Optimal Use of Vasodilators for Diagnosis of Microvascular Angina in the Cardiac Catheterization Laboratory

Examining the Disproportionate Burden of Microvascular Disease in Women

Purpose of Review

Microvascular dysfunction (MD) is a systemic condition implicated in a wide range of pathologies, including ischemic heart disease (IHD), stroke, chronic kidney disease (CKD), dementia, pulmonary arterial hypertension (PAH), and pregnancy complications. MD encompasses conditions characterized by small-vessel obstruction, impaired oxygen delivery, defective clearance of cellular waste, and inadequate gas exchange, ultimately leading to tissue damage and organ dysfunction. This review identifies the role of MD in the pathogenesis of a variety of diseases and across organ systems. It highlights the disproportionate burden of MD in women, with a focus on sex-specific risk factors, especially pregnancy.

Recent Findings

In recent years, there has been increased recognition of the role of MD in the pathogenesis of both cardiac and non-cardiac diseases. Advances in imaging modalities, such as coronary flow reserve assessment and endothelial function testing, have improved the detection of microvascular dysfunction across organ systems. Studies have also highlighted the connection between MD and systemic inflammation, oxidative stress, and hormonal influences, particularly in women. Emerging research suggests that pregnancy-related complications, including preeclampsia and gestational hypertension, may serve as early markers of long-term microvascular dysfunction and cardiovascular disease risk.

Summary

This review focuses on coronary microvascular dysfunction (CMD) in women, with additional discussion of endothelial and microvascular dysfunction in the renovascular, cerebrovascular, and pulmonary arterial systems. This review describes diagnostic and therapeutic approaches for MD in diverse disease contexts and emphasizes the critical need for research to advance diagnostic tools and therapeutic strategies tailored to the unique needs of women.

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.

Diagnostic Yield of Comprehensive Coronary Function Testing in Patients with Angina and Unobstructed Coronary Arteries: Endotype Characterisation and Clinical Implications

Background

Coronary functional disorders (CFD) are significant contributors to angina with non-obstructed coronary arteries (ANOCA). Various endotypes, such as epicardial or microvascular spasm and/or coronary microvascular dysfunction (CMD), have been identified. Previous studies have shown a high prevalence of CFD in ANOCA cases, but often lacked comprehensive coronary functional testing (CFT), which ideally includes coronary spasm provocation testing and CMD assessment. This study aims to investigate the prevalence of CFD and to characterise endotypes in ANOCA patients using comprehensive CFT.

Methods

A total of 89 consecutive ANOCA patients (mean age 64, 69% women) who underwent comprehensive CFT were enrolled. CFT comprised acetylcholine (ACh) spasm provocation testing and assessment of coronary flow reserve (CFR) and hyperaemic microvascular resistance using Doppler technique.

Results

CFT identified at least one coronary vasomotion disorder in 91% of patients with ANOCA. Among them, microvascular spasm was the most common endotype (61%), followed by CMD (43%). Only 9% of patients had isolated CMD with the remaining CMD patients also showing coronary spasm. Low CFR was mainly associated with high resting coronary flow rather than impaired hyperaemic flow (R -0.60, p<0.0001). Additionally, 48% of patients with microvascular spasm exhibited moderate to severe coronary tortuosity.

Conclusion

CFT provides a high diagnostic yield of CFD in ANOCA patients. Coronary spasm, particularly microvascular spasm, is the most frequent endotype. Patients with isolated CMD are rare, highlighting the importance of spasm testing in the ANOCA population.

Objective Ischemia, Subjective Angina, and Psychological Distress in Angina With No Obstructive Coronary Disease

BACKGROUND

Angina with no obstructive coronary disease (ANOCA) and ischemia with no obstructive coronary disease, prevalent yet underrecognized conditions, mostly affect women. Previous studies rarely distinguished between them. We aimed to compare the prevalence of objective ischemia through various examinations in women with ANOCA and assess the impact of objective and subjective ischemia on their mental health.

METHODS AND RESULTS

A total of 84 eligible women with ANOCA and 42 controls underwent mental stress, pharmacological stress, exercise stress, and Holter testing. Objective evidence of myocardial ischemia was assessed by positron emission tomography-computed tomography and ECG, and subjective symptoms were graded using the Canadian Cardiovascular Society scale (CCS). Psychological assessments were conducted using 6 scales. Among 84 women with ANOCA, 37 (44%) received a diagnosis of ischemia with no obstructive coronary disease following mental stress testing, 20 (28.6%) through pharmacological stress testing, 14 (21.2%) via exercise stress testing, and 24 (32.9%) from Holter. Mental stress-induced myocardial ischemia was more prevalent (P<0.05). Among 54 patients with ANOCA who completed all tests, 30% showed no ischemia, and only 1 (1.9%) showed ischemia in all tests. In addition, patients with ANOCA had higher psychological scores than controls (P<0.01). No significant differences was observed in psychological scores between ANOCA with positive and negative ischemia test results (P>0.05). However, ANOCA with milder angina (CCS I) exhibited higher scores across the Hospital Anxiety and Depression Scale, State-Trait Anxiety Inventory, Perceived Stress Scale, and Posttraumatic Stress Disorder Checklist-Civilian Version and a higher prevalence of Type D personality traits (P<0.05).

CONCLUSIONS

In patients with ANOCA, the positive rate of myocardial ischemia exhibits variability among several noninvasive tests. A worsened psychological state is more closely linked to milder angina symptoms than to ischemia performance, highlighting the importance of focusing on symptom management in their psychological care.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT03982901.

Coronary microvascular dysfunction, arrythmias, and sudden cardiac death: A literature review

The coronary vascular system has a unique structure and function that is adaptive to myocardial demand. It is composed of a continuous network of vessels receding in size from epicardial arteries to the microvascular circulation. Failure to meet myocardial demand results in ischemia, angina, and adverse myocardial outcomes. It is evident that 50 % of patients with angina have a non-obstructive coronary disease and 66 % of these patients have coronary microvascular dysfunction (CMD). The impact of CMD on the atria and ventricles is exhibited through its association with atrial fibrillation and distortion of ventricular repolarization. Ultimately, this influence increases the risk of mortality, morbidity, and sudden cardiac arrest. CMD serves as an independent risk for atrial fibrillation, increases ventricular electrical inhomogeneity, and contributes to the progression of cardiac disease. The underlying pathogenesis may be attributed to oxidative stress evident through reactive oxygen species, impaired vasoactive function, and structural disorders such as fibrotic changes. Myocardial ischemia, brought about by a demand-supply mismatch in CMD, may create a milieu for ventricular arrythmia and sudden cardiac arrest through distortion of ventricular repolarization parameters such as QT dispersion and corrected QT dispersion.

