In Reply:—
We appreciate the commentary and the excellent points raised by Dr. Katz. We apologize for the omission of his excellent case report from our extensive though limited bibliography. It is true, as it states both in the original article and in Dr. Katz' letter, that our information about anesthetic management of long QT syndrome (LQTS) is derived primarily from case reports and anecdotal data. We agree thoroughly that preoperative control allows for the optimal intraoperative and postoperative management.
Second, Dr. Katz opines that genetic testing may not be routinely available but that electrocardiogram analysis may offer insight into the genetic subtype. We agree that it is important to elucidate the genetic subtype for treatment purposes. Since the birth of cardiac channelopathies in 1995, LQTS genetic testing has been performed in a few specialized research laboratories. However, clinical genetic testing for LQTS has been available for nearly a year now. Except for perhaps a few expert T-wave morphologists, great caution should be exercised in attempting to genotype based on inspection of the electrocardiogram.
In response to the correspondence from Drs. Rasche and Hübler, we agree that the heterogeneity of repolarization is the prominent feature of LQTS and that the QT interval only relays general information about the effect of anesthetic medications. Although the effect of isoflurane on delayed rectifier potassium ion channels has been shown to be inhibitory at supratherapeutic concentrations and nonphysiologic temperatures, we do not believe that these data warrant the exclusion of isoflurane as an inhaled anesthetic; however, we respect the assertion that a total intravenous anesthetic may be a more conservative approach to use in patients with LQTS.
*Mayo Clinic College of Medicine, Rochester, Minnesota. ackerman.michael@mayo.edu
