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.