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.

Rethinking False Positive Exercise Electrocardiographic Stress Tests by Assessing Coronary Microvascular Function

BACKGROUND

Exercise electrocardiographic stress testing (EST) has historically been validated against the demonstration of obstructive coronary artery disease. However, myocardial ischemia can occur because of coronary microvascular dysfunction (CMD) in the absence of obstructive coronary artery disease.

OBJECTIVES

The aim of this study was to assess the specificity of EST to detect an ischemic substrate against the reference standard of coronary endothelium-independent and endothelium-dependent microvascular function in patients with angina with nonobstructive coronary arteries (ANOCA).

METHODS

Patients with ANOCA underwent invasive coronary physiological assessment using adenosine and acetylcholine. CMD was defined as impaired endothelium-independent and/or endothelium-dependent function. EST was performed using a standard Bruce treadmill protocol, with ischemia defined as the appearance of ≥0.1-mV ST-segment depression 80 ms from the J-point on electrocardiography. The study was powered to detect specificity of ≥91%.

RESULTS

A total of 102 patients were enrolled (65% women, mean age 60 ± 8 years). Thirty-two patients developed ischemia (ischemic group) during EST, whereas 70 patients did not (nonischemic group); both groups were phenotypically similar. Ischemia during EST was 100% specific for CMD. Acetylcholine flow reserve was the strongest predictor of ischemia during exercise. Using endothelium-independent and endothelium-dependent microvascular dysfunction as the reference standard, the false positive rate of EST dropped to 0%.

CONCLUSIONS

In patients with ANOCA, ischemia on EST was highly specific of an underlying ischemic substrate. These findings challenge the traditional belief that EST has a high false positive rate.

Characterizing Mechanisms of Ischemia in Patients With Myocardial Bridges

BACKGROUND

Myocardial bridges (MBs) are prevalent and can be associated with acute and chronic ischemic syndromes. We sought to determine the substrates for ischemia in patients with angina with nonobstructive coronary arteries and a MB in the left anterior descending artery.

METHODS

Patients with angina with nonobstructive coronary arteries underwent the acquisition of intracoronary pressure and flow during rest, supine bicycle exercise, and adenosine infusion. Coronary wave intensity analysis was performed, with perfusion efficiency defined as accelerating wave energy/total wave energy (%). Epicardial endothelial dysfunction was defined as a reduction in epicardial vessel diameter ≥20% in response to intracoronary acetylcholine infusion. Patients with angina with nonobstructive coronary arteries and a MB were compared with 2 angina with nonobstructive coronary arteries groups with no MB: 1 with coronary microvascular disease (CMD: coronary flow reserve, <2.5) and 1 with normal coronary flow reserve (reference: coronary flow reserve, ≥2.5).

RESULTS

Ninety-two patients were enrolled in the study (30 MB, 33 CMD, and 29 reference). Fractional flow reserve in these 3 groups was 0.86±0.05, 0.92±0.04, and 0.94±0.05; coronary flow reserve was 2.5±0.5, 2.0±0.3, and 3.2±0.6. Perfusion efficiency increased numerically during exercise in the reference group (65±9%-69±13%; P=0.063) but decreased in the CMD (68±10%-50±10%; P<0.001) and MB (66±9%-55±9%; P<0.001) groups. The reduction in perfusion efficiency had distinct causes: in CMD, this was driven by microcirculation-derived energy in early diastole, whereas in MB, this was driven by diminished accelerating wave energy, due to the upstream bridge, in early systole. Epicardial endothelial dysfunction was more common in the MB group (54% versus 29% reference and 38% CMD). Overall, 93% of patients with a MB had an identifiable ischemic substrate.

CONCLUSIONS

MBs led to impaired coronary perfusion efficiency during exercise, which was due to diminished accelerating wave energy in early systole compared with the reference group. Additionally, there was a high prevalence of endothelial and microvascular dysfunction. These ischemic mechanisms may represent distinct treatment targets.

Coronary microvascular dysfunction and heart failure with preserved ejection fraction: what are the mechanistic links?

PURPOSE OF REVIEW

Heart failure with preserved ejection fraction (HFpEF) accounts for half of all heart failure presentations and is associated with a dismal prognosis. HFpEF is an umbrella term that constitutes several distinct pathophysiological entities. Coronary microvascular dysfunction (CMD), defined as the inability of the coronary vasculature to augment blood flow adequately in the absence of epicardial coronary artery disease, is highly prevalent amongst the HFpEF population and likely represents one distinct HFpEF endotype, the CMD-HFpEF endotype. This review appraises recent studies that have demonstrated an association between CMD and HFpEF with an aim to understand the pathophysiological links between the two. This is of significant clinical relevance as better understanding of the pathophysiology underlying CMD-HFpEF may result in more targeted and efficacious therapeutic options in this patient cohort.

RECENT FINDINGS

There is a high prevalence of CMD, diagnosed invasively or noninvasively, in patients with HFpEF. Patients with HFpEF who have an impaired myocardial perfusion reserve (MPR) have a worse outcome than those with a normal MPR. Both MPR and coronary flow reserve (CFR) are associated with measures of left ventricular diastolic function and left ventricular filling pressures during exercise. Impaired lusitropy and subendocardial ischaemia link CMD and HFpEF mechanistically.

SUMMARY

CMD-HFpEF is a prevalent endotype of HFpEF and one that is associated with adverse cardiovascular prognosis. Whether CMD leads to HFpEF, through subendocardial ischaemia, or whether it is secondary to the impaired lusitropy that is characteristic of HFpEF is not known. Further mechanistic work is needed to answer this pertinent question.

Endothelial cell dysfunction in cardiac disease: driver or consequence?

The vascular endothelium is a multifunctional cellular system which directly influences blood components and cells within the vessel wall in a given tissue. Importantly, this cellular interface undergoes critical phenotypic changes in response to various biochemical and hemodynamic stimuli, driving several developmental and pathophysiological processes. Multiple studies have indicated a central role of the endothelium in the initiation, progression, and clinical outcomes of cardiac disease. In this review we synthesize the current understanding of endothelial function and dysfunction as mediators of the cardiomyocyte phenotype in the setting of distinct cardiac pathologies; outline existing in vivo and in vitro models where key features of endothelial cell dysfunction can be recapitulated; and discuss future directions for development of endothelium-targeted therapeutics for cardiac diseases with limited existing treatment options.

