Pacemaker Follow-Up with Prolonged Intervals in the Stable Period 1 to 5 Years Postimplant

This pilot study focuses on pacemaker follow-up in the technically stable period 1–5 years after a pacemaker implantation. Two hundred and thirty selected patients with single chamber pacemakers (215 WI, 15 AAI) had their follow-up intervals prolonged to 2–4 years in this period. Sixty-six patients fulfilled the study period uneventfully and 21 are still pending. Sixty-nine patients had unscheduled visits to the pacemaker clinic. Of these, 7 were reoperated (1 for exit block, 4 had pocket erosions, and 2 were upgraded to DDD). Nine were reprogrammed (1 for sensing failure, 1 had the pulse duration increased, and in 7 the pacing rate was changed). Seventy-four patients died. In 63, the cause of death is known not to be pacemaker related. Six died suddenly, and in five cases, the cause of death is unknown. This study indicates that frequent follow-up visits may be omitted in this period in selected patients with single chamber pacemakers. A prerequisite is that the patients are registered at a pacemaker clinic and have easy access to the physician whenever they suspect pacemaker related problems.     

Effects of Extracorporeal Shock Wave Lithotripsy on Single Chamber Rate Response and Dual Chamber Pacemakers

This study evaluated effects of extracorporeal shock wave lithotripsy on four models of Medtronic implantable cardiac pacemakers. In vitro testing consisted of: (1) unsynchronized pacemaker strapped on the patient with extracorporeal shock synchronized to the patient's native heart rate; and (2) pacemakers suspended alone in water 6 inches from the focal point, synchronizing the extracorporeal shock to pacemaker output. Unsynchronized shocks affected each model of pacemaker differently, i.e., single chamber constant rate pacemakers experienced extended periods of inhibition for more than three pacing cycles while activity-triggered rate response pacemakers exhibited rate increases to the upper rate setting. Dual chamber synchronous pacemakers exhibited intermittently a 59% decrease and a 20% increase in ventricular rate due to inhibition and triggering, respectively, from shock oversensing. Synchronized shocks did not alter the rate of single chamber constant rate pacemakers, but did cause the rate to increase to the upper rate setting for activity-triggered rate response pacemakers. The shock was synchronized to the initial atrial output from the dual chamber pacemaker and caused frequent inhibition of the ventricular stimulus when the ventricular-safety-pace (VSP) feature was programmed off. Programming VSP on reduced the incidence of ventricular inhibition resulting in near normal pacemaker operation. There was neither observable damage to pacemaker components nor spurious reprogramming of pacemaker parameters during the tests. Our studies with one manufacturer's pacemakers suggests that lithotripsy shock effects on implantable pacemakers can be tolerated provided: (1) the single chamber pacemaker is programmed to the demand constant rate modality; (2) the dual chamber pacemaker is programmed to VSP on or to the VVI mode; and (3) the pacemaker distance to the focal point is greater than 6 inches.(ABSTRACT TRUNCATED AT 250 WORDS)     

No gender differences in pacemaker selection in patients undergoing their first implantation

Recent studies have indicated that women were less likely to receive sophisticated pacemaker devices than men. These differences could not be fully explained by demographic and clinical variables. The purpose of the present study was to assess whether a gender related difference might exist in pacemaker mode selection in patients undergoing their first implantation in The Netherlands. Records of first implants (n = 39,217) collected from 1988 through 1997 covering 95% of all implantations in The Netherlands. From this population 33,564 (85.6%) patients were included for final analysis. We observed no significant sex differences in pacemaker selection in patients with atrioventricular conduction disorders and bundle branch block. In patients with sick sinus syndrome, only very old women (> or = 85 years) had more atrial systems implanted than men of similar age (6.5% vs 3.5%), whereas men received more double chamber pacemakers (12.3% vs 10.3%) (P = 0.002). However, the relative distribution of physiological versus nonphysiological pacemakers in this subgroup was similar for men and women. In patients with chronic atrial fibrillation/flutter associated with bradycardia, sex differences were only apparent in the age group of 75-85 years; women received more dual chamber pacemakers (8.8% vs 5.3%) whereas men received more single chamber ventricular pacemakers (94.2% vs 89.8%) (P = 0.0011). With increasing age, sex differences in pacemaker selection were absent, but there was a considerable drop in implantation rate of dual chamber systems. Our study showed no major sex differences in the selection of pacemaker devices. Physicians select pacemaker devices by age rather than gender, which might be a rational choice.     

