Myocardial Blood Flow by PET and N-13 Ammonia During Regadenoson vs Adenosine Stress

Overview

Blockage of the heart arteries (coronary artery disease) can lead to angina (chest pain), heart attacks, heart failure, and/or death. Positron emission tomography (PET) stress myocardial perfusion imaging (MPI) is a powerful tool to help identify blockages in the coronary arteries. During the PET MPI test, a drug is given to mimic the effects of exercise on the heart. The study was done to measure blood flow to the heart using two similar drugs approved to mimic the effects of exercise on the heart in people during a heart stress test. The first drug, called adenosine, has been approved for this use for several decades. The second drug, called regadenoson, was approved in 2008. The investigators were looking at whether the increase in blood flow to the heart with the newer drug (regadenoson) was similar to the increase in blood flow with the older drug (adenosine). This information is important for the use of these drugs in patients and for interpreting the blood flow values.

The hypothesis for this study was that Regadenoson will produce a very similar degree of maximal hyperemia (increased blood flow) as adenosine, the other vasodilator agent. There were only 2 days on study for each subject. On Day 1 of the study, subjects were interviewed and had a physical exam, including a resting 12-lead electrocardiogram (ECG) to exclude evidence of silent ischemia or myocardial infarction, and other cardiovascular disorders. Subjects were instructed to have a light meal at least 4 hours prior to the PET MPI. Subjects were instructed to abstain from caffeine-containing products for 24 hours prior to the PET scan. Day 1 of the study occurred less than or equal to 4 weeks of Day 2. On Day 2 of the study, each subject underwent three PET N-13 ammonia (10-20 mCi) dynamic emission acquisitions: resting, regadenoson (0.4 mg/5 mL IV), and adenosine (140 microgram/kg/min; order of regadenoson vs adenosine was randomized according to subject's birth year), and three transmission acquisitions for attenuation correction. Each emission acquisition was separated by 50 min to allow for radioactive decay. At the end of the drug infusions, subjects were monitored for 5-30 min. Based on the known short biological half-lives of these stress agents, the pharmacologic effects of each drug should have dissipated by the time the next drug was administered.