Different molecular types of long-QT syndrome

Prolongation of the QT interval in the electrocardiogram
results from an increase in the duration
of the cardiac action potential (1). The
normal potential lasts about 300 ms (phases 1
and 2). The resting membrane potential (phase
3) is reached by progressive inactivation of calcium
currents and increasing depletion of
potassium currents, which repolarize the cell.
In phase 0 the cell is quickly depolarized