Inframammary Pulse Generator Placement for Maximizing Cosmetic Effect

Today with the expanding clinical role of cardiac pacing and more advanced methods of detecting pacing problems, more and more young patienls are being idenlified as Candidales for permanenl pacing. Concern has been expressed by young female patients over the cosmetic effects of pacemaker surgery. Two young female patients were evaluated from a physiologic and cosmetic point of view. The electrodes were placed via the percutaneous approach. The pulse generator was treated as a breast implant using The usual recommended plastic surgeon's inframammary approach. In both cases, optimal cosmetic effect was achieved without any external evidence of the pacemaker system.     

Inframammary pulse generator placement for maximizing cosmetic effect

Today with the expanding clinical role of cardiac pacing and more advanced methods of detecting pacing problems, more and more young patients are being identified as candidates for permanent pacing. Concern has been expressed by young female patients over the cosmetic effects of pacemaker surgery. Two young female patients were evaluated from a physiologic and cosmetic point of view. The electrodes were placed via the percutaneous approach. The pulse generator was treated as a breast implant using the usual recommended plastic surgeon's inframammary approach. In both cases, optimal cosmetic effect was achieved without any external evidence of the pacemaker system.     

Entrapment of Tined Leads

A rare complication is described, in three patients. The tined tip of a ventricular pacemaker electrode was entrapped in the chordae of the tricuspid valve and could not be removed by subtle manipulations in two patients. In one patient, the electrode was removed with partial rupture of the tricuspid valve. The two electrodes remained in the entrapped position and new electrodes were inserted in all three cases. No clinical sequelae were found during follow-up of at least 24 months.     

Criteria for pacemaker explant in patients without a precise indication for pacemaker implantation

Unnecessary pacemaker implantation may cause significant social and psychological consequences, the inconvenience of periodic office visits, and the expense of pulse generator replacement. Establishing adequate criteria for explantingpacemakers is crucial and has notyet been described. This study presents the results of a study protocol for explanting the pacemaker in patients without a clear indication for pacemaker implantation. Seventy pacemaker users without a clear reason for the implantation were included in the study conducted from August 1986 to November 1998 and were prospectively followed. The investigation consisted of clinical and neurological evaluations, echocardiogram, exercise testing, and tilt table testing. When these tests were negative, the pulse generator energy and stimulation rates were reprogrammed to the lowest values. Periodic Holter monitoring was conducted during follow-up. When asymptomatic for 1 year, patients underwent an electrophysiological evaluation of sinus and atrioventricular junction function and ventricular vulnerability. When the electrophysiological study was negative, pacemaker explantation was performed. Of the 70 patients, 35 had their pacemaker explanted; 3 were excluded due to a positive tilt table test and electrophysiological study, and 3 are waitingfor pacemaker explantation. Mean follow-up after pacemaker explantation was 30.3 months, and all patients remained asymptomatic, exceptfor one patient who died of a noncardiac cause. Critical analysis of pacemaker users without a well-established indication is justified because it may allowpacemaker explant in a significant proportion of these patients, and it may bring considerable social, economic, and psychological benefits.     

Assessment of the Subclavian Vein in Patients with Transvenous Pacemaker Leads

Thrombosis of the subclavian vein can occur after the implantation of transvenous pacemaker electrodes. Although this is seldom followed by thromboembolic complications, it can cause problems when replacing the leads. To assess the impact of the pacemaker leads on the subclavian vein, a study using nonin-vasive duplex sonography was performed on 56 patients at an average of 41 months after the implantation. Forty-three percent of the patients were found to have a normal function of the subclavian vein, 46% developed pathological changes of the vessel wall, and 11% occluded. These changes rarelv caused symptoms, and, therefore, had little clinical significance. Moreover, the occlusion rate was found independent of the patient's age, the patient's sex, the number of electrodes, the procedure of implantation, and even the time from implantation. As a result, the clinical diagnosis of occlusion is uncertain. Therefore, duplex sonography is recommended as an easy means of excluding a totally thrombosed subclavian vein prior to replacing pacemaker leads.     

