Abstract: A noise discrimination circuit determines if sensed electrocardiographic (ECG) pulsed signals sensed within a pulse generator are valid ECG signals, i.e., valid P-waves or R-waves, or noise. The ECG signal may then be processed. The processed ECG signal is monitored to determine both the amplitude and duration of any signal pulses appearing thereon. If the amplitude of a given ECG signal pulse exceeds a prescribed threshold level for a prescribed time period, the pulse is considered to be a valid ECG signal. The noise discrimination circuit includes: a threshold detector for determining if the amplitude of the ECG signal exceeds the prescribed threshold level; a timer circuit for generating a timed window signal, triggered by the threshold detector whenever the ECG signal amplitude exceeds the prescribed threshold level; and logic circuitry for determining if the amplitude of the ECG signal remains above the threshold level for the duration of the timed window signal.

Abstract: A stylet for use with an implantable pacing lead and for checking purposes after this implantation. The pacing lead is a hollow elongated conductor including coiled wire forming continuous turns. The stylet comprises a flexible, straight filament and a blunting tip having an axially symmetrical shape. The rear end of the tip is provided with an axially symmetrical cavity at the bottom of which is secured the distal end of the filament. Upon insertion of the stylet in the conductor of an implanted pacing lead, for example for checking the correct connection of the conductor in the heart's tissue, the tip by virtue of its shape is prevented from catching in the grooves, existing between the turns of the coiled wire, as the style moves around bends formed in the conductor while it is in a blood vessel, thereby facilitating the insertion of the stylet.