0001), lower capillary length density (mean, 3164 versus 3701 mm/mm3; mean difference, -537 [95% CI, -787 to -286], P<0.0001), and higher total myocardial fibrosis (mean, 7.5% versus 5.7%; mean difference, 1.7% [95% CI, 1.0-2.5], P<0.0001), than decedents without CAD.

CONCLUSIONS

CAD was associated with coronary microvascular rarefaction and increased myocardial fibrosis. The association of CAD with coronary microvascular rarefaction and increased myocardial fibrosis may contribute to the increased risks of death, myocardial infarction and heart failure that accompany CAD, and may attenuate the impact of percutaneous coronary intervention on cardiovascular risk in people with stable angina.

The association between trimethylamine N-oxide levels and coronary microvascular dysfunction and prognosis in patients with ST-elevation myocardial infarction

BACKGROUND AND AIMS

Coronary microvascular dysfunction (CMD) is common after ST-elevation myocardial infarction (STEMI), leading to adverse clinical outcomes. However, its diagnosis remains difficult, and mechanisms elusive. This study explores the role of Trimethylamine N-oxide (TMAO), a gut microbiota metabolite, as a potential biomarker for diagnosing CMD in STEMI patients.

METHODS

This prospective, observational study enrolled 210 STEMI patients with multivessel coronary artery disease who underwent primary percutaneous coronary intervention (PCI). TMAO levels were measured at baseline, 3 months, and 12 months post-PCI, whilst coronary physiology was assessed at 3 months. The primary endpoint was the incidence of CMD at 3 months, with the secondary endpoint being major adverse cardiovascular and cerebrovascular events (MACCE) at 12 months. An additional 59 consecutive patients were enrolled for validation.

RESULTS

TMAO levels varied from baseline to 3 months, then stabilised. The areas under the ROC curve for baseline TMAO and TMAO at 3-month were 0.55 (95 % CI 0.46-0.64; p = 0.426), and 0.80 (95 % CI 0.73-0.87; p < 0.001), respectively. The optimal cut-off for TMAO at 3-month to diagnose CMD was 3.91, with similar sensitivity and specificity in the derivation and validation cohort. The incidence of MACCE was higher in patients with TMAO≥3.91 (41.4 % vs 10.7 %; p < 0.001). The addition of 3-month TMAO improved the diagnostic performance of traditional risk factors.

CONCLUSION

TMAO is a robust biomarker for CMD and is significantly associated with the incidence of MACCE. TMAO has the potential in guiding clinical decision-making and suggests an interplay between gut microbiota and CMD.

Myocardial contrast echocardiography evaluation of coronary microvascular dysfunction to Predict MACEs in patients with heart failure with preserved ejection fraction follow-up

BACKGROUND

CMD refers to the abnormalities of the tiny arteries and capillaries within the coronary artery system, which result in restricted or abnormal blood flow. CMD is an important mechanism involved in ischemic heart disease and secondary heart failure. CMD can explain left ventricular dysfunction and poor prognosis.The European Association of Cardiovascular Imaging recommends the use of MCE for the assessment of myocardial perfusion. Myocardial contrast echocardiography (MCE) is used to evaluate the accuracy of Coronary microvascular dysfunction (CMD) for predicting major adverse cardiac events (MACEs) in patients with heart failure with preserved ejection fraction (HFpEF) at follow-up.

