Recent Changes

Perhaps because of the prevalence of cardiac disease as well as the symbolic significance of the heart, concern for heart-related diseases has been central to much of what we have come to identify as late-twentieth-century medicine. That includes both "high-tech" innovations and preventive medicine strategies, such as risk-factor intervention and lifestyle modifications.

The echocardiogram is a "high-tech" approach to cardiac diagnosis based on the reflection of sound waves in the body. The technique was first demonstrated in the 1950s, and recent advances have greatly increased the quality of the images, such that it is possible to diagnose heart disease even in a fetus. By bouncing sound waves off the interior of the heart, a picture can be generated that reflects the heart's anatomy, and by the use of small air bubbles to provide contrast, the passage of blood can also be traced. The echocardiogram's greatest advantages lie in its complete safety (so far as is now known) and freedom from pain.

Other imaging techniques applied to cardiac disease include tagging blood constituents with radioactive substances (which can be used to measure both function and blood flow) and both computerized axial tomography and magnetic resonance imaging. The latter two techniques make use of digital processing and imaging to provide cross-sectional images based on a computerized reconstruction of the information provided by scanning from many different directions. In addition, computerized axial tomography and positron emission tomography are now being used to measure the metabolic state of the heart muscle.

Treatment of patients with acute myocardial infarction has evolved from observing and supporting the patient to attempting to intervene in the disease process itself. Typically, patients with myocardial infarction suffer from an obstruction of one of the coronary arteries that supply blood to the heart. Two methods for relieving that obstruction are now being used, one mechanical and one in which medication dissolves the blockage. The mechanical intervention is percutaneous transluminal coronary angioplasty (PCTA), during which a catheter is directed into the coronary artery and expanded in order to clear the lumen. Since its introduction in 1977, PCTA has become widely used for the treatment of coronary disease. The number of procedures performed in the United States rose from 32,206 in 1983 to 175,680 in 1987. The procedure has also become popular in other countries, with approximately 12,000 procedures being done in the Federal Republic of Germany and 10,048 in Japan during 1987. The initial success rate approaches 95 percent at some institutions, but a significant percentage of patients experience later failure. PCTA continues to be used for people who suffer from symptoms caused by an obstruction of the coronary arteries, but who have not yet suffered death of the heart muscle. The technique has been attempted as well with patients who have recently suffered death of the heart muscle, causing myocardial infarction, but recent studies suggest that it is not as useful for urgent therapy.

Tissue-dissolving agents include products of recombinant DNA technology. These agents should be administered soon after a person suffers a heart at tack in order to dissolve the clot before irreversible damage has been done to the heart muscle. Although PCTA requires rapid transportation of a heart attack patient to the hospital, often via helicopter, treatment with clot-dissolving agents can be initiated before the patient reaches the hospital. This therapy must be closely monitored, however, making hospitalization necessary for optimal treatment. This may negate studies from the 1970s that showed that hospitalization made no difference in the prognosis of patients suffering from an uncomplicated myocardial infarction. The optimum therapy for patients with myocardial infarction is being evaluated.

The first successful transplantation of a human heart into another human being was performed in South Africa by Christian Barnard in 1967. Transplantation was at first reserved for critically ill patients not likely to survive for long. However, a series of advances, primarily in the posttransplant management of patients, has led to a dramatic increase in survival after transplantation and to a tendency to carry out the procedure on patients with severe heart failure much earlier in the course of the disease. As a result, the number of transplantations performed worldwide increased from 3,000 in 1986 to more than 6,800 by January 1988. The five-year actuarial survival worldwide exceeded 70 percent and was more than 80 percent for some subgroups. Moreover, more than 80 percent of survivors were able to return to their previous occupations or comparable levels of activity. The success of cardiac transplantation prompted Medicare, the primary federal means of payment for elderly U.S. citizens receiving health care, to fund heart transplantations. It did so, however, at only a few locations, selected on the basis of results and experience, thus linking reimbursement with some measure of quality. Although not all heart transplantations are covered by Medicare, many insurance plans have indicated an intent to employ Medicare criteria in deciding which institutions will be paid for the procedure.

That some patients suffer from an abnormally slow heartbeat has been known for some time. Current treatment for many of them (perhaps too many) is provided by an artificial pacemaker. The first pacemaker was implanted in 1959, and now more than 200,000 pacemakers are implanted each year worldwide, approximately half of these in the United States. The pacemaker, which usually weighs about 40 grams, is connected to the heart by wires and is powered by lithium batteries that commonly last 7 to 10 years. At first pacemakers produced electrical pacing signals at a constant rate in order to treat

Stokes-Adams disease; more recent models can be programmed to respond to changing conditions in a variety of ways. A new device can electrically shock the heart out of an uncoordinated rhythm called ventricular fibrillation. This automatic implantable defibrillator, first used in 1982, appears to be helpful for patients who suffer from arrhythmias that are difficult to control.

Unlike the stomach or the limbs, for example, a person's heart cannot stop functioning for long or the person will die. This fact made operations on the heart difficult to contemplate during the nineteenth century, when great advances were being made in surgery on other organs. Some leading surgeons of the day flatly asserted that surgery on the heart would always be impossible. Nonetheless, early in the twentieth century, surgical treatment of valvular heart disease was attempted. From 1902 to 1928, 10 attempts were made to cure mitral stenosis (a narrowing of the valve leading to the main pumping chamber of the heart); 8 of the patients died. Because of the dismal outcomes, no one attempted another such operation until the mid-1940s. Starting in the 1950s, the availability of cardiac bypass in the form of an effective pump and oxygenator enabled surgeons to work on a still, "open" heart rather than on a beating organ. Valve replacements became relatively easy. Coronary artery bypass grafting (surgery to bypass blocked coronary arteries) is now a common means of treating coronary artery disease. Whereas at first surgeons bypassed only one or two obstructed vessels, now many more are commonly bypassed during a procedure.

Our ability to replace diseased valves has also greatly increased. Some patients suffering from abnormal heart rhythms can be helped by heart surgery designed to interrupt abnormal conduction pathways within the heart. Some centers are investigating a heterotopic prosthetic ventricle, a mechanical device designed to support a failing heart until a suitable transplant can be procured. Others have attempted to use an artificial heart for long-term support. Such a device would not be subject to the immunologic phenomena associated with transplantation and would obviate the need to locate a donor heart. However, problems with clots and hemolysis have thus far severely limited the attractiveness of this option.

Your Heart and Nutrition

Your Heart and Nutrition

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