Heart Injury and Its Consequences
The doctor said that you had a heart attack. This simple statement will be repeated over and over again in your mind in the months to follow. The important thing, however, is that you understand what this statement means. The terms that you hear will be confusing; heart attack, coronary occlusion, coronary thrombosis, and myocardial infarction are virtually synonymous. Angina pectoris is not synonymous with coronary occlusion. When a person has a heart attack, a portion of the heart muscle dies. In angina, there is a temporary insufficiency of blood flow to a part of the heart, and heart muscles death does not occur.
The heart is basically a pump that is composed primarily of muscle that expands and contracts to push blood through the body. This muscle, like all muscles in the body, must be fed with food and oxygen to function properly. If the muscle or part of the muscle is deprived of food and oxygen, serious consequences develop. Food and oxygen are carried to the heart muscle by blood flowing through the right and left coronary arteries. These are two blood vessels that arise from the aorta as soon as oxygen-rich blood has left the heart. In other words, the very first organ that the heart pumps blood to for nourishment is itself. Both coronary arteries supply a different part of the heart by way of their branches. If a main artery or one of its branches becomes obstructed for any reason, a portion of the heart muscle dies. This is a heart attack. The moment of blood vessel occlusion and heart muscles death is usually accompanied by profound symptoms such as severe chest pain, possibly, weakness, sweating, a sense of fear, and, in some instances, shortness of breath, palpitations, or fainting. If the rest of the heart can compensate during this initial phase of profound injury, the heart muscle will heal itself and the pump may again function in a near-normal fashion.
The common medical term used to describe this condition is myocardial infarction. Myo refers to muscle, cardial to heart, and infarction means an area of dead tissue that is caused by interruption in means an area of dead tissue that is caused by interruption in blood supply.. This point must be emphasized the fact that a portion of the heart muscle has died to help you understand and long term restrictions that this condition may impose upon you.
A great many people have the erroneous impression that a coronary thrombosis or coronary occlusion means only that an important blood vessel has been obstructed. That is correct, but it omits the consequences of heart muscle death. They have then heard that in time drugs will dissolve the blood clot that obstructs the vessel, and they then infer that they are back to normal again. Other people have the impression that, when a blood vessel is obstructed collateral blood vessels will supply the deprived tissue with an adequate blood flow. This again is a half-truth. Collateral circulation refers to the presence of small blood vessels which communicate with the large blood vessels. If a block occurs in a large vessel, these branches have the capacity to enlarge and shunt blood flow around the blockage to an area in need of blood. It is true that in time a blood clot may disappear, and it is also true that in time collateral blood vessels may supply with extra blood an area of the heart that lacks it. However, the diagnosis of myocardial infarction distinctly indicates that a portion of heart muscle has died before either of these two potential solutions have had time to become a reality.
In time, the area of dead muscle will be replaced by scar tissue. The time element is considered to be approximately six weeks. The reason that the patient activity should be greatly curtailed during the six-week period is that the heart should be given a chance to form an adequate scar. The function of the heart is to pump blood throughout the body. Working muscles of the body require a greater blood flow and, therefore, impose a greater load on the heart. A person at rest requires minimal blood flow to his body muscles and, therefore, minimal heart work. A distinct possibility in the person who does not rest after a myocardial infarction is that the area a dead muscle will soften and rupture before a scar has formed. The effect is the same as punching a hole in a gas tank. When the gasoline runs out, the engine will no longer run. In the case of the human being, he dies.
Restricted activity during this critical healing phase permits the formation of a tight, effective scar. Scar tissue is incapable of performing any work. Scar tissue cannot contract to make the heart a more effective pump. A good scar, however, will draw the living muscles as close together as possible so that they can function properly without the useless part. If the heart is overworked during this period, it will tend to enlarge and a loose, thin, bulging scar will form which will hamper the work to the adjacent muscles. This loose scar is called a ventricular aneurysm.
One of the potential early complications of the myocardial infarction is heart failure. This term means that the pump is unable to move an adequate amount of blood through the body. When one portion of the heart muscle suddenly dies, the rest of the heart must take on an additional burden. This is similar to one engine of a multiengine airplane suddenly quitting in flight. If the load is not too heavy and if the remaining engines are powerful enough, the plane will continue to be airborne; otherwise the plane will crash. If the pilot has sufficient time to act, he may be able to compensate for his loss of power by throwing cargo or fuel overboard to lighten his load. The burden on the heart muscle is eased by radically reducing the activity that the entire body undertakes. This is another reason for strict rest during the early phases of a heart attack. If the heart is unable to pump an adequate blood volume, the ensuing course of events results in an engorgement of blood in the vessels of the lungs. The increased back pressure eventually results in the water portion of the blood oozing into the air spaces of the lungs, which blocks normal gas exchange. The patient literally drowns in his own fluids. The clinical picture is called pulmonary edema, which is a form of heart failure. The patient experiences this chain of events as a rapidly increasing shortness of breath.
