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Wednesday, September 7, 2011

Abstract and full paper on ARTIFICIAL HEART


 ARTIFICIAL HEART

       INDEX


·                    Abstract

       ·        Introduction

 ·            Heart Anatomy and Disease

 ·            Effectiveness of Transplantation

 ·            Total Artificial Heart Development

 ·            A  Complete  Artificial  Implantable Heart

 ·            Design  of  the  Complete Artificial Implantable Heart

 ·            Conclusion

 ·            Bibliography


 ABSTRACT:

    Heart disease currently affects more than 100  million  people  around  the  World   Some  of  these  diagnosed  cases  are  so severe that patients  may not  survive  the wait  for  a  donor  heart.    Biomedical scientists and  engineers  have  developed devices  such  as  defibrillators, pacemakers, and artificial  hearts to keep patients  alive  until  a  donor  heart becomes  available.    Artificial   hearts prove  to  become  the  most  effective choice for severely ill patients.  In 1995, 2400  heart  transplants  were  performed while  4000  patients  awaited  donor hearts;  731  of  these  patients  died waiting.    With  the  number  of  patients suffering  from  severe  heart  disease increasing  and  the  number  of  donor hearts remaining constant, an immediate need  exists  for  the  advancement  of artificial hearts.  Artificial hearts provide a viable option for patient awaiting heart   transplantation. Future developments on artificial hearts have the   hope  of  eliminating  the  need  for the transplantation completely .


  INTRODUCTION:

                  Artificial  hearts  have  been around  since  the  early  1980s. TheJarvik-7   became   the   first   permanent artificial   heart   in   1982.  The   patient implanted with   the   device   lived   for   112 days on the artificial organ.  Patient   was   unable to leave his bed and was in severe pain until his death. Human life could be  prolonged  by  artificial  means,  but patients  still  had  to  suffer  after implantation. At this time, the risks, such as  sub-standard  quality  of  life, outweighed  future  benefits  of  artificial heart  technology  and  all  research  was put  off  until  positive  results  could  be expected.  After many technological Developments in materials science as well as pharmaceuticals, artificial heart technology is once more in the spotlight. The  Complete  Artificial  Implantable Heart  and  the  Ventricular  assist  device provide  a  mobile  option  for  severely  ill cardiac patients.

2. Heart Anatomy and Disease
                            
                                   To  completely  understand  the design  development  of  the  device,  it  is imperative  to  know  the  functions  and diseases of  the  human  heart.   The heart is the most important organ in the human body.    Even  if  a  patient  is  considered brain dead, the patient is still considered alive  until  the  heart  stops  beating. Though it serves such an essential role the mechanisms behind the human heart are relatively   simple.    The heart is pump that works based on positive displacement.  Positive  displacement refers  to  a  change  in  volume  within  a chamber  due  to  the  movement  of  fluid across its boundaries.  From this volume change,  pressure  differences  arise  that drive  the  blood  pumping  process.  The heart  has  four  chambers.    These chambers or cavities are the right atrium right  ventricle,  left  atrium,  and  left ventricle.    Each  chamber  connects  to a one-way valve.  When a cavity contracts, a  valve  opens  and  blood  flows  into  the chamber.  In summary, there  are  four valves,  each  associated  with  individual  chamber.   The following list identifies each valve with respective chamber.

·        Mitral  valve & left atrium    
·        Aortic valve & left ventricle 
·        Tricuspid valve & right atrium
·        Pulmonary valve& right ventricle
                                
                          The   heart pumps blood to the body in two steps. First,  the  right  and left  atria  contract,  moving  blood  to  the right  and  left  ventricles.    Second,  the ventricles  contract  simultaneously  to push  the  blood  out  of  the  heart  and through  the  body.    The heart then relaxes, allowing new blood to fill the atria.    This  contraction  of  the  atria  and the  ventricles  makes  up  a  heartbeat. Figure1 illustrates the anatomy of the human heart.   


