Feasibility of low-level treadmill exercise during adenosine stress in an outpatient office laboratory

Abstract

Background: In patients referred for adenosine stress myocardial perfusion imaging, low-level treadmill exercise (LLTE) has been shown to reduce adenosine-related side effects and improve image quality. However, the feasibility of using LLTE during adenosine stress has not been well defined. Methods: We retrospectively reviewed the records of all patients referred to our outpatient office laboratory for adenosine stress myocardial perfusion imaging from January through December of 2003. Results: 1038 consecutive patients were referred for adenosine stress myocardial perfusion imaging. The most common contraindication to LLTE was the presence of a right ventricular pacemaker/defibrillator (n=210; 20% of patients). Left bundle branch block (LBBB) was a less frequent contraindication (n=68; 6.6% of patients). Among the remaining 760 patients without ventricular pacemakers or LBBB who were eligible for LLTE, 100 patients (13%) were unwilling or unable to perform LLTE. Arm exercise was substituted for LLTE in 66 patients (8.7% of eligible patients) and 34 patients (4.5% of eligible patients) performed no exercise during adenosine infusion. The remaining 660 patients (87% of eligible patients) performed LLTE (1 mph, 0% incline) during the 4-minute adenosine infusion (140 mcg/kg/min). Conclusion: The majority of patients referred to our outpatient office laboratory for adenosine stress myocardial perfusion imaging were willing and able to perform LLTE (660 of1038; 64%). Only 13% of eligible patients were unwilling or unable to perform LLTE, and most of these patients were able to perform arm exercise. The most common contraindication to LLTE was the presence of a right ventricular pacemaker/defibrillator. As clinical indications for device therapy continue to expand, ventricular pacemaker/defibrillators will likely prove to be an increasingly common obstacle to the widespread application of LLTE during adenosine stress.