Pulse Generator Replacement Research Articles

Preservation of a subcutaneous pocket for vagus nerve stimulation pulse generator during magnetoencephalography

Patients with epilepsy and an implanted vagus nerve stimulation (VNS) device who are referred for consideration of definitive epilepsy surgery (removal of the epileptogenic cortex) may require magnetoencephalography (MEG), a study requiring explantation of the pulse generator, as part of their evaluation. Nonetheless, these patients may not wish to abandon palliative VNS therapy should definitive surgery prove unsuccessful or impossible. To avoid obliteration of the pocket by scar tissue after the pulse generator is explanted, the authors have preserved the dead space in several patients with insertion of a similarly sized silicone block. This block is easily replaced with the pulse generator if continued VNS therapy is appropriate, and is left in place in patients who appear to no longer require VNS therapy. Upon completion of MEG, if pulse generator replacement proves desirable, atraumatic retrieval of the electrode connector pin and body is easy. Silicone block implantation during what may prove to be temporary device explantation facilitates reuse of the original pulse generator implantation site and atraumatic distal electrode wire retrieval.

Complication Risk with Pulse Generator Change: Implications When Reacting to a Device Advisory or Recall

Recent advisories and recalls of pacemakers and implantable cardioverter-defibrillators (ICDs) have highlighted the need for evidence-based recommendations regarding management of patients with advisory devices. In order to better facilitate decision-making when weighing the relative risks and benefits of performing generator changes in these patients, we conducted a review to assess operative complication rates. We reviewed generator changes performed between 2000 and 2005 at the Mayo Clinic-Rochester, including a total of 732 change-outs consisting of 570 done for elective replacement indicators (ERI) and 162 for manufacturer advisories or recalls. Complications included all those requiring reoperation, occurring within a 60-day period postoperatively and directly attributable to the generator change. These included infection requiring device excision, hematoma requiring evacuation, and incisional dehiscence requiring reclosure. Operation-associated complications requiring intervention were noted in 9 patients, or 1.24% of our population. Of these nine complications, eight occurred among patients receiving pulse generator replacement for ERI (1.40%) and one occurred in a patient receiving replacement for a manufacturer advisory or recall (0.62%). Complications included 5 infections, 3 hematomas, and 1 incisional dehiscence. Generator replacement is not a benign procedure and associated risks must be weighed in the context of other variables when making management choices in patients with advisory or recall devices.

The Implantable Cardiac Defibrillator

implantable cardioverter-defibrillator (ICD) is one of the great engineering achievements of the twentieth century.1 This electronic device detects potentially lethal cardiac arrhythmia (ventricular fibrillation [VF] or ventricular tachycardia [VT]) and shocks or overdrives the heart to restore normal sinus rhythm. Smaller than the tiniest cell phone, the ICD system consists of a battery, leads to sense rhythm and to deliver the shock, a computer that analyzes cardiac waveforms and initiates a counter-pulsation algorithm, charging circuitry that converts battery power to the voltage and current needed to overcome the arrhythmia, and memory to document cardiac and device activity. Additional components of the system include an external programmer to interrogate the ICD memory and to tailor sensing and firing algorithms to optimize care for a particular patient. Initially approved by the Food and Drug Administration in 1985, the first-generation ICD was bulky, weighing more than 9 ounces. Implantation was a complex open-heart surgical procedure (thoracotomy) with the attendant risks of general anesthesia and surgical site infection. Rudimentary sensing algorithms resulted in occasional false firings, which some patients equated to being kicked by a mule. Battery life was at best 2-3 years and necessitated additional surgery to replace the pulse generator. While Medicare coverage soon became available, eligibility criteria were highly restrictive, framing the device as: ... a treatment of last resort for patients who have documented episodes of life-threatening tachyarrhythmia or cardiac arrest not associated with myocardial infarction. Patients must also be found by electrophysiologic testing to have an inducible tachyarrhythmia that proves unresponsive to medication or surgical therapy . . .2 Over the ensuing 20 years, the technology has steadily evolved.3 The device has shrunk to less than one-fifth the original size, the number of leads has been reduced, and sensing algorithms refined. Battery life has improved to the point where 5-10 years may elapse before pulse generator replacement is required. Most importantly, the smaller and more elegant design facilitated a much simpler implantation procedure that does not require opening the chest, and can be performed in an ambulatory surgery center under local anesthesia. Technological evolution combined with growing evidence for survival benefit has resulted in progressive relaxation of Medicare coverage criteria. From the beginning, controversy has surrounded the ICD because of debate over whether or not the technology is Determinants of ICD cost-effectiveness relative to standard care include the cost of the procedure, the survival benefit of the device, and the risk of cardiac arrhythmic death in the target patient population. Over time, the annualized cost of the ICD has decreased due to less invasive surgery and longer battery life. Lower costs make the device more cost-effective. Conversely, broadening of selection criteria has reduced the relative risk of patients receiving the therapy, which tends to reduce cost-effectiveness. The Multicenter Automatic Defibrillator Implantation Trial II (MADIT II) trial evaluated ICD benefit and cost relative to conventional pharmacologic therapy among myocardial infarction survivors with impaired cardiac pumping ability as evidenced by an

