HEART ATTACKS AND CORONARY ARTERY DISEASEDocument Transcript
HEART ATTACKS AND CORONARY ARTERY DISEASE LAWRENCE DECKELBAUM, M.D. disagreeable sensation in the breast, which seemsINTRODUCTION as if it would take their life away, if it were to increase or to continue; the moment they stand still, all this uneasiness vanishes.Coronary artery disease has probably affected hu-man beings throughout history, but it is only in the Although the relationship between angina pecto-last century or so that it has emerged as a leading ris and diseased coronary arteries was establishedcause of death. The first description of the symptoms just a few years later, it was not until the early 20thof coronary artery disease was written in 1768 by century that the medical profession gave widespreadWilliam Heberden, an English physician. Dr. Heber- recognition to coronary artery disease as a majorden coined the term “angina pectoris’’—from the cause of death. Such recognition may have been slowLatin, angere, which means to strangle or distress, in coming because the disease was not widely prev-and pectoris, “of the chest’’—and his classic descrip- alent until around the middle of the 19th century.tion still holds true today With the advent of improved sanitation, immuniza- tion, and other advances in public health, the death There is a disorder of the breast, marked with toll from infectious diseases—previously the leading strong and peculiar symptoms considerable for cause of death—dropped. In industrialized nations, the kind of danger belonging to it, and not ex- these advances in public health coincided with life- tremely rare, of which I do not recollect any men- style changes, such as adoption of a diet high in meat tion among medical authors. The seat of it, and and other fatty foods, an increase in cigarette smok- sense of strangling and anxiety, with which it is ing, and a more sedentary life-style. It was at this time attended, may make it not improperly be called that the death rate from heart attacks began to soar. Angina pectoris. (See Chapter 3.) Those, who are afflicted with it, are seized while According to statistics compiled by the Centers for they are walking and more particularly when they Disease Control, almost one in two Americans dies walk soon after eating, with a painful and most of cardiovascular disease. The total annual toll is 133
MAJOR CARDIOVASCULAR DISORDERS more than 975,000; of these, about 500,000 die of Although the bodys entire volume of blood passes heart attacks. The large majority of heart attacks re- through the heart’s chambers approximately every sults from coronary artery disease, a condition that 60 seconds, only about 5 percent of the total amount afflicts about 5 million Americans. of oxygenated blood is available for the heart’s own Of course, mortality statistics are only part of the energy needs. The coronary arteries (which are 3 to story-coronary artery disease also affects life-style, 5 millimeters or 1/8 to 1/5 of an inch in diameter) are productivity, and the economy. According to 1991 the sole conduits for this supply. Because heart mus- figures compiled by the American Heart Association cle (myocardium) extracts oxygen from arterial blood and the National Center for Health Statistics, about with maximum efficiency, any increase in the heart’s 6 million Americans have a history of a heart attack, workload requires an increase in the blood supply. angina, or both. Although the likelihood of a heart When there is an imbalance between the available attack increases with age, a large number of supply of blood (oxygen) and demand for blood (ox- Americans—mostly men—are struck down during ygen), the heart muscle becomes oxygen-deprived, a their most productive years. About 45 percent of condition known as myocardial ischemia. Without heart attacks occur before the age of 65, with 5 per- adequate blood flow to the heart muscle, the heart cent before age 40. The American Heart Association itself is unable to function properly. puts the total annual cost of cardiovascular disease at $94.5 billion, a figure that includes both direct med- ical costs and estimated lost productivity resulting from disability. Fortunately, the number of deaths from coronary artery disease—while still unacceptably high—has OXYGEN DEPRAVATION (ISCHEMIA) been steadily declining since the late 1950s. In 1950, the age-adjusted death rate from heart attacks was For the majority of people suffering from coronary 226 per 100,000 Americans. By 1986, this had artery disease, the supply of oxygenated blood is re- dropped by nearly half to 129 per 100,000. For ex- duced due to a progressive narrowing of the open ample, the five-year survival rate of patients with an- channels (the interior lumens) of the coronary arter- gina improved from 75 percent in the years 1950 to ies. This is due to atherosclerosis, a disease in which 1970, to 87 percent during 1970 to 1975. Much of this scattered lesions, known as atherosclerotic, plaques improvement is undoubtedly the result of improved or atheromas, appear on the inner wall of the coro- medical care. But altered life-style factors such as nary artery. See Figure 11.1, a series of illustrations smoking cessation and a reduction in fat consump- showing how an artery becomes blocked. (The word tion are also believed to lower the risk of premature atheroma comes from the Greek for porridge, be- death from a heart attack. cause atheromas contain a porridgelike mixture of cholesterol, fat, and fibrous or starlike tissue.) The first signs of atherosclerosis can appear at an early age. A significant proportion of males in their teens and early 20s may already have fatty streaks ANATOMY OF THE HEART and other evidence of the disease on the walls of their coronary arteries-as was first demonstrated by au- topsies conducted on young American soldiers killed The normal human heart has two major coronary during the Korean War. The buildup of athero- arteries, so named because, together with their sclerotic plaque is a gradual process, however, and branches, they surround the heart like a crown (or it may take upward of 20 years or more from the first corona). From its branch off the aorta, the left main appearance of fatty streaks before the coronary ar- coronary artery quickly divides into two vessels: the teries are blocked enough to produce symptoms such left anterior descending artery and the circumflex ar- as angina or shortness of breath. Symptoms usually tery. Another vessel, the right coronary artery, comes do not occur until the coronary artery has been nar- off the aorta and supplies blood to the right and bot- rowed by about 50 to 70 percent. Even with signifi- tom parts of the heart. The three vessels supply all cantly clogged coronary arteries causing ischemia, the oxygenated blood necessary to keep the hearts however, many people do not experience symptoms. muscle and electrical conduction system functioning This is referred to as silent ischemia. and viable. (See Chapter 1.) The exact causes of buildup of atherosclerotic
