Device Interrogation:
This EGM is of an RV capture threshold test. The RV lead was implanted in 1994, and a note in the patient’s device states the patient is dependent.
What is the RV threshold?
Answer:
The RV bipolar EGM displays a very narrow evoked response corresponding to each VP marker.
At 1.5V, the complexes change, suggesting a potential loss of capture.
The test was repeated with the inclusion of a surface ECG.
What is your assessment of the capture threshold after seeing this EGM?
Answer:
- The RV capture threshold is 2.25V @ 1.0ms.
- Lead 1 is positive, therefore confirming RV capture and not LV.
- Why are there R waves on the RV Bipolar channel when there is clearly no capture?
- The signal that is present on the RV channel is pacing artifact. We know that the patient is dependent, so it cannot be an intrinsic signal, and the surface ECG shows no capture and no R wave corresponding to the pacemaker impulse.
- The examples shown here demonstrate the importance of surface electrograms when testing patients. Given the age of the RV lead in this example, and the fact that the patient is pacemaker dependent, it is even more important to confirm that the device is programmed with appropriate 2:1 pacing safety margins.
Would you have reported the threshold as 1.75V @ 1.0ms prior to seeing the test with surface ECG?
Notice that the last technician that did the check 7 months prior did.
