Influence of Internal Current and Pacing Current on Pacemaker Longevity

The effects of lower pulse amplitude on battery current and pacemaker longevity were studied comparing the new, small-sized VVI pacemaker, Minix 8341, with the former model, Pasys 8329. Battery current was telemetrically measured at 0.8. 1.6, 2.5, and 5.0 V pulse amplitude and 0.05, 0.25, 0.5, and 1.0 msec pulse duration. Internal current was assumed to be equal to the battery current at 0.8 V and 0.05 msec. Pacing current was calculated subtracting internal current from battery current. The Minix pacemaker had a significantly lower battery current because of a lower internal current (Minix: 4.1 ±0.1 μA; Pasys: 16.1 ± 0.1 μA); pacing current of both units was similar. At 0.5 msec pulse duration, the programming from 5.0-2.5 V puise amplitude resulted in a greater relative reduction of battery current in the newer pacemaker (51% vs 25%). Projected longevity of each pacemaker was 7.9 years at 5.0 V and 0.5 msec. The programming from 5.0–2.5 V extended the projected longevity by 2.3 years (Pasys) and by 7.1 years (Minix). The longevity was negligibly longer after programming to 1.6 V. Conclusion: Extension of pacemaker longevity can be achieved with the programming to 2.5 V or less if the connected pacemakers need a low internal current for their circuitry.     

Intermittent Pacemaker Syndrome: Revision of VVI Pacemaker to a New Cardiac Pacing Mode for Tachy-Brady Syndrome

A patient with tachy-brady syndrome manifested by paroxysmal atrial fibrillation and symptomatic sinus bradycardia and treated by VVI pacing developed pacemaker syndrome during episodes of ventricular pacing. His cardiac pacemaker was revised to a dual chamber system utilizing the new AV sequential DDI pacing mode which eliminated pacemaker-related tachycardias and totally abolished the pacemaker syndrome symptoms. There have been no further episodes of atrial fibrillation, possibly due to elimination of temporal dispersion of refractory periods during bradycardia. The propensity for atrial fibrillation has also been minimized by excluding competitive atrial stimulation during DVI pacing. The DDI mode provides the clinician increased utility and flexibility in the use of AV sequential pacing therapy.     

Telemetry Guided Pacemaker Programming: Impact of Output Amplitude and the Use of Low Threshold Leads on Projected Pacemaker Longevity

In a prospective study, a low threshold screw-in electrode (Medtronic 5078, group I. n = 9) was compared to a conventional active fixation lead (Biotronik Y60BP, group II. n = 9) to investigate whether lower pacing thresholds really translate into longer projected service life of the pacemaker. The leads were implanted in the atrium and were connected to a dual chamber pacing system which included the same ventricular lead (Medtronic 5024) and the same pulse generator model (Intermedics 294–03) in both groups. Eighteen months after implantation, atrial and ventricular pacing thresholds were measured as the charge delivered per pulse [μC] at 0.5, 1.0. 1.5, 2.0, and 3.5 V, respectively. For chronic output programming in both channels, patients capturing at 0.5 V were set to 1.0 V, those capturing at 1.5 V were permanently programmed to 2.0 V with the double of the charge threshold as the safety margin for pacing (“safety charge”). A combination of atrial and ventricular output settings was optimal, if it resulted in minimum battery current drain [μA] as measured by pacemaker telemetry. In both groups, current consumption [μA] decreased significantly as output amplitude was decreased, exhibiting its lowest value at 1.0 V in either channel. All ventricular leads could be programmed to the optimum output amplitude of 1.0 V in groups 1 and 2. As the 2:1 “safety charge” values were almost identical, the ventricular channel essentially contributes the same amount to the battery drain of the pacing system in both groups. In the atrium, all patients of group 1 could be programmed to the optimum output amplitude of 1.0 V with an average pulse duration of 0.42 ± 0.15 ms. In group 2, however, all patients had to be programmed to 2.0 V with a mean pulse width of 0.52 ± 0.15 ms. With the atrial and ventricular output being optimized, the average battery drain of the whole pacing system was 12.19 ± 0.63 μA in group 1 versus 14.42 ± 0.32 μA in group 2 (P < 0.001). As patients were chronically programmed to these output settings, this difference translates into a clinically relevant gain in projected pacemaker longevity of 17 months or 18.3 % (121 ± 4 vs. 104 ± 2 months; P < 0.001). Thus, programming a 2:1 safety margin in terms of charge and optimizing the output parameters by real-time telemetry of the battery current is a useful approach to reduce battery current drain. Making the most of modern lead technology with a different performance in only one channel of an otherwise identical DDD pacing system translates into a significant prolongation of projected pacemaker service life which is of great importance with the increasing awareness of health care expenditures. The gain in projected longevity is mainly due to the option of reducing the output amplitude which is still significantly beneficial well below the nominal voltage of the power source.     