Higher Body Mass Index is associated with increased arterial stiffness prior to target organ damage: a cross-sectional cohort study

BACKGROUND

Obesity is associated with several neurohumoral changes that play an essential role in organ damage. Increased arterial stiffness causes functional vessel wall changes and can therefore lead to accelerated target organ damage as well. Whether obesity causes an independent increase in central arterial stiffness is, however, not yet fully known.

METHODS

One hundred thirty-three patients (63.2% male) were included. Body Mass Index (BMI) was defined as body weight in kilograms, divided by the square of body height in meters. Chronic Kidney Disease Epidemiology Collaboration creatinine 2009 equation was used to estimate the glomerular filtration rate (eGFR). Non-invasive applanation tonometry was used for arterial stiffness measurements (Sphygmocor Atcor Medical, Sydney, Australia). All patients underwent coronarography.

RESULTS

The mean age of our patients was 65.0 ± 9.2 years. Their mean BMI was 28.5 ± 4.4 kg/m2, eGFR 75.5 ± 17.2 ml/min/1.73 m2 and ankle-brachial index (ABI) 1.0 ± 0.1. Their arterial stiffness measurements showed mean carotid-femoral pulse wave velocity (cfPWV) 10.3 ± 2.7 m/s, subendocardial viability ratio (SEVR) 164.4 ± 35.0%, and pulse pressure (PP) 47.8 ± 14.5 mmHg. Spearman's correlation test revealed a statistically significant correlation between BMI and SEVR (r = -0.193; p = 0.026), BMI and cfPWV (r = 0.417; p < 0.001) and between BMI and PP (r = 0.227; p = 0.009). Multiple regression analysis confirmed an independent connection between BMI and cfPWV (B = 0.303; p < 0.001) and between BMI and SEVR (B = -0.186; p = 0.040). There was no association between BMI and kidney function, ABI, or coronary artery disease.

CONCLUSION

Increased BMI is independently associated with augmented central arterial stiffness and reduced subendocardial perfusion but not with coronary artery disease, kidney function, or ABI.

Initial single-center experience of a standardized protocol for invasive assessment of ischemia and no obstructive coronary artery disease

INTRODUCTION

Coronary vasomotion disorders (CVDs), including microvascular angina (MVA) and vasospastic angina (VSA), account for significant morbidity among patients with non-obstructive coronary artery disease (NOCAD). However, protocols for CVD assessment in clinical practice are seldom standardized and may be difficult to implement.

PURPOSE

To assess the safety and feasibility of a comprehensive coronary function test (CFT) protocol for assessment of CVD and the prevalence of different phenotypes of CVD in patients with angina and NOCAD (ANOCA).

METHODS

Patients with persistent angina referred for invasive coronary angiogram and found to have NOCAD were prospectively recruited and underwent a CFT. Functional parameters (fractional flow reserve, coronary flow reserve and index of myocardial resistance) and coronary vasoreactivity were assessed in all patients.

RESULTS

Of the 20 patients included, the mean age was 63±13 years and 50% were females. Most patients had persistent typical angina and evidence of ischemia in noninvasive tests (75%). The CFT was successfully performed in all subjects without serious complications. Isolated MVA was found in 25%, isolated VSA in 40%, both MVA and VSA in 10% and noncardiac chest pain in 25% of patients. Antianginal therapy was modified after the results of CFT in 70% of patients.

CONCLUSION

A coronary function test was feasible and safe in a cohort of patients with ANOCA. CVD were prevalent in this selected group of patients, and some presented mixed CVD phenotypes. CFT may provide a definitive diagnosis in patients with persistent angina and prompt the stratification of pharmacological therapy.

Complete Versus Incomplete Percutaneous Coronary Intervention-Mediated Revascularization in Patients With Chronic Coronary Syndromes

Multivessel coronary artery disease (CAD) is associated with worse outcomes across the spectrum of clinical presentations. The prognostic implications of completeness of revascularization in CAD patients, especially those with chronic coronary syndromes (CCS), remain highly debated. This is largely due to the use of non-standardized definitions for complete revascularization (CR) and incomplete revascularization (ICR) within previously published studies, lack of randomized clinical data, varying revascularization methods and heterogenous study populations. In particular, the utility and effectiveness of PCI-mediated CR for CCS remains unknown. In this review, we discuss the various definitions used for CR vs. ICR, highlight the rationale for pursuing CR and summarise the current literature regarding the effects of PCI-mediated CR on clinical outcomes in patients with CCS.

Coronary Slow Flow Is Not Diagnostic of Microvascular Dysfunction in Patients With Angina and Unobstructed Coronary Arteries

Background Guidelines recommend that coronary slow flow phenomenon (CSFP), defined as corrected thrombolysis in myocardial infarction frame count (CTFC) >$$ > $$27, can diagnose coronary microvascular dysfunction (CMD) in patients with angina and nonobstructed coronary arteries. CSFP has also historically been regarded as a sign of coronary endothelial dysfunction (CED). We sought to validate the utility of CTFC, as a binary classifier of CSFP and as a continuous variable, to diagnose CMD and CED. Methods and Results Patients with angina and nonobstructed coronary arteries had simultaneous coronary pressure and flow velocity measured using a dual sensor-tipped guidewire during rest, adenosine-mediated hyperemia, and intracoronary acetylcholine infusion. CMD was defined as the inability to augment coronary blood flow in response to adenosine (coronary flow reserve <2.5) and CED in response to acetylcholine (acetylcholine flow reserve ≤1.5); 152 patients underwent assessment using adenosine, of whom 82 underwent further acetylcholine testing. Forty-six patients (30%) had CSFP, associated with lower flow velocity and higher microvascular resistance as compared with controls (16.5±$$ \pm $$6.9 versus 20.2±$$ \pm $$6.9 cm/s; P=0.001 and 6.26±$$ \pm $$1.83 versus 5.36±$$ \pm $$1.83 mm Hg/cm/s; P=0.009, respectively). However, as a diagnostic test, CSFP had poor sensitivity and specificity for both CMD (26.7% and 65.2%) and CED (21.1% and 56.0%). Furthermore, on receiver operating characteristics analyses, CTFC could not predict CMD or CED (area under the curve, 0.41 [95% CI, 0.32%-0.50%] and 0.36 [95% CI, 0.23%-0.49%], respectively). Conclusions In patients with angina and nonobstructed coronary arteries, CSFP and CTFC are not diagnostic of CMD or CED. Guidelines supporting the use of CTFC in the diagnosis of CMD should be revisited.

