Non-cardiac drugs that interfere with the electrical activity controlling the heartbeat are associated with a three-fold risk of sudden cardiac death, according to Dutch research published (Wednesday 11 May) in Europe's leading cardiology journal, the European Heart Journal.
In a study of 775 cases of sudden cardiac deaths and over 6,000 matched controls in the Netherlands the researchers found that the use of certain anti-psychotic and gastro-intestinal drugs listed on the website of the International Registry for Drug-induced Arrhythmias was probably responsible for 320 sudden cardiac deaths a year in the Netherlands and, by extrapolation, a total of around 15,000 in Europe and the USA.
The drugs involved are those that prolong the QTc interval in the heart. The QTc interval is the duration (as measured by electrocardiogram) of the electrical activity controlling contraction of the cells of the heart muscle. It is the measure of how long it takes to repolarize the myocardial cells in the heart, a process that is necessary before the heart can contract. Drugs that prolong the QTc interval can interfere with repolarization and cause life-threatening arrhthymias.
However, the report's senior author, Dr Bruno Stricker from the Erasmus Medical Center in Rotterdam, said that although these drugs did significantly raise the risk of sudden cardiac death it was important to keep the risk in perspective. The normal annual incidence of sudden cardiac death was one to two deaths a year per thousand of the population in the western world. This risk rises to around three per thousand per year in those taking the drugs.
"These drugs are vital treatments for serious conditions in many cases, so it is essential that patients should not stop taking them on their own initiative. If they are concerned they should talk to their doctor," said Dr Stricker, who is also working as senior medical officer at the Inspectorate for Healthcare The Hague.
The drugs examined were cisapride and domperidone (GI drugs), chlorpromazine, haloperidol and pimozide (anti-psychotics) and erythromycin and clarithomycin (antibiotics).
They have all previously been implicated in cardiac arrhythmia, but the new study is believed to be the first to evaluate the link between them and sudden cardiac death.
"The risk of sudden cardiac death was higher among recent starters (within around 90 days) and was significantly increased in users of GI medication and anti-psychotics," said Dr Stricker. "Past use was not associated with increased risk. Although the antibiotics have been reported to be linked to sudden cardiac death, we found no statistically significant increase in our study, although that may have been due to the limited number of cases."