Implantable cardiac pacemaker batteries

Lithium iodide is the electrolyte in a number of specialist batteries, especially in implanted cardiac pacemakers. In this battery the anode is made of lithium metal. A conducting polymer of iodine and poly-2-vinyl pyridine (P2VP) is employed as cathode because iodine itself is not a good enough electronic conductor (Fig. 2.3a). The cell is fabricated by placing the Li anode in contact with the polyvinyl pyridine-iodine polymer. The lithium, being a reactive metal, immediately combines with the iodine in the polymer to form a thin layer of lithium iodide, Lil, which acts as the electrolyte ... 

Silver, copper and other oxosalts have been extensively studied as cathodes in laboratory cells commercial power sources, principally for pacemakers, using silver chromate were manufactured until the 1980s, and silver vanadate or silver vanadium oxide (Ag2V4On), first reported by workers at Wilson Greatbatch Ltd, is currently used as cathode in implantable cardiac defibrillator batteries. 

Polymer electrolyte batteries have been used in implanted cardiac pacemakers since 1972. The system used is lithium/iodine-polyvinylpyridine. Although the conductivity of the Li ions in Li2l is poor, the current requirements are very small, and the major consideration is the storage of a high energy density of nearly 1 Whcm . ... 

Secondary, or rechargeable, cells have been used in medical devices for some time. One of the first batteries to be used for implantable cardiac pacemakers was a custom rechargeable nickel-cadmium battery [6]. Systems to recharge the battery transcuta-neously using inductive methods were developed starting in the late 1950s [42]. 

Greatbatch W, Lee JH, Mathias W, Eldiidge M, Moser JR, Schneider AA (1971) The solid-state lithium battery a new improved chemical power source for implantable cardiac pacemakers. IEEE Trans BioMed Eng BME 18 317-324... 

The first lithium/iodine cardiac pacemaker battery was implanted in 1972. This type of battery proved to be very successful in this field and for other applications, too. The special features of this solid state battery are explained with its technique, which is limited with its extremely high energy density and reliability, especially for low rate applications. This technique is based firstly on the electrode couple of lithium and iodine with its high energy content - the OCV of the lithium/iodine cell is 2.80 V -and secondly on the favorable fact that the product of the cell reaction, the lithium iodide (LiJ), forms very tight and continuous layers between the active material of the electrodes, which are acceptable ionic conductors with negligible electronic... 

Most of the implantable cardiac pacemakers need to be replaced because of the battery exhaustion within 5-8 years. The longevity of the IMDs is determined by the battery life. When the service life of the battery ends, it needs to be replaced, causing the patient to undergo painful surgery and incur enormous expenses. In contrast, the main advantage of fuel cells for IMD is its theoretical potential to function as long as the individual is alive. The devices can use substrates that already exist in the body— no artificial fuel and oxidants are required. 

The high reliability and the complete absence of faults such as electrolyte leakage or gas generation make the lithium-iodine solid state battery a particularly suitable device for powering implanted electronic devices, and it is now widely used in the cardiac pacemaker industry. The design and construction of Medtronic Inc, pacemaker batteries are shown in Fig. 9.12. A typical unit, such as the Enertec Alpha 33 , has dimensions of 33.4 mm X 27.4 mm X 7.9 mm, giving a total volume of 6.0 cm3 and a mass of 22 g. The cell has a completely welded construction and uses a specialized... 

Lithium batteries are used in many portable consumer electronic devices and are also widely used in industry. The most common type of lithium cell used in consumer applications comprises metallic lithium as the anode and manganese dioxide as the cathode, with a Li salt such as Li perchlorate or Li tetrafluoroborate dissolved in an organic solvent. Lithium batteries find application in many long-life, critical devices such as cardiac pacemakers and other implantable electronic medical devices. These devices use special lithium-iodide batteries designed to last 15 years or more. Lithium batteries can be used in place of ordinary alkaline cells in many devices such as clocks and cameras. Although they are more expensive, lithium cells provide a much longer life, and thereby minimize battery replacement. 

Increasingly, biopotentials have to be measured within implanted devices and need to be transmitted to an external monitor or controller. Such applications include cardiac pacemakers transmitting the intracardiac ECG and functional electrical stimulation where, for example, action potentials measured at one eyelid serve to stimulate the other lid to restore the physiological function of a damaged lid at least to some degree. In these applications, the power consumption of the implanted biopotential amplifier hmits the life span of the implanted device. The usual solution to this problem is an inductive transmission of power into the implanted device that serves to recharge an implanted battery. In applications where the size of the implant is of concern, it is desirable to eliminate the need for the battery and the related circuitry by using a quasi-passive biopotential amplifier, that is, an amplifier that does not need a power supply. 

Implantable stimulation systems use an encapsulated pulse generator that is surgically implanted and has subcutaneous leads that terminate at electrodes on or near the desired nerves. In low power consumption applications such as the cardiac pacemaker, a primary battery power source is included in the pulse generator case. When the battery is close to depletion, the pulse generator has to be surgically... 

