Cardiac transplantation is presently the optimum surgical treatment for heart failure. Allograft transplantation result in 90% survival in one year and 50% survival in five years with return to a near normal quality of life. However, the scarcity of donor organs means that less than one tenth of potential recipients receive an organ. Recent successful heart transplantation’s performed using Dead man’s heart (not brain dead man) as a heart donor has given a new hope to the potential recipients. Longer term problems include a prevalence of coronary artery disease, due to chronic immunological rejection, renal impairment due to cyclosporine toxicity, and an increased risk of malignancy because of chronic immune-suppression. Despite recent claims for transgenic porcine hearts and the potential for their off the shelf” availability, rejection of xeno transplants is likely to be worse than for allograft and is unlikely to be solved by immune-suppressive agents alone. This, together with the possibility of retrovirus transmission, has led to the recent moratorium on the progression to human xeno transplants.
Mechanical support devices
In the last few years, implantable mechanical support devices have joined the list of long term options for heart failure. These devices, initially used in the 1960s to completely replace the native heart in moribund patients awaiting transplantation, required fixed attachment of the patient to a bulky external console. In contrast, the current implantable left ventricular assist devices augment the function of the native heart and can be powered by portable battery packs. Their success in supporting patients awaiting transplantation over months (“bridge to transplant”), allied to the growing imbalance between demand for the supply of hearts for transplantation, has encouraged their permanent implantation. Two electrically driven left ventricular assist devices (the Novacor and the heartmate) are now available for long term implantation. Their major limitations are the risks of infection, thromboembolism, noise, and batteries that need to be charged every eight to twelve hours.
Two newer concepts show promise in the surgical treatment of heart failure. The jarvik 2000 is an axial flow pump, about the size of a thumb( in contrast to the one litre volume displacement of the heartmate), designed to sit within the apex of the left ventricular and silently deliver non-pulsatile flow rates upto 10 litres per minutes. Its long term physiological effects are still under investigation, but in animal models it has shown excellent haemodynamic performance without evidence of haemolysis, but in animal models it has shown excellent haemodynamic performance without evidence of haemolyisis. It is likely to be avialble for clinical use within a year. Secondly, evidence is accumulating that prolonged support with left ventricular assist devices may allow at least some recovery of native cardiac functions. Reports are emerging of succelful explants of devices after three to six months of support. The raises the fascinating possibility that mechanical intervention at an earlier stage in the course of certain types of heart failure, including viral myocarditis and dilated cardiomyopathy, might restore normal cardiac function (“bridge to recovery”)
Many question remain unanswered. Left ventricular assist devices are inherently expensive, but randomized trials comparing them with medical treatment or transplantation may prove them cost effective. Should they be used at an earlier stage of heart failure in the hope of promoting native cardiac recovery? Would a silent, miniaturized, fully implantable device prove preferable to conventional transplantation or xenotransplantation with immunosuppressant and other inherent problems? Is it possible that these different surgical approaches to heart failure might become complimentary treatments at different stages of the disease, allowing the surgical procedure to be tailored to individual patients? The current lack of donor organs for transplantation adds urgency to the debate.
Fetal Cardiac Surgery
The aim of fetal intervention should be to provide foetuses with heart defects, who had hitherto been “condemned-to-die”, a meaningful chance of survival. Preserving heart muscle function, preventing progression of already existing changes(like a condition called Fibroelastosis), and restoring a near-normal pattern of growth to the heart chambers and blood vessels are the targets of fetal surgery. If this is achieved, then any future operations after the child is born could be fully reconstructive, done at a single stage and with reasonable chances of restoring a normal heart, and a normal life span to the survivor.
Contrast this with the present situation where corrective operations for complex heart defects need to be done in multiple stages, each with its own risks and complications, and ultimately resulting in a life expectancy and a lifestyle considerably different from normal persons. That such ideals can be achieved is suggested by the encouraging results of animal experiments. To perform surgery on intracardiac structures or great vessels, it is necessary to put the fetus on extracorporeal circulation(i.e., Cardiac bypass). Since the fetus is already on physiologic ‘bypass via the placenta, extracorporeal cardiac bypass in the fetus is much more complex that cardiopulmonary bypass can be safely performed in foetuses as small as 450 grams with transfusion.
