Drug-induced QT prolongation
Drug-induced QT prolongation is a significant alteration in cardiac function, where the QT interval on an electrocardiogram (ECG) is extended beyond the normal range as a result of medication intake. The QT interval represents the time it takes for the heart's ventricles to depolarize and repolarize, essentially measuring the time from the start of the Q wave to the end of the T wave in the heart's electrical cycle. Prolongation of this interval can increase the risk of developing arrhythmias, particularly Torsades de Pointes (TdP), a potentially life-threatening condition.
Causes[edit | edit source]
Drug-induced QT prolongation can be caused by a variety of medications, including but not limited to certain antibiotics, antidepressants, antipsychotics, and antiarrhythmic drugs. The mechanism behind this adverse effect often involves the blockade of the hERG (human Ether-à-go-go-Related Gene) channel, which is crucial for cardiac repolarization. By inhibiting this channel, drugs can inadvertently prolong the QT interval.
Risk Factors[edit | edit source]
Several factors can increase the risk of drug-induced QT prolongation, including:
- Female gender
- Advanced age
- Existing heart conditions
- Electrolyte imbalances, particularly low levels of potassium or magnesium
- Concurrent use of multiple medications that prolong the QT interval
Symptoms[edit | edit source]
In many cases, drug-induced QT prolongation is asymptomatic. However, when symptoms do occur, they may include:
- Palpitations
- Fainting (syncope)
- Seizures
In severe cases, it can lead to Torsades de Pointes (TdP), a specific type of ventricular tachycardia that can degenerate into ventricular fibrillation and sudden death.
Diagnosis[edit | edit source]
Diagnosis of drug-induced QT prolongation involves a thorough medical history, medication review, and an ECG. The QT interval is measured, and if prolonged, the offending medication may be identified and discontinued.
Management[edit | edit source]
Management of drug-induced QT prolongation primarily involves:
- Discontinuation of the offending medication
- Correction of electrolyte imbalances
- Close monitoring of the QT interval
In some cases, alternative medications that do not affect the QT interval may be prescribed.
Prevention[edit | edit source]
Prevention strategies include:
- Careful selection of medications, especially in patients with known risk factors
- Regular monitoring of the QT interval in patients taking medications known to cause QT prolongation
- Avoiding the concurrent use of multiple QT-prolonging drugs
See Also[edit | edit source]
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Contributors: Prab R. Tumpati, MD