In this entry are discussed a few of the specialized batteries for medical devices that are portable or wearable (carried with the patient, like hearing aids), or implantable (surgically placed inside the body as with neurostimulation pain management devices). There is a focus on the batteries designed for a few of the more common applications - implantable cardiac rhythm management (cardiac pacemakers and defibrillators), pain management, and hearing loss devices. 

Carbon monofluoride (CFx) is one such fluoride compound that today is used as a positive electrode material in Li batteries for a number of different applications. For example, they are used in certain types of heart failure devices - implantable cardiac resynchronization therapy pacemakers (CRT-P). CRT-P devices can pace the right atrium and right ventricle, but they are also capable of pacing the left ventricle. Pacing three chambers requires more power than a cell can deliver, so a different battery type is needed. Li/CFx cells were developed in response to the increased power required by CRT-P devices. Vagal nerve stimulator devices also use a Li/CFx cells. 

Cardiac pacemakers are generally employed when the cardiac rhythm is either abnormal or too slow. To rectify this problem, doctors prescribe implanted pacemakers that detect the slow heart rate and send impulses to stimulate the muscle using microelectronic circuits. The life of these devices developed before 1973 and incorporating zinc-mercuric-oxide (Zn-HgO) batteries was only between 12 and 18 months. When Li-l2 batteries became available around 1975, the battery life was extended to more than 10 years. The life of devices with batteries developed after 2008 could be more than 15 years. 

According to heart specialists, four distinct types of medical devices can be used to treat cardiac diseases, namely pacemakers, cardioverters, defibrillators, and left-ventricular assist devices. In addition, the total artificial or mechanical heart needs to be powered by batteries with an emphasis on reliability, safety, and OCV with no electrical surges and voltage fluctuations. Generally, cardiac pacemakers are prescribed by heart specialists when the cardiac rhythm is too slow or when the patient has an abnormal heart beat. This device is implanted in the patient s chest. The implanted pacemaker detects the slow heart rate and sends electrical impulses to stimulate the heart muscle. An electrical signal from the muscle is fed back to the device to make appropriate corrections in the stimulation parameters, which will normalize the heart rate within a hundred microseconds or so. 

Since 1972, Catalyst Research Corporation has been the supplier of lithium-iodine batteries for cardiac pacemakers and other medical implantable devices and, more recently, for other applications of these batteries. 

From the first pacemaker implant in 1958 by Dr Ake Senning surgeon at the Karolinska Hospital in Stockholm, numerous engineering developments have faced challenges in battery power. In 1972, a primary lithium-iodine battery replacing the mercury-zinc cells greatly extended the cardiac pacemaker life (about 10 years). More details on the history of this battery can be found in ref. 

The semiconductive properties and tunnel structure of sulfide and transition-metal oxides led to the use of these materials in lithium power sources (Table 2.5). Several lithium-based chemistries were successfully applied to replace the prior system Zn/AgO and later the lithium-iodine batteries in implantable medical devices [59-61]. For example, Li//CuO, Li//V205, Li//CF and more recently Li// Ag2V40ii couples have been adopted to power cardiac pacemakers requiring less that 200 pW [62,63]. The lithium/carbon monofluoride (Li//CFJ primary cells are very attractive in several applications because of the double energy density with respect to the state-of-the-art LiZ/MnOa primary batteries (theoretically 2203 against 847 Wh kg ). 

Medical Device Batteries describes wearable and implantable medical devices powered by batteries. Devices include those that are used for cardiac rhythm management (pacemakers, defibrillators, and heart failure devices), hearing loss, bone growth and fusirm, drug delivery for therapy or pain relief, nerve stimulation for pain management, urinary incompetence and nervous system disorders, vision, diagnostic measurements and monitoring, and mechanical heart pumps. 

Takeuchi ES, Leising RA, Spillman DM, Rubino R, Gan H, Takeuchi KJ, Marschilok AC (2004) Lithium batteries for medical applications, hi Nazii G-A, Pistoia G (eds) Lithium batteries science and technology. BQuwer, Boston, pp 686-700 Untereker DF, Crespi AM, Rorvick A, Schmidt CL, Skarstad PM (2007) Power systems for implantable pacemakers, cardioverters, and defibrillators. In Ellenbogtai KA, Kay GN, Lau C-P, Wilkoff BL (eds) Clinical cardiac pacing and defibrillation, 3rd edn. Saunders, Philadelphia, pp 235-259... 

Various batteries are used by implantable devices for the treatment of cardiac diseases. Some of these devices have been found to be ideal in terms of reliability and longevity, some have been found to be marginal in performance, and only few have been found to be suitable for pacemaker applications. The batteries selected for the treatment ofvarious cardiac diseases include Li-l2, LiAgVO,2, LiMn02, Li-ion, and LiCF,j. The performance of the batteries used in pacemakers is somewhat affected by such factors as body temperature, dissolved blood oxygen, physical exertion, and body movements. 

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