- Provides an educational review of recent advances
- Focuses on biomedical high technology
- Features contributions from leaders in the field
- Provides an educational review of recent advances
- Focuses on biomedical high technology
- Features contributions from leaders in the field
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Overview
- Provides an educational review of recent advances
- Focuses on biomedical high technology
- Features contributions from leaders in the field
Product Details
| ISBN-13: | 9780080932088 |
|---|---|
| Publisher: | Elsevier Science |
| Publication date: | 09/11/2008 |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 320 |
| File size: | 8 MB |
Read an Excerpt
Advances in Biomedical Engineering
ELSEVIER
Copyright © 2009 Elsevier B.V.All right reserved.
ISBN: 978-0-08-093208-8
Chapter One
Review of Research in Cardiovascular DevicesZbigniew Nawrat
Contents
1. Introduction 2 2. The Heart Diseases 8 3. The Cardiovascular Devices in Open-Heart Surgery 8 3.1. Blood Pumps 9 3.2. Valve Prostheses 23 3.3. Heart Pacemaker 34 4. The Minimally Invasive Cardiology Tools 34 5. The Technology for Atrial Fibrillation 38 6. Minimally Invasive Surgery 39 6.1. The Classical Thoracoscopic Tools 40 6.2. The Surgical Robots 43 6.3. Blood Pumps - MIS Application Study 49 7. The Minimally Invasive Valve Implantation 53 8. Support Technology for Surgery Planning 53 9. Conclusions 57 Acknowledgments 58 References 58
Abstract
An explosion in multidisciplinary research, combining mechanical, chemical, and electrical engineering with physiology and medicine, during the 1960s created huge advances in modern health care. In cardiovascular therapy, lifesaving implantable defibrillators, ventricular assist devices, catheter-based ablation devices, vascular stent technology, and cell and tissue engineering technologies have been introduced. The latest and leading technology presents robots intended to keep the surgeon in the most comfortable, dexterous, and ergonomic position during the entire procedure. The branch of the medical and rehabilitation robotics includes the manipulators and robots providing surgery, therapy, prosthetics, and rehabilitation. This chapter provides an overview of research in cardiac surgery devices.
Keywords: Heart prostheses, valve prostheses, blood pumps, stents, training and expert systems, surgical tools, medical robots, biomaterials
1. Introduction
Remarkable advances in biomedical engineering create new possibilities of help for people with heart diseases. This chapter provides an overview of research in cardiac surgery devices. An explosion in multidisciplinary research, combining mechanical, chemical, and electrical engineering with physiology and medicine, during the 1960s created huge advances in modern health care. This decade opened new possibilities in aerospace traveling and in human body organ replacement. Homo sapiens after World War II trauma became not only the hero of mind and progress but also the creator of the culture of freedom. Computed tomographic (CT) scanning was developed at EMI Research Laboratories (Hayes, Middlesex, England) funded in part by the success of EMI's Beatles records. Modern medical imaging techniques such as CT, nuclear magnetic resonance (NMR), and ultrasonic imaging enable the surgeon to have a very precise representation of internal anatomy as preoperative scans. It creates possibilities of realizing new intervention methods, for instance, the very popular bypass surgery. It was a revolution in disease diagnosis and generally in medicine. In cardiovascular therapy, lifesaving implantable defibrillators, ventricular assist devices (VADs), catheter-based ablation devices, vascular stent technology, and cell and tissue engineering technologies have been introduced.
Currently, the number of people on Earth is more than 6 billion: increasingly lesser number of living organisms and about million increasingly more "intelligent" robots accompany them.
Robotics, a technical discipline, deals with the synthesis of certain functions of the human using some mechanisms, sensors, actuators, and computers. Among many types of robotics is the medical and rehabilitation robotics - the latest but rapidly developing branch at present, which includes the manipulators and robots providing surgery, therapy, prosthetics, and rehabilitation. They help fight pareses in humans and can also fulfill the role of a patient's assistant. Rehabilitation manipulators can be steered using ergonomic user interfaces - e.g., the head, the chin, and eye movements. The "nurse" robots for patients and physically challenged persons' service are being developed very quickly. Partially or fully robotic devices help in almost all life actions, such as person moving or consuming meals, simple mechanical devices, science education, and entertainment activities. Help-Mate, an already existing robot-nurse, moving on the hospital corridors and rooms delivers meals, helps find the right way, etc.
On the one hand, robots are created that resemble the human body in appearance (humanoids), able to direct care; on the other hand, robotic devices are constructed - telemanipulators - controlled by the human tools allowing to improve the precision of human tasks. Robots such as ISAC (Highbrow Soft Arm Control) or HelpMate can replace several functions of the nurse, who will give information, help find the way, bring the medicines and the meal. In case of lack of qualified staff, to provide care for hospice patients at home, these robots will be of irreplaceable help.
