Stepwise Progression and Successful Extraction of a Completely Transected EMBLEM S‐ ICD Model 3501 Lead

A 33-year-old man with an EMBLEM S-ICD (Model 3501) experienced complete lead transection. Despite preserved secondary-vector sensing, the lead was safely extracted using silk-suture extension and a Byrd sheath, illustrating stepwise lead injury and a simple extraction strategy. The Boston Scientific EMBLEM S-ICD electrode Model 3501 has been associated with rare but clinically significant lead fractures. In February 2021, the U.S. Food and Drug Administration issued a Class I recall after 27 reported cases. Fractures typically occur just distal to the proximal sensing electrode at a manufacturing notch and may progress to involve the defibrillation coils. The reported incidence is 0.2% at 41 months, with a 0.004% risk of life-threatening events at 10 years 1, 2. Although several cases have been reported, most involved partial fractures, and detailed descriptions of extraction of completely transected leads remain limited. We present the case of a 33-year-old man who underwent EMBLEM S-ICD (Model 3501) implantation for secondary prevention of ventricular fibrillation (month 0). Noise was detected on the secondary and alternate sensing vectors at routine interrogation 60 months after implantation (Figure 1), and the patient was initially followed conservatively. The device was programmed to the secondary vector, which remained in use until lead extraction, and system impedance was 85 Ω. Because the patient worked on a ranch, frequently performed repetitive upper-extremity tasks, and regularly engaged in upper-body strength training including push-ups, the noise was initially considered possibly related to myopotential interference. At 71 months after implantation, noise episodes became more frequent (Figure 1), prompting lead extraction and reimplantation; system impedance remained within the normal range at 75 Ω. Reproducibility of the noise with specific maneuvers was not systematically assessed. However, at approximately 71.5 months after implantation, the impedance increased to > 400 Ω. Device interrogation at 72 months after implantation (the day before the procedure) showed an electrically flat alternate vector, intermittent noise and partially flattened R waves on the secondary vector, and clear, stable R-wave detection on the primary vector (Figure 1). Preoperative chest X-ray showed abnormal angulation near the proximal sensing electrode, suggesting complete fracture (Figure 2A); however, because R-wave sensing was preserved on the secondary vector, a partial fracture was presumed. The extraction was performed under general anesthesia to ensure adequate analgesia and prevent patient movement during this relatively uncommon procedure. At the incision site around the proximal sensing electrode, the lead was found to be completely transected just distal to the proximal sensing electrode. The fracture was confirmed fluoroscopically (Figure 2B) and by direct visualization (Figure 2C). The lead was separated into proximal and distal fragments. The distal end was secured with a silk suture for extension, and a Byrd mechanical sheath (Cook Medical) was advanced for gentle blunt dissection of adhesions under counter-traction. The entire lead was successfully removed without complications (Figure 2D). A new lead was implanted 2 cm lateral to the original position, and the generator was replaced during the same procedure. The postoperative course was uneventful, and the patient was discharged in good condition. According to a manufacturer-issued medical device advisory, fractures of the Model 3501 electrode have been reported to occur immediately distal to the proximal sensing electrode, at a manufacturing notch created during assembly. This proposed mechanism is consistent with observations described in independent clinical reports 1. Because no proximal sensing conductor is present at this location, the primary vector may remain unaffected. Fracture progression first involves the distal sensing conductor. When the distal sensing conductor is compromised, the alternate vector can become electrically flat—alternate vector flatline (AVFL)—which has been described as an early indicator of fracture 1, 2. In addition, once the distal sensing conductor is transected and protrudes outside the lead to contact surrounding tissue, electrical repositioning occurs whereby the sensing field is effectively relocated around the fracture site; as a result, the secondary vector may record R waves resembling those of the primary vector (Figure 3A) 1, 2. While the defibrillation coil is not yet involved, the impedance remains stable. With further injury extending to the defibrillation coil, the impedance becomes abnormal. In the present case, although preoperative chest X-ray suggested complete fracture, we considered the lesion incomplete because R waves were still detected on the secondary vector. This apparently discordant finding is explainable by electrical repositioning. The concomitant presence of AVFL on EGM is also consistent with the reported mechanism (Figure 1) 1, 2. Moreover, the rise in impedance to > 400 Ω at approximately 71.5 months after implantation indicated progression of the injury. The patient worked on a ranch and frequently performed repetitive upper-extremity tasks. He also regularly engaged in strength training such as push-ups. These repetitive upper-body activities may have imposed mechanical stress on the lead, particularly at the vulnerable manufacturing notch, and contributed to the fracture. We illustrate the temporal course of lead injury. At 60 months after implantation, noise appeared on the secondary and alternate vectors while the system impedance remained stable (Figure 3B). At approximately 72 months after implantation, the impedance rose to > 400 Ω, at which time complete transection was present (Figure 3C). To our knowledge, this is the first report to depict the stepwise longitudinal progression of S-ICD lead injury in this manner. Finally, extraction of a completely transected lead may present additional technical considerations because continuous traction cannot be applied. In this case, proximal extension with a silk suture and blunt dissection using a Byrd mechanical sheath enabled safe, complete removal. This technique is simple, reproducible, and may be useful in similar cases. This case provides a rare longitudinal illustration of the progression of Model 3501 lead injury, from early electrical abnormalities to confirmed complete transection and successful extraction. We thank Yumetsugu Munakata for his assistance with the figures. This study was conducted according to the principles of the Declaration of Helsinki. The study was approved by the Institutional Review Board. The patients provided written informed consent. Dr. Kondo received lecture fees from Daiichi-Sankyo, Medtronic Abbott Medical Japan, Biotronik, Boston Scientific, and Japan Lifeline, and research funds from Daiichi-Sankyo and Boston Scieintific. Other authors have no conflicts of interest to declare. The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.