| 摘要 |
<p>A demand cardiac pacemaker of the type having circuitry for detecting the occurrence of natural heart activity. The sensitivity of the detecting circuitry is selectively and non-invasively altered via externally generated signals. In a preferred embodiment, the detecting circuitry establishes a first level representative of sensed extraneous repetitive noise and a second level greater in absolute value than the reference level by an amount representative of sensed heart activity. Circuitry differentially responsive to the difference between the reference and second level detects the occurrence of natural heart activity. The amount by which the reference and second level must differ to indicate natural heart activity is established by a bias circuit, the bias being alterable to establish one of a preselected plurality of sensitivities.</p> |
