What is the purpose and procedure of a Lexiscan (regadenoson) scan stress test?

Lexiscan (Regadenoson) Scan Stress Test: Purpose and Procedure

A Lexiscan (regadenoson) scan stress test is a pharmacologic stress test using regadenoson as a vasodilator to assess myocardial perfusion in patients who are unable to perform adequate exercise stress testing. 1

Purpose

• Lexiscan is specifically indicated for radionuclide myocardial perfusion imaging (MPI) to detect coronary artery disease in patients who cannot achieve adequate exercise stress 1
• It serves as an alternative to exercise stress testing for patients with physical limitations, providing diagnostic and prognostic information about myocardial ischemia 2
• Particularly useful for patients with abnormalities on resting ECG that impair diagnostic interpretation (e.g., left bundle-branch block, LV hypertrophy with "strain" pattern, digitalis effect) 2
• Regadenoson has a more favorable side-effect profile compared to other vasodilators (adenosine, dipyridamole), making it safer for use in patients with bronchospasm 2

Patient Selection

• Appropriate for patients unable to exercise adequately due to physical limitations 1
• Particularly valuable for patients who cannot achieve age-predicted target heart rate or 5 METs during exercise testing 1
• Preferred over exercise MPI in patients with left bundle-branch block due to higher specificity 2
• Can be used in patients with pulmonary hypertension, though careful monitoring is required 3
• Generally well-tolerated in special populations including those with end-stage liver disease 4

Procedure

1. Pre-test preparation:

   • Patient must avoid consumption of methylxanthines (caffeine, tea, coffee, theophylline, aminophylline) for at least 12 hours before the test 1
   • Baseline vital signs and ECG are obtained 1, 5

2. Administration:

   • Regadenoson is administered as a single fixed-dose of 0.4 mg via intravenous injection 1
   • No need for weight-based dosing, making administration simpler than with other vasodilators 1, 6

3. Imaging:

   • Radionuclide tracer (typically 99mTc-sestamibi) is injected shortly after regadenoson administration 1
   • SPECT (Single Photon Emission Computed Tomography) imaging is performed 60-90 minutes after regadenoson administration 1
   • Images are evaluated for perfusion defects that may indicate coronary artery disease 2, 1

4. Monitoring:

   • Continuous ECG monitoring and frequent vital sign measurements are performed 1, 5
   • Patients typically experience an increase in heart rate and a slight decrease in blood pressure 6, 5
   • Most side effects begin soon after administration and resolve within approximately 15 minutes 6

Hemodynamic Effects

• Causes rapid increase in coronary blood flow, which is sustained for a short duration 6
• Typically increases heart rate by 16-23 beats per minute 6, 4
• May cause slight decreases in systolic and diastolic blood pressure 6, 4
• Hemodynamic effects may be blunted in patients with high BMI (≥30 kg/m²) and diabetes 5

Contraindications

• Acute coronary syndrome or high-risk unstable angina 7
• Decompensated heart failure 7
• Significant heart block without permanent pacemaker 7
• Severe systemic arterial hypertension (≥200/110 mmHg) 7
• Significant hypotension (SBP <90 mmHg) 7

Common Side Effects

• Dyspnea (shortness of breath) - most common side effect (70.6% in patients with pulmonary hypertension) 3
• Chest discomfort 5
• Headache 5
• Flushing 6
• Gastrointestinal symptoms 6

Safety Profile

• No serious events such as death, myocardial infarction, ventricular tachycardia, or ventricular fibrillation reported in multiple studies 3, 5
• Well-tolerated in patients with end-stage liver disease 4
• Safe for use in patients with pulmonary hypertension 3
• Appears safe for use in cardiac MRI settings as well as nuclear imaging 5

Interpretation and Clinical Value

• Normal or mildly abnormal results on myocardial perfusion imaging indicate an annual risk for cardiac death and acute MI less than 1% 2
• Moderate to severe abnormalities (multivessel perfusion defects) predict an annual risk for cardiovascular death or MI rates of 5% or higher 2
• The negative predictive value of pharmacologic stress perfusion imaging is high, typically 90-100% 2
• The annualized event rate for patients with a normal pharmacologic stress result is approximately double that of patients with a normal exercise stress result 2