HEART ATTACKS AND CORONARY ARTERY DISEASE 1948 to the present day) has enabled us to identify which risk factors increase the likelihood that some- one will develop atherosclerosis. These risk factors include some that are controllable, such as smoking, hypertension, and elevated blood cholesterol, as well as age, gender, family history, and other factors that are beyond our control. (See Chapter 3.) In addition to atherosclerotic plaque buildup, spasms of the muscles that encircle the coronary ar- teries can also interrupt the coronary blood supply. Normal artery In 85 percent of people who have coronary artery spasms, atherosclerosis is also present. In about 10 to 15 percent of people with typical anginal chest pains, spasms may be the sole cause of the oxygen deprivation (ischemia) and resulting pain. Some people who experience angina may have normal coronary arteries. The angina some of these people experience may be caused by a constriction or narrowing of the aortic valve. In others—who may have no evidence of coronary artery spasm, heart valve disease, or left ventricular heart muscle Artery with plaque buildup obstructing most of the interior abnormality-there is no clear reason for the angina. channel (lumen) These people generally have an excellent overall prognosis. An inability to deliver adequate oxygen during rest or periods of increased demand can result in ischemia manifested by angina and other symptoms. Factors affecting the heart muscles’ demand for blood include blood pressure, heart rate, and the size of the left ventricle. A sizable percentage of people suffer from chron- ically high blood pressure. In addition, blood pres- Cross section of an artery with a plaque sure temporarily rises during exercise or periods of stress. (See Chapter 12.) The heart rate is increased by exertion, fever, stress, and an overactive thyroid. Enlargement of the main pumping chamber—the left ventricle—is commonly the result of hypertension or certain heart valve disorders. All of these conditions result in increased work for the heart and the need for more oxygen. If this cannot be supplied, symp- toms may occur. Eventually, a clot (thrombus) can form, completely blocking the lumenFigure 11.1How a normal artery may become blocked by fatty plaque, SYMPTOMSplaque are not understood, nor is it possible to pin-point how they begin or what their course will be. The primary symptom of coronary artery disease isHowever, evidence based on a number of long-term chest pain or angina, which is not itself a disease butstudies (such as the Framingham Heart Study, which a set of symptoms closely corresponding to Heber-has examined the health of several thousand men and den’s original description. A person suffering fromwomen in the Boston suburb of Framingham from angina may clutch a fist to the chest while describing 135
MAJOR CARDIOVASCULAR DISORDERS of the heart. During cold weather, angina may also be more frequent because vessels may go into spasm, increasing the work of the heart while simultaneously decreasing the blood supply to the heart. In general, anginal symptoms usually fade and disappear when the person ceases the particular activity that pro- voked them. Ischemia may occasionally occur without symp- toms of angina or other discomfort, so-called “silent ischemia.” Some patients may experience only silent episodes of ischemia, whereas others have episodes with and without angina. The potential danger of si- lent ischemia is that someone may not be aware of the reduced blood flow to the heart muscle and might, therefore, be less likely to cease the activity precipi- tating it. The diagnosis, significance, and treatment of silent ischemia are areas of active research. Figure 11.2 DIAGNOSIS The shaded areas show locations for angina. It occurs most frequently or classically in the center of the chest (most heavily shaded area), but it may also radiate to the whole chest, neck, jaw, Angina is a clinical diagnosis; however, diagnosing and down the arm, particularly on the left side. Angina can also coronary artery disease purely on the basis of symp- occur in these places without occurring in the center of the chest. toms may be difficult. The discomfort of angina is not always experienced in the same way, and a patients symptoms may be vague. Chest pain can also occur a feeling of discomfort or pain, often using such in a variety of other conditions that may exist alone words as “pressure” or “heaviness.” This pain is usu- or may accompany coronary artery disease. It is, ally located in the center of the chest but may radiate therefore, important for the physician to distinguish to or occur only in the neck, shoulder, arm, or lower between anginal pains and chest pain from other jaw, particularly on the left side. (See Figure 11.2.) sources. (See Table 11.1.) Anginal pain usualJy begins Brief sharp stabbing or sticking pains confined to a gradually and lasts for several minutes, generally fad- small area of the chest are rarely caused by angina. ing when the individual stops the activity that pre- For most people, these symptoms almost always cipitated the attack or takes a medication such as occur during or after physical activity and/or emo- nitroglycerin, which widens (dilates) the coronary ar- tional stress and are more likely to occur following a teries and increases blood supply to the heart muscle. meal or in cold weather. People who have what is Angina is probably not the cause of the chest dis- known as stable angina can often predict with rea- comfort if it lasts less than 5 seconds or more than sonable accuracy the amount of activity that precip- 20 minutes (provided the patient is not having a heart itates an attack-sometimes to the point of knowing attack), if the pain is sharp or “stabbing,” if it is pre- how many stairs they can climb before pain begins. cipitated by a sudden movement or deep breath, if it Typical activities that might bring on angina include is confined to a small area, if it is not relieved by rest walking up several flights of stairs, climbing a hill, or or cessation of physical activity (again, provided the other sudden vigorous activities, such as running for patient is not having a heart attack), or if the chest a bus or playing tennis. A change in anginal pattern, wall is tender to the touch. such as increased frequency of angina or the new The sources of chest pain that mimic angina in- onset of angina at rest, is referred to as crescendo or clude esophageal or stomach disorders (for example, unstable angina. reflux of stomach acid into the esophagus, resulting Angina may be more likely to occur following a in “heartburn”), pain due to obstruction of the bile meal, because blood pools in the stomach and the duct, inflammation of the cartilage of the chest wall, intestinal tract during digestion, increasing the work and arthritis of the bones in the neck.
