Implantation Of Pacing System Research Articles

Acute effects of radiofrequency ablation of atrial arrhythmias on implanted permanent pacing systems.

We studied the safety of performing RF catheter ablation in patients with implanted permanent pacemakers by monitoring the function of implanted pacing systems before, during, and immediately after exposure to RF energy. Patients with implanted pacing systems may require RF ablation for treatment of a variety of tachyarrhythmias. High frequency electromagnetic fields, such as RF energy, may affect implanted pacing systems, causing temporary or permanent loss of output, undersensing, oversensing, asynchronous pacing, or reversion to "reset" (Recommended Replacement Time or Power On Reset) parameters. Thirty-five patients with implanted pacing systems (23 DDDR, 6 VVIR, 5 DDD, 1 VVI, 31 bipolar and 4 unipolar) underwent RF catheter ablation. Prior to ablation, each pacing system underwent measurements of pacing and sensing thresholds, telemetry of intracardiac electrograms and measurement of battery voltage and lead impedance(s). During ablation, pacemaker function was monitored by real-time telemetry, intracardiac electrograms, and surface ECG. Immediately after ablation, each pacing system was reevaluated. Telemetry during RF ablation revealed normal pacing and sensing in 14 (40%) of 35 patients. Refractory period extension with asynchronous pacing and noise mode reversion were seen in 16 (46%) of 35 patients. Rare under- and/or oversensing, reversion to reset parameters, and telemetry "lock up" with inhibition of pacing output was seen in a few patients. After ablation, there were no significant changes in atrial or ventricular pacing or sensing thresholds or measurements of atrial and ventricular lead impedances. We conclude that most permanent pacemakers are not adversely affected by exposure to RF energy during catheter ablation. A variety of pacemaker behaviors may be seen during RF ablation, and a thorough understanding of each pulse generator's potential response(s) to electromagnetic interference is important before undertaking catheter ablation in patients with permanent pacemakers. Careful reevaluation of the patient's pacing system following the procedure is mandatory.

Effects of internal defibrillation on an implanted pacing system with programmable polarity.

Management of multiple cardiac arrhythmias in some patients with both an implantable cardioverter defibrillator (ICD) and a pacemaker has demonstrated several advantages. In such circumstances, it is imperative that pacemaker function and its programmed parameters be preserved following a defibrillation shock. This article describes the effects encountered by a specific programmable polarity pacemaker (RelayR 294-03) when subjected to electrical defibrillation in a canine model. Three pacemakers were repeatedly tested in three separate dog experiments. Each pacemaker, with its leads implanted in the right atrium and the right ventricle, was subjected to a minimum total number of 24 high energy biphasic and monophasic shocks (600-700 V) delivered by a coexisting ICD system using three different defibrillating lead configurations. None of the pacemaker systems showed any failure in function; all pacemakers continued to function within preshock specification and conversion to unipolar pacing and/or backup mode was not observed in any of the tests. Intracardiac electrical potentials measured directly off the ICD and the pacemaker leads, during a defibrillation shock (mean 566.6 V; 23.7 J), showed that potentials measured in a bipolar configuration (tip-ring: mean 21.0 V in atrium, 12.0 V in ventricle) were significantly less than potentials measured in a unipolar configuration (tip-can: mean 387.9 V in atrium, 394.0 V in ventricle; ring-can: mean 405.6 V in atrium, 395.4 V in ventricle). Our compatibility tests demonstrate that use of this programmable-polarity pacemaker in concert with an ICD system appears to be safe. Testing similar to the present study should be conducted prior to complete clinical acceptance of combined ICD and pacemaker implantation.

