• authors state all mice die in utero, no specific time of lethality provided

• unlike human patients with a similar mutation, heterozygotes do not display sudden cardiac death (J:128657)

• significantly slower heart rate

• flecainide induced extreme sinus bradycardia and/or sinus arrest in 4 of 6 mice compared to 0 of 6 in wild-type controls

• epicardial mapping indicates slower conduction (increased activation time, reduced transverse conduction velocity) in the right ventricle but not in the left ventricle

• significant prolongation of the PQ interval

• increase in the flecainide-induced prolongation of the PQ interval compared to wild-type controls

• prolonged QRS duration

• increase in the flecainide-induced prolongation of the QRS interval compared to wild-type controls

• prolonged QTc interval

• more sinus pauses of longer duration

• however, no ventricular arrhythmias are detected

• prolonged action potential duration at frequencies less than 4 Hz and smaller dV/dt(max) at all frequencies tested

• ventricular myocytes show reduced peak sodium current densities and prolonged current decay half-life (at voltages from -45 to -25 mV) at room temperature

• upstroke velocity (dV/dt(max)) of the elicited action potential is reduced by 31% at -120 mV

• the current density of persistent sodium currents is significantly larger at voltages between -90 and -10 mV