What is the protocol for a stress MRI?

Stress MRI Protocol

Stress MRI is most commonly performed using pharmacological stress rather than exercise stress due to logistical reasons, with vasodilator agents like regadenoson being preferred for their ease of administration and diagnostic accuracy. 1

Pharmacological Stress Agents

Preferred Agents

• Regadenoson: Single 10-second infusion, allowing providers to maintain distance from patients. This is the preferred agent when available and not contraindicated 1, 2
• Adenosine: Requires continuous infusion (0.14 mg/kg/min for 6 minutes) 2
• Dipyridamole: Alternative vasodilator option 1, 3
• Dobutamine: Used when vasodilators are contraindicated; administered in increasing doses from 5-10 μg/kg/min up to 50 μg/kg/min 1

Considerations for Agent Selection

• Vasodilators may cause a drop in blood pressure of approximately 10 mmHg (use caution in hypotensive patients) 1
• Dobutamine may cause hypotension at lower doses and hypertension at higher doses 1
• For patients unable to exercise, pharmacological stress is the standard approach 1

Protocol Components

1. Patient Preparation

• Obtain informed consent
• Screen for contraindications to MRI and stress agents
• Ensure patient has fasted appropriately if using vasodilators
• Place IV access for contrast and stress agent administration
• Apply ECG leads for cardiac monitoring during the procedure

2. Image Acquisition Sequence

• Rest images: Obtain baseline cardiac function and perfusion images
• Stress agent administration: Administer pharmacological stress agent
• Stress perfusion imaging: Acquire images during peak stress effect (immediately after regadenoson or during adenosine/dipyridamole infusion) 2
• Rest perfusion imaging: Typically performed 15 minutes after stress imaging 4
• Late gadolinium enhancement (LGE): Acquired 10-15 minutes after contrast administration to assess for myocardial scarring 3

3. Image Analysis

• Compare rest and stress images for perfusion defects
• Assess wall motion abnormalities that develop or worsen with stress
• Evaluate for LGE indicating prior myocardial infarction
• Quantify global and regional cardiac function (ejection fraction, wall motion)
• Consider strain measurements for additional prognostic information 3

Reporting Requirements

The stress MRI report should include 1:

1. Demographics: Patient information and referring physician
2. Clinical indication: Reason for the study, cardiac history, symptoms
3. Stress protocol: Agent used, dose, duration, and any adverse reactions
4. Findings:
   • Perfusion defects (location, extent, reversibility)
   • Wall motion abnormalities
   • Left ventricular function (rest and stress)
   • Presence of myocardial scarring
   • Other cardiac or incidental findings
5. Interpretation: Clinical significance of findings and correlation with patient's presentation

Special Considerations

• Safety monitoring: Continuous ECG, blood pressure, and oxygen saturation monitoring during stress
• Contraindications: Unstable angina, recent MI, high-grade AV block, severe bronchospasm (for adenosine/regadenoson)
• Exercise stress MRI: While less common due to logistical challenges, can be performed using supine bicycle ergometry in specific populations 4
• Prognostic value: Stress MRI provides superior diagnostic performance compared to conventional exercise ECG and can be comparable or superior to nuclear imaging techniques 1, 5

Advantages of Stress MRI

• Superior diagnostic performance for detecting obstructive coronary disease 1
• Ability to quantify and localize areas of ischemia 1
• No radiation exposure unlike nuclear imaging techniques 5
• Provides comprehensive assessment of cardiac function, perfusion, and viability in a single examination 5
• Particularly valuable in patients with challenging imaging characteristics (women, prior revascularization, LV dysfunction) 5

Stress MRI with vasodilator agents has shown excellent prognostic value, with normal results associated with very low annual risk of cardiac events (<1% per year) 6, 3.