Delayed Pacemaker Erosion due to Electrode Seal Defects

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1 Delayed Pacemaker Erosion due to Electrode Seal Defects Joseph D. Cohn, M.D., Rajendar Santhanam, M.D., Micki A. Rosenbloom, and Robert F. Thorson, B.S. ABSTRACT Over a 7-year period, follow-up data were available on 163 patients who underwent 209 pacemaker-related operations for initial insertion or revision of previously implanted units. During the follow-up period, 16 pacemaker generator units were removed from 12 patients solely because of the development of local skin erosion. This represents a 7.7'/0 incidence of pacemaker generator erosion. Three units were removed within a &month interval following pacemaker implantation and were associated with positive bacterial cultures, thereby indicating an infectious cause. Findings at removal of the remaining 13 pacemaker generators included extensive fibrosis with chronic inflammation, fibroblastic proliferation, and granulation tissue, which was most prominent at the site of insertion of the pacemaker lead into the pacemaker generator unit. Granulation tissue frequently led from this area to the area of skin attenuation and erythema. Inspection of the pacemaker generator units and electrodes demonstrated fluid ingress and tissue ingrowth toward the electrode due to inadequate seal mechanisms. Inadequate seal design of the pacemaker generator and electrode junction leads to tissue ingrowth with fibroblastic proliferation, chronic inflammation, and eventual pacemaker erosion. Extension of pacemaker generator longevity through the use of lithium batteries and nuclear energy sources has led to improved acceptance of artificial pacemaker generating units in the treatment of a wide variety of rhythm disturbances. Long-term implants of pacemaker generating units have, however, become associated with specific failure modes related to electrical components and pacemaker lead construction. Late erosions have been documented on rare occasions and are usually attributable to From the Department of Surgery, Saint Bamabas Medical Center, Livingston, NJ. Accepted for publication Jan 11, Address reprint requests to Dr. Cohn, Saint Bamabas Medical Center, Livingston, NJ local trauma. Occasionally, and during prospective evaluation, a design-related cause for pacemaker erosion has been documented [13.* The appearance of late pacemaker erosion prompted the development of a surveillance program to define related causative factors. Methods During the 7-year period from 1971 through 1977, follow-up data were available for 163 patients who underwent 209 pacemaker generator insertions or revisions of previously implanted units. Several different pacemaker generator units and lead configurations were employed, and selection was based on patient requirement, availability, and current technology. Follow-up examinations were performed every 4 months during evaluation of pacemaker generator electronic function. During the follow-up period, 16 pacemaker generator units were removed from 12 patients solely because of local skin erosion caused by the pacemaker. Pacemaker erosion occurred from 1 to 36 months following insertion and resulted in frank skin necrosis with extrusion of the pacemaker generating unit in four instances and localized skin induration, erythema, and tenderness without extrusion in twelve others. Thus, 16 pacemaker generator units were removed, representing an incidence of pacemaker generator erosion of 7.7%. During this time, implantation of pacemaker models 301UD, 401BD, and 602B (Cardiac Pacemakers, Inc.) were utilized on 107 occasions or 51%. Eleven erosions were observed in this patient group, representing an incidence of erosion of 10.3%. Additional units implanted included Medtronic 5942, Medtronic 5842, Xytron 5950, Biotronik IDP44, Intermedics 251, Intermedics 223A, and Arc0 LI-3D. A summary of the late pacemaker generator erosions is given in the Table. *Cardiac Pacemakers, Inc: Personal communication, by Joseph D. Cohn

