Longevity of dual chamber pacemakers: device and patient related determinants

METHODS FOR INVESTIGATING CONTRACTION CHARACTERISTICS OF A PART OF MUSCLES FOR IMPLANTABLE POWER GENERATION SYSTEMS

To develop a power generation system as a solution to the power supply problems of small active implantable medical devices, we proposed a new method to examine muscles using skeletal muscle contraction through electrical stimulation. Realization of the system requires data on the contraction characteristics of a part of the muscles through which blood flows; thus, a dedicated setup was built and verified using a goat. The connecting parts were attached to two points in the large muscle of the goat’s trunk; one was fixed and the other slid along the guide. The distance and force between the two points, approaching each other, were measured by contracting the muscle between the points using electrical stimulation and pulling the measurement cart. The contraction distance and force were measured simultaneously, and the dynamic work of the contraction was calculated. The muscle work occurred with almost the same time delay regardless of the load, and the work tended to be greater when the contraction force, and not the contraction distance, of the muscle was large. The setup is physiological, simple, and versatile. Our setup can potentially be used in the development of implantable power generation systems and in other related fields.

Wireless Power Transfer Techniques for Implantable Medical Devices: A Review

Wireless power transfer (WPT) systems have become increasingly suitable solutions for the electrical powering of advanced multifunctional micro-electronic devices such as those found in current biomedical implants. The design and implementation of high power transfer efficiency WPT systems are, however, challenging. The size of the WPT system, the separation distance between the outside environment and location of the implanted medical device inside the body, the operating frequency and tissue safety due to power dissipation are key parameters to consider in the design of WPT systems. This article provides a systematic review of the wide range of WPT systems that have been investigated over the last two decades to improve overall system performance. The various strategies implemented to transfer wireless power in implantable medical devices (IMDs) were reviewed, which includes capacitive coupling, inductive coupling, magnetic resonance coupling and, more recently, acoustic and optical powering methods. The strengths and limitations of all these techniques are benchmarked against each other and particular emphasis is placed on comparing the implanted receiver size, the WPT distance, power transfer efficiency and tissue safety presented by the resulting systems. Necessary improvements and trends of each WPT techniques are also indicated per specific IMD.

Hydrogel Leclanché Cell: Construction and Characterization

A liquid-to-gel based Leclanché cell has been designed, constructed and characterized for use in implantable medical devices and other applications where battery access is limited. This well-established chemistry will provide reliable electrochemical potential over a wide range of applications and the novel construction provides a solution for the re-charging of electrodes in hard to access areas such as an internal pacemaker. The traditional Leclanché cell, comprised of zinc (anode) and manganese dioxide (cathode), conductive carbon powder (acetylene black or graphite), and aqueous electrolyte (NH4Cl and ZnCl2), has been suspended in an agar hydrogel to simplify construction while maintaining electrochemical performance. Agar hydrogel, saturated with electrolyte, serves as the cell support and separator allowing for the discharged battery suspension to be easily replaced once exhausted. Different amounts of active anode/cathode material have been tested and discharge characteristics have been plotted. It has been found that for the same amount of active material, acetylene black batteries have higher energy density compared to graphite batteries. Graphite batteries also discharge faster compared to acetylene black batteries. The results support further development of liquid batteries that can be replaced and refilled upon depletion.

Design optimization of contactless generator for implantable energy harvesting system utilizing electrically-stimulated muscle

We propose an energy harvesting device driven by a contraction of an electrically-stimulated skeletal muscle for an alternative battery of implantable medical devices. In order to realize a durable generator, we proposed a contactless plucking mechanism utilizing parallel leaf springs and magnets, with which the generator can be driven without friction. By utilizing this mechanism, the generator can be driven not only in a contraction phase, but also a relaxant phase. We optimized the stiffness of the parallel leaf springs, air gap between the magnets, and magnetic circuit in order to maximize generated power of the generator. The generated power of the prototype in nonliving environment was evaluated. The result showed the protype could achieve 35.8 μW, the value of which is enough to drive the implantable medical devices. Finally, the generated power was evaluated in the ex-vivo experiment using a gastrocnemius muscle of a toad with a weight of 193.4 g. In this experiment, the generator achieved 18.1 μW from only 3.5 g of the skeletal muscle. Also, we confirmed that the generated power exceeded the power consumption of the electrical stimulation on the skeletal muscle. Hence, we concluded the results showed the feasibility of the energy harvesting system with proposed mechanism.

