What are the different types of stress tests and their indications?

Types of Stress Tests and Their Indications

Primary Stress Test Modalities

Exercise ECG (treadmill or bicycle) is the first-line stress test for patients who can exercise adequately and have an interpretable baseline ECG, as it provides both diagnostic information and functional capacity assessment at lower cost 1, 2.

Exercise-Based Stress Tests

Exercise ECG Testing

• Primary indication: Patients capable of achieving ≥5 METs of exercise with normal baseline ECG (no left bundle branch block, LV hypertrophy with strain pattern, or digitalis effect) 1, 3, 4
• Provides: Functional capacity assessment, blood pressure response, heart rate recovery, and ECG changes during physiologic stress 1, 2
• Contraindicated when: Baseline ECG abnormalities prevent interpretation, patient cannot exercise adequately, or absolute contraindications exist 1, 3

Exercise Stress Echocardiography

• Primary indication: Patients who can exercise but have uninterpretable baseline ECG (left bundle branch block, LV hypertrophy, paced rhythm) 1
• Additional indications: Assessment of valvular function during stress, evaluation of diastolic function reserve, and when wall motion assessment is needed 1, 2
• Advantage: Provides structural and functional information including valve gradients and pulmonary artery pressures 2

Exercise Nuclear Perfusion Imaging (SPECT/PET)

• Primary indication: Patients who can exercise but have uninterpretable baseline ECG 1
• Preferred in women: Nuclear imaging has better diagnostic accuracy than exercise ECG in female patients 4
• Provides: Myocardial perfusion assessment, infarct size quantification, and coronary flow reserve evaluation 2
• Critical contraindication: Avoid exercise nuclear imaging in left bundle branch block patients (use pharmacologic stress instead due to septal perfusion artifacts) 1

Pharmacologic Stress Tests

Pharmacologic stress testing should be reserved for patients unable to achieve adequate exercise (cannot reach 5 METs or stage II Bruce protocol) 1, 4.

Vasodilator Stress (Adenosine/Dipyridamole/Regadenoson) with Nuclear Imaging

• Primary indication: Patients unable to exercise adequately who need perfusion assessment 1, 2, 5
• Mechanism: Creates coronary "steal phenomenon" by maximal arteriolar vasodilation, revealing flow-limiting stenoses 2
• Preferred for: Left bundle branch block patients (adenosine/regadenoson preferred over exercise to avoid septal artifacts) 1
• Absolute contraindications: Second- or third-degree AV block without pacemaker, sinus node disease, bronchoconstrictive disease (asthma), hypotension <90 mmHg systolic, recent methylxanthine use 6, 5
• Regadenoson advantage: More favorable side-effect profile, safer in bronchospasm compared to adenosine/dipyridamole 1

Dobutamine Stress Echocardiography (DSE)

• Primary indication: Patients unable to exercise who need wall motion assessment or have contraindications to vasodilators 1, 2
• Specific indication: Low-gradient aortic stenosis with reduced ejection fraction (assesses contractile reserve) 1, 2
• Mechanism: Increases heart rate and contractility, creating demand ischemia 2
• Absolute contraindications: Critical aortic stenosis, hemodynamically significant LVOT obstruction, uncontrolled arrhythmias, severe hypertension, hypokalemia 6
• Avoid in: Serious arrhythmias, severe hypertension (≥200/110 mmHg), unstable patients 1, 6

Dobutamine Nuclear Perfusion Imaging

• Primary indication: Patients unable to exercise with contraindications to vasodilators (severe COPD, bronchospasm, high-grade AV block) 1, 2
• Alternative when: Echocardiographic windows are inadequate (morbid obesity, severe COPD) 1

Clinical Decision Algorithm

Step 1: Assess Exercise Capacity

• Can exercise to ≥5 METs? → Proceed to exercise-based testing 4
• Cannot exercise adequately? → Proceed to pharmacologic testing 1, 4

Step 2: Evaluate Baseline ECG

• Normal ECG, no digoxin → Exercise ECG (most cost-effective) 1, 3
• Uninterpretable ECG (LBBB, LV hypertrophy with strain, paced rhythm, digoxin) → Exercise imaging (echo or nuclear) 1
• LBBB specifically → Pharmacologic nuclear imaging (adenosine/regadenoson preferred) 1

Step 3: Select Pharmacologic Agent (if needed)

• No contraindications to vasodilators → Vasodilator nuclear imaging (regadenoson preferred for safety profile) 1, 5
• Bronchospasm/asthma, AV block, or vasodilator contraindications → Dobutamine stress (echo or nuclear) 1, 6
• Need valve assessment or adequate echo windows → Dobutamine stress echo 1, 2

Specific Clinical Scenarios

Preoperative Risk Assessment

• Can exercise: Exercise stress test (ECG or imaging based on baseline ECG) 1
• Cannot exercise: Pharmacologic stress imaging (DSE or nuclear) most commonly used 1, 3

Suspected Coronary Artery Disease

• Intermediate pretest probability with normal ECG: Exercise ECG 1
• Intermediate pretest probability with abnormal ECG: Exercise or pharmacologic stress imaging 1

Known Coronary Disease - Risk Stratification

• Asymptomatic, can exercise: Exercise stress test to assess functional capacity and ischemic threshold 1
• Change in symptoms: Stress imaging to assess extent and severity of ischemia 1, 2

Valvular Disease Assessment

• Aortic stenosis (mean gradient >30 mmHg) in young adults <30 years: Exercise stress testing to assess symptoms, blood pressure response, and exercise capacity 1
• Low-gradient aortic stenosis with reduced EF: Dobutamine stress echo to assess contractile reserve 1, 2
• Valvular disease with exertional symptoms: Exercise stress echo to assess gradient changes and pulmonary pressures 1, 2

Diastolic Dysfunction Evaluation

• Grade 1 diastolic dysfunction with exertional dyspnea: Exercise stress echo (supine bicycle preferred) to assess E/e' ratio and filling pressures with stress 1

Exertional Palpitations

• Palpitations during/after exercise: Exercise stress testing to reproduce symptoms and correlate with ECG findings 7

Absolute Contraindications to All Stress Testing

Do not perform stress testing in patients with 2, 6:

• Acute coronary syndrome or high-risk unstable angina
• Decompensated heart failure
• Severe symptomatic aortic stenosis
• Uncontrolled arrhythmias
• Acute aortic dissection
• Acute pericarditis or myocarditis
• Severe hypertension (≥200/110 mmHg)
• Acute pulmonary embolism

Key Prognostic Markers During Testing

High-risk findings requiring immediate attention 1:

• ST depression at low workload (<5 METs or stage I Bruce) persisting into recovery
• Failure to increase systolic BP >120 mmHg or sustained >10 mmHg drop during exercise
• ST-segment elevation (excluding aVR or leads with Q waves)
• Complex ventricular ectopy during stress or recovery
• Delayed heart rate recovery (<10-12 beats/min decrease in first minute)
• Large or multiple perfusion defects on nuclear imaging
• Extensive wall motion abnormalities on stress echo