METHODS

The clinical data of 142 patients diagnosed with HFpEF in our hospital from January 2020 to January 2022 were retrospectively summarized and stratified into 77 cases (> 1) in the CMD group and 65 cases (= 1) in the non-CMD group based on the perfusion score index (PSI) of the 17 segments of the left ventricle examined by the admission MCE, and the perfusion parameters were measured at the same time, including the peak plateau intensity (A value), the curve slope of the curve rise (βvalue) and A × β values. At a median follow-up of 27 months till October 2023, MACEs were recorded mainly including heart failure exacerbation, revascularization, cardiac death, etc. RESULTS: Increasing age, hypertension, diabetes, and coronary artery disease in the CMD group resulted in decreased left ventricular ejection fraction (LVEF), increased plasma NT-B-type natriuretic peptide (BNP) and left ventricular global longitudinal strain (LVGLS), decreased A-values and A × β-values, and an increased incidence of MACEs (P < 0.05). Univariate and multivariate Cox regression analyses showed that LVGLS (HR = 1.714, 95% CI = 1.289-2.279, P < 0.001) and A × β values (HR = 0.636, 95% CI = 0.417 to 0.969, P = 0.035) were independent predictors of MACEs in patients with HFpEF. The receiver operating characteristic curve (ROC) showed that the area under the curve (AUC) of LVGLS combined with A × β value for diagnosis of MACEs was 0.861 (95% CI = 0.761 ~ 0.961, P < 0.001), which was significantly higher than that of LVGLS or A × β value (P < 0.05). The Kaplan-Meier survival curves showed that the cumulative survival rate in CMD group was significantly lower than non-CMD group (logrank χ2 = 6.626, P = 0.010), with the most significant difference at 20 months of follow-up.

CONCLUSION

MCE can evaluate CMD semi-quantitatively and quantitatively, LVGLS combined with A × β value has good performance in predicting the risk of developing MACEs in patients with HFpEF at 3 years of follow-up, and CMD can be used as an important non-invasive indicator for assessing clinical prognosis.

Comparison of Ticagrelor with Clopidogrel on Coronary Microvascular Dysfunction Following Acute Myocardial Infarction Using Angiography-Derived Index of Microcirculatory Resistance

PURPOSE

This research aimed to assess the impact of ticagrelor and clopidogrel on coronary microvascular dysfunction (CMD) and prognosis following acute myocardial infarction (AMI), using the angiography-derived index of microcirculatory resistance (angio-IMR) as a non-invasive assessment tool.

METHODS

In this retrospective study, angio-IMR was performed to evaluate CMD before and after dual antiplatelet therapy (DAPT) with either ticagrelor (90 mg twice daily, n = 184) or clopidogrel (75 mg once daily, n = 72). The primary endpoint is the improvement of CMD evaluated by angio-IMR (delta angio-IMR) following DAPT. Secondary endpoints included myocardial reinfarction and readmission for heart failure during 2-year follow-up.

RESULTS

Compared with clopidogrel, ticagrelor exhibited a significantly higher delta angio-IMR [- 3.09 (5.14) versus - 1.99 (1.91), P = 0.008], indicating a superior improvement of CMD with ticagrelor treatment. Multivariate Cox regression indicated that ticagrelor treatment was related to a reduced risk of readmission for heart failure [8 (4.3) versus 9 (12.5), adjusted HR = 0.329; 95% CI = 0.116-0.934; P = 0.018] and myocardial reinfarction [7 (3.8) versus 8 (11.1), adjusted HR = 0.349; 95% CI = 0.125-0.975; P = 0.026]. Furthermore, ticagrelor treatment serves as an independent predictor of readmission for heart failure (HR = 0.322; 95% CI = 0.110-0.943; P = 0.039).

CONCLUSION

The results of this study indicate a potential association between ticagrelor treatment and improved CMD, as well as a reduced risk of cardiovascular events, including myocardial reinfarction and readmission for heart failure in AMI patients. Further randomized controlled trials are necessary to confirm the potential benefits of ticagrelor on CMD and cardiovascular prognosis. This clinical trial was registered in www.

CLINICALTRIALS

gov (NCT05978726).

From chest pain to coronary functional testing: Clinical and economic impact of coronary microvascular dysfunction

BACKGROUND

Coronary functional testing to formally diagnose coronary microvascular dysfunction (CMD) reduces cardiovascular events and alleviates angina. This study aims to investigate the extensive and complex journey that patients with CMD undergo, from the onset of chest pain to eventual diagnosis.

METHODS

Data from the Coronary Microvascular Disease Registry (CMDR) were analyzed, including information on the date of first documentation of chest pain, number of non-invasive and invasive tests the patient underwent, emergency department visits, and hospitalizations. In addition, we estimated the total cost per patient. A total of 61 patients with CMD diagnosis were included in this analysis.

