1. Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology
Feasibility and safety of exercise stress testing using an anti-gravity treadmill with Tc-99m tetrofosmin single-photon emission computed tomography (SPECT) myocardial perfusion imaging: A pilot non-randomized controlled study
Patrick Daly, MD*, Regina Kayse, MD*, Steven Rudick, MD*,
Nathan Robbins, MS*, Jennifer Scheler MD#, David Harris, MD*,
Robert O’Donnell, MD*, Alok K Dwivedi PhD^, Myron C. Gerson, MD*.
Division of Cardiovascular Health and Disease, Department of Internal Medicine, and Division of Nuclear Medicine*, Department of Radiology#, University of Cincinnati Medical Center, Cincinnati, Ohio , Division of Biostatistics & Epidemiology, Department of Biomedical Sciences^ ,Texas Tech University Health Sciences Center, El Paso, Texas
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2. Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology
BACKGROUND
1-Exercise is the AHA/ACC guideline-recommended stress modality for myocardial perfusion imaging, but many patients are unable to exercise to target heart rate on a conventional treadmill 2- .We examined the feasibility and safety of stress imaging using an anti-gravity treadmill in patients with perceived poor exercise capacity.
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3. Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology
METHODS
Study type:
Pilot non-randomized controlled study
Study subjects: Included patients had an inability to exercise on the conventional treadmill due to a disabling comorbidity or less than moderate physical functioning; non-ambulatory patients were excluded.
Study endpoints:
Primary end point(s): Assess safety of anti-gravity exercise in patients undergoing cardiac stress testing
Secondary end point(s): Compare myocardial image quality following anti-gravity stress and pharmacologic stress
Study variables
Table 1
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4. Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology
RESULTS
Variables
Pharmacologic
Anti-gravity
p-value
Mean(SD)
Age(years)
61.2(8.3)
59.3(9.1)
0.46
Height (inches)
67(4.1)
67.3(3.9)
0.81
Weight (pound)
210.8(43.8)
202.4(52.9)
0.56
Body mass index
32.9(5.8)
31.4(8.2)
0.49
Time on treadmill (seconds)
------
455.2(169.5)
Resting heart rate
74.4(11.9)
79.3(15.1)
0.22
Peak systolic BP
134.2(24.2)
164.3(23.7)
0.0001
Peak diastolic BP
73.9(11.2)
81.9(13.9)
0.0372
Rest systolic BP
144.7(19.8)
144.4(18.8)
0.97
Rest diastolic BP
76.9(10.4)
80.9(11.7)
Peak heart rate
120.5(14)
134.9(17.9)
0.0042
Peak double product
16,296.1( )
22,334.5(5,034.4)
Pre-stress EF (%)
54.1(16.2)
55.4(12.7)
0.88
Pre-stress EDV (ml)
116.3(28.4)
117.6(63.1)
0.23
Pre-stress ESV (ml)
56.5(34.3)
57.9(56.1)
0.35
Post-stress EF (%)
55.5(14.6)
56.1(13.2)
0.93
Post-stress EDV (ml)
122.5(31.1)
115.2(60.8)
0.05
Post-stress ESV (ml)
57.8(36)
57(57.2)
0.29
N (%)
Gender-female
11(55)
13(44.8)
0.57
Race-black
5(29.4)
17(58.6)
0.07
Indication
0.008
Coronary disease
1(5)
0(0)
0.41
Chest pain
7(35)
19(65.5)
0.046
Short of breath
9(45)
2(6.9)
0.004
Other
1.00
Pre-operative
2(10)
6(20.7)
0.45
Calcium blocker use
5(25)
0.74
Beta blocker use
6(30)
15(51.7)
0.15
Anti-anginal drugs held for 48 hours
11 (55)
27 (69)
0.25
Abnormal scan
8(27.6)
0.24
Table 1: Comparison of factors between control and test groups
EF: ejection fraction; EDV: end diastolic volume; ESV: end systolic volume; BP: blood pressure; SD: standard deviation
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5. Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology
RESULTS
Of the 49 study patients, 29 walked on the anti-gravity treadmill and 20 received regadenoson stress. Seventeen of the anti-gravity patients (59%, 95%CI: 39%-76%) reached target heart rate possibly obviating the need for pharmacologic stress. Mean exercise level on the anti-gravity treadmill was to Bruce stage 3 with duration 7 minutes and 36 seconds. Five of the anti-gravity test patients reached target with 25% unweighting and 12 with 50% unweighting. Only minor adverse effects were noted, limited to transient musculoskeletal discomfort in 5 patients who exercised on the anti-gravity treadmill. There was no significant difference (p=NS) in image quality between patients who exercised on the anti-gravity treadmill (4.30 ± SD 0.87) versus controls who received pharmacologic stress (4.28 ± SD 0.66). On multivariable analysis higher resting heart rate was the only predictor of achieving at least 85% of maximum predicted heart rate on the anti-gravity treadmill (odds ratio 1.16, 95% CI: , p = 0.014).
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6. Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology
CONCLUSIONS
1- Patients with self-perceived inability to walk effectively on a conventional treadmill, who are referred for diagnostic SPECT MPI, can safely exercise, often to target heart rate, on an anti-gravity treadmill.
2- Further study is indicated to directly compare the effectiveness of anti-gravity stress testing to exercise on a conventional treadmill as an adjunctive approach to stress MPI in patients with limited exercise capacity.
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