起搏心电图的解读及异常情况处PPT课件.pptVIP

* CorePace Module 4: Troubleshooting An intrinsic depolarization occurs in the atrium, but this depolarization is not sensed by the pacemaker. Therefore, the pacemaker sends an inappropriate pacing pulse to that chamber. Undersensing can be thought of as 搊verpacing. In this example, an AAI pacemaker is programmed to inhibit the atrial pacing pulse when a P-wave is sensed. Because the P-wave was not sensed, the pacemaker delivered an atrial pulse. If a pacemaker is undersensing, you will not see appropriate atrial sense markers on the marker channel. * CorePace Module 4: Troubleshooting Insulation breaks may cause undersensing if the insulation break results in the: Reduction of intrinsic beats at the sense amplifier Inability of the amplitude to meet the sensitivity requirement Conductor fracture may cause an open circuit. If intrinsic signals cannot cross the conductor fracture, undersensing will occur. The primary cause of conductor fracture is the chronic stress imposed on the lead as a result of its placement in the subclavian region, and may be reflected in increased impedance readings. During lead maturation, the pacemaker抯 sensitivity may be decreased 20？0%. (Steroid-eluting leads may eliminate the reduction in sensitivity by minimizing the growth of fibrotic tissue near the electrode). Lead dislodgment usually occurs early in the life of the pacemaker before the lead has fibrosed to endocardial tissue. The primary causes of lead dislodgment are: Inadequate initial positioning Patient movement (bringing arms overhead, etc.) Lead dislodgment occurs in approximately 2？% of pacemaker implants. Changes in the native signal may be caused by: Myocardial infarction Change in medications (not common) Electrolyte imbalance Undersensing may be caused by an inappropriately programmed setting. * CorePace Module 4: Troubleshooting If a pacemaker is oversensing, you will see signals on the marker channel that do not correspond to the ECG pattern. In this example,