Unstable Angina and Stress Testing Guidelines
Risk Stratification
- Unstable angina patients should be categorized into low, intermediate, or high-risk groups based on clinical presentation, ECG findings, and cardiac biomarkers, as recommended by the American Heart Association 1, 2
- High-risk features include persistent ischemic pain, ST-segment changes, elevated cardiac biomarkers, and heart failure symptoms, according to the American College of Cardiology 1
- Low-risk patients include those with new-onset or progressive angina with symptoms provoked by walking, as defined by the American College of Cardiology 3, 4
Contraindications to Stress Testing
- High-risk unstable angina or acute myocardial infarction is explicitly listed as a contraindication to exercise ECG testing, as stated by the American Heart Association 5
- Patients with ongoing ischemia despite medical therapy should undergo prompt angiography without noninvasive risk stratification, as recommended by the American College of Cardiology 1, 2
- Active acute coronary syndrome is a contraindication to all forms of stress testing, including pharmacological stress tests, according to the American Heart Association 5
Timing of Stress Testing
- For low-risk patients with unstable angina who have stabilized, stress testing can be performed when patients have been free of active ischemic or heart failure symptoms for a minimum of 8-12 hours, as recommended by the American College of Cardiology 3, 4, 6
- The American College of Cardiology/American Heart Association guidelines specifically recommend noninvasive stress testing for low and intermediate-risk patients who have been free of ischemia at rest or with low-level activity and heart failure for a minimum of 12-24 hours 1
Evidence for Safety
- Limited evidence supports the use of exercise testing in acute coronary syndrome patients with appropriate indications as soon as the patient has stabilized clinically, as found by the American College of Cardiology 3, 6
- One review found that among patients with stabilized unstable angina, only a small percentage experienced adverse events within 24 hours of their exercise test, as reported by the American College of Cardiology 3, 4
Recommended Approach
- For patients with a normal resting ECG who are not taking digoxin, the exercise treadmill test should be the standard mode of stress testing, as recommended by the American College of Cardiology 3, 4
- An imaging modality should be added for patients with baseline ECG abnormalities, as recommended by the American Heart Association 1
- Pharmacological stress testing with imaging is recommended when physical limitations prevent adequate exercise, according to the American Heart Association 1, 5
Stress Echocardiogram in Unstable Angina
Contraindications and Precautions
- The American College of Cardiology recommends that patients with unstable angina who have not responded to intensive medical therapy should proceed directly to angiography without non-invasive risk stratification 7, 8, 9
- Patients with active ischemic symptoms, ST segment changes, elevated cardiac biomarkers, or symptoms of heart failure should not undergo stress testing 7
- Characteristics that contraindicate stress testing include prolonged resting angina (>20 minutes), transient ST segment changes >0.05 mV during pain, ischemia-related pulmonary edema, new mitral regurgitation murmur or S3, hemodynamic instability, and elevated troponin (>0.1 mg/mL) 7
Patient Selection for Stress Echocardiogram
- The American College of Cardiology suggests that stress echocardiogram can be performed in patients with unstable angina who are at low or intermediate risk and have been clinically stabilized, following strict criteria 7, 8, 9
- Low-risk patients should be free of ischemic symptoms or heart failure for at least 8-12 hours before the test, and the test should be performed within 72 hours of presentation if evaluated ambulatorily 7, 8
- Intermediate-risk patients should be free of resting ischemia or low-level activity for at least 2-3 days before the test, and may be evaluated earlier as part of a carefully structured chest pain management protocol 7, 8, 9
Indications for Pharmacological Stress Echocardiogram
- The American Heart Association recommends pharmacological stress testing with imaging (echocardiography or nuclear perfusion) when patients have physical limitations that prevent adequate exercise (arthritis, amputation, severe peripheral vascular disease, severe COPD, general weakness) 9
- Pharmacological stress testing is also indicated when patients have non-interpretable baseline ECG (bundle branch block, left ventricular hypertrophy, ST depression >0.10 mV, pacemaker rhythm, pre-excitation, digoxin effect) 9