The current status of fetal cardiac surgery is similar to the field of infant heart surgery 60 years ago, when it was clear that correction of certain congenital defects would provide great benefit, but there was no safe and effective method to gain access to the heart. However, with the development cardiopulmonary bypass (CPB) equipment and techniques, intraoperatives access to the heart became possible. This allowed postnatal cardiac surgery to be done safely and effectively. If similar “low risk”techniques, understanding and equipment existed for the fetus, there would be little argument that fetal cardiac surgery would be preferable e for certain congenital lesions. I predict that when fetal cardiac surgical techniques become equally advanced and safe, (which won’t be long), innovative cardiac surgeons will surely expand the indications for the procedure to cover the entire spectrum of congenital heart disease. And that would be the end of birth defects of the heart, as we know them today. This sure is a great time to be a cardiac surgeon!
Genetic Engineering
Concept of genetic engineering was a introduced by Herbert boyer and stenley cohen in the year 1971. In 1969, they performed studies on a couple of properties of enzymes known as aldectase. Boyer observed that these enzymes have the capability of cutting DNA strands in a particular fashion, which left what has become known as ‘sticky ends’ on the strands. These clipped ends are made by pasting together pieces of DNA which is a precise exercise. This discovery, in turn, led to a rich and rewarding conversation in Hawaii with a Stanford scientist named Stanley cohen. Cohen had been studying small ringles of DNA called plasmids which float about freely in the cytoplasm of certain bacterial cells and replicate independently from the coding strand of DNA. Cohen had developed a method of removing theses plasmids from the cell and then reinserting them in other cells. Combining this process with that of DNA splicing enabled Boyer and Cohen to recombine segments of DNA in desired configurations and insert the DNA in bacterial cells, which could then act as manufacturing plants for specific proteins . This breakthrough was the basis upon which the discipline of Generic engineering was founded. Modern molecular genetics has revolutionized medicine and our knowledge of ourselves. In simple terms, genetic engineering (GE) is the ability to manipulate the genes of an organism to produce a given protein or obtain organisms that have a given trait.
The first big success of GE was the production of insulin by genetically modified bacteria. It showed the medical, economical and industrial possibilities of this technology. Like a pyramid buried in the sands of desert, the possibilities and usage of GE were being uncovered. Thanks to refined techniques in molecular genetics and recombinant DNA techniques, its usage soon started to be employed in vast array of areas.
The greatest applications of genetics are in medicine. By knowing which gene, which piece of the genetic code is responsible for a given disease, physicians can diagnose the disease. It also provides scientists the opportunity to understand how disease occur and eventually develop treatments. A large part of modern biomedical research is conducted based on genetics and GE. For instance, in the field of aging research, we can alter the pace of aging in animal models by modifying in a single gene which allows us to study why we age and how can we treat the disease of old-age. At least until nanotechnology arrives. GE is the ultimate bio tool.
The possibilities for applying GE to change the human genome are immense: there are genes that offer protection against disease such as cancer and AIDS, genes that code enhanced senses and intelligence, anything we can imagine. For instance, it may be possible in near future to go the doctor and have a gene inserted that gives rise to a stronger immune system. Another technology is gene therapy, which usually works by injecting special viruses into patients that then deliver the gene of interest into the patient’s cells.
There are thousands of genetic diseases that are encoded by the nuclear genome, such as the Down’s syndrome. A complicated option to take care is pre-implantation genetic diagnosis (PGD). In this technique, used to create what is often called a “designer baby”‘ an embryo is created by in-vitro-fertilization(IVF) and tested for genetic diseases and genomic imbalances that can cause problems to the child. This technique allows for the selection of healthy babies, but also to create a baby to treat a sick sibling. The next step in “designer babies” is to use GE to correct genetic diseases in the embryo. Importantly, germinal GE would allow for the evolution of the human species.
