QTc is a measurement of the electrical activity linked to the contraction of heart muscle cells.
Drugs that increase the QTc interval can cause life-threatening disruptions of heart rhythms.
Dr Stricker and colleagues from the Netherlands assessed the association between the use of non-cardiac QTc-prolonging drugs and the risk of sudden cardiac death.
The researchers performed a population-based case-control study in the Integrated Primary Care Information project, a longitudinal observational database.
The team reviewed the complete medical records from more than 500 000 persons and all deaths between 1995 and 2003.
|The 7 drugs studied are likely to be responsible for 320 of the 775 sudden deaths|
|European Heart Journal|
Sudden cardiac death was classified based on the time between onset of cardiovascular symptoms and death.
For each case, the researchers matched up to 10 random controls for age, gender, date of sudden death and general practice.
The exposure of interest was the use of non-cardiac QTc-prolonging drugs.
Of the 7 drugs studied, 2 included the antibiotics erythromycin and clarithromycin.
Others on the risk-list are cisapride and domperidone, which are used to treat gastro-intestinal conditions, and the anti-psychotic medications chlorpromazine, haloperidol and pimozide.
The researchers categorized the exposure at the index date into 3 mutually exclusive groups of current use, past use, and non-use.
The team reported that the study population comprised 775 cases of sudden cardiac death and 6297 matched controls.
The research team found that current use of any non-cardiac QTc-prolonging drug was associated with a significantly increased risk of sudden cardiac death.
The 7 drugs studied were likely to have been responsible for 320 of these deaths, equating to about 1200 deaths in the UK and 15,000 across Europe and the US.
The drugs were found to interfere with the electrical activity controlling the heartbeat, increasing the risk of sudden death due to cardiac arrest by 3 times.
The team observed that the risk of death was highest in women, older patients and in recent starters of less than 90 days.
Dr Stricker concludes, “The use of non-cardiac QTc-prolonging drugs in a general population is associated with an increased risk of sudden cardiac death.”
"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, but talk to their doctors.”