2 446 The Annals of Thoracic Surgery Vol 28 5 vember 1979 Clinical Data for the 16 Patients Who Had Pacemaker Generator Erosiona Symptom Patient Onset after Ulceration. Implanatation Pacemaker through Skin Culture 1 23 mo CPI 301UD growth 2 11 mo CPI 301UD Scant staphylococcus 3 8 mo Scant Staphylococcus aureus mo 2 wk Intermedic 223A Staphylococcus aureus 6 31 mo mo 19 mo 30 mo 12 mo 35 mo 2d Biotronik IDP44 Biotronik IDP44 Biotronik IDP44 CPI 301UD Staphylococcus epidermidis Scant Staphylococcus epidermidis, Staphylococcus aureus Staphylococcus aureus 13 5d Staphylococcus aureus, gramnegative bacilli mo 7 mo 4 mo Medtronic 5942 CPI 6028 growth asymptoms and findings include erythema, induration, and fluid accumulation within the pacemaker generator site. Loose fitting electrode leads were commonly noted on pacemaker removal. Histological examination in eight instances revealed focal necrosis, granulation tissue, and chronic inflammatory changes. CPI = Cardiac Pacemakers, Inc. The 16 pacemaker generator units that were removed because they were causing skin erosion were evaluated by visual inspection and by electronic function analysis. Lead function was assessed. Culture specimens were obtained from the pacemaker pocket, and multiple biopsies of pacemaker pocket tissue were examined histologically. Case Reports Patient 2 A 64-year-old man was admitted for pacemaker replacement because of imminent erosion. Pacemaker insertion had been performed 14 months previously because of syncope associated with bradycardia. The implanted pacemaker system consisted of a model 301UD, which is a unipolar pacemaker generator unit (serial no ), and a unipolar lead (serial no LC), both manufactured by Cardiac Pacemakers, Inc. During the 3 months prior to admission, the patient noted induration and erythema over the medial superior corner of the pacemaker. He was treated conservatively with antibiotics and warm compresses, without improvement. Because of progression of these symptoms, it was elected to implant a new pacemaker generator unit and electrode on the opposite chest. Consequently, an Arc0 unipolar pacemaker generator unit, model LI3D (serial no. D33132C) was implanted utilizing an Arc0 unipolar endocardial electrode model 2HP (serial no. N711). The previously implanted Cardiac Pacemakers, Inc., pacemaker generator unit was removed. Examination of the insertion of the endocardial lead into this pacemaker demonstrated a loose fit between the Silastic endocardial lead and the epoxy channel of the pacemaker generator unit.

3 447 Cohn et al: Pacemaker Erosion From Electrode Seal Defects Fig 1. The pacemaker generator unit removed from Patient 2 demonstrates the presence of an incomplete seal along the epoxy channel of the pacemaker generator unit. The arrow indicates the position of this seal along the Silastic endocardial lead. This is incorporated in the lead design in an attempt to prevent fluid accumulation within the epoxy channel. However, tissue fluid can be seen adjacent to the electrode and within the pacemaker channel as a result of the incomplete seal. Figure 1illustrates the explanted unit and the endocardial electrode. A continuous air interface can be seen extending across the thin, expanded portion of the Silastic lead, which is designed to act as a barrier to fluid accumulation at the electrode connection site. Bloody fluid and tissue debris were noted to track from this area to the subcutaneous tissue adjacent to the area of skin erythema. Histological examination of biopsy tissue demonstrated edematous granulation tissue, focal necrosis, and young fibroblastic proliferation at areas adjacent to the electrode insertion site. More peripherally, fibrosis and mild chronic inflammatory changes were present. There was no evidence of foreign body giant cell reaction (Fig 2). Fig 2. Biopsy of pacemaker lining tissue from Patient 2 demonstrates fibroblastic proliferation, edematous granulation tissue, and dense fibrosis adjacent to the pacemaker lead insertion site into the generator unit. In addition, this granulation tissue associated with mild chronic inflammatory changes extended from the area of the lead insertion toward the area of imminent erosion on the skin surface. ( H b E ; original magnification X430.j Skin attentuation was also noted over these areas. In addition, considerable induration was present over the anterior surface of the subcutaneous tissue adjacent to the pacemaker generator unit. The initial implantation had consisted of a bipolar pacemaker generator unit, model 401BD (serial no ) by Cardiac Pacemakers, Inc., and a bipolar Medtronic enpatient 4 docardial electrode (serial no MA). An 86-year-old man, was admitted for evaluaupon removal of the pacemaker unit, necrotic tion of erosion of an indwelling pacemaker material was noted to originate at the insertion generator unit. Pacemaker insertion had been of both leads into the pacemaker generator unit, performed 2 years previously for heart block. with granulation tissue extending to the subduring the past several months, he noted cutaneous tissue and with adjacent skin erythema and induration over the lateral erythema. The entire pacemaker pocket was superior and inferior margins of the pacemaker. edematous and indurated. Biopsy of the sur-

