Leg-muscle perfusion reserve on 99mTc-MIBI stress-rest scintigraphy: the novel use of radionuclide imaging in assessing lower extremity functional capacity

AIM: To evaluate the utility of lower extremity 99mTc-MIBI imaging as a noninvasive correlate to lower extremity functional capacity. MATERIALS AND METHODS: Patients referred for stress myocardial perfusion imaging with no known history of peripheral artery disease (PAD) were included in the study. 99mTc-MIBI perfusion scintigraphy was performed for calf muscles at stress and rest. Perfusion reserve (PR) for bilateral calves was calculated as: (average stress counts-average rest counts)/average rest counts × 100. Correlation of PR was assessed for functional/exercise capacity [metabolic equivalents (METs) and exercise duration]. RESULTS: Eighty-six patients (70 male and 16 female) with a median age of 53.5 (range 28-77) years were included in the study. The mean PR for calf muscles was 62.9 ± 37.9%. There was a significant correlation between the functional capacity of the patients (METs achieved and exercise duration) and PR of bilateral calf muscles. CONCLUSION: Radionuclide imaging with 99 m-Tc MIBI allows noninvasive assessment of changes in both macrovascular and microvascular perfusion under dynamic exercise. Thus, it may serve as an ideal noninvasive imaging to provide insight into physiological adaptations as well as to detect the macrovascular and microvascular perfusion disturbances in PAD and skeletal muscle adaptation in response to exercise therapy commonly prescribed for PAD or other novel therapies.