The artificial heart

ENERGY TRANSFER FOR AN ARTIFICIAL

HEART

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An artificial heart is a prosthetic device that is implanted into the body to replace the biological heart.

Artificial heart  a pumping mechanism that duplicates the rate, output, and blood pressure of the natural heart; it may replace the function of a part or all of the heart.

INTRODUCTION

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ARTIFICIAL HEART

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THE HUMAN HEART

Heart has four chambers

Right chambers pump blood to lungs to receive oxygen

Left chambers pump oxygenated blood from lungs to rest of the body

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Cont…Right and left atria receive

bloodRight and left ventricles pump

bloodValves produce one-way blood

flow from atria ventricles arteries

Energy to pump blood comes from nutrients and oxygen in blood

The blood supply to the heart is provided by coronary arteries

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Why heart substitutes fail?

Immune response “rejects” transplant or side effects due to immune suppression

Formation of clotsDamage to red blood cellsLack of pulsatile blood flow

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ARTIFICIAL HEART HISTORY

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Artificial heart are of three types

VENTRICULAR ARTIFICIAL HEART

VENTRICULAR ASSIST DEVICE

TOTAL ARTIFICIAL HEART

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VENTRICULAR ARTIFICIAL HEART

Each pump is small enough to be

implanted into the void that was left

behind from the extraction.

The jarvik-7 design incorporates two heart pumps that are connected to a power console.

Both pumps receive power from a large

external console. The console pushes air through

the tubing.

Air enters inside the pump and is expelled

through a series of thin flexible diaphragms.

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VENTRICULAR ASSIST DEVICE

Michael has pioneered the development

of heart pumps since the early 1960s.

Ventricular assist device, invented by Dr Michael DeBakey was

implanted in 1966 at Methodist hospital in Texas.

In 1966, he performed the first successful

implantation of a ventricular assist device.

The patient's heart recovered while the VAD

took over its pumping chores.

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TOTAL ARTIFICIAL HEART

The AbioCor™ implantable replacement heart is the first completely self-contained

total artificial heart. It is the product of 30 years of research, development,

and testing conducted by ABIOMED, Inc. in order to extend and improve the lives of

patients who would otherwise die of heart failure.

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ENERGY TRANSFER Electrical circulatory assist devices use

brushless dc motor as its pump Electrical energy is transferred to these devices

transcutaneously using a transcutaneous transformer

Transcutaneous transformer has large leakage inductance which reduce its efficiency

Dc-dc converter employing secondary side resonance can be employed to alleviate this problem but the transfer gain of voltage varies widely with coupling coefficient

Converter employing compensation of leakage inductance on both sides of the transformer offers stable gain and high efficiency

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PROPOSED ENERGY TRANSFERENCE SCHEME

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Determination of Control region Gv curve is divided into 3 regions: low

frequency, middle frequency and high frequency regions

Region II provides maximum transfer gain but is very sensitive to changes in load and coupling coefficient, hence not used

Region I and III can control output voltage

Region III is desirable because the unity gain frequencies is much less sensitive than for region I

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System Design

Output requirements: V0 = 24V Iomax =2.0A I0min =0.5A Size, geometry and core material of the

transformer and range of air gap and misalignment between them are already defined

For transformer windings the same cores used in series converter are used

System Design Transformer Core: Ferroxcube Pot Core 6656 3C8 Ferrite OD=2.6in Thickness=1.1in Air gap=10-20mm Misalignment=0-10mm Region III of gain characteristics is selected

for control Low value of Q is selected to reduce

sensitivity if variation Compensating resonant frequency is chosen at

120kHz

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The AbioCor, along with other

components is surgically

implanted; it is designed to fit

within chest and abdomen.

ABIOCOR SYSTEM

• The AbioCor System consists of the following

implanted components: Replacement Heart Implanted TET Implanted Controller  Implanted Battery

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The thoracic unit weighs slightly more than two pounds (0.9 kg) and is

about the same size and shape of a natural heart.

It is made of titanium, and Angioflex, a polyurethane plastic. 

REPLACEMENT HEART

The thoracic unit is implanted in the chest, and connects

to the right and left atria, the aorta, and the pulmonary

artery.

The thoracic unit contains two hydraulic motors; one

keeps the blood pumping from each ventricle (blood

pump), and the other operates the motion of the four heart

valves.

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IMPLANTED TRANSCUTANEOUS ENERGY

TRANSMISSION (TET)

The implanted TET is an electric coil that provides

all of the AbioCor System’s internal devices with

electrical energy.

