What is a 2-Day Stress Test?
A 2-day stress test is a nuclear myocardial perfusion imaging protocol where the rest and stress portions are performed on separate days, allowing for optimal image quality and reduced radiation exposure, particularly in patients with higher body mass index or those unable to complete adequate exercise stress in a single session. 1, 2
Types of Stress Tests
Exercise Stress Testing
- Traditional exercise stress testing involves continuous ECG monitoring with frequent blood pressure measurements during progressively increasing exercise intensity, typically using a treadmill or cycle ergometer 1
- Exercise is the preferred stress method when possible as it provides valuable physiologic data including exercise capacity, heart rate response, blood pressure response, and symptom assessment 2
- Approximately 67% of younger patients (<75 years) can achieve 85% of maximum predicted heart rate, while only 54% of elderly patients (>75 years) reach this target 3
Pharmacologic Stress Testing
- Used for patients who cannot exercise adequately due to physical limitations, deconditioning, peripheral vascular disease, orthopedic disabilities, neurological disease, or other comorbidities 1
- Two main categories of pharmacologic stress agents:
Two-Day Protocol for Nuclear Stress Testing
Day 1: Rest Study
- Patient receives radiotracer injection (typically technetium-99m sestamibi) at rest 3
- Imaging is performed to establish baseline myocardial perfusion 1
- This allows for optimal radiotracer dosing without residual activity from a same-day stress portion 2
Day 2: Stress Study
- Patient undergoes either exercise or pharmacologic stress 1, 2
- At peak stress, radiotracer is injected to capture perfusion during stress conditions 2
- Imaging is performed after stress to identify stress-induced perfusion defects 1
Advantages of 2-Day Protocol
- Allows for higher radiotracer doses, resulting in better image quality, particularly in larger patients 2
- Eliminates residual radiotracer activity from the rest portion that could interfere with stress images 2
- Provides more time for recovery between test components, which is beneficial for elderly or frail patients 3
- Reduces the likelihood of patient fatigue affecting test quality 2, 3
Common Stress Testing Modalities Used in 2-Day Protocols
SPECT/CT Myocardial Perfusion Imaging
- Uses intravenously administered tracers to evaluate cardiac pathophysiology, including ventricular function and myocardial perfusion 1
- Can be performed with either exercise or pharmacologic stress 1
- Provides insights into abnormalities of ventricular function (global and regional) 1
PET/CT Heart Stress
- Utilizes rubidium-82 or other tracers to reflect myocardial physiology, including perfusion, wall motion, and cardiac flow reserve 1
- Higher sensitivity than SPECT for detecting coronary artery disease 2
Stress Echocardiography
- Compares echocardiographic images at rest with those obtained during or immediately after stress 1
- Can be performed with exercise or pharmacologic agents 1, 5
- A test is considered positive if wall motion abnormalities develop with exercise in previously normal territories or worsen in an already abnormal segment 1
Safety Considerations
- Stress testing entails a small but definite risk (approximately 1 myocardial infarction or death per 2500 tests) 1
- Should only be performed with appropriate indications, careful consideration of contraindications, and under proper supervision 1
- Pharmacologic stress testing side effects may include:
- Elderly patients (>75 years) may experience more frequent side effects with pharmacologic stress agents, particularly atrioventricular block with adenosine 3