HEART ATTACKS AND CORONARY ARTERY DISEASE :Table 11.1Identifying Causes of Chest Pain Causes Type of chest pain Causes Type of chest pain and other symptoms and other symptoms Blood clot in the Chest pain accompanied by Lack of oxygen Dull, heavy, constricting pain lung (pulmonary breathlessness, faintness, in the heart in the center of the chest that embolism) cough bringing up bloody (angina) can spread to throat and phlegm, blueness (cyanosis) upper jaw, back, and arms around the mouth. (mainly left arm). Pain appears when person is active and Broken rib Pain in or near the chest area disappears when activity stops that increases with pressure and person rests. Can be or movement; area around accompanied by difficult fracture may be swollen and breathing, sweating, nausea, bruised. and dizziness. Collapsed lung Usually sudden sharp chest Nerve infection Intense, knifelike pain in one (pneumothorax) pain on one side of the body, (shingles) in the area of the chest that accompanied by chest area precedes, by several days or breathlessness; may be less, a rash (groups of blisters discomfort rather than pain, on the skin—much like may include pain at the chicken pox—above the bottom of the neck and affected nerve); pain continues tightness across chest. through and after rash Heart attack Crushing pain in the center of appearance. the chest, accompanied by Pneumonia Respiratory illness, including difficult breathing, sweating, cough and fever, precedes nausea, or a feeling of other symptoms, including faintness. chest pain, shortness of Heartburn and Painful burning sensation in breath, chills, sweating, hiatus hernia the chest that becomes worse bloody or yellow phlegm, or when person bends forward delirium. or lies down; person may also Pulled muscle in Pain, stiffness, or tenderness experience belching and the chest area in the chest area as a result of regurgitation of acidic fluid. overstretching a muscle (for Infection of the Pain in the upper chest that instance, while working out); airways in the worsens when coughing; deep area may become swollen as a lungs (acute cough that brings up grayish result of internal bleeding. bronchitis) or yellowish phlegm from the lungs. Disorders of the heart can also result in anginalike Further complicating the difficulty of making a di-symptoms. These include an elevated pressure in the agnosis of coronary artery disease on the basis oflungs (pulmonary hypertension) or a blood clot in an symptoms alone is the existence of silent ischemia.artery supplying the lungs (pulmonary embolism), re- Some people—who may or may not also occasionallysulting in lack of oxygen delivery to the lung tissue. experience anginal discomfort—can show all the clin-Inflammation or infection of the tough outer sac that ical signs of an attack of angina and yet may not feelcovers the heart (acute pericarditis) can produce per- any discomfort at the time. This syndrome appearssistent chest pain, which usually comes on suddenly to be more common in persons with diabetes.and is aggravated by coughing or movement. The presence of chest discomfort in someone who 137
MAJOR CARDIOVASCULAR DISORDERS has several risk factors for heart disease strongly sug- the test, because a drop in blood pressure during gests to the physician that the patient has coronary exercise also implies that the extent of coronary ar- artery disease. However, accurate diagnosis of cor- tery disease may be severe. The exercise ECG can onary artery disease in these people (and those with correctly identify about 65 to 75 percent of people chest pain who do not fit the risk profile) may require with coronary artery disease. some of the following tests. Helter monitoring, or the ambulatory ECG, which is worn for 24 to 48 hours, may be a useful tool in diagnosing some cases of angina. ECG changes may be recorded during episodes of angina. Like other tests in cardiology, it may not be necessary in all cases. ELECTROCARDIOGRAPHY The electrocardiogram (ECG), a graphic record of the electric currents generated by the heart, is an essen- tial tool for the diagnosis of coronary artery disease. RADIOISOTOPE SCANS An ECG taken while a person is resting (a resting, or baseline, ECG) will not show evidence of lack of ox- Thallium-201 is an isotope that is used for diagnosing ygen in the heart muscle—unless the patient is having coronary artery disease. This radioactive substance an attack of angina at the time-but it can demon- is injected and passes through the bloodstream into strate the presence of a previous heart attack or other the heart muscle cells. The distribution of thallium is changes suggesting that the heart muscle may not be recorded with a gamma camera, and areas of heart receiving an adequate blood supply. muscle that are not getting sufficient oxygen show The baseline ECG can provide a considerably up as “cold spots” in which the blood flow did not more useful diagnosis if the patient experiences an- deliver thallium or the heart muscle cells did not take gina during testing. The test can then not only show it up. Combined with the exercise ECG, an exercise that inadequate oxygen is reaching the heart muscle, thallium test helps to correctly identify about 90 per- but also give an idea of which artery is blocked and cent of people with coronary obstructions. This test the extent of heart muscle that maybe at risk. also helps to locate the specific sites of lesions. Re- The exercise ECG—popularly known as an exer- cently, new radioisotope agents have become avail- cise stress or tolerance test—is another useful tool able that may replace thallium-201 in the future. (See for diagnosis. While being monitored, the patient en- Chapter 10.) gages in physical activity of progressive intensity, Another diagnostic tool, multigated acquisition usually on a treadmill, stationary bicycle, or stair- scan (MUGA), which uses the radioisotope techne- climbing device. Exercise is usually continued until tium, can also provide information on the size and the heart rate reaches 85 percent of a calculated so- contraction pattern of the left ventricle. Contraction called maximum level—about 220 minus the person’s abnormalities that are induced by exercise can indi- age (for a 60-year-old person, about 160 beats per cate coronary artery disease. Ischemic or infarcted minute], or until symptoms of fatigue or chest pain (dead, due to a heart attack) regions of the heart USU- or significant ECG changes are noted. ally contract abnormally. If coronary arteries are healthy, they dilate or open People who are unable to tolerate an exercise test up to supply the extra blood and oxygen necessary because of orthopedic problems or impaired leg cir- to sustain the extra heart muscle workload. If this culation (see Chapter 17) can be effectively tested occurs, the electrocardiogram shows few changes. If using thallium combined with a potent drug, di- the arteries are narrowed or go into spasm, however, pyridamole (Persantine). Dipyridamole causes the portions of the heart muscle do not get enough blood coronary arteries to dilate (as they should to satisfy and ECG changes will occur. the increased demand for oxygenated blood created If changes occur at low work levels after only a by exertion) and thus increases the blood flow. If few minutes and/or at a heart rate of only about 100 there are blockages in an artery, the increase of beats per minute, this suggests that coronary heart flow does not occur and a “cold spot” is imaged. disease may be fairly severe. It is also useful to mon- This test compares favorably with exercise thallium itor a patient’s blood pressure and heart rate during imaging.