It is connected to the thoracic unit, the implanted

controller, and the implanted battery.

The implanted TET is located on the upper-left area

of the chest (opposite of the artificial heart).

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The job of the implanted controller is to

oversee the internal components of the

AbioCor System.

The implanted controller is also able to

manage the artificial heart’s cardiac output

rate to make sure that the artificial heat

generates the necessary blood flow. 

IMPLANTED CONTROLLERThe implanted controller is a small automatic computer located in

the abdomen of the patient’s body. 

It is secured in a titanium case and connects to all internal

components.

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The implanted battery is placed in the abdomen,

opposite from the implanted Controller.

It is implanted when the implanted controller and

the artificial heart are placed in the patient’s body.

The implanted battery is kept in a titanium case, it

receives energy from the external TET.

It is connected to all other internal components.

If the patient were to separate himself from the

external TET and battery pack (such as to take a

shower), the implanted battery would provide

energy for 30 - 40 minutes.

IMPLANTED BATTERY

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External Components:

TRANSCUTANEOUS ENERGY

TRANSMISSION (TET)

PATIENT-CARRIED

ELECTRONICS.

PCE BATTERY BAG

PCE BATTERIES

PCE CONTROL MODULE

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TRANSCUTANEOUS ENERGY TRANSMISSION (TET)

The external TET is placed directly over the location of the internal

TET to transfer energy through the skin.

If the patient is stationary and is near a power outlet, his source for

energy may be the console.If the patient is mobile and has

no intentions of remaining in

the same location for a long

period of time, he may use the

PCE as a power source.

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 PATIENT-CARRIED ELECTRONICS

The patient using the AbioCor System is not

forced to stay in bed hooked up to the

system’s console;

He is also given the option to move around

and not have to depend on a power outlet to

power the system’s components.

If the patient chooses to be mobile(movable)

he may use the Patient-Carried Electronics

(PCE) by plugging the external TET into the

PCE’s control module.

PCE BATTERY BAG

PCE Battery Bag weighs : 10 pounds.

Carried by using : An attached shoulder strap (Abiomed).

Inside of the bag contains : Four batteries, plastic cardholders.

Outside of the bag contains : PCE control module.

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PCE BATTERIESEach pair of PCE Batteries supplies the AbioCor’s internal system with

power for about one hour (Abiomed).

The battery bag can carry two pairs of PCE batteries.

The internal system may be supplied with power for about two hours .

Additionally, since the PCE batteries don’t last very long, they must be

changed several times a day so patient can take extra batteries if necessary.

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PCE CONTROL MODULE

The PCE control module is to be placed in one

of the pockets of the PCE battery bag.

It is connected to the batteries by a battery cable

and is also connected to the external TET.

 If a problem occurs within one of the internal

devices, the control module immediately notifies

the patient.

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To maintain operation, the AbioCor System

must first have a source of power depending

on whether or not the patient is mobile.

This power source will either be the console or

the PCE control module.

If the power source detects a problem, an

alarm light or an alarm sound notifies the

patient.

Otherwise, if no problems are detected the

AbioCor System follows a cyclic function and

continues to operate.

FUNCTION

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COST OF IMPLANTATION

Complete heart replacement device can

cost about $75,000.

Procedure expenses cost about

$175,000.

It is financed by the national heart

research fund.

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There are many obstacles to overcome before

any TAH is widely accepted.

The AbioCor System consists of a set of

internal components and external components.

The internal and external TETs work together

to convert this energy into usable energy for all

internal components.

CONCLUSION

• All of these provide power for the artificial

heart and components keep the artificial heart

pumping blood and keep sending that blood

throughout the patient’s body.

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“ARTIFICIAL HEART IS NOT A

BRIDGE TO

TRANSPLANTATION BUT A LIFE

EXTENDING DEVICE”

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REFERENCESAbiomed. Product details. http://www.abiomed.com/products/heart_replacement/product_details.cfm

Bonsor, Kevin. How Artificial Hearts Work. http://science.howstuffworks.com/artificial-heart.htm

Brain, Marshall. How Hydraulic Machines Work.http://science.howstuffworks.com/hydraulic.htm

Cho, B.H., Gyu Bum Joun. “An energy transmission system for an artificial heart using leakage inductance compensation of transcutaneous transformer”. IEEE. Nov. 1998http://ieeexplore.ieee.org/xpl/abs_free.jsp?arNumber=728328

Factmonster. heart, artificial. <http://www.factmonster.com/ce6/sci/A0823119.html>

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