RESULTS

Most patients in our cohort were older than 50 years of age. The median time from initial chest pain symptoms to diagnosis was 0.62 (interquartile range [IQR]: 0.06-2.96) years. During this period, patients visited the emergency department a median of 1.0 (IQR: 0.0-2.0) times. Diagnostic tests included 3.0 (IQR: 2.0-6.0) electrocardiograms, 3.0 (IQR: 0.0-6.0) high-sensitivity troponin tests, and 1.0 (IQR: 1.0-2.0) echocardiograms. Prior to diagnosis of CMD, 13 (21.3 %) patients had left heart catheterization without coronary functional testing. Non-invasive testing for ischemia was conducted in 43 (70.5 %) patients. Alternative non-cardiac diagnoses were given to 11 (18.0 %) patients during the diagnostic process, with referrals made to gastroenterology for 16 (26.2 %) and pulmonology for 10 (16.4 %) patients. The cost was almost $2000/patient.

CONCLUSION

Timely identification of CMD offers promising opportunities for prompt symptom alleviation, accompanied by reduced visits to the emergency department, cardiovascular testing, invasive medical procedures, and consequently reduced healthcare expenses.

Coronary microvascular dysfunction in autoimmune rheumatic diseases: beyond coronary flow velocity reserve

Autoimmune rheumatic diseases (ARDs) are a heterogeneous group of disorders characterized by an inappropriate immune reactivity against different body tissues. Patients affected by ARDs present increased cardiovascular morbidity and mortality, which significantly impacts long-term prognosis. Endothelial dysfunction, inflammation, oxidative stress, and autoimmunity are strictly involved in atherosclerosis progression and coronary microvascular dysfunction (CMD), both of which contribute to increased cardiovascular risk. CMD represents the inability of the coronary microvasculature to respond with vasodilation to increased cardiac metabolic demands and can be assessed by non-invasive and invasive imaging tests. Coronary flow velocity reserve assessed by echocardiography has been demonstrated to accurately identify ARDs patients with CMD. However, stress cardiac magnetic resonance (CMR) accurately assesses myocardial ischemia, perfusion, and viability in ARDs patients. The myocardial perfusion reserve index (MPRI) is a robust semiquantitative imaging marker that represents the vasodilatory capacity of the coronary microcirculation in response to a vasodilator stress. In the absence of significant coronary stenosis, ARDs patients revealed a reduced MPRI in comparison with the general population, regardless of the presence of myocardial fibrosis. Identification of CMD in asymptomatic patients could be crucial to precociously start targeted medical therapy, avoiding major adverse cardiac events in this clinical setting. This review aims to summarize the current evidence regarding CMD in ARDs patients, focusing on the role of stress CMR and the promising myocardial perfusion analysis.

Navigating the Landscape of Coronary Microvascular Research: Trends, Triumphs, and Challenges Ahead

Coronary microvascular dysfunction (CMD) refers to structural and functional abnormalities of the microcirculation that impair myocardial perfusion. CMD plays a pivotal role in numerous cardiovascular diseases, including myocardial ischemia with non-obstructive coronary arteries, heart failure, and acute coronary syndromes. This review summarizes recent advances in CMD pathophysiology, assessment, and treatment strategies, as well as ongoing challenges and future research directions. Signaling pathways implicated in CMD pathogenesis include adenosine monophosphate-activated protein kinase/Krüppel-like factor 2/endothelial nitric oxide synthase (AMPK/KLF2/eNOS), nuclear factor erythroid 2-related factor 2/antioxidant response element (Nrf2/ARE), Angiotensin II (Ang II), endothelin-1 (ET-1), RhoA/Rho kinase, and insulin signaling. Dysregulation of these pathways leads to endothelial dysfunction, the hallmark of CMD. Treatment strategies aim to reduce myocardial oxygen demand, improve microcirculatory function, and restore endothelial homeostasis through mechanisms including vasodilation, anti-inflammation, and antioxidant effects. Traditional Chinese medicine (TCM) compounds exhibit therapeutic potential through multi-targeted actions. Small molecules and regenerative approaches offer precision therapies. However, challenges remain in translating findings to clinical practice and developing effective pharmacotherapies. Integration of engineering with medicine through microfabrication, tissue engineering and AI presents opportunities to advance the diagnosis, prediction, and treatment of CMD.

