Torsade de pointes during sevoflurane anesthesia in a child with congenital long QT syndrome

Prediction of anesthetic torsadogenicity using a human ventricular cell model

This simulation study was designed to predict the torsadogenicity of sevoflurane and propofol in healthy control, as well as type 1 and type 2 long QT syndrome (LQT1 and LQT2, respectively), using the O'Hara-Rudy dynamic model. LQT1 and LQT2 models were simulated by decreasing the conductances of slowly and rapidly activating delayed rectifier K+ currents (IKs and IKr, respectively) by 50%, respectively. Action potential duration at 50% repolarization level (APD50) and diastolic intracellular Ca2+ concentration were measured in epicardial cell during administration of sevoflurane (1 ~ 5%) and propofol (1 ~ 10 μM). Torsadogenicity can be predicted from the relationship between APD50 and diastolic intracellular Ca2+ concentration, which is classified by the decision boundary. Whereas the relationships in control and LQT1 models were distributed on nontorsadogenic side in the presence of sevoflurane at all tested concentrations, those in LQT2 models were shifted to torsadogenic side by concentrations of ≥ 2%. In all three models, propofol shifted the relationships in a direction away from the decision boundary on nontorsadogenic side. Our findings suggest that sevoflurane, but not propofol, exerts torsadogenicity in patients with reduced IKr, such as LQT2 patients. Caution should be paid to the occurrence of arrhythmia during sevoflurane anesthesia in patients with reduced IKr.

Elevation of propofol sensitivity of cardiac IKs channel by KCNE1 polymorphism D85N

BACKGROUND AND PURPOSE

The slowly activating delayed rectifier K⁺ channel (I_Ks ), composed of pore-forming KCNQ1 α-subunits and ancillary KCNE1 β-subunits, regulates ventricular repolarization in human heart. Propofol, at clinically used concentrations, modestly inhibits the intact (wild-type) I_Ks channels and is therefore unlikely to appreciably prolong QT interval in ECG during anaesthesia. However, little information is available concerning the inhibitory effect of propofol on I_Ks channel associated with its gene variants implicated in QT prolongation. The KCNE1 single nucleotide polymorphism leading to D85N is associated with drug-induced QT prolongation and therefore regarded as a clinically important genetic variant. This study examined whether KCNE1-D85N affects the sensitivity of I_Ks to inhibition by propofol.

EXPERIMENTAL APPROACH

Whole-cell patch-clamp and immunostaining experiments were conducted in HEK293 cells and/or mouse cardiomyocyte-derived HL-1 cells, transfected with wild-type KCNQ1, wild-type or variant KCNE1 cDNAs.

KEY RESULTS

Propofol inhibited KCNQ1/KCNE1-D85N current more potently than KCNQ1/KCNE1 current in HEK293 cells and HL-1 cells. Immunostaining experiments in HEK293 cells revealed that pretreatment with propofol (10 μM) did not appreciably affect cell membrane expression of KCNQ1 and KCNE1 proteins in KCNQ1/KCNE1 and KCNQ1/KCNE1-D85N channels.

CONCLUSION AND IMPLICATIONS

The KCNE1 polymorphism D85N significantly elevates the sensitivity of I_Ks to inhibition by propofol. This study detects a functionally important role of KCNE1-D85N polymorphism in conferring genetic susceptibility to propofol-induced QT prolongation and further suggests the possibility that the inhibitory action of anaesthetics on ionic currents becomes exaggerated in patients carrying variants in genes encoding ion channels.

Comparison of the Effects of Propofol and Sevoflurane on QT Interval in Pediatrics Undergoing Cochlear Implantation: A Randomized Clinical Trial Study

Background

Children with sensorineural hearing loss are at risk of cardiac electrophysiologic abnormalities. Inhalational Sevoflurane induction in these children can cause QT prolongation.

Objectives

In order to evaluate the safety of inhalational induction of anesthesia with sevoflurane in children with sensorineural hearing loss, who are candidates for cochlear implant, its electrophysiologic effects was compared with intravenous induction of anesthesia with propofol.

Methods

In this double-blind randomized clinical trial, 61 children aged between one and eighteen years old, who were candidates for cochlear implantation, were randomly allocated to groups receiving anesthesia with sevoflurane (n = 32) or propofol (n = 29) for induction of anesthesia. Two 12-leads ECG were taken from all of patients before and after induction and QTc, Tp-e interval, and JTc were measured and compared.

