A case control study to identify and explore associations with sudden death and medications that can prolong the QT interval on the electrocardiograph.

Background: In England and Wales over 5000 people die each year with a sudden death of ill-defined or unknown cause. Aims: To explore the hypothesis that the use of drugs that can cause prolongation of the QT interval on the electrocardiograph are associated with an increased risk of sudden death from cardiac arrhythmia. Methods: A community based, matched case control study used post mortem and primary care datasets. Cause of death was most likely due to cardiac arrhythmia. 789 cases were matched to 2357 controls for age, sex and cardiovascular disease at the GP practices. The International Registry for Drug-Induced Arrhythmias “Arizona” classification was used to separate drugs according to strength of QT prolongation. Results: Conditions significantly associated with sudden death were used in the adjusted analysis. Overall risks were doubled for the registry drugs that were considered to pose the greatest risk but with considerable variation. The association with sudden death increased with concomitant use of registry drugs. Drugs used for psychiatric purposes were consistently strongly associated with sudden death. Conclusion: Arizona registry classification is a poor predictor of sudden death. The linkage of the general practice research database to mortality data has the potential for a much larger sample for further study