Evaluating Ischemic Heart Disease in Women: Focus on Angina With Nonobstructive Coronary Arteries (ANOCA)

Ischemic heart disease (IHD) is common in women, and cardiovascular disease is a leading cause of morbidity and mortality. While obstructive coronary artery disease is the most common form of IHD, millions of women suffer from angina with nonobstructive coronary arteries (ANOCA), an umbrella term encompassing multiple nonatherosclerotic disorders of the coronary tree. The underlying pathology leading to ischemia in these syndromes may be challenging to diagnose, leaving many women without a diagnosis despite persistent symptoms that impact quality of life and adversely affect long-term cardiovascular prognosis. In the last decade, there have been significant advances in the recognition and diagnostic evaluation of ANOCA. Despite these advances, the standard approach to evaluating suspected IHD in women continues to focus predominantly on the assessment of atherosclerotic coronary artery disease, leading to missed opportunities to accurately diagnose and treat underlying coronary vasomotor disorders. The goal of this review is to describe advances in diagnostic testing that can be used to evaluate angina in women and present a pragmatic diagnostic algorithm to guide evaluation of ANOCA in symptomatic patients. The proposed approach for the assessment of ANOCA is consistent with prior expert consensus documents and guidelines but is predicated on the medical interview and pretest probability of disease to inform a personalized diagnostic strategy.

Endothelial microRNAs in INOCA patients with diabetes mellitus

Ischemia with non-obstructive coronary artery (INOCA) is a common cause of hospital admissions, leading to negative outcomes and reduced quality of life. Central to its pathophysiology is endothelial dysfunction, which contributes to myocardial ischemia despite the absence of significant coronary artery blockage. Addressing endothelial dysfunction is essential in managing INOCA to alleviate symptoms and prevent cardiovascular events. Recent studies have identified diabetes mellitus (DM) as a significant factor exacerbating INOCA complications by promoting endothelial impairment and coronary microvascular dysfunction. MicroRNAs (miRNAs) have emerged as potential biomarkers and therapeutic targets in various biological processes, including endothelial dysfunction and cardiovascular diseases. However, research on miRNA biomarkers in INOCA patients is sparse. In this study, we examined a panel of circulating miRNAs involved in the regulation of endothelial function in INOCA patients with and without DM. We analyzed miRNA expression using RT-qPCR in a cohort of consecutive INOCA patients undergoing percutaneous coronary intervention. We detected a significant dysregulation of miR-363-5p and miR-92a-3p in INOCA patients with DM compared to those without DM, indicating their role as biomarkers for predicting and monitoring endothelial dysfunction in INOCA patients with DM.

Innervation of the coronary arteries and its role in controlling microvascular resistance

The coronary circulation plays a crucial role in balancing myocardial perfusion and oxygen demand to prevent myocardial ischemia. Extravascular compressive forces, coronary perfusion pressure, and microvascular resistance are involved to regulate coronary blood flow throughout the cardiac cycle. Autoregulation of the coronary blood flow through dynamic adjustment of microvascular resistance is maintained by complex interactions among mechanical, endothelial, metabolic, neural, and hormonal mechanisms. This review focuses on the neural mechanism. Anatomy and physiology of the coronary arterial innervation have been extensively investigated using animal models. However, findings in the animal heart have limited applicability to the human heart as cardiac innervation is generally highly variable among species. So far, limited data are available on the human coronary artery innervation, rendering multiple questions unresolved. Recently, the clinical entity of ischemia with non-obstructive coronary arteries has been proposed, characterized by microvascular dysfunction involving abnormal vasoconstriction and impaired vasodilation. Thus, measurement of microvascular resistance has become a standard diagnostic for patients without significant stenosis in the epicardial coronary arteries. Neural mechanism is likely to play a pivotal role, supported by the efficacy of cardiac sympathetic denervation to control symptoms in patients with angina. Therefore, understanding the coronary artery innervation and control of microvascular resistance of the human heart is increasingly important for cardiologists for diagnosis and to select appropriate therapeutic options. Advancement in this field can lead to innovations in diagnostic and therapeutic approaches for coronary artery diseases.