Robotic surgery was born out of microsurgery and endoscopic experience. Minimally invasive interventions require a multitude of technical devices: cameras, light sources, special tools (offering the mechanical efficiency and tissue coagulation for preventing bleeding), and insufflations (thanks to advances in computer engineering, electronics, optics, materials, and miniaturization). The mobility of instruments is decreased [from seven, natural for human arm, to four degrees of freedom (DOFs)] due to the invariant point of insertion through the patient's body wall. Across the world, physicians and engineers are working together toward developing increasingly effective instruments to enable surgery using the latest technology. The leading technology presents robots intended to keep the surgeon in the most comfortable, dexterous, and ergonomic position during the entire procedure. The surgery is complex and requires precise control of position and force. The basic advantages of minimally invasive robot-aided surgery are safe, reliable, and repeatable operative results with less patient pain, trauma, and recovery time. Conventional open-heart surgery requires full median sternotomy, which means cracking of sternum, compromising pulmonary function, and considerable loss of blood.
2. The Heart Diseases
The human biological heart has two sets of pumping chambers. The right atrium receives oxygen-depleted blood from the body, which is pumped into the lungs through the right ventricle. The left atrium receives aerated blood from the lungs, which is pumped out to the body through the left ventricle. With each heart beat, the ventricles contract together. The valves control the direction of blood flow through the heart.
Congestive heart failure, a condition in which the heart is unable to pump the blood effectively throughout the body, is one of the leading causes of death. This disease is caused by sudden damage from heart attacks, deterioration from viral infections, valve malfunctions, high blood pressure, and other problems. Although medication and surgical techniques can help control symptoms, the only cure for heart failure is heart transplantation. Artificial hearts and pump assist devices have thus been developed as potential alternatives.
Ischemic heart disease is caused by progressive atherosclerosis with increasing occlusion of coronary arteries resulting in a reduction in coronary blood flow. Blood flow can be further decreased by superimposed events such as vasospasm, thrombosis, or circulatory changes leading to hypoperfusion. Myocardial infarction (MI) is the rapid development of myocardial necrosis caused by a critical imbalance between the oxygen supply and the oxygen demand of the myocardium. Coronary artery bypass grafts (CABGs) are implanted in patients with stenosed coronary arteries to support myocardial blood flow.
Valvular heart disease is a life-threatening disease that affects millions of people worldwide and leads to valve repairs and/or replacements.
In the USA and Europe alone, with more than 600 million inhabitants and more than 6million patients with heart failure, the prevalence of advanced heart failure, constituting 1-10% of the heart failure population, is estimated to total between 60,000 and 600,000 patients. More than 700,000 Americans die each year from heart failure, making it the number one cause of death in the U.S., as well as worldwide. About half of these are sudden cardiac deaths, which occur so quickly that there is not enough time for intervention with a cardiac assist or replacement device. For the remaining half, heart transplantation is one of the few options available today. Though hundreds of thousands are in need, only about 2,000 people in the U.S. will be able to receive donor hearts every year. This consistent shortage in the supply of donor hearts in the U.S. demonstrates the need for an alternative to heart transplantation. The total potential market for the artificial heart is more than 100,000 people in the U.S. each year. (http://www.abiomed.com).
3. The Cardiovascular Devices in Open-Heart Surgery
Cardiac surgery is surgery on the heart and/or great vessels. This surgery is a complex procedure requiring precise control of position and force. Conventional open-heart surgery requires full median sternotomy, which means cracking of sternum, compromising pulmonary function, and considerable loss of blood.
The repair of intracardiac defects requires a bloodless and motionless environment, which means that the heart should be stopped and drained of blood. Hence, the patient requires the function of the heart and lungs provided by an artificial method.
Modern heart-lung machines can perform a number of other tasks required for a safe open-heart operation. This system preserves the patient's own blood throughout the operation and the patient's body temperature can be controlled by selectively cooling or heating the blood as it flows through the heart-lung machine. Medications and anesthetic drugs can be administered via separate connections. The disadvantages include the formation of small blood clots, which increase the risk of stroke, pulmonary complications, and renal complications. The machine can also trigger an inflammatory process that can damage many of the body's systems and organs. Those risks push today's biomedical engineers to improve the heart-lung machine and oxygenator, while surgeons are developing advances that would eliminate the need for the machine altogether. One such advance is minimally invasive surgery (MIS).
The surgeons have begun to perform "off-pump bypass surgery" - coronary artery bypass surgery without the aforementioned cardiopulmonary bypass. The surgeons operate on the beating heart stabilized to provide an (almost) still work area. One of the greatest challenges in beating-heart surgery is the difficulty of suturing or sewing on a beating heart. A stabilization system makes it possible for the surgeon to work on the patient's beating heart carefully and, in the vast majority of cases, eliminates the need for the heart-lung machine.
