No relationship between fiber type and halothane contracture test results in malignant hyperthermia

Previous studies in cat, rat, and swine have implicated fiber type as influencing the halothane and caffeine contracture test used to diagnose malignant hyperthermia (MH). The authors performed fiber type analysis using myosin ATPase stains on 31 fascicles of skeletal muscle from nine patients following contracture testing. There was no significant difference in fiber type composition between fascicles from MH negative (n = 5) and MH positive (n = 4) patients. Furthermore, examining each of the 31 fascicles, the authors found no correlation (P greater than .05) of contracture magnitude with percentage of either Type I or Type II fibers using the Pearson Product-Moment correlation calculation. The authors conclude that fiber type composition does not influence contracture test results in human biopsies.