first shock electrode 16 intended to be placed in the right ventricle and constituting e g the negative terminal for application of the potential voltage of defibrillation or cardioversion this ventricular shock electrode 16 is connected by a connection conductor 18 on a connection terminal 20 to the generator advantageously a terminal of the df 1 standard type probe 10 also carries at its distal part 12 a second shock electrode 22 which is known as a u201c supra ventricular u201d an electrode intended to be positioned in the high vena cava for application of a shock to the atrium this supra ventricular shock electrode 22 is connected by connection conductor 24 on connection terminal 26 to the generator preferably also with a df 1 standard connector probe 10 is also equipped with an extremity electrode 28 which is a detection stimulation electrode intended to be positioned at the bottom of the right ventricular cavity this electrode 28 is connected by a conductor 30 on a connection terminal 32 to the pacemaker advantageously with an is 1 connector standard as shown in fig4 conductor 30 is a hollow conductor e g a conductor internally wound having in its center a lumen 34 that allows introduction of a stylet for the guidance of distal extremity 12 by a physician.