Regadenoson with low-level exercise reduces side effects
In a routine clinical setting, the pharmacologic stress agent regadenoson with and without low-level treadmill exercise is safe and well tolerated. Those patients who exercised had fewer side effects and a drop in blood pressure, according to a study published online April 23 in the Journal of Nuclear Cardiology.

Regadenoson (Lexiscan) is a pharmacologic stress agent, which was recently approved for stress myocardial perfusion imaging (MPI).

Deborah H. Kwon, MD, and colleagues from the Cleveland Clinic evaluated 1263 patients who underwent regadenoson stress testing (596 with low-level treadmill exercise, 667 supine) between July 1, 2008 and Dec. 4, 2008,

They found that low-level treadmill testing was well tolerated in the patient population. Shortness of breath, dizziness, palpitations, transient heart block and nausea were less frequent when patients were able to exercise. Patients referred to low-level exercise, however, had fewer co-morbidities than those not referred.

"A prospectively designed trial which randomizes patients into the low-level treadmill versus supine regadenoson MPI would help to distinguish if exercise alone helps to diminish the side effects," the authors wrote.

In the study, 51 percent of patients experienced a drop in systolic blood pressure greater than 10 mmHg, with 9 percent experiencing a decrease in more than 30 mmHg. This decrease in blood pressure was more common in patients who underwent low-level treadmill testing versus those that were supine (56 percent vs. 47 percent). The difference was significant.

The frequency of symptoms was as follows: chest pain: 35 percent, dizziness/lightheadedness: 16 percent, shortness of breath: 27 percent, headache: 1.4 percent, nausea: 2.3 percent and palpitations: 5 percent. Researchers found no major hemodynamic or conduction abnormalities. Additionally, in the 16 percent of patients with a history of chronic obstructive pulmonary disease or asthma, regadenoson MPI was well tolerated.

"Adenosine-induced bronchoconstriction is an important limitation [of using adenosine] because as many as 30 percent of patients referred for adenosine MPI also carry the diagnosis of COPD and knowledge of broncho-reactivity to adenosine is often not known prior to adenosine administration," the authors wrote.

According to the study, regadenoson was administered as a single 400-µg peripheral IV rapid infusion over 10 seconds followed immediately by a 5-mL saline solution flush. Technetium 99m tracer (tetrofosmin) was injected approximately 30 seconds after starting regadenoson.