| 摘要 |
An implantable cardiac stimulation device is provided which alters the stimulation regime during determination of a capture threshold level. In order to avoid the potential for fusion beats which would interfere with a capture threshold level determination, a two-fold approach is used. First, the atrial refractoriness of the atrium of the patient's heart is extended by supplying a secondary atrial stimulation pulse during a prescribed time period following delivery of a primary atrial stimulation pulse. Second, the atrium is overdriven by providing an atrial stimulation pulse at a rate in excess of the intrinsic heart rate. Accordingly, the potential for fusion beats is significantly decreased and the reliability of the determined capture threshold level is increased. In a preferred embodiment, two closely placed stimulation pulses, i.e., a first primary atrial stimulation pulse and a secondary atrial stimulation pulse, are provided to an atrium of the patient's heart, and a second primary atrial stimulation pulse set to a test level is delivered faster than the heart's intrinsic rate. During this pacing regime, the potential for fusion beats is decreased and accordingly, sensing the presence or absence of evoked responses can accurately determine the capture threshold level.
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