• die at E10.5 of cardiac failure

• cardiac failure

• 6 of 275 suddenly died around 3-6 months of age, presumably because of fatal arrhythmias

• resting heart rate is lower

• some spontaneously develop polymorphous ventricular arrhythmias

• sudden accelerations in heart rate or premature beats cause lengthening of the action potential with early afterdepolarization and trigger arrhythmias

• increase in peak and late sodium current in cardiomyoctes

• ECG recordings show abnormal and variable myocardial propagation of the electrical pulse

• QT interval is prolonged by 55%

• T-wave is more prominent than in wild-type