Advanced Pacemaker Diagnostic Features in the Characterization of Atrial Fibrillation: Impact on Preventive Pacing Algorithms

YANG, A., et al .: Advanced Pacemaker Diagnostic Features in the Characterization of Atrial Fibrillation: Impact on Preventive Pacing Algorithms. Pacing algorithms to prevent PAF are mainly based on the suppression of premature atrial complexes (PACs), which play an important role in its initiation. In contrast to 24-hour ambulatory electrocardiograms, advanced pacemaker (PM) diagnostic features are capable of recording AF episodes during long follow-up periods and of characterizing AF in a detailed fashion. For the specific use of these algorithms, a detailed characterization of AF was performed in 91 dual chamber PM recipients with histories of AF. Fifteen patients with episodes of oversensing due to far-field signals or frequent episodes of "2:1-undersensing" of atrial flutter were excluded. The remaining 76 patients had high recurrence rates of AF (median 0.8 episodes/day), however, the majority of episodes lasted <7 minutes. Despite frequent PACs (median 10.8/hour) during sinus rhythm, a median of 66.4% of the AF episodes were preceded by <2 PACs/min before onset. In conclusion, frequent, short-lived AF episodes seem best suited for AF preventive pacing therapies. However, the small number of PACs preceding many AF episodes may limit the efficacy of PAC suppressing algorithms. (PACE 2003; 26[Pt. II]:310–313)     

Ventricular Pacing from the Atrial Channel of a DDD Pacemaker: A Consequence of Pacemaker Twiddling?

ANDERSON, M.H., ET AL.: Ventricular Pacing from the Atrial Channel of a DDD Pacemaker: A Consequence of Pacemaker Twiddling? The breakdown of pacemaker lead insulation under conditions of mechanical stress leading to failure of pacing is well recognized. We present a case where adjacent breakdown of insulation in two unipolar pacing leads resulted in inappropriate ventricular pacing. Replacement of the leads rectified the problem. [PACE, Vol. 13, December, Part I 1990)     

A Right Atrial Mass in the Presence of a Permanent Pacemaker Electrode in a Patient with Polycythemia Vera

A case of a huge right atrial mass that developed 2 years after a permanent pacemaker implantation is described. The patient had a history of polycythemia vera, which is known to present a high tendency towards the development of thrombosis. In light of this fact, we suggest that in similar cases a full echocardiography follow-up should be performed, and long-term anticoagulant therapy should be considered in selected cases.     

Ventricular Lead Transection and Atrial Lead Damage in a Young Softball Player Shortly After the Insertion of a Permanent Pacemaker

We report a case in which permanent pacemaker implantation using a conventional subclavian approach on the throwing side of an avid softball player resulted in complete transection of the ventricular lead and severe damage to the atrial lead. The site of the lead fracture suggested that both leads were crushed between the clavicle and the first rib as a result of the frequent and repetitive arm movement. This case illustrates the importance of the selection of the correct approach for permanent pacing lead insertion.     

Anomalous "VVI" Pacing of a Dual Chamber Pacemaker When Programmed in DDI(R) Mode

We describe the case of a dual chamber rate responsive pacemaker (Relay, model 294-03, Intermedics, Angleton, TX, USA) implanted in a 68-year-old male for sick sinus syndrome, which was not working properly when programmed in the DDIR mode, thus determining occasionally a sort of "VVI" pacing. However, the pacemaker performed well when programmed in the DDDR mode. We discovered that this was not a malfunction of a single device but rather a general behavior of this family of Intermedics dual chamber pacemakers (also not rate responsive), caused by a software problem.     

