Incidence and Prognosis of Pacemaker Lead-Associated Masses: A Study of 1,569 Transesophageal Echocardiograms

Ronald Lo, MD, Michael D'Anca, MD, Todd Cohen, MD, Todd Kerwin, MD, Winthrop University Hospital, Mineola, New York

Ronald Lo, MD, Michael D'Anca, MD, Todd Cohen, MD, Todd Kerwin, MD, Winthrop University Hospital, Mineola, New York

Cardiac permanent pacemaker (PPM) and implantable cardioverter-defibrillator (ICD) devices have significantly enhanced the treatment of patients with dysrhythmias, and their application in clinical practice has become increasingly common. As of 2002, there were an estimated 415,000 functioning ICD devices, and over 2.25 million PPM devices presently utilized worldwide.1 Pacemaker and ICD lead masses are rare, however, they are becoming more prevalent. Lead endocarditis is becoming a significant source of morbidity and mortality. Although rare, the incidence rates range from 1 - 7%, with mortality rates approaching 33%.2 The incidental thrombotic mass on leads is also frequently identified, with an estimated incidence of 2 - 22%.3 Transesophageal echocardiography (TEE) is becoming more frequently utilized to screen for infections or masses involving indwelling catheters including pacemaker and ICD leads, exceeding the specificity and sensitivity of transthoracic echocardiography (TTE).4 The transesophageal approach reveals a better view of the right atrium and the superior vena cava, and window detail is less inhibited by pacemaker lead movement and reverberation. Patients with implanted leads will also undergo TEE examinations for purposes other than for an investigation of suspected endocardial infection. Incidental echogenic masses located on pacemaker and ICD leads are frequently encountered in routine examinations. The goal of our study was to retrospectively examine the incidence and prognosis of both suspected lead endocarditis and the incidentally discovered lead-associated mass. Methods This study was approved by the Institutional Review Board of Winthrop University Hospital. All cases of TEE were reviewed from January 2002 to January 2005 at Winthrop University Hospital. Of 1,569 TEEs reviewed, a pacemaker or ICD lead was visualized in 125 examinations. Patients were included in this analysis if they had evidence of a pacemaker or ICD lead in the right atrium or the right ventricle. Cases were retrospectively reviewed. The indications for TEE and clinical management were recorded. Fifteen patients were determined to have abnormal findings, specifically the presence of hyperechoic densities visualized on right heart leads. Follow-up telephone surveys were conducted on all patients with evidence of masses on TEE. All patients were asked follow-up questions focused on outpatient treatment including anticoagulation and antibiotics, repeat diagnostic studies, surgical interventions and associated complications. Patients with masses on TEE were divided into two groups for analysis. Group A was determined to have a pre-test likelihood of endocarditis with a mass localized on TEE. Group B is comprised of patients who were found incidentally to have a mass on the intracardiac lead. Results In 125 TEEs, pacemaker and ICD leads were visualized. Fifteen tests demonstrated an echogenic mass. Nine (7%) studies correlated with a clinical suspicion of endocarditis; these were analyzed as Group A. Six (5%) patients were found incidentally to have a mass on the pacing lead during TEE; these were analyzed as Group B. Group A analysis included 9 patients with presumed lead endocarditis. Six patients were treated with medical therapy alone. Five patients received 6 weeks of intravenous (IV) antibiotics via a PICC line. Six-month follow up revealed no recurrence of endocarditis. One patient was discharged home on warfarin and oral fluoroquinolones after receiving IV antibiotic therapy for 1 week. A repeat TEE was performed several weeks after discharge, which showed no change in the sessile mass initially viewed with no changes made to management. He was rehospitalized 5 months after discharge at a different institution with complaints of fever and malaise. The patient was treated for pneumonia with the same antibiotic therapy as received previously, and subsequently died 2 days after admission. An autopsy revealed extensive right-sided pulmonary thromboembolus extending from the right atrium through the distal branches of the pulmonary artery, with diffuse hemorrhagic pneumonia ante mortem. Three patients were treated with laser lead extraction and ICD generator explantation. No mortality was reported during follow up. Group B analysis included 6 patients who were found incidentally to have a mass on the pacing lead during TEE. Three patients were treated with warfarin, 2 received no specific therapy and 1 underwent surgical debridement of the lead during valve surgery. All