HEART ATTACKS AND CORONARY ARTERY DISEASE nostic benefits exceed the potential risks given anyECHOCARDIOGRAPHY of the following situations: q A patient who is under medical treatment com-Portions of the heart can be seen using an ultrasound bined with life-style changes continues to suf-method called echocardiography. The echocardio- fer from incapacitating angina. Such people cangram is a useful diagnostic tool for determining im- usually be relieved of their pain by coronary by-paired function and increased thickness of the walls pass surgery or angioplasty, and coronary angio-of the left ventricle as well as for helping to rule out graphy is necessary to determine whether theirother cardiac problems such as valve disease. (See arteries are suitable for either procedure.Chapter 14.) As with the MUGA, abnormalities in q An electrocardiogram and other tests suggestventricular contraction (wall motion abnormalities) that a patient risks damage to a considerablecan be documented by the echocardiogram during portion of the heart muscle (for example, theexercise or pharmacologic stimulation. A diagnosis patient who has marked electrocardiogramof angina and/or coronary heart disease can usually [ECGI changes after only a few minutes of abe made without the use of this test, however. stress test). Certain severe anatomic subsets of coronary artery disease (as shown using cor- onary angiography) are better treated with cor- onary bypass surgery. Coronary angiography may sometimes be sug-CORONARY ANGIOGRAPHY q gested to evaluate the coronary anatomy and hence better advise a patient about his or herX-ray imaging of the coronary arteries can be per- prognosis or treatment options.formed in a cardiac catheterization laboratory. Here,with the patient under mild sedation, an opening ismade to a blood vessel in the groin or arm, and a thintube is threaded up through the vessel to the heart.A dye that shows up on X-ray is injected into thecoronary vessels to outline their lumen, and into theleft ventricle to assess its contraction. This sequence DETERMINING TREATMENTof events is captured on motion-picture X-rays (an-giograms). The choice of treatment depends on both the need to Coronary angiography provides the “gold stan- relieve symptoms and the need to identify those atdard” diagnosis of the extent and location of disease increased risk of death. For example, in a large studyin the coronary arteries. Angiography also gives a of patients with chronic stable angina who were un-clear indication of whether the left ventricle is func- dergoing treatment in Veterans Administration fa-tioning well. A stenotic or narrowed vessel can be cilities, it was shown that 35 percent of those whoidentified by an indentation or narrowing in the col- had obstructions of the left main coronary artery diedumn or channel of dye in the vessel due to the ob- within four years with medical treatment alone. Thisstructing plaque or clot. The severity of the stenosis compared with a four-year death rate of 27 percentcan be quantified by the percent of the narrowing of for patients who had obstructions of three vessels, athe dye channel. An occluded vessel can be identified 12 percent death rate for patients who had obstruc-because it contains little or no blood and hence shows tions of two vessels, and a 2 percent death rate forlittle or no dye beyond the blockage. patients with obstructions of one vessel. (Fortunately, People are sometimes fearful of this procedure be- obstructions of the left main coronary artery are notcause it does carry a small risk of mortality (0.1 per- too common.)cent) or adverse reactions such as heart attack or It is useful in deciding treatment to determine thestroke (less than 3 percent), but the potential life- specific type of angina that is present. People withsaving benefits of an accurate diagnosis may out- coronary artery disease may be affected by whatweigh by far the modest risk. Obviously, however, all seems to be either stable exertional angina or vaso-people with angina do not need catheterization. The spastic (for example, Prinzmetal’s) angina. (See box,cardiologist will usually consider whether the diag- “Complications of Angina.”)