Pacemaker Diagnostics:

POLLAK, W.M., et al .: Pacemaker Diagnostics: A Critical Appraisal of Current Technology. Diagnostic information retrieved from a pacemaker offers the ability to improve patient care. Pacemaker diagnostic data provides information regarding pacemaker function and activity, lead function, arrhythmia occurrence, and data to aid in optimal pacemaker programming. Current pacemakers incorporate greater storage capabilities, more efficient means of storing and presenting data between follow-up visits, and more options for programming diagnostic functions and algorithms. The cardiac rhythm of the paced patient can be evaluated via real-time intracardiac electrograms at interrogation, surface electrocardiograms, ambulatory electrocardiograms, and by pacemaker stored diagnostic function that may include stored intracardiac electrograms. This article focuses on the various methods of obtaining diagnostic information regarding pacemaker activity, pacemaker function, and diagnostic information on cardiac arrhythmias. The current clinical applicability and limitations of these methods and the use of stored diagnostic data in the clinical follow-up and study of patients with pacemakers is discussed. (PACE 2003; 26[Pt. I]:76–98)     

The Impact of a Manufacturer's Revision of Pacemaker Service Life on the Workload of a Large Pacing Center

In certain batches of a manufacturer's pacemakers, inadequate insulation of the battery cell feed-through mechanism led to internal short-circuiting and premature battery depletion. We describe the impact of the consequent reduction in service life and recommended close supervision of these generators on the follow-up clinics and inpatient workload at a large pacing center. One-hundred and ninety patients had Cordis Gamma series pacemakers implanted between September 1981 and July 1985; 135 have had to undergo premature generator replacement. Eleven of these pacemakers had developed early depletion of rate and 12 no-output failure. Within 3 months of their generator change, 12 patients developed wound sepsis, three of them requiring fiirther system replacement. We calculate that at least 540 extra outpatient appointments, 400 in-hospital patient days and 12 full working days in one of our catheterization laboratories were required to deal with the problems. The pacemaker industry, as well as doctors and technicians involved in pacemaker purchase and implantation, should be aware of the consequences of a major recall not only on workload but also on patient morbidity and anxiety.     

The Isotopic Cardiac Pacer: A Ten-Year Experience

In the past, the battery has been the main cause of pacemaker failure. The isotopic-powered cardiac pacemaker theoretically should provide greater reliability and longevity than pacemakers powered by chemical batteries. We studied 79 isotopic pacemakers in 75 patients for up to 10 years. Four types of Plutonium 238 powered pacemakers were studied. They included 5 VOO, 51 VVI, 14 VVIP, and 9 VVIM pacemakers. A more diverse group of 93 VVI, VVIP and VVIM pacemakers, powered by chemical batteries, were studied as controls. During the course of study the mercury zinc battery has become obsolete. The increased longevity of the lithium battery, at first very promising, has been compromised by the demands firstly of smaller size, and later of more complex circuits. The longevity and reliability of the isotopic pacemakers has been found to be superior to pacemakers powered by chemical batteries. The isotopic fuel cell, because of its greater longevity, may be needed for the increasingly complex circuits required for dual chamber pacemakers, functioning for the control of bradyarrhythmia alone, or combined with tachyarrhythmia control.     

Rate Adaptive Pacing—Clinical Experience with Three Different Pacing Systems

Physiological stimulation can be achieved by either bifocal or rate responsive pacing. The latter pacemakers adapt the heart rate to physical activity by biological signals. Out of many possible approaches only three pacemaker systems for rate responsive pacing are available: the QT-pacemaker (Tx or Quintech), the respiratory biorate pacemaker, and the activity detecting Activitrax. Our own experiences (8 QT, 6 Biorate, 8 Activitrax pacemakers) and a survey of 95 QT- and 37 Biorate pacemakers from 11 centers are reported. The Biorate pacemaker functions without any problems; its present disadvantage is limited programmability. With the Tx pacemaker failing, frequency adaptation (26%) was found more often in the early series, mostly due to voltage polarization at the tip of the electrode. The Activitrax pacemaker gives satisfactory frequency adaptation, largely depending on the activity of the muscles of the shoulder and pectoral region.     

