From the Guidelines
QT prolongation is a significant risk factor for dangerous arrhythmias like Torsades de Pointes, and medications such as antiarrhythmics, antipsychotics, antibiotics, antidepressants, antiemetics, and antimalarials can contribute to this condition, with women being at higher risk due to longer QT intervals than men. The risk of QT prolongation is increased in patients with certain medical conditions, such as heart disease, and electrolyte abnormalities, particularly low potassium, magnesium, or calcium levels [ 1 ]. According to the 2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death, QT-prolonging medications should not be used in patients with long QT syndrome unless there is no suitable alternative, and careful monitoring of the QTc during therapy is recommended [ 1 ].
Risk Factors for QT Prolongation
- Female gender [ 1 ]
- Hypokalemia [ 1 ]
- Bradycardia [ 1 ]
- Recent conversion from atrial fibrillation [ 1 ]
- Congestive heart failure [ 1 ]
- Digitalis therapy [ 1 ]
- High drug concentrations [ 1 ]
- Rapid rate of intravenous drug administration [ 1 ]
- Baseline QT prolongation [ 1 ]
- Ventricular arrhythmia [ 1 ]
- Left ventricular hypertrophy [ 1 ]
- Congenital long QT syndrome [ 1 ]
- Certain DNA polymorphisms [ 1 ]
- Severe hypomagnesemia [ 1 ]
- Concomitant use of 2 or more drugs that prolong the QT interval [ 1 ]
Medications that Can Contribute to QT Prolongation
- Antiarrhythmics: amiodarone, sotalol, procainamide [ 1 ]
- Antipsychotics: haloperidol, quetiapine, ziprasidone [ 1 ]
- Antibiotics: azithromycin, ciprofloxacin, clarithromycin [ 1 ]
- Antidepressants: citalopram, escitalopram [ 1 ]
- Antiemetics: ondansetron, domperidone [ 1 ]
- Antimalarials: chloroquine, hydroxychloroquine [ 1 ]
In patients with drug-induced QT prolongation, removal of the offending agent is indicated, and clinicians should obtain baseline ECGs, monitor QT intervals during treatment, maintain normal electrolyte levels, and consider alternative medications for high-risk patients [ 1 ].
From the FDA Drug Label
Because of the theoretical possibility of QT-prolonging effects that might be additive to those of quinidine, other antiarrhythmics with Class I (disopyramide, procainamide) or Class III activities should (if possible) be avoided Prolongation of the QTc interval is associated in some other drugs with the ability to cause torsade de pointes-type arrhythmia, a potentially fatal polymorphic ventricular tachycardia, and sudden death. Factors contributing to QTC prolongation (especially hypokalemia, hypomagnesemia, and hypocalcemia) should be sought out and (if possible) aggressively corrected
The medications that can contribute to QT prolongation are:
- Class I antiarrhythmics: disopyramide, procainamide
- Class III antiarrhythmics
- Ziprasidone 2
- Quinidine 3 Factors that contribute to QT prolongation:
- Hypokalemia
- Hypomagnesemia
- Hypocalcemia There is no information about the difference in QT prolongation between men and women.
From the Research
QT Prolongation in Men and Women
- Normal QTc intervals are typically <450 ms for men and <460 ms for women 4
- For every 10 ms increase in QTc interval, there is a ~5% increase in the risk of arrhythmic events 4
Risk Factors for QT Prolongation
- Patient-related risk factors include female sex, age >65 years, and uncorrected electrolyte disturbances 4
- Other risk factors include hypokalemia, drug-drug interactions, advancing age, genetic predisposition, hypomagnesemia, heart failure, and bradycardia 5
Medications that Can Contribute to QT Prolongation
- Many drug therapies are associated with prolongation of the QT interval, including dofetilide, a class III antiarrhythmic agent 6
- Diverse classes of medications are associated with QT interval prolongation, and clinicians can minimize adverse events by avoiding prescription of multiple medications associated with QT interval prolongation in high-risk patients 7
Monitoring and Management of QT Prolongation
- When the QTc interval is 470-500 ms for males, or 480-500 ms for females, or the QTc interval increases 60 ms or more from pretreatment values, dose reduction or discontinuation of the offending drug should be considered where possible, and electrolytes corrected as needed 5
- If the QTc interval is ≥500 ms, the offending drug should be discontinued, and continuous EKG telemetry monitoring should be performed, or the 12-lead EKG should be repeated every 2-4 hours, until the QT interval has normalized 5