Effect of Implantable Nonthoracotomy Defibrillation System on Permanent Pacemakers: An In Vitro Analysis with Clinical Implications

Implantable cardioverter defibrillation systems are capable of delivering over 700 volts, and upwards of 40 joules (J) directly to the heart. Nonthoracotomy lead (NTL) systems allow the delivery of this energy to the inside of the heart, and potentially in close proximity to the leads of an endocardial pacing system. The effect of repeated maximal energy discharges (stored energy 40 J, delivered energy 38 J), utilizing both monophasic as well as biphasic shock pulses delivered via two different configuration NTL systems on a series of Pacesetter polarity programmable present generation single, and dual chamber pacemakers was evaluated in vitro using a saline test tank. All pulse generators studied demonstrated normal function and were not reprogrammed nor adversely affected by repeated defibrillation shocks. The current induced in the leads was assessed, and shown to be as high as 1.5 amps in the proximal conductor and 1.2 amps in the distal conductor of the ventricular lead, which may cause damage at the electrode-myocardial interface, and explain some of the postshock rise in capture and sensing thresholds that have been reported with implanted pacing systems postdefibrillation.

Outcomes of an ambulatory cardiac pacing program: indications, risks, benefits, and outcomes.

The purpose of this review was to evaluate the economical benefits and outcomes of an ambulatory pacing system implantation program that began in 1991 for new and replacement pacing system implantations. Patient access, incidence of complications, hospital bed day utilization, economic impact, safety, and practicality of the Ambulatory Pacing System Implantation Program was retrospectively reviewed from August 1991 to March 1994. The Ambulatory Pacing System Implantation Program includes pre-operative outpatient assessment in the pacemaker clinic, admission to the Day Medical Unit followed by same day pacing system implantation, discharge home after a short period of observation, and, in selected cases, cardiac monitoring, followed by pacemaker clinic visit 24-hours postimplantation. Two hundred four cardiac pacing systems, 154 new and 50 replacements (pulse generator/leads), were implanted under the guidelines of the Ambulatory Pacing System Implantation Program between August 1991 and March 1994. Eighty-seven percent of the patients were implanted with passive fixation leads, the remaining with active fixation leads; all but four of which were leads implanted in the atria. Preprocedure wait time was decreased from 16 to 2 days for elective pacing system implantation. The incidence of lead dislodgment in the first, second, and third year of the Ambulatory Pacing System Implantation Program was 20%, 12%, 5%, respectively; compared to 11% for a similar number of cases in previous years done as inpatients. The incidence of new infection was 2.4% compared to < 1% in previous years. Six of the 204 (2%) cases required admission overnight. A total savings of 1,456 bed days ($1,275,450.00; Canadian) has been realized for an equivalent number of cases when compared with previous years. The operational cost was reduced by $3,976.00 per case. It has been shown that the Ambulatory Pacing System Implantation Program has improved client access, and is a safe and economical approach to implantation of cardiac pacing systems.

First derivative of right ventricular pressure, dP/dt, as a sensor for a rate adaptive VVI pacemaker: initial experience.

Ten patients underwent implantation of a rate adaptive ventricular pacing system with a new pulse generator and lead. The unipolar lead has a steroid eluting tip and a pressure sensor. The first derivative of the signal from this sensor, dP/dt, is determined and the pacemaker rate is varied in response to changes in the right ventricular dP/dtMAX. During implantation, dP/dt values were in the range of 180-720 mm Hg/sec. The autothreshold for pacing at 2.5 V remained unchanged 1 month after implantation (0.065 +/- 0.045 msec, range 0.05-2.00 msec) and only slightly increased after 3 months (0.075 +/- 0.045 msec, range 0.05-2.00 msec). A significant correlation existed between the dP/dt measured during implantation and the right ventricular pressure measured by telemetry at follow-up visits (r = 0.93, P = 0.0001). Initial pacemaker programming was performed on the second day after implantation following a short walk and was adjusted subsequent to follow-up visits according to the patient's subjective assessment and in accordance with the results of exercise tests and Holter monitoring. Exercise and Holter tests did not significantly change initial programming. There was a significant correlation between right ventricular systolic pressure and the rate response setting (r = -0.66, P less than 0.05). During dP/dt pacing, all patients felt well, and eight of these reported an improvement compared to nonrate adaptive pacing. The heart rate response to effort and recovery was appropriate. It was concluded that: (1) right ventricular dP/dt is a suitable parameter for controlling the pacing rate; (2) appropriate programming of the dP/dt pacemaker results in a suitable heart rate response to exercise and recovery.