Mudança do modo VVI para DDD ("upgrade") na troca eletiva do gerador de pulsos: análise comparativa clínico-funcional

Evaluate the clinical and functional behavior of the ventricular and atrioventricular stimulation modes in the elective replacement of pulse generator in patients with chagasic cardiopathy and atrioventricular block. Twenty-seven patients under ventricular and atrioventricular stimulation were comparatively evaluated at the beginning of the study, and alternately in ventricular and atrioventricular modes in two 90-day phases, with regard to: the clinical behavior evaluated according to quality of life and functional class, and the functional behavior evaluated by transthoracic echocardiography and the six-minute walk test. The statistical analysis was performed with patients at baseline, and under ventricular and atrioventricular modes, using the chi-square test and the repeated measures analysis of variance, and taking into consideration a 0.05 level of significance. The mean quality-of-life scores were: functional capacity (VVI 71.3+/-18.2 , DDD 69.3+/-20.4); overall health status (VVI 68.1+/-21.8, DDD 69.4+/-19.4) and vitality (VVI 64.8+/-24.6 , DDD 67.6+/-25.5); on echocardiography: LVEF (VVI 52.5+/-12.8 , DDD 51.8+/-14.9), LVDD (VVI 53.0+/-7.7 , DDD 42.4+/-7.8), LA (VVI 38.6+/-5.4 DDD 38.5+/-5.1), and in the six-minute walk test: distance walked (VVI 463.4+/-84.7, DDD 462.6+/-63.4). There were four cases of complications, three of them associated with the change in stimulation mode. This study showed no differences between the two stimulation modes in the clinical behavior assessed by quality of life and functional class, and in the functional behavior, evaluated according to the ecochardiographic findings and the six-minute walk test.

Near-fatal incident on routine induction of ventricular fibrillation at the replacement of an implantable cardioverter defibrillator

The case of a 54-year-old patient with severe coronary artery disease and storms of ventricular tachyarrhythmias is presented. On the replacement of an implantable cardioverter defibrillator due to battery depletion, he suffered life-threatening complications associated with arrhythmia induction. Performing a routine induction of ventricular arrhythmias on the occasion of pulse generator replacement may be reconsidered in selected patients.

One Stage Side‐to‐Side Replacement of Infected Pulse Generators and Leads

Infected and contaminated cardiac pulse generators and leads must be removed entirely in order to effect a cure. We have shown through our experience with 68 consecutive cases that explantation of the offending system and replacement of a new device on the opposite side can be safely accomplished in one sitting--a side-to-side replacement--as long as there is appropriate case selection. There were no early or late infections of the new operative site.

