Patent ID: 8565879

Claim:
An apparatus comprising: a cardiac signal sensing circuit configured to provide an electrical cardiac signal representative of cardiac activity of a subject; a therapy circuit configured to deliver electrical pacing stimulation energy to a heart of the subject; and a controller circuit communicatively coupled to the cardiac signal sensing circuit and the therapy circuit, and including a capture detection circuit configured to detect cardiac capture, wherein the controller circuit is configured to: initiate delivery of pacing stimulation energy to the heart using a first energy level; change the delivery of pacing stimulation energy level by at least one of: a) increasing the pacing stimulation energy from the first energy level until detecting that the pacing stimulation energy induces stable capture, or b) reducing the pacing stimulation energy from the first energy level until detecting that the pacing stimulation energy fails to induce the cardiac capture; and continue the changing of the pacing stimulation energy level until confirming the stable capture or the failure to induce the cardiac capture; wherein the controller circuit includes a safety margin calculation circuit configured to calculate a safety margin of pacing stimulation energy using at least one of: a determined stability of a parameter associated with evoked response; and a determined range of energy levels corresponding to intermittent failure to induce the cardiac capture, wherein the safety margin is indicative of a stimulation energy range between detected cardiac capture and stable cardiac capture, and wherein the controller circuit is configured to calculate a stimulation energy level for pacing therapy using the calculated safety margin and a stimulation energy level that induced cardiac capture.