Results

Two cases, who had pre-induction QTc longer than 500 ms were excluded from the study. Patients had similar age (102.58 ± 87 versus 101.46 ± 67 months, P = 0.95) and gender (males: 48.3% versus 56.3%, P = 0.53) distribution. The researchers observed significant post induction difference in QTc values between these groups (propofol 422.5 ± 40, sevoflurane 445.0 ± 29, P = 0.016). There was no significant difference in the percent QTc and Tp-e changes in propofol and sevoflurane groups. Greater percentage of patients with increased Tp-e interval (> 100 ms) in the sevoflurane group than the propofol group was also seen. There was no significant long QTc difference (QTc > 500 ms or more than 60 ms increase from baseline) after induction of anesthesia in the sevoflurane group compared to the propofol group (15.6% versus 13.8%, P = 0.84).

Conclusions

After electrophysiological evaluations in children with sensorineural hearing loss, in patients whose pre-induction QTc is not longer than 500 ms, propofol seems safer than inhalational sevoflurane for induction of anesthesia.

Sevoflurane causes greater QTc interval prolongation in chronically hyperglycemic patients than in normoglycemic patients

QTc interval prolongation is a serious diabetic complication and increases mortality rate. Hyperglycemia inhibits the rapid component of delayed rectifier potassium channel currents (Ikr) and prolongs the QTc interval on electrocardiograms. Sevoflurane also inhibits the Ikr and causes QTc interval prolongation. In fact, torsade de pointes occurred in a patient with poorly controlled diabetes mellitus during sevoflurane anesthesia. We enrolled 74 patients, including 37 normoglycemic patients (glycated hemoglobin [HbA1c]: <6.5%) (NG group) and 37 chronically hyperglycemic patients (HbA1c: ≥6.5%) (HG group). Anesthesia was induced with 2 mg/kg propofol and 0.3 μg/kg/min remifentanil, and maintained with 2% sevoflurane in 40% O2 and 0.2-0.3 μg/kg/min remifentanil. The QT interval and Tp-e interval (from the peak to the end of the T wave) were measured before and at 5, 10, 30, 60, 90, and 120 min after the administration of sevoflurane and adjusted for the patient's heart rate (QTc and Tp-ec, respectively). P-values of <0.05 were considered statistically significant. The QTc and the Tp-ec intervals of the two groups did not differ significantly before the administration of sevoflurane. The QTc interval gradually increased with time in both groups and was significantly longer than the baseline value at 10 min after the administration of sevoflurane in both groups. The QTc interval of the HG group was significantly longer than that of the NG group at 90 min and 120 min after the administration of sevoflurane. The Tp-ec interval was not affected by sevoflurane in either group.We have demonstrated that sevoflurane significantly prolongs the QTc interval, and that the extent of the prolongation is significantly greater in chronically hyperglycemic patients than in normoglycemic patients. Although Tp-ec is not affected by sevoflurane, it should be noted that the simultaneous blockade of potassium channels would increase the risk of arrhythmias.

Sevoflurane prolonged the QTc interval and increased transmural dispersion of repolarization in a patient with long QT syndrome 3: a case report

We report that sevoflurane not only caused marked QTc interval prolongation but also increased transmural dispersion of repolarization in a patient with long QT syndrome 3 (LQT3). A 16-year-old male with LQT3 underwent a shoulder operation. He experienced no episode of syncope or cardiac arrest, but his preoperative electrocardiography (ECG) showed marked QTc interval prolongation (631 ms) and Tp-e interval prolongation (126 ms). Anesthesia was induced with propofol and maintained with 2% sevoflurane and remifentanil. Although no lethal arrhythmias occurred in the perioperative period, not only the QTc interval but also Tp-e interval was further prolonged by sevoflurane. While sevoflurane has been recognized as a safe anesthetic in terms of QT interval prolongation, even in patients with long QT syndromes, we believe that sevoflurane might be avoided for poorly controlled LQT3 patients.

Propofol inhibits hERG K+ channels and enhances the inhibition effects on its mutations in HEK293 cells