Myopotential Inhibition of Unipolar QRS-inhibited (VVI) Pacemakers, Assessed by Ambulatory Holter Monitoring of the Electrocardiogram

Seventy-four patients with unipolar QRS-inhibited pacemakers (VVI) were Holter monitored to assess the occurrence of pacemaker inhibition caused by skeletal muscle potentials during daily activities. Fifty patients had high-grade atrioventricular block and 24 had sinoatrial disease. Chest wall stimulation prior to monitoring revealed asystole of > 4 seconds duration in 22 patients, and ventricular rates between 25 and 56 beats per minute in 52 patients. Fifty-one patients (69%) had one or more episodes of pacemaker inhibition from myopotentials. Inhibition occurred in all types of pacemakers studies, but was most frequent and of longest duration in patients with Siemens-Elema 207/70 (13/14 patients), Cordis Omni-Stanicor (6/7 patients), CPI Microlith (5/6 patients), and Medtronic 5945 (8/10 patients). This was not unexpected considering the filter characteristics of the pacemakers. Nine patients (12%) presented symptoms which might be ascribed to pacemaker inhibition. The longest asystole observed was 3.2 s. Seven patients had pacemakers spikes falling on or near T-waves of spontaneous heart beats because their pacemakers had been rendered refractory by myopotentials. No serious arrhythmias were seen during episodes of pacemaker inhibition or interference. More emphasis should be put on the improvement of filter characteristics of unipolar VVI-pacemakers. Pacemaker patients with symptoms of myopotential inhibition should be equipped with either a bipolar or ventricular triggered (VVT) pacemaker or with a sensitivity and/or pacing mode programmable pacemaker.     

Radiofrequency Catheter Atrioventricular Node Ablation in Patients with Permanent Cardiac Pacing Systems

Following successful BF ablation of the atrioventricular node (AVN), temporary pacing is necessary prior to insertion of a permanent pacemaker. The risks and inconvenience of temporary pacing could be avoided if a permanent pacemaker is already in place. This study reports the feasibility of RF ablation of the AVN in 27 patients (age 55 ± 17 years, 15 males) with hypertrophic cardiomyopathy and pacemakers, Indications for AVN ablation were drug refractory atrial fibrillation in 24 patients, and rapid AVN conduction preventing septal pre-excitation by DDD pacemaker, inserted for relief of left ventricular outflow obstruction, in three cases. Sixteen patients had DDD devices and 11 patients had VVI devices. During RF ablation, each pacemaker was programmed to VVI at 50 beats/min. The ablation catheter was manipulated with fluoroscopic control to avoid close contact with or disturbance of the pacing leads. In 16 patients, RF ablation was performed immediately following pacemaker implantation but in the remaining patients, the AVN was ablated 6–32 months after pacemaker implantation. The power applied was 25–50 watts for a duration of 15–60 seconds. AV block was achieved in all cases but required 34 ± 36 applications for 16.5 ± 17.8 min/case. RF ablation consistently caused reversion to magnet rate in one patient and temporarily inhibited appropriate pacemaker discharge in another. However, no other pacemaker or lead malfunction was detected so that temporary pacing was not required in any case. At 6 ± 3 months follow-up, all pacemakers were functioning normally without alteration in pacing parameters from baseline. Thus. RF ablation of the AVN can be performed safely in the presence of a recently implanted permanent pacemaker, without temporary pacing.     

Interactions between Pacemakers and Security Systems

Electromagnetic fields arising from a variety of different sources have been shown to interfere with normal pacemaker function. This study evaluated the possible interactions between two modern security systems and different pacemaker types. Fifty–three patients (27 single chamber pacemakers, 25 dual chamber pacemakers) have been tested routinely for their pacemaker function. Thirty–eight patients presented with unipolar sensing and 15 with bipolar sensing. The patients were asked to walk through an installed security system, an antitheft device, and electromagnetic access device with different field strengths while a six–channel ECG monitored the patients. The pacemaker systems were first measured in their basic programmed modes, then the intervention frequency was changed to 100/min and, thereafter, the maximum sensitivity without T wave over– sensing was added. In the security system with the highest field strength (2,700 mA/m), a pacemaker malfunction could be observed in 13% of the monitored patients. In one case, a pacemaker (VVIR) switched to ventricular safety pacing (VOO mode). In the security system with the lower field strength (1,600 mA/m) we found a pacemaker malfunction in 4% of the tested patients. In the antitheft device (50 mA/m). in the electromagnetic access device (300 mA/m), and in pacemaker systems with bipolar sensing, none of these dysfunctions were observed. Phantom programming as described previously did not occur in any of the systems. Persons who are often in the vicinity of security systems should be equipped with a bipolar pacemaker system. Our findings indicate that patients with pacemakers should avoid contact with security systems.     

