What are the guidelines for conducting a cardiac stress test (cardiac stress test) on a patient?

Guidelines for Conducting a Cardiac Stress Test

A cardiac stress test should be performed in patients with suspected coronary artery disease (CAD) who have normal initial cardiac biomarkers and ECG, within 72 hours of presentation for low-risk patients or after 8-12 hours of observation for patients in chest pain units if they remain pain-free with normal ECGs and cardiac biomarkers. 1

Types of Stress Tests and Indications

Exercise Stress Testing

• Exercise testing is preferred over pharmacological stress testing whenever functional status permits 2
• Standard exercise treadmill testing is the initial procedure of choice for patients with a normal or near-normal resting ECG who are capable of adequate exercise 3
• Exercise stress testing can identify patients at risk of developing hypertension if they show an abnormal hypertensive response to exercise 4

When to Add Imaging to Exercise Testing

• Imaging modalities (echocardiography, nuclear imaging) should be added when patients have:
  • Resting ST-segment depression
  • Left ventricular hypertrophy
  • Bundle-branch block or intraventricular conduction defect
  • Pre-excitation syndrome
  • Digoxin therapy
  • Paced rhythm 1

Pharmacological Stress Testing

• Pharmacological stress testing should be used for patients who cannot exercise adequately 1
• Two categories of pharmacological stress agents are used:
  • Coronary vasodilating agents (dipyridamole, adenosine) that work directly on coronary vessels to increase blood flow
  • Cardiac positive inotropic agents (dobutamine, arbutamine) that work indirectly by increasing myocardial workload 5
• Dobutamine is administered starting at a low rate (0.5-1.0 μg/kg/min) and titrated at intervals of a few minutes, guided by patient response 6
• Optimal dobutamine infusion rates typically range from 2-20 μg/kg/min, but may occasionally require up to 40 μg/kg/min 6

Patient Risk Assessment and Testing Selection

Step-by-Step Approach for CAD Assessment

1. Determine urgency of surgery (if applicable) 2
2. For non-urgent cases, determine if patient has acute coronary syndrome 2
3. Estimate perioperative risk of major adverse cardiac events (MACE) based on combined clinical/surgical risk 2
4. If patient has low risk of MACE (<1%), no further testing is needed 2
5. If patient has elevated risk of MACE, determine functional capacity:
   • If ≥4 METs, proceed without further evaluation
   • If <4 METs or unknown, consider whether stress testing will impact decision-making 2

Contraindications to Stress Testing

• Acute coronary syndrome (unstable angina, STEMI, NSTEMI) 1
• Decompensated heart failure 2
• Severe/symptomatic aortic stenosis 2
• Uncontrolled arrhythmias 2
• Severe systemic arterial hypertension (≥200/110 mmHg) 2
• Acute aortic dissection 2
• Pericarditis/myocarditis 2
• Pulmonary embolism 2
• Severe pulmonary hypertension 2

Modality-Specific Contraindications

• Vasodilator stress imaging: significant arrhythmias, hypotension (SBP <90 mmHg), bronchospastic disease, recent use of dipyridamole or methylxanthines 2
• Dobutamine stress echocardiography: critical aortic stenosis, significant LVOT obstruction 2

Interpretation of Results and Risk Stratification

High-Risk Findings (>3% annual mortality)

• Exercise EF ≤0.50 or rest EF ≤0.35 2
• Stress-induced moderate perfusion defect with LV dilation or increased lung uptake 2
• Echocardiographic wall-motion abnormality involving more than 2 segments developing at low dose of dobutamine (≤10 mcg/kg/min) or at low heart rate (<120 bpm) 2

Intermediate-Risk Findings (1-3% annual mortality)

• Mild/moderate resting LV dysfunction (LVEF = 0.35-0.49) 2
• Intermediate-risk treadmill score (-11 to 5) 2
• Stress-induced moderate perfusion defect without LV dilation 2
• Limited stress echocardiographic ischemia with wall-motion abnormality only at higher doses of dobutamine involving ≤2 segments 2

Low-Risk Findings (<1% annual mortality)

• Low-risk treadmill score (score ≥5) 2
• Normal or small myocardial perfusion defect at rest or with stress 2
• Normal stress echocardiographic wall motion 2

Common Pitfalls to Avoid

• Ordering stress tests in asymptomatic low-risk patients without risk factors is not recommended 1
• Failing to use imaging when indicated in patients with baseline ECG abnormalities leads to decreased accuracy 1
• Performing stress tests too early in patients with acute myocardial infarction who are not clinically stable 1
• Routine preoperative stress testing in low-risk patients or those undergoing low-risk procedures is not recommended as it is costly, may delay surgery, and has not been shown to improve outcomes 2
• Failing to consider pharmacologic stress testing when patients cannot achieve adequate exercise levels can lead to inaccurate results 1