Effect of an Active Abdominal Pulse Generator on Defibrillation Thresholds with a Dual-Coil, Transvenous ICD Lead System

Many patients with implantable cardioverter defibrillators (ICDs) have older lead systems, which are usually not replaced at the time of pulse generator replacement unless a malfunction is noted. Therefore, optimization of defibrillation with these lead systems is clinically important. The objective of this prospective study was to determine if an active abdominal pulse generator (Can) affects chronic defibrillation thresholds (DFTs) with a dual-coil, transvenous ICD lead system. The study population consisted of 39 patients who presented for routine abdominal pulse generator replacement. Each patient underwent two assessments of DFT using a step-down protocol, with the order of testing randomized. The distal right ventricular (RV) coil was the anode for the first phase of the biphasic shocks. The proximal superior vena cava (SVC) coil was the cathode for the Lead Alone configuration (RV --> SVC). For the Active Can configuration, the SVC coil and Can were connected electrically as the cathode (RV --> SVC + Can). The Active Can configuration was associated with a significant decrease in shock impedance (39.5 +/- 5.8 Omega vs. 50.0 +/- 7.6 Omega, P < 0.01) and a significant increase in peak current (8.3 +/- 2.6 A vs. 7.2 +/- 2.4 A, P < 0.01). There was no significant difference in DFT energy (9.0 +/- 4.6 J vs. 9.8 +/- 5.2 J) or leading edge voltage (319 +/- 86 V vs. 315 +/- 83 V). An adequate safety margin for defibrillation (> or =10 J) was present in all patients with both shocking configurations. DFTs are similar with the Active Can and Lead Alone configurations when a dual-coil, transvenous lead is used with a left abdominal pulse generator. Since most commercially available ICDs are only available with an active can, our data support the use of an active can device with this lead system for patients who present for routine pulse generator replacement.

Antibiotic Prophylaxis with a Single Dose of Cefazolin During Pacemaker Implantation: Incidence of Long‐Term Infective Complications

Systemic and localized infections related to permanent pacemaker implantation are not common, but are serious and potentially life-threatening complications. The aims of this prospective observational study were: (1) to assess the safety and long-term efficacy of a simplified scheme of antibiotic prophylaxis, and (2) to identify the predictors of long-term infective complications, in patients undergoing pacemaker implantation or replacement. From October 1998 to July 2001, 852 patients (mean age 77.0 +/- 9.2 years; 474 men) who underwent new permanent pacemaker implantation (69.6%) or pulse generator replacement (30.4%) received a mini-bag of 2 g of cefazolin diluted in 50 mL of saline solution, administered intravenously in 20 minutes before the beginning of the procedure. Early (within 2 months of implantation) and late major and minor infective complications were recorded. During the earlier phase, minor complications were observed in 9 patients (1%). During the long-term phase of the surveillance (mean 25.6 +/- 11.0 months, range 12-55 months) major infective complications were observed in 6 patients (0.7%). On multivariate analysis, no clinical or procedural variable predicted the occurrence of long-term infective complications. Our data indicate the safety and efficacy of a single, intravenous 2 g dose of cefazolin in preventing infective complications related to pacemaker implantation or replacement. No clinical or procedural variable predicted the occurrence of long-term infective complications.

Inappropriate implantable cardioverter defibrillator therapy delivered after sensing of arc welding

Introduction: Electromagnetic interference continues to be a life-threatening cause of ICD malfunction. This report presents an unusual case of inappropriate ICD discharge that occurred while a patient was swimming in a lake. Case Report: A 55 year old male with a history of coronary artery disease, extensive myocardial infarction, and ventricular fibrillation was first implanted with a dual-chamber ICD system on August 5, 1999 with subsequent pulse generator replacement on June 1, 2004. The new pulse generator was a Medtronic model 7274; the chronic atrial lead was a Medtronic model 6940, and the chronic right ventricular lead was a Medtronic model 6945. On July 18, 2004 the patient received two shocks. The patient reported no preceding symptoms of syncope or palpitations prior to ICD therapy. The ICD had been programmed with VT detection above 182 bpm, VF detection above 240 bpm, and ventricular sensitivity of 0.3 mV. The figure shows the intracardiac electrograms recorded during a VF episode stored that day. Electrical activity consistent with 50/60 Hz alternating current superimposed upon normal myocardial activity at 60 bpm was recorded by the ICD in several episodes that day as nonsustained VT (5-7 beats in duration) and in 3 episodes as VF. During the 11 minutes in which these “episodes” were recorded, the patient was lying on a raft in a lake. Electrical current generated during arc welding repair of a nearby dock was recorded and interpreted by the ICD as rapid ventricular activity, resulting in inappropriate therapy. Discussion: ICDs remain front-line prevention for sudden cardiac death. This unusual case report of electromagnetic interference over a long distance demonstrates a need for continued improvement of sensing algorithms.