MAJOR CARDIOVASCULAR DISORDERS cipitated the attack. In addition, medication generally Complications of Angina helps to reduce the frequency of the attacks or, often, eliminates them by decreasing the heart’s blood (ox- The medical problems that can arise from coronary ygen) requirements or by increasing blood (oxygen) artery disease are: supply. q Heart rhythm disorders (arrhythmias), which are People with vasospastic angina, which is caused disturbances in the heart’s electrical activity. In by arterial spasms, may often have a fixed blood ves- people with coronary artery disease, the sel narrowing, but of a kind or degree in which con- arrhythmias are likely to have been caused by striction of the blood vessel also plays an important damage to certain areas of the heart muscle through lack of oxygen (ischemia) or heart role in the onset of oxygen deprivation. Angina is less attack (infarction). Electrical instability is predictable in these people. They may experience probably the major cause of sudden death in days when there is little or no chest pain regardless people with coronary artery disease. When heart of the amount of physical activity or days when an- rhythm disorders are the major clinical manifestations of coronary artery disease, gina is sparked by even slight exertion. In fact, angina therapy focuses primarily on preventing frequently occurs even when the person is resting or arrhythmias using medical, electrical, or in asleep. Vasospastic angina usually responds to med- refractory cases, surgical therapy. (See ications that alleviate or prevent vessel spasms. Chapter 16.) • Unstable angina or angina which becomes progressively more severe regardless of treatment. A person with this kind of angina may find that the frequency and severity of chest pain increases, and attacks may occur during rest or may be provoked by less effort DRUG THERAPY than usual. This type of angina may also occur in people who previously have not had angina; the attacks increase in frequency and severity A variety of medications are used to treat angina. (See and may occur during rest or be precipitated by Chapter 23.) These medications work either by re- less and less physical activity each time. This ducing the oxygen demand of the heart, by helping angina is not well controlled by medication. increase the supply of blood, or by doing both. Often, q Angina that cannot be controlled. This unstable two or more medications will be prescribed together angina often serves as a forewarning of because they can complement each other’s actions impending heart attack. People who suffer from unstable angina should be hospitalized— and may reduce the necessary dose of any one drug, preferably in a coronary intensive care unit— thus minimizing side effects. and treated with bed rest and medication. The oldest and most frequently used coronary ar- Aspirin and the drug heparin, a blood thinner tery medications are the nitrates. Nitrates dilate veins, administered intravenously, have been shown to reduce the incidence of heart attacks in people causing blood to pool in the veins and thus reducing with unstable angina. Coronary angiography the amount of blood returning to the heart. This has (chest X-ray of dye-filled blood vessels) should the effect of decreasing the size of the left ventricle, be considered to determine the extent and reducing the work of the heart (lowering heart mus- location of any narrowing of the coronary arteries and to help decide whether angioplasty cle demand for oxygen), and lowering the blood pres- or bypass surgery should be performed. sure. Nitrates may also increase the supply of Heart attack. oxygenated blood by causing the coronary arteries to open more fully, thus improving blood flow. Ni- Sudden death. trates also relieve coronary artery spasm. They do not, however, appear to decrease the strength of the heart’s contraction. Nitrates are available in the form Stable exertional angina is caused by an imbalance of nitroglycerin tablets, long-acting tablets, topical between the coronary blood supply and demand re- ointments, and time-release medicated patches that sulting from a fixed or stable obstruction of one or attach to the skin. more of the coronary arteries. Oxygen deprivation During an attack of angina, nitroglycerin tablets usually occurs at about the same point during exer- are taken under the tongue (sublingually), where the tion, and people can generally predict the factors that medication is quickly absorbed into the bloodstream. provoke an attack. Pain can usually be alleviated with The medication begins to work within five minutes, medication and/or by stopping the activity that pre- and its beneficial effects last from 10 to 30 minutes.
HEART ATTACKS AND CORONARY ARTERY DISEASEBecause of its rapid effect and short duration of ac- blocking the channels through which calcium wouldtion, sublingual nitroglycerin is generally used for normally enter these cells. By helping to block smoothrelief of individual angina episodes rather than for muscle contraction which causes arteries to narrow,sustained treatment. the medication helps keep the vessels dilated, thereby Isosorbide dinitrate is a long-acting nitrate. It takes improving blood flow.3 to 15 minutes to take effect, and its benefits last The calcium antagonists commonly used in thefrom one to two hours when it is taken sublingually. United States are nifedipine (Procardia), nicardipineThe benefits of oral forms of isosorbide dinitrate last (Cardene), verapamil (Calan, Isoptin), and diltiazemfrom four to six hours, depending on the size of the (Cardizem). Although their clinical effects and them-dose; there is also a longer-acting sustained-release ical structures are different, they all work by reducingform. the ability of calcium to enter heart muscle and vas- Transdermal nitroglycerin disks are patches worn cular smooth muscle cells. As a result, they are ef-on the skin; the nitroglycerin is absorbed into the fective in treating coronary artery spasm andbloodstream to provide continuous delivery of med- increasing blood flow by dilating the arteries. Theication for up to 24 hours. However, it is generally heart’s workload is also decreased because the drugsrecommended that the patch be removed during lower blood pressure and decrease the strength ofsome part of each day to prevent the buildup of tol- the heart’s contractions.erance to the drug’s effects. Calcium channel blockers may often be prescribed as an addition to a regimen consisting of a beta blocker and a nitrate, particularly for people whoseBETA BLOCKERS anginal discomfort has persisted despite the use ofBeta blockers were first introduced in the early 1970s the latter medications. Verapamil and diltiazem haveand have become one of the most useful types of also been used to treat heart rhythm disorders. Cau-drugs to treat coronary artery disease (and effort- tion in the use of these drugs is necessary in peopleinduced angina in particular). Beta blockers work by with any significant degree of heart block (abnor-blocking