Screening for Subclinical Coronary Functional Abnormalities in Asymptomatic Adults

Abstract

Subclinical coronary functional abnormalities, encompassing impaired vasoreactivity and early endothelial dysfunction, are increasingly recognized as precursors to overt coronary artery disease (CAD) and major adverse cardiac events. Asymptomatic adults may harbor these abnormalities despite the absence of obstructive lesions, underscoring the value of early detection. This review synthesizes the epidemiology, pathophysiology, risk factors, clinical features, diagnostic modalities, management strategies, recent advances, and guideline recommendations regarding the screening of subclinical coronary functional abnormalities in asymptomatic populations, with a focus on evidence-based and clinically relevant insights for healthcare professionals.

Introduction

Coronary artery disease remains the leading cause of morbidity and mortality worldwide. While clinical attention often centers on overt atherosclerotic disease, a significant proportion of adverse cardiovascular outcomes occur in individuals without obstructive lesions but with functional coronary abnormalities. These subclinical functional changes, particularly microvascular and endothelial dysfunction, precede structural disease and may represent the earliest stage of the atherosclerotic continuum. As the paradigm shifts towards preventive cardiology, the utility of screening for such abnormalities in asymptomatic adults is a subject of growing interest. This article comprehensively reviews the current understanding of subclinical coronary functional abnormalities, the rationale and methods for screening, and the implications for clinical practice.

Epidemiology / Disease Burden

Subclinical coronary functional abnormalities are highly prevalent, with estimates suggesting that up to 50% of patients with ischemia and no obstructive coronary artery disease (INOCA) demonstrate impaired coronary vasoreactivity. Large population-based studies, such as the WISE (Women’s Ischemia Syndrome Evaluation) and PROMISE trials, have highlighted the substantial burden of microvascular dysfunction in both genders, though women are disproportionately affected. Autopsy and imaging studies indicate that early functional impairment may be present in up to 10-20% of asymptomatic middle-aged adults, translating to millions of individuals at increased risk for major adverse cardiac events (MACE) globally. Notably, such abnormalities often precede detectable atherosclerotic plaque by years, underscoring their significance for early intervention and risk stratification.

Pathophysiology

Coronary functional abnormalities primarily arise from impaired endothelial-dependent and/or independent vasodilation, resulting in inadequate coronary blood flow in response to metabolic demands. Mechanistically, endothelial dysfunction involves reduced nitric oxide bioavailability, increased oxidative stress, low-grade inflammation, and dysregulation of vasoconstrictor mediators such as endothelin-1. In the microvasculature, structural remodeling and impaired smooth muscle relaxation further contribute to flow limitation. Importantly, these functional disturbances often precede and promote atherogenesis, creating a vicious cycle that accelerates plaque formation and destabilization. Recent molecular studies implicate genetic factors, metabolic syndrome components, and environmental exposures in the pathogenesis of subclinical coronary dysfunction.

Risk Factors

Traditional cardiovascular risk factors hypertension, diabetes mellitus, dyslipidemia, smoking, and obesity are strongly associated with the development of subclinical coronary functional abnormalities. In addition, non-traditional factors such as chronic systemic inflammation (e.g., autoimmune diseases), psychosocial stress, sleep disorders, and certain medications (e.g., chemotherapeutic agents) have been implicated. Emerging evidence also highlights a role for genetic predisposition, particularly in individuals with a family history of premature CAD. Women, especially postmenopausal, are at elevated risk, and certain ethnic groups may exhibit higher susceptibility due to differences in microvascular function.

Clinical Features

By definition, subclinical coronary functional abnormalities are asymptomatic. However, subtle manifestations, such as reduced exercise tolerance or nonspecific fatigue, may rarely occur and are often overlooked. Importantly, these abnormalities set the stage for future symptomatic ischemia, angina with non-obstructive coronary arteries (ANOCA), and adverse cardiovascular outcomes. In some cases, unexplained arrhythmias or minor troponin elevations on biomarker screening may signal underlying functional disturbance. Recognizing high-risk individuals based on risk factor profiles and subclinical indicators is essential for targeted screening strategies.

Diagnosis

Diagnosing subclinical coronary functional abnormalities in asymptomatic adults remains challenging due to the lack of overt symptoms and the limitations of conventional imaging. Non-invasive assessment of endothelial function includes flow-mediated dilation (FMD) of the brachial artery, peripheral arterial tonometry (PAT), and coronary flow reserve (CFR) measurement via transthoracic Doppler echocardiography or cardiac magnetic resonance imaging (CMR). Advanced techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) may quantify myocardial blood flow and detect subtle perfusion defects. Invasive testing, including acetylcholine or adenosine coronary reactivity testing during coronary angiography, is considered gold standard but is rarely indicated in asymptomatic individuals outside research settings. Biomarkers such as high-sensitivity C-reactive protein (hsCRP), asymmetric dimethylarginine (ADMA), and specific microRNAs are being investigated as potential screening tools but are not yet established in clinical practice.

Treatment & Management

Management of subclinical coronary functional abnormalities centers on aggressive risk factor modification and lifestyle interventions. Evidence supports the benefit of statins, angiotensin-converting enzyme inhibitors (ACEIs), and angiotensin receptor blockers (ARBs) in improving endothelial function, independent of lipid-lowering effects. Antioxidant therapy, though promising in preclinical studies, has not demonstrated consistent benefit in large trials. Structured exercise programs, dietary modification (e.g., Mediterranean diet), and weight reduction are strongly recommended. Given the absence of symptoms, pharmacological intervention is generally reserved for individuals with high-risk profiles or evidence of progression on serial assessment. Patient education regarding adherence and long-term risk reduction is paramount.

Recent Advances / Emerging Therapies

Recent research has focused on the identification of novel biomarkers and the development of advanced imaging modalities to enhance the sensitivity and specificity of screening. The use of cardiac PET for quantifying myocardial blood flow and CFR has shown promise in large cohort studies. Endothelial progenitor cell-based therapies and targeted anti-inflammatory agents are emerging as potential disease-modifying interventions. Machine learning and artificial intelligence (AI) are being applied to integrate clinical, imaging, and biomarker data for refined risk prediction and personalized screening strategies. Ongoing trials are evaluating the long-term impact of early screening on cardiovascular outcomes in asymptomatic adults.

Guideline Recommendations

Current international guidelines, including those from the American College of Cardiology (ACC) and European Society of Cardiology (ESC), do not recommend routine screening for subclinical coronary functional abnormalities in the general asymptomatic population. However, targeted assessment may be considered in selected high-risk groups, such as individuals with a strong family history of premature CAD, multiple risk factors, or persistent abnormal biomarkers. The guidelines emphasize the importance of global risk assessment using validated tools (e.g., ASCVD risk calculator) and advocate for lifestyle and pharmacological interventions in accordance with the overall risk profile. Ongoing research may inform future updates and the potential role of more widespread screening.

Conclusion

Subclinical coronary functional abnormalities represent a pivotal, yet underrecognized, stage in the evolution of coronary artery disease. While routine population-wide screening remains controversial, selected high-risk asymptomatic adults may benefit from early detection and intervention. Advances in non-invasive diagnostics and emerging therapies hold promise for improved risk stratification and prevention. Integrating individualized risk assessment and targeted management into clinical practice is essential to reduce the burden of cardiovascular disease and improve long-term outcomes.