Pacing channel isolation in multi-site cardiac pacing systems

DETAILED DESCRIPTION The present invention is therefore directed to reducing the blanking periods of sense amplifiers employed to sense a cardiac depolarization across a pair of pace/sense electrodes after delivery of a pacing pulse to the same or a different pair of pace/sense electrodes in at least a two site or chamber pacing system.
The present invention incorporates monolithic isolation circuit means comprising an output current loop coupled with a pair of pace/sense electrodes and an input current loop coupled to the sense amplifier inputs, the input and output current loops formed as integrated circuit conductors and functioning as isolated current replicators of sensed cardiac depolarizations.
In a multi-site or multi-chamber pacing system having N sense amplifiers in N sense amplifier channels, N-1 isolated current replicators are in circuit between the pace/sense electrodes and the sense amplifier inputs of up to N-1 sense amplifiers.
Preferably, each isolated current replicator is also in circuit between the pacing pulse generator and the pair of pace/sense electrodes of the channel.
The output current loop is coupled with the pair of pace/sense electrodes of the channel, and the input current loop is coupled with both the input of the sense amplifier and the output of the pacing pulse generator.
In this embodiment, pacing trigger pulses delivered to the input current loop are replicated in the output current loop and delivered to the pace/sense electrodes, whereas cardiac signals traversing the pace/sense electrodes and the output current loop are replicated in the input current loop and provided to the sense amplifier.
The input current loop and the output current loop are isolated from one another so that the output current loop and the components coupled therewith, including the pace/sense electrode pair of the pacing channel are uncoupled from the pacing circuitry and isolated from leakage currents accompanying delivery of a pacing pulse to a pace/sense electrode pair of another pacing channel