Paroxysmal Atrial Fibrillation and High Degree AV Block: Use of Single-Lead VDDR Pacing with Mode Switching

Dual chamber rate responsive pacing incorporating a mode switching option is increasingly listed in patients with chronic paroxysmal atrial fibrillation and high degree AV block. Single-lead VDDR pacemakers have been rarely used for this indication. The purpose of this study was to determine thnir reliability of atrial sensing during atrial fibrillation, the percentage of at rial synchronous ventricular pacing, and the behavior of the sinus rate outside the phases of atrial fibrillation. We studied ten patients with a single-lead VDDR pacemaker implanted for this indication. Follow-up visits were performed at predischarge and after 1, 3, 6, 12. 18, and 24 months. During the mean follow-up period of 18.9 ± 6.9 months, the atrial sensing thresholds in sinus rhythm remained stable. Atrial synchronous ventricular stimulation was achieved in 68,7 ±31.2% (median 82.5%) of the whole follow-up time. All patients showed an adequate atrial rate response during sin us rhfthm. Atrial fibrillation was detected by the pacemakers in 24.0 ± 29.8% of time. In 3 of 10 patients the duration of atrial fibrillation showed a steady increase from visit to visit. The sensed amplitudes of atrial fibrillation ranged from 0.1–1.0 mV. A programmed atrial sensitivity of 0.1 mV was necessary to achieve complete sensing of atrial fibrillation. None of the patients experienced tachycardias with optimized pacemaker programming. Single-lead VDDR pacing incorporating a mode-switching option is useful in patients with high degree AV block and paroxysmal atrial fibrillation, since it provides atrial synchronous ventricular pacing in more than two-thirds of follow-up time. In a subgroup of patients, a progressive increase of the time during atrial fibrillation was demonstrated. A reliable detection of paroxysmal atrial fibrillation requires the programming of the atrial sensitivity to its most sensitive value.     

DDIR Versus VVIR Pacing in Patients with Paroxysmal Atrial Tachyarrhythmias

Patients with sinus node dysfunction (SND) in particular those with tachycardia-bradycardia syndrome and patients undergoing atrioventricular nodal ablation procedures for refractory paroxysmal atrial tachyarrhythmias (PAT), are candidates for single chamber (VVIR mode) or dual chamber rate responsive (DDIR mode) systems. To evaluate the benefits and disadvantages of each pacing mode we retrospectively analyzed 33 patients with a history of frequent PAT who received a VVIR (22 patients); or a DDDR pacemaker (11 patients) programmed to the DDIR mode. The mean follow-up time was 25 and 18 months, respectively. Preimplant left atrial diameter was significantly smaller in the DDIR group. Chronic atrial fibrillation developed in 54% of the VVIR patients and 27% of the DDIR group, but this difference was not significant. Complications of patients with VVIR pacemakers included new mitral and tricuspid insufficiency, stroke, pacemaker inlolerance and aggravated congestive heart failure. Patients with DDIR pacemakers had a lower incidence of symptoms and complications. However, this group received more antiarrhythmic medication, required a closer follow-up, and their pacemakers needed frequent reprogramming. Our findings suggest that VVIR is a poor choice for patients with SND, congestive heart failure, and PAT, and that DDIR may be an acceptable alternative.     

Deactivating implanted cardiac devices in terminally ill patients: practices and attitudes

Background: Clinicians may receive requests to deactivate pacemakers and implantable cardioverter-defibrillators (ICDs) in terminally ill patients.
Methods: We describe practices and attitudes regarding deactivation of pacemakers and ICDs in terminally ill patients among physicians, nurses, and others who manage treatment of patients with implanted cardiac devices and among field representatives of device manufacturers. A Web-based survey was provided to Heart Rhythm Society members and to representatives of two manufacturers of implantable cardiac devices. Measurements were the answers of 787 respondents.
Results: Of the respondents, 86.8% reported involvement in requests for ICD deactivation and 77.6% reported involvement in pacemaker deactivation (P < 0.001). Having cared for a terminally ill patient for whom the respondent or a physician had ordered device deactivation was common (95.4% for ICDs vs 84.8% for pacemakers; P < 0.001). Having personally deactivated a device was also common (92.4% for ICDs vs 76.6% for pacemakers; P < 0.001). More respondents said they were comfortable with personally deactivating an ICD than deactivating a pacemaker (56.7% for ICDs vs 34.4% for pacemakers; P < 0.001). Respondents reported that the industry representative is the individual who deactivates the device most of the time (59.3% for ICDs and 49.7% for pacemakers).
Conclusions: Deactivation of implanted cardiac devices in terminally ill patients is common. Practices and attitudes associated with pacemaker deactivation differ significantly from those associated with ICD deactivation. Professional groups should develop guidelines for managing requests for implanted cardiac device deactivation and should clarify the role of device industry representatives in these deactivations.     