A wireless optical power system for medical implants using low power near-IR laser

An alternative method of transcutaneous wireless optical energy supply to an artificial cardiac pacemaker has been conceived, thereby negating the possibility of electromagnetic interference. In this research, a comparative analysis is made between two distinct arrays of photovoltaic cells, consisting of two different geometries. Being powered by a 5 mW 750 nm laser, that has a different spot size for each topology; both models are tested by their ability to charge a 150 mAh rechargeable LiPo battery, while being embedded underneath a layer of skin tissue. This system in turn, regulates the power supplied to a low power medical implant (<; 10 mW), in the place of conventional batteries. For a charging period of 60 minutes, results indicate that a pacemaker utilizing this system can sustain operation for nearly 85 hours, without any noticeable side-effects or changes in temperature.

Trends in service time of pacemakers in the Netherlands: a long-term nationwide follow-up study

AIMS

After decades of experience and strongly improved technology, service time of pacemaker generators is expected to increase. To test this hypothesis, we conducted a retrospective review of a large cohort of patients with a pacemaker.

METHODS

We reviewed data collected between 1984 and 2006 in the first national Dutch pacemaker registry. This registry covered 96% of all generators implanted. We analysed the time of and reason for explantation of pacemaker generators. A 7-year follow-up interval after first implantation and following replacements was used to analyse changes over time.

RESULTS

During 22 years of data collection, nearly 97,000 first pacemaker generators were implanted. A total of 27,937 (22.4%) generators were explanted within a mean of 6.3 (standard deviation 3.3) years. Reasons for approximately 60% of these explantations were 'end of life' of the pacemaker generator or elective system change. Complications or failures such as infections and recalls accounted for approximately 20% of the explantations. For the remaining 20%, the reasons for explantation had not been registered.

CONCLUSION

Despite progress in technology, a substantial proportion of pacemaker generators is explanted before its expected service time, with one in five generators being replaced due to technical failures, infections or other complications. Furthermore, the time interval between pacemaker implantation and explantation due to normal 'end of life' (battery EOL) decreased. Infections continue to rank highly as a cause for pacing system replacement, despite all current preventive measures.

Wireless Power Transfer Strategies for Implantable Bioelectronics

Neural implants have emerged over the last decade as highly effective solutions for the treatment of dysfunctions and disorders of the nervous system. These implants establish a direct, often bidirectional, interface to the nervous system, both sensing neural signals and providing therapeutic treatments. As a result of the technological progress and successful clinical demonstrations, completely implantable solutions have become a reality and are now commercially available for the treatment of various functional disorders. Central to this development is the wireless power transfer (WPT) that has enabled implantable medical devices (IMDs) to function for extended durations in mobile subjects. In this review, we present the theory, link design, and challenges, along with their probable solutions for the traditional near-field resonant inductively coupled WPT, capacitively coupled short-ranged WPT, and more recently developed ultrasonic, mid-field, and far-field coupled WPT technologies for implantable applications. A comparison of various power transfer methods based on their power budgets and WPT range follows. Power requirements of specific implants like cochlear, retinal, cortical, and peripheral are also considered and currently available IMD solutions are discussed. Patient's safety concerns with respect to electrical, biological, physical, electromagnetic interference, and cyber security from an implanted neurotech device are also explored in this review. Finally, we discuss and anticipate future developments that will enhance the capabilities of current-day wirelessly powered implants and make them more efficient and integrable with other electronic components in IMDs.

Implantable power generation system utilizing muscle contractions excited by electrical stimulation

An implantable power generation system driven by muscle contractions for supplying power to active implantable medical devices, such as pacemakers and neurostimulators, is proposed. In this system, a muscle is intentionally contracted by an electrical stimulation in accordance with the demands of the active implantable medical device for electrical power. The proposed system, which comprises a small electromagnetic induction generator, electrodes with an electrical circuit for stimulation and a transmission device to convert the linear motion of the muscle contractions into rotational motion for the magneto rotor, generates electrical energy. In an ex vivo demonstration using the gastrocnemius muscle of a toad, which was 28 mm in length and weighed 1.3 g, the electrical energy generated by the prototype exceeded the energy consumed for electrical stimulation, with the net power being 111 µW. It was demonstrated that the proposed implantable power generation system has the potential to replace implantable batteries for active implantable medical devices.