Lead Dislodgment of a Permanent Pacemaker Due to Removal of a Temporary Pacing Electrode

A 63-year-old male received a transvenous temporary pacemaker for bradyarrhythmia following mitral valve replacement and tricuspid valve annuloplasty. A transvenous permanent pacemaker was implanted the following day due to persistence of the bradyarrythmia and pacemaker dependency of the patient. Later the same day during removal of the temporary pacing electrode the permanent pacing lead was dislodged and had to be operatively repositioned. To avoid this complication, the position of pacemaker leads should be checked postoperatively with a frontal and lateral chest radiograph, and fluoroscopy should be used during removal of a temporary lead.     

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, under- sensing, 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 revaluation of the patient's pacing system following the procedure is mandatory.     

Clinical Evaluation of a Pacemaker Algorithm That Adjusts the Pacing Rate During Sleep Using Activity Variance

DURU, F., et al. : Clinical Evaluation of a Pacemaker Algorithm That Adjusts the Pacing Rate During Sleep Using Activity Variance. Even though rate responsive pacemakers are able to regulate pacing rates based on sensor activity, they are set with a minimum rate that is not adjusted to provide rate decreases during sleep. The aim of this study was to evaluate the performance of the “Sleep Rate” feature, as compared to patient diaries and a validated method that identifies sleep from wrist actigraphy. In 19 patients (15 men; age 69 ± 8 years ) with Pacesetter Trilogy DR+ pacemakers, the base rate and the sleep rate were set to 80 and 50 ppm, respectively. When the patients returned 2 days later, data recorded by the pacemaker and wrist actigraph were analyzed to find the agreement in corresponding sleep/wake periods. In 17 (89%) patients, the pacemaker went into the sleep mode. The total sleep time derived from actigraphy significantly exceeded the time during which the pacemaker was in sleep mode (1156.8 ± 83.4 vs 307.3 ± 77.2 minutes ). Frequent reversions out of the sleep mode limited the total sleep time derived from the pacemaker. Cumulative analysis of the pacemaker data showed that the maximum time in the sleep mode was 78 minutes, and exceeded 1 hour in six instances, 30 minutes in 32 instances, and 15 minutes in 83 instances. Epoch by epoch comparisons revealed a good agreement (93.6 ± 1.8% ) during wakefulness between the corresponding actigraph and pacemaker epochs. However, only 24.6 ± 3.7% of the corresponding epochs during sleep were identical, and the overall agreement was 54.4 ± 3.7% . Except for one patient who reported palpitations, patients did not suffer from a pacemaker rate change. The Sleep Rate feature provides rate reduction during sleep, while assuring rapid frequency response during physical activity. However, the current algorithm does not allow long periods of slow pacing rate during continuous sleep, possibly due to its conservative design and the presence of movement arousals, which has to be improved in future generation algorithms.     

The Impact of a Dedicated "Syncope and Falls" Clinic on Pacing Practice in Northeastern England

This study examined whether the increased demand for pacemaker implants for carotid sinus syndrome (CSS) at the Regional Pacing Service in northeastern England was related to the establishment of a dedicated "syncope and falls" clinic or to the publication of NASPE and BPEG guidelines for pacing symptomatic bradycardia. To this end, pacemaker rates for various indications at this institution were compared with those of a comparable region (Liverpool), as well as with BPEG's national pacemaker database. Findings indicate a distinct impact of the Newcastle syncope and falls clinic on recognition and pacemaker treatment of CSS.     

The Case of the Two-timing Pacemaker

A 71-year-old man with a permanent transvenous pacmaker had recent history of lightheadedness and was brought to the hospital emergency room com-plaining of shortness of breath. His blood pressure was 80/50, pulse rate 148. Administration of a pressor drug restored blood pressure and coincidentally the heart rate returned to 70. His condition was caused by formation of a dendritic spur in the substrate of the programming circuit in his implanted pacemaker, with consequent intermittent doubling of the impulse frequency. Another pacemaker was substituted surgically, and he recovered uneventfully.     

