Coronary Microvascular Dysfunction Screening in Asymptomatic Adults

Abstract

Coronary microvascular dysfunction (CMD) is increasingly recognized as a significant contributor to adverse cardiovascular outcomes, even in the absence of overt symptoms or obstructive coronary artery disease. Early detection and screening in asymptomatic adults, particularly those with risk factors, may offer opportunities for early intervention and risk stratification. This review discusses the epidemiology, pathophysiology, risk factors, clinical features, diagnostic approaches, and management strategies for CMD in asymptomatic populations, incorporating recent advances and guideline-based recommendations to inform clinical practice.

Introduction

Coronary microvascular dysfunction (CMD) refers to impaired vasodilatory function and/or increased microvascular resistance in the small coronary arterioles that cannot be explained by obstructive epicardial coronary disease. While CMD has been traditionally underrecognized, mounting evidence implicates it as a cause of myocardial ischemia, heart failure with preserved ejection fraction (HFpEF), and increased cardiovascular morbidity and mortality. In asymptomatic adults, CMD may remain silent yet contribute to progressive myocardial remodeling and adverse events. With the advent of advanced imaging and functional assessment tools, the focus has shifted toward early identification and risk stratification in at-risk but asymptomatic individuals. This review synthesizes current knowledge on CMD screening, providing an academic and practical resource for clinicians seeking to optimize cardiovascular prevention strategies.

Epidemiology / Disease Burden

The true prevalence of CMD in asymptomatic adults is difficult to ascertain due to historically limited screening and diagnostic options. However, population-based studies suggest that up to 30% of individuals with evidence of myocardial ischemia do not have obstructive epicardial coronary artery disease, and a substantial subset of these cases are attributable to microvascular dysfunction. CMD is particularly prevalent in women, individuals with diabetes mellitus, metabolic syndrome, hypertension, and those with a family history of premature coronary artery disease. In large registries, CMD has been linked to a two- to four-fold increase in major adverse cardiovascular events (MACE) compared to matched controls, underscoring its clinical relevance even in asymptomatic populations. The burden is likely underestimated, as conventional risk assessment tools and stress testing may fail to identify microvascular disease in the absence of overt symptoms or epicardial stenoses.

Pathophysiology

CMD is characterized by structural and functional abnormalities in the coronary microcirculation. Key mechanisms include endothelial dysfunction, reduced nitric oxide bioavailability, increased oxidative stress, inflammation, and remodeling of the microvascular bed. These pathophysiological changes result in impaired coronary flow reserve (CFR), abnormal vasoreactivity, and microvascular spasm. Chronic exposure to cardiometabolic risk factors accelerates these processes, contributing to myocardial ischemia, fibrosis, and ultimately left ventricular dysfunction. Unlike epicardial atherosclerosis, CMD often occurs in the absence of significant luminal narrowing but can precipitate similar adverse cardiac outcomes. Recent evidence highlights the interplay between systemic inflammation, metabolic dysregulation, and microvascular integrity, suggesting a shared pathophysiological substrate with other forms of cardiovascular disease.

Risk Factors

Traditional cardiovascular risk factors play a prominent role in the development of CMD. These include advancing age, female sex (particularly postmenopausal women), hypertension, diabetes mellitus, dyslipidemia, obesity, smoking, and a sedentary lifestyle. Non-traditional risk modifiers such as chronic kidney disease, systemic inflammatory and autoimmune disorders (e.g., rheumatoid arthritis, lupus), and psychosocial stress have also been implicated. Genetic predisposition and familial clustering further suggest heritable components. Recognition of these risk factors in asymptomatic adults is crucial for targeted screening and preventive strategies in clinical practice.

