Pacemaker technology has rapidly advanced and leadless devices promise several advantages compared to conventional pacemakers. Leadless pacemakers (Figure 1) are designed to be implanted in the right ventricular (RV) septum or apex via a percutaneous procedure on a steerable catheter. Although rare, device dislodgement and embolization is a possibility that can cause an array of complications depending largely on the vessel/organ to which it embolizes. Steerable retrieval catheters have been designed and a retrieval protocol has been proposed, based on animal studies. We report a case of a leadless pacemaker embolization to the pulmonary artery and the potential difficulties with successful retrieval. Combining the theorized retrieval instructions with the experience of this case, we propose a retrieval protocol for future cases of leadless pacemaker embolization.
A 39-year-old male with a past medical history of type 2 diabetes, coronary artery disease, obesity, hypertension, chronic back pain, and seizure disorder presented with a witnessed syncopal episode. He was unconscious for several minutes and had no warning signs. No seizure-like activity was reported. The patient had previously undergone a cardiac ischemic workup and had a loop recorder placed for a prior syncopal episode. Loop recorder interrogation now showed a 3-second pause at the time of the syncopal episode. He was enrolled in the LEADLESS II investigational device exemption (IDE) study and underwent successful implantation of a leadless pacemaker per guidelines. Post implantation evaluation revealed an appropriately positioned device that was functioning normally. The patient was discharged the following day in stable condition. During his follow-up office visit a week later, he reported symptoms of chest pain and lightheadedness. Pacemaker interrogation revealed that the device was not sensing or pacing. Chest x-ray confirmed dislodgement and embolization of the pacemaker to the right lower pulmonary artery, and the patient was referred to an interventional cardiologist for device retrieval. The case was discussed in an interdisciplinary meeting involving an interventional cardiologist, electrophysiologist, cardiothoracic surgeon, catheterization laboratory staff, OR surgical staff, and experts from Abbott. A percutaneous retrieval strategy was formulated with surgical backup.
The patient was brought into the hybrid operating room and intubated after general anesthesia was administered. A pre-extraction pulmonary angiography was performed through a multipurpose catheter, ruling out any perforation or bleed (Figure 2 shows actual images of the pacer retrieval procedure and Figure 3 features a schematic of the sequence). An 18-30 mm EN Snare catheter (Merit Medical) was then advanced to capture the docking button on the leadless pacemaker. When the pacer was in the main pulmonary artery, another angiogram confirmed no perforation or vessel rupture, but did reveal an embolized branch of the distal vessel. The Nanostim Retrieval Catheter (NRC) (Abbott) was steered into the right atrium while the EN Snare, along with captured device, was retracted into the right atrium. Following the Nanostim device instructions for use (IFU), we next needed to switch the device from the EN Snare catheter to the NRC before retracting the device via the inferior vena cava (IVC). We released the device from the EN Snare, but before we could capture the device with the NRC, the pacemaker moved into the superior vena cava (SVC). The docking button was positioned toward the cranial aspect of the SVC, complicating plans to use the NRC. The EN Snare was used again and advanced up the SVC. We were able to successfully capture the leadless pacemaker by advancing the EN Snare loop over the body of the device and returned the device to the right atrium. On the second attempt, the pacer was released from the EN Snare and captured by the NRC. The NRC snare loop became fixed around the body of the device, and despite multiple attempts, we were unable to move the loop to the docking button or align the device in a coaxial fashion to the NRC. Plans to use the NRC were abandoned and the pacer pulled out of the NRC loop snare as the EN Snare loop was able to capture the docking button. The EN Snare catheter, along with the captured device, were withdrawn in an 18 French (F) sheath and retracted all the way to the hub. Since we had not used a Perclose system (Abbott Vascular) and the patient was heparinized, we decided to reintroduce a new sheath. The sheath with the embedded device was retracted 4 inches, nicked to introduce a 150 cm, .035-inch J wire, and a new 18F sheath was exchanged for later manual removal. The device was extracted from the sheath and sent to the company for analysis.
Twenty-four (24) hours post retrieval, an echocardiogram demonstrated normal left ventricular and right ventricular function, with no evidence of pericardial effusion. A computed tomography (CT) scan of the chest demonstrated a segmental occlusion of the right lower lobe pulmonary artery, likely representing a pulmonary embolus that developed further downstream to the device. The patient underwent successful implantation of a new dual-chamber (DDD) pacemaker later that week and was started on rivaroxaban for treatment of pulmonary embolism.
