Diabetic foot syndrome: importance of calf muscles MR spectroscopy in the assessment of limb ischemia and effect of revascularization
Abstract
Aim: The standard method for assessment of e?ect of revascularization in patients with diabetic foot (DF) and critical limb ischemia (CLI) is transcutaneous oxygen pressure (TcPO2). Phosphorus magnetic resonance spectroscopy (31P MRS) enables to evaluate oxidative muscle metabolism that could be impaired in patients with diabetes and its complications.
The aim of our study was to compare MRS of calf muscle between patients with DF and CLI and healthy controls and to evaluate the contribution of MRS in the assessment of the e?ect of revascularization. Methods: Thirty-four diabetic patients with DF and CLI treated either by autologous cell therapy (ACT; 15 patients) or percutaneous transluminal angioplasty (PTA; 12 patients) in our foot clinic during 2013-2016 and 19 healthy controls were included into the study.
TcPO2 measurement was used as a standard method of non-invasive evaluation of limb ischemia. MRS examinations were performed using the whole-body 3T MR system 1 day before and 3 months after the procedure.
Subjects were examined in a supine position with the coil fxed under the m. gastrocnemius. MRS parameters were obtained at rest and during the exercise period.
Rest MRS parameters of oxidative muscle metabolism such as phosphocreatine (PCr), inorganic phosphate (Pi), phosphodiesters (PDE), adenosine triphosphate (ATP), dynamic MRS parameters such as recovery constant PCr (tPCr) and mitochondrial capacity (Qmax), and pH were compared between patients and healthy controls, and also before and 3 months after revascularization. Results: Patients with CLI had signifcantly lower PCr/Pi (p < 0.001), signifcantly higher Pi and pH (both p < 0.01), signifcantly lower Qmax and prolonged tPCr (both p < 0.001) in comparison with healthy controls.
We observed a signifcant improvement in TcPO2 at 3 months after revascularization (from 26.4 +- 11.7 to 39.7 +- 17.7 mm Hg, p < 0.005). However, the rest MRS parameters did not change signifcantly after revascularization.
In individual cases we observed improvement of dynamic MRS parameters. There was no correlation between MRS parameters and TcPO 2 values.
Conclusion: Results of our study show impaired oxidative metabolism of calf muscles in patients with CLI in comparison with healthy controls. We observed an improvement in dynamic MRS parameters in individual cases; this fnding should be verifed in a large number of patients during longer follow-up.