                         The   human   body   needs   oxygen in order to live. The circulatory system is responsible for filtering oxygenated blood and deoxygenated blood from the body.  Blood enters in to   heart through two veins, the superior vena cava and the inferior vena cava. Both   of these veins feed de-oxygenated blood into the right atrium. The right atrium contracts sending blood to the right ventricle. Blood  flows  from  the  right  ventricle through  the  lungs  by  means  of  the  Pulmonary valve .With in the lungs the deoxygenated blood becomes oxygenated. The newly oxygenated blood flows through left atrium and ventricle, and the blood disperses through the body. Figure 2 recaps flow of blood through the heart.                            Like all machines, the Heart can malfunction numerous   ways. Cardiovascular   disease  occurs  when  the heart  becomes  “clogged,  broken  down, or  in  need  of  repair”.    Severe cardiovascular  disease  is  the  leading cause for heart transplantation,  but other malfunctions  such as  valve damage and chamber problems also  require  the need for   a  new  heart.   Currently, 12 million Indians have at least one kind of cardiovascular disease.   Heart disease is the number one cause of death in India. Since  many  conditions  fall  under  the in   category  of  cardiovascular  disease,  we will  focus  on  the  two  main  causes  for heart transplantation and artificial hearts: coronary heart disease  and  congestive heart failure .                                                                         
                     Coronary  heart  disease (CHD) afflicts  approximately  20  percent  of  all patients  diagnosed  with  cardiovascular disease.    Patient’s   symptoms   can range from being mild to intolerable.  CHD is the   hardening of   artery   walls   inside   the  heart.  Arteries are essentially piping   that   connects heart valves together. In CHD , the  transportation  of  blood  becomes  impaired  when  a  mixture  of  fat  and  cholesterol, or plaque, lines the arteries the buildup of plaque restricts the free flow of blood, which induces  pressure drop between the valves.  The  heart compensates  for  this  pressure  drop  by  pumping  harder  in  order  to provide enough  blood  for  the  entire  body Patients  suffering  from  CHD often  exhibit  symptoms  such  as  severe  chest pain  and  fatigue  due  to  the  lack  of  oxygenated  blood.  For severe cases of CHD, the only cure is a   heart transplant .Congestive heart failure (CHF) arises when the heart does not efficiently pump blood.  Since the heart is unable to pump enough oxygen-rich blood, blood starts to fill in the lungs, which leads to congestion.  Therefore, the heart must work   harder in order to meet the body’s oxygen demands.   This behavior cause’s excessive wear to the diseased organ initial symptoms of CHF, such as fatigue and swelling of the ankles, is usually so option. Until the condition becomes much more severe.    As  the  disease  progresses patients start to suffer  from  shortness of  breath  and  palpitations  even  while remaining  stationary.  For extremely, severe cases, transplantation is the only option.



3.  Effectiveness of Transplantation

                                Surgeons started developing heart transplantion techniques early as the 1900s.  Preliminary transplantations conducted on animals proved to  have fatal cosequences caused by the donor organ rejection.Therefore doctors were skeptical to try transplantation procedures on humans.
                    In  1905,  the  first  cardiac  heart transplant  was  performed  by  two surgeons  on  a  dog.  They  removed  the heart of a dog  and placed  into  the chest cavity  of  larger  dog  (Transplantation) Then the heartbeat  resumed but the  dog  transplantation. Though the experiment had fatal results,  this  event  stunned  the  medical community  and  spearheaded  further research  in  field  of  cardiac expired  two  hours  after  the  operation.
                                 By definition, heart transplantation is “The replacement of a patient’s diseased or injured heart with a healthy donor   heart”.    Reaching the exact definition of transplantation proved to be an extremely difficult task.   In order to deter organ rejection after transplantation, research was launched in field of immunosuppressant drugs.    An immunosuppressant drug restrains a transplanted patient’s immune system to prevent rejection of the implanted organ.
Dr.  Gertrude Elion   developed the first with end stage cardiovascular disease
in 1957.    Azathioprine proved to be useful tool that helped facilitate future
advancements in organ  transplantation.
                                      In 1967, Dr. Barnard performed the first human heart transplant in Cape Town, South Africa.    Dr.  Barnard implanted the donor heart from a 25-year old  female  into  a  55-year  old  female with  end  stage  cardiovascular  disease .she  lived  for  18  days  with  the transplanted  organ.    Ironically, the medication prescribed to suppress rejection of the new organ weakened his immune system.
                                     Current  heart  transplantation techniques  prove  to  be  a  viable  option .According  to  the  United  Network  of Organ  Sharing  (UNOS),  2,202  heart transplants  were  performed  in  2001  compared to 170 transplants performed in 1970.   Currently, approximately 70% of transplant patients live for   five or more years after transplantation [UNOS, 1999].    These  current  statistics  are staggering  in  comparison  to  the  14% survival  rate  from  the  early  1970s.Scientists  and  physicians  have  worked collectively  to  make  transplantation  a   safe and effective process.failure  patients,  there  are  many limitations to the procedure.  As of now more than 11,163 patients were awaiting heart transplant [UNOS, 2004].   Only about  quarter  of  these  patients  will receive  a  new  heart  [UNOS,  2004].Since  there  is  such  a  shortage of  donor hearts. 
                                    Therefore, further development provides a solution for all patients. Current development of artificial hearts strives to is necessary to provide a universal solution for these patients.


