Cardiac Pacemaker System Presented by Wong Shin KEU

Cardiac Pacemaker System Presented by: Wong Shin (KEU 98038) Mc. Cartney Dandot (KEU 97010)

Scope of presentation • Introduction • A prelude: normal heart activity • Pacemakers: its past history – Conception of idea – Invention process – Clinical prototyping • Pacemakers: Current development • Pacemakers: its future trend • Comment and conclusion

Introduction • A pacemaker system is a device capable of generating artificial pacing impulses and delivering them to the heart. • It consists of a pulse generator and appropriate electrodes. • In the past few years electronic pacemaker systems have become extremely important in saving and sustaining the lives of cardiac patients whose normal pacing function of the heart have been impaired.

Normal heart activity

Why need the pacemakers? • Sometimes a heart's natural rhythm is interrupted or becomes irregular- bradycardia – The heart's natural pacemaker sends out electrical impulses too slowly due to a diseased SA node. – Or, the electrical impulses may be blocked along the pathway through the heart, -"heart block. " – Symptoms: dizziness, extreme fatigue, shortness of breath, or fainting spells. • A pacemaker stimulates the heart muscle with precisely timed discharges of electricity that cause the heart to beat in a manner very similar to a naturally occurring heart rhythm.

Pacemakers: its past history Conception of idea • Cloroform was popular in the late 1980 s, but when it was used, occasional respiratory and cardiac arrest occurred, as an occasional complication of cloroform anesthesia • To restart the heart, Green in the United Kingdom [1872] applied the output of a 300 V battery using hand-held electrodes applied to the base of the neck and the lower left chest. • Interestingly, the electrode applied to the lower left chest stimulated the ventricles. The other electrode applied to the base of the neck delivered current to the phrenic nerve and twitched the diaphragm, causing a brisk inspiratory motion.

Invention process • In 1882, Ziemssen in Germany applied cardiac pacing to a 42 -year-old woman who had a large defect in the anterior left chest wall following resection of an enchondroma. • The heart was only covered by skin, on which Ziemssen placed electrodes. • Using induction-coil shocks, he paced the heart with a stimulus frequency higher than that of the normal heart rate.

Clinical prototyping • Dr. Rune Elmqvist designed the world's first implantable pacemaker. It included a pulse generator delivering about two volts with an impulse period of two milliseconds. The original transistors showed large leakage currents and were found not suitable. • Problems of the early pacemakers: breakage of electrode wires, short battery life, the need for surgery for pacemaker and lead implantation • Chardack [1961] described a durable electrode wire made from the alloy that is used in the escapement spring of watches. It was sutured to the epicardium, and a thoracotomy was required.

• Within a year, Lillehei et al. [1960] reported the use of right ventricular catheter electrodes with an external pacemaker to pace 66 patients. The pacemaker was built by Earl Bakken, a biomedical engineer, the founder of Medtronic Inc. in 1949, which soon became the pioneer pacemaker company. • The pacemaker manufactured is called the Greatbatch-Chardack pacemaker. It consisted of a transistor oscillator and an amplifier energized by 10 mercury-zinc cells. The 10 cells and electronic circuitry were potted in epoxy and covered by a double shell of Silastic. The electrode used was about the size of a postage stamp

Earl's first wearable, battery-powered, transistorized cardiac pacemaker

Invention process (cont. ) From Earl E. Bakken's Book "One Man's Full life" "Back at the garage, I dug out a back issue of Popular Electronics magazine in which I recalled seeing a circuit for an electronic, transistorized metronome. The circuit transmitted clicks through a loudspeaker; the rate of the clicks could be adjusted to fit the music. I simply modified that circuit and placed it, without the loudspeaker, in a four-inch-square, inch-and-thick metal box with terminals and switches on the outside - and that, as they say, was that. "

Schematic drawing of a pacemaker The pulse generator houses the battery and the circuitry, which generates the stimulus and senses electrical activity. The lead is an insulated wire that carries the stimulus from the generator to the heart and relays intrinsic cardiac signals back to the generator

A closer look at the pacemaker The programmer is a telemetry device used to provide two-way communication between the generator and the clinician. It can alter therapy delivered by the pacemaker and retrieve diagnostic data that are essential for optimally titrating that therapy.