Ventricular Fibrillation Produced by Stimulation of External Transthoracic Electrodes—An Experimental Study

The threshold for ventricular fibrillation was determined in 12 pentobarbital anesthetized dogs using transthoracic electrodes located at the optimal axillary electroventilation sites. Electroventilation is the name used to designate inspiration produced by stimuli applied to body surface electrodes. The optimal stimulation site for electroventilation was first determined using hand-held electrodes. Then electrodes, 4.1 cm in diameter, were sutured bilaterally to the optimal anterior axillary stimulation site. The threshold current for producing ventricular fibrillation was determined using single pulses ranging from 0.1-10 msec in duration delivered during the vulnerable period of the cardiac cycle. Fibrillation was produced in all dogs with the 10- and 5-msec pulse durations, in 11 dogs with 0.3-msec, in 6 dogs with 0.2-msec, and in 1 dog with 0.1-msec pulse duration. In all dogs, the current required to produce ventricular fibrillation increased greatly as the pulse duration was decreased. The current required for fibrillation was much in excess of that required to produce one tidal volume. With the longer duration pulses, the ratio was about 80. With the 8 microseconds duration pulses used for electroventilation the estimated ratio is about 800.     

Limitations of Pacemaker System Analyzers for the Evaluation of Implantable Pulse Generators

A variety of commercial pacemaker system analyzers have been used to evaluate the electrical performance of pulse generators prior to implant or at the time of reoperation for pacemaker malfunction. We evaluated the ability of seven commercially available pacemaker system analyzers to provide the data required to determine if a given pulse generator was operating according to its manufacturer's specifications. While all pacemaker system analyzers provided accurate data for rate and pulse duration, values displayed for amplitude and sensitivity were inconsistent due to the methods each pacemaker system analyzer employed to measure these parameters. Overall, 22% of representative test sequences yielded data which would have resulted in the inappropriate rejection of the subject pulse generators for implantation. These observations suggest that pacemaker system analyzers are not suitable for evaluating all pulse generators. Moreover, physicians must be aware of these deficiencies in order to avoid the pitfalls of relying exclusively on pacemaker system analyzer data when troubleshooting pacemaker malfunction. (PACE, Vol. 4, November-December, 1981)     

Long-Term Reliability of Single Lead Atrial Synchronous Pacing Systems Using Closely Spaced Atrial Dipoles: Five-Year Experience

To assess the long-term capability of single atrioven ticular (AV) lead VDD pacing systems using close atrial dipoles to assure reliable atrial guided pacing, the safety and efficacy of 86 VDD units implanted in 73 patients at a single center since November 1988 was reviewed. All patients suffered from advanced AV block with normal sinoatrial function. Sixty five patients received a LEM/CCS Twinal 30/30S system, four patients received a Vitatron-Saphir system, and four patients received a Medtronic Thera VDR 8348 system. All patients underwent provocative tests in search of myopotential interference, and Holter recordings; in a group of patients who underwent pacemaker replacement a comparison was made between implant and replacement measurements. The mean follow-up duration was 27.3 months. A high percentage of successfully VDD paced patients and a low incidence of pacemaker malfunction, regularly solved by pacemaker reprogramming, was reported. Atrial signal amplitudes comparable to those measured at implant were found at replacement in all patients. These data support the long-term reliability of single AV lead VDD pacing systems with closely spaced atrial dipoles, as well as stable atrial sensing by floating bipolar atrial electrodes and effective atrial synchronous ventricular pacing over time.     

Cardiac Electrodes and Electrograms: Some New Observations and Concerns

Electrode studies have been performed with dead animal tissue and a variety of other materials immersed in saline solution and compared with studies in the canine heart (live and arrested) in an attempt to delineate both normal and anomalous signals sensed by pacemaker electrodes or obtained during diagnostic electrogram recording of cardiac activity. The data from these studies could be useful for defining the origin of artifacts and a variety of other phenomenon such as "fractured" QRS complexes, acute ST segment elevations, His bundle oscillatory signatures, and unexplained potentials synchronously associated with cardiac events. The studies verify that artifacts can be generated in an electrolyte medium by rubbing electrodes against insulators or biologic materials and by inducing motion between common pole materials of an active electrode system. The studies suggest that some of the grasping electrodes in current clinical use may be subject to self-generating artifacts associated with cardiac-induced frictional motion between the constituent materials employed in the electrode design.     

Malfunction of a Sheath-Retracting Active-Fixation Pacemaker Electrode Due to Impacted Endocardium

A patient is described in whom a sheath-retracting active-fixation pacemaker electrode dislodged shortly after successful transvenous implantation in the right atrial appendage. Attempts to reposition the lead were unsuccessful. Examination of the explanted electrode disclosed that inability to reposition the electrode was due to the fact that impacted tissue around the electrode "screw" prevented its being re-advanced out of its polyurethane housing. (PACE, Vol. 5, March-April, 1982)     

Infections in Transvenous Cardiac Pacemakers: Two More Cases

Two patients with metastatic pacemaker infections, one caused by Pseudomonas aeruginosa, 5 months after implantation, and the second by Streptococcus pneumoniae, 8 years after implantation, were treated successfully by removal of the pacemaker systems. Infection reoccurred in the patient with Pseudomonas aeruginosa, who initially underwent partial pacing system removal allowing the atrial lead to remain. Repeat partial atrial lead removal and contralateral pacemaker implantation was followed by clinical infection, which was resolved when both the implanted atrial lead fragment and the recently implanted pacemaker were both removed. Removal of all hardware is required for cure of pacemaker infection.     

