P1-22

Understanding drug-induced torsades de pointes: a genetic stance

Drugs may produce a variety of arrhythmias, but drug-induced QT prolongation and the risk of the polymorphic ventricular tachycardia torsades de pointes (drug-induced long QT syndrome) has garnered the most attention. The wide array of drugs with potential for QT prolongation, the correspondingly large number of patients exposed to such drugs, the difficulty in predicting an individual's risk, and the potentially fatal outcome, make drug-induced long QT syndrome an important public health problem for clinicians, researchers, drug development programs, and regulatory agencies. This review focuses on the genetic risk factors and mechanisms underlying QT prolongation and proarrhythmia. The post-genomic era hints at an improved understanding (and prediction) of how the gene-environment interaction produces this particular adverse drug response.

Drug-induced long QT and torsade de pointes: recent advances

PURPOSE OF REVIEW

A wide array of drugs can cause marked QT prolongation with the associated risk of torsade de pointes. The large number of drugs with this potential, the correspondingly large number of patients exposed to such drugs, and the potentially fatal outcome make drug-induced long QT syndrome an important public health problem. This review focuses on mechanisms underlying QT prolongation and proarrhythmia, risk factors, including the role of genetic variants, and the unifying framework of reduced repolarization reserve.

RECENT FINDINGS

While most drugs that prolong the QT block a specific potassium channel, novel mechanisms altering protein trafficking have been discovered. The progression to torsade de pointes may be less related to degree of QT prolongation than to drug effects on transmural dispersion or variability of repolarization. Our understanding of certain predisposing risk factors has been further refined.

SUMMARY

Ongoing research continues to elucidate the mechanisms underlying drug-induced long QT syndrome. Importantly, studies are establishing improved predictors of risk for progression to torsade de pointes, in addition to the degree of QT prolongation, which is an imperfect predictor. Nonetheless, drug-induced long QT syndrome and torsade de pointes pose unique challenges for clinicians, researchers, drug-development programs, and regulatory agencies.