What is the diagnostic approach for stable angina?

Diagnostic Approach for Stable Angina

Begin with a thorough history and physical examination to assess pretest probability of ischemic heart disease, followed by resting ECG, then proceed to risk-stratified stress testing based on the patient's ability to exercise and ECG interpretability. 1

Initial Clinical Assessment

History and Symptom Characterization

• Classify chest pain into three categories: typical angina (substernal chest discomfort with characteristic quality and duration, provoked by exertion/emotional stress, relieved by rest or nitroglycerin), atypical angina (meets 2 of 3 criteria), or noncardiac chest pain (meets ≤1 criterion) 1
• Distinguish stable from unstable angina immediately: patients presenting with rest angina, severe new-onset angina, or increasing angina require categorization as high, moderate, or low-risk unstable angina and different management 1
• Document specific pain characteristics: quality, location, duration, triggering factors (exertion, emotional stress), and relieving factors (rest, nitroglycerin) 1

Risk Factor Assessment

• Evaluate cardiovascular risk factors systematically: age, sex, diabetes mellitus (particularly important as it confers high risk for macrovascular disease), hyperlipidemia, smoking, hypertension, family history of premature CAD, and postmenopausal status in women 1
• Diabetes is the most critical risk factor to identify as it substantially increases CAD probability beyond other risk factors 1

Pretest Probability Estimation

• Calculate pretest probability using age, sex, and pain characteristics: this determines all subsequent testing decisions 1
• Low probability: <10-20%; Intermediate probability: 10-90%; High probability: >80-90% 1
• Risk factors (especially diabetes, hyperlipidemia, smoking) increase the probability estimates 1

Physical Examination

• Assess for alternative causes: valvular heart disease (murmurs suggesting aortic stenosis), hypertrophic cardiomyopathy, signs of heart failure, or conditions increasing myocardial oxygen demand (hyperthyroidism, severe uncontrolled hypertension) 1
• Evaluate for conditions decreasing oxygen supply: anemia, hypoxemia from pulmonary disease 1

Initial Diagnostic Testing

Resting Electrocardiogram

• Obtain resting ECG in all patients without obvious noncardiac cause of chest pain 1
• Note that >50% of patients with chronic stable angina have normal resting ECG 1
• Findings favoring CAD diagnosis: left ventricular hypertrophy, ST-T wave changes consistent with ischemia, evidence of prior Q-wave MI 1
• Identify ECG features that preclude standard exercise testing: preexcitation (Wolff-Parkinson-White) syndrome, electronically paced ventricular rhythm, >1 mm ST depression at rest, complete left bundle-branch block 1

Shared Decision-Making

• Engage patients in shared decision-making regarding diagnostic and therapeutic options, explaining risks, benefits, and costs 1

Risk Stratification Through Stress Testing

For Patients Able to Exercise with Interpretable ECG

Standard exercise ECG (Bruce protocol with Duke treadmill score) is the initial test for patients with intermediate pretest probability of IHD who have interpretable ECG and at least moderate physical functioning 1

• Duke treadmill score calculation: exercise time (minutes) − (5 × ST-segment deviation in mm) − 4 (if angina occurs) − 8 (if angina causes test termination) 1
• Low risk (score ≥5): 4-year survival 99%, annual mortality 0.25% 1
• High risk (score ≤−10): 4-year survival 79%, annual mortality 5% 1
• Do NOT use exercise stress with nuclear myocardial perfusion imaging as initial test in low-risk patients with interpretable ECG 1

For Patients with Uninterpretable ECG or Unable to Exercise Adequately

Use exercise stress with radionuclide myocardial perfusion imaging or echocardiography for patients with intermediate-to-high pretest probability who have uninterpretable ECG but can exercise 1

Use pharmacologic stress with radionuclide myocardial perfusion imaging or echocardiography for patients with intermediate-to-high pretest probability who cannot achieve at least moderate physical functioning or have disabling comorbidity 1

Important Contraindications

• Do NOT use pharmacologic stress testing in patients who have interpretable ECG and can exercise adequately 1
• Do NOT use standard exercise ECG in patients taking digoxin or with confounding ECG features 1

Assessment of Left Ventricular Function

Measure left ventricular function by resting echocardiography or radionuclide angiography in specific high-risk subgroups: 1

• Patients with history of MI
• Patients with pathologic Q waves on ECG
• Patients with symptoms or signs suggestive of heart failure
• Patients with complex ventricular arrhythmias

Left ventricular ejection fraction is the strongest predictor of long-term survival and guides therapeutic decisions regarding medical versus surgical therapy 1

Advanced Imaging Considerations

Coronary CT Angiography

• Coronary CT angiography has emerged as a first-line diagnostic test with higher sensitivity and comparable specificity to stress testing 2
• Allows detection of nonobstructive atherosclerosis not identified by other noninvasive modalities, improving risk assessment 2

Cardiac Magnetic Resonance

• CMR with dobutamine stress can detect wall motion abnormalities or perfusion defects 1
• Currently has Class II recommendations (clinically useful but supported by limited literature) 1

Coronary Angiography Indications

Reserve coronary angiography for: 1, 3

• Patients with estimated annual mortality >3% requiring assessment for revascularization
• Patients with severe or progressive angina despite optimal medical therapy
• Survivors of sudden cardiac death or life-threatening ventricular arrhythmias
• Patients with heart failure and suspected ischemic etiology
• When noninvasive testing is contraindicated, inconclusive, or limited by disability/comorbidity

Special Considerations

Women

• Classical angina symptoms are less reliable indicators of obstructive CAD in younger women compared to men 1
• Higher prevalence of coronary artery spasm and Syndrome X in women with chest pain 1
• Higher frequency of false-positive exercise tests in women 1

Common Pitfalls to Avoid

• Do not rely solely on noninvasive techniques if diagnostic doubt exists; cardiac catheterization definitively excludes or confirms coronary atherosclerosis or spasm 4
• Do not perform electron-beam CT as a screening test for CAD (sensitivity 80.4%, specificity only 39.9% with marked variability in repeated measures) 1
• Chest radiography is not useful for CAD diagnosis unless signs of heart failure, valvular disease, or pericardial disease are present 1