INDIANAPOLIS – Analyzing myofibers obtained from muscle biopsies of patients with peripheral arterial disease may provide objective criteria to diagnose disease and determine its severity, a study has shown.
Researchers collected needle biopsies of the gastrocnemius muscle from 20 patients with peripheral arterial disease (PAD) with claudication, 19 patients with PAD and critical limb ischemia, and 20 controls. Individual myofibers in the samples were partitioned using image-processing algorithms.
Morphologic deterioration of myofibers in the ischemic muscle is closely linked to limb dysfunction in PAD, Dr. Dimitrios Miserlis explained at the meeting. Previous studies have used morphologic analyses of PAD muscle, but they have been largely qualitative and included very limited quantitative information.
A team of vascular surgeons, biologic imaging specialists, and biologic systems engineers from the University of Nebraska in Omaha and in Lincoln are developing a highly quantitative morphologic analysis of PAD myofibers. Using data from 31 patients, they tested 96 morphometric parameters and identified 8 that objectively define the myopathic changes in PAD muscle.
Combinations of these parameters in a two-stage mathematical model were able to discriminate healthy controls from PAD patients, and claudicating patients from patients with critical limb ischemia, said Dr. Miserlis of the department of surgery at the University of Nebraska Medical Center in Omaha.
“Our findings are correlated with the clinical picture,” he said.
Based on the first 31 patients, the 5 morphometric parameters used in the first stage of the model were variation in major axis [length], variation in solidity, variation in roundness, solidity, and fiber density.
Then in the remaining 28 participants, the model was able to identify all 19 controls and claudicating patients (100% accuracy) and 8 of 9 patients with critical limb ischemia (89% accuracy), for an overall accuracy of 96.4%, he said.
The second stage of the model used the morphometric parameters of variation in eccentricity, variation in minor axis (width), variation in solidity, variation in roundness, and average roundness. Among the same 28 participants, the model was able to identify 7 of 10 controls (70% accuracy), 8 of 9 claudicating patients (89% accuracy), and 8 of 9 critical limb ischemia patients (89% accuracy), for an overall accuracy of 82%.
The study proves that morphometrics can be developed into mathematical equations that categorize PAD patients according to degree of damage in their ischemic limb, Dr. Miserlis said. Each of these categories of damage can be targeted for biochemical analysis, providing precisely determined biochemical signatures of PAD initiation and disease progression.
This is important because “biochemical signatures may be used to direct and assess stage-specific therapeutic interventions,” he said.
The investigators, who continue to refine the model, believe that most fibers exhibiting these abnormal morphologic characteristics may be reparable with appropriate therapy, and they plan to evaluate this possibility in the near future. The study was led by coprincipal investigators George Casale, Ph.D.; Jeyamkondan Subbiah, Ph.D.; and Dr. Iraklis Pipinos.
Dr. Miserlis is supported by a scholarship from the Propondis Foundation. His colleagues received awards from the National Heart, Lung, and Blood Institute; the American Vascular Association; and the University of Nebraska.
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