Efeitos da mudança de modo de estimulação ventricular para atrioventricular sobre a qualidade de vida em pacientes com cardiopatia chagásica e bloqueio atrioventricular na troca eletiva do gerador de pulsos

OBJETIVO: Avaliar os efeitos da mudança de modo de estimulação ventricular para atrioventricular sobre a qualidade de vida em pacientes com cardiopatia chagásica e bloqueio atrioventricular, na troca eletiva do gerador de pulsos. MÉTODO: No período de 8 de setembro de 2001 a 18 de março de 2004, no Instituto do Coração da Faculdade de Medicina da Universidade de São Paulo e no Hospital de Beneficência Portuguesa de Ribeirão Preto, foram estudados comparativamente sob estimulação ventricular e atrioventricular 27 pacientes com cardiopatia chagásica e bloqueio atrioventricular, com indicação de troca eletiva do gerador de pulsos. Os pacientes foram analisados na inclusão do estudo e alternadamente no modo ventricular e atrioventricular em duas fases com duração de 90 dias, considerando-se o comportamento clínico, avaliado pela qualidade de vida. A análise estatística foi realizada na condição basal, modo VVI e modo DDD, utilizando-se o teste de variância para medidas repetidas, considerando-se nível de significância de 0,05. RESULTADOS: Não foram detectadas diferenças de comportamento na qualidade de vida, avaliada pela capacidade funcional pelo estado geral e pela vitalidade, entre os dois modos de estimulação cardíaca estudados. Ocorreram três casos de complicações relacionadas à mudança de modo de estimulação: dois casos de taquiarritmias atriais conduzidas pelo marcapasso e um caso de deslocamento de eletrodo atrial. CONCLUSÕES: A análise comparativa da estimulação ventricular com a atrioventricular, na troca eletiva do gerador, demonstrou que não houve diferença de comportamento clínico sobre a qualidade de vida.

&lt;![CDATA[&lt;B&gt;Health-related quality of life in patients with Chagas' cardiomiopathy and complete atrioventricular block at elective pulse generator replacement: effects of pacing mode upgraded from VVI to DDD&lt;/B&gt;]]&gt;

&lt;![CDATA[&lt;B&gt;Health-related quality of life in patients with Chagas' cardiomiopathy and complete atrioventricular block at elective pulse generator replacement: effects of pacing mode upgraded from VVI to DDD&lt;/B&gt;]]&gt;

Pacemakers and Implantable Cardioverter Defibrillators:

The size of pacemakers and implantable cardioverter defibrillators (ICDs) has been diminishing progressively. If two devices are otherwise identical in components, features and technology, the one with a larger battery should have a longer service life. Therefore, patients who receive smaller devices may require more frequent surgery to replace the devices. It is uncertain whether this tradeoff for smaller size is desired by patients. We surveyed 156 patients to determine whether patients prefer a larger, longer-lasting device, or a smaller device that is less noticeable but requires more frequent surgery. The effects of subgroups were evaluated; these included body habitus, age, gender, and patients seen at time of pulse generator replacement (PGR), initial implant, or follow-up. Among 156 patients surveyed, 151 expressed a preference. Of these, 90.1% preferred the larger device and 9.9% the smaller device (P <0.0001). Among thin patients, 79.5% preferred a larger device. Ninety percent of males and 89.2% of females selected the larger device. Among younger patients (< or =72 years), 89.6% preferred the larger device, as did 90.5% of older patients (>72 years). Of patients undergoing PGR or initial implants, 95% favored the larger device, as did 86% of patients presenting for follow-up. The vast majority of patients prefer a larger device to reduce the number of potential replacement operations. This preference crosses the spectrum of those with a previously implanted device, those undergoing initial implants, those returning for routine follow-up, and patients of various ages, gender, and habitus.

