Early Biomarkers of Acute Coronary Syndrome

Acute Coronary Syndrome Acute Coronary Syndrome (ACS) includes three related clinical conditions existing along a continuum of severity: unstable angina, non-ST segment elevation myocardial infarction, and ST segment elevation myocardial infarction. Early diagnosis and classification of ACS is important in an emergency setting for proper patient management. According to the latest guidelines of the American College of Cardiology, cardiac troponins are considered the most important biomarker of the condition after clinical history and electrocardiogram (ECG).[1] Emerging Biomarkers in Acute Coronary Syndrome The pursuit of early and reliable biomarkers for ACS has led to the identification of several promising candidates alongside troponins. Among these, heart-type fatty acid-binding protein (H-FABP), copeptin, pregnancy-associated plasma protein A, myeloperoxidase (MPO), and high-sensitivity C-reactive protein (hsCRP) have shown potential in providing additional prognostic and diagnostic information. These markers reflect diverse pathophysiological processes, including myocardial injury, oxidative stress, hemodynamic stress, and vascular inflammation, thereby enriching the clinician’s toolkit for the timely identification of at-risk populations and management of ACS patients.[2,3] More recently, circulating microRNAs (miRNAs) have emerged as a novel class of biomarkers with early molecular predictive power. Certain miRNAs are released rapidly into circulation during ischemic injury and may precede detectable rises in troponin levels, thereby enhancing early ACS detection. In particular, miRNA-21 has been identified as a key differentiating biomarker between ACS and non-ACS cases, offering the promise of earlier diagnosis and refined risk stratification.[4] These advances underscore the transition from reliance on a single biomarker toward a multimarker strategy, integrating both traditional and emerging indicators to improve patient outcomes. Troponins as the Cornerstone Biomarker in Acute Coronary Syndrome The troponin complex is an intracytoplasmic regulatory protein critical for the contraction and relaxation of striated muscle. It is composed of three subunits – troponin C, I, and T, which together mediate the interaction between calcium, actin, and myosin filaments. Troponin C is expressed in both skeletal and cardiac muscle, whereas the cardiac-specific isoforms of troponin T and troponin I are synthesized exclusively in cardiomyocytes, making them highly specific markers of myocardial damage.[5] Following myocardial cell death, serum troponin levels typically begin to rise within 4 h of injury. Troponin I remains detectable for approximately 4–7 days, whereas troponin T can persist for 10–14 days, allowing for both early diagnosis and delayed detection of myocardial infarction. The introduction of high-sensitivity cardiac troponin assays has revolutionized ACS diagnostics. These assays can detect circulating troponin concentrations at levels 10- to 100-fold lower than conventional assays, enabling earlier and more precise identification of myocardial injury, particularly within the first few hours of symptom onset.[6] Despite significant advances in troponin estimation, novel biomarkers such as H-FABP and copeptin, which rise earlier than troponins, may enhance early diagnosis when used in combination with it. These markers are particularly valuable in patients with inconclusive ECG findings or those presenting very soon after symptom onset, as they help exclude ACS with a high negative predictive value. H-FABP is of particular interest in this context; however, lack of specificity limits its usefulness as a standalone diagnostic marker.[7] Similarly, copeptin has emerged as an independent marker of total mortality and morbidity in patients with ACS, especially in those with multiple risk factors.[8] In several studies, the role of miRNAs has also been explored in identifying patients with ACS, but none have yet been able to outperform the diagnostic accuracy of cardiac troponins.[9] A recent meta-analysis evaluating the diagnostic potential of miRNA-21 highlighted the heterogeneity of results among different research subgroups, emphasizing the need for further studies to better define both the diagnostic and prognostic utility of this biomarker.[4] Considering factors such as cost, availability, and diagnostic specificity, cardiac troponins continue to remain the most reliable and widely used biomarkers of ACS in routine clinical practice. Expanded Role of Biomarkers in Acute Coronary Syndrome The role of biomarkers in ACS extends well beyond diagnosis. While cardiac troponins remain the gold standard for detecting myocardial necrosis, modern cardiovascular care increasingly relies on a spectrum of biomarkers to inform risk assessment, prognosis, and therapeutic decision-making. Biomarkers such as MPO and hsCRP emphasize the inflammatory basis of ACS. Unlike troponins, which are primarily diagnostic, MPO and hsCRP are more frequently applied as prognostic and disease-monitoring markers, reflecting ongoing vascular inflammation and plaque instability. Incorporating these markers into clinical algorithms allows for better prediction of recurrent events, risk stratification of patients, and potentially guides the use of anti-inflammatory therapies. Vitamin D as a Modifiable Biomarker in Acute Coronary Syndrome In addition to its classical metabolic roles, Vitamin D deficiency has been implicated in endothelial dysfunction, vascular inflammation, and pro-thrombotic states, thereby positioning it as a potential biomarker of ACS risk. Unlike troponins, which serve as markers of established myocardial injury, Vitamin D offers the unique advantage of being a modifiable factor. Serum levels can be readily assessed and deficiency corrected through supplementation. This raises the intriguing possibility that Vitamin D might not only serve as a risk predictor but also as a therapeutic target capable of influencing disease progression. While current evidence is largely observational, the concept of Vitamin D as a biomarker with interventional potential distinguishes it from most traditional cardiovascular biomarkers and highlights the need for prospective studies and randomized trials to validate its prognostic and disease-modifying roles. The article “Correlation between Vitamin D Levels and Troponin in Patients Suspected of Acute Coronary Syndrome: A Cross-Sectional ICU Study,” explores whether low Vitamin D might be associated with greater myocardial injury as reflected in higher troponin levels among patients with ACS, thereby linking nutritional status with the extent of myocardial injury. Vitamin D influences cardiovascular health through multiple mechanisms including suppression of the renin–angiotensin–aldosterone system, reducing hypertension and left ventricular hypertrophy, promotion of endothelial function by enhancing nitric oxide synthesis, anti-inflammatory effects with downregulation of pro-inflammatory cytokines, regulation of calcium homeostasis in cardiomyocytes, influencing contractility and hypertrophy.[10] The study’s findings echo earlier observational studies linking deficiency of Vitamin D with increased risk of cardiac events. However, inconsistent results have been produced by a few randomized controlled trials. The VITAL trial which enrolled over 25,000 participants, did not show a reduction in major cardiovascular events with Vitamin D supplementation, though subgroup analyses suggested a possible benefit in severely deficient individuals.[11] This discrepancy between observational and interventional evidence underscores the complexity of Vitamin D’s role in cardiovascular health. It is also possible that serum Vitamin D level is a risk marker but not a risk factor for cardiovascular disease risk and related underlying mechanisms.[12] Implications for Clinical Practice At present, Vitamin D testing is not routinely recommended in ACS patients, nor is supplementation established as a therapeutic intervention for reducing cardiac injury. The study under review contributes valuable preliminary evidence linking lower Vitamin D levels with greater myocardial injury, as measured by troponin I, in patients admitted with ACS. Despite limitations of sample size, cross-sectional design, and potential confounders, the findings align with longstanding hypotheses of Vitamin D as a modifiable cardiovascular risk factor. While current clinical practice should not change solely based on these data, the study underscores the need for continued investigation into the role of Vitamin D in cardiovascular disease. Ultimately, only large-scale, rigorously designed prospective studies and interventional trials will determine whether Vitamin D supplementation holds therapeutic promise in ACS and beyond.