QT interval prolongation, a potential risk for arrhythmias, may result from gene polymorphisms relevant to cardiomyocyte repolarization. Another noted cause of QT interval prolongation is the administration of chemical compounds such as anesthetics, which may affect a specific type of cardiac K⁺ channel encoded by the human ether-a-go-go-related gene (hERG). hERG K⁺ current was recorded using whole-cell patch clamp in human embryonic kidney (HEK293) cells expressing wild type (WT) or mutated hERG channels. Expression of hERG K⁺ channel proteins was evaluated using western blot and confirmed by fluorescent staining and imaging. Computational modeling was adopted to identify the possible binding site(s) of propofol with hERG K⁺ channels. Propofol had a significant inhibitory effect on WT hERG K⁺ currents in a concentration-dependent manner, with a half-maximal inhibitory concentration (IC₅₀) of 60.9±6.4μM. Mutations in drug-binding sites (Y652A or F656C) of the hERG channel were found to attenuate hERG current blockage by propofol. However, propofol did not inhibit the trafficking of hERG protein to the cell membrane. Meanwhile, for the three selective hERG K⁺ channel mutant heterozygotes WT/Q738X-hERG, WT/A422T-hERG, and WT/H562P-hERG, the IC₅₀ of propofol was calculated as 14.2±2.8μM, 3.3±1.2μM, and 5.9±1.9μM, respectively, which were much lower than that for the wild type. These findings indicate that propofol may potentially increase QT interval prolongation risk in patients via direct inhibition of the hERG K⁺ channel, especially in those with other concurrent triggering factors such as hERG gene mutations.

Ventricular fibrillation after elective surgery in an adolescent with long QT syndrome

Congenital long QT syndrome (LQTS) is a potentially lethal but highly treatable channelopathy. Along with multiple risk reduction measures, a recommendation for left sympathetic cardiac denervation therapy and/or implantable cardioverter defibrillator is made for higher risk patients. Despite its relatively common incidence in paediatric patients, there are no formal recommendations regarding perioperative management and discharge criteria for LQTS patients undergoing ambulatory surgery. This report describes a 17-year-old girl, diagnosed with congenital LQTS at 9 years of age, who had an episode of ventricular fibrillation the day after elective ear, nose and throat surgery. Despite several risk factors, she had a same-day dismissal, was not adequately monitored postoperatively and her cardiologists were not notified of her procedure. For the high-risk LQTS patient, we recommend monitoring of perioperative electrolytes and rhythm, postoperative ECG, adequate β-blockade therapy, avoidance of particular pharmacological agents, consideration of overnight observation and communication with the patient's cardiologist prior to procedure, and at discharge.

[Perioperative treatment of patients with long QT syndrome]

Long QT syndrome (LQTS) is caused by a change in cardiac repolarization due to functional ion channel dysfunction which is associated with an elongation of the QT interval (hence the name) in the electrocardiogram and a predisposition to cardiac rhythm disorders (e.g. torsade de pointes, TdP) as well as cardiac events up to sudden cardiac death. There is a congenital (cLQTS) and an acquired (aLQTS) form of the disease. The prevalence of cLQTS is 1 in 2000 but aLQTS is much more common and includes a grey area due to many asymptomatic patients. The LQTS is, therefore, more common than malignant hyperthermia which is much discussed in anesthesiology and has a reported prevalence in the population of 1:3000. Considering the prevalence of both aLQTS as well as cLQTS the importance of the LQTS seems to be underestimated in current perioperative care. Potential perioperative risks of such patients can be significantly reduced by appropriate patient management. This includes adequate preoperative preparation, the correct choice of anesthetic medication as well as adequate perioperative monitoring and preparedness for immediate pharmaceutical and electrical intervention in case of typical cardiac rhythm disturbances, such as TdP arrhythmia.

Enhanced effects of isoflurane on the long QT syndrome 1-associated A341V mutant

BACKGROUND

The impact of volatile anesthetics on patients with inherited long QT syndrome (LQTS) is not well understood. This is further complicated by the different genotypes underlying LQTS. No studies have reported on the direct effects of volatile anesthetics on specific LQTS-associated mutations. We investigated the effects of isoflurane on a common LQTS type 1 mutation, A341V, with an unusually severe phenotype.

METHODS

Whole cell potassium currents (IKs) were recorded from HEK293 and HL-1 cells transiently expressing/coexpressing wild-type KCNQ1 (α-subunit), mutant KCNQ1, wild-type KCNE1 (β-subunit), and fusion KCNQ1 + KCNE1. Current was monitored in the absence and presence of clinically relevant concentration of isoflurane (0.54 ± 0.05 mM, 1.14 vol %). Computer simulations determined the resulting impact on the cardiac action potential.

RESULTS

Isoflurane had significantly greater inhibitory effect on A341V + KCNE1 (62.2 ± 3.4%, n = 8) than on wild-type KCNQ1 + KCNE1 (40.7 ± 4.5%; n = 9) in transfected HEK293 cells. Under heterozygous conditions, isoflurane inhibited A341V + KCNQ1 + KCNE1 by 65.2 ± 3.0% (n = 13) and wild-type KCNQ1 + KCNE1 (2:1 ratio) by 32.0 ± 4.5% (n = 11). A341V exerted a dominant negative effect on IKs. Similar differential effects of isoflurane were also observed in experiments using the cardiac HL-1 cells. Mutations of the neighboring F340 residue significantly attenuated the effects of isoflurane, and fusion proteins revealed the modulatory effect of KCNE1. Action potential simulations revealed a stimulation frequency-dependent effect of A341V.

