Abstract
Case Summary
A patient presents with symptomatic bradycardia and high-grade atrioventricular block and receives a dual-chamber pacemaker with left bundle branch area pacing lead. Post procedure, there is concern for dislodgement of the ventricular lead after an electrocardiogram shows a missing ventricular paced beat. After additional device interrogation and review of the device manufacturer algorithms, it was determined that what was thought to be loss-of-capture or loss-of-sensing was coincidental artifact and normal device function.
Take-Home Messages
The highest risk for pacemaker lead dislodgement is immediately after implantation, and a 12-lead electrocardiogram should be reviewed post implantation. Understanding device manufacturer algorithms can help interpret unusual artifacts and findings in paced rhythms.
Key Words: electrocardiography, pacemakers
Graphical Abstract
Case
A 70-year-old woman presents with left-sided chest pain and is found to be in 2:1 atrioventricular (AV) block with right bundle branch block pattern. She was admitted to the intensive care unit for hypertensive urgency and symptomatic bradycardia and found to have no signs of myocardial ischemia. A dual-chamber pacemaker was implanted (Medtronic Azure S DR) with a left bundle branch area pacing lead (3,830 lead implanted in the septum near the inferior left bundle branch) and an atrial lead (5,076 stylet-driven lead implanted into the right atrial appendage). The device was programmed to managed ventricular pacing, with a lower rate of 60 and upper rate of 130, with sensed AV delay of 150 ms and paced AV delay of 180 ms. The paced rhythm is shown (Figure 1).
Figure 1.
12-Lead Electrocardiogram
Electrocardiogram obtained immediately after implantation of dual-chamber pacemaker.
What is the cause of the observed finding?
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A.
Loss of atrial sensing
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B.
Loss of ventricular sensing
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C.
Normal device functioning
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D.
Lead dislodgment with failure to pace the ventricle
Discussion
The underlying cause is C. The ECG (Figure 1) demonstrates an example of an atrial-sensed, ventricular paced rhythm with a single missing ventricular pace after a normally timed sinus P wave, followed by a short-coupled atrial-pace and ventricular-pace event. The predominant ventricular paced morphology has an RSR’ pattern in lead V1, with left axis deviation, suggesting capture of the left posterior fascicular region, consistent with conduction system pacing. Notably, the high amplitude of the pacing artifact suggests that the right ventricular lead is configured unipolar.
The crux is the missing ventricular paced beat after the sixth P-wave. Of most concern is failure of ventricular pacing, potentially through lead dislodgement leading to loss of atrial sensing or loss of ventricular capture, or may indicate ventricular oversensing of electromagnetic interference leading to pacing suppression. The short-coupled sequential pacing event also provides a clue, and could represent noncompetitive atrial pacing, which occurs after a P-wave falls into the postatrial ventricular blanking period, delaying the subsequent atrial paced event up to 30 ms before the next lower rate scheduled ventricular paced event. After the sixth P-wave, there is a low-amplitude signal that is seen on leads V1, II, and V5, and the augmented precordial leads, that lies in the sensed AV delay from the sensed P-wave and is on time, although discrete in amplitude and morphology from prior ventricular pacing signals. This may represent failure to sense the prior atrial signal, and thereby pacing into the refractory period, or some change in ventricular pacing output. Notably, there is a similar signal preceding the subsequent P-wave, which appears identical to the other sinus P waves.
Medtronic pacemakers will perform managed ventricular pacing in an attempt to avoid ventricular pacing and the device will schedule a switch from DDD to ADI.1 If a sensed ventricular beat is not seen in the search window, it will deliver a safety pace, consisting of an atrial paced beat followed by ventricular back-up pacing 80 ms afterward, as seen in Supplemental Figure 1 as the device reverts back to DDD. The presumed low-amplitude “pacer spike” was deemed an external artifact,2 supported by the difference in amplitude from unipolar ventricular pacing, and the missing annotation arrow from the ECG that was present for all other pacing events.
Funding Support and Author Disclosures
The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
Footnotes
The authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the Author Center.
Appendix
For a supplemental figure, please see the online version of this paper.
Appendix
References
- 1.Gillis A.M., Pürerfellner H., Israel C.W., et al. Reducing unnecessary right ventricular pacing with the managed ventricular pacing mode in patients with sinus node disease and AV block. Pacing Clin Electrophysiol. 2006;29(7):697–705. doi: 10.1111/j.1540-8159.2006.00422.x. [DOI] [PubMed] [Google Scholar]
- 2.Clifford G.D., Azuaje F., Mcsharry P. ECG statistics, noise, artifacts, and missing data. Adv Methods Tools ECG Data Anal. 2006;6(1):18. [Google Scholar]
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