| 摘要 |
<p>A novel rate responsive pacemaker using isovolumic contraction time (IVCT) as a control signal responsive to metabolic demands is disclosed. This control signal is injected into the timing circuit of a standard rate adaptive pacemaker to enhance the pacer's ability to respond in direct relation to the patient's changing metabolic needs as he performs his daily activities. A typical configuration using either right or left heart IVCT for rate control is described, in which the pacing rate is determined by the duration of IVCT. Since pacing rate and IVCT are linearly related, a simple conversion factor can be used to transform the duration of IVCT into the duration of the pacemaker escape interval (pacing rate). Although both right and left heart IVCT could be used for rate control, for the sake of simplicity only the right heart parameters are described herein. The device is capable of operating in most of the available modes (VVIR, DDDR, DDIR, AAIR), and has provisions for multiprogrammability, data storage, bidirectional telemetry, among other standard functions. The device has two inputs to measure IVCT: one, signaling the onset of mechanical activation of the ventricle (start of IVCT), and another, signaling the onset of ejection (end of IVCT). The time interval between these two signals is the duration of IVCT, which is processed by the pacemaker to determine the escape interval, through a simple conversion algorithm, analogous to what is available in the prior art. Onset and end points of IVCT are detected by any combination of biological sensors in the form of pressure, volume or flow transducers. <IMAGE></p> |
