الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 166 |  |  |
| | | from | 166 | | |
Abstract
Ischemia is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. Atherosclerosis or PAD is the most common cause of arterial occlusive diseases that leads to lower limb ischemia. In patients with chronic lower limb ischemia, resting blood flow is similar to that of a healthy person. However, during exercise, blood flow cannot maximally increase in muscle tissue because of proximal arterial stenoses. When the metabolic demands of the muscle exceed blood flow, claudication symptoms ensue (Rowe, 2011). Muscle ischemia adversely affects muscle metabolism. In the ischemic muscle during exercise the levels of inorganic phosphate are very high as the breakdown of ATP and phosphocreatine is elevated. Therefore, the ratio of inorganic phosphates to phosphocreatine increases to a greater extent than in the normoperfused muscle. The result is a higher rate of glycolytic metabolism as indicated by the marked drop in pH. These changes observed by 31P magnetic resonance spectroscopy are in accordance with studies using needle biopsy, which demonstrated increased accumulation of lactate and depletion of cellular ATP during exercise in claudicants compared with normal subject (Kemp et al, 1995). Reduced ATP synthesis is the consequence of reduced vascular perfusion which decreases both oxygen delivery and the washout of toxic metabolites from the muscle. Patients with claudication accumulate acetylcarnitine (thus reflecting acetyl-CoA accumulation) and lactate (as a consequence of PDH inhibition). In the current study, proton 1H – MRS was used to assess metabolic changes in ischemic limbs with different grades of lower limb ischemia. Sucsessfuly, it was able to detect lactate accumulation in critically ischemic muscle evidenced by the significant difference in Lac/Cr ratio between healthy and critically ischemic muscle. There was also detectable glucose metabolism changes with decreased levels in ischemic limbs compared to healthy volunteers, this was documented by the Glu/Cr ratio changes.While creatine is a stable metabolite which makes it suitable chemical compund as a reference in patients and healthy volunteers. There was evidence of increased lactate concentration after exercising in mildly ischemic limbs demonstrated by the significant increase in lac/Cr ratio after exercise Glu/lac ratio could be consideered a key marker of crtically ischemic muscle. 1H-MRS is a promising technique that can be considered complementary technique to other imaging modalities in evaluation of lower limb ischemia. It can sensitively reflect altered muscle metabolism in patients with critical ischemia. However, there is overlap between metabolite ratios in healthy and mildly ischemic muscle. Further studies are still recommended for larger numbers of patients to assess the role of 1H-MRS in evaluation of mild ischemia and in assessment of muscle recovery after revascularization