Optimizing pacemaker longevity with pacing mode and settings programming: results from a pacemaker multicenter registry

BACKGROUND

This study aimed to describe the influence on dual-chamber devices' expected longevity of devices' settings.

METHODS

Data from patients implanted with dual chamber devices (Symphony™, SORIN CRM SAS, Clamart, France) from 2003 to 2006 were collected in registries. Programmer files were retrieved: device-estimated longevity, assessed through algorithm prediction, was analyzed according to device settings.

RESULTS

One thousand sixty-eight recipients of dual chamber pacemaker in sinus rhythm (75.3±11.1 years, 54.5% male, ventricular block 30%, brady-tachy syndrome 21%, and sinus node dysfunction 49%) were followed up to 14.2±12.1 months (ranging from first quartile Q1: 2.9 months to fourth quartile Q4: 49.3 months) after implantation. DDD with automatic mode conversion and minimized ventricular pacing (SafeR) modes were programmed in 34.3%, 2.9%, and 62.8% of the patients, respectively. The mean total longevity estimated by the device was 134.1±31.5 months (11.2±2.6 years). Significant increase in longevity was observed in devices undergoing at least one reprogramming (134.4±31.4 months) versus device presenting no reprogramming (103.4±32.3 months, P=0.0005). The parameters associated with the major increase in mean longevity were the mode (mean longevity increase of +23.9 months in SafeR as compared to DDD mode, P<0.0001) and the atrial (A) and ventricular (V) amplitudes (mean longevity increase of +29.6 and +26.9 months for a decrease of less than 1V in A and V outputs respectively, P<0.0001).

CONCLUSION

This study provides information on dual chamber pacemakers' longevity and highlights the impact of devices' reprogramming on expected longevities.

In vivo demonstration of a self-sustaining, implantable, stimulated-muscle-powered piezoelectric generator prototype

An implantable, stimulated-muscle-powered piezoelectric active energy harvesting generator was previously designed to exploit the fact that the mechanical output power of muscle is substantially greater than the electrical power necessary to stimulate the muscle's motor nerve. We reduced to practice the concept by building a prototype generator and stimulator. We demonstrated its feasibility in vivo, using rabbit quadriceps to drive the generator. The generated power was sufficient for self-sustaining operation of the stimulator and additional harnessed power was dissipated through a load resistor. The prototype generator was developed and the power generating capabilities were tested with a mechanical muscle analog. In vivo generated power matched the mechanical muscle analog, verifying its usefulness as a test-bed for generator development. Generator output power was dependent on the muscle stimulation parameters. Simulations and in vivo testing demonstrated that for a fixed number of stimuli/minute, two stimuli applied at a high frequency generated greater power than single stimuli or tetanic contractions. Larger muscles and circuitry improvements are expected to increase available power. An implanted, self-replenishing power source has the potential to augment implanted battery or transcutaneously powered electronic medical devices.

Pacemaker longevity: the world's longest-lasting VVI pacemaker

OBJECTIVE

To describe VVI-pacemaker longevity by model type at our institution and report on a long-lasting model and the longest-lasting pacemaker to be described in the literature.

BACKGROUND

Cardiac pacemakers are becoming increasingly common in the United States. Presently their batteries are expected to last up to 12 years. Pacemaker generator change is associated with increased cost to the health care system and is inconvenient for patients.

METHODS

After identifying a group of very long-lasting CPI Microlith 605 VVI pulse generators, we reviewed records on all patients who had either Guidant or Medtronic pulse generator explantation at our institution over a 10-year period. Average longevities were calculated for all VVI pacemakers, four common VVI models, and the CPI Microlith 605.

RESULTS

A total of 105 VVI-programmed pacemakers were identified. Their average longevity was 7.2 years. The two most common Medtronic VVI-programmed pacemakers explanted were the Thera (7.1 years) and Kappa (7.3 years). The two most common Guidant/CPI models were the Vigor (4.2 years) and Discovery (5.7 years). The CPI Microlith 605 (19.2 years) lasted more than 26 years in one patient before being explanted.

