The 2023 Canadian Cardiovascular Society Clinical Practice Update on Management of the Patient With a Prolonged QT Interval

A prolonged QT interval on the electrocardiogram is associated with an increased risk of the torsades de pointes form of ventricular arrhythmia resulting in syncope, sudden cardiac arrest or death, or misdiagnosis as a seizure disorder. The cause of QT prolongation can be congenital and inherited as an autosomal dominant variant, or it can be transient and acquired, often because of QT-prolonging drugs or electrolyte abnormalities. Automated measurement of the QT interval can be inaccurate, especially when the baseline electrocardiogram is abnormal, and manual verification is recommended. In this clinical practice update we provide practical tips about measurement of the QT interval, diagnosis, and management of congenital long QT syndrome and acquired prolongation of the QT interval. For congenital long QT syndrome, certain β-adrenergic-blocking drugs are highly effective, and implantable defibrillators are infrequently required. Many commonly prescribed drugs such as antidepressants and antibiotics can prolong the QT interval, and recommendations are provided on their safe use.