The blood pressure of the body is maintained by a certain quantity of blood flowing through blood vessels in a given period of time. When the heart is unable to pump an adequate amount of blood, the blood pressure in the entire body will fall and a state of shock will develop. The patient experiences this as a sensation of weakness, faintness, and possibly profuse perspiration. The physician recognizes this state by a low blood pressure and a weak pulse. If this state persists for a sufficient time, the brain and other vital organs will suffer from lack of blood and irreparable damage or death may occur.
The heart normally contracts 60 to 100 times a minute, propelling blood with each contraction. The stimulus for each contraction is a discharge from nervous tissue within the heart at the same rate. The origin of these stimuli is usually the sino-atrial node, which is known as the pacemaker of the heart. However, any portion of the heart has the potential capacity for initiating a nervous impulse that can result in contraction of the heart muscles. When a portion of heart muscles dies, the remaining muscles may become very irritable and multiple areas of discharge may compete with the pacemaker, resulting in a rapid or erratic heart beat. This rhythm may be a tachycardia or fibrillation. If the speed of contraction is not too fast or if the rhythm of contraction is not too erratic, the heart will still pump blood effectively. If, on the other hand the rate is too fast or the rhythm too irregular, the actual amount of blood pumped will greatly diminish and a shock-like picture will develop. The patient may experience these events as a palpitation or fluttering in his chest. The development of shock is accompanied by feelings of weakness, faintness or profuse sweating.
Physicians today are familiar with these events, and hospitals are equipped to combat many of these complicating factors. Therefore, the safest place for a person who has suffered a heart attack is in a hospital under close supervision of trained personnel. It is nostalgic to remember Grand-father heart attack as he remained in his comfortable bed at home, visited daily by his family doctor until it was felt safe for him to get out of bed. At that time, however, many of these serious complications were not known, and effective treatment for them was not available. Today doctor may very well recognise over the telephone that his patient has gone into shock the third day after his heart attack, but if the patient is at home it may be too late for the doctor to do anything effective about it by the time he reaches the bedside.
The current approach to the treatment of myocardial infarction is first to get the suffering patient to the hospital quickly. After a provisional diagnosis has been made, he is moved into a special area of the hospital called a Coronary Care Unit, which is staffed and equipped expressly for this type of illness. The patient is usually under the constant supervision of doctors, nurses, and electronic machinery, all of which are focusing their attention on detecting the very first sign of any complication. If complications do develop, treatment is much more effective if it is begun early.
The development of the concept of coronary care units is of recent origin. It is the result of increasing medical knowledge and in particular of increasing knowledge about the natural history of coronary artery disease. To achieve a proper frame of reference, it is of interest that Dr. Paul White reports that in 1910 the diagnosis of a heart attack or myocardial infarct was seldom made in a general hospital. His explanation is that, first, the disease itself was much less common than it is today, and, second, that doctor were not aware of the disease itself. In other words, medicine had not advanced to the point where it was commonly recognised that there was such a thing as a myocardial infarct, or what the symptoms of this illness were. By the 1920 the disease pattern was established as a distinct entity, and by, World War II large number of patients were being treated for this condition.
By the 1960 statistics revealed that about 60 percent of the deaths of person with atherosclerotic heart disease were sudden deaths. Furthermore about 70 percent of these deaths accurred during the first seven days of the illness. Just before this period, the first human being was successfully defibrillated by an electrical shock across the chest. This is a common cause of sudden death in persons with heart attacks.
Shortly after this, the technique of closed-chest cardiac massage was devised. By this is meant the application of pressure repeatedly over the chest of a person whose heart has stopped beating. With the proper application of chest compression, blood is forced into and out of the heart in a near normal fashion. The efficiency does not approach that of the normally beating heart, but enough blood can be induced to circulate to the vital organs of the body to postpone death. Formerly, if the heart stopped beating or fibrillated, death of the brain occurred in four or five minutes as mentioned above. Other forms of heart stoppage cannot be treated by defibrillation, but sometimes drugs or other forms of treatment can be used to start the heart again if the patient can be kept alive until they have a chance to take effect.