Pacemakers longevity

Schuchert A and Kuck KH Influence of internal current and pacing current on pacemaker longevity. PACE 1994 17 13-16. 

Furman S, Garvey J, Hurzeler P. Pulse duration variation and electrode size as factors in pacemaker longevity. J Thorac Cardiovasc Surg 1975 69(3) 382-389. 

Pacemaker and defibrillator systems consist of two implanted and one external component the generator, cardiac leads, and programmer, respectively (Morley-Davies and Cobbe, 1997). Although the clinical functions of pacemakers and defibrillators differ, the desired component characteristics are similar and include low complication rates coupled with small size, durabiliiy, and longevity. 

In most modem pacemakers the logic functions are controlled by microprocessors. A pacemaker microprocessor is very similar to the central processing unit (CPU) in a desktop computer. A pacemaker microprocessor operate with currents mil-Uons of times less than low-power microprocessors in today s laptop computers. This low-power operation is necessary in order to achieve overall size and longevity and can limit its processing power. The pacemaker CPU is generally custontized and integrated with other components such as memory on one IC. 

If the procedure is to proceed in a smooth and expeditious fashion, careful preoperative planning is essential. The first such decision is whether the patient requires a single-chamber or dual-chamber pacemaker. As a rule, if the patient has intact atrial function, every effort is made to preserve atrial and ventricular relationships. Single-chamber ventricular pacing is usually reserved for the patient with chronic atrial fibrillation or atrial paralysis. A device is selected with acceptable size, longevity, and progranunability. If the heart is chronotropically incompetent, a device that offers some form of rate adaptation... 

The growing availability of AutoCapture capabilities, first introduced in Europe by St. Jude Medical in their Microny family of single-chamber rate-modulated pacemakers has been expanded to the ventricular channel in the Affinity family of dual-chamber pacemakers (50-52). Similar but not identical algorithms have now been introduced by other manufacturers thus reducing the need for periodic capture threshold assessments. However, it does not totally eliminate the need to consider the combined concerns of patient safety and device longevity and periodically assess the event counter diagnostics that accompany this feature. While AutoCapture will protect the patient to... 

Fig. 19.19 Pacemaker output settings for lowest current drain and maximum longevity induction of an endless loop tachycardia during an atrial capture threshold test in a patient with a Pacesetter Affinity DR pacing system. The automatic PMT detection and termination algorithm recognized the tachycardia and promptly terminated it. Meanwhile, the recording provided details as to the tachycardia interval and the retrograde conduction interval providing guidance as to programming the PVARP.

Marco D, Pacemaker output settings for lowest current drain and maximum longevity, Reblampa 1995 8 159-162. 

Crossley GH, Gayle D, Simmons TW, et al., Reprogramming pacemakers enhances longevity and is cost-effective. Circulation 1996 94 (Suppl II) 245-247. 

Separate pacemaker and ICD devices in the same patient are becoming increasingly rare. This is likely so because contemporary ICDs have generous bradycardia pacing functions, and improved battery longevity. 

Battery weight 12.5—15.5 g depending on the pacemaker manufacturer in addition, variation in battery weight is strictly dependent on the battery s longevity requirements and current drain capabilities. 

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. 

Chemical reaction expressions are derived wherever required for the benefits of readers and to examine the harmful battery by-products, if any. Li-ion rechargeable batteries capable of supplying ultra-low current levels in a microampere range from 10 to 25 mA best suited for implantable pacemakers are described with an emphasis on longevity, reliability, safety, and minimum size and weight. 

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. 

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