Abstract
BackgroundAlthough exercise is often prescribed for the management of cardiovascular diseases, a non-invasive imaging approach that quantifies skeletal muscle physiology and correlates with patients’ functional capacity and cardiovascular fitness has been absent. Therefore, we evaluated the potential of lower extremity single photon emission computed tomography (SPECT)/CT perfusion imaging as a non-invasive correlate to exercise tolerance and cardiovascular fitness. MethodsPatients (n = 31) undergoing SPECT/CT myocardial perfusion imaging underwent additional stress/rest SPECT/CT imaging of the lower extremities. CT-based image segmentation was used for regional quantification of perfusion reserve within the tibialis anterior, soleus, and gastrocnemius muscles. Metabolic equivalents (METs) at peak exercise and heart rate recovery (HRR) after exercise were recorded. ResultsPeak METs were significantly associated with perfusion reserve of tibialis anterior (p = 0.02), soleus (p = 0.01) and gastrocnemius (p = 0.01). HRR was significantly associated with perfusion reserve of the soleus (p = 0.02) and gastrocnemius (p = 0.04) muscles. Perfusion reserve of the tibialis anterior (40.6 ± 20.2%), soleus (35.4 ± 16.7%), and gastrocnemius (29.7 ± 19.1%) all significantly differed from each other. ConclusionsSPECT/CT imaging provides regional quantification of skeletal muscle perfusion reserve which is significantly associated with exercise tolerance and cardiovascular fitness. Future application of SPECT/CT may elucidate the underlying skeletal muscle adapations to exercise therapy in patients with cardiovascular diseases.
Highlights
Exercise is often prescribed for clinical management of cardiovascular diseases with limited understanding of the physiological processes responsible for exercise-induced improvements in functional capacity, which is partially due to many clinical tests being unable to non-invasively evaluate physiological changes that occur within skeletal muscle in response to exercise therapy
We have demonstrated that quantitative evaluation of skeletal muscle perfusion reserve can be achieved by incorporating additional lower extremity single photon emission computed tomography (SPECT)/CT imaging into routine one-day stress/rest SPECT/CT myocardial perfusion imaging protocols without the need for additional radiotracer injection or exercise stress testing
In the present study, using a stress/rest SPECT/CT imaging protocol during standard treadmill stress testing, we demonstrate the ability of SPECT/CT imaging to quantify perfusion responses to functional treadmill walking/running exercise within individual muscle groups of the calf, which has not been previously achieved by magnetic resonance imaging (MRI), positron emission tomography (PET), or SPECT-based imaging investigations
Summary
Exercise is often prescribed for clinical management of cardiovascular diseases with limited understanding of the physiological processes responsible for exercise-induced improvements in functional capacity, which is partially due to many clinical tests being unable to non-invasively evaluate physiological changes that occur within skeletal muscle in response to exercise therapy. A non-invasive approach that is capable of quantifying skeletal muscle perfusion and represents a composite index of changes in both the macrovasculature and microvasculature may correlate better with functional capacity and could assist in elucidating the underlying exercise-induced mechanisms of functional improvement, thereby improving the evaluation of exercise therapy for various forms of cardiovascular disease, such as PAD. We evaluated the potential of lower extremity single photon emission computed tomography (SPECT)/CT perfusion imaging as a non-invasive correlate to exercise tolerance and cardiovascular fitness
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