CONCLUSION

At a time when pacemakers are being used more frequently, pacemaker longevity may decrease as a result of the use of dual-chamber pacing systems. In our study, the CPI Microlith 605 had an average longevity more than twice that of all other VVI pacemakers. We also report on a pulse generator that lasted 26.3 years.

Long-term experience with AutoCapture-controlled epicardial pacing in children

AIMS

To examine the feasibility and safety of AutoCapture (AC)-controlled pacing with epicardial leads in children, and study the effects on device longevity.

METHODS

A total of 62 children were prospectively enrolled. Pre-discharge testing precluded AC function in six children. In 56 (90%) children, devices with AC-controlled pacing were followed up to 9years. Calculated battery life in AC-controlled pacing was compared with theoretical calculations, using a two-fold stimulation output of measured thresholds.

RESULTS

In 53 of 56 children, no differences were observed for evoked response signals (13.3 vs. 11.5mV, P = 0.20) or lead polarization safety margins (5.5 vs. 4.1, P = 0.25) at 6-month and 4-year follow-up. A crossover to conventional pacing was required in 3 of 56 children. AC-controlled pacing prolonged the calculated battery life up to 15% for the identity and integrity devices with 0.95A h capacity, compared with theoretical conventional settings (P = 0.008). In patients with ventricular pacing thresholds >1.5V at 0.5ms, battery life was increased by 30% compared with theoretical conventional settings (P < 0.001).

CONCLUSION

AC-controlled pacing with epicardial leads is feasible and safe in children during long-term follow-up. An adequate lead polarization safety margin persists in most patients. Calculated battery life was prolonged up to 15% with AC-controlled pacing. Patients with high or fluctuating pacing thresholds benefit the most.

Reducing Ventricular Pacing in Sinus Node Dysfunction DDIR versus DDDR

BACKGROUND

The use of DDIR mode has been limited since the advent of mode switch in the DDDR mode. In patients with AV block, DDDR is necessary to maintain AV synchrony. However, DDIR mode may still be beneficial for patients with intact AV conduction. The aim of this study was to compare the incidence of ventricular pacing and atrial tachyarrhythmia in DDIR and DDDR with mode switch in a randomized, single-blind, crossover study, and discuss the utility of both modes.

METHODS AND RESULTS

Twenty-four patients (8 males) with bradycardia-tachycardia syndrome and no signs of AV block (mean age 70.1 +/- -9.1 years) were enrolled and randomized to DDIR or DDDR modes with the leads placed at the right atrial appendage and right ventricular apex. After 12 weeks, patients were switched to the opposite mode. During the study period, atrial high rate episodes and other pacemaker diagnostic data were collected. Significantly less ventricular pacing was observed in DDIR mode (DDIR versus DDDR; 48.9%, 76.5%, P = 0.0002) and atrial high rate episodes were significantly lower in DDIR mode (DDIR versus DDDR; 1.32, 1.85 per day, P < 0.05).

CONCLUSION

In patients with sinus node dysfunction and intact AV conduction, DDIR mode may have important implications for simplifying device programming, device longevity, and to avoid atrial tachyarrhythmia.

Cost-effectiveness of dual-chamber pacing compared with ventricular pacing for sinus node dysfunction

BACKGROUND

Compared with single-chamber ventricular pacing, dual-chamber pacing can reduce adverse events and, as a result, improve quality of life in patients paced for sick sinus syndrome. It is not clear, however, how these benefits compare with the increased cost of dual-chamber pacemakers.

METHODS AND RESULTS

We used 4-year data from a 2010-patient, randomized trial to estimate the incremental cost-effectiveness of dual-chamber pacing compared with ventricular pacing and then projected these findings over the patients' lifetimes by using a Markov model that was calibrated to the first 5 years of in-trial data. To assess the stability of the findings, we performed 1000 bootstrap analyses and multiple sensitivity analyses. During the first 4 years of the trial, dual-chamber pacemakers increased quality-adjusted life expectancy by 0.013 year per subject at an incremental cost-effectiveness ratio of 53,000 dollars per quality-adjusted year of life gained. Over a lifetime, dual-chamber pacing was projected to increase quality-adjusted life expectancy by 0.14 year with an incremental cost-effectiveness ratio of approximately 6800 dollars per quality-adjusted year of life gained. In bootstrap analyses, dual-chamber pacing was cost-effective in 91.9% of simulations at a threshold of 50,000 dollars per quality-adjusted year of life and in 93.2% of simulations at a threshold of 100,000 dollars. Its cost-effectiveness ratio was also below this threshold in numerous sensitivity analyses that varied key estimates.