of the patients in this group were alive at follow up, and no significant clinical events attributable to the lead-associated mass were observed. Discussion A majority of pacemaker lead infections are caused by Staphylococci genus, of which certain species have the ability to adhere to and seed prosthetic surfaces. Very shortly after biomaterial is implanted in the human body, it becomes coated with a complex mixture of host proteins and platelets. In one model system involving short-term contact between biomaterial and blood, fibrinogen was shown to be the dominant component and was primarily responsible for adherence of S. aureus in subsequent in vitro assays.5 In contrast, with material that has been in the body for longer periods such as IV catheters, the fibrinogen is degraded and no longer promotes bacterial attachment.6 Several other microorganisms have been shown to cause pacemaker lead endocarditis, including Corynebacterium, Enterococcus and Streptococcus.7 The most efficacious treatment of pacemaker lead endocarditis is the removal of the infected apparatus in conjunction with a several-week course of antibiotics, followed by reimplantation of the ICD device in a different site at a date several weeks following negative blood cultures. Del Rio and associates reported a 100% recurrence in pacemaker lead endocarditis in patients treated with antibiotics alone.8 In our study, we reported no recurrences of pacemaker endocarditis in patients treated with a prolonged course of broad-spectrum IV antibiotics and a mortality rate of 11.1% occurring in a treatment regimen consisting of short-term oral antibiotics. TEE has become increasingly important in the diagnosis and management of infective endocarditis. TEE allows for the visualization of the pacemaker lead route ranging from the superior vena cava to the insertion site in the right ventricle, and thus increases the ability to precisely locate the lesions on pacemaker leads.9 Because of superior views provided by the study and a negative predictive value of 90 - 100%, a negative TEE study significantly decreases the likelihood of IE, but does not completely exclude the diagnosis. Therefore, in this setting, a negative finding should be closely correlated with the clinical course. However, the question arises as to proper treatment protocols when echogenic masses are found incidentally. In our study, a total of 6 patients were found to have pacemaker-associated echogenic masses in tests conducted with low or no suspicion of bacterial endocarditis. This represents 5% of all patients with a pacemaker or ICD undergoing TEE. Treatment regimens varied from intermittent observation to anticoagulation and, in one case, surgical debridement. In these cases, as endocarditis was not considered based on clinical evidence, treatment regimens did not include antibiotics. We report a 100% survival rate among these patients, and no complications. Several factors have been associated with pacemaker lead densities including atrial fibrillation, ejection fraction < 40% and spontaneous echographic contrast.10 Some studies have speculated an increased risk of pulmonary embolus, and their association with pacemaker lead infection and mycotic embolization remains at this point hypothetical, as the general constituency of pacemaker strands and their ability to be seeded by bacteria has yet to be determined. Further study is necessary to determine whether such factors as strand dimensions, chronicity or location in areas of high turbulence increase the chance of complication and should affect the clinician's approach to patient care. Study limitations. The results were obtained from a single-center retrospective analysis. The small number of patients with significant masses is a major limitation. Specific antibiotic regimens utilized or the duration of anticoagulant therapy in those patients was not studied. The true incidence and prognosis of pacemaker lead-associated masses and endocarditis remains unknown. However, a multicenter prospective registry with long-term patient follow up would provide a more accurate assessment of the incidence and clinical outcome in patients with pacemaker lead-associated masses. Conclusion As the implant rate of pacemakers and ICDs continue to increase, both lead endocarditis and incidental masses noted on leads will become a more prevalent clinical entity. As randomized, controlled, clinical trial data are lacking, the clinician must exercise judgment when approaching these patients. Since an infected prosthetic device is rarely cured with antibiotics alone, serious consideration should be given to explanting the lead and generator. An incidentally noted mass appears to have a relatively benign course in our small series. This article was reprinted with permission from the Journal of Invasive Cardiology 2006;18(12):599 - 601.