3.1. Blood Pumps
The human heart is a pump that is made of muscle tissue. A special group of cells called the sinus node is located in the right atrium. The sinus node generates electrical stimuli that make the heart contract and pump out blood. The normal human heart beats about 75 times per minute (i.e., about 40 million times a year) - i.e., the heart pumps 5 l of blood per minute. The normal systemic blood pressure is 120/80 mmHg. The mechanical power (calculated by multiplying the pressure by the flow rate) of the human heart is about 1.3 W. However, to provide this mechanical power, the heart requires 10 times much higher rate of energy turnover, owing to its low mechanical efficiency (less than 10%).
However, the development in biotechnology can open the opportunity for tissue engineering (a branch of biotechnology) - a prospect of saving people with extremely complex or irreversible failure heart will still be realized using mechanical heart support devices.
During the last half-century, various blood pumps were introduced into clinical practice, which can partially support or replace the heart during open-heart surgery or considerably for a longer time period until heart recovers or until transplantation is performed. Several millions of people owe their health and lives to these devices. According to the American Heart Association, an estimated 5 million Americans are living with heart failure and more than 400,000 new cases are diagnosed every year. About 50% of all patients die within 5 years.
The first operation on a beating heart was performed by Gibbon in 1953 using a peristaltic pump. Since then, there has been rapid development in mechanical assist devices, leading to the realization of today's mechanical aid system for blood circulation, based on the requirements using the following:
intra-aortic balloon pump (IABP)
continuous blood flow devices - roll and centrifugal rotary pumps
pulsating flow blood pumps - pneumatic or electro-control membrane pumps
The assumed time of blood pump using in the organism influences the construction and material used in its design. According to this criterion, the pumps can be divided into following categories:
short-term (during the operation or in sudden rescue operations)
medium-term - over several weeks or months (as a bridge to heart transplantation or treatment)
long-term - several years (already at present) and permanently (in the intention) (as the target therapy)
The extracorporeal circulation (perfusion) and the controlled stopping of heart action make it possible to perform the open-heart operation. The peristaltic pumps are in common use, where the turning roll locally tightens the silicon drain to move a suitable volume of the blood. The disadvantages of this procedure, such as the damage to blood components, are eliminated or reduced by pump construction and material improvement. The patients with both heart and lung failure are assisted by the system consisting of pump and oxygenator. The method of time oxygenation (supply oxygen to the blood) for extracorporeal blood - extracorporeal membrane oxygenation (ECMO) - was applied the first time in 1972 by Hill. The blood pump, membrane oxygenator, heat exchanger, and a system of cannulas (tubes) for patient's vascular system connection are the elements of the system. Inner surface of all these parts are covered with heparin. The Extracorporeal Life Support Organization Registry has collected (since 1989) data on more than 30,000 patients, most of whom have been neonates with respiratory failure [7]. The currently available centrifugal pump VADs are BioMedicus BioPump (Medtronic, Minneapolis, MN, USA), CentriMag[R] (Levitronix, Zürich, Switzerland), RotaFlow[R] (Jostra, Hirrlingen, Germany), and Capiox[R] (Terumo, Ann Arbor, MI, USA). These pumps have been available since 1989 to support neonates and older children with postoperative cardiac failure but competent lung function.
Centrifugal pumps benefit from the physical phenomena (centrifugal, inertia force) of blood acceleration during temporal rotational movement. These pumps consist of a driving unit and an acrylic head driven by a magnetic couple. Input and output blood flow channels are perpendicular to each other. The output velocity of the blood on the conical rotor depends on the input rotary speed, preload, and afterload. Based on vortex technology, these pumps use turbine spins of 10,000-20,000 rpm to create a flow of 5-6 l/min and have generally been applied for temporary assistance of stunned myocardium of the left ventricle. The construction of working pump and its environment conditions influence the blood hemolysis during its use. According to the results of in vitro experiment, with the pump working as VAD and extracorporeal circulation (CPB and ECMO), the use of the pump as VAD caused the least degree of hemolysis, and the hemolysis of pumps in the time to ECMO strongly depends on the kind of oxygenator used. Pumps with the conical rotor caused a greater degree of hemolysis working with small flows and large pressures (ECMO). On the contrary, a lesser degree of hemolysis was observed for pumps with the flat rotor, regardless of its purpose.
(Continues...)
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Table of Contents
1. Review of Research in Cardiovascular DevicesD. Zbigniew Nawrat
2. Biomechanical modelling of Stents: Survey 1997-2007
Matthieu De Beule
3. Signal Extraction in Multisensor Biomedical Recordings
V. Zarzoso, R. Phlypo, O. Meste and P. Comon
4. Fluorescence Lifetime Spectroscopy and Imaging of Visible Fluorescent Proteins
Ankur Jain, Christian Blum and Vinod Subramaniam
5. Monte Carlo Simulations in Nuclear Medicine Imaging
Steven Staelens and Irene Buvat
6. Biomedical Visualization
Chris R. Johnson and Xavier Tricoche