4 448 The Annals of Thoracic Surgery Vol 28 5 vember 1979 Fig 3. Model 401BD (serial no ), Cardiac Pacemakers, Inc., bipolar pacemaker generator unit removed from Patient 4. Examination demonstrates marked tissue ingrowth into the epoxy lead channel. Tissue biopsy demonstrated the presence of fibrous tissue with focal necrosis and deposition of hemosiderin. Granulation tissue was present and extended to the subcutaneous tissue adjacent to the skin erythema near the surgical incision. Fig 4. Extensive ingrowth of tissue is noted in the lead channel of the bipolar pacemaker model 602B in the pacemaker removed from Patient 16. Histological examination of this tissue and adjacent pacemaker lining tissue demonstrated focal necrosis and chronic inflammation. Granulation tissue was noted to be present from the site of lead insertion into the pacemaker to the subcutaneous tissue adjacent to the area of skin attentuation. rounding tissue demonstrated fibrous tissue with focal necrosis and deposition of hemosiderin. Tissue ingrowth into the epoxy channel of the pacemaker generator unit was noted at the site of both electrodes (Fig 3). The indwelling bipolar unit was removed and replaced with an Intermedic unipolar pacemaker generator unit. The proximal lead of the bipolar electrode was capped with an adapter. The Silastic sleeve of the Intermedic pacemaker generator unit allowed mechanical sealing of the pacemaker lead and pacemaker generator channel. abdomen. The present pacemaker and lead had been in place for 10 months. Four months following implantation of this system, skin attenuation and erythema became noticeable over the pacemaker site. Increasing erythema, skin attenuation, and discomfort persisted, and elective replacement was performed. During the replacement operation, dense fibrosis was noted in the tissue surrounding the pacemaker generator unit. Electrode corrosion was visible in the pacemaker unit and tissue ingrowth into the unit was extensive (Fig 4). Granulation tissue was present from the site of lead insertion into the pacemaker to the subcutaneous tissue and was associated with the adjacent skin erythema. Histological examination of biopsy sections from tissue surrounding the pacemaker generator unit demonstrated fibrous tissue with focal necrosis and chronic inflammation. Cytological examination of aspirated fluid demonstrated neutrophils, histiocytes, and necrotic debris consistent with inflammation. Electronic evaluation of pacemaker function Patient 16 A 64-year-old man was admitted to the hospital because of imminent pacemaker extrusion. Initial pacemaker implantation had been performed 8 years previously for symptomatic bradycardia. During this interval, several replacements had been performed and the current pacemaker and lead configuration consisted of two Medtronic model 5814 epicardial leads and a Cardiac Pacemakers, Inc., model 602B (serial no ), which was inserted into the upper

5 449 Cohn et al: Pacemaker Erosion From Electrode Seal Defects was within normal limits and specifications. The epicardial lead, which had been inserted into the pacemaker generator unit, allowed free movement between the electrodes enclosed within the pacemaker epoxy channel and the surrounding tissue. The Medtronic epicardial leads were considerably smaller than the channel diameter in the pacemaker unit, and this allowed buildup of tissue and debris within this lumen. Though imminent erosion of the pacemaker occurred 10 months following initial implantation, this represents one of the earliest erosions related to this problem of the pacemaker generator interface. Following irrigation of the pacemaker pocket and appropriate debridement, an Intermedic unipolar pacemaker generator unit, model 251 (serial no ) was inserted. One of the epicardial leads was capped with a plastic adapter. Use of the Intermedic unit with a Silastic sleeve allows a firm tie to occlude the electrode and prevent tissue and fluid ingress into the epoxy lead channel. This provides a satisfactory solution for pacemaker channel tissue ingrowth that occurs in this manner. Results Out of 209 pacemaker insertions, 16 pacemaker generator units were removed because of pacemaker erosions. Erosion occurred from 1 to 36 months following insertion and resulted in frank skin necrosis and extrusion of the pacemaker generator in four instances. Localized skin induration, erythema, and tenderness were present in twelve. The incidence of erosion was 7.7%. Analysis of the data indicate that primary pacemaker pocket infection occurred in 1 patient (Patient 12), in whom septicemia developed, with blood cultures yielding StaphyZococcus aureus. This complication could be traced to events that