What is happening during this device check?
This patient is a 73-year-old male implanted by a cardiologist in a different group for bradycardia approximately 5 weeks prior to this device check. The patient was establishing care with a new clinic. This was his first device check post implant. Multiple screen shots and testing data are provided to help determine what, if anything of concern is happening with this new implant. The patient denied any symptoms, but stated he didn’t feel much different after receiving the implant.
This EGM is a screenshot of the presenting/underlying rhythm freeze. There is not a surface ECG present. The first three complexes show normal sinus rhythm with 1st degree AV block. The last 4 complexes show atrial pacing with conduction at 300-324ms.
Does this look like a normal presenting rhythm?
The device check continued with the following impedance and sensing measurements evaluated.
The lead impedance measurements appear to be stable and within normal limits.
Sensing Measurements & Trends:
Atrial and RV sensing measurements are within range and have appropriate 2:1 sensitivity parameters programmed. It is noteworthy, however, to see that the p wave value at implant was 2.9 mV but is measuring >5.0mV today. It is also noteworthy that the R wave measurement at implant was just above 10.0mV (visible on the y-axis) but has dropped to 5.8-6.1mV since implant.
Capture threshold tests were performed next. During the testing, some of the paced complex morphologies were inconsistent. A 5-lead surface ECG was added.
EGM 2:
EGM 2: 5 lead surface ECG was added- Screenshot with surface- all paced complexes. Notice the morphology variation of the R wave on Lead I, as well as on leadless. The inconsistency of the paced PR intervals, and the alignment of the AP markers to what is shown on Lead I.
EGM 3:
EGM 3: Underlying rhythm freeze (DDI 30) with surface ECG. This looks normal.
EGM 4:
EGM 4: Atrial threshold test: AAI 90; 7.5V @1.5ms. Are we capturing? No! The A pace is falling into the T wave. Why is the ventricular rate increasing to the testing rate of 90bpm? Notice the first paced complex looks like it could be capturing- is the patient conducting after the first AP?
EGM 5:
EGM 5: Ventricular threshold test. VVI 90; 7.5v@1.5m. Notice the latency of the paced p waves in the circled intervals once the test ends (flagged as “programmed” in this example), or possible undersensing?
Answer:
The observations from this check were that the sensing had changed since implant, and undersensing was occasionally observed as shown in EGM 5. The thresholds were inconsistent, and it was not reasonable to conclude that the A and RV leads were capturing the chamber that they were pacing. Lead dislodgment was suspected, and the patient was referred for a stat consult with the electrophysiologist.
The patient was consented for a lead revision. The chest X-Ray at the lab prior to the procedure is shown below:
The chest X-ray done prior to opening the pocket showed that the leads appeared to be intact and not dislodged. Multiple lead tests through the programmer also showed appropriate capture thresholds and sensing. Testing was performed while the patient was supine, compared to seated upright in clinic. This suggested that the patient’s position could be affecting the testing values. EGMS from clinic were reviewed, and the physician decided to proceed with the revision.
Immediately upon opening the pocket, it was found that the lead suture sleeves were not anchored down appropriately, and the leads were sliding up and down freely in the vasculature. Given this finding, possible micro dislodgement of both leads was probable. Both leads were repositioned and secured with suture sleeves and appropriate anchoring implant technique. Lead testing was done through the pacing system analyzer, and all values were within normal range.
This was a unique device check in that a direct cause of the inconsistent findings could not be identified with routine testing. It was also a great reminder to put surface ECG on patients while testing their device as many times the intracardiacs can be deceiving. Sometimes it is difficult to pinpoint what is wrong, but to observe that something is not quite right.
