Patent ID: 7643877

Claim:
An apparatus comprising: a test energy circuit adapted to deliver a test energy to a heart of a patient; a response signal circuit adapted to detect responding signals providing for an indication of an electric field strength in a predetermined cardiac region, the responding signals resulting from the delivery of the test energy; a controller in communication with the test energy circuit and the response signal circuit, the controller adapted to estimate a defibrillation threshold based on the indication of the electric field strength; a heart signal sensing circuit to sense intrinsic electrical heart signals from the heart of a patient; a ventricular tachyarrhythmia/fibrillation detector circuit, operatively coupled to the heart signal sensing circuit, the ventricular tachyarrhythmia/fibrillation detector circuit operable to detect a ventricular tachyarrhythmia/fibrillation, wherein the ventricular tachyarrhythmia/fibrillation detector circuit has a sensitivity and a specificity, and wherein the ventricular tachyarrhythmia/fibrillation detector circuit is configured such that the specificity exceeds the sensitivity; a defibrillation shock circuit, coupled to the ventricular tachyarrhythmia/fibrillation detector circuit, the defibrillation shock circuit configured to deliver a defibrillation shock in response to the detected ventricular tachyarrhythmia/fibrillation, the defibrillation shock selected to exceed the estimated defibrillation threshold; and a stimulation circuit, coupled to the heart signal sensing circuit, the stimulation circuit configured to deliver to the heart a stimulation at an energy level appropriate to evoke or assist in evoking a responsive heart contraction.