Should a 78-year-old female with a history of mechanical mitral valve replacement, atrial fibrillation, hypertension, and hyperlipidemia undergo a Lexiscan (regadenoson) stress test or a traditional exercise stress test?

Lexiscan (Regadenoson) Stress Test is Appropriate for This Patient

This 78-year-old patient with mechanical mitral valve, atrial fibrillation, and multiple cardiovascular comorbidities should proceed with the Lexiscan (regadenoson) pharmacological stress test as ordered, rather than a traditional exercise stress test. 1

Rationale for Pharmacological Stress Testing

Exercise stress testing in patients with valvular heart disease requires careful patient selection and continuous monitoring by trained operators. 1 While exercise testing can provide valuable prognostic information in patients with valve disease, pharmacological stress testing is often more appropriate when:

• The patient presents with episodic weakness and poor sleep habits, which may limit exercise capacity 1
• There is a need to evaluate coronary artery disease progression in a patient with multiple cardiovascular risk factors 1
• The patient has a mechanical valve replacement, which requires careful hemodynamic assessment 1

Safety Profile of Regadenoson

Regadenoson has been extensively studied and demonstrated to be safe and effective in patients with cardiovascular disease, including those with hypertension, history of arrhythmia, and coronary artery disease. 2 In clinical trials:

• 81% of patients had hypertension (similar to this patient) 2
• 33% had history of arrhythmia (this patient has atrial fibrillation/flutter) 2
• 41% had history of myocardial infarction 2
• The median age was 66 years, with patients ranging up to 93 years 2

Advantages Over Exercise Stress Testing

Pharmacological stress testing with regadenoson offers several advantages for this patient: 1, 2

• Standardized vasodilator response that is not dependent on patient effort or exercise capacity 2
• Shorter procedure time compared to traditional adenosine infusion (single injection vs. 6-minute infusion) 2
• Better tolerability with the ability to reverse side effects if needed 1
• More reliable results when baseline exercise capacity may be compromised by episodic weakness 1

Specific Considerations for This Patient

The patient's current medications are compatible with regadenoson stress testing, with one important caveat: 2

• Beta-blockers (metoprolol 200mg daily): In clinical trials, 18% of patients were on beta-blockers on the day of scanning 2
• Calcium channel blockers (amlodipine 2.5mg daily): 9% of patients in trials were on these medications 2
• Critical instruction: The patient must avoid all methylxanthine-containing products (caffeine, theophylline, aminophylline) for at least 12 hours before the test 2

Anticoagulation Management

The patient's warfarin therapy does not need to be interrupted for a non-invasive stress test. 1 The current anticoagulation regimen should be continued, as:

• This is a diagnostic imaging procedure without bleeding risk 1
• The patient has a mechanical mitral valve requiring continuous anticoagulation 1
• Interruption of anticoagulation would increase thromboembolic risk unnecessarily 3, 4

Monitoring Requirements During Testing

During regadenoson administration, continuous monitoring must include: 1, 2

• Continuous ECG monitoring for arrhythmias (particularly important given history of atrial fibrillation/flutter) 1, 2
• Blood pressure monitoring for hypertensive or hypotensive responses 1, 2
• Assessment for chest pain, dyspnea, or other symptoms 2
• Availability of aminophylline for reversal if needed 1

Patient Education Points

When explaining to the patient why Lexiscan is preferred over exercise stress testing, emphasize: 2

• Lexiscan provides equivalent diagnostic information to exercise testing while being more reliable when exercise capacity is uncertain 2
• The test is shorter and better tolerated than traditional adenosine infusion protocols 2
• Results are not dependent on achieving a target heart rate, which can be difficult in patients on beta-blockers 2
• The medication effect is brief (half-life of 2-3 minutes), and any side effects resolve quickly 2
• Most importantly: She must avoid all caffeine and caffeine-containing products for 12 hours before the test, as methylxanthines can block the effect of regadenoson and invalidate the study 2

Common Pitfalls to Avoid

Key considerations to prevent complications: 2

• Ensure the patient has not consumed caffeine for at least 12 hours prior to testing 2
• Have aminophylline readily available for reversal of prolonged adverse effects 1, 2
• Monitor closely for arrhythmias given her history of atrial fibrillation/flutter 2
• Do not discontinue anticoagulation for this non-invasive procedure 1, 3

The ordered Lexiscan stress test is the appropriate choice and should proceed as planned, with proper patient preparation including caffeine avoidance. 2