Effect of Anaesthesia on the QT Interval

Abstract

The QT interval, which is measured from the start of the Q wave (or the R wave when no Q wave is present) to the completion of the T wave, reflects the duration of electrical ventricular systole. The duration of systole varies with heart rate and therefore the measured QT interval is often corrected for heart rate using the following formula, in which QTc represents the rate corrected value: QTc = Qt/VRR interval The QTc interval is normally less than 440 ms [1]. Increased serum concentrations of noradrenaline and a change in the balance between sympathetic and parasympathetic tone may be associated with prolonged QT interval [2, 3]; this may be controlled with either f}-block [4] or stellate ganglion block [5]. Hypomagnesaemia and, more commonly, hypokalaemia cause clinically significant prolongation which may be produced by effects on the repolarizing potassium current. Sleep (which is associated with a reduction in sympathetic tone) prolongs QTc [6]. Induction of anaesthesia with thiopentone prolongs significantly the QT interval [7], whereas Althesin had no effect [8]. The most marked changes follow tracheal intubation facilitated with suxamethonium, but these changes may be reduced by pretreatment with tubocurarine [7] or by (3-block [9], suggesting mediation by the sympathetic nervous system. It has been reported also that the QT interval is significantly prolonged by enflurane [8, 10], but not by halothane anaesthesia [8]. The mechanism underlying these differences has not been explained. It has been reported that these volatile agents and also

The Effects of Local Anaesthetics on QT Parameters during Thoracic Epidural Anaesthesia Combined with General Anaesthesia: Ropivacaine versus Bupivacaine

“…Propofol-induced prolongation of the QTc interval has been observed in various studies (17)(18)(19). In the present study, the QT interval was prolonged after propofol injection, but we did not observe any QTc prolongation with propofol usage.…”

Effects of fentanyl pretreatment on the QTc interval during propofol induction

“…Propofol prolonged the QTc interval significantly in some studies [26,27], while others showed it to have little or no effect [4,7]. Although the duration of propofol infusion was short compared to some other studies [4,7], over the time studied it did not prolong the QTc intervals before laryngoscopy.…”

Acquired Long QT Syndrome: Frequency, Onset, and Risk Factors in Intensive Care Patients

“…[40][41][42][43] In our study, the patients with aLQTS often had the syndrome at the time of ICU admission (30%), or aLQTS developed soon after their admission to the unit (70%); the mean time of onset was 10.6 hours after ICU admission. Our sample included 8 patients who had major surgery and returned to the ICU from the operating room.…”

“…(Critical Care Nurse. 2012;32 [5]: [32][33][34][35][36][37][38][39][40][41] Feature ©2012 American Association of Critical-Care Nurses doi: http://dx.doi.org/10.4037/ccn2012900…”

“…Clinicians have known for several decades that flurane can affect cardiac repolarization, leading to aLQTS. [39][40][41][42][43] Cases most often occur in older patients with predisposing risk factors such as electrolyte abnormalities and/or ischemic heart disease. 47,48 However, in a recently reported case, 49 ventricular tachycardic arrest developed in a healthy 35-year-old woman after QTc prolongation during a simple septoplasy with general anesthesia.…”