CONCLUSIONS

For patients with sick sinus syndrome requiring pacing, dual-chamber pacing increases quality-adjusted life expectancy at a cost that is generally considered acceptable.

Pacemakers and Implantable Cardioverter Defibrillators:. Device Longevity Is More Important Than Smaller Size: The Patient's Viewpoint

The size of pacemakers and implantable cardioverter defibrillators (ICDs) has been diminishing progressively. If two devices are otherwise identical in components, features and technology, the one with a larger battery should have a longer service life. Therefore, patients who receive smaller devices may require more frequent surgery to replace the devices. It is uncertain whether this tradeoff for smaller size is desired by patients. We surveyed 156 patients to determine whether patients prefer a larger, longer-lasting device, or a smaller device that is less noticeable but requires more frequent surgery. The effects of subgroups were evaluated; these included body habitus, age, gender, and patients seen at time of pulse generator replacement (PGR), initial implant, or follow-up. Among 156 patients surveyed, 151 expressed a preference. Of these, 90.1% preferred the larger device and 9.9% the smaller device (P <0.0001). Among thin patients, 79.5% preferred a larger device. Ninety percent of males and 89.2% of females selected the larger device. Among younger patients (< or =72 years), 89.6% preferred the larger device, as did 90.5% of older patients (>72 years). Of patients undergoing PGR or initial implants, 95% favored the larger device, as did 86% of patients presenting for follow-up. The vast majority of patients prefer a larger device to reduce the number of potential replacement operations. This preference crosses the spectrum of those with a previously implanted device, those undergoing initial implants, those returning for routine follow-up, and patients of various ages, gender, and habitus.

The Nature and Frequency of Postimplant Surgical Interventions:

The purpose of this retrospective study was to investigate the nature and frequency of surgical reinterventions after primary pacemaker implantation in patients who survived at least 20-30 years. Eighty-five such patients were identified, 32 of whom had radioisotopic (nuclear) implants, and 53 lithium battery powered lithium units. Excluding reoperations within the first 3 months, patients with nuclear implants experienced about two reoperations in 25 years, while those with lithium experienced one every 8 years. The most frequent reasons for surgery were pulse generator replacements, lead revisions, and mode changes, particularly in the nuclear group. There were no premature device failures. This study allows us to make reasonable predictions to patients about the experience a pacemaker implantation, and reassures us about the reliability of the devices that were implanted in the past.

Effect of modern pacing algorithms on generator longevity: a predictive analysis

Pulse generator (PG) longevity is of major importance to the quality of care of pacemaker patients. A series of automatic algorithms affect PG longevity. This study investigated the individual and combined effects of three algorithms incorporated in the Medtronic Kappa 700 pacemaker series: Capture Management periodically measures the stimulation threshold and adjusts the PG output, Sinus Preference allows the sinus rate to prevail in a specified range below the sensor rate, and Search AV allows an extension of the AV interval if spontaneous conduction is observed. The effects of Capture Management, Sinus Preference, and Search AV on device longevity were studied in 21 consecutive patients treated in the VDD and DDDR modes. Patients were followed for 1 year. The data were analyzed using an equation provided by the manufacturer. Capture Management was activated in 20 patients. For 11 PGs at the basic settings, longevity was extended by 5.2%, whereas reprogrammed PGs had no gain. Sinus Preference was active in four DDDR patients, who gained 12.0 +/- 5.3%atrial sensing from it, with a resultant longevity gain of1.4 +/- 0.45 months(NS). Search AV was active in 19 patients and 8 responders gained 7.8 +/- 4.4 months PG longevity. The overall longevity in this study was 106.3 +/- 8.4 months with all features as programmed, whereas the longevity without Capture Management and Search AV algorithms would be 98.2 +/- 4.9 months, saving 8.1 +/- 5.8 months(range 0-18) of battery life. Thus, two algorithms: Capture Management and Search AV, have clinical relevance in the extension of PG longevity.