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.     

Activity-Controlled Circadian Base Rate

The current pacing rates are clustered around a fixed base rate since pacemaker patients are usually sedentary, resting, or sleeping most of the time. This fixed base rate is either too low for daytime hemodynamic support or too high for nighttime rest and recovery. Multiple Holter studies involving normal individuals have suggested that the resting base rate fluctuates during the course of the day. The circadian base rate (CBR) algorithm was designed to provide patients with a circadian change in paced resting rate and a normal rate distribution. The CBR algorithm, using a sophisticated accelerometer sensor, was developed and tested using the downloaded activity data from patients implanted with Trilogy DR+ pacemakers. Twenty-five patients (19 men, 6 women, age 72 ± 9 years) were studied. Trilogy DR+ is able to record the detailed sensor and system behavior data for a week. During outpatient visits, the pacemaker was interrogated and the data accumulated in the pacemaker memory were downloaded. The CBR algorithm was applied to the activity variance histogram to calculate the base rate and to construct its histogram. The base rates in the CBR histogram are generally below 100 ppm with a distribution that mimics the natural sinus rate distribution of normal subjects. The CBR algorithm provides the highest daytime rates for hemodynamic support and the lowest nighttime rates for cardiac recovery, with a smoothly changing base rate modeling the normal circadian variation in heart rate.     

Incidence of atrial tachyarrhythmias in pacemaker patients: results from the Balanced Evaluation of Atrial Tachyarrhythmias in Stimulated patients (BEATS) study

OBJECTIVES: The prospective Balanced Evaluation of Atrial Tachyarrhythmias in Stimulated patients (BEATS) study compared atrial tachyarrhythmia (AT) detection by means of serial ECG recordings versus device detection. BACKGROUND: The annual incidence of AT in patients with dual-chamber pacemakers may be significantly underestimated based on ECG and Holter recordings. METHODS: A DDD(R) device capable of AT-triggered dual-channel electrogram (EGM) storage was implanted in 254 patients (70 +/- 11 years, 159 men) with a class I pacing indication. Patients were seen at 6, 26, and 52 weeks after pacemaker implantation. At all visits, symptoms were checked, surface ECGs were recorded including a 24-hour Holter recording at 6 weeks, and the pacemakers were interrogated. Primary study endpoint was AT documentation by surface ECG/Holter versus stored EGMs. Secondary endpoints consisted of the association between patients' symptoms and AT documentation, and of the AT incidence depending on pacing indication and a history of AT. RESULTS: ATs were documented by ECG/Holter recordings in 37 patients (15%) and by stored EGMs in 137 patients (54%) (P < 0.0001). Symptoms were absent in 108 of 137 patients (79%) with device-documented AT but present in 70 of 117 patients (60%) without AT documentation. AT documentation was more frequent in patients with a history of AT but not in patients with sinus node compared to AV node disease. CONCLUSION: ATs occur in pacemaker patients significantly more frequently than estimated by ECG/Holter recordings. Only the analysis of device-stored EGMs allows reliable assessment of the AT burden.     

Noninvasive Conversion of Atrial Flutter Using a Multiprogrammable DDD Pulse Generator

. A patient with sick sinus syndrome and resistant paroxysmal atrial flutter was treated with amiodarone and implanted with a Medtronic 7005 DDD pacemaker. Following discontinuation of amiodarone, an episode of sustained atrial flutter was converted to sinus rhythm by noninvasive rapid atrial pacing in the outpatient ciinic. This case illustrates one of the many capabilities for arrhythmic intervention using currently availabie implanted pacemakers.     