CONCLUSIONS

The LQTS-associated A341V mutation rendered the IKs channel more sensitive to the inhibitory effects of isoflurane compared to wild-type IKs in transfected cell lines; F340 is a key residue for anesthetic action.

Effect of ramosetron on the QT interval during sevoflurane anaesthesia in children: a prospective observational study

BACKGROUND

We investigated the effects of concomitant administration of sevoflurane and ramosetron on the QT interval, the interval between the peak and end of the T wave (Tpe) and Tpe/QT ratio in children.

OBJECTIVES

To compare the effects of concomitant administration of ramosetron and sevoflurane on heart rate corrected interval with Bazett's formula (QTc), Tpe interval and Tpe/QT ratio.

DESIGN

A prospective observational study.

SETTING

Elective orthopaedic surgery with patient-controlled analgesia.

PATIENTS

Forty children aged between 3 and 12 years.

INTERVENTION

ECG recordings were collected before induction (BASE), before sevoflurane administration (SEVO) and after the administration of ramosetron (SEVO and R).

MAIN OUTCOME MEASURES

The heart rate corrected interval with Bazett's formula (QTc), Tpe interval and Tpe/QT ratio were calculated and the changes were analysed using repeated-measures analysis of variance (ANOVA).

RESULTS

The QTc interval at BASE was 388.5 ± 29.3 ms. It increased with sevoflurane anaesthesia to 414.9 ± 21.4 ms and did not change with the administration of ramosetron (418.2 ± 23.0 ms). The Tpe interval and Tpe/QT ratio did not differ between measurements. No ventricular arrhythmias occurred during the study.

CONCLUSION

Ramosetron was not associated with prolongation of the QTc interval when it was given concomitantly with sevoflurane in children. No ventricular arrhythmias or other adverse effects occurred during the study.

The effect of sevoflurane and ondansetron on QT interval and transmural dispersion of repolarization in children

BACKGROUND

This study evaluated the prolongation of QT interval by the combination of sevoflurane and ondansetron in pediatric patients. Additionally, transmural dispersion of repolarization as interval between the peak and end of the T wave (Tp-e) and Tp-e/QT ratio was also measured to assess the risk of ventricular arrhythmia.

METHODS

The 3-lead electrocardiography (ECG) in lead II was sampled at three stages: at preinduction, just before (Sevo alone) and finally, after administration of ondansetron (Sevo+Ondansetron) in 41 children aged from 3 to 12 years. The QT interval was corrected for heart rate using Bazett's formula. And, Tp-e interval was obtained, and Tp-e/QT ratio was calculated. For analysis of the changes of parameters, a repeated-measures analysis of variance was used to identify significant differences in QTc, Tp-e interval and Tp-e/QT ratio at the three epochs.

RESULTS

The mean QTc at preinduction period was 413.8 (20.8) ms. The mean Sevo alone and Sevo+Ondansetron QTcs were 432.5 (28.1) and 439.2 (27.6) ms, and the differences in QTc prolongation between stages were all significant (P < 0.01). Ondansetron increased Tp-e interval significantly; however, Tp-e/QT ratio was not different among three stages. There were no ECG abnormalities such as atrial or ventricular arrhythmia and T-wave abnormality in any patient.

CONCLUSIONS

Sevoflurane prolongs the QTc interval and its combination with ondansetron further increased this effect in children. However, the dispersion of ventricular repolarization was not significantly affected, and there were no adverse events such as ventricular arrhythmia in this study. The combination of sevoflurane and ondansetron may be clinically safe, but careful ECG monitoring is still advisable.

Perioperative torsade de pointes: a systematic review of published case reports

BACKGROUND

Torsade de pointes is a rare but potentially fatal arrhythmia. More than 40 cases of perioperative torsade de pointes have been reported in the literature; however, the current evidence regarding this complication is very limited. To improve our understanding, we performed a systematic review and meta-analysis of all published case reports of perioperative torsade de pointes.

METHODS

MEDLINE was systematically searched for cases of perioperative torsade de pointes. We included patients of all age groups and cases that occurred from the immediate preoperative period to the third postoperative day. Patient and case characteristics as well as QT interval data were extracted.

