Authors: Destiny F. Chau, MD - Arkansas Children’s Hospital/University of Arkansas for Medical Sciences, Little Rock, AR AND Meera Gangadharan, MBBS, FAAP, FASA Children’s Memorial Hermann Hospital, University of Texas Health Science Center, Houston, TX
A 14-year-old patient with a history of long QT syndrome, not currently under treatment with medication or device therapy, is undergoing an appendectomy. During anesthesia emergence, sinus tachycardia at 150 bpm with non-sustained runs of Torsades de pointes are observed. Which of the following pharmacologic treatments for the arrhythmia has the HIGHEST risk of causing hemodynamic instability?
EXPLANATION
Congenital long QT syndrome (LQTS) is characterized by QTc prolongation on the electrocardiogram (ECG) and is associated with increased risk of life-threatening cardiac arrhythmias. LQTS results from heterogeneous genetic abnormalities of potassium or sodium ion channels involved in ventricular repolarization. It is the most common inherited arrhythmia syndrome, occurring in 1 out of every 2,500 individuals. It is associated with syncope, polymorphic ventricular tachycardia (Torsades des pointes) and sudden cardiac arrest. The rate of cardiac events is directly proportional to the degree of QTc prolongation.
The genetic mutations associated with LQTS are categorized into three subtypes, accounting for 95% of LQTS, and include LQT1, LQT2, and LQT3. LQT1 and LQT2 relate to mutations affecting potassium channels whereas in LQT3, mutations affect sodium channels. Patients with LQT1 are most triggered by sudden increases in sympathetic tone, such as stress or exercise. This is particularly notable with swimming, which has been associated with drowning in seemingly healthy young individuals. Patients with LQT2 are more prone to emotional stress, such as being frightened or startled. Patients with LQT3 are more likely to have events at rest.
Nonselective beta-blockers are first-line therapy, which can significantly decrease symptomatology, especially in those with LQT1 genotype. Cardiac sympathetic denervation can reportedly reduce the frequency of cardiac arrhythmia and is considered for patients who are intolerant of beta blockers or are poor candidates for cardiac implanted electronic devices.
Perioperative considerations for patients with LQTS include continuing beta blockers, reducing sympathetic stimulation, avoiding QTc prolonging drugs, and ensuring normal electrolytes, especially potassium, calcium, and magnesium. Although many perioperative anesthetic drugs can prolong the QTc, they can be used without untoward effects. The recommendation is to minimize the simultaneous occurrence of arrhythmogenic triggers, such as avoiding the administration of QTc prolonging drugs during periods of catecholamine surges, for example administering ondansetron during anesthesia emergence. For treatment of sinus tachycardia, esmolol is a good choice for rapid rate control. Further, should Torsades des pointes (TdP) occur, magnesium sulfate is the treatment of choice. Lidocaine, a sodium channel blocker, is also safe to use for ventricular arrhythmias associated with LQTS because it does not prolong the QTc interval. Antiarrhythmic class III agents, such as amiodarone and sotalol, should be avoided because they prolong the action potential duration and refractoriness, which may exacerbate this arrhythmia.
The correct answer is C. Amiodarone can worsen the TdP, thus it should be avoided. This patient is having sinus tachycardia with non-sustained runs of TdP, therefore esmolol can be used for rate control of the sinus tachycardia, while lidocaine can be used to treat the non-sustained runs of TdP. Ultimately, magnesium is the treatment of choice for TdP. Cardioversion should be used in the setting of hemodynamically unstable arrhythmias.
REFERENCES
Kuntz MT, Eagle SS, Dalal A, Samouil MM, Staudt GE, Londergan BP. What an anesthesiologist should know about pediatric arrhythmias. Paediatr Anaesth. 2024;34(12):1187-1199. doi:10.1111/pan.14980
Shah MJ, Silka MJ, Silva JNA,et al. 2021 PACES Expert Consensus Statement on the Indications and Management of Cardiovascular Implantable Electronic Devices in Pediatric Patients. Heart Rhythm. 2021;18(11):1888-1924. doi:10.1016/j.hrthm.2021.07.038
Valdes SO, Kim JJ, Miller-Hance W. Arrhythmias: Diagnosis and Management. In: Andropoulos DB, Mossad EM, Gottlieb EA, ed. Anesthesia for Congenital Heart Disease. 4th ed. Hoboken, New Jersey: Wiley-Blackwell; 2023: 674-709
