Rate initialization and overdrive pacing for capture threshold testing

A cardiac device, comprising:

• pacing circuitry for delivering pacing pulses to a cardiac chamber;
• sensing circuitry configured to detect cardiac events;
• a controller operatively coupled to the pacing circuitry and the sensing circuitry;
• the controller configured to determine from the detected cardiac events a number of intrinsic and/or fusion beats and count the number of intrinsic and/or fusion beats over a plurality of cardiac cycles;
• the controller further configured to set a capture threshold test (CTT) pacing rate for a capture threshold test (CTT), wherein the capture threshold test (CTT) pacing rate is set higher if the number of counted intrinsic and/or fusion beats reaches a predetermined threshold while limiting the capture threshold test (CTT) pacing rate from going beyond a predetermined maximum pacing rate;
• and
• the controller further configured to initiate a capture threshold test (CTT) at the capture threshold test (CTT) pacing rate by delivering pacing pulses to the cardiac chamber using the pacing circuitry.

A cardiac device, comprising:

• pacing circuitry for delivering pacing pulses to a heart chamber;
• sensing circuitry configured to detect cardiac signals that include indications of cardiac events during a plurality of cardiac cycles;
• and
• a controller coupled to the pacing circuitry and the sensing circuitry, the controller configured to count a number of intrinsic beats in the cardiac events, the controller further configured to set a capture threshold test (CTT) pacing rate for a capture threshold test (CTT), wherein the capture threshold test (CTT) pacing rate is set at a first pacing rate if the number of intrinsic beats in the cardiac events does not go beyond a predetermined threshold and the capture threshold test (CTT) pacing rate is set higher at a second pacing rate if the number of intrinsic beats in the cardiac events goes beyond the predetermined threshold;
• and
• the controller is further configured to initiate a capture threshold test (CTT) at the capture threshold test (CTT) pacing rate by delivering pacing pulses to the heart chamber using the pacing circuitry.