The subpectoral pacemaker implant: it isn't what it seems!

The traditional pulse generator implantation site lies subcutaneous on the fascia of the pectoralis major muscle. This article describes a subpectoral pocket approach, which on anatomic investigation is actually "intrapectoral" and offers a much improved cosmetic result with the potential advantage of less erosion. In the authors' experience with over 1000 initial pacemaker implants and pulse generator replacements, the potential concerns of neurovascular and muscular damage have not been realized. There has been no pulse generator damage from the ribs, serious loculated hematomas, or unusual postoperative or chronic pain. From experience with pulse generator recalls, the replacement procedure has not been significantly more difficult than with the subcutaneous approach. The intrapectoral approach has now become the authors' routine in patients without significant adipose tissue overlying the pectoralis major muscle.

The Nature and Frequency of Postimplant Surgical Interventions:

The purpose of this retrospective study was to investigate the nature and frequency of surgical reinterventions after primary pacemaker implantation in patients who survived at least 20-30 years. Eighty-five such patients were identified, 32 of whom had radioisotopic (nuclear) implants, and 53 lithium battery powered lithium units. Excluding reoperations within the first 3 months, patients with nuclear implants experienced about two reoperations in 25 years, while those with lithium experienced one every 8 years. The most frequent reasons for surgery were pulse generator replacements, lead revisions, and mode changes, particularly in the nuclear group. There were no premature device failures. This study allows us to make reasonable predictions to patients about the experience a pacemaker implantation, and reassures us about the reliability of the devices that were implanted in the past.

Compatibility of automatic threshold tracking pacemakers with previously implanted pacing leads in children.

The Autocapture function controls and optimizes the amplitude of the pacing pulse and saves energy. The manufacturer recommends using a special low polarization, low threshold bipolar Pacesetter lead for the Autocapture function. The purpose of this study was to evaluate the compatibility of Autocapture with previously implanted pacing leads. The study included 15 patients (mean age 13.6 +/- 3.4 years) who needed pulse generator replacement and received the VVIR pacemaker Regency SR+ or the DDDR pacemakers Affinity DR or Integrity DR with the Autocapture function. The new pulse generators connected to previously implanted ventricular leads. At the time of implantation the pacing threshold was 1.0 +/- 0.35 V at 0.5 ms, the lead impedance was 580 +/- 80 omega, and the spontaneous R wave amplitude was 7.89 +/- 4.89 mV. The polarization signal (PS) was 3.8 +/- 3.04 mV, and evoked response (ER) was 8.15 +/- 4.57 mV at the predischarge testing. Follow-up telemetry was done at months 1, 3, 6, 12, and 18. The follow-up duration was 9.4 +/- 5 months (range 1-18 months). If the results of PS and ER measurements were acceptable for autocapture, it turned on at the 1-month visit. In six (40%) patients the results were found acceptable for autocapture function. Age, lead impedance, pacing threshold, intrinsic R wave measurement, lead age, fixation mechanism, and ER measurements were not statistically different in Autocapture suitable and not suitable groups. The main reason not to activate Autocapture had been increased PS. Any significant fluctuations were not observed in pacing threshold, lead impedance, ER, and PS during follow-up. In conclusion, previously implanted pacing leads may be compatible with the Autocapture function.