Bradycardia and Syncope in Children Not Controlled by Pacing: Beta‐Adrenergic Hypersensitivity

Cardiac pacing is frequently employed in the therapy of children with syncope and documented bradycardia. This report describes two children, ages 7 and 9 years, who underwent placement of demand ventricular pacing systems for documented bradycardia and syncope. Cardiac catheterization and intracardiac electrophysiological studies failed to show evidence of structural abnormalities, sinus node or conduction system disease, inducible arrhythmias, or VA conduction in each patient. Both patients had persistent symptoms after pacemaker implantation. Autonomic function testing with continuous heart rate and blood pressure monitoring revealed exaggerated beta-adrenergic responses to simple standing and small doses of isoproterenol. Symptoms were completely eliminated with atenolol. In these two children, cardiac pacing alone was not adequate for relief of symptoms. Autonomic mechanisms of bradycardia and hypotension should be considered prior to implantation of permanent pacing systems in children.

Ventricular Cross Stimulation Using a Pacing System Analyzer

Cross stimulation refers to the situation in which a pacing lead positioned in one cardiac chambers results in stimulation of another chamber. We report three cases of ventricular cross stimulation observed at the time of pacing system implantation. The cross stimulation occurred through bipolar atrial and ventricular leads connected in bipolar configuration to a dual chamber pacing systems analyzer. Analysis of events during cross stimulation indicated that the current pathway was occurring within the pacing system analyzer itself, due to low resistance internal connections between the ring electrodes of the atrial and ventricular pacing systems analyzer channels. Cross stimulation within the pacing system analyzer can be eliminated by making the ventricular channel unipolar. Awareness of the phenomenon reported here should assist in the avoidance of the mistaken diagnosis of pacing lead migration and malposition during pacing system implant procedures.

Comparison of Unipolar and Bipolar Active Fixation Atrial Pacing Leads

The purpose of this investigation was to compare the acute pacing and sensing characteristics of a new bipolar active fixation atrial pacing lead with those of a unipolar atrial lead of similar design. Pacing threshold voltage and current, lead impedance, and atrial electrogram amplitude and slew rate were measured at the time of surgery in 28 consecutive patients undergoing DDD pacing system implantation. Eleven patients received a Medtronic 6957J-58 unipolar active fixation atrial lead and 17 patients were given a Medtronic 4016-58 bipolar lead. Both leads are polyurethane-insulated with the distal electrode being a platinum alloy screw-helix with a surface area of 8.0 mm2. There were no significant differences in the threshold voltage (1.01 V unipolar versus 1.05 V bipolar) or current (1.93 mA unipolar versus 1.78 mA bipolar) of the two leads. The mean impedance of the bipolar active fixation lead was 618 ohms compared to 479 ohms for the unipolar lead (p = 0.02). The mean amplitude of the atrial electrogram was 4.64 mV for the bipolar lead and 3.11 mV for the unipolar lead (p = 0.02). The atrial electrogram exceeded 5 mV in 10 of 17 patients with the bipolar lead but zero of 11 with the unipolar lead. There was no significant difference in the mean slew rate of the leads (1.09 V/s bipolar versus 0.73 V/s unipolar; p = 0.18). Over a follow-up period of up to 10 months, all patients remained in either the DDD or DDI modes with no episodes of atrial sensing or pacing failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Programmability: A Clinical Approach

Programmability is a vital characteristic of any implantable pacing system. It allows the physician to alter or adjust pulse-generator behavior at any time during or after pacemaker insertion. This capability has been shown to reduce the need for reoperation to correct sensing and pacing malfunctions. Moreover, programmability can be utilized to prolong battery life, evaluate lead-electrode performance, and individualize the pacemaker prescription.

