Surya Gnyawali, PhD – Surgery – Indiana University; Chandan K Sen, PhD – Surgery – Indiana University
Introduction: Critical limb Ischemia (CLI) is the advanced stage of peripheral arterial disease (PAD). CLI is characterized by ischemic rest pain, non-healing ischemic ulcers, and gangrene with both life and limb threatening complications. CLI carries about 25% to 40% risk of major amputation with 20% annual mortality. Currently, there is no specific treatment that target ischemic myopathy characteristic of CLI. Current swine models of CLI, with tolerable side-effects, fail to achieve sustained ischemia followed by a necrotic myopathic endpoint. Such limitation in experimental model hinders development of effective interventions. Thus, this work sought to develop a robust and clinically relevant swine model of CLI involving ischemic muscle necrosis.
Methods: CLI was induced unilaterally by ligation-excision of one inch of the common femoral artery (CFA) via infra-inguinal minimal incision in female Yorkshire pigs (n=5). X-ray arteriography was done pre- and post-CFA transection to validate successful induction of severe ischemia. Weekly assessment of the sequalae of ischemia on limb perfusion, and degree of ischemic myopathy was conducted for 1 month using X-ray arteriography, laser speckle imaging (LSI), angiography, Duplex ultrasound, high resolution ultrasound and histopathological analysis.
Results: Successful induction of CLI was achieved in all pigs and was confirmed using invasive and non-invasive imaging modalities. Gait disturbance and limping were recorded in all pigs. The angiography showed complete cessation of blood flow downstream the CFA without jeopardizing the pelvic vessels and organs. Arterial duplex indicis (Pulsatility index, Resistive index and Systolic to diastolic ratio were significantly lower in ischemic limb compared to contra lateral limb demonstrating the development of Ischemia at all timepoints (p< 0.05; n = 5). The non-invasive tissue analysis of the elastography images showed specific and characteristic pattern of increased muscle stiffness indicative of the fibrotic and necrotic outcome. The prominent skeletal muscle necrosis was evident upon direct inspection of the affected tissues. Ischemic myopathic changes associated with inflammatory infiltrates and deficient blood vessels were objectively validated by histopathological analysis.
Discussion: A translational model of severe hindlimb ischemia causing ischemic myopathy was successfully established adopting an approach that enable long-term survival studies in compliance with regulatory requirements pertaining to animal welfare.
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