VIABILITY CRITERION OF MUSCLE BUNDLES USED IN THE IN-VITRO CONTRACTURE TEST IN PATIENTS WITH NEUROMUSCULAR DISEASES

We have compared the viability criteria of muscle bundles used in the in vitro contracture test for susceptibility to malignant hyperthermia (MH) in a group of 28 patients with various neuromuscular diseases (N MD) and 93 MH-related family patients. In the patients with NMD, this standard test gave one positive, six equivocal and 21 negative results . Compared with MH-related family patients, muscle bundles used had si gnificantly smaller resting membrane potentials and smaller predrug tw itch tension amplitudes. Some results from the group with NMD were obt ained with muscles which were damaged, more rapidly deteriorating non- standard, or both, and should not be taken to indicate that the patien ts have the genetic trait for MH. The in vitro contracture test is not always relevant for myopathic muscle (especially dystrophic muscle) a nd this could explain the lack of specificity for MH.