Electronic Article Surveillance: A Possible Danger for Pacemaker Patients

In order to evaluate if antitheft devices commonly designed as electronic article surveillance (EAS) systems can be dangerous for pacemaker patients, in vitro and in vivo studies were made in close cooperation between a pacemaker center and an EAS designer. Three types of EAS radiation including radiofrequency, magnetic, and pulsed electromagnetic fields were applied to various pacemakers. The in vitro study consisted of exposing to the EAS fields 28 pacemakers connected to unipolar leads. Radiofrequency fields and pulsed electromagnetic fieids evoked minor effects and no prolonged inhibitions. When exposed to magnetic fields, most of the pacemakers switched to "fixed rate" pacing, but inhibitions were observed in 13 pacemakers exposed to 300 Hz, and in 14 pacemakers exposed to a 10-kHz magnetic field when they were moved at cardiac frequencies within the fields. The in vivo study was made on 32 volunteers treated by 26 different pacemakers: 22 single chamber and ten dual chamber. All patients had been monitored in the pacemaker clinic and pacemakers were working well. Radiofrequency and pulsed electromagnetic fields did not affect the pacemaker function. Magnetic interference evoked prolonged inhibition of seven out of the ten dual chamber pacemakers, causing brief asystole in patients being continually paced. None of the dual chamber pacemakers incorporated "safety stimulation intervals" after ventricular bianking. The EAS artifact was sensed after the ventricular blanking causing a cross-talk ECG pattern. No reprogramming was induced by the electromagnetic fields. This experience demonstrates that certain EAS may be dangerous for pacemaker patients. Following this cooperative study a pacemaker safe EAS circuit delivering short bursts of magnetic fields has been designed.     

Acceptance of elective bradypacing by patients: an African perspective

Background: In our practice, we noticed that patients respond differently when pacemaker insertion is recommended to them. We then saw the need to study how African patients accept elective pacemaker implantation. Aim: The study was conducted to determine African patients’ responses to elective pacemaker insertion. Patients and Methods: We recruited patients who reported at our outpatient clinic with indications for elective pacemaker insertion. The study period lasted 64 months from September 1999. The patients were counseled before insertion and we sought their consent before being recruited for the study. Five possible responses were used to grade acceptance. They were followed up for 12 months each. Patients who were brought in emergency and those who refused participation were excluded. Those who missed follow‐up were also dropped. Results: Ninety‐two patients (n = 92) met our study criteria after dropping eight patients who missed follow‐up clinic attendance. Most of the candidates (71.7%) felt they had no options but to accept pacemakers at the time of operation. The remaining candidates either accepted the procedure with hope or wholeheartedly. Most of the candidates migrated up the ladder of acceptance over the 12‐month period. Discussion and Conclusion: We concluded that most patients would accept pacemakers wholeheartedly over time. (PACE 2012; 35:58–61)     

Myopotential Interference in Unipolar Rate Responsive Pacemakers

The effects of myopotential interference on unipolar rate responsive pacemakers were assessed in 22 patients. Six types of pacemakers (from four manufacturers) were studied: five TX2 (QT sensing), seven Biorate (five RDP3 and two MB-1, respiratory rate sensing), seven Activitrax (activity sensing), two Medtronic 2503 (dP/dt sensing), and one Sensolog P703 (activity sensing). Provocative tests using arm exercises were performed in both VVI and rate responsive modes. At nominal sensitivity settings (1.8-2.5 mV), 55% of these patients were myopotential positive for at least 1 provocative test. Pressing the palms together was found to be the most sensitive provocative test. Rate response was achieved with treadmill exercise (all patients), hyperventilation (RDP3 and MB-1) and tapping (Activitrax) or wobbling the pacemaker in its pocket (Sensolog). During continued rate acceleration, myopotential interference was induced by arm exercises. The duration of inhibition was shorter when the provocative tests were performed during rate response compared to that occurred at rest. Short periods of myopotential interference resulted in temporary inhibition of pacing but rate response continued immediately on removal of the interference. In one patient with a RDP3 pacemaker, a prolonged episode of myopotential interference during treadmill exercise resulted in reversion of the pacemaker to the interference mode. Appropriate adjustment of the sensitivity setting effectively controlled the symptoms in most patients. However, one patient with a QT sensing pacemaker and symptomatic myopotential interference required programming to the VVT pacing mode. Two out of five patients with RDP3 required pacemaker replacement because of uncontrolled myopotential interference.(ABSTRACT TRUNCATED AT 250 WORDS)