Runaway Pulse Generator Malfunction Resulting from Undetected Battery Depletion

Runaway pacemaker is an uncommon, potentially lethal circuit malfunction characterized by sudden onset of erratic pacing at rapid nonphysiological rates. Two patients with a single chamber pacemaker (Medtronic ST 8331 and 8419) presented with episodic dizziness. ECG revealed recurrent decrescendo amplitude episodes of runaway stimuli at 2,400 and 2,600 ppm, approximately 3 seconds in duration, separated by pacing at 62.5 and 65 ppm, respectively. Fortunately the runaway stimuli were subthreshold and did not result in capture of the ventricle. Emergency pulse generator replacement was uneventful. Both leads were normal and both pulse generators had low battery voltages at 1.488 and 1.78 V, respectively.

Do battery depletion indicators reliably predict the need for pulse generator replacement?

The aim of this study was to test the validity of battery depletion indicators to forecast end of service (EOS) in dual chamber pulse generators (PG). Two additional approaches for prediction of EOS were evaluated as well: the real-time telemetry of cell impedance and a battery stress test (BST) that used a transitory increase in pacing rate. The study population consisted of 119 patients with Intermedics dual chamber PG models Cosmos II and Relay, in which cell impedance had exceeded 2.5 k omega. The patients were followed in 6-month intervals. If the interrogation of the PG or the BST prompted the appearance of the intensified follow-up indicator (IFI), the next follow-up was scheduled within 2 months. PG replacement was performed on physician's discretion or immediately on appearance of the elective replacement indicator (ERI), regardless of the method of ERI provocation. During a period of 2 years/and 9 months, 33 patients underwent PG replacement. Out of 21 patients with positive ERI indicators, only 5 had positive warning indicators of approaching battery depletion in the preceding follow-up (IFI during BST, n = 4; ERI during BST n = 1). The majority of patients (n = 16, 76%) revealed ERI without prior activation of IFI, neither spontaneous nor during the BST. Four of these 16 ERI-positive patients had cell impedance values far below the ERI limits of the manufacturer. Based on battery depletion indicators, an exact prediction of EOS of dual chamber pacemakers is not possible. Measuring battery impedance allows for a statistical estimation of remaining service life but it may be misleading in the individual case. A BST that is based on a temporary increase of pacing rate is invalid in forecasting battery depletion. As activation of the ERI can trigger an abrupt change to the VVI backup mode, pacemaker dependent patients with low programmed basic pacing rates may be hemodynamically compromised by an unexpected activation of ERI. Close monitoring intervals and PG replacement before appearance of the ERI is recommended in those patients.

Comparison of bipolar and integrated sensing for redetection of ventricular fibrillation

Background Implantable cardioverter-defibrillator function is critically dependent on reliable sensing of intracardiac signals. Lead systems that use integrated sensing, in which the distal shocking coil is part of both the sensing and shocking pathways, may be prone to undersensing of ventricular fibrillation, especially during redetection after a failed first shock. To assess the effect of endocardial lead system on redetection, we compared a dedicated rate-sensing lead and 2 generations of integrated sensing defibrillator leads with a uniform testing algorithm and pulse generator. Methods The study group consisted of 72 patients after implantable cardioverter-defibrillator implantation. Three transvenous rate-sensing leads were evaluated: a standard pacing lead, incorporating true bipolar sensing without ventricular coils, or an integrated shocking and sensing lead (Endotak C) with either 6-mm (60 series) or 12-mm (70 series) spacing between the sensing tip and shocking coil. Redetection was assessed from a failed first shock just below defibrillation threshold. Results Compared with the dedicated bipolar lead, redetection was prolonged with the 60 series lead (8.3 ± 3.6 vs 6.6 ± 2.3 seconds, P = .04). Moreover, prolonged redetection (>8 seconds) was observed in 41% of patients with 60 series leads compared with only 11% with dedicated bipolar leads ( P < .01). No significant effects on redetection were noted with an integrated lead with greater spacing between the tip and coil (70 series). Conclusions Delayed redetection is frequently noted with an integrated lead with close spacing between the tip and coil. Detailed evaluation of detection and redetection of these leads should be performed at the time of pulse generator replacement. (Am Heart J 1999;138:133-6.)