Pharmacotherapy of Amanita phalloides poisoning using silybin

A total of 18 cases of Amanita phalloides poisoning was treated by combined chemotherapy during 1980 and 1981. After attempted primary elimination of the toxin all patients received silybin as basic therapy mainly by infusion and, in two instances, silymarin orally. In order to investigate the effect of silybin therapy a retrospective study of the followed-up case records was made. The cases were arbitrarily classified into three groups of severity (light, medium and severe) according to clinical and laboratory findings. A close relationship was found between the severity of the intoxication and the time elapsed before commencement of silybin therapy. The time interval between mushroom intake and the commencement of the silybin administration averaged 71.5 hours in the "severe" group compared with 46 and 33.8 hours, respectively, in the "medium" and "light" groups. The mean silybin dosage was 33 mg/kg body weight/day; the mean duration of silybin therapy was 81.6 hours. With the exception of one fatality in a particularly high dosage suicidal intoxication, all patients survived. Administration of silybin within about 48 hours after mushroom intake seems to be an effective measure to prevent severe liver damage in Amanita phalloides poisoning.     

A Comparison between Conventional and Basket Transvenous Electrodes

Three transvenous electrodes, two of a conventional type and one in the shape of a wire basket, were compared. In order to make a valid comparison, the electrodes were all attached to the same kind of lead. The conventional large and small surface electrodes showed no difference in early complication rate. The wire basket electrode, however, had significantly fewer early complications than the others. This was true whether the patients underwent a two- or a one-step procedure, and whether the surgery was done by experienced or inexperienced pacemaker surgeons. When inserted by experienced surgeons in a one-step procedure, the wire basket electrodes had an early complication rate of only 1.2%. Since this unrefined electrode that allows tissue ingrowth for improved anchoring has shown such good results, it is likely that other electrodes that have been perfected, of a hollow or porous design, will also be advantageous to the patients and show good results.     

The Effects of Percutaneous Catheter Ablation on Preexisting Permanent Pacemakers

VANERIO, G., ET AL.: The Effects of Percutaneous Catheter Ablation on Preexisting Permanent Pacemakers. Study Objective: Determine the effect of percutaneous catheter ablation (CAI on permanent pacemakers. Measurements and Results: Twenty-three patients who underwent CA at The Cleveland Clinic Foundation from September 1983 to January 1990, and had a previously implanted pacemaker were studied. Electrocardiographic data during the CA procedure and clinic data including pacemaker evaluations were analyzed. Fifty-two percent (12/23) of the pacemakers malfunctioned: five developed transient ventricular loss of capture; two undersensing; one oversensing; three could not be interrogated or programmed, and one did not respond to the magnet test. Four patients developed syncopal episodes and two severe dizziness after the procedure. All had their pacemakers replaced. In total, seven were explanted. Destructive analysis by the individual manufacturer identified pacemaker circuitry failure in five. Unipolar pacemakers and anodal ablation procedures had more frequent and severe malfunctions, but the difference was not statistically significant. Conclusions: Pacemaker malfunction is frequent during CA. It may be prevented by programming the pacemaker, when possible, to the nonfunctioning mode (000 mode). Temporarily disconnecting the pacemaker during ablation requires further evaluation as an alternative approach. Close follow-up can detect pacemaker malfunction and prevent complications.     

Rate Control with an External SO2 Closed Loop System

In 20 volunteers (mean age 35.5 y) and 12 pacemaker patients (mean age 68.7 y), central venous oxygen saturation (SO₂) was monitored continuously by means of an optical sensor integrated in an external transvenous pacing lead placed in the right ventricular cavity. From the SO₂ signal recorded at rest and during various modalities of exercise, an algorithm for controlling pacing rate of an external pacing system was developed. An open loop system was used in the volunteers, allowing the comparison of the computed pacing rate with the individual intrinsic heart rate. There was an excellent correlation between the two frequencies as far as the dynamic characteristics and the steady state relationship were concerned. In five pacemaker patients who were stimulated via the external lead, a closed loop control of pacing rate was used. In one patient with a DDD pacemaker implanted for third degree AV-block, the rate response of the SO₂ driven pacemaker was well in accordance with the rate attained with the implanted atrial triggered system. With both pacing modes, exercise capacity as determined on a symptom limited treodmill test was identical. In four patients (3 AV block III, 1 bradyarrhythmia) an improvement in exercise tolerance up to 65 percent could be demonstrated with the rate responsive pacing mode. In all patients, it could he shown that an autoregulating pacemaker system with SO₂ is an open possibility.     