4. Total Artificial Heart Development


                                        The  development  of  artificial  hearts reflects  a  transition  from  a  support device  to  a  completely  self-contained machine. In the 1960s, the purpose of an artificial  heart  was  to  temporarily support  patients  until  a  donor  heart  became  available.    Surgeons  attempted successful;  however,  many  surgeons became  wary  of  this  device  because  it early  1980s  by  implanting  an  artificial heart  intended  for  long-term  therapy. The device they used was the Jarvik-7, a blood pump that replaces the heart’s ventricles.    The  procedure  was  initially  successful;  however,  many  surgeons became  wary  of  this  device  because  it did  not  offer  an  acceptable  quality  of life.    As  a  result,  the  public  began  to question  the  need  for   permanently removing  vital components  of the  heart. The  world of  artificial  heart  technology then  separated  into  two  classes:    assist devices  and  artificial  hearts.    In  the 1980s,  several  organizations,  including Abiomed  Inc.,  Penn  State  Medical Center,  and  the  Texas  Heart  Institute, began developing ideas for new designs. Their  intent  was  to  engineer  artificial hearts  that  could  permanently  sustain heart  failure  patients  while  providing  a decent quality of life.   These companies immediately encountered one huge barrier infection due to precutaneous or skin piercing, tubes. During  the  1980s,  every  artificial  heart had  power  cords,  blood  tubes,  or  air tubes  protruding  from skin. It was not until the early 1990s with the advent of transcutaneous technology.


Milestones in the Artificial Heart Technology
·        1960s       –       Surgeons implant the first temporary artificial heart.
·        1970s       –       Engineers   develop the ventricle assist device as an alternative
                                to artificial heart
·        1980s       –       First long term artificial heart results in poor quality of life.
                               VAD’s show potential for long term support.
·        1990s       –       Transcutaneous technology eliminates the need for skin – 
                                Protruding. Electrical wiring, patients with long-term VDA’s
                                      recovers from heart failure.                            
·        2000s       –       Results of the Abiocor   reflect   improved quality of life for
                               patients after implantation.


5.     A  Complete  Artificial  Implantable Heart


  This  device  is  a  permanent artificial  heart  that  is completely  self- contained within  the  body.   Some cases like they may have failure on both left and right side of the heart.   Before the introduction  of  the  device,  doctors  had no option than  to  let  these  patients  die. However, artificial  heart  developers, such as Abiomed  Corp.  and Penn State, focused  their  design  parameters  for patients  who’s  hearts  have  irreversibly failing  left  and  right  ventricles.    This category  of  patients  comprises  about 20%  of  those  in  need  of  a  heart transplant.   
                  Designs  for  this  device  initially  began in the early 1980s, around the time of the Jarvik-7.    Only  recently  has  the  device artificial  heart  received.  The  device. which  was  prepared  by  Abiomed    with the  same  principle  was   approved   by FDA  for clinical testing.  The large time span  for   approval  results  from  the controversy caused by the Jarvik-7.  The device  design  addresses  key  pitfalls encountered  with  the  Jarvik-7. Improvements  include  better  surface materials  to  reduce  blood  clotting and a newly  engineered  power   system  that does not require skin piercingelectrical cords.  These design considerations were  applied to the new model and clinical  testing  of the  device  made by  Abiomed has begun in the recent times. The first patient implanted with the device, was lived for nearly five months.  This event caught the attention of the public because
it was the first time a patient with an artificial heart was able to  stand  up  and  walk  around.    As of patients are alive today. Today, seven people received the and two

