ANATOMY AND FUNCTION
The human heart is a pear-shaped structure about the size of a fist. It lies obliquely within the chest cavity just left of center, with the apex pointing downward. The heart is constructed of a special kind of muscle called myocardium or cardiac muscle, and is enclosed in a double-layered, membranous sac known as the pericardium. A wall of muscle divides the heart into two cavities: the left cavity pumps blood throughout the body, while the right cavity pumps blood only through the lungs. Each cavity is in turn divided into two chambers, the upper ones called atria, the lower ones ventricles. Venous blood from the body, containing large amounts of carbon dioxide, returns to the right atrium. It enters the right ventricle, which contracts, pumping blood through the pulmonary artery to the lungs. Oxygenated blood returns from the lungs to the left atrium and enters the left ventricle, which contracts, forcing the blood into the aorta, from which it is distributed throughout the body. In addition, the heart employs a separate vascular system to obtain blood for its own nourishment. Two major coronary arteries regulate this blood supply.CARDIAC CYCLEBlood flows through the heart in one direction only. It is prevented from backing up by a series of valves at various openings: the tricuspid valve between the right atrium and right ventricle; the bicuspid, or mitral, valve between the left atrium and left ventricle; and the semilunar valves in the aorta and the pulmonary artery. Each heartbeat, or cardiac cycle, is divided into two phases. In the first phase, a short period of ventricular contraction known as the systole, the tricuspid and mitral valves snap shut, producing the familiar "lub" sound heard in the physician's stethoscope. In the second phase, a slightly longer period of ventricular relaxation known as the diastole, the pulmonary and aortic valves close up, producing the characteristic "dub" sound. Both sides of the heart contract, empty, relax, and fill simultaneously; therefore, only one systole and one diastole are felt. The normal heart has a rate of 72 beats per minute, but in infants the rate may be as high as 120 beats, and in children about 90 beats, per minute. Each heartbeat is stimulated by an electrical impulse that originates in a small strip of heart tissue known as the sinoatrial (S-A) node, or pacemaker.
ADVANCES IN CARDIOLOGY
One of the important advances in cardiology is the artificial pacemaker used to electrically initiate a normal heartbeat when the patient's own pacemaker is defective (see arrhythmia); it may be surgically implanted in the patient's body. Similarly, an internal defibrillator may be implanted to deliver an electrical shock to the heart in order to stop certain forms of rapid heart rhythm disturbances. Another familiar tool of the cardiologist is the electrocardiograph (EKG), which is used to detect abnormalities that are not evident from a physical examination (see electrocardiography).The most important advance in the treatment of heart disease has been the human heart transplant. The first heart transplanted into a human occurred in 1964 Dr. James Hardy transplanted a chimpanzee heart into a dying patient. The patient lived for 90 minutes before the heart stopped beating. In over 40 years since Dr. Hardy's breakthrough surgery Doctors have vastly improved the heart transplantation technique. Survival rates have greatly increased over the past 20 years, and as of Aug. 11, 2006, the survival rates were as follows.·1 year: 86.1% (males), 83.9% (females) ·3 years: 78.3% (males), 74.9% (females) ·5 years: 71.2% (males), 66.9% (females) In the 1980s new advances in the design and construction of an artificial heart—both the entire organ and such parts as the valves and large blood vessels—showed some promise in treating cardiovascular disease, but the limited success that has characterized artificial heart implantation thus far has led many experts to question the efficacy of such measures. Although the artificial heart has often been used as a temporary measure until a permanent human donor heart can be located, a number of recipients have not fared well, even for a limited duration. In addition, it is often unclear how long the recipient will have to wait for a donor heart. Of which there are not nearly enough donor hearts and many people die while on the waiting list. Proponents of the artificial heart hope that technological advances will allow the permanent replacement of human hearts with artificial ones.The most promising type of research being done today is in the field of stem cell research. Even with the ridiculous policy during the Bush years of prohibiting federal funding of stem cell research doctors have still been making great strides forward in the field. On April 30, 2008 stem cell researchers at UCLA were able to grow functioning cardiac cells using mouse skin cells that had been reprogrammed into cells with the same unlimited properties as embryonic stem cells. The finding is the first to show that induced pluripotent stem cells or iPS cells, which don't involve the use of embryos or eggs, can be differentiated into the three types of cardiovascular cells needed to repair the heart and blood vessels. The discovery could one day lead to clinical trials of new treatments for people who suffer heart attacks, have atherosclerosis or are in heart failure. These types of advances in research are nothing less than amazing. But they still have a good deal of time to go before their research will directly help people suffering from heart disease today. Additionally the mere fact that researchers are having to waste years, and billions of dollars, trying to find an alternative to perfectly viable embryonic stem cells for research shows just how controlled by religious ideology our government truly is.As of 2010 we now have a president who is not buried in religious idiocy and supports stem cell research. Thank you President Obama. But of course immediately after President Obama’s decision to allow the use of federal funding for stem cell research the religious zealots in America immediately went to court to fight against it and after only a month of sanity they are tying up scientific progress once again. If I were a guest on Real Time with Bill Maher I would go off on a rant. But this is a research/optimistic site so I will keep my opinions to myself.There is a vast wealth of knowledge on the Internet dealing with heart disease that is easily accessible. Well beyond what I could possibly fit on this site. So rather than placing it redundantly here, I have posted some of what I consider the most helpful web sites below.
THE HUMAN HEART
Medical professionals are constantly vigilant in their research to find new ways to cure the many different types of Heart Disease. Heart disease is a generic term for a number of different diseases affecting the heart. As of 2007, it is the leading cause of death in the United States, England, Canada and Wales, killing one person every 34 seconds in the United States alone. Our heart is a muscular organ, which is responsible for pumping blood through the blood vessels by repeated, rhythmic contractions. The heart is composed of cardiac muscle, an involuntary muscle tissue that is found only within this organ. The average human heart beating at 72 BPM beats over 100,000 times per day feeding every cell in our body with life giving blood.The heart is a tireless workhorse that we as humans push to the limits of its abilities every day. The heart only gets to rest one-half of a second at a time, if it is lucky. It never gets to shut down. Never takes a "nap". It is the most amazing machine ever imagined. It beats continuously from only a few weeks after we are conceived until the time we die. It is unimaginably tough. Yet it is also very fragile. Heart disease is the leading cause of death in the United States and is a major cause of disability. Almost 700,000 people die of heart disease in the U.S. each year. That is about 29% of all U.S. deaths. Heart disease is a term that includes several more specific heart conditions. The most common heart disease in the United States is coronary heart disease, which can lead to heart attack. The heart is susceptible to many negative influences that can have detrimental effects on it. Including but not limited to diabetes, high cholesterol, high blood pressure, obesity, heredity, genetics, cigarette smoke, drugs, and alcohol just to name a few.