Clinical Features

By definition, CMD in asymptomatic adults is clinically silent; however, subtle manifestations may include reduced exercise capacity or non-specific fatigue. In symptomatic patients, CMD can present as angina with nonobstructive coronary arteries (ANOCA) or as part of the syndrome of ischemia with no obstructive coronary artery disease (INOCA). In asymptomatic individuals, the absence of chest pain or dyspnea does not preclude the presence of significant microvascular dysfunction, which may progress undetected until the development of overt cardiovascular disease, arrhythmias, or heart failure. Subclinical myocardial ischemia can lead to progressive structural changes detectable only with advanced imaging or functional testing.

Diagnosis

Screening for CMD in asymptomatic adults is not universally recommended but may be considered in selected high-risk populations. Diagnostic approaches include noninvasive and invasive assessments of coronary flow reserve (CFR) and microvascular function. Noninvasive modalities such as positron emission tomography (PET), cardiac magnetic resonance imaging (CMR) with vasodilator stress, and transthoracic Doppler echocardiography can quantify CFR and detect microvascular impairment. PET, in particular, is considered the gold standard due to its high sensitivity and reproducibility. Invasive coronary function testing, performed during coronary angiography, assesses endothelium-dependent and independent microvascular reactivity, typically using acetylcholine or adenosine. Biomarkers of endothelial dysfunction and systemic inflammation may provide adjunctive information but lack specificity. The choice of screening modality should be individualized based on risk profile, availability, and clinical context.

Treatment & Management

Management of CMD in asymptomatic adults focuses on aggressive risk factor modification, lifestyle intervention, and pharmacological therapies targeting the underlying pathophysiology. Optimal control of blood pressure, glycemic status, and lipid profiles is paramount. First-line pharmacotherapy may include statins, angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs), and beta-blockers, all of which have demonstrated microvascular benefits beyond their primary indications. Emerging evidence supports the use of novel agents such as sodium-glucose cotransporter 2 (SGLT2) inhibitors and GLP-1 receptor agonists, particularly in individuals with diabetes or metabolic syndrome. Antiplatelet therapy is generally reserved for those with concomitant atherosclerotic disease. Non-pharmacological strategies, including structured exercise, dietary modification, and smoking cessation, remain foundational. Patient education and shared decision-making are critical for long-term adherence and prevention of disease progression.

Recent Advances / Emerging Therapies

Recent clinical trials have evaluated the role of novel cardiovascular agents in improving microvascular function and outcomes. SGLT2 inhibitors and GLP-1 receptor agonists have shown promise in reducing cardiovascular events and improving myocardial perfusion independent of glycemic control. Anti-inflammatory therapies, such as colchicine and interleukin-1β inhibitors, are being explored for their potential to modulate microvascular inflammation. Advances in noninvasive imaging, including higher resolution PET and CMR mapping, allow earlier detection and quantification of CMD. Machine learning and biomarker-based approaches are under investigation for risk stratification and personalized screening algorithms. These innovations hold promise for refining CMD detection and guiding tailored interventions in asymptomatic populations.

Guideline Recommendations

Major cardiovascular societies, including the American Heart Association (AHA) and European Society of Cardiology (ESC), acknowledge the clinical importance of CMD but do not currently endorse routine screening in asymptomatic adults. Targeted screening may be considered in individuals with significant risk factors, unexplained left ventricular dysfunction, or evidence of ischemia without obstructive disease. The focus remains on intensive risk factor modification and primary prevention. Guidelines emphasize the need for further research to clarify the benefits, cost-effectiveness, and long-term outcomes of CMD screening in asymptomatic cohorts.

Conclusion

Coronary microvascular dysfunction is a clinically significant yet often underrecognized contributor to cardiovascular morbidity and mortality in asymptomatic adults. Early identification through targeted screening, particularly in high-risk individuals, may provide opportunities for preventive intervention and improved outcomes. Advances in diagnostic imaging and pharmacotherapy continue to refine our approach to CMD. Ongoing research and consensus-building are essential to establish evidence-based screening protocols and integrate CMD assessment into routine cardiovascular risk evaluation.