Xe-133 muscle blood flow in polymyositis and dermatomyositis

The histologic picture of polymyositis or dermatomyositis is characterized by muscle fiber degeneration, which is assumed to be caused by a circulatory abnormality. To verify this assumption, we measured the muscle blood flow in patients with polymyositis (or dermatomyositis) and in normal subjects using the inert gas Xe-133. Sixteen patients and 30 age-matched normal volunteers were studied. Muscle blood flow was measured with Xe-133 dissolved in isotonic saline as described by Lassen et al. (1964) and Pozderac et al. (1975). Data were acquired in the frame mode after intramuscular injection (anterior tibial muscle) of 0.3 mCi of Xe-133 in 0.2ml of saline for 20 min. A computer routine was used to calculate the clearance half time (T 1/2) in min and flow rate (Q) in ml/100 gm tissue/min. The student's t test was used to test statistical significance. Our preliminary results suggest: 1. The muscle blood flow in patients with polymyositis and dermatomyositis was significantly lower than the corresponding normal control levels. 2. This findings may be due to decreased in muscle capillary 3. Further studies are warranted to obtain a conclusive understanding of the pathogenesis of polymyositis and dermatomyositis.