A Randomized Controlled Study of Enhanced External Counterpulsation with Cardiac Rehabilitation in Patients with Nonobstructive Coronary Artery Disease and Coronary Microvascular Dysfunction

Treatment with enhanced external counterpulsation (EECP) or cardiac rehabilitation (CR) benefits patients with coronary heart disease; this paper intends to explore the feasibility of EECP combined with CR in patients with nonobstructive coronary heart disease (NOCAD) and coronary microcirculation disorders (CMD).In January 2021-2022 month June our income NOCAD patients as the research object, the line of cardiac magnetic resonance (CMR), myocardial perfusion reserve (MPR) < 2.0 coronary microcirculation disorders (CMD, 80 cases). Random indicator method 80 CMD patients divided into two groups, 40 cases in each. Usual treatment group: conventional drugs and CR therapy. EECP treatment group: on the basis of standard treatment group, employ EECP therapy. Comparing the two groups before and after the treatment curative effect cardiac function index, endothelial unction index, adverse cardiovascular events, etc.After EECP treatment, the treatment group showed a higher effective rate compared to the usual treatment group (P < 0.05). EECP group curative effect, left ventricular ejection fraction,plasma NO and vascular endothelial growth factor levels higher than the usual group, the incidence of adverse cardiovascular events is lower than the usual group. The difference was statistically significant (P < 0.05).EECP combined with cardiac rehabilitation in patients with CMD symptoms has better effect and safety and provides reference for treatment of CMD patients.

Impact of Coronary Microvascular Dysfunction on Functional Left Ventricular Remodeling and Diastolic Dysfunction

BACKGROUND

Coronary microvascular dysfunction (CMD) is a common complication of ST-segment-elevation myocardial infarction (STEMI) and can lead to adverse cardiovascular events. Whether CMD after STEMI is associated with functional left ventricular remodeling (FLVR) and diastolic dysfunction, has not been investigated.

METHODS AND RESULTS

This is a nonrandomized, observational, prospective study of patients with STEMI with multivessel disease. Coronary flow reserve and index of microcirculatory resistance of the culprit vessel were measured at 3 months post-STEMI. CMD was defined as index of microcirculatory resistance ≥25 or coronary flow reserve <2.0 with a normal fractional flow reserve. We examined the association between CMD, LV diastolic dysfunction, FLVR, and major adverse cardiac events at 12-month follow-up. A total of 210 patients were enrolled; 59.5% were men, with a median age of 65 (interquartile range, 58-76) years. At 3-month follow-up, 57 patients (27.14%) exhibited CMD. After 12 months, when compared with patients without CMD, patients with CMD had poorer LV systolic function recovery (-10.00% versus 8.00%; P<0.001), higher prevalence of grade 2 LV diastolic dysfunction (73.08% versus 1.32%; P<0.001), higher prevalence of group 3 or 4 FLVR (11.32% versus 7.28% and 22.64% versus 1.99%, respectively; P<0.001), and higher incidence of major adverse cardiac events (50.9% versus 9.8%; P<0.001). Index of microcirculatory resistance was independently associated with LV diastolic dysfunction and adverse FLVR.

CONCLUSIONS

CMD is present in ≈1 of 4 patients with STEMI during follow-up. Patients with CMD have a higher prevalence of LV diastolic dysfunction, adverse FLVR, and major adverse cardiac events at 12 months compared with those without CMD.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique Identifier: NCT05406297.

Intracoronary electrocardiogram detects coronary microvascular dysfunction and ischemia in patients with no obstructive coronary arteries disease

BACKGROUND

Coronary microvascular dysfunction (CMD) is the leading cause of ischemia with no obstructive coronary arteries disease (INOCA) disease. Diagnosis of CMD relies on surrogate physiological indices without objective proof of ischemia.

