Anaesthetics and the rate corrected interval: learning from droperidol?
OBJECTIVE
Understanding of the long QT syndrome continues to evolve. Anaesthesia in patients with untreated long QT syndrome carries a risk of perioperative malignant ventricular arrhythmias. Genotypically susceptible individuals may have a normal rate-corrected QT interval and present with torsade de pointes intraoperatively. The likelihood of arrhythmias can be reduced by careful preoperative preparation. Perioperative disturbances in physiological homeostasis and drugs administered can prolong the rate-corrected QT interval.


RESULTS
Seven ion channel genes have been discovered and over 300 mutations identified. For acquired long QT syndrome, the main issue is the blockade of a slow component of delayed rectifier potassium ion current. Preclinical tests are recommended to assess potential new drugs for QT prolongation. Drugs not increasing the transmural dispersion of repolarization have little potential to induce arrhythmias despite prolonging the QT interval. Diagnostic DNA testing is used to screen families. Although gene-based specific therapy is preliminary, molecular genetic analysis could be useful to unravel subclinical mutations. Future therapeutic strategies include the use of sodium antagonists, potassium channel activators and protein kinase inhibitors.


CONCLUSIONS
Droperidol can lead to serious cardiac arrhythmias from QT prolongation. Recent advances in the pathophysiology of congenital and acquired long QT syndrome are reviewed. Preclinical tests assessing potential new drugs for QT prolongation are briefly discussed. Considerations for the management of these patients during perioperative phases are explored. The optimal treatment of the long QT syndrome is presented along with a glimpse into future possibilities in this field.
Department of Anaesthesia, Christchurch School of Medicine, University of Otago, Christchurch, New Zealand. shiptonea@xtra.co.nz
Edward A
EA
Shipton