or inhibiting certain receptors in the heart. mality of the heart’s normal rhythm electrical con- During exercise or emotional stress, adrenalinelike ductive system) or poor left ventricle function.products are released and normally stimulate thesereceptors (beta-adrenergic receptors) to transmit COMBINATION DRUG TREATMENTmessages to the heart to speed up and pump harder. Effective treatment for people with severe anginaBy blocking these beta receptors and reducing the often involves using a combination of drugs, mostheart’s workload (lowering heart rate and strength often a nitrate, a beta blocker, and a calcium channelof contraction), beta blockers effectively reduce the blocker. For people with less severe angina, there aredemand of the heart muscle for oxygen during phys- several options. Broadly speaking, beta blockers areical activity or excitement. This helps prevent oxygen often the treatment of choice for angina that is usuallydeprivation to areas of the heart muscle. Beta block- brought on by an increase in heart work or oxygeners also help to lower blood pressure, which further demand. For people with angina in which vesselreduces the work of the heart. spasms are likely to play a significant role, calcium The drugs may be used alone or in combination channel blockers may be the drugs of choice. Nitrateswith others that relieve angina; the effects of beta are generally used in conjunction with either drug.blockers are particularly complemented by nitrate Aspirin therapy is also being frequently recom-therapy. Beta blockers currently on the market in- mended for people with coronary artery disease. As-clude propranolol (Inderal), nadolol (Corgard), ti- pirin has an antiplatelet effect that reduces the riskmolol (Blocadren), pindolol (Visken), betaxolol of clot formation in a coronary artery. Platelets are a(Kerlone), metoprolol (Lopressor), atenolol (Tenor- type of blood cell. They are instrumental in clot for-min), acebutolol (Sectral), and penbutolol (Levatol). mation that can occur at the site of a plaque and further decrease blood flow through a coronary ar- tery, often resulting in a heart attack. Aspirin hasCALCIUM CHANNEL BLOCKERS been shown to be beneficial after a heart attack andCalcium plays an important role in the contraction of for reducing the risk of a heart attack in people whothe smooth muscle cells of both the heart and the suffer from unstable angina and possibly also in peo-arteries. Calcium blockers or antagonists work by ple who suffer from stable angina. 141
MAJOR CARDIOVASCULAR DISORDERS principal behind the coronary bypass operation is to ANGIOPLASTY AND SURGERY provide new conduits to bypass obstructed or nar- rowed sections of the coronary arteries. These new conduits can be fashioned from lengths of a vein re- Two options for interventional or surgical treatment moved from the leg (the saphenous vein) or from an of angina are currently available and widely used artery of the chest wall (the internal mammary ar- balloon angioplasty (also called percutaneous trans- tery). This procedure takes place in an operating Iuminal coronary angioplasty or PTCA) and coronary room, with the patient deeply anesthetized. His or her artery bypass surgery. heart is stopped, and blood is circulated through the Angioplasty involves inserting a thin tube (cathe- body by a pump outside of the body (a heart-lung ter) with a deflated balloon on its tip through an in- machine). cision into a blood vessel in the groin or the arm and Coronary artery bypass surgery has a relatively threading it through the major arteries until it low mortality rate (1 to 2 percent in people with good reaches the coronary arteries. The catheter is then heart muscle function), although there is also a 5 to positioned so that the balloon rests within the block- 10 percent risk of a heart attack during or immedi- age, at which point the physician inflates the balloon, ately after the operation. Coronary artery bypass sur- thereby flattening and cracking the plaque or other gery provides complete relief from anginal pain in obstruction against the vessel wall and also stretch- about 70 percent of people and partial relief in an- ing the vessel open with the pressure. When the bal- other 20 percent. The clearest indication for bypass loon is deflated and removed, the blocked vessel surgery, therefore, is for patients who continue to remains less obstructed. have incapacitating angina despite being on a good This procedure was first performed in humans in medical program. 1977. More than 200,000 Americans now undergo it There is evidence that coronary artery bypass sur- each year, with an overall initial success rate ap- gery improves the longevity of certain people—no- proaching 90 percent, according to the National tably, those with blockages of the left main coronary Heart, Lung, and Blood Institute’s registry figures for artery branch and those with disease in all three cor- 1985 and 1986. Approximately 30 percent of patients onary arteries and impaired function of the left ven- undergoing angioplasty experience a recurrence of tricle. There is little proof that surgery improves the artery narrowing (restenosis) within six months, al- survival rate of people with narrowing in one or two though they may benefit from repeat angioplasty. The arteries alone, but a major study showed that quality mortality rate is around 1 percent, with a 4 percent of life (symptoms) improved in patients in all cate- chance of complications that might require emer- gories. Because of improvements in operative tech- gency coronary artery bypass surgery. nique, coronary artery bypass surgery is now an Care in selection of patients is important to the option for elderly people, as well as for people suf- success of angioplasty. Ideally, the patient should fering from other diseases-such as diabetes have only one or two vessels obstructed (although mellitus-in conjunction with coronary artery dis- multivessel angioplasty is increasingly being used), ease. It is, however, an expensive operation with a and the obstructions should be in sections of the significant recovery period. (See Chapter 25 for a artery that can be reached easily by the catheter. im- more detailed discussion.) provements in technique, along with new develop- ments in the field, make angioplasty an increasingly effective method of treating coronary artery disease. However, angioplasty is not initially successful in some cases. Studies are under way to compare an- LIFESTYLE MODIFICATION gioplasty to medical therapy in patients with predom- inantly single vessel disease and to surgery in patients Life-style changes are an important part of any treat- with multiple vessel disease. (See Chapter 24 for fur- ment regimen for angina. Some changes may be use- ther details.) ful in reducing the frequency of attacks by identifying Coronary artery bypass surgery is one of the most and modifying the activities and situations that pre- common and successful major surgeries performed cipitate these attacks. Changes may be relatively mi- today. Although this operation was first performed nor, such as avoiding exertion after a heavy meal or as recently as 1967, about 320,000 bypass procedures using a golf cart instead of walking. Emotional upset are now done in the United States each year. The should be avoided as much as possible, and air con-
