Prolongation of QT interval

Definition:

A cardiac abnormality in which the heart muscle takes longer than normal to recharge between beats.

The QT interval is a measurement made on an electrocardiogram, which is used to assess the electrical behaviour of the heart. It equates approximately to the time taken between the heart ventricles beginning to contract and when they finish relaxing. Prolongation of the QT interval means that the heart muscle takes longer than normal to prepare to contract. Excessive QT prolongation can trigger abnormal heart rhythms (tachycardia).

Prolongation of the QT interval is seen in a range of conditions. It can also be triggered by several drug treatments (including some antibiotics). For this reason, regulatory authorities typically require drug developers to provide data on a drug’s effects on the QT interval.