Pacemaker today

Pacemaker: Current Development • Comprise of 3 distinct components: • Pulse generator • Lead • Programmer • Come in different shapes and sizes • Small and lightweight (~22 -50 gms) • Depending upon patient’s heart condition, physician will prescribe the number of chambers to be paced and type of pacing

Number of Chambers • A single-chamber pacemaker paces either the right atrium or the right ventricle, with one lead. Most common is the right ventricle. • A dual-chamber pacemaker paces both the right atrium and right ventricle of the heart with two pacing leads. Most common type of pacemaker implanted today.

Single-chamber pacemaker A single-chamber pacemaker placed in the right ventricle of the heart • Correct a slow or unsteady heartbeat, resulted from “heart block”. • Pacemaker lead will ensure that the heart's ventricles contract rhythmically and fully.

Single-chamber pacemaker model available from Medtronic • Rate responsive • It has one or two sensors that detect changes in the heart rate needs. • It then adjust the heart rate accordingly Medtronic Kappa SR, Series 400

Dual-chamber pacemaker • • • A dual-chamber pacemaker with two pacing leads Senses both atrial and ventricular activity to see if pacing is needed When pacing does occur, the contraction of the atria is followed closely by a contraction in the ventricles Resulting in timing that mimics the heart's natural way of working.

Dual–chamber pacemaker model available from Medtronic • Rate responsive • It has one or two sensors that detect changes in the heart rate needs. • It then adjust the heart rate accordingly Medtronic Kappa DR, Series 400

Rate-Responsive Pacemaker • A rate-responsive pacemaker uses a or a combination of special sensor(s): – activity sensor – minute ventilation sensor • that recognizes body changes and helps the heartbeat speed up or slow down to meet patient body's changing needs for blood. • It mimics patient heart's natural function. • The physician has many options in programming the pacemaker to respond to the patient normal activities as illustrated in the next slide.

n n n A normal heart rhythm slows down or speeds up many times during the day. The heart beats slower while resting or sleeping. Exercise or emotional excitement make heart beat faster because, in an excited state, the body requires greater amounts of blood to be circulated.

Successes of the Pacemaker • Successfully implanted, since the late 1950 s. • More than 2 million people have been benefited • The development of new pacing technologies since 1985 has opened the door for significant improvements in pacemaker wearers' quality of life • by permitting greater tolerance for exercise and participation in new activities.

Case study on the success of Medtronic Kappa 400 Series • One year after receiving a single sensor (minute ventilation), single chamber pacemaker, a 69 -year-old patient was still having symptoms when exercising • After implanting the Medtronic Kappa 400 Series pacemaker, the patient was able to resume his previous exercise regimen of rock climbing and exercising at a gym. • The integrated dual sensors (activity and minute ventilation) of the Medtronic Kappa 400 Series pacemakers provide heart rate support proportional to a patient's metabolic demands.

Pacemakers: its future trend • In future generations, – developments in the field of microprocessor technology will most likely lead to greater flexibility in the self-adjustment of rate, output, and the overall sensitivity of pacemakers. – The continued innovation of programmability and telemetry will increase the diagnostic capabilities of pacemakers. – Systems are being developed which can facilitate storing of patient details and which can diagnose rhythm disturbances using sophisticated algorithms. – Sensors will be combined with electrogram analysis to differentiate between physiological and pathological alterations in hemodynamics so that appropriate adjustments can be initiated.

Pacemakers: its future trend (cont. ) • Pacemaker technology that is self-adjusting will evolve that can differentiate arrhythmias and initiate the appropriate pacing modality. • Progress in battery technology will reduce generator size further without effects on longevity. • Generator microprocessors will permit more flexible programming of algorithms that will satisfy the patient's changing requirements. • A pacemaker may be reprogrammed or experience a change in the sensing or pacing thresholds after a shock from a defibrillator. • In future generations, it is important that the pacemaker be able to protect itself from excessive energy and shocks caused by a defibrillator.

Comment and conclusion • A pacemaker system is a device that sends periodic impulses to the heart to restore the rhythm of the heart. • Early devices provided only single-chamber, asynchronous, nonprogrammable pacing coupled with questionable reliability and longevity. • Today, advanced electronics afford dualchamber multiprogrammability, diagnostic functions, rate response, data collection, and exceptional reliability, and lithium-iodine power sources extend longevity to upward of 10 years.

Comment and conclusion (cont. ) • Such features have evidently improved the management of patients with cardiac problems such as bradycardia. • The new diagnostic function can aid clinicians to diagnose and keep track with patient’s development. • Continual advances in a number of clinical, scientific, and engineering disciplines have so expanded the use of pacing that it now provides cost-effective benefits to an estimated 350, 000 patients worldwide each year.

That’s all for our presentation… Thank you very much for your attention!