OBJECTIVES

Intracoronary electrocardiogram (icECG) derived hyperemic indices may accurately and objectively detect CMD and reversible ischemia in related territory.

METHODS

INOCA patients with proven ischemia by myocardial perfusion scan (MPS) and completely normal coronary arteries underwent simultaneous intracoronary electrophysiological (icECG) and physiological (intracoronary Doppler) assessment in all 3 coronary arteries during rest and under adenosine induced hyperemia.

RESULTS

Sixty vessels in 21 patients were included in the final analysis. All patients had at least one vessel with abnormal CFR. 41 vessels had CMD (CFR < 2.5), of which 26 had increased microvascular resistance (structural CMD, HMR > 1.9 mmHg.cm-1.s) and 15 vessels had CMD (CFR < 2.5) with normal microvascular resistance (functional CMD, HMR <= 1.9 mmHg.cm-1.s). Only one-third of the patients (n = 7) had impaired CFR < 2.5 in all 3 epicardial arteries. Absolute ST shift between hyperemia and rest (∆ST) has shown the best diagnostic performance for ischemia (cut-off 0.10 mV, sensitivity: 95%, specificity: 72%, accuracy: 80%, AUC: 0.860) outperforming physiological indices (CFR: 0.623 and HMR: 0.653 DeLong's test P = .0002).

CONCLUSIONS

In INOCA patients, CMD involves coronary artery territories heterogeneously. icECG can accurately detect CMD causing perfusion abnormalities in patients with INOCA outperforming physiological CMD markers, by demonstrating actual ischemia instead of predicting the likelihood of inducible ischemia based on violated surrogate thresholds of blunted flow reserve or increased minimum microvascular resistance.

CONDENSED ABSTRACT

In 21 INOCA patients with coronary microvascular dysfunction (CMD) and myocardial perfusion scan proved ischemia, hyperemic indices of intracoronary electrocardiogram (icECG) have accurately detected vessel-specific CMD and resulting perfusion abnormalities & ischemia, outperforming invasive hemodynamic indices. Absolute ST shift between hyperemia and rest (∆ST) has shown the best classification performance for ischemia in no Obstructive Coronary Arteries (AUC: 0.860) outperforming Doppler derived CMD indices (CFR: 0.623 and HMR: 0.653 DeLong's test P = .0002).icECG can be used to diagnose CMD causing perfusion defects by demonstrating actual reversible ischemia at vessel-level during the initial CAG session, obviating the need for further costly ischemia tests.

CLINICALTRIALS

GOV: NCT05471739.

Chemokine Fractalkine and Non-Obstructive Coronary Artery Disease-Is There a Link?

Non-obstructive coronary artery disease (NO-CAD) constitutes a heterogeneous group of conditions collectively characterized by less than 50% narrowing in at least one major coronary artery with a fractional flow reserve (FFR) of ≤0.80 observed in coronary angiography. The pathogenesis and progression of NO-CAD are still not fully understood, however, inflammatory processes, particularly atherosclerosis and microvascular dysfunction are known to play a major role in it. Chemokine fractalkine (FKN/CX3CL1) is inherently linked to these processes. FKN/CX3CL1 functions predominantly as a chemoattractant for immune cells, facilitating their transmigration through the vessel wall and inhibiting their apoptosis. Its concentrations correlate positively with major cardiovascular risk factors. Moreover, promising preliminary results have shown that FKN/CX3CL1 receptor inhibitor (KAND567) administered in the population of patients with ST-elevation myocardial infarction (STEMI) undergoing percutaneous coronary intervention (PCI), inhibits the adverse reaction of the immune system that causes hyperinflammation. Whereas the link between FKN/CX3CL1 and NO-CAD appears evident, further studies are necessary to unveil this complex relationship. In this review, we critically overview the current data on FKN/CX3CL1 in the context of NO-CAD and present the novel clinical implications of the unique structure and function of FKN/CX3CL1 as a compound which distinctively contributes to the pathomechanism of this condition.

