Regadenoson — Overview of Applications in Cardiology

Coronary artery disease is a leading cause of morbidity and mortality in developed countries. According to a Center for Disease Control report, one out of four deaths is attributed to coronary artery disease. It costs the United States human lives, produc‐ tivity, and more than 100 billion dollars each year. Due to increased incidence in both men and women and all ethnicities, risk stratification of patients at risk for developing myocardial infarction and death is of paramount importance. Various tests are available for diagnosis and prognosis in coronary heart disease such as exercise treadmill testing, coronary calcium scoring, dobutamine stress echocardiography, exercise, dipyridamole, adenosine or dobutamine stress nuclear myocardial perfusion imaging (MPI), and dobutamine or adenosine stress cardiac magnetic resonance imaging. Since 2008 a new vasodilator, regadenoson (REG), has become available and is now widely used for nuclear perfusion imaging. Pharmacologic stress testing challenges the coronary flow reserve to evaluate the hyperemic capacity of the heart, which can be impaired in significant epicardial stenosis or microvascular dysfunction. In the presence of either of these conditions, ischemia induced by hyperemia manifests as wall motion abnormalities on echocardiography or as perfusion defects in nuclear perfusion imaging. REG is a selective adenosine A2A receptor agonist, and due to its targeted coronary vasodilator properties and bolus administration of a standard dose in all patients, it has rapidly gained popularity as the preferred MPI stress agent. In this chapter we will review the basis of pharmacologic vasodilator stress imaging starting with a brief discussion of the various adenosine receptors and their function, the structure and mechanism of action of REG, and its development and approval. It will be compared with other myocardial perfusion pharmacologic stress agents like adenosine and © 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. dipyridamole in terms of safety, efficacy, and side effect profile. We will also address the utility of REG in special situations like renal disease, chronic obstructive pulmo‐ nary disease, heart transplant, left bundle branch block, and paced rhythms. The prognostic value of REG MPI in the general population, its effectiveness with and without exercise, and the emerging applications of REG in other modalities of imaging such as positron emission tomography and stress echocardiography will be discussed.