Prolonged (or long) QT syndrome (LQTS) is the perturbation of ion channels impairing ventricular repolarization, which puts patients at increased risk for Torsades de pointes, a polymorphic ventricular tachycardia. Prolongation of the QT segment results from either congenital genetic mutations or the effects of drugs or metabolic abnormalities on the ion channels responsible for repolarization (Table 62-4). Congenital LQTS can occur in children at any age. The prevalence is 1 in 5000 persons.[88] [89] Most of the genetic mutations are inherited in an autosomal-dominant manner. Far less common is the autosomal-recessive LQTS and sensorineural deafness, affecting 1 in 1 million people.[90] These patients present with syncope, seizures, or sudden cardiac death after an increase in sympathetic activity, commonly in the form of exercise, an auditory stimulus, or emotional stress.

A preoperative electrocardiographic evaluation should be performed on children with a history of any these manifestations, who have a family history of sudden death, or who are receiving long-term administration of one of the drugs listed in Table 62-4, looking for a QT_c greater than 470 ms in male patients and 480 ms in female patients. Only 60% of patients are symptomatic at the time of recognition.[91] Children with LQTS should have electrolytes measured to ensure that serum levels of potassium, calcium, and magnesium are normal. Patients with a risk of congenital LQTS should avoid all of the drugs listed in Table 62-4, if possible. Potent anesthetic vapors have effects on the cardiac conduction system and should be used in these patients with great care.[92]

Generic Name	Brand Name	Category*
Albuterol	Ventolin, Proventil	3
Amantadine	Symmetrel	2
Amiodarone	Pacerone, Cordarone	1
Amphetamine/dextroamphetamine	Adderall	3
Atomoxetine	Strattera	3
Azithromycin	Zithromax	2
Chloral hydrate	Noctec	2
Chloroquine	Arelan	1
Chlorpromazine	Thorazine	1
Clarithromycin	Biaxin	1
Clozapine	Clozaril	2
Dextroamphetamine	Dexadrine	3
Disopyramide	Norpace	1
Dobutamine	Dobutrex	3
Dolasetron	Anzemet	2
Dopamine	Intropin	3
Droperidol	Inapsine	1
Ephedrine	Rumatuss	3
Epinephrine	Primatene, Bronkaid	3
Erythromycin	Erythrocin , EES	1
Felbamate	Felbatrol	2
Flecainide	Tambocor	2
Foscarnet	Foscavir	2
Fosphenytoin	Cerebyx	2
Gemifloxacin	Factive	2
Granisetron	Kytril	2
Halofantrine	Halfan	1
Haloperidol	Haldol	1
Isoproterenol	Isupres, Medihaler-Iso	3
Isradipine	Dynacirc	2
Levalbuterol	Xopenex	3
Levofloxacin	Levaquin	2
Lithium	Lithobid, Eskalith	2
Metaproterenol	Alupent, Metaprel	3
Methadone	Dolophine, Methadose	1
Methylphenidate	Ritalin , Concerta	3
Milodrine	ProAmantine	3
Moxifloxacin	Avelox	2
Nicardipine	Cardene	2
Norepinephrine	Levophed	3
Octreotide	Sandostatin	2
Ofloxacin	Floxin	2
Ondansetron	Zofran	2
Pentamidine	Pentam, NebuPent	1
Phenylephrine	Neosynephrine	3
Pimozide	Orap	1
Procainamide	Pronestyl	1
Pseudoephedrine	PediaCare, Sudafed	3
Quetiapine	Seroquel	2
Quinidine	Quinaglute, Cardioquin	1
Risperidone	Risperdal	2
Salmeterol	Serevent	3
Sotalol	Betapace	1
Tacrolimus	Prograf	2
Telithromycin	Ketek	2
Terbutaline	Brethine	3
Thioridazine	Mellaril	1
Tizanidine	Zanaflex	2
Venlafaxine	Effexor	2
Ziprasidone	Geodon	2

Drugs in bold type are commonly used in perioperative period.
Drugs in italics type are commonly used in children.
^*Category 1: Drugs that are generally accepted by authorities to have a risk of prolonging the QT interval and causing Torsades de pointes.
Category 2: Drugs that may prolong the QT interval but at this time lack substantial evidence for causing Torsades de pointes.
Category 3: Drugs to be avoided for use in patients with diagnosed or suspected congenital long QT syndrome (in addition to drugs in categories 1 and 2).
A continuously updated and complete list of drugs that prolong QT, as well a list of drugs which do not prolong QT and are therefore safe in patients with long QT, may be found at www.torsades.org/medical-pros/drug-lists/drug-lists.htm#. (Accessed July 21, 2006.)