HEART ATTACKS AND CORONARY ARTERY DISEASEditioning maybe considered a necessity for patientswith coronary artery disease who live in hot, humidclimates. HEART ATTACKS Long-term changes that reduce known cardiovas-cular risk factors are also helpful, because they can A heart attack, known medically as acute rnyocardialhelp not only to prevent further damage to the ar- infarction or an acute MI, is a major and all too com-teries but also, in some instances, actually to reverse mon medical emergency. Each year, there are aboutthe damage. 1.5 million heart attacks in the United States, leading For smokers, smoking cessation is the first and to more than 500,000 deaths. Most of these deaths—most efficacious life-style modification that can be un- more than 300,000—are sudden, occurring before thedertaken. Studies have shown that if a person quits patient even reaches the hospital.smoking altogether, the risk of a heart attack returns The vast majority of heart attacks area direct resultwithin 3 to 5 years to a level similar to that of non- of coronary artery disease. A blood clot or muscularsmokers in the same age group. (See Chapter 6.) spasm in a narrowed coronary vessel may suddenly Changes’ in diet are also a vital part of reducing block it completely, triggering an infarction in thethe continued development and progression of ath- area of the heart muscle that is normally nourishederosclerosis. Reducing the total calories and the in- by that artery. (The myocardium is the muscular walltake of saturated fats and dietary cholesterol while of the heart. infarction is a term to describe the deathincreasing the intake of starches and high-fiber food of some of this vital tissue because it has been de-may significantly lower blood cholesterol levels. (See prived of blood and oxygen.)Chapter 5.) A myocardial infarction can be dangerous because Regular aerobic exercise has many possible ben- irreparable heart damage may develop within a shorteficial effects: controlling weight, lowering blood time after the muscle is deprived of oxygen. An in-cholesterol, improving cardiovascular tone, reducing farction that affects as little as 10 percent of thestress, and providing a general feeling of well-being. myocardium can cause death if it involves a criticalThe conditioning effect of exercise also increases a area such as the papillary muscle (the muscle sup-person’s ability to perform a greater amount of work porting the heart valve) or if it precipitates an irreg-with the use of less oxygen. (See Chapter 7.) ular rhythm or perforation of the heart wall. Still, Exercise need not be strenuous, but it is important heart attack patients often survive much larger in-that it be energetic enough to gradually raise the farctions, affecting up to 30–40 percent of the myo-heart rate and that it be performed regularly (a min- cardium, if a less critical area is involved.imum of three to five days a week). Brisk walking for The severity of the heart attack depends on several30 to 45 minutes is inexpensive, requires no skill, and factors, including:puts little burden on knees, back, or hips. Exercisesthat produce a sudden strain—such as lifting heavyweights—should be avoided or conducted under a The site of the coronary artery that is blocked.physician’s guidance. They have relatively little car- Blockages of the left main and the left anteriordiovascular benefit, and the sudden increase of blood descending arteries are usually more life- pressure that such activities produce may precipitate threatening than blockage of the right coronary an attack of angina. artery. Reducing stress can be a valuable adjunct to any Cardiac arrhythmias. Blockage of a coronary ar- life-style modification. While stress has been only ten- tery can cause a serious heartbeat irregularity uously linked to high blood pressure and coronary (arrhythmia) that may result in sudden death. artery disease, reduction of stress can benefit the For example, blockage may cause a malfunction body as a whole. It is important to realize that stress of the heart’s electrical impulse system, leading does not arise just from having a lot to do; rather, it to an inefficiently rapid beat (tachycardia) or an comes from feelings of being overwhelmed and un- ineffective fluttering of heart muscle (ventric- able to cope, from feelings of hostility and from an ular fibrillation). Ventricular fibrillation is fatal inability to relax or enjoy leisure time. Regularly set- unless blood flow is restored with cardiopul- ting aside time to pursue an enjoyable activity (such monary resuscitation and the normal heartbeat as listening to music), meditation, and in some cases, restored with drugs or electric shock therapy psychological counseling, can all help reduce stress. (defibrillation). Serious arrhythmias may also (See Chapter 8.) arise later, after the acute phase of a heart at-
MAJOR CARDIOVASCULAR DISORDERS tack, if certain areas of the ventricular wall have episode lasts for more than 10 or 15 minutes and it been damaged. (See Chapter 16.) is not relieved by up to three nitroglycerin tablets • Collateral circulation. When a key coronary ves- (given every few minutes), it is a sign that a heart sel slowly becomes blocked over a period of attack may be occurring. months or years, the heart muscle’s demand for Cold sweats are common just before or during a oxygen prompts other vessels and their heart attack. The person may be dizzy or weak or branches to widen and even extend into the may feel faint; loss of consciousness can also occur. oxygen-deprived area to provide an alternative The pulse may be rapid and shallow or irregular. Nau- blood source. In effect, a gradual natural cor- sea, vomiting, and other gastrointestinal symptoms onary bypass takes place. This is referred to as are common. A person having a heart attack also may “collateral” coronary blood flow, which can be be short of breath. He or she maybe weak, pale, and a saving grace if the original vessel becomes extremely anxious. (For information on how to help totally occluded. Collaterals are credited with victims of a heart attack and other cardiac emergen- saving many older heart attack patients. The cies, see box “What You Can Do” and Chapter 27.) sudden, fatal heart attacks that sometimes Prompt emergency care not only saves many lives strike younger men or women may be more but it also helps minimize the damage of a heart at- serious because the blockage occurs in a vessel tack. Many ambulances and other emergency vehi- serving an area for which collaterals have yet cles are now equipped with life-saving equipment. In to develop. fact, many are actually mobile coronary care units, and the emergency medical teams are trained in ad- ministering life-saving treatment even