Comparison of Anti-gravity Treadmill Exercise and Regadenoson Tc-99m Tetrofosmin Single-photon Emission Computed Tomography (SPECT) Myocardial Perfusion Imaging

This randomized, single blind, controlled study will enroll up to 75 subjects presenting to the nuclear cardiology stress lab for a previously ordered SPECT study. Potential subjects will be identified by the study staff and stress lab staff prior to the stress portion of their study when the potential subject states an inability to exercise to target heart rate on the conventional treadmill prior to starting exercise. The study coordinator will then be contacted to obtain informed consent from the study subject. Subjects, after signing an informed consent document, will be enrolled and will complete the enrollment. If the subject qualifies for the study, they will then be randomized with a 2:1 ratio between the test and control arms using a preprinted randomization table.

Subjects randomized to the test arm will be instructed on the proper procedure for safely entering and exercising on the anti-gravity treadmill by the stress lab and research staff. Subjects will be provided a size-appropriate pair of neoprene shorts to be worn over their clothes. The shorts attach to the anti-gravity treadmill. These shorts will be cleaned following each patient use. Test arm subjects will exercise according to the Bruce protocol unweighted to 75% of their body weight with additional unweighting to 50% during the test if unable to reach target at 75% weight. Once these subjects have reached their target heart rate on the Bruce protocol, patients will receive the Tc-99m injection as per standard clinical protocol and maintain target heart rate for 1 minute following the injection. Patients will then be brought to walk speed for recovery.

Any subject in the test arm who is unable to reach target heart rate on the anti-gravity treadmill will be slowed to walk speed and receive regadenoson and Tc-99m injections while walking. They will be maintained at 75% unweighting while walking for these injections. Subjects unable to reach target on the anti-gravity treadmill will be included in the final data safety analysis but will be excluded from the test arm image analysis.

Subjects randomized to the control arm will proceed with the clinical standard regadenoson pharmacological stress SPECT study with adjunctive low-intensity walk on conventional treadmill during regadenoson and Tc-99m injections if tolerated. If they are unable to tolerate any treadmill exercise, they will receive regadenoson and Tc-99m injections at rest. Study patients will have stable systemic blood pressure with readings equal to or greater than 90 mmHg systolic. Other inclusion and exclusion criteria are described in detail below.

All images will be acquired by the standard clinical imaging protocol and processed by a trained nuclear medicine technologist. The imaging will then be analyzed and read by an experienced nuclear cardiologist who is blinded to whether patient is in the anti-gravity treadmill or control arm. The subsequent images and values will be confirmed by a separate and blinded experienced nuclear cardiologist. The uptake counts of isotope in the left ventricle versus the background counts will be recorded and compared between the test arm and the control arm.