6.     Design  of  the  Complete Artificial Implantable Heart

 Three subsystems  implanted  under  the  skin  make  up  the design  of  the  device. These  subsystems  include  the  heart pump,  a  computerized  pump  controller, and  a  power source. All of the subsystems cumulatively,
 Weigh around 4 pounds and operate so quietly that stethoscope is needed to listen to the heart sounds.  Surgeons   implant the heart pump in the area from where the ventricles are removed. Channels that   connect naturally to the ventricles are then sewn into artificial cuffs that snap on to the heart. Two independent                         
hydraulic  motors  lie  inside  the  heart  One  motor  maintains  the  pumping    function to each ventricle while the other   motor  operates  the  motion  of  the  four  heart  valves.    The  pumping  motion operates  through  hydraulics  by  an oscillating  pusher  plate  that  squeezes sacs  which  alternatively  expel  blood  to the lungs and the body. When the blood sacs become full, the exit valves are shut and the entrance  valves  are  open.  The pump  then  squeezes  the  sacs,  which allows  the  exit  valves  to  open  and  the entrance valves to close. The  device  is  capable  of producing  more  than  two  gallons  of blood  every  minute,  which  signifies  a higher output than the Ventricular  assist devices(VAD).   Similar  in  design  to the VAD,  a  small  computer  secured  in  the abdomen  of  a  patient  automatically adjusts  the  output  of  the  pump.  The continual monitoring  of  blood  flow guarantees  that  incoming  flow  matches outgoing  flow.    This  rhythm  ensures steady  state  pumping  of the  heart.   The transfer of energy  is also  the  same as  in the  VAD.   Surgeons  implant  an  electric  coil  in  the  abdomen  area  to  allow  for energy transfer across the skin.  Patients wear a battery pack around the waist and must  change  the  batteries  several  times daily.    The  system  also  includes  an internal battery so that patient may  uncouple  the  external  power  source  in order to take a shower. One  significant   advantage  to  the  device is  the  smooth surface of  the  blood  sacs. Smooth plastics are important in order to ensure  constant  motion  of  blood  cells. Any time  blood  stops moving  along the of the device clotting develops. The smoothness of   the  plastic, called Angioflex, allows  for minimal  damage  to  the  blood. Angioflex  is  also  durable  enough  to withstand  1,00,000  beats  a  day  for several  years.    This  plastic  is  a  major  cont ibution to the life and to the safety of the device.
 

7. Conclusion

          Heart  failure  is  the  leading  cause  of death  in  India  and  also  all  over  the World.    Most  people  die  from  heart failure chambers,  fail  to  push  enough  blood through  the  body.  A  solution  to  donor heart  rejection  surfaced  in  the  early 1980s  with  the  advent  of  cyclosporine an  immunosuppressant  and this discovery,  the  average  survival rate of heart transplant patients increased to more than 5 years. One  of  the  drawbacks  to  heart transplantation  is  its availability is only half of the  patients  needing  a  heart transplant will receive a donor  heart  The  development  of  artificial hearts resurfaced again in 1993 with the advent of transcutaneous  technology. Transcutaneous  technology is  based  on the transfer of 
power  across the  skin  by electric  coils.This technology eliminates infection due to  skin- protruding  electrical  tubes.    Artificial hearts  and  heart  transplantation  are  the only  methods  for  saving  the  lives  of patients with heart failure.  As  of today, heart  transplantation  is  the  official method  for  replacing  the  human  heart. But, donor hearts are not available to all  patients.    Heart  transplantation  and artificial  hearts  are  not  a  competing source  of  technology.    These technologies  exist  parallel  to  each  other in  order  to  encompass  the  whole population of  patients  in  need  of  a  new heart.  Hope  this  technology  will  soon reach to  the  common  man  in  I NDIA.

8. Bibliography
         
www.bbcworld.comot
www.abiomed.com
www.cnn.com
www.heartcenteronline.com

Reference:
.   Anatomy and physiology:   by   Tortora and Grabowski


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