RESULTS

Forty-six cases of perioperative torsade de pointes were identified; 29 occurred in women (67%), and 2 episodes were fatal (case fatality rate: 4%). Craniotomies and cardiac surgery accounted for 40% of all cases. Preceding events identified by the authors were hypokalemia (12/46, 26%; 99% confidence interval [CI], 9%-43%) and bradycardia (7/46, 15%; 99% CI, 2%-28%). Drugs were implicated in approximately one third of the events (14/46, 30%; 99% CI, 13%-48%). The mean corrected QT (QTc) at baseline was 457 ± 67 milliseconds (minimum 320 milliseconds; maximum 647 milliseconds; data available in 27/46 patients). At the time of the event, the mean QTc increased to 575 ± 77 milliseconds (minimum 413 milliseconds; maximum 766 milliseconds; data available in 33/46 patients). On average, QTc increased by +118 milliseconds (99% CI, 70-166 milliseconds; P < 0.001) between baseline and after the torsade de pointes event. All patients, except for 2, had a substantial prolongation of their QTc interval at the time of the event.

CONCLUSIONS

This systematic review identified several common risk factors for perioperative torsade de pointes. Given the nearly uniform presence of a substantial QTc interval prolongation at the time of a torsade de pointes episode, increased vigilance for perioperative QTc interval prolongation may be warranted.

Drugs to be avoided in patients with long QT syndrome: Focus on the anaesthesiological management

Long QT syndrome incidence is increasing in general population. A careful pre-, peri- and post-operative management is needed for patients with this syndrome because of the risk of Torsades de Pointes and malignant arrhythmias. The available data regarding prevention of lethal Torsades de Pointes during anesthesia in patients with long QT syndrome is scant and conflicting: only case reports and small case series with different outcomes have been published. Actually, there are no definitive guidelines on pre-, peri- and post-operative anesthetic management of congenital long QT syndrome. Our review focuses on anesthetic recommendations for patients diagnosed with congenital long QT syndrome furnishing some key points for preoperative optimization, intraoperative anesthetic agents and postoperative care plan, which could be the best for patients with c-long QT syndrome who undergo surgery.

QT interval abnormalities: risk factors and perioperative management in long QT syndromes and Torsades de Pointes

Electrophysiological abnormalities of the QT interval of the standard electrocardiogram are not uncommon. Congenital long QT syndrome is due to mutations of several possible genes (genotype) that result in prolongation of the corrected QT interval (phenotype). Abnormalities of the QT interval can be acquired and are often drug-induced. Torsades de Pointes (TP) is an arrhythmia that is a result of aberrant repolarization/QT abnormalities. If not recognized and corrected quickly, QT interval abnormalities may precipitate potentially fatal ventricular dysrhythmias. The main mechanism responsible for the development of QT prolongation is blockade of the rapid component of the delayed rectifier potassium current (I kr), encoded for by the human-ether-a-go-go-related gene (hERG). The objectives of this review were (1) to describe the electrical pathophysiology of QT interval abnormalities, (2) to differentiate congenital from acquired QT interval abnormalities, (3) to describe the currently known risk factors for QT interval abnormalities, (4) to identify current drug-induced causes of acquired QT interval abnormalities, and (5) to recommend immediate and effective management strategies to prevent unanticipated dysrhythmias and deaths from QT abnormalities in the perioperative period.

The role of Volatile Anesthetics in Cardioprotection: a systematic review

This review evaluates the mechanism of volatile anesthetics as cardioprotective agents in both clinical and laboratory research and furthermore assesses possible cardiac side effects upon usage. Cardiac as well as non-cardiac surgery may evoke perioperative adverse events including: ischemia, diverse arrhythmias and reperfusion injury. As volatile anesthetics have cardiovascular effects that can lead to hypotension, clinicians may choose to administer alternative anesthetics to patients with coronary artery disease, particularly if the patient has severe preoperative ischemia or cardiovascular instability. Increasing preclinical evidence demonstrated that administration of inhaled anesthetics - before and during surgery - reduces the degree of ischemia and reperfusion injury to the heart. Recently, this preclinical data has been implemented clinically, and beneficial effects have been found in some studies of patients undergoing coronary artery bypass graft surgery. Administration of volatile anesthetic gases was protective for patients undergoing cardiac surgery through manipulation of the potassium ATP (K_ATP) channel, mitochondrial permeability transition pore (mPTP), reactive oxygen species (ROS) production, as well as through cytoprotective Akt and extracellular-signal kinases (ERK) pathways. However, as not all studies have demonstrated improved outcomes, the risks for undesirable hemodynamic effects must be weighed against the possible benefits of using volatile anesthetics as a means to provide cardiac protection in patients with coronary artery disease who are undergoing surgery.

