| 摘要 |
An implantable pacemaker (10) with apparatus for detecting capture or adjusting the strength or duration of pacing pulses by assessing (42) the mechanical evoked response that may be distinctly sensed through impedance sensing, pressure sensing, plethysmography or other suitable methods. When capture is to be detected or the strength or duration of the pacing pulses is to be adjusted, two pacing pulses are delivered to the heart in each cycle of a series of cardiac cycles. The first pulse is varied (138, 142) in strength or duration or both. The second pulse is maintained at a consistently high strength or duration to assure capture. The impedance of the heart is measured during a time window following the first pulse which is predicted to include a recognizable feature of the impedance waveform of the heart following a stimulating pulse. The magnitude of the first pulse is gradually changed until capture is lost. When the stimulation effect of the first pulse on the heart changes, the impedance measured during the window will change distinctly, indicating that a stimulus threshold has been detected.
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