Permanent Pacemaker Positioning Via the Inferior Vena Cava in a Case of Single Ventricle with Loss of Right Atrial-Vena Cava Continuity

Successful dual chamber pacing was achieved by implanting permanent pacemaker leads using an extra-peritoneal approach to the inferior vena cava in a 48-year-old patient with a single ventricle, transposition of the great vessels, and a right atrial pulmonary artery shunt (Glenn's procedure). The pacemaker generator was implanted into a subcutaneous pockel in the anterior abdominal wall.     

Cumulative Hazard Analysis of J-Wire Fracture in the Accufix Series of Atrial Permanent Pacemaker Leads

To permit a more complete analysis of J-wire fracture in the Accufix series of atrial permanent pacemaker leads, the time to occurrence of all known fractures and injuries has been redefined relative to the duration of risk exposure, that is, according to the interval of time between implant and occurrence of the event. This redefinition permits application of a cumulative hazards model to the data, which previously has not been explored. Predictors of J-wire fracture can be tested using this method. This also permits parametric curve-fitting for determination of linearity or constancy of risk of events over time. Results: Among 2,063 Multicenter Study (MCS) leads analyzed, 381 fractures of the J-wire were identified. Stratified analysis based on cumulative hazard curves identified a more open shape of the J-wire as predictive of fracture, which supports the results previously reported based on logistic regression analysis. Fitting a Weibull curve to the cumulative hazard of J-wire fracture gives a shape parameter equal to 0.85. This value indicates that the instantaneous hazard of J-wire fracture decreased over time from implant. Conclusions: (1) The cumulative hazard function can be used to examine predictors of J-wire fracture and preliminary findings support the previously identified predictor of J shape; (2) Based on these analyses, the rate of J-wire fracture appears to decrease slightly as time from implant increases.     

Incidence and Predictors of Permanent Pacemaker Requirement after Transcatheter Aortic Valve Implantation with a Self‐Expanding Bioprosthesis

Background: Previous reports have suggested the occurrence of cardiac conduction disorders and permanent pacemaker (PPM) requirement after transcatheter aortic valve implantation (TAVI). Based on a single‐center experience, we aim to assess the incidence of postprocedural conduction disorders, need for PPM, and its determinants after TAVI with a self‐expanding bioprosthesis. Methods: From August 2007 to October 2009, 32 consecutive patients underwent TAVI with the Medtronic CoreValve (MCV) System (Medtronic Inc., Minneapolis, MN, USA). Three patients paced at baseline and two cases of procedure‐related mortality were excluded. We analyzed the 12‐lead electrocardiogram at baseline, immediately after procedure and at discharge. Requirements for PPM were documented and potential clinical, electrophysiological, echocardiographic, and procedural predictors of PPM requirement were studied. Results: After TAVI, eight patients (29.6%) required PPM implantation due to high‐grade atrioventricular (AV) block. The prevalence of left bundle branch block increased from 13.8% to 57.7% directly after implantation (P = 0.001). Need for PPM was correlated to the depth of prosthesis implantation (r = 0.590; P = 0.001). At a cutoff point of 10.1 mm, the likelihood of pacemaker could be predicted with 87.5% sensitivity and 74% specificity and a receiver operator characteristic curve area of 0.86 ± 0.07 (P = 0.003). Of the seven patients with preexisting right bundle branch block (RBBB), four (57.1%) required PPM implantation after TAVI. Conclusions: High‐grade AV block requiring PPM implantation is a common complication following TAVI and could be predicted by a deeper implantation of the prosthesis. Patients with preexisting RBBB also seem to be at risk for the development of high‐grade AV block and subsequent pacemaker implantation. (PACE 2010; 1364–1372)     

Early pacemaker battery depletion caused by a current leak in the output circuitry: rectification not exchange

Malfunction of a dual chamber system pacemaker due to a current leak in the output circuitry leading to a rapid decline in battery longevity is described. Serial pulse amplitude alterations in defined device configurations enabled location of the defect in the 2.5-V output voltage level; the current leak disappeared in the 5-V output voltage level, and recurred in the 7.5-V output voltage level which combines both 2.5-V and 5-V output circuitries. Reprogramming of pulse amplitudes rectified device malfunction. Circuitry reprogramming of pacemakers with faulty unexplained high battery current can circumvent early replacement in management of device malfunction.