The 47th Chromosome, also called techno chromosome, is a therotical concept that proposes adding a new chromosome, or more likely a pair of chromosomes, to our current set of 46 chrosomes. This would allow us to include all the changes we desire without the danger of creating genetic imbalances by changing our current chromosomes. Molecular system engineering has created an artificial chromosome that can be passed into the progeny of mice, and there are attempts to expand this research into humans as cell mendiated gene therapy and stem cell therapy, so this is not science fiction. Forecasting the future isn’t easy. Nevertheless, it may be hoped that one day ene-therapy will realize its full potential and all the ailments of humanity will be wiped out from the face of day Gene-therapy will realize its full potential and all the ailments of humanity will be wiped out from the face of earth. Then no doubt, it will be total demise of cardiac surgery and cardiac surgeons will be busy in cutting and uniting the DNA creating new generation beyond humans.
Stem-Cell therapy-an adjust to heart surgery
The addiction of stem cells should help boost heart function and improve quality of life. Probably the most profound effect or benefit that patients could experience from an increase in EF is in their overall quality of life. “People below 40 percent begin to realize real limitations in exercise and their ability to perform activities of daily living. Those with EFs in the 20s can be severely restricted or disabled. Fortunately, stem cells have been shown to help those with the lowest EFs the most.
Stem cell probably functions best by helping save existing myocytes from death, not by creating new ones. The stem cells also seen to “stabilize the cytoskeleton of the heart and act as a ‘functional patch’ to maintain the proper geometry of the heart, which is very critical to the overall performance of the heart as it undergoes remodelling from injury”. Regenerative medicine, which includes stem cell therapies, is a highly translational field and there is a great deal of bench to bed-side and back to the bench that take place. Most investigators involved in these trials will need expertise both in the animal lab and with conducting human clinical trials.
Digitalisation of Cardiac Surgery
Tele cardiac surgery
Hippocrates(480-390 B.C) defined surgery as the therapeutic activity practiced by the means of the “hands.” The twentieth century has seen the addiction of laparoscopic surgery that moved the surgeon’s hand outside the body to reduce surgical trauma and improve patient outcomes. Despite these advances, some form of physical contact between the surgeon and patient has always remained. Surgical robotics at the turnoff the twenty-first century has produced the technology to disrupt even the paradigm of surgeon-patient proximity. Robotics entered the operating room in 1985 with the PUMA 200 industrial robot adapted for CT-guided biopsy. This first generation of surgical robots was notable was notable for performing image-guided precision tasks but was limited by the need for preoperative planning and basic computer interfaces. The development of telesurgery started in the 1970s with the aim to replace the surgeon’s physical presence in situations of mass casualties in hostile environments such as war or natural catastrophes. The ability to deliver surgical expertise to distant locations will benefit patients worldwide, especially those residing in rural areas with poor communication. Surgical candidates who cannot access to the health care facility for advanced cardiac care can be helped with this technology for primary consultation with a cardiac surgeon and further planning for required treatment.
Tele-education
The concept of telemedicine can also be applied for educational purpose. Eminent medical professionals can deliver lectures and demonstrations and perform live workshops which can be transmitted to remote places and institutes for the benefit of medical students. It saves lives in emergency situations when there is no time to take the patient to a hospital owing to remote location with poor connectivity of the place. Those patients residing in inaccessible areas or isolated regions like rural areas, can receive clinical healthcare from their home without arduous travel to the hospital. Telemedicine is an innovative system of healthcare provision from long distance utilizing the telecommunication and modern information technologies. Though this concept arrived in 20th century with telephone & radio, today diverse advanced technologies, including video telephone, latest tele-medical devices, mobile cooperation technology, diagnostic methods, distributed client or server applications etc. have upgraded the quality and extent of telemedicine service. This system has eliminated distance barriers to deliver clinical healthcare.
While the future is hard to predict, one thing is for sure, the paradigm of physical contact between the surgeon and patient has broken leading to an era where surgeons can advise and operate from across the room, across the country, and even across continents and impart education virtually.
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| http://www.slideboom.com/presentations/2282230/Heart-Transplant-In-Delhi |
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