Vector switching in an implantable cardiac stimulus system

A method of cardiac signal analysis in an implantable cardiac treatment device, the implantable cardiac treatment device including at least first, second and third electrodes coupled to operational circuitry for the device, the method comprising:

• configuring the device by sensing signals using at least first and second sense vectors defined by first and second pairs of electrodes chosen from the first, second and third electrodes;
• calculating signal metrics for the first and second vectors;
• and selecting a default sense vector by analysis of the signal metric;
• using the default sense vector for sensing of cardiac signals;
• analyzing a first signal captured from the default sense vector to determine whether:
• a normal sinus rhythm has been sensed;
• an arrhythmia has been sensed;
• or
• ambiguity is present;
• and
• determining that ambiguity is present and selecting a different sense vector from the default sense vector and analyzing a second signal captured from the different sense vector in order to resolve the ambiguity.

A method of operating an implantable electrical cardiac treatment device having operational circuitry for performing cardiac performance evaluation and treatment and at least first, second and third electrodes configured for implantation in a patient and coupled to the operational circuitry, the method comprising:

• observing a sensing metric for selected pairs of the first, second and third electrodes;
• identifying a default electrode pair for use in evaluation of cardiac signals using at least the sensing metric;
• identifying a second best electrode pair for use in evaluation of cardiac signals;
• analyzing a first signal captured using the default electrode pair and determining whether:
• the first signal indicates a normal sinus rhythm;
• the first signal indicates a particular arrhythmia;
• or
• the first signal indicates ambiguity;
• and
• determining that the first signal indicates ambiguity and, in response thereto, analyzing a second signal captured using the second best electrode pair.

A method of cardiac signal analysis in an implantable cardiac stimulus device, the device including a canister and a lead assembly, the lead assembly including a plurality of electrodes thereon and the canister including at least one electrode thereon for use in cardiac activity sensing, the method comprising:

• identifying a first electrode pair that defines a first sensing vector for default usage when observing cardiac activity of the patient;
• attempting to form a template representative of normal sinus rhythm for the patient using the first sensing vector after the first electrode pair has been selected for default use;
• failing to form the template representative of normal sinus rhythm using the first sensing vector and, in response thereto,
• changing the default electrode pair to a different pair of electrodes defining a sensing vector other than the first sensing vector;
• wherein:
• the first electrode pair is identified for default use on the basis of having a better cardiac signal metric when compared to other available sense vectors and, within the step of changing the default electrode pair, the different pair of electrodes is selected on the basis of having a better cardiac signal metric than at least all other available sense vectors except the first electrode pair.