Advanced hybrid stress testing: a potential new paradigm combining exercise and pharmacologic stress.

Partington et al at the Brigham & Women’s Hospital present a landmark article on the use of pharmacological stress at near peak exercise in this issue of the Journal. The article represents the first in a likely series of articles by these and other investigators exploring the use of selective A2 agents injected as a bolus at near-peak exercise, or during recovery, in patients undergoing maximal exercise testing with myocardial perfusion imaging (MPI) who do not achieve the accepted 85% maximum heart rate standard. ‘‘Hybrid stress testing,’’ the combination of exercise and vasodilation pharmacologic stress with dipyridamole, adenosine, or regadenoson, improves patient tolerance and image quality compared to pharmacologic stress without exercise. While off label, supplemental exercise during dipyridamole and adenosine stress is recommended by ASNC. As almost all patients can undergo either exercise or pharmacologic stress, the development of pharmacologic stress has allowed MPI to become the most commonly performed test in the US for the evaluation of ischemia. Pharmacologic stress testing continues to increase in the US, representing 51% of MPI studies in 2010 and 55% in 2011. A substantial percentage, though the minority, of these studies are performed in a hybrid fashion with low level exercise combined with pharmacological stress. Partington and colleagues seized upon the specific advantages of regadenoson (bolus administration over 10 seconds and one dose for all patients) to evaluate maximal vasodilation stress with regadenoson injected at near-peak exercise in 211 relatively low-risk patients who could not achieve [85% of maximum heart rate (220 age). Beginning with 2,237 patients undergoing MPI and able to exercise in their observational trial, 1,522 (68%) achieved [85% of maximum heart rate and, therefore, did not require regadenoson. The remaining 715 patients received either (a) radiotracer despite a heart rate \85% maximum (ETT-Submax, n = 504, 23%) or (b) a novel protocol of regadenoson injected 1 minute prior to exercise termination, with radiotracer (Tc-99 sestamibi) injected 30 seconds following regadenoson (n = 211, 9%). They labeled this new test ‘‘ETT-Reg.’’ Patients who underwent regadenoson stress MPI while supine (SupineReg, n = 239) during the same time period served as another comparison group. Patients who had ischemic ECG changes or symptoms of ischemia during exercise stress received radiotracer when this occurred so were part of the ETTSubmax group. Patients were excluded from the ETT-Reg group a priori if, prior to the initiation of stress testing, they had (a) undergone past coronary revascularization, (b) a Q wave myocardial infarction on their resting ECG, (c) known CAD and were being evaluated for ischemia at the workload achieved, even if exercise was submaximal, (d) CAD and were undergoing MPI for symptoms suggestive of ischemia. The decision to exclude patients from ETT-Reg during the test included the clinician’s belief that adding regadenoson to maximal exercise, albeit submaximal by heart rate, was unsafe in a particular patient based on signs or symptoms exhibited during exercise. Such exclusions resulted in the ETT-Reg group patients comprising a low-risk group compared to the comparison groups. Acknowledging this, the investigators found ETT-Reg to be feasible, safe, and significantly better tolerated than regadenoson administered From the MemorialCare Heart & Vascular Center, Long Beach Memorial Medical Center and Miller Children’s Hospital of Long Beach, Long Beach, CA; and Division of Cardiology, University of California, Irvine, Irvine, CA. Reprint requests: Gregory S. Thomas, MD, MPH, FACC, FASNC, MemorialCare Heart & Vascular Center, Long Beach Memorial Medical Center and Miller Children’s Hospital of Long Beach, 2801 Atlantic Ave, Long Beach, CA 90806; gthomas1@memorialcare.org. J Nucl Cardiol 2012;19:887–90. 1071-3581/$34.00 Copyright 2012 American Society of Nuclear Cardiology. doi:10.1007/s12350-012-9614-x