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Posted on 11.19.01
Drugs That Prolong the QT Interval: Why are They So Important?
By Nancy M. Allen LaPointe, PharmD
Drugs used to treat abnormal heart rhythms often change the electrical patterns within the heart, which can be seen and measured on an electrocardiogram (ECG). Sometimes these changes can be used to determine whether the medicine is effective or whether the dose is appropriate for a patient.
If the electrical patterns change too much, however, different and potentially dangerous abnormal heart rhythms may occur. To prevent these potentially dangerous side effects, the patient's ECG should be carefully monitored while taking antiarrhythmic drugs. The medicine or the dose then can be adjusted if needed.
One of these changes may be a lengthening of the QT interval on the ECG. The potential to prolong the QT interval is not limited only to drugs used to treat abnormal heart rhythms, such as quinidine or sotalol. In fact, many other medicines used to treat other diseases or disorders, such as infections or mental illnesses, can have this same side effect.
Sometimes the QT interval becomes prolonged when too high a dose of the medicine is used or if the medicine is combined with another drug that changes how the body processes the first drug. Because these other drugs are not being used to treat abnormal heart rhythms, however, many healthcare professionals may not think of this potential side effect and may not monitor the ECG.
Investigators in the Duke CERTs center are very interested in learning more about how healthcare providers use and monitor medicines that can prolong the QT interval on the ECG. The Duke CERTs is conducting several projects studying:
- how often these drugs are used,
- how well healthcare providers understand this potential side effect, and
- how well healthcare providers monitor for this potential side effect when starting one of the medicines that can prolong the QT interval.
Once these projects are completed, the Duke CERTs plans to develop an educational program for healthcare providers directed at areas identified by the research as needing improvement. Our goal is to assist healthcare providers in using these medicines more safely