Anesthetic Considerations for Pediatric Patients With Congenital Long QT Syndrome

What an anesthesiologist should know about pediatric arrhythmias

Identifying and treating pediatric arrhythmias is essential for pediatric anesthesiologists. Pediatric patients can present with narrow or wide complex tachycardias, though the former is more common. Patients with inherited channelopathies or cardiomyopathies are at increased risk. Since most pediatric patients present for anesthesia without a baseline electrocardiogram, the first identification of an arrhythmia may occur under general anesthesia. Supraventricular tachycardia, the most common pediatric tachyarrhythmia, represents a broad category of predominately narrow complex tachycardias. Stimulating events including intubation, vascular guidewire manipulation, and surgical stimulation can trigger episodes. Valsalva maneuvers are unreliable as treatment, making adenosine or other intravenous antiarrhythmics the preferred acute therapy. Reentrant tachycardias are the most common supraventricular tachycardia in pediatric patients, including atrioventricular reciprocating tachycardia (due to a distinct accessory pathway) and atrioventricular nodal reentrant tachycardia (due to an accessory pathway within the atrioventricular node). Patients with ventricular preexcitation, often referred to as Wolff-Parkinson-White syndrome, have a wide QRS with short PR interval, indicating antegrade conduction through the accessory pathway. These patients are at risk for sudden death if atrial fibrillation degenerates into ventricular fibrillation over a high-risk accessory pathway. Automatic tachycardias, such as atrial tachycardia and junctional ectopic tachycardia, are causes of supraventricular tachycardia in pediatric patients, the latter most typically noted after cardiac surgery. Patients with inherited arrhythmia syndromes, such as congenital long QT syndrome, are at risk of developing ventricular arrhythmias such as polymorphic ventricular tachycardia (Torsades de Pointes) which can be exacerbated by QT prolonging medications. Patients with catecholaminergic polymorphic ventricular tachycardia are at particular risk for developing bidirectional ventricular tachycardia or ventricular fibrillation during exogenous or endogenous catecholamine surges. Non-selective beta blockers are first line for most forms of long QT syndrome as well as catecholaminergic polymorphic ventricular tachycardia. Anesthesiologists should review the impact of medications on the QT interval and transmural dispersion of repolarization, to limit increasing the risk of Torsades de Pointes in patients with long QT syndrome. This review explores the key anesthetic considerations for these arrhythmias.

Diagnostic lacunae and implications of an automated implantable cardioverter defibrillator implantation in a child with type 3 Long QT (LQT3) syndrome

A diagnosis of congenital long QT interval syndrome based on history and electrocardiogram was made in a child in the absence of readily available genetic testing. A genotype 3 (LQT3) was suspected after exclusion of other variants as the child was non-responsive to beta-blocker and sodium channel blocker medication. As the child continues to show episodic bradycardia, polymorphic ventricular ectopy, and T-wave alternans, a single-chamber automated implantable cardioverter-defibrillator implantation was done successfully. This report highlights how the diagnosis of LQT3 was arrived at as well as the anesthetic challenges in the management of patients with LQTS.

Anesthesia for a Child with Congenital Long QT Syndrome, a Case Report and Literature Review

Long QT syndrome is an inherited disorder of the heart's electrical activity that may also be associated with malignant arrhythmia and cause sudden death. In addition to this inherited condition, several commonly used anesthetic drugs can prolong the QT interval. We present here a 17-month-old male patient who underwent general anesthesia for a cochlear implant. No cardiac arrhythmia was observed in the patient, whose muscle relaxant effect was reversed using sugammadex. The application of intravenous anesthetics was preferred to maintain anesthesia for this patient and was safely applied.

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.

PONV management in patients with QTc prolongation on the EKG

Postoperative nausea and vomiting (PONV) is a commonly encountered problem in surgical practice. It delays discharge from the post-anesthesia care unit, requires additional resources to treat, and may increase the morbidity in some patients. Many effective drugs are available to treat or prevent PONV, however many of these drugs have the potential to prolong the QTc on the electrocardiogram (EKG) and increase the risk of serious ventricular arrhythmias, in particular, torsade de pointes. The QTc prolongation may be a manifestation of a genetic mutation resulting in abnormal myocyte repolarization or it may be acquired and associated with the use of various medications, electrolyte disorders, and physiological conditions. Patients predisposed to QTc prolongation presenting for surgery constitute a challenging group, since many drugs commonly used for PONV management will put them at risk for perioperative serious arrhythmias. This is an important topic, and our mini-review is an attempt to highlight the problem, summarize the existing experience, and generate recommendations for safe management of PONV for patients, who are at increased risk of QTc prolongation and arrhythmias. Focused prospective studies will help to find definitive answers to the discussed problems and challenges and develop specific guidelines for clinical application.