What does a cardiac stress test evaluate for?

Cardiac Stress Test Evaluation

A cardiac stress test primarily evaluates for the presence, extent, and severity of coronary artery disease by assessing myocardial perfusion, ventricular function, and hemodynamic responses under conditions of increased cardiac workload. 1

Primary Evaluations

• Coronary Artery Disease Detection: Stress tests identify areas of reduced coronary blood flow by revealing perfusion defects or wall motion abnormalities that occur when blood supply cannot meet increased myocardial oxygen demand during stress 1
• Myocardial Perfusion: Radionuclide tracers are taken up by the myocardium in proportion to coronary blood flow, allowing visualization of hypoperfused or ischemic areas 1
• Regional and Global Ventricular Function: Assessment of wall motion abnormalities and changes in ejection fraction during stress can indicate ischemia or viability 1
• Hemodynamic Responses: Evaluation of blood pressure, heart rate, and cardiac output responses to increased workload 1

Types of Stressors

Exercise Stress

• Preferred Method: Exercise is the test of choice when feasible as it provides physiological cardiovascular responses and functional capacity assessment 1
• Methods: Treadmill or bicycle ergometer protocols 1
• Advantages: Preserves electro-mechanical response integrity and provides valuable information about functional status 1

Pharmacological Stress

• Vasodilators (dipyridamole, adenosine, regadenoson):

  • Cause maximal coronary arteriolar vasodilation 1
  • Create "steal phenomenon" where blood is directed away from territories supplied by obstructed arteries 1
  • Evaluate coronary flow reserve 1, 2

• Adrenergic Agents (dobutamine):

  • Increase heart rate and contractility 1
  • Evaluate contractile reserve and viability 1
  • Useful for patients unable to exercise 1

Additional Parameters Assessed

• Diastolic Function: Exercise stress echocardiography can detect impaired LV diastolic function reserve and increased filling pressures 1
• Valvular Function: Changes in transvalvular gradients and regurgitation during stress 1
• Pulmonary Artery Pressure: Elevation during exercise may indicate pulmonary hypertension 1
• Myocardial Viability: Low-dose dobutamine can identify viable but dysfunctional myocardium 3
• Functional Capacity: Exercise duration, workload achieved, and symptoms during stress 4

Clinical Significance

• Diagnostic Value: Identifies ischemia in patients with intermediate probability of coronary artery disease 1, 3
• Prognostic Information: Provides risk stratification for future cardiac events 5, 6
• Treatment Guidance: Helps determine need for cardiac catheterization, revascularization, or medical therapy 1
• Post-Intervention Assessment: Evaluates efficacy of medical treatment or revascularization 1

Common Contraindications

• Absolute: Acute coronary syndrome, high-risk unstable angina, decompensated heart failure, severe aortic stenosis, uncontrolled arrhythmias, severe hypertension (≥200/110 mmHg), acute aortic dissection, acute pericarditis/myocarditis 7
• Relative: Specific contraindications exist for different stress modalities (dobutamine, vasodilators) based on patient characteristics 7

Key Considerations

• The ischemic cascade during stress testing includes sequential abnormalities: perfusion defects, myocardial stiffening, wall motion abnormalities, ECG changes, and chest pain 1
• Stress imaging (echocardiography or nuclear) provides greater diagnostic accuracy than exercise ECG alone, especially in patients with baseline ECG abnormalities 1, 6
• The choice of stress modality should be based on patient characteristics, local expertise, and specific diagnostic questions 1, 4