When we look at the electrocardiograph of a person, there are various zones which are separated by even intervals. This indicates that there is no problem in the electrical conductivity of the heart and the functioning of the heart is smooth. However, in some people, either due to genetic reasons or due to acquired reasons, the electrocardiograph does not look normal. The QT interval is prolonged which indicates that some abnormality has been occurred in the electrical conductivity of the heart.
In severe conditions, it causes arrythmia which many a times proves fatal. The question is how there is a change in the QT interval. This may be due to genetic reason in which the genes responsible for ion regulation are mutated and the system goes abnormal. In acquired QT prolongation, the reason may be either the medication which may increase QT interval or the deficiency of calcium or potassium.
Drugs Causing QT Prolongation
There are various drugs causing QT prolongation. The physician must understand the side effect profile of the drug. If the drug induces QT prolongation, then proper screening of the patient is to be done in terms of electrolyte imbalance, cardiac arrest or chronic diarrheal conditions which may play their part in QT prolongation. The physician should also take care that the patient should not be administered more than 1 drug that causes QT prolongation. Further, the medicines which may interfere with the metabolism of drug having QT prolongation as side effect should be avoided. The drug causing kidney or liver damage should not be administered with drugs with QT prolongation ability.
The drugs which causes the QT prolongation includes antihistamine such as diphenhydramine, antibiotics such as clarithromycin and Gastrointestinal drug such as Cisapride. The other categories of drug may include antipsychotics, antimalarials, antiprotozoal and antidepressants.
Which Antidepressants Cause QT Prolongation?
Ventricular arrythmia is a serious condition and in severe conditions prove fatal. Certain medications may prolong the QT interval. The antidepressants such as citalopram, escitalopram, venlafaxine, desvenlafaxine, sertraline clomipramine and bupropion are among the drugs which are known for prolongation of QT interval. The administration of these drugs should be done after proper screening of the patients regarding their medical history and the concomitant administration of other drugs. The administration of these drugs should be periodically monitored.
Drugs are one of the largest contributors when it comes to; acquired prolong QT interval. Among various classes of drug causing QT prolongation as a result of side effect such as antihistamine, GERD drugs, antimalarials among others, antidepressant are generally known for their QT prolongation side effects.
QT prolongation risk varies within the antidepressant segment and the administration of the drug should be done by analyzing the risk involved. Almost all the SSRIs, except paroxetine have shown to be prolonging the QT interval.
The USFDA has issued a warning against the use of citalopram to the patients with the risk of prolong QT intervals as this drug may trigger this situation and may make it more serious. Although escitalopram does not increase the QT interval when compared to citalopram but caution with its use is recommended. The other drugs with higher risk include amitriptyline, venlafaxine and clomipramine. The drugs having low risk may include fluoxetine, sertraline, desvenlafaxine, and bupropion.
The administration of these drugs to the patients with risk of QT prolongation is regularly monitored and the monitoring should be done periodically.
Mechanism of QT Prolongation
QT prolongation occurs when there is abnormality in the ion regulation with in the heart. This abnormality does not allow the heart to perform function in normal manner leading to arrhythmia. QT prolongation occurs when there is a delay in ventricular repolarization, which is more when compared to normal delay. This leads to severe ventricular arrhythmia and the symptoms such as syncope and seizures began to develop. In certain cases, this arrhythmia proves fatal. Increased dispersion of polarization also plays an important role in triggering the ventricular arrhythmia.