Regadenoson and exercise myocardial perfusion imaging: The courtship continues

Excerpt

American Society of Nuclear Cardiology (ASNC) guidelines support the use of low-level exercise testing for adenosine and dipyridamole in select patients to improve diagnostic accuracy and to decrease adverse side effects.1 Regadenoson does not have the same support in the current guidelines and, as with the adenosine and diypridamole, its use with exercise remains “off-label”.2 Since approval in 2008, regadenoson has become the most common vasodilator stress test agent in the United States.3 Its ease of use as a single bolus injection makes it versatile and straightforward to use. Although approved for supine testing, it has been evaluated for low-level exercise (a protocol we characterize as RegLowEx) in one randomized trial and a large observational study.4,5 Similar to adenosine and dipyridamole, the goals of RegLowEx are improved image quality and decreased vasodilator associated symptoms. Newer studies have evaluated regadenoson given just before peak exercise (which we term RegNearPeakEx), at peak (termed RegPeakEx), and just after peak exercise (termed RegPostPeakEx) for those unable to achieve 85% of maximum predicted heart rate or meet an ischemic endpoint.6-9 The primary goal of protocols that allow patients to exercise to peak is to obtain prognostic information from the exercise stress aspect of the test and use regadenoson on an provisional basis such that perfusion imaging sensitivity is not compromised due to lack of an appropriate heart rate being achieved. A proposed algorithm was described in our previous editorial on this topic.10 A randomized clinical trial of a novel protocol in which symptom limited exercise is performed and if an adequate heart rate or an ischemic endpoint is not achieved, the administration of regadenoson is delayed until three minutes post exercise during a five minute recovery period of slow walking (termed RegRecovery) is now underway.11 …