Optical Coherence Tomography Angiography Changes in Patients Diagnosed With Acute Coronary Syndrome: A Systematic Review and Meta-Analysis

We conducted a systematic review and meta-analysis to assess the association between optical coherence tomography angiography (OCTA) parameters and acute coronary syndrome (ACS). Two independent reviewers searched the electronic databases (MEDLINE (Medical Literature Analysis and Retrieval System Online), Scopus, Embase (Excerpta Medica Database), Cochrane Library, ClinicalTrials.gov, and World Health Organization International Clinical Trials Registry Platform) from inception until April 2023. According to the inclusion criteria of this review, eligible were observational studies, randomized control trials, and registry/database studies that included the eyes of adult ACS patients and assessed OCTA parameters within the macula. The pooled standardized mean differences (SMD) between patients diagnosed with ACS and healthy controls with a confidence interval (CI) of 95% were calculated using the Hartung-Knapp-Sidik-Jonkman random-effects method. The heterogeneity was assessed by I2 and the Cochran Q and a random effects model was applied. Seven studies were eligible and included in our systematic review (n = 898), of which three were included in the meta-analysis (n = 341). The pooled SMD in the superficial vascular plexus (SVP), deep vascular plexus (DVP), and foveal avascular zone (FAZ) were -0.46 (95% CI: -0.94 to 0.01, p = 0.05, I2 = 0%, three studies), -0.10 (95% CI: -3.20 to 3.00, p = 0.75, I2 = 67%, two studies), and 0.43 (95% CI: -1.22 to 2.09, p = 0.38, I2 = 92%, three studies), respectively. Our findings suggest that there are no differences in OCTA metrics between ACS patients and healthy individuals.

Microvascular Dysfunction in Obesity-Hypertension

PURPOSE OF REVIEW

This review aims to explore the role of microvascular dysfunction in obesity-hypertension, discuss the effects obesity has on renal microvasculature, review the current methods for assessing microvascular dysfunction and available therapeutic options, and identify critical areas for further research.

RECENT FINDINGS

There is a strong association between obesity and hypertension. However, the pathophysiology of obesity-hypertension is not clear. Microvascular dysfunction has been linked to hypertension and obesity and could be an important mediator of obesity-related hypertension. Newer therapies for hypertension and obesity could have ameliorating effects on microvascular dysfunction, including GLP-1 agonists and SGLT-2 inhibitors. There is still much progress to be made in our understanding of the complex interplay between obesity, hypertension, and microvascular dysfunction. Continued efforts to understand microvascular dysfunction and its role in obesity-hypertension are crucial to develop precision therapy to target obesity-hypertension.

Quantitative Perfusion Imaging with Total-Body PET

Recently, PET systems with a long axial field of view have become the current state of the art. Total-body PET scanners enable unique possibilities for scientific research and clinical diagnostics, but this new technology also raises numerous challenges. A key advantage of total-body imaging is that having all the organs in the field of view allows studying biologic interaction of all organs simultaneously. One of the new, promising imaging techniques is total-body quantitative perfusion imaging. Currently, 15O-labeled water provides a feasible option for quantitation of tissue perfusion at the total-body level. This review summarizes the status of the methodology and the analysis and provides examples of preliminary findings on applications of quantitative parametric perfusion images for research and clinical work. We also describe the opportunities and challenges arising from moving from single-organ studies to modeling of a multisystem approach with total-body PET, and we discuss future directions for total-body imaging.

Understanding Patient Characteristics and Coronary Microvasculature: Early Insights from the Coronary Microvascular Disease Registry