The clinical significance of QT interval prolongation in anesthesia and pain management: what you should and should not worry about

The most feared drug-induced complication is fatal cardiac arrest. Torsades de pointes (TdP) is a polymorphic ventricular tachycardia occurring in the setting of a QT interval prolongation and is the most frequent type of drug-induced pro-arrhythmia. The most common mechanism of QT prolongation and TdP is blockade of the rapid component of the delayed rectifier repolarizing potassium conductance IKr. Anesthesiologists have extensive experience with QT prolonging drugs, but there are relatively few reports of TdP occurring in the perioperative setting. Nevertheless, regulatory concern regarding the drug droperidol resulted in a significant reduction in its use. Concern regarding two other agents that potently block IKr, i.e., sevoflurane and methadone, has grown, and practitioners are worried that these valuable agents may meet the same fate. In this review, the data regarding the TdP risk of droperidol, sevoflurane, and methadone are compared with particular emphasis on the different settings in which they are employed. While the three drugs are potent IKr inhibitors, little evidence exists to suggest that droperidol or sevoflurane are associated with significant proarrhythmia in the perioperative setting. Due to factors such as inhibition of the parasympathetic nervous system, prevention of hypoxia and hypercarbia, and attention to serum electrolytes, TdP is a very rare occurrence in the perioperative environment. Methadone, however, is typically given to outpatients, over long periods, and in combination with agents that inhibit its metabolism or are QT prolonging in their own right. Thus, pre- and post-drug electrocardiograms may be appropriate when prescribing methadone for outpatients, while the much lower risk for TdP (and the difficulties inherent in QT measurement in the perioperative period) render this approach unfruitful and worthy of reevaluation.

Perioperative management of hereditary arrhythmogenic syndromes

Patients with inherited cardiac channel disorders are at high risk of perioperative lethal arrhythmias. Preoperative control of symptoms and a multidisciplinary approach are required for a well-planned management. Good haemodynamic monitoring, adequate anaesthesia and analgesia, perioperative maintenance of normocarbia, normothermia, and normovolaemia are important. In congenital long QT syndrome, torsades de pointes should be prevented with magnesium sulphate infusion and avoidance of drugs such as droperidol, succinylcholine, ketamine, and ondansetron. Propofol and epidural anaesthesia represent safe choices, while caution is needed with volatile agents. In Brugada syndrome, β-blockers, α-agonists, and cholinergic drugs should be avoided, while isoproterenol reverses the ECG changes. Propofol, thiopental, and volatiles have been used uneventfully. In congenital sick sinus syndrome, severe bradycardia resistant to atropine may require isoproterenol or epinephrine. Anaesthetics with vagolytic properties are preferable, while propofol and vecuronium should be given with caution due to risk of inducing bradyarrhythmias. Neuraxial anaesthesia should produce the least autonomic imbalance. Arrhythmogenic right ventricular dysplasia/cardiomyopathy induces ventricular tachyarrhythmias, which should be treated with β-blockers. Generally, β-adrenergic stimulation and catecholamine release should be avoided. Halothane and pancuronium are contraindicated, while large doses of local anaesthetics and epinephrine should be avoided in neuraxial blocks. In catecholaminergic polymorphic ventricular tachycardia, β-blocker treatment should be continued perioperatively. Catecholamine release and β-agonists, such as isoproterenol, should be avoided. Propofol and remifentanil are probably safe, while halothane and pancuronium are contraindicated. Regional anaesthesia, without epinephrine, is relatively safe. In suspicious cardiac deaths, postmortem examination and familial screening are recommended.

Anesthesia induction with sevoflurane and propofol: evaluation of P-wave dispersion, QT and corrected QT intervals

The present study compared the effects of anesthesia induction with sevoflurane and propofol on hemodynamics, P-wave dispersion (Pwd), QT interval and corrected QT (QTc) interval. A total of 72 adult patients were included in this prospective study. All patients had control electrocardiograms (ECGs) before anesthesia induction. Anesthesia was induced with sevoflurane inhalation or intravenous propofol. Electrocardiography for all patients was performed during the 1(st) and 3(rd) minutes of induction, 3 minutes after administration of muscle relaxant, and at 5 minutes and 10 minutes after intubation. Pwd and QT intervals were measured on all ECGs. QTc intervals were determined using the Bazett formula. There was no significant difference in Pwd and QT and QTc intervals on control ECGs. In the sevoflurane group, except for control ECGs, Pwd and QTc interval on all ECGs were significantly longer than those in the propofol group (p < 0.05). We conclude that propofol should be used for anesthesia induction in patients with a predisposition to preoperative arrhythmias, and in those whose Pwd and QTc durations are prolonged on preoperative ECGs.