Invasive coronary physiology in patients with angina and non-obstructive coronary artery disease: a consensus document from the coronary microvascular dysfunction workstream of the British Heart Foundation/National Institute for Health Research Partnership

Nearly half of all patients with angina have non-obstructive coronary artery disease (ANOCA); this is an umbrella term comprising heterogeneous vascular disorders, each with disparate pathophysiology and prognosis. Approximately two-thirds of patients with ANOCA have coronary microvascular disease (CMD). CMD can be secondary to architectural changes within the microcirculation or secondary to vasomotor dysfunction. An inability of the coronary vasculature to augment blood flow in response to heightened myocardial demand is defined as an impaired coronary flow reserve (CFR), which can be measured non-invasively, using imaging, or invasively during cardiac catheterisation. Impaired CFR is associated with myocardial ischaemia and adverse cardiovascular outcomes.The CMD workstream is part of the cardiovascular partnership between the British Heart Foundation and The National Institute for Health Research in the UK and comprises specialist cardiac centres with expertise in coronary physiology assessment. This document outlines the two main modalities (thermodilution and Doppler techniques) for estimation of coronary flow, vasomotor testing using acetylcholine, and outlines a standard operating procedure that could be considered for adoption by national networks. Accurate and timely disease characterisation of patients with ANOCA will enable clinicians to tailor therapy according to their patients' coronary physiology. This has been shown to improve patients' quality of life and may lead to improved cardiovascular outcomes in the long term.

Global trends and frontiers in research on coronary microvascular dysfunction: a bibliometric analysis from 2002 to 2022

BACKGROUND

Coronary microvascular dysfunction (CMD) is a leading cause of ischemic heart disease. Over the past few decades, considerable progress has been made with respect to research on CMD. The present study summarized the current research hotspots and trends on CMD by applying a bibliometric approach.

METHODS

Relevant publications between 2002 and 2022 were extracted from the Web of Science Core Collection. Visualization network maps of countries, institutions, authors, and co-cited authors were built using VOSviewer. CiteSpace was used for keyword analysis and the construction of a dual-map overlay of journals and a timeline view of co-cited references.

RESULTS

1539 CMD-related publications were extracted for bibliometric analysis. The annual publications generally showed an upward trend. The United States of America was the most prolific country, with 515 publications (33.5%). Camici P. G. was the most influential author, whereas the European Heart Journal, Circulation, and Journal of the American College of Cardiology were the most authoritative journals. Research hotspot analysis revealed that endothelial dysfunction as well as reduced nitric oxide production or bioavailability played critical roles in CMD development. Positron emission tomography was the most widely used imaging method for diagnosis. In addition, microvascular angina, hypertrophic cardiomyopathy, and heart failure have attracted much attention as the main clinical implications. Furthermore, international standards for CMD diagnosis and management may be the future research directions.

CONCLUSIONS

This study offers a comprehensive view about the hotspots and development trends of CMD, which can assist subsequent researchers and guide future directions.

Invasive Functional Coronary Assessment in Myocardial Ischemia with Non-Obstructive Coronary Arteries: from Pathophysiological Mechanisms to Clinical Implications

Despite ischemic heart disease (IHD) has been commonly identified as the consequence of obstructive coronary artery disease (OCAD), a significant percentage of patients undergoing coronary angiography because of signs and/or symptoms of myocardial ischemia do not have any significant coronary artery stenosis. Several mechanisms other than coronary atherosclerosis, including coronary microvascular dysfunction (CMD), coronary endothelial dysfunction and epicardial coronary vasospasm, can determine myocardial ischemia or even myocardial infarction in the absence of flow-limiting epicardial coronary stenosis, highlighting the need of performing adjunctive diagnostic tests at the time of coronary angiography to achieve a correct diagnosis. This review provides updated evidence of the pathophysiologic mechanisms of myocardial ischemia with non-obstructive coronary arteries, focusing on the diagnostic and therapeutic implications of performing a comprehensive invasive functional evaluation consisting of the assessment of both vasodilation and vasoconstriction disorders. Moreover, performing a comprehensive invasive functional assessment may have important prognostic and therapeutic implications both in patients presenting with myocardial ischemia with non-obstructive coronary arteries (INOCA) or myocardial infarction with non-obstructive coronary arteries (MINOCA), as the implementation of a tailored patient management demonstrated to improve patient's symptoms and prognosis. However, given the limited knowledge of myocardial ischaemia with non-obstructive coronary arteries, there are no specific therapeutic interventions for these patients, and further research is warranted aiming to elucidate the underlying mechanisms and risk factors and to develop personalized forms of treatment.

Invasive evaluation of coronary microvascular dysfunction

Coronary microvascular dysfunction (CMD) is a prevalent cause of ischemic heart disease and is associated with poorer quality of life and worse patient outcomes. Both functional and structural abnormalities of the microcirculation can generate ischemia in the absence of epicardial stenosis or worsen concomitant obstructive coronary artery disease (CAD). The invasive assessment of CMD allows for the evaluation of the entirety of the coronary vascular tree, from the large epicardial vessels to the microcirculation, and enables the study of vasomotor function through vasoreactivity testing. The standard evaluation of CMD includes vasomotor assessment with acetylcholine, as well as flow- and resistance-derived indices calculated with either thermodilution or Doppler guidewires. Tailored treatment based upon the information gathered from the invasive evaluation of CMD has been demonstrated to reduce the burden of angina; therefore, a thorough understanding of these procedures is warranted with the aim of improving the quality of life of the patient. This review summarizes the most widespread approaches for the invasive evaluation of CMD, with a focus on patients with ischemia and non-obstructive CAD.

Presence of Coronary Endothelial Dysfunction, Coronary Vasospasm, and Adenosine-Mediated Vasodilatory Disorders in Patients With Ischemia and Nonobstructive Coronary Arteries

BACKGROUND

Coronary function testing in patients with ischemia and nonobstructive coronary arteries (INOCA) commonly includes assessment of adenosine-mediated vasodilation and acetylcholine spasm provocation. The purpose of this study was to evaluate the diagnostic value of additional endothelial function testing for the diagnosis of vasomotor dysfunction in patients with INOCA.