before the pa- tient reaches the emergency room. In most communities, emergency medical service (EMS) WARNING SIGNS AND SYMPTOMS workers, ambulance drivers, firemen, and others are now trained to stabilize heart attack patients before and while transporting them to the emergency room. Heart attacks vary in severity and in symptoms. The (See Chapter 27.) one clear rule is that whenever heart attack is sus- Even in the face of marked symptoms of a heart pected, the person must be taken to a hospital as attack, there is a natural tendency to wait and see if quickly as possible. About 60 percent of all heart at- the pain or discomfort in the chest is from heartburn tack deaths occur within the first hour. Yet, according or some other harmless ailment. But, if it is a heart to the American Heart Association, at least half of attack, irreversible damage may occur within hours people suffering a heart attack delay seeking help for if not minutes. Perhaps more important, some of the two or more hours. most potent new drugs that can prevent death of The initial pain of a heart attack is often intense— heart muscle work only if they are given within the a crushing feeling or pressure in the middle of the first four to six hours of the heart attack. Thereafter, chest. But in other cases it is much less severe; the they may be less beneficial. pain may be no more than an unusual dull, aching Preferably, treatment should be sought at a hos- sensation that persists. Or there may be a strong pital with a 24-hour-a-day emergency room that is squeezing sensation inside the center of the chest. continuously staffed by doctors. If the choice presents Some people experience burning feelings, while in itself, one should go to a hospital with an intensive some cases, they simply feel bloated. Sometimes, care unit (ICU) or, preferably, one with a specialized there is virtually no pain. (These are referred to as ICU called a coronary care unit (CCU). silent heart attacks.) When pain occurs, it most often is focused beneath the sternum (breastbone). Or it may spread out, en- compassing all of the chest, the shoulders and arms (the left arm more often than the right), and even the neck and the jaws. For some people, this chest pain IN THE EMERGENCY DEPARTMENT seems very much like, albeit more severe than, the angina pectoris that they had previously experienced. When you accompany a person with a suspected In unusual instances, there is little or no pain, al- heart attack to the emergency department, ask im- though there may be other symptoms. If an anginal mediately for a doctor or a nurse and clearly an-
HEART ATTACKS AND CORONARY ARTERY DISEASEnounce that a heart attack patient has arrived. After A defibrillator will be deployed at once if the heartan examination, the nurses and doctors can deter- is fibrillating. A jolt of electricity is passed throughmine whether it really is a heart attack or some other the heart, between paddle-shaped electrodes heldperhaps less serious problem. against the chest. This electric shock often interrupts Emergency department nurses and physicians arrhythmias and restores the heart to normal (sinus)often can diagnose a typical heart attack by looking rhythm. If the heart has stopped, doctors will com-at the patient. (They may see several heart attack vic- press the chest, up and down, trying to maintain thetims each day.) Even so, looks can be deceptive, and heart’s pumping action. (See Chapter 27.)a diagnosis must be confirmed by talking to and ex- Over the past decade, the most recent innovationamining the patient and by taking an electrocardi- in the treatment of heart attack patients has been theogram (ECG) and administering a series of blood use of clot-dissolving or thrombolytic agents, a tech-tests. nique called reperfusion therapy. Most heart attacks The heart may be beating too rapidly (tachycardia) result from the formation of a blood clot within aor too slowly (bradycardia). The blood pressure, too, coronary artery that is narrowed by atherosclerosismay be elevated, or more commonly it may be on the or spasm, and it is possible to restore blood flow tolow end of normal. The ECG typically shows irreg- the heart by dissolving this clot (thrombus).ularities, particularly changes in the Q waves, ST seg- Because the lack of blood and oxygen causes pro-ments, and/or T waves. (See Figure 11.1.) Doctors gressive death of myocardial cells, it is important tooften can deduce from the ECG which coronary ves- administer the thrombolytic agent as soon as possi-sel is afflicted. ble. In more than two-thirds of cases, if the throm- A blood specimen should be drawn quickly and bolytic agent is administered within 6 hours of thethen tested for the presence of enzymes that are se- onset of the heart attack, the blood clots can be dis-creted by heart muscle cells that may have been in- solved and the blood flow restored, thereby salvagingjured, a strong indication of muscle damage or death heart muscle. Studies have clearly shown that early(infarction). Treatment starts immediately, particu- administration of thrombolytic agents results in bet-larly if the patient’s heart has stopped or he or she ter survival and better heart function following myo-is unconscious. cardial infarction. 145
MAJOR CARDIOVASCULAR DISORDERS The earliest thrombolytic agents were streptoki- inside the aorta, the body’s largest artery which rises nase (Kabikinase, Streptase) and urokinase (Abbok- from the heart. The balloon can be inflated rhyth- inase). More recently, t-PA (tissue plasminogen mically from outside the body. This forces blood into activator) and anistreplase (Eminase) have been in- the aorta and forward through the circulatory sys- troduced for clinical use in the United States. TPA tem, thereby assisting the weakened heart. In es- (alteplase or Activase) is a genetically engineered sence, the balloon is an auxiliary pump that agent that contains a natural human substance that temporarily carries some of the load when the heart activates an enzyme that dissolves the blood clot. Al- is weakened by a heart attack. though the agent is most effective when given early, in selected patients, the myocardium can be salvaged when the thrombolytic agent is given later. These drugs have revolutionized the care of heart attack patients and have reduced the death rates by about 20 percent. HOW CORONARY CARE UNITS HELP In addition to thrombolytic agents, aspirin and heparin may also be administered. The drug heparin Much of the recent improvement in heart attack treat- is given intravenously and interferes with normal ment comes from specific new developments—better blood clotting. These drugs can prevent a clot in the ways to detect heart damage and improved drugs or artery from growing larger or from reforming after other treatments. Still, a major factor in decreased it has been dissolved by the thrombolytic agent. heart attack mortality is the development of total, in- Additional drugs are often administered early in tegrated care, with an emphasis on monitoring heart the course