Coronary artery disease is a major cause of morbidity and mortality in the United States.
Currently, the presence of physiologically significant coronary disease is most commonly
diagnosed using non-invasive imaging tests such as a nuclear stress test or an echo stress
test. Unfortunately, nuclear stress tests require the use of ionizing radiation and have a
limited spatial resolution. On the other hand, echo stress tests are dependent of adequate
imaging windows. Adenosine stress testing combined with cardiac magnetic resonance (CMR) is a
rapidly evolving technique for diagnosing significant coronary disease. It does not use
ionizing radiation and has excellent image quality. In a recent meta-analysis of 14 studies
with a total of 1,183 patients, the sensitivity and specificity of stress CMR for detecting
significant coronary disease was 91% and 81%. Additionally, 2 studies have shown that
patients with a normal stress CMR study have a <1% risk of having a cardiovascular event
during the ensuing year. Another important advantage to stress CMR is the ability to fully
quantify myocardial blood flow which may improve the diagnostic accuracy of stress CMR. In
addition to perfusion imaging, CMR can directly visualize the coronary arteries, detect
extremely small myocardial infarctions, and precisely measure the left ventricular function.
Although adenosine stress CMR is a rapidly maturing test, several important challenges exist.
First, many patients find it difficult to tolerate the common side effects of adenosine in
the confined space of the MRI scanner. Secondly, many patients under the influence of
adenosine and its side effects cannot adequately hold their breath during image acquisition
making image interpretation more difficult and quantitative analysis very time consuming.
Finally, because adenosine must be continuously infused during a contrast-enhanced stress
CMR, 2 separate intravenous (I.V.) catheters are needed. Most of the undesirable effects of
adenosine are mediated through the adenosine A(2B) and A(3) receptors; where as, its desired
vasodilator effects are mediated through the A(2A) receptor. The FDA recently approved an
adenosine A(2A) receptor specific stress testing agent called regadenoson which is
administered as a 10 second bolus and has an improved side effect and safety profile when
compared to adenosine. With its improved tolerability and ease of use, regadenoson is a more
ideal stress testing agent to use with CMR.
The purpose of this study is to determine whether a comprehensive regadenoson stress cardiac
magnetic resonance study which includes myocardial perfusion imaging, optimized coronary
imaging, and myocardial scar imaging provides incremental prognostic information over a
clinical evaluation that includes nuclear stress testing.
