How often is unstable angina truly unstable? Insights from outpatient chest pain evaluation

Background

Chest pain is one of the most frequent causes of emergency department (ED) visits and cardiology referrals. However, the diagnostic yield and outcomes of patients referred for outpatientreassessment after suspected unstable angina (UA) remain poorly characterized in real-world practice.

Purpose

To describe the demographic and clinical profile of patients referred to a tertiary outpatient clinic for chest pain and to evaluate the rate and predictors of diagnostic reclassification, as well as itsimplications on DAPT use and clinical outcomes."

Methods

Retrospective observational study including 892 consecutive patients evaluated between January 2024 and December 2025. Continuous variables are presented as mean (SD) and categoricalvariables as frequencies (%). Associations were assessed using the chi-square test, with p<0.05 considered statistically significant. Analyses were performed using R version 4.4.2.

Results

Mean age was 63.9±11.9 years and 60.2% were male. Most referrals originated from the ED (96.7%). The leading referral diagnosis was UA (90.7%), followed by stable coronary artery disease(CAD) (6.9%) and other chest pain diagnoses (2.4%).

At first outpatient visit, 58.2% were on DAPT and 86.0% on statins. Hypertension (77.6%), dyslipidaemia (59.4%), and diabetes (36.9%) were common; prior CAD was documented in 46.7%.

After evaluation, the majority of patients initially referred to as UA were reclassified as chest pain without functionally significant ischemia (53.8%) or without obstructive coronary artery disease on invasive angiography (26.9%).

Most patients were managed conservatively or discharged. Percutaneous coronary intervention occurred predominantly in UA referrals (89.7%).

Conclusions

In this real-world cohort, most patients discharged from the emergency department with suspected unstable angina (UA) were ultimately reclassified as having non-obstructive or functionally non-significant disease after structured outpatient evaluation.

These findings raise important questions regarding the diagnostic accuracy of UA classification in the emergency setting. The high reclassification rate may reflect the inherent challenges of chestpain differential diagnosis under time pressure and clinical uncertainty. Alternatively, a subset of these patients may represent ischemia with non-obstructive coronary arteries (INOCA) or microvascular disease, entities systematically underdiagnosed without targeted investigation.

Structured outpatient reassessment is essential to refine diagnosis, prevent overtreatment ( including prolonged and unnecessary use of DAPT) and optimize resource allocation in suspected acute coronary syndrome cases.Outpatient Diagnostic Reclassification FlowPatient Pathway, Profile and Outcomes