Insulation lead failure: is it a matter of insulation coating, venous approach, or both?

Lead insulation material and implant route have a major impact on lead reliability and durability. We compare the incidence of lead insulation failure resulting from both the venous approach and insulation type. Two hundred ninety consecutive leads were followed for a mean period of 57 +/- 30 months; leads with < 1 year follow-up were excluded. There were 116 Silicone Rubber insulated leads and 174 with polyurethane (151 Pellethane 80A and 23 Pellethane 55D) insulation; 279 leads were bipolar and 11 unipolar; 274 leads were implanted in the ventricle and 66 in the atrium. The venous route was the subclavian vein for 170 leads (58%) and the cephalic vein for 120 leads (42%). Insulation failure was diagnosed when a single sign of oversensing, undersensing, failure to capture, early pulse battery depletion, and lead impedance < 250 omega was present. Measurement of lead impedance was performed intraoperatively at implantation and during lead revision or pulse generator replacement. Lead failure caused by conductor coil fracture was not considered. There were 13 lead insulation failures, all among leads with polyurethane insulation (12 Pellethane 80A and 1 Pellethane 55D). Eleven failures (10%) occurred when the subclavian vein and 2 (3%) when the cephalic vein approach was used. The cumulative survival rate of polyurethane and silicone rubber insulated leads was 88.7% and 100%, respectively (P = 0.02); the cumulative survival rate of polyurethane insulated leads was 83.2% when the subclavian vein and 95.1% when the cephalic vein were used (P = 0.03). The mean time to polyurethane lead failure when the subclavian vein approach was used was 54 +/- 17 months and when the cephalic route was 73 +/- 4 months (P < 0.02). By multivariate analysis, the route of entry was found to be a significant variable related to polyurethane insulated lead failure (P < 0.05). At lead revision failure to capture was present in 7, oversensing in 4, and undersensing in 2 instances; impedance was < 250 omega in all cases. Pellethane 80A insulated leads are prone to insulation failure, but more when the subclavian vein is used, rather than the cephalic vein.

Long-term Follow-up of the Patients with Permanent Antibradycardia Pacemaker

Background:Antibradycardia pacemaker is one of the treatment modalities for bradyarrhythmia. We present the clinical results of 440 implantations of permanent pacemaker between August 1984 and December 1997 at Department of Internal Medicine in Seoul National University Hospital. Method:We investigated the indication of permanent pacing, the pacing modes, the complications of permanent pacing, and the chronic pacing threshold. Result:The study was comprised of 440 patients (M/F:179/261, mean age:59±12 years, 58±14 years, respectively). Indications of the primary pacemaker implantations were sinus node dysfunction in 53% and atrioventricular conduction disorders in 47%. Twelve percent of total pacemaker procedures were pulse-generator replacements. Pacing modes were VVI in 59.1%, VVIR in 10.2%, DDD in 30.2%, and others in 0.5%. Complications developed in 21 cases (4.8%) during long-term follow-up. They included 8 cases of pacing failure due to increased pacing threshold, 2 cases of early power depletion, 2 cases of lead dislodgement, 6 cases of lead fracture, 3 cases of skin erosion, 3 cases of hematoma, 3 cases of infection, and 1 case of skeletal muscle stimulation. Chronic pacing thresholds at pacing width of 0.5 msec were 1.9±0.4 V for the epicardial ventricular leads (n=11), 1.3±0.5 V for the endocardial ventricular leads (n=36), and 1.1±0.2 V for the atrial leads (n=4) after 7 to 10 years of implantation. Conclusion:Sinus node dysfunction was the more common indication than atrioventricular block for the antibradycardia pacemaker implantation. Long-term follow-up of the pacemaker patients would be very useful to detect the pacing system abnormalities and to maximize the battery longevity by adjustment of pacing output according to the level of chronic pacing threshold. (Korean Circulation J 1998;28(5):768-773)