Intraoperative Recordings of Monophasic Action Potentials with Chronically Implantable Pacemaker Leads

Since the development of fracially coaled Iridium electrodes recordings of monophasic action potentials are possible. Intraoperative recordings of MAP from 15 pacemaker implantations were done after positioning the chronically implantabie pacemaker leads (Biotronik, Berlin, Germany) in the right ventricle by using five screw-in electrodes and ten anchor electrodes. Intraoperative recordings of MAP are possible with all implanted pacemaker leads. The recordings of typical MAP signals were always accompanied with stable electrode positions and good sensing and pacing characteristics.     

A Multicenter Evaluation of a Single-Pass Lead VDD Pacing System

Since June 1985 until April 1989, 237 patients (130 males, 107 females, aged 22 to 95 years, mean 71) with symptomatic AV conduction disturbances and competent sinus node, were implanted with a single-pass lead VDD pacing system in 30 centers and followed-up for at least 6 months. The ventricular pacing lead incorporated two atrial ring 3-cm apart electrodes, positioned within the right atrial cavity without contact with the heart wall, in order to detect the atrial activity, which is differentially processed by the pacemaker. At implant, mean atrial electrogram amplitude, derived from a custom pacemaker system analyzer (PSA) with the same input filter of the pacemaker was 1.7 +/- 0.8 mV (n = 93). In all cases, atrial sensitivity at implant was the default value +/- 0.15 mV. The atrial tracking capability of the pacing systems was assessed within the month and every 6 months after implantation by means of clinical evaluation, resting ECG, 24-hour Holter monitoring and the following tests: exercise stress testing, mental stress, isometric exercise, and nifedipine test. These tests evoke an increase of atrial rate in consequence of metabolic needs or as a reflex response. The criterion used to evaluate the correct operation of the system was the percentage of atrial synchronization. This was defined as the ratio between atrial triggered ventricular paced complexes and all ventricular paced complexes. All monitorings showed a ratio higher than or equal to 98% in a percentage of patients not lower than 95%. Mean follow-up was 385 days (range 183-1,370 days).(ABSTRACT TRUNCATED AT 250 WORDS)     

Acute and Chronic Clinical Performance Comparison of a Porous and a Solid Electrode Design

The long-term performance of porous and solid ring-tipped electrodes was compared in clinical use over a one-year period. Each of the two electrode designs was implanted in 22 patients in conjunction with an output-programmable pacemaker. Implant evaluation included impedance, height of sensed R wave, and a strength-duration curve. Threshold determination by pulse-width programming was performed at the time of implant and at one week, two weeks, two months, six months, and one year. There were no dislodgements with either electrode. No significant differences were noted in the acute parameters or in chronic thresholds.     

In Vitro Estimation of the Electrical Performance of Bipolar Pacing Electrode Systems

With the current interest in bipolar stimulation, there is a need for greater understanding of the electrical contributions of the two electrodes in this type of pacing. This has been investigated using a specially designed cell in which an electrode under test was immersed in a buffered saline solution (pH 7.42) at 37–38°C. Four electrode types were studied: a single stimulating electrode (6 mm² dish tip, Pt-black coated) and three indifferent electrodes. The indifferent electrodes were a 41 mm² polished Pt ring, a Pt-black coated version of the same electrode, and a titanium pacemaker enclosure which was included to allow comparison with the unipolar situation. These electrodes were tested individually against a chlorided silver reference electrode of negligible (1–2Ω) impedance, the results being processed in such a way as to allow estimation of the properties of the stimulating electrode taken in combination with each of the indifferents. Constant current pulses (1–10 mA amplitude, 0.5 and 1.0 ms duration) were applied and measurements made from the resulting voltage waveforms. These were V₁ and V₂, the potential at the leading and trailing edge of the pulse, and Va, the post-pulse potential at 20 ms following the trailing edge. The potential V₁ - V₂ is electrode dependent and allows the determination of the energy loss due to polarization to be calculated. Sinusoidal AC signals (0.1 Hz-10 kHz, 20 μA maximum amplitude) were also employed, allowing determination of sensing impedance. Under all conditions, the calculated performance of the stimulating electrode with the coated ring was nearly equivalent to that with the pacemaker enclosure. The performance with the uncoated ring was in all respects markedly inferior, displaying almost double the energy loss on pulsing, post-stimulus potentials an order of magnitude larger and sensing impedance increased by a factor of up to 8.