Implantable cardiac stimulation system providing autocapture and lead impedance assessment and method

An implantable cardiac stimulation system that provides autocapture and lead impedance assessment comprising:

• stimulation means for providing pacing stimulation pulses;
• lead means including a plurality of electrodes for providing a plurality of different electrode configurations;
• switch means for selectively coupling the stimulation means to any one of the plurality of electrode configurations;
• autocapture means for performing autocapture tests with the stimulation means coupled to a primary pacing electrode configuration, the autocapture means comprising capture detection means for detecting evoked responses during an autocapture test with the capture detection means coupled by the switch means to a current one of the plurality of electrode configurations different from the primary pacing electrode configuration;
• and
• impedance measuring means for measuring lead impedance of the current electrode configuration responsive to a failure to detect an evoked response during an autocapture test and causing the switch means to couple the stimulation means to an electrode configuration other than the current one of the plurality of electrode configurations if the measured impedance is outside a predetermined impedance range.

A method of performing an automatic capture test, the method comprising:

• performing the automatic capture test by applying a plurality of energy-varying pacing pulses to a chamber of a patient's heart using a first electrode configuration selected from a plurality of selectable electrode configurations;
• monitoring for evoked responses to each of the pacing pulses using a second electrode configuration different from the first electrode configuration;
• measuring an impedance value of the second electrode configuration responsive to a failure to detect an evoked response for a given one of the pacing pulses;
• and
• selecting an electrode configuration other than the second electrode configuration if the measured impedance value does not satisfy one or more predetermined criteria.

An implantable cardiac stimulation system comprising:

• a pulse generator providing primary pacing pulses and back-up pacing pulses;
• a lead system providing a first electrode configuration and a second electrode configuration;
• an autocapture circuit that, responsive to a primary pacing pulse provided using the first electrode configuration, detects an evoked response using the second electrode configuration and that, responsive to a failure to detect an evoked response, causes the pulse generator to provide a back-up pacing pulse;
• and
• an impedance measuring circuit that measures lead impedance during a back-up pacing pulse.