Comparison of the effect of sevoflurane and desflurane on postoperative arrhythmia and QT dispersion

The aim of this study was to investigate the effect of sevoflurane and desflurane on cardiac arrhythmias in adult patients who will be anesthetized. A total of 40 patients who were in the ASA I–II group and who were to undergo elective surgery were included in the study. No pre-medication was administered to the patients. They were monitored with the Holter equipment at preoperative 24 hours, and also at postoperative 24 hours on condition that Holter monitoring will begin before induction. Following routine monitoring, the patients were randomly divided into two equal groups; group one was given sevoflurane and group two was given desflurane. In this study, desflurane and sevoflurane resulted in both a significant prolongation of QT and QTc and a significant increase in QT and QTc dispersion when compared with the basal values. In the sevoflurane group, there was no significant increase in postoperative ventricular arrhythmia, compared to that during the preoperative period. However, this increase was significant in the desflurane group (p = 0.009). Sevoflurane and desflurane result in an increase in QT dispersion. Postoperative rhythmic control should carefully be monitored, especially in the desflurane group.

Pharmacogenomics of anesthetic drugs in transgenic LQT1 and LQT2 rabbits reveal genotype-specific differential effects on cardiac repolarization

Anesthetic agents prolong cardiac repolarization by blocking ion currents. However, the clinical relevance of this blockade in subjects with reduced repolarization reserve is unknown. We have generated transgenic long QT syndromes type 1 (LQT1) and type 2 (LQT2) rabbits that lack slow delayed rectifier K+ currents (IKs) or rapidly activating K+ currents (IKr) and used them as a model system to detect the channel-blocking properties of anesthetic agents. Therefore, LQT1, LQT2, and littermate control (LMC) rabbits were administered isoflurane, thiopental, midazolam, propofol, or ketamine, and surface ECGs were analyzed. Genotype-specific heart rate correction formulas were used to determine the expected QT interval at a given heart rate. The QT index (QTi) was calculated as percentage of the observed QT/expected QT. Isoflurane, a drug that blocks IKs) prolonged the QTi only in LQT2 and LMC but not in LQT1 rabbits. Midazolam, which blocks inward rectifier K+ current (IK1), prolonged the QTi in both LQT1 and LQT2 but not in LMC. Thiopental, which blocks both IKs and IK1, increased the QTi in LQT2 and LMC more than in LQT1. By contrast, ketamine, which does not block IKr, IKs, or IK1, did not alter the QTi in any group. Finally, anesthesia with isoflurane or propofol resulted in lethal polymorphic ventricular tachycardia (pVT) in three out of nine LQT2 rabbits. Transgenic LQT1 and LQT2 rabbits could serve as an in vivo model in which to examine the pharmacogenomics of drug-induced QT prolongation of anesthetic agents and their proarrhythmic potential. Transgenic LQT2 rabbits developed pVT under isoflurane and propofol, underlining the proarrhythmic risk of IKs blockers in subjects with reduced IKr.

FUNCTIONAL INTERACTION BETWEEN DPI 201-106, A DRUG THAT MIMICS CONGENITAL LONG QT SYNDROME, AND SEVOFLURANE ON THE GUINEA-PIG CARDIAC ACTION POTENTIAL

1. Sevoflurane produces QT prolongation on the electrocardiogram, predominantly via inhibition of the slow delayed rectifier K(+) current. DPI 201-106 is an experimental drug that produces QT prolongation by reducing Na(+) channel inactivation, thereby mimicking congenital long QT syndrome type 3 (LQT3). The present study explores the electrophysiological consequences of administration of sevoflurane in the presence of impaired Na(+) channel activity. 2. We examined the effects of sevoflurane and DPI 201-106, alone and in combination, on the cardiac action potential of guinea-pig ventricular myocytes using standard microelectrode techniques. 3. Both sevoflurane and DPI-201-106 prolonged action potential duration, with the combination of the two drugs producing greater than additive effects. Similarly, instability and triangulation of the action potential waveform, measures of pro-arrhythmia, were more pronounced when both drugs were combined. 4. Sevoflurane treatment significantly alters cardiac action potential waveforms when administered in the presence of impaired Na(+) channel inactivation. These results indicate the potential for ventricular arrhythmia when sevoflurane is administered to LQT3 patients and suggests caution when using sevoflurane in this population.

