What are the absolute contraindications for myocardial perfusion imaging (MPI)?

Absolute Contraindications for Myocardial Perfusion Imaging

The absolute contraindications for myocardial perfusion imaging (MPI) include high-risk unstable angina, active acute coronary syndrome (ACS) or acute myocardial infarction (AMI) within 2 days, significant arrhythmias, and significant hypotension (systolic blood pressure <90 mmHg). 1

Primary Contraindications

Cardiac-Related Contraindications

• High-risk unstable angina, complicated ACS or AMI within 2 days (active ACS) 1
• Significant arrhythmias (e.g., ventricular tachycardia, second- or third-degree atrioventricular block) 1
• Significant hypotension (systolic blood pressure <90 mmHg) 1
• Uncontrolled heart failure 1
• Sinus bradycardia <45 bpm 1

Vasodilator-Specific Contraindications

• Contraindications to vasodilator administration (when using pharmacologic stress with adenosine, dipyridamole, or regadenoson) 1
• Known or suspected bronchoconstrictive or bronchospastic disease (particularly important for adenosine or dipyridamole stress) 1
• Use of dipyridamole or methylxanthines (e.g., aminophylline, caffeine) within 12 hours before the test 1

Serious Adverse Events

While not strictly contraindications, awareness of potential serious adverse events is critical when considering MPI:

• Cardiac death, fatal and non-fatal myocardial infarction 2
• Ventricular fibrillation, symptomatic ventricular tachycardia 2
• Stroke, transient cerebral ischemia 2
• Seizures, anaphylactoid reactions, and bronchospasm 2
• Asystole, sinus node arrest, sinus node depression, and conduction block 2

Special Considerations

Patient-Specific Risk Factors

• Patients with abnormalities of cardiac impulse formation/conduction or severe coronary artery disease may be at increased risk for adverse events 2
• Patients with a history of unstable angina may be at greater risk for severe myocardial ischemia 2
• Patients with a history of asthma may be at greater risk for bronchospasm during dipyridamole injection 2

Radiation Considerations

• While not an absolute contraindication, radiation exposure should be considered, especially in younger patients or those requiring repeated imaging 1
• Radiation exposure varies by tracer: 10 mSv for tetrofosmin, 12 mSv for MIBI, and 18 mSv for thallium-201 1

Safety Precautions

When performing MPI with pharmacologic stress agents:

• Parenteral aminophylline should be readily available for relieving adverse events such as bronchospasm or chest pain 2
• Vital signs should be monitored during and for 10-15 minutes following intravenous infusion of dipyridamole 2
• An electrocardiographic tracing should be obtained using at least one chest lead 2
• For severe hypotension, place the patient in a supine position with the head tilted down if necessary, before administration of parenteral aminophylline 2

Clinical Implications

Understanding these contraindications is essential for patient safety, as MPI is otherwise considered a relatively safe procedure with a complication rate of approximately 0.01% deaths and 0.02% morbidity 1. When absolute contraindications are present, alternative imaging modalities such as stress echocardiography or cardiovascular magnetic resonance imaging may be considered based on local expertise and availability 1.