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ARTIFICIAL PACEMAKER

What is a pacemaker?

Artificial pacemakers are a two-part electrical system that includes a pulse generator (pacemaker) and one or two leads which deliver impulses to the heart. The leads also carry signals back from the heart.

By "reading" these signals, the pulse generator is able to monitor the heart's activity and respond appropriately.

A pacemaker helps to pace the heart when the natural rate is too slow to pump enough blood to the body (bradycardia).

Pacing Systems

Pulse generator

Sensing and Pacing lead

Pulse generator

Main elements: Power source – provide the energy

required for the operation of the pacemaker

Memory (RAM/ROM) to store data for diagnostic purposes

Antenna. Monitors relevant heart data and sends it, for example, to doctor

Microprocessor – controls all operations

Pulse generator is responsible for generating the pulse at the proper time based on events

sensed

Pacing Lead

The generator is connected to heart through the tiny wires called leads.

Leads deliver the pulse to its destination in the heart, sense and carry back information to the pulse generator.

Each lead has an electrode on its tip. That tip actually burrows into heart wall

Connector

Lead BodyActive Fixation

Mechanism

TipElectrode

Fixation Mechanisms

Good contact with the heart wall. Achieve best results in pulse pacing of the heart

Electrode

Effective interface between two systems, physiology and electronics, can be done with electrode

Material used for electrode tips is titanium Electrode housing is made from silicone rubbers Steroids needed to prevent inflammation process

Inflammation – process when, human body attempts to isolate a foreign object (est. põletik)

How a healthy heart works? The heart is a double pump that circulates blood

around the body. It has four chambers.

The upper right chamber (right atrium) and lower right chamber (right ventricle) take in deoxygenated blood from the body and send it to the lungs.

The upper left chamber (left atrium) and the lower left chamber (left ventricle) take in oxygenated blood from the lungs and send it around the body.

The ventricles do all the pumping.

The nervous system is responsible for the heart rate and coordinating the heart's pumping action

How does a pacemaker take over heart beat? The pacer's electrical pulses travel through leads to heart. The pulses are timed

to flow at regular intervals just like heart's natural electrical signals would.

Pacer has 2 functions: pacing and sensing (The third function is programming)

PacingPacer sends electrical signals to heart through pacing leads. Eachelectrical signal is called a pacing pulse. The pacing pulse begins heartbeat

SensingLeads send information about heart's electrical system back to the pacer.This allows the pacer not to interfere with a natural, healthy heart beat

Sensing Functions:- Level detection (amplitude)- Filter (band-pass filter)- Amplifier

Picture illustrates how pacemaker is connected to the heart and take control over

heart`s beat

Types of artificial cardiac pacemakers

Unipolar system

Single chamber - only one

chamber is regulated

Bipolar system

Dual chamber - two leads are used.

Implantation procedure The procedure is usually done

under local anaesthesia

The pulse generator is implanted under the skin

The leads are inserted using x-ray control, via a vein found in this area, and positioned in the appropriate right sided heart chamber

The leads are tested before the pulse generator is attached

Programming

Pacemakers have many programmable functions that can be done with a special programmer. Unfortunately there is no universal programmer and each manufacturer provides programmers that will work only with their pacemakers

Living with an artificial cardiac pacemaker A person with an artificial cardiac pacemaker can live a normal life and can still doeveryday activities.

Most pacemakers last longer than five years. Before the pacemakerfails, a battery depletion indicator suggests that the pacemaker should be replaced.This is again performed under local anaesthesia.

How does magnet application affect a pacemaker?

Magnet application disables the sensing amplifier, causing it to pace asynchronously.

It is recommended that patients with a pacemaker keep at least 15 cm away from possible sources of magnetic interference, e.g. mobile phones, magnetic pain therapy, stereo speakers

First pacemakers

The battery operated pacemaker by Lillehei and Bakken (1957)

First totally implantable pacemaker by Senning (1958)

A model of Albert Hyman’s Pacemaker (1931)

Referance

1. Berg, Linda R., Martin, Diana W., and Solomon, Eldra P. Biology: Sixth Edition. Ed. Nedah Rose. Thomson Learning Inc., 2002, pp. 923 – 928

2. Crane, Richard H. “Some of the Physics of Cardiac Pacemakers”. How Do Things Work (1983 – 1995). American Association of Physics Teachers., 1996, pp. 41 – 42.

3. Sutton, Caroline. “How Does an Artificial Pacemaker Help a Weak or Damaged Heart?”. How Do They Do That? : Wonders of the Modern World Explained. Ed. Duncan M. Anderson. Hiltown Press Inc., 1981, pp. 28 – 30

4. http://heartdisease.about.com/cs/arrhythmias/a/pacemakers.htm

5. http://www.tucsonheart.com/pacemaker_insertion.htm