14-起搏器基本概念和起搏心电图阅图(祁述善).ppt

DDD/R modes have four types of blanking periods: A non-programmable atrial blanking period (varies from 50-100 msec) is initiated each time the atrium paces or senses. This is to avoid the atrial lead sensing its own pacing pulse or P wave (intrinsic or captured). In Thera and Kappa devices, this blanking period is dynamic, depending on the strength of the paced/sensed signal. The PVAB-(Post-Ventricular Atrial Blanking Period) is initiated by a ventricular pace or sensed event (nominally set at 220 msec) to avoid the atrial lead sensing the far-field ventricular output pulse or R wave. In dual-chamber timing, a non-programmable ventricular blanking period occurs after a ventricular paced or sensed event to avoid sensing the ventricular pacing pulse or the R wave (intrinsic or captured). This period is 50-100 msec in duration and is dynamic, based on signal strength. There also is a ventricular blanking period after an atrial pacing pulse in order to avoid sensing the far-field atrial stimulus (crosstalk). This period is programmable (nominally set at 28 msec). This blanking period is relatively short because it is important not to miss ventricular events (e.g., PVCs) that occur early in the AV interval. Ventricular blanking does not occur coincident with an atrial sensed event. This is because the intrinsic P wave is relatively small and will not be far-field sensed by the ventricular lead. The issue of ventricular safety pacing and cross-talk will be addressed later on in the presentation. A note of caution in programming long ventricular blanking periods after an atrial pace should be mentioned. If the ventricular blanking period after an atrial pace is excessively long, conducted ventricular events may go unsensed and cause the pacemaker to pace in the ventricle after the AV interval expires. This pace could occur before the ventricle has recovered from depolarization and may induce a ventricular arrhythmia (R on T phenomena). The total time that the atrial c