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Limb Stress-Rest Perfusion Imaging With Contrast Ultrasound for the Assessment of Peripheral Arterial Disease Severity

Jonathan R. Lindner, MD, FACC^_*,_*, Lisa Womack, MS, Eugene J. Barrett, MD, PhD, Judy Weltman, MS, Wendy Price, RN, Nancy L. Harthun, MD, Sanjiv Kaul, MD, FACC^_*, James T. Patrie, MS

^_* Cardiovascular Division, Oregon Health & Science University, Portland, Oregon
General Clinical Research Center, University of Virginia, Charlottesville, Virginia
Endocrinology Division, University of Virginia, Charlottesville, Virginia
Department of Surgery, University of Virginia, Charlottesville, Virginia.

^_* Reprint requests and correspondence: Dr. Jonathan R. Lindner, Cardiovascular Division, UHN-62, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239. (Email: lindnerj{at}ohsu.edu).

Objectives: We hypothesized that stress-rest perfusion imaging of skeletal muscle in the lower extremity with contrast-enhanced ultrasound (CEU) could evaluate the severity of peripheral arterial disease (PAD).

Background: Perfusion imaging may provide valuable quantitative information on PAD, particularly in patients with diabetes in whom microvascular functional abnormalities are common.

Methods: Study subjects included 26 control subjects and 39 patients with symptomatic PAD, 19 of whom had type 2 diabetes mellitus. A modified treadmill exercise test was performed to determine exercise time to development of claudication. Multilevel pulse-volume recordings and ankle-brachial index (ABI) at rest and post-exercise ABI were measured in both extremities. Microvascular blood flow in the gastrocnemius and soleus muscles was measured at rest and after 2 min of calibrated plantar-flexion exercise.

Results: During exercise, claudication did not occur in normal subjects and occurred earlier in PAD patients with diabetes than without (median time 1.2 min [95% confidence interval (CI) 0.6 to 2.5] vs. 3.0 min [95% CI 2.1 to 6.0], p < 0.01). Compared to control subjects, patients with PAD had lower skeletal muscle blood flow during plantar-flexion exercise and lower flow reserve on CEU. After adjusting for diabetes, the only diagnostic tests that predicted severity of disease by claudication threshold were CEU exercise blood flow and flow reserve (odds ratios 0.67 [95% CI 0.51 to 0.88; p = 0.003] and 0.64 [95% CI 0.46 to 0.89, p = 0.008], respectively). A quasi-likelihood information analysis incorporating all non-invasive diagnostic tests indicated that the best models for predicting severity of disease were the combination of diabetes and either exercise blood flow or flow-reserve on CEU.

Conclusions: Perfusion imaging of limb skeletal during exercise and measurement of absolute flow reserve can provide valuable information on the severity PAD. This strategy may be useful for evaluating the total impact of disease in patients with complex disease or those with coexisting functional abnormalities of flow regulation.

Abbreviations and Acronyms   ABI = ankle-brachial index   CEU = contrast-enhanced ultrasound   DM = diabetes mellitus   PAD = peripheral arterial disease   PVR = pulse volume recording   VI = video intensity

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