Verification of capture by sensing evoked response across cardioversion electrodes

A cardiac pacemaker/defibrillator system comprising:

• a defibrillation lead system having at least two defibrillation electrodes adapted to be positioned in relation to a patient's heart;
• a pacing lead system having at least two pace/sense electrodes adapted to be positioned in relation to a patient's heart;
• sense amplifier means for sensing electrical depolarizations of the heart via said pace/sense electrodes and providing a sense detect signal in response thereto;
• pacing pulse generator means coupled to said pace/sense electrodes for providing pacing pulses to the heart in response to a trigger signal;
• pacer timing and control means operable in a pacing mode and responsive to said sense detect signals comprising means for timing escape intervals initiated in response to said sense detect signals and means for providing trigger signals to said pacing pulse generator means on expirations of said escape intervals;
• defibrillation shock generator means for providing defibrillation shocks across said defibfillation lead system;
• and
• defibfillation control means responsive to sense detect signals for controlling the operation of said defibfillation shock generator means;
• a system operable in a threshold determination operation for determining capture and loss of capture of the heart in response to test pacing pulse energy level comprising:
• means for coupling a threshold sensing electrode pair including at least one defibfillation electrode to the sense amplifier means;
• means for causing said pacer timing and control means to provide trigger pulses to said pacing pulse generator means for delivering test pacing pulses at a stimulation threshold test energy levels to the patient's heart through said pace/sense electrodes;
• means responsive to sense output signals provided by the sense amplifier means in response to the delivered pacing pulses when the stimulation threshold test energy level is sufficient to capture the heart for indicating capture of the heart;
• and
• means responsive to the absence of sense output signals provided by the sense amplifier means in response to the delivered pacing pulses when the stimulation threshold test energy level is insufficient to capture the heart for indicating loss of capture of the heart.

A cardiac pacemaker/defibrillator system operable in a threshold determination operation for determining a stimulation threshold of the heart, comprising:

• a defibrillation lead system having at least one defibrillation electrode adapted to be positioned in relation to a patient's heart;
• a pacing lead system having at least one pace/sense electrode pair adapted to be positioned in relation to a patient's heart;
• sense amplifier means adapted to be coupled to said pacing lead system for sensing occurrences of electrical depolarizations of the heart and providing a sense output signal in response thereto indicative of an occurrence of a depolarization;
• means responsive to said sense amplifier means for defining escape intervals following said sense output signals;
• means responsive to said defining means for delivering an electrical pulse to said patient's heart in response to an expiration of a said escape interval;
• means operable in a threshold determination operation for coupling a threshold sensing electrode pair including at least one defibrillation electrode to said sense amplifier means;
• pacing pulse generator means operable in the threshold determination operation for delivering pacing pulses at a stimulation threshold test energy level to the patient's heart through the pacing lead system and at least one pace/sense electrode;
• and
• means responsive to a sense output signal of the sense amplifier means for determining capture of the patient's heart by a pacing pulse delivered at the stimulation threshold test energy level.

A cardiac pacemaker/cardioverter system, comprising:

• a cardioversion lead system having at least one cardioversion electrode adapted to be positioned in relation to a patient's heart;
• a pacing lead system having at least one pacing electrode adapted to be positioned in relation to a patient's heart;
• first and second sense amplifier means for sensing electrical signals from said patient's heart;
• means for generating pacing pulses, coupled to said pacing electrode;
• means for detecting occurrences of tachyarrhythmia, coupled to said first amplifier;
• control means for defining a first operational mode during which said tachyarrhythmia detecting means is employed to detect occurrences of tachyarrhythmia and a second operational mode during which a threshold determination is made, said control system comprising means for triggering said pacing pulse generating means to deliver pacing pulses during said second mode;
• coupling means for coupling said at least one cardioversion lead to said first sense amplifier during said first operational mode and for coupling said at least one cardioversion electrode to said second sense amplifier means during said second operational mode;
• and
• capture detection means for detecting capture of said patient's heart during said second operational mode in response to electrical activity sensed by said second sense amplifier means.