METHODS

In this retrospective cohort study, we included patients with INOCA who underwent clinically indicated comprehensive coronary function testing. Endothelial dysfunction was defined as a <50% increase in coronary blood flow, determined by Doppler flow, and/or epicardial vasoconstriction compared to baseline, in response to low-dose acetylcholine. Coronary artery spasm (CAS) was defined as vasospastic angina or microvascular angina in response to coronary high-dose acetylcholine. An impaired adenosine-mediated vasodilation was defined as a coronary flow reserve <2.5 and/or hyperemic microvascular resistance ≥2.5.

RESULTS

Among all 110 patients, 79% had endothelial dysfunction, 62% had CAS, and 29% had an impaired adenosine-mediated vasodilation. Endothelial dysfunction was present in 80% of patients who tested positively for CAS and/or an impaired adenosine-mediated vasodilation. Endothelial function testing increases the diagnostic yield of coronary function testing that only incorporates adenosine testing and spasm provocation by 17% to 92%. Of patients with normal adenosine-mediated vasodilation and no inducible CAS, 68% had endothelial dysfunction.

CONCLUSIONS

Concomitant endothelial dysfunction was prevalent in the vast majority of patients with INOCA with inducible CAS and/or an impaired adenosine-mediated vasodilation. In patients with INOCA without inducible CAS and normal adenosine-mediated vasodilation, two-thirds had endothelial dysfunction. These results indicate the relevance to perform endothelial function testing in patients with INOCA in view of its therapeutic implication.

Vasospastic Angina: A Contemporary Review of its Pathophysiology, Diagnosis and Management

Nearly 40% of patients presenting to the catheter laboratory with angina have non-obstructed coronary arteries (ANOCA), an umbrella term that encompasses distinct pathophysiological entities, such as coronary artery spasm. Coronary artery spasm leads to sudden reversible coronary flow attenuation, which clinically manifests as vasospastic angina (VSA). VSA is associated with poor quality of life and an increased risk of major adverse cardiac events. However, the pathophysiological mechanisms underlying this phenomenon are incompletely understood, which has resulted in limited therapeutic options for patients afflicted with this condition. The past decade has seen a surge in new research being conducted in the field of ANOCA and VSA. This review article provides a comprehensive summary of the underlying pathophysiological mechanisms of VSA and the current therapeutic options. We also appraise the current diagnostic approach in patients with suspected VSA.

Comparison of Doppler Flow Velocity and Thermodilution Derived Indexes of Coronary Physiology

OBJECTIVES

The aim of this study was to compare Doppler flow velocity and thermodilution-derived indexes and to determine the optimal thermodilution-based diagnostic thresholds for coronary flow reserve (CFR).

BACKGROUND

The majority of clinical data and diagnostic thresholds for flow-based indexes are derived from Doppler measurements, and correspondence with thermodilution-derived indices remain unclear.

METHODS

An international multicenter registry was conducted among patients who had coronary flow measurements using both Doppler and thermodilution techniques in the same vessel and during the same procedure.

RESULTS

Physiological data from 250 vessels (in 149 patients) were included in the study. A modest correlation was found between thermodilution-derived CFR (CFRthermo) and Doppler-derived CFR (CFRDoppler) (r2 = 0.36; P < 0.0001). CFRthermo overestimated CFRDoppler (mean 2.59 ± 1.46 vs 2.05 ± 0.89; P < 0.0001; mean bias 0.59 ± 1.24 by Bland-Altman analysis), the relationship being described by the equation CFRthermo = 1.04 × CFRDoppler + 0.50. The commonly used dichotomous CFRthermo threshold of 2.0 had poor sensitivity at predicting a CFRDoppler value <2.5. The optimal CFRthermo threshold was 2.5 (sensitivity 75.54%, specificity 81.25%). There was only a weak correlation between hyperemic microvascular resistance and index of microvascular resistance (r2 = 0.19; P < 0.0001), due largely to variation in the measurement of flow by each modality. Forty-four percent of patients were discordantly classified as having abnormal microvascular resistance by hyperemic microvascular resistance (≥2.5 mm Hg · cm-1 · s) and index of microvascular resistance (≥25).

CONCLUSIONS

CFR calculated by thermodilution overestimates Doppler-derived CFR, while both parameters show modest correlation. The commonly used CFRthermo threshold of 2.0 has poor sensitivity for identifying vessels with diminished CFR, but using the same binary diagnostic threshold as for Doppler (<2.5) yields reasonable diagnostic accuracy. There was only a weak correlation between microvascular resistance indexes assessed by the 2 modalities.

Coronary flow reserve and cardiovascular outcomes: a systematic review and meta-analysis

AIMS

This meta-analysis aims to quantify the association of reduced coronary flow with all-cause mortality and major adverse cardiovascular events (MACE) across a broad range of patient groups and pathologies.

METHODS AND RESULTS

We systematically identified all studies between 1 January 2000 and 1 August 2020, where coronary flow was measured and clinical outcomes were reported. The endpoints were all-cause mortality and MACE. Estimates of effect were calculated from published hazard ratios (HRs) using a random-effects model. Seventy-nine studies with a total of 59 740 subjects were included. Abnormal coronary flow reserve (CFR) was associated with a higher incidence of all-cause mortality [HR: 3.78, 95% confidence interval (CI): 2.39-5.97] and a higher incidence of MACE (HR 3.42, 95% CI: 2.92-3.99). Each 0.1 unit reduction in CFR was associated with a proportional increase in mortality (per 0.1 CFR unit HR: 1.16, 95% CI: 1.04-1.29) and MACE (per 0.1 CFR unit HR: 1.08, 95% CI: 1.04-1.11). In patients with isolated coronary microvascular dysfunction, an abnormal CFR was associated with a higher incidence of mortality (HR: 5.44, 95% CI: 3.78-7.83) and MACE (HR: 3.56, 95% CI: 2.14-5.90). Abnormal CFR was also associated with a higher incidence of MACE in patients with acute coronary syndromes (HR: 3.76, 95% CI: 2.35-6.00), heart failure (HR: 6.38, 95% CI: 1.95-20.90), heart transplant (HR: 3.32, 95% CI: 2.34-4.71), and diabetes mellitus (HR: 7.47, 95% CI: 3.37-16.55).

CONCLUSION

Reduced coronary flow is strongly associated with increased risk of all-cause mortality and MACE across a wide range of pathological processes. This finding supports recent recommendations that coronary flow should be measured more routinely in clinical practice, to target aggressive vascular risk modification for individuals at higher risk.