Pacing Failure Due to Flecainide Acetate

Flecainide acetate is a recently introduced, class 1 antiarrhythmic agent that is highly effective in the treatment of ventricular and atrioventricular/nodal reentrant tachycardias. Although both intravenous and orally administered flecainide are known to cause an increase in the pacing threshold, an abrupt and potentially lethal rise in threshold causing failure of a properly functioning, newly implanted pacing system has not to our knowledge been described. We report such a case to stress the need for caution when using this drug in elderly pacemaker patients.

Do all pacemakers need both antibradycardia and antitachycardia pacing features?

The role of programmed stimulation of the heart in the study of tachycardias was first reported in 1967. 1,2 This was soon followed by the development of implantable pacing systems 3–5 for long-term treatment of reentry tachycardias by timed stimuli. Two basic types of pacemaker systems are available today: 1 for bradycardia support and 1 to interrupt paroxysmal reentrant tachycardias. Both types of systems have undergone considerable technologic refinement and sophistication in the last years. Bradycardia pacemakers, which have additional antitachycardia pacing modes, are being developed. Soon these additional features will be advertised as being of great benefit to the pacemaker population. This study determines the need for all pacemakers to have both antibradycardia and antitachycardia pacing capabilities.

A Combined Atrial/Ventricular Lead for Permanent Dual-Chamber Cardiac Pacing Applications

A new urethane insulated dual unipolar atrial/ventricular transvenous lead has been developed to facilitate implantation of permanent dual-chamber cardiac pacing systems in man. The atrial portion of the lead has tines and is designed to retain a permanent J configuration, while the coaxially situated ventricular lead is freely and independently adjustable and incorporates a ring tip electrode with four urethane tines. Our initial experience with the dual lead in one patient is reported herein and suggests that combined atrial/ventricular pacing leads are feasible and may obviate need for implantation of two separate pacing electrodes in patients being considered for permanent dual-chamber pacing.

Two leads in one introducer technique for A-V sequential implantations.

Thirty‐six (36) consecutive patients underwent implantation of transvenous atrioventricular sequential pacing systems by inserting the atrial and ventricular leads together through one #14 French sub‐clavian introducer. This technique has been easy, reliable and free of complications. (PACE, Vol. 5, March‐April, 1982)

Cardiac Pacing: A Concise Guide to Clinical Practice

Throughout the world 400,000 people have had electrical pacemaker systems implanted, including more than 150,000 people in the United States. Each year 60,000 pacemakers from approximately 20 major manufacturers of pulse generators are implanted in the United States alone. Basic information concerning electrical pacing systems is therefore important to all physicians who treat cardiac patients. In Cardiac Pacing cardiologist Philip Varriale and thoracic surgeon Emil Naclerio, in conjunction with other experts in the technology and practice of cardiac pacing, discuss the electrophysiological concepts of cardiac pacing, the role of pacing in the management of patients with heart block and cardiac arrhythmias, the components of implantable pacing systems, and the techniques of surveillance important for pacemaker longevity. The 329-page text is divided into 23 chapters. Cardiac conduction anatomy, conduction abnormalities, including bifascicular and trifascicular block and sick sinus syndrome, and indications for permanent cardiac pacing are briefly reviewed. Chapters on the

Sleeping Threshold Change Causing Failure of Artificial Cardiac Pacing

To the Editor.— Along with environmental, metabolic, and pharmacologic influences on artificial cardiac pacing, important threshold changes have been reported to occur incident to changes in physical activity. 1 Clinically evident interruption of pacing as the result of these influences has largely been reported as a result of drug administration. 2,3 We have recently seen a patient in whom a pacemaker malfunction occurred only during sleep. Report of a Case.— A 74-year-old white man underwent initial implantation of an artificial pacing system in November of 1962 for a stable arteriosclerotic third-degree heart block. Since that time the patient has undergone 12 different procedures incident to the management of various complications causing pacemaker failure. These include, over the years, skin erosion with extrusion of the pulse generator, wire fracture, infection of the battery pocket, electrode dislocation, battery fatigue, and finally threshold change. He was seen in the office on Dec 23,