Stress Testing¶
Exercise is preferred when the patient can exercise safely. It provides functional capacity, symptoms, ECG changes, blood-pressure response, and arrhythmia assessment.
Choosing the Stressor¶
| Situation | Stress method |
|---|---|
| Can exercise adequately | Exercise |
| Cannot exercise | Pharmacologic |
| LBBB or ventricular pacing | Vasodilator stress |
| Active wheezing or bronchospasm | Avoid vasodilators; consider dobutamine |
| Cannot exercise or receive a vasodilator | Dobutamine |
Note
Reaching 85% of age-predicted maximal heart rate is not an automatic stopping point. Continue until maximal effort, limiting symptoms, or another termination criterion.
Exercise ECG¶
Exercise ECG is appropriate when the patient can exercise and the baseline ECG is interpretable.
Add imaging for:
- LBBB
- Ventricular pacing
- Pre-excitation
- Resting ST depression ≥1 mm
- Digoxin-related ST changes
- Marked LVH with repolarization abnormality
RBBB alone does not make the ECG uninterpretable, although V1–V3 are unreliable for ischemia assessment.
Positive ECG Response¶
- ≥1 mm horizontal or downsloping ST depression
- Measured approximately 60–80 ms after the J point
- Occurring during exercise or recovery
New ST elevation ≥1 mm in a lead without a prior Q wave is a high-risk finding.
Duke Treadmill Score¶
Angina index:
- 0 = none
- 1 = nonlimiting
- 2 = exercise-limiting
| Score | Risk |
|---|---|
| ≥5 | Low |
| −10 to +4 | Intermediate |
| ≤−11 | High |
High-Risk Findings¶
- Exercise capacity <5 METs
- Ischemia at a low workload
- ≥2 mm ST depression
- ST depression persisting into recovery
- Exercise-induced ST elevation
- Fall in systolic blood pressure
- Limiting angina
- Ventricular tachycardia
- Abnormal heart-rate recovery
Achieving ≥10 METs without high-risk findings generally predicts a favorable prognosis.
Do Not Exercise¶
- Acute MI within approximately 2 days
- Ongoing unstable angina or ACS
- Hemodynamically significant arrhythmia
- Symptomatic severe aortic stenosis
- Decompensated heart failure
- Acute pulmonary embolism
- Acute myocarditis or pericarditis
- Acute aortic dissection
Stop the Test For¶
- Moderate-to-severe angina
- Sustained ventricular tachycardia
- Signs of poor perfusion
- Neurologic symptoms
- Ischemic ST elevation
- SBP decrease >10 mm Hg with ischemia
- Inability to monitor ECG or blood pressure
- Patient request
Pharmacologic Stress¶
| Agent | Mechanism | Important point |
|---|---|---|
| Adenosine | Nonselective adenosine agonist | Very short half-life |
| Dipyridamole | Increases endogenous adenosine | Longer duration |
| Regadenoson | Selective A2A agonist | Fixed 0.4-mg IV dose |
| Dobutamine | β1-mediated inotropy and chronotropy | Increases myocardial demand |
Avoid Vasodilators With¶
- Active wheezing or bronchospasm
- High-grade AV block without a pacemaker
- Sinus-node dysfunction without a pacemaker
- SBP <90 mm Hg
- Unstable ACS
- Recent caffeine or methylxanthine exposure
- Dipyridamole use within approximately 48 hours
Aminophylline can reverse serious vasodilator effects but should not be used for a regadenoson-associated seizure.
Board Pearls¶
- LBBB or ventricular pacing → vasodilator MPI
- Active wheezing + unable to exercise → consider dobutamine
- Exercise is preferred even when imaging is required
- Caffeine can invalidate vasodilator stress
- Regadenoson-related dyspnea does not necessarily mean bronchospasm
- Interpret symptoms, workload, ECG, hemodynamics, and imaging together