Imaging Assessment of Endothelial Function: An Index of Cardiovascular Health

Endothelial dysfunction is a key early mechanism in a variety of cardiovascular diseases and can be observed in larger conduit arteries as well as smaller resistance vessels (microvascular dysfunction). The presence of endothelial dysfunction is a strong prognosticator for cardiovascular events and mortality, and assessment of endothelial function can aid in selecting therapies and testing their response. While the gold standard method of measuring coronary endothelial function remains invasive angiography, several non-invasive imaging techniques have emerged for investigating both coronary and peripheral endothelial function. In this review, we will explore and summarize the current invasive and non-invasive modalities available for endothelial function assessment for clinical and research use, and discuss the strengths, limitations and future applications of each technique.

Coronary Microvascular Angina: A State-of-the-Art Review

Up to 60–70% of patients, undergoing invasive coronary angiography due to angina and demonstrable myocardial ischemia with provocative tests, do not have any obstructive coronary disease. Coronary microvascular angina due to a dysfunction of the coronary microcirculation is the underlying cause in almost 50% of these patients, associated with a bad prognosis and poor quality of life. In recent years, progress has been made in the diagnosis and management of this condition. The aim of this review is to provide an insight into current knowledge of this condition, from current diagnostic methods to the latest treatments.

Correlation and mechanism between cardiac magnetic resonance imaging and oral streptococcus count in patients with primary microvascular angina pectoris

BACKGROUND

Although primary microvascular angina (PMVA) can be diagnosed clinically, the etiology and pathophysiology of PMVA remain unclear. The effects of conventional clinical medications (aspirin, statins, and nitrates) are unsatisfactory, and PMVA can lead to serious cardiovascular events. The present study was designed to analyze the correlation between the load perfusion cardiovascular magnetic resonance imaging (CMR) results and the Streptococcus sanguinis(S sanguinis) count and the correlations between the S sanguinis count in oral cavity subgingival plaque and changes in the plasma levels of platelet alpha-granule membrane glycoprotein 140 (GMP-140), fibrinopeptide A (FPA), von Willebrand factor (vWF), and homocysteine (Hcy) in patients with PMVA after increased anti-infective treatment of the oral cavity. This study also discusses the pathogenesis of PMVA from this perspective. The differences in the S sanguinis count in oral cavity subgingival plaque and oral health status between healthy people and PMVA patients will be compared, and the correlation between the oral cavity health status and disease in PMVA patients will be analyzed.

METHODS

The present randomized controlled trial with a parallel control group will be conducted in 68 PMVA patients diagnosed by the in-patient cardiology department. The selected patients will be randomly divided into 2 groups, one receiving routine drug treatment and the other a combination of anti-infective treatments. The normal control group will comprise 30 healthy people with no infectious oral cavity disease matched by age and sex. We will conduct CMR, and the presence of S sanguinis in subgingival plaques will be used to determine the bacterial count in PMVA patients. Blood samples will also be collected to determine the levels of GMP-140, FPA, vWF, and Hcy. S sanguinis in the subgingival plaque of PMVA patients will be further analyzed after increasing the oral cavity anti-infective treatment; the resulting changes and their correlations with changes in GMP-140, FPA, vWF, and Hcy levels will be assessed. Additionally, the differences in the S sanguinis count and the oral cavity health status of oral cavity dental plaque between healthy people and PMVA patients will be determined, and the correlation between the oral cavity conditions and PMVA will be analyzed. The relationship between the perfusion CMR results and the oral cavity S sanguinis count of PMVA patients, and the potential pathogenesis, will be explored. We will use the SPSS19.0 statistical software package to analyze the data. The measurements will be expressed as means±standard deviation. Student t test will be used for intergroup comparisons, a relative number description will be used for the count data, and the chi-square test will be used for intergroup comparisons. Multivariate logistic regression will be performed to identify associations. A P value < .05 will be considered significant.

DISCUSSION

In this study, the correlation between the perfusion CMR results and the S sanguinis count in oral cavity subgingival plaque of PMVA patients will be analyzed. Changes in the levels of GMP-140, FPA, vWF, and Hcy of PMVA patients after receiving increased oral cavity anti-infective treatment will be explored, and the difference in the S sanguinis count in oral cavity subgingival plaque and the oral cavity health status between healthy people and PMVA patients will be compared.

ATRIAL REGISTRATION

Chinese Clinical Trial Registry, (http://www.chictr.org.cn/showprojen.aspx?proj=45091).

Evaluate the Correlation between the TIMI Frame Count, IMR, and CFR in Coronary Microvascular Disease

Objective

To evaluate the correlation between the TIMI frame count, IMR, and CFR in coronary microvascular disease (slow flow phenomenon).

Methods

TFC and IMR were recorded in the nitroglycerin and ATP administration states, and the relationship between TFC, IMR, and CFR in specific states was analyzed.

Results

A total of 41 patients with baseline TFC >25 frames on coronary angiography were enrolled, and nitroglycerin reduced TFC by 50% from baseline in 24 (58.54%) patients; 16 of the remaining 17 patients were able to achieve a 50% reduction in TFC by further intracoronary ATP injection. 10 patients were further tested for IMR, and the results showed significant correlations between baseline TFC and IMR (r = 0.775, P=0.008), TFC and IMR after nitroglycerin (r = 0.875, P=0.001), and the minimal TFC and IMR that could be obtained with nitroglycerin or ATP administration (r = 0.890, P=0.001). There was also a significant correlation between the proportional improvement in TFC and CFR before and after nitroglycerin injection (r = 0.685, P=0.029). In addition, we observed a lower IMR measured after nitroglycerin than after ATP in three patients, suggesting that CMD may be dominated by NO-sensitive vascular such as prearterioles and that an extensive analysis of the target site of CMD may be achieved by stepwise drug administration.

Conclusion

Induction of TFC in different states by a stepwise drug approach may serve as a potential primary screening method for coronary microcirculatory dysfunction, thereby reducing the need for further IMR or CFR testing.