Coronary angiography has limitations in accurately assessing the coronary microcirculation. A new comprehensive invasive hemodynamic assessment method utilizing coronary flow reserve (CFR) and the index of microvascular resistance (IMR) offers improved diagnostic capabilities. This study aimed to present early real-world experience with invasive hemodynamic assessment of the coronary microvasculature in symptomatic patients with nonobstructive coronary artery disease (CAD) from the Coronary Microvascular Disease Registry, which is a prospective, multi-center registry that standardized the evaluation of patients with angina and nonobstructive CAD who underwent invasive hemodynamic assessment of the coronary microvasculature using the Coroventis CoroFlow Cardiovascular System. All patients underwent comprehensive invasive hemodynamic assessment. Analysis was performed on the first 154 patients enrolled in the Coronary Microvascular Disease Registry; their mean age was 62.4 years and 65.6% were female. A notable proportion of patients (31.8%) presented with a Canadian Cardiovascular Society Angina Score of 3 or 4. Coronary microvascular dysfunction was diagnosed in 39 of 154 patients (25.3%), with mean fractional flow reserve of 0.89 ± 0.43, mean resting full cycle ratio of 0.93 ± 0.08, mean CFR of 1.8 ± 0.9, and mean IMR of 36.26 ± 19.23. No in-hospital adverse events were reported in the patients. This study demonstrates the potential of invasive hemodynamic assessment using CFR and IMR to accurately evaluate the coronary microvasculature in patients with nonobstructive CAD. These findings have important implications for improving the diagnosis and management of coronary microvascular dysfunction, leading to more targeted and effective therapies for patients with microvascular angina.

Unveiling the Enigma: Exploring the Intricate Link Between Coronary Microvascular Dysfunction and Takotsubo Cardiomyopathy

This review article delves into the intricate and evolving relationship between coronary microvascular dysfunction (CMD) and takotsubo cardiomyopathy (TCM), two intriguing cardiovascular conditions increasingly recognised for their potential interplay. We examine their characteristics, shared pathophysiological mechanisms, diagnostic challenges, and management strategies. Emerging evidence suggests a link between microvascular dysfunction and the development of TCM, leading to a deeper exploration of their connection. Accurate diagnosis of both conditions becomes essential, as microvascular dysfunction may modify TCM outcomes. We underscore the significance of understanding this connection for improved patient care, emphasising the need for tailored interventions when CMD and TCM coexist. Collaborative research and heightened clinical awareness are advocated to advance our comprehension of this relationship. Through interdisciplinary efforts, we aim to refine diagnostic precision, develop targeted therapies, and enhance patient outcomes in cardiovascular medicine.

Coronary Microvascular Dysfunction: Features and Prognostic Value

(1) Background: The results of the international studies support the assumption that coronary microvascular dysfunction (CMD) occurs significantly more often than previously identified and is associated with adverse outcomes. However, there is a lack of the accurate comprehension of its pathophysiology. The objectives of this study were to evaluate the clinical and instrumental features of CMD and to assess its prognostic value during 12 months of follow-up period. (2) Methods: A total of 118 patients with non-obstructive coronary artery disease (CAD) and preserved LV ejection fraction (62 [59; 64]%) were enrolled in the study. Serum levels of biomarkers were analyzed by enzyme-linked immunoassay. CMD was defined as the reduced myocardial flow reserve (MFR) ≤ 2 obtained by dynamic CZT-SPECT. Two-dimensional transthoracic echocardiography with evaluation of LV diastolic dysfunction was performed baseline. (3) Results: Patients were divided into groups depending on the presence of CMD: CMD+ group (MFR ≤ 2; n = 45), and CMD- group (MFR > 2; n = 73). In CMD+ group, the severity of diastolic dysfunction, the levels of biomarkers of fibrosis and inflammation were higher than in CMD- group. Multivariate regression analysis showed that the presence of diastolic dysfunction (OR 3.27; 95% CI 2.26-5.64; p < 0.001), the hyperexpression of NT-proBNP ≥ 760.5 pg/mL (OR 1.67; 95% CI 1.12-4.15; p = 0.021) and soluble ST2 ≥ 31.4 ng/mL (OR 1.37; 95% 1.08-2.98; p = 0.015) were independent factors associated with CMD. Kaplan-Meier analysis showed that a rate of the adverse outcomes was significantly (p < 0.001) higher in patients with CMD (45.2%, n = 19) than in patients without it (8.6%, n = 6). (4) Conclusions: Our data suggest that the presence of CMD was associated with the severe diastolic dysfunction and hyperexpression of the biomarkers of fibrosis and inflammation. Patients with CMD had higher rate of the adverse outcomes than those without it.