Primary Pacemaker Implantation Research Articles

Incidence and significance of chronotropic incompetence in patients with indications for primary pacemaker implantation or pacemaker replacement.

This prospective study was undertaken to evaluate the incidence and significance of chronotropic incompetence in 211 patients [age 71.1 6 10.6 years (mean 6 SD)] by means of maximum exercise test in order to determine the indication for rate-responsive pacing before primary pacemaker implantation (147 patients) or pacemaker replacement (64 patients). There were 112 (53%) patients with second- or third-degree AV block, 63 (30%) with sick sinus syndrome, and 36 (17%) with chronic atrial fibrillation. Chronotropic incompetence was defined as maximum heart rate lower than age-adjusted norm calculated by the formula: 0.7x(220 - age) and its significance as the difference between the two rates. The overall incidence of chronotropic incompetence was 42%. The incidence was significantly higher in patients with atrial fibrillation (67%, P<0.0005) and sick sinus syndrome (49%, P<0.012) than in those with AV block (30%). The mean difference between maximum heart rate and the age-adjusted norm was 18% (range 2%-63%). The mean difference was significantly higher in patients with atrial fibrillation (27%, range 8-63%) than in those with sick sinus syndrome (19%, range 2%-45%, P<0.01), or with AV block (12%, range 6%-26%, P<0.000001). The rate-responsive pacemakers were implanted in 44% of 211 patients studied and in 43% of 196 patients excluded from the study due to the apparent (contra)indication of rate-responsive pacing (NS). Thus, chronotropic incompetence seems to be common in the pacemaker patient population. The highest incidence and significance was found in patients with chronic atrial fibrillation. Systematic evaluation of chronotropic competence can double the rate of implantation of rate-responsive pacemakers; however, further studies are needed to clarify relation between the significance of chronotropic incompetence and functional benefit of rate-responsive pacing.

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)

Sinus Node Dysfunction

Sinus node dysfunction (SND) is the indication for pacemaker implantation in 35–50% of all patients undergoing primary pacemaker implantation [1]. SND is characterized by syncopal attacks, dizzy spells, or heart failure due to sinus arrest, sino-atrial block, or sinus bradycardia. Approximately 50% of patients with SND suffers from paroxysmal atrial ~brillation, the brady-tachy syndrome, which is associated with an increased risk of arterial thromboembolism [2]. Although it is well recognized that cardiac pacing is effective in abolishing bradycardia-related symptoms in patients with SND, the most optimal pacing mode is, however, still debated. The present review will focus upon the results of recently published prospective trials on selection of pacing mode in SND and the clinical consequences of these results.

Survey of cardiac pacing in the United States in 1989

A survey of physicians who implant permanent cardiac pacemakers was conducted to identify practice patterns related to pacemaker-implantation frequency, hospital and implantation-facility characteristics, indications for pacing and pulsegenerator replacement, preferences regarding device types, pacing modes, follow-up methods and frequency, and type and frequency of pacing-related complications. Questionnaires were sent to 11,414 potential physician respondents and 6 pacemaker manufacturers. Implanters' opinions were solicited regarding such issues as the importance of various device features and capabilities, the appropriateness of practice guidelines, and the efficacy of quality-assurance measures. In 1989, 89,445 primary pacemaker implantations and 21,055 pulse-generator replacements were performed by approximately 7,919 physicians at about 3,400 U.S. centers. Typically, a pacemaker manufacturer's sales representative played an active role in 80% of cases. Since the last survey, which examined pacing practices in 1985, primary implantations of dual-chamber pacemakers increased from 22 to 32%, and the proportion of adaptive-rate pacemakers increased from 1 to 40% of primary implants. The “typical” implanter used bipolar electrode systems in 90% of cases, single-chamber pacemakers in 70%, and the introducer method in 95% of lead placements. Significant differences in practice patterns were found among subsets of the survey respondents. Surgeons tended to work alone, use simpler, singlechamber pacemakers, and leave follow-up to others. Electrode stability tended to be better among implanters in nonacademic environments. The quadrennial survey continues to provide useful information on an easily identifiable and traceable patient population, but the process would be greatly simplified by the adoption of a “universal” reporting system such as that used in Europe.

Complications of transvenous and transtboracic electrodes.

Electrode complications in a series of 220 patients are presented. At the primary pacemaker implantation, 114 patients received transvenous and 106 transthoracic electrodes. For the transvenous technique the Elema unipolar electrode (EMT 588 and 588 B) was used exclusively and for the transthoracic technique an epicardial disc electrode (EMT 567) was used in 64 per cent and myocardial electrodes (Vitatron MIP 125, Medtronic 5814 and 6913) in 36 per cent. The material was followed up for an average of three years (from 2 to 10 years). The dislocation frequency of transvenous electrodes was 10.4 per cent/patient-year, as 21 per cent of the electrodes became dislodged. Of the electrode dislocations, forty per cent occurred within the first post-implantation month. Exit block at stimulation with transthoracic electrodes was seen in 8.1 per cent/patient-year. Infections were more common with the transvenous than with the other types of electrodes. The myocardial electrode was significantly (p less than 0.05) more reliable than the transvenous electrode during the follow-up evaluated in terms of uncomplicated function time of the primary electrode. As in Helsinki both endocardial and myocardial-epicardial pacemaker electrodes have been used it seems to be of interest to report the results from our pacemaker material.