Flurpiridaz F-18 is a diagnostic radiopharmaceutical, a fluorine-18 labeled molecule recently approved by the U.S. Food and Drug Administration (FDA). It is designed to assist in evaluating certain health conditions. Used in medical imaging, this radiotracer allows for visualization of biological processes within the body using specialized techniques.
Purpose in Medical Imaging
Flurpiridaz F-18 is primarily used in myocardial perfusion imaging (MPI) via Positron Emission Tomography (PET). This technique assesses blood flow to the heart muscle, indicating heart health. It helps identify areas of the heart not receiving adequate blood supply, a common issue in coronary artery disease (CAD).
CAD involves narrowed or blocked arteries that reduce blood flow to the heart, potentially leading to myocardial ischemia or heart attacks. By evaluating blood flow under both rest and stress conditions, flurpiridaz F-18 PET MPI provides detailed information on heart muscle perfusion. This diagnostic approach offers improved accuracy in detecting blood flow abnormalities compared to some traditional imaging methods. The longer half-life of flurpiridaz F-18, approximately 109 minutes, extends its availability and facilitates broader distribution compared to older PET cardiac tracers.
How it Interacts with the Body
Flurpiridaz F-18 interacts specifically with heart muscle cells. It is a structural analog of pyridaben, an inhibitor of mitochondrial complex I, an enzyme abundant in heart muscle mitochondria. After intravenous administration, flurpiridaz F-18 rapidly enters the bloodstream and is selectively taken up by the myocardium.
Tracer uptake is directly proportional to myocardial blood flow; areas with higher blood flow show greater accumulation. The fluorine-18 isotope emits positrons, which are detected by the PET scanner. These positrons travel a short distance before interacting with electrons, producing gamma rays that the scanner detects to create detailed images.
Flurpiridaz F-18 demonstrates high first-pass myocardial extraction and prolonged retention within heart muscle cells. Its high affinity for mitochondrial complex I allows for clear visualization of the myocardium with a high signal-to-background ratio. Sustained uptake in the heart, combined with rapid clearance from non-target tissues like the liver and lungs, contributes to superior image quality. Flurpiridaz F-18 acts as a diagnostic tracer without causing biochemical disturbances.
The Diagnostic Process
Patients undergoing a flurpiridaz F-18 PET scan follow a structured procedure. Before the scan, patients are advised to fast for at least three hours and avoid caffeine for at least 12 hours. They may also be instructed to withhold certain cardiac medications that might interfere with stress test results.
The procedure involves two main parts: a rest scan and a stress scan. For the rest scan, the patient lies still, and a dose of flurpiridaz F-18, typically between 2.5 to 3.0 mCi, is administered intravenously. Image acquisition begins immediately after injection and lasts for approximately 20 minutes.
Following the rest study, a stress test is performed. This can involve either exercise on a treadmill or bicycle, aiming for at least 85% of the patient’s age-predicted maximum heart rate, or a pharmacologic stress induced by a medication like regadenoson, adenosine, or dipyridamole. During the stress phase, a second, larger dose of flurpiridaz F-18, around 6.0 to 9.5 mCi, is injected. Imaging acquisition for the stress study also takes approximately 20 minutes. The overall procedure, including preparation and scanning, typically takes a few hours.
Understanding the Scan Results
The flurpiridaz F-18 PET scan produces detailed maps of heart muscle blood flow. Medical professionals interpret these images by analyzing tracer uptake patterns. Areas with normal blood flow show uniform and high uptake of flurpiridaz F-18. Conversely, regions with reduced blood flow, often due to narrowed coronary arteries, exhibit lower signal intensity or “defects.”
Comparing rest and stress images is informative. If a defect appears only during stress but not at rest, it suggests inducible ischemia, meaning the heart muscle is not receiving enough blood during increased demand. If the defect is present in both rest and stress images, it may indicate a myocardial infarction or scar tissue, where the heart muscle has been permanently damaged. The scan also allows for quantification of myocardial blood flow (MBF) and myocardial flow reserve (MFR), which measure the heart’s ability to increase blood flow in response to stress. These measurements provide insights into the severity of coronary artery disease and help guide treatment decisions.
Safety and Patient Considerations
Flurpiridaz F-18 is generally well-tolerated, and clinical trials have indicated a favorable safety profile. Common adverse reactions reported during flurpiridaz F-18 PET MPI include:
Shortness of breath
Headache
Angina pectoris
Chest pain
Fatigue
ST segment changes on an electrocardiogram
Flushing
Nausea
Abdominal pain
Dizziness
Irregular heartbeats
More serious, though less frequent, adverse reactions associated with exercise or pharmacologic stress can occur. These include myocardial infarction, severe arrhythmias, significant drops in blood pressure, bronchoconstriction, stroke, or seizures. Therefore, stress testing is performed in facilities equipped with cardiac resuscitation equipment and trained medical staff.
Patients should be aware that flurpiridaz F-18 contributes to long-term cumulative radiation exposure, which is associated with an increased risk of cancer. To minimize exposure, patients are typically advised to hydrate well before and after the scan and to void frequently. For pregnant women, the potential for adverse pregnancy outcomes due to radiation exposure should be discussed with a healthcare provider. Lactating women are usually advised to temporarily discontinue breastfeeding and pump and discard breast milk for at least eight hours after administration.