Diagnostic Approach for Unstable Angina

Clinical Presentation and Diagnosis

The European Society of Cardiology recommends diagnosing unstable angina clinically when a patient presents with one of three specific patterns: rest angina lasting up to 20 minutes, crescendo angina, or new-onset severe angina causing marked limitation within 2 months of presentation 1, 2
Unstable angina manifests in three distinct ways that differentiate it from stable angina, including rest angina, crescendo angina, and new-onset severe angina 1, 2
Typical angina meets three characteristics: substernal chest discomfort of characteristic quality and duration, provoked by exertion or emotional stress, and relieved by rest and/or nitroglycerin 1, 2
Atypical angina meets two of the above characteristics 1, 2
Women and elderly patients often present with atypical symptoms including sharp chest pain, nausea, vomiting, or midepigastric discomfort 3, 4

The American Heart Association recommends immediately classifying patients into high-risk, intermediate-risk, or low-risk categories based on clinical features, as this determines the urgency of intervention and site of care 3, 4, 5
High-risk features include rest pain lasting >20 minutes, pulmonary edema, angina with S3 gallop, rales, or new/worsening mitral regurgitation murmur, hypotension, dynamic ST-segment changes ≥1 mm, and elevated cardiac troponin levels 5, 2
Intermediate-risk features include rest angina now resolved with moderate or high likelihood of CAD, rest angina (<20 minutes) relieved by rest or sublingual nitroglycerin, angina with dynamic T-wave changes, and new-onset Canadian Cardiovascular Society Class III or IV angina within 2 weeks 5
Low-risk features include no rest or nocturnal angina, normal or unchanged ECG, and increased angina frequency, severity, or duration without rest pain 7, 8, 5

The European Society of Cardiology recommends obtaining cardiac-specific troponin T or troponin I immediately in all patients with suspected unstable angina, as troponin-positive patients have up to 20% risk of death or MI at 30 days versus <2% in troponin-negative patients 2
Measure troponin or creatinine kinase MB (mass assay) when clinical suspicion of instability exists to exclude myocardial injury 1, 2
Obtain complete blood count (hemoglobin and total white cell count) for prognostic information 1, 2
Measure serum creatinine to evaluate renal function in all patients 1, 2

Dynamic ST-segment depression or elevation ≥1 mm indicates high risk 5
T-wave inversions >2 mm in multiple precordial leads suggest high risk 5
Normal or unchanged ECG does not exclude unstable angina but suggests lower risk 5, 7

Systematically evaluate for secondary causes that increase myocardial oxygen demand or decrease oxygen supply, as these may precipitate unstable angina in the presence of underlying CAD 3, 4, 7, 8
Conditions increasing oxygen demand include hyperthermia with volume contraction, hyperthyroidism, cocaine abuse or sympathomimetic toxicity, severe uncontrolled hypertension, and hypertrophic cardiomyopathy or aortic stenosis 3, 4, 7, 8
Conditions decreasing oxygen supply include anemia, hypoxemia from pulmonary disease, polycythemia, leukemia, thrombocytosis, or hypergammaglobulinemia 3, 4, 7, 8

Examine for signs of hemodynamic compromise, heart failure, valvular disease, or alternative diagnoses that may explain symptoms or alter management 3, 4, 5
Physical examination is usually normal or nonspecific in stable ischemic heart disease but may reveal heart failure, valvular disease, hypertrophic cardiomyopathy, or peripheral vascular disease 3, 4
Assess for pulmonary congestion (rales), S3 gallop, new mitral regurgitation murmur, or hypotension as markers of high risk 5