Anti-gravity Treadmill Exercise in Stress 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.

Inclusion Criteria:

1. Patients >18 years of age who are able to ambulate.

2. Women will either have a negative pregnancy test, be post-menopausal or have prior
surgical infertility

3. Nuclear stress SPECT imaging test ordered as exercise SPECT or regadenoson SPECT.

4. If ordered for exercise SPECT, self-admission of inability to exercise on
conventional treadmill. This typically includes subjects unable to exercise due to
obesity, musculoskeletal disease, peripheral vascular disease, weakness or
debilitation.

5. Patients that initially start conventional treadmill exercise protocol and have to
stop due to exercise-limiting symptoms including musculoskeletal pain and fatigue.

6. Hemodynamically stable patients as defined by mean blood pressure (BP) >75 mm Hg and
heart rate (HR) 60-120 beats per minute.

Exclusion Criteria:

1. Hemodynamically unstable patients as defined by resting mean BP <75 and HR <60 or
>120.

2. Patients with acute coronary syndrome as defined by troponin elevation (>0.05) within
the past 72 hours.

3. Patients at high clinical risk related to severe aortic stenosis, known
exercise-induced ventricular tachycardia or fibrillation, or advanced (second-degree
type II or third-degree) heart block.

4. Patients with left bundle branch block or paced cardiac rhythm (in whom exercise is
associated with non-ischemic perfusion abnormalities).

5. Patients unable to provide consent or unable to cooperate.

6. Inability to physically enter onto the anti-gravity treadmill unit.

7. Pregnant women.

8. Patients with a contraindication to receive regadenoson (sinus node dysfunction,
high-degree heart block, active wheezing/reactive airway disease).

9. At risk patient populations (prisoners or severely mentally handicapped).