Diagnostic Challenge of Unstable Angina Pectoris with Persistently Low High-Sensitivity Cardiac Troponin I Levels: A Case Report

Background: High-sensitivity cardiac troponin I (hs-cTnI) is a key biomarker for detecting myocardial injury and is central to the diagnosis of acute coronary syndrome (ACS). However, in unstable angina pectoris (UAP), hs-cTnI levels may remain below the 99th percentile upper reference limit, making diagnosis challenging despite ongoing myocardial ischemia. This case report aims to highlight the diagnostic challenges of UAP in the presence of persistently low hs-cTnI levels and to emphasize the importance of integrating clinical assessment, serial electrocardiographic findings, and biomarker interpretation for accurate diagnosis. Case Presentation: A descriptive case report design was used. Clinical data were obtained from a 64-year-old male patient with hypertension and diabetes mellitus who presented to the emergency department with chest pain, palpitations, and mild shortness of breath. Diagnostic evaluation included serial electrocardiography, laboratory investigations including high-sensitivity cardiac troponin I (hs-cTnI), and comprehensive clinical assessment during hospitalization. Electrocardiography demonstrated sinus rhythm without acute ischemic changes throughout admission. Serial hs-cTnI measurements remained persistently low, ranging from 2.77 pg/mL to 4.35 pg/mL, with no dynamic rise or fall. Despite normal troponin levels and absence of myocardial necrosis, the patient was diagnosed with unstable angina pectoris based on typical ischemic chest pain and significant cardiovascular risk factors. Conclusion: This case illustrates the diagnostic complexity of UAP when hs-cTnI levels remain within the normal range. It highlights the necessity of integrating clinical evaluation, serial ECG findings, and risk stratification rather than relying solely on biomarkers. From a nursing perspective, comprehensive assessment, continuous hemodynamic monitoring, patient education, and early evidence-based intervention are essential. Multidisciplinary management is crucial to prevent progression to acute myocardial infarction and adverse outcomes.