Stress test

Overview of Treatment

Stress testing is a diagnostic procedure used to evaluate cardiac function during exercise or load conditions, primarily to assess the heart's response when oxygen demand increases. This test monitors the electrophysiological activity or blood flow changes of the heart during activity, assisting physicians in diagnosing coronary artery disease, angina, or other cardiovascular issues. Stress tests can be divided into two main types: exercise stress testing and pharmacologic stress testing, selected based on the patient's physical condition.

The core of this examination is to simulate a high-load state of the heart. When the patient exercises, the heart needs to increase blood supply. If there are narrowings or blockages in the vessels, abnormal waveforms or blood flow distribution anomalies will appear on the ECG or imaging. This technique is widely used for patients suspected of heart disease, preoperative risk assessment, and monitoring treatment efficacy in cardiac patients.

Types and Mechanisms of Treatment

Stress testing mainly includes three types:

• Exercise ECG (Treadmill Test): The patient walks on a treadmill with real-time ECG monitoring
• Nuclear imaging stress test: Combines radioactive tracers with imaging techniques to observe myocardial blood flow changes
• Pharmacologic stress test: Used for patients unable to exercise, using drugs such as dobutamine or adenosine to simulate cardiac load

These methods increase myocardial oxygen consumption, causing potential issues to manifest in imaging or ECG.

The physiological mechanism involves that when coronary artery stenosis exists, exercise or drug stimulation leads to inadequate blood flow compensation in the affected myocardial regions, resulting in ischemic changes. Combining imaging techniques can precisely locate the stenosis, while ECG monitors indicators such as ST segment changes.

Indications

Stress testing is mainly suitable for:

• Patients suspected of coronary artery disease or angina
• Unexplained chest pain or dyspnea differential diagnosis
• Preoperative risk assessment for cardiac patients
• Assessment of exercise tolerance and treatment monitoring in cardiac patients

This examination is especially suitable for medium to high-risk groups, such as those with a family history of heart disease, hypertension, or diabetes.

Doctors may recommend this test to:

• Confirm whether chest pain is caused by cardiac issues
• Assess the necessity of cardiac surgery or intervention
• Develop or adjust exercise prescriptions for cardiac patients

Usage and Dosage

The exercise test process includes:

1. Initial static ECG and blood pressure measurements
2. Gradually increasing the incline and speed on the treadmill, adjusting to the patient's physical capacity
3. Real-time ECG and symptom monitoring

Pharmacologic testing uses dobutamine or adenosine, with ultrasound or SPECT imaging to observe myocardial perfusion.

Dosage control involves:

• The treadmill test usually lasts 10-15 minutes until the target heart rate is reached
• Drug doses are calculated based on body weight, with dobutamine often infused at 20-40 μg/kg/min
• If chest pain, abnormal blood pressure, or significant ST segment changes occur during the test, it must be immediately stopped

Benefits and Advantages

The main advantages of stress testing include:

• Non-invasive, no need for surgery or catheter insertion
• Allows dynamic observation of cardiac performance under stress
• When combined with imaging, can accurately locate ischemic areas
• Relatively low cost and repeatable

For patients suspected of heart disease, this test can effectively differentiate between functional impairment and non-cardiac chest pain.

Compared to invasive coronary angiography, stress testing:

• Is suitable for initial screening of low to moderate suspicion cases
• Can evaluate exercise tolerance and cardiac compensatory capacity
• Has preventive value for asymptomatic high-risk groups

Risks and Side Effects

Immediate risks may include:

• Induction of angina or arrhythmias during the test
• Pharmacologic stress may cause dizziness, tremors, or breathing difficulties
• Rare cases may trigger myocardial infarction or heart failure

This is more common in patients with severe heart disease or drug allergies.

Long-term sequelae are extremely rare, but misjudgment risks should be noted:

• Obesity may affect imaging resolution
• Left bundle branch block may interfere with ECG interpretation

Within 24 hours after the test, vigorous activity should be avoided, and any discomfort should be monitored.

Precautions and Contraindications

Contraindications include:

• Within 72 hours of acute myocardial infarction
• Severe uncontrolled hypertension (systolic BP >200 mmHg)
• Aortic aneurysm, severe valvular disease, or unstable heart failure
• Drug allergies (e.g., to adenosine or dobutamine)

Before the test, inform the doctor of:

• All medications currently used (especially beta-blockers or nitrates)
• Recent cardiac events or surgeries
• Allergy history and drug sensitivities

On the day of the test, avoid caffeine and wear comfortable clothing.

Interactions with Other Treatments

Beta-blockers may interfere with heart rate response and should be discontinued 12-24 hours before testing. Some lipid-lowering drugs (such as statins) have no direct interaction with the test but should inform the physician of all medications used.

Interactions with nuclear imaging:

• Radioactive contrast agents may interact with nephrotoxic drugs
• Diabetic patients using insulin need dose adjustments to prevent hypoglycemia

All medication adjustments should be strictly monitored by the attending physician.

Treatment Efficacy and Evidence

Large studies show that stress myocardial isotope scans have a sensitivity of 85-90% and specificity of about 75-80%, with high diagnostic value for moderate to severe coronary artery stenosis. Exercise ECG has an accuracy of about 70-80% in typical angina patients, often combined with imaging to improve precision.

The 2018 JAMA analysis indicates that stress testing can reduce unnecessary invasive procedures by 30% and decrease misdiagnosis cases by 20%. For low to moderate risk patients, this test is considered a frontline screening tool.

Alternatives

Invasive alternatives include:

• Coronary angiography: directly observes the degree of vessel stenosis
• PET (Positron Emission Tomography): provides higher-resolution blood flow perfusion images

However, these tests are more costly and invasive.

Non-invasive alternatives:

• Resting ECG: cannot simulate load conditions
• Echocardiography: can observe ventricular function dynamically but with lower spatial resolution

Stress testing remains unmatched in dynamic evaluation.

Frequently Asked Questions

Do I need to fast or adjust medications before the stress test?

It is generally recommended to avoid eating 2-4 hours before the stress test to prevent gastrointestinal discomfort during exercise. If you are taking cardiovascular medications (such as antihypertensives or cardiac drugs), consult your doctor about whether to temporarily stop or adjust the dosage. Specific instructions vary based on individual health status; follow the medical team's guidance.

What should I do if I experience chest pain or weakness during the test?

If chest pain, dizziness, or discomfort occurs during the stress test, inform the technician or doctor immediately. The test will be stopped promptly, and ECG or other assessments will be performed to ensure safety. These symptoms may be reactions to the test but also require ruling out cardiac issues; timely communication is crucial.

Can I resume normal activities on the day after the test?

Most patients can resume light daily activities immediately after the test. However, if abnormal reactions such as arrhythmias or blood pressure abnormalities occur during the test, the doctor may advise rest or limit strenuous exercise. It is recommended to avoid alcohol or excessive fatigue on the day and monitor for any changes in physical condition.

How often should follow-up be if the stress test results are abnormal?

If the results indicate cardiac ischemia or abnormalities, the doctor will schedule follow-up examinations such as coronary angiography or medication management based on severity. Mild abnormalities may require re-evaluation every 3-6 months, while severe cases need more frequent monitoring. The specific plan depends on individual risk assessment.

How do stress test results influence treatment planning?

The results help the doctor determine whether blood flow is sufficient. If ischemia is detected, medication adjustments, angioplasty, or surgery may be necessary. Combining results with clinical symptoms allows for a more precise assessment of cardiac function and the development of personalized treatment goals, such as exercise training or lifestyle modifications.