Ischemia and no obstructive coronary arteries in patients with stable ischemic heart disease

A large proportion of patients with suspected obstructive coronary artery disease (CAD) is found to have ischemia with no obstructive coronary artery disease (INOCA). Based on current evidence, these patients are at increased risk of adverse cardiovascular events, even though they have no obstructive CAD. Importantly, INOCA is associated with recurrent clinical presentations with chest pain, impaired functional capacity, reduced health-related quality of life, and high healthcare costs. Underlying coronary microvascular dysfunction (CMD), through endothelium-dependent and independent mechanisms contribute to these adverse outcomes in INOCA. While non-invasive and invasive diagnostic testing has typically focused on identification of obstructive CAD in symptomatic patients, functional testing to detect coronary epicardial and microvascular dysfunction should be considered in those with INOCA who have persistent angina. Current diagnostic methods to clarify functional abnormalities and treatment strategies for epicardial and/or microvascular dysfunction in INOCA are reviewed.

Untangling the pathophysiologic link between coronary microvascular dysfunction and heart failure with preserved ejection fraction

Coronary microvascular disease (CMD), characterized by impaired coronary flow reserve (CFR), is a common finding in patients with stable angina. Impaired CFR, in the absence of obstructive coronary artery disease, is also present in up to 75% of patients with heart failure with preserved ejection fraction (HFpEF). Heart failure with preserved ejection fraction is a heterogeneous syndrome comprising distinct endotypes and it has been hypothesized that CMD lies at the centre of the pathogenesis of one such entity: the CMD–HFpEF endotype. This article provides a contemporary review of the pathophysiology underlying CMD, with a focus on the mechanistic link between CMD and HFpEF. We discuss the central role played by subendocardial ischaemia and impaired lusitropy in the development of CMD–HFpEF, as well as the clinical and research implications of the CMD–HFpEF mechanistic link. Future prospective follow-up studies detailing outcomes in patients with CMD and HFpEF are much needed to enhance our understanding of the pathological processes driving these conditions, which may lead to the development of physiology-stratified therapy to improve the quality of life and prognosis in these patients.

Invasive and non-invasive assessment of ischaemia in chronic coronary syndromes: translating pathophysiology to clinical practice

Intracoronary physiology testing has emerged as a valuable diagnostic approach in the management of patients with chronic coronary syndrome, circumventing limitations like inferring coronary function from anatomical assessment and low spatial resolution associated with angiography or non-invasive tests. The value of hyperaemic translesional pressure ratios to estimate the functional relevance of coronary stenoses is supported by a wealth of prognostic data. The continuing drive to further simplify this approach led to the development of non-hyperaemic pressure-based indices. Recent attention has focussed on estimating physiology without even measuring coronary pressure. However, the reduction in procedural time and ease of accessibility afforded by these simplifications needs to be counterbalanced against the increasing burden of physiological assumptions, which may impact on the ability to reliably identify an ischaemic substrate, the ultimate goal during catheter laboratory assessment. In that regard, measurement of both coronary pressure and flow enables comprehensive physiological evaluation of both epicardial and microcirculatory components of the vasculature, although widespread adoption has been hampered by perceived technical complexity and, in general, an underappreciation of the role of the microvasculature. In parallel, entirely non-invasive tools have matured, with the utilization of various techniques including computational fluid dynamic and quantitative perfusion analysis. This review article appraises the strengths and limitations for each test in investigating myocardial ischaemia and discusses a comprehensive algorithm that could be used to obtain a diagnosis in all patients with angina scheduled for coronary angiography, including those who are not found to have obstructive epicardial coronary disease.

Cardiovascular magnetic resonance image analysis and mechanism study for the changes after treatments for primary microvascular angina pectoris

ABSTRACT

Most cases of primary microvascular angina pectoris (PMVA) are diagnosed clinically, but the etiology and pathological mechanisms are unknown. The effect of routine clinical medications is minimal, and PMVA can progress to serious cardiovascular events. To improve the diagnosis and effective treatment of this disease, this study was designed to diagnose PMVA via cardiovascular magnetic resonance (CMR) and the coronary angiography thrombolysis in myocardial infarction (TIMI) blood flow grade, as well as to analyze vascular endothelial function to elucidate the pathogenesis of PMVA and compare the effects of routine clinical medications.The present randomized controlled trial including a parallel control group will be conducted on 63 PMVA patients in our cardiovascular department. The patients will be selected and randomly divided into the control, diltiazem, and nicorandil groups. The control group will be administered routine drug treatments (aspirin, atorvastatin, betaloc ZOK, perindopril, and isosorbidemononitrate sustained-release tablets). The diltiazem group will be additionally treated with 90 mg qd diltiazem sustained-release capsules. The nicorandil group was additionally given 5 mg tid nicorandil tablets. Coronary angiography will be performed before treatment, the severity and frequency of chest pain will be evaluated before and after 9 months of treatment, and homocysteine and von Willebrand factor levels will be measured. Electrocardiography, echocardiography, dynamic electrocardiography, a treadmill exercise test, and CMR will be performed. Sex, age, body mass index, complications, smoking, and family history will also be recorded. The SPSS19.0 statistical software package will be used to analyze the data. The measurements will be expressed as the mean ± standard deviation. Measurement data will be compared between the groups using Student's t-test. A relative number description will be used for the counting data, and the chi-squaretest will be used to compare the groups. A multivariate logistic regression analysis will be performed A P-value < .05 will be considered significant.The direct indices (CMR and coronary angiographic TIMI blood flow grade) may improve after adding diltiazem or nicorandil during routine drug treatments (such as aspirin, statins, and nitrates) in PMVA patients, and indirect indices (homocysteine and von Willebrand factor levels) may be reduced.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (http://www.chictr.org.cn/showprojen.aspx?proj=41894), No. CHiCTR1900025319, Registered on August 23, 2019; pre initiation.

Berries and Their Polyphenols as a Potential Therapy for Coronary Microvascular Dysfunction: A Mini-Review

Ischemia with no obstructive coronary artery disease (INOCA) is a common diagnosis with a higher prevalence in women compared to men. Despite the absence of obstructive coronary artery disease and no structural heart disease, INOCA is associated with major adverse cardiovascular outcomes as well a significant contributor to angina and related disability. A major feature of INOCA is coronary microvascular dysfunction (CMD), which can be detected by non-invasive imaging and invasive coronary physiology assessments in humans. CMD is associated with epicardial endothelial-dependent and -independent dysfunction, diffuse atherosclerosis, and left-ventricular hypertrophy, all of which lead to insufficient blood flow to the myocardium. Inflammatory and oxidative stress signaling, upregulation of the renin-angiotensin-aldosterone system and adrenergic receptor signaling are major drivers of CMD. Treatment of CMD centers around addressing cardiovascular risk factors; however, there are limited treatment options for those who do not respond to traditional anti-anginal therapies. In this review, we highlight the ability of berry-derived polyphenols to modulate those pathways. The evidence supports the need for future clinical trials to investigate the effectiveness of berries and their polyphenols in the treatment of CMD in INOCA patients.