Electrophysiologic Mechanism Underlying Action Potential Prolongation by Sevoflurane in Rat Ventricular Myocytes

Background:

Despite prolongation of the QTc interval in humans during sevoflurane anesthesia, little is known about the mechanisms that underlie these actions. In rat ventricular myocytes, the effect of sevoflurane on action potential duration and underlying electrophysiologic mechanisms were investigated.

Methods:

The action potential was measured by using a current clamp technique. The transient outward K+ current was recorded during depolarizing steps from −80 mV, followed by brief depolarization to −40 mV and then depolarization up to +60 mV. The voltage dependence of steady state inactivation was determined by using a standard double-pulse protocol. The sustained outward current was obtained by addition of 5 mm 4-aminopyridine. The inward rectifier K+ current was recorded from a holding potential of −40 mV before their membrane potential was changed from −130 to 0 mV. Sevoflurane actions on L-type Ca2+ current were also obtained.

Results:

Sevoflurane prolonged action potential duration, whereas the amplitude and resting membrane potential remained unchanged. The peak transient outward K+ current at +60 mV was reduced by 18 ± 2% (P &lt; 0.05) and 24 ± 2% (P &lt; 0.05) by 0.35 and 0.7 mm sevoflurane, respectively. Sevoflurane had no effect on the sustained outward current. Whereas 0.7 mm sevoflurane did not shift the steady state inactivation curve, it accelerated the current inactivation (P &lt; 0.05). The inward rectifier K+ current at −130 mV was little altered by 0.7 mm sevoflurane. L-type Ca2+ current was reduced by 28 ± 3% (P &lt; 0.05) and 33 ± 1% (P &lt; 0.05) by 0.35 and 0.7 mm sevoflurane, respectively.

Conclusions:

Action potential prolongation by clinically relevant concentrations of sevoflurane is due to the suppression of transient outward K+ current in rat ventricular myocytes.

The pediatric cardiac patient presenting for noncardiac surgery

PURPOSE OF REVIEW

To summarize results of recent papers and discuss current trends concerning anesthesia in children with congenital heart disease presenting for noncardiac surgery.

RECENT FINDINGS

Children with congenital heart disease have a significant incremental risk when presenting for minor or major surgery. It is a current trend that noncardiac surgery should be performed in pediatric centers, which have anesthesiologists and pediatricians familiar with the multiple specialties of children with congenital heart disease. A careful preoperative evaluation using a multidisciplinary approach is of great importance. In recent studies and case reports, the safe use of newer anesthetic agents, such as sevoflurane or desflurane, was reported in combination with opioids or regional blocks. In addition to standard monitors, invasive monitoring should be considered liberally perioperatively in patients with limited hemodynamic reserve and with major surgery. Several case reports reported that laparoscopic surgery was successfully performed even in high-risk patients with congenital heart disease.

SUMMARY

Careful preoperative evaluation, experienced anesthesiologists, suitable anesthetic agents and techniques, and the liberal use of invasive monitoring are integral parts of safe and effective anesthetic care in children with congenital heart disease. Future studies have to show whether laparoscopic surgery may be beneficial in this special subgroup of patients.

A Comparison of the Effect on Dispersion of Repolarization of Age-Adjusted MAC Values of Sevoflurane in Children

BACKGROUND

QT interval prolongation is associated with torsades des pointes (TdP), but is a poor predictor of drug torsadogenicity. Susceptibility to TdP arises from increased transmural dispersion of repolarization (TDR) across the myocardial wall, rather than QT interval prolongation per se. TDR can be measured on the electrocardiogram as the time interval between the peak and end of the T-wave (Tp-e). Thus Tp-e is a readily measured assay of drug torsadogenicity. Several anesthetic drugs prolong the QT interval, but their effect on TDR is largely unknown.

METHODS

We investigated the effects of sevoflurane on corrected QT (QTc) and Tp-e intervals in 54 unpremedicated ASA I-II children, aged 3-10 yr, who were randomized to receive sevoflurane 1, 1.25, or 1.5 MAC, age-adjusted. Twelve-lead electrocardiograms were recorded before and after sevoflurane exposure. QTc and Tp-e were compared within and among groups using 2-way analysis of variance. Change in Tp-e after sevoflurane exposure was the primary outcome measure.

RESULTS

Sevoflurane significantly prolonged preoperative QTc at all doses (P < 0.005), with no dose-response relationship, but had no effect on preoperative Tp-e.

CONCLUSION

Sevoflurane markedly prolongs the QTc in healthy children, but does not increase dispersion of repolarization as measured by the Tp-e interval, indicating low or no torsadogenicity, and making it unlikely to increase predisposition to TdP.