Unlike conventional pacemakers that require a more invasive surgery, leadless pacemakers are designed to be implanted via a percutaneous procedure. During traditional pacemaker implantation, acute and long-term complications can affect up to 10-12% of patients.1 The exclusion of a pacing lead, coupled with the small size and lack of a surgical pocket, improves patient comfort and can reduce traditional pacemaker complications, including device pocket-related infections and lead failure.1-4
Abbott’s Nanostim device (Figure 1A) was the first to be implanted in the United States in 2014. It is a single-chamber pacemaker that provides rate response based on changes in right ventricular core temperature and has an estimated battery life comparable to traditional pacemakers, with projected longevity between 10 and 17 years.3,4 Medtronic’s Micra device (Figure 1B) is also a totally self-contained leadless pacemaker system that was the first to be FDA approved in April 2016. It is also a single-chamber pacemaker that utilizes a 3-axis, accelerometer-based rate response and has a projected battery longevity between 4.7 and 12 years, depending on use conditions.5 The Nanostim device is designed to be implanted in the right ventricular septum or apex via the femoral vein with an 18F delivery catheter. The Micra is designed to be implanted with a 23F introducer. Abbott has designed single-loop and triple-loop retrieval catheters to facilitate Nanostim device retrieval and to enable removal for other reasons such as infection, need for device upgrade, and elevated thresholds. Although the occurrence of dislodgement is <1% and typically happens acutely, it is important to develop strategies to deal with this infrequent event.6 The NRC is deflectable and steerable, and has a single- or triple-loop snare that can be positioned independently from the retrieval catheter.7 For Micra retrieval, off-the-shelf snares are recommended for device removal, although the manufacturer recommends that devices that reach end of life should be turned off and a new device placed, rather than retrieved.5
This is one of the few reported cases of retrieval of an embolized leadless pacemaker. Based on this limited experience, we have developed a protocol for safe and effective percutaneous removal of an embolized pacer (Table 1). We suggest using a hybrid operating room with proper surgical backup and experienced personnel in the room. It is important to prepare for potential complications, including pulmonary artery perforation or laceration, pericardial effusion, IVC laceration, or right-sided valvular damage. If the Nanostim pacer is in the right atrium, SVC, or IVC, we suggest using the NRC. If the pacemaker is in the right ventricle, right ventricular outflow tract, the pulmonary artery, or its branches, the EN Snare system or the Goose Neck snare (Medtronic) should be used, depending on the operator’s experience with these systems. An embolized Micra leadless pacemaker may be approached similarly, but extra attention should be paid to the longer fixation tines in this device, which have the potential of damaging surrounding structures during withdrawal. In clinical trials for the Micra, there were no device embolization events; however, this remains a possible complication.5
Based on animal studies (ovine model)8, Abbott’s experts recommended retrieval of the pacer from the pulmonary artery into the right atrium using the EN Snare system and transfer to the NRC in the right atrium before withdrawing into the IVC and externalizing the device.7 However, based on our limited experience, we would recommend against this plan, because it is fraught with unnecessary risks. First, a freely mobile device in the right atrium could embolize to the SVC or another part of the heart in a far more difficult location and with an orientation that makes extraction harder. Secondly, during transfer, there is a risk of both snares getting stuck on the device, thereby necessitating a surgical rescue.
Our case is one of the few documented cases of leadless pacemaker retrieval from the pulmonary artery. The greater acceptance of leadless pacing technologies will increase the incidence of dislodgement and embolization of these devices. Interventional cardiologists should be well versed in retrieval techniques and assist electrophysiologists to safely manage potential complications. Protocols should be in place at each institution, along with retrieval equipment, to ensure patient safety.
- Mountfort K, Knops R, Sperzel J, Neuzil P. The promise of leadless pacing: based on presentations at Nanostim-sponsored symposium held at the European Society of Cardiology Congress 2013, Amsterdam, The Netherlands, 2 September 2013. Arrhythm Electrophysiol Rev. 2014 May; 3(1): 51-55. doi: 10.15420/aer.2011.3.1.51.
- Van Eck JW, van Hemel NM, Zuithof P, et al. Incidence and predictors of in-hospital events after first implantation of pacemakers. Europace. 2007;9: 884-889.
- Reddy VY, Knops RE, Sperzel J, et al. Permanent leadless cardiac pacing: results of the LEADLESS trial. Circulation. 2014 Apr 8; 129(14): 1466-1471.
- Knops RE, Tjong FVY, Neuzil P, et al. Chronic performance of a leadless cardiac pacemaker 1-year follow-up of the LEADLESS trial. J Am Coll Cardiol. 2015 Apr 21; 65(15): 1497-1504.
- Reynolds D, Duray GZ, Omar R, et al. A leadless intracardiac transcatheter pacing system. N Engl J Med. 2016 Feb 11; 374(6): 533-541. doi: 10.1056/NEJMoa1511643.
- Reddy VY, Exner DV, Cantillon DJ, et al. Percutaneous implantation of an entirely intracardiac leadless pacemaker. N Engl J Med. 2015; 373(12): 1125-1135.
- Sperzel J, Khairkhahan A, Ligon D, Zaltsberg S. Feasibility, efficacy and safety of percutaneous retrieval of a leadless cardiac pacemaker in an in vivo ovine model. Europace. 2013; 15(Suppl 2): 859.
- Koruth JS, Rippy MK, Khairkhahan A, et al. Feasibility and efficacy of percutaneously delivered leadless cardiac pacing in an in vivo ovine model. J Cardiovasc Electrophysiol. 2015 Mar; 26(3): 322-328. doi: 10.1111/jce.12579.
1Orlando Health Heart Institute, Orlando, Florida; 2Department of Internal Medicine Orlando Regional Medical Center, Orlando, Florida
Work was performed at Orlando Regional Medical Center, Orlando, Florida.
Disclosures: The authors report no conflicts of interest regarding the content herein.
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