occurred at the time of implantation. Erosion of the pacemaker occurred five weeks following implantation and was the earliest erosion in this series. Two additional wound cultures (Patient 5 and 13) demonstrated pathological organisms, and the associated pacemaker erosions occurred within 3 months of initial implantation. Thus, infection that occurs at the time of surgical implantation L 0 (Ipooooo l I I I I I l l MONTHS AFTER IMPLANTATION Fig 5. The occurrence of pacemaker generator removals associated with iminent or actual pacemaker erosion. The solid circles represent instances of documented pacemaker pocket infection, and all 3 occurred at less than 3 months following implantation. Thirteen additional pacemaker erosions not associated with an infective process occurred at 7 to 36 months following implantation. may only account for those pacemaker erosions seen within 3 months of pacemaker insertion. As shown in Figure 5, all other pacemaker replacements for erosions were done more than 7 months following implantation. Cultures obtained during pacemaker removal or replacement procedures in these patients were sterile or yielded nonpathogenic or skin contaminant organisms. Gross examination of the pacemaker site uniformly demonstrated induration and edema of the pacemaker pocket lining tissue. Granulation tissue and maximum induration of the lining tissue were always present at the junction of the pacemaker lead and pacemaker generator unit. Tissue could frequently be seen to enter the space between the pacemaker lead and the lumen of the pacemaker generator in continuity with the lead electrode (see Figs 1,3,4). Histological examination of the excised tissues demonstrated granulation tissue with focal necrosis, chronic inflammation, and fibroblastic proliferation. Foreign body giant cell reactions were not present. Polymorphonuclear infiltration was not a prominent finding in those pacemakers associated with late erosion, as might be anticipated in the presence of an infective process. Comment Improved pulse generator design and use of lithium-battery and nuclear energy generating units have increased the longevity of pacemaker devices. Long-term implantation of

6 450 The Annals of Thoracic Surgery Vol 28 5 vember 1979 pacemaker generator units has, however, become associated with specific failure modes related to electrical components and pacemaker lead construction. The occurrence of late pacemaker erosion due to a noninfective process indicates that a pacemaker generator or lead design feature can be a causative factor. Prior investigation [ll has established a causal relationship between pacemaker generator design and tissue growth into a potential space in the pacemaker generator unit. This investigation also indicated that tissue exposed to a pacemaker electrode would migrate in tissue culture. Thus, an exposed pacemaker generator electrode within the pacemaker site is not biologically inert [2]. Instances of late pacemaker generator erosion were uniformly associated with pacemaker site induration. Pain was present and was most intense at the junction of the pacemaker lead and generator junction. Cultures from the pacemaker site at replacement did not yield infective organisms. Histological study demonstrated inflammatory reaction, fibroblastic proliferation, and granulation tissue, which was most prominent at the pacemaker lead insertion into the generator unit. A loose fit of the pacemaker lead into the lumen of the generator was commonly seen in these instances and may be responsible for the initiation of events leading to tissue ingrowth in this area. Based on these investigations, it is clear that improved design characteristics are required for the satisfactory long-term function of the electrode lead-pacemaker junction interface. It is recommended that labeling be improved so that surgeons implanting pacemakers are assured that the mechanical as well as electrical properties of the electrode lead are compatible with the pacemaker generator unit. Improved quality control during manufacturing is necessary in order to eliminate the possibility of potential space problems during implantation or their development on a long-term basis. Improved seal design of the electrode lead junction and pacemaker generator unit is also required to further assure elimination of continuity between the pacemaker generator electrode and tissue fluid. References 1. Cohn JD, Thorson RF: Extrusion of pacemaker pulse generator due to design defect. J Thorac Cardiovasc Surg 65:323, Huffmann JK, Goodman GR: Considerations for intra-operative pacemaker and lead system analysis. Cardiovasc Dis, Bull Texas Heart Inst 3:236, 1976