Coronary microvascular disease: current concepts of pathophysiology, diagnosis and management

Coronary microvascular disease (CMD) is present in 30% of patients with angina and is associated with increased morbidity and mortality. We now have an improved understanding of the pathophysiology of CMD and the invasive and noninvasive tests that can be used to make the diagnosis. Recent studies have shown that management of CMD guided by physiological testing yields better results than empirical treatment. Despite major advances in diagnosing and stratifying this condition, therapeutic strategies remain limited and poorly defined. This review article discusses recent advances in understanding the pathophysiology of CMD, the modalities that are available to diagnose it clinically, current management options and a look at what is in store for the future.

The effectiveness and safety of nicorandil in the treatment of patients with microvascular angina: A protocol for systematic review and meta-analysis

BACKGROUND

Microvascular angina has become a clinical and frequent cardiovascular disease in recent years, which is complicated and there is no clear treatment. Today, Western medicine still deals with microvascular angina with standardized treatment based on the stable angina. Firstly, it is to control the risk factors of atherosclerosis, and the second is to reduce the oxygen consumption of the patient's heart muscle. In the previous randomized controlled clinical trials, it has shown that nicorandil can improve the symptoms of angina for the treatment of microvascular angina, but there is a lack of high-quality randomized controlled trials on the clinical effectiveness and safety of nicorandil in the treatment of microvascular angina, and the lack of evaluation of its effectiveness and safety. Therefore, this paper aims to understand whether nicorandil can further improve the prognosis of patients with microvascular angina and the safety of the drug through the method of systematic evaluation.

METHODS

Retrieval of relevant network electronic databases by computer: SinoMed, CNKI, WanFang Data, VIP, PubMed, EMbase and The Cochrane Library, the retrieval time is from the establishment of each database to December 2017, to collect randomized controlled studies of nicorandil in the treatment of microvascular angina. At the same time, it is supplemented by manual search of the included literature references, as far as possible to increase the included literature imformation. Two researchers independently browse the topics and abstracts, and select, find, read the full text of the relevant literature, and screen the literature according to the criteria for inclusion and exclusion established in advance, then extract the data, and cross-check, and resolve the differences through multi-person discussion. Data analysis of collected information is performed by using RevMan 5.3 software.

RESULTS

The data of the included literature are statistically analyzed by meta-analysis, and the key outcome indicators are used to determine whether nicorandil can further improve the prognosis of patients with microvascular angina and the safety of the drug.

CONCLUSION

Through the method of evidence-based medicine, this study finds the existing problems and defects in the current research, which will provide high-quality evidence-based medical evidence for nicorandil's treatment of microvascular angina, and it help the clinical treatment and further research.

OSF REGISTRATION NUMBER

DOI 10.17605/OSF.IO/DSQG9.

Coronary provocative tests in the catheterization laboratory: Pathophysiological bases, methodological considerations and clinical implications

The paradigm for the management of patients presenting with angina and/or myocardial ischemia has been historically centered on the detection and treatment of obstructive coronary artery disease (CAD). However, in a considerable proportion (30-50%) of patients undergoing coronary angiography, obstructive CAD is excluded. Thus, functional mechanisms may be involved in determining myocardial ischemia and should be investigated. In particular, coronary vasomotor disorders both at epicardial and at microvascular level may play a crucial role, but a definitive diagnosis of these disorders can at times be difficult, given the transience of symptoms, and often requires the use of coronary provocative tests. Of importance, these tests may provide relevant information on the pathogenic mechanism of myocardial ischemia, allowing physicians to tailor the therapies of their patients. Furthermore, several studies underscored the important prognostic information deriving from the use of coronary provocative tests. Nevertheless, their use in clinical practice is currently limited and mainly restricted to specialized centers, with only a minority of patients receiving a benefit from this diagnostic approach. In this review, we explain the pathophysiological bases for the use of provocative tests, along with their clinical, prognostic and therapeutic implications.

High-Resolution Cardiac Magnetic Resonance Imaging Techniques for the Identification of Coronary Microvascular Dysfunction

OBJECTIVES

This study assessed the ability to identify coronary microvascular dysfunction (CMD) in patients with angina and nonobstructive coronary artery disease (NOCAD) using high-resolution cardiac magnetic resonance (CMR) and hypothesized that quantitative perfusion techniques would have greater accuracy than visual analysis.

BACKGROUND

Half of all patients with angina are found to have NOCAD, while the presence of CMD portends greater morbidity and mortality, it now represents a modifiable therapeutic target. Diagnosis currently requires invasive assessment of coronary blood flow during angiography. With greater reliance on computed tomography coronary angiography as a first-line tool to investigate angina, noninvasive tests for diagnosing CMD warrant validation.

METHODS

Consecutive patients with angina and NOCAD were enrolled. Intracoronary pressure and flow measurements were acquired during rest and vasodilator-mediated hyperemia. CMR (3-T) was performed and analyzed by visual and quantitative techniques, including calculation of myocardial blood flow (MBF) during hyperemia (stress MBF), transmural myocardial perfusion reserve (MPR: MBF_HYPEREMIA / MBF_REST), and subendocardial MPR (MPR_ENDO). CMD was defined dichotomously as an invasive coronary flow reserve <2.5, with CMR readers blinded to this classification.

RESULTS

A total of 75 patients were enrolled (57 ± 10 years of age, 81% women). Among the quantitative perfusion indices, MPR_ENDO and MPR had the highest accuracy (area under the curve [AUC]: 0.90 and 0.88) with high sensitivity and specificity, respectively, both superior to visual assessment (both p < 0.001). Visual assessment identified CMD with 58% accuracy (41% sensitivity and 83% specificity). Quantitative stress MBF performed similarly to visual analysis (AUC: 0.64 vs. 0.60; p = 0.69).

CONCLUSIONS

High-resolution CMR has good accuracy at detecting CMD but only when analyzed quantitatively. Although omission of rest imaging and stress-only protocols make for quicker scans, this is at the cost of accuracy compared with integrating rest and stress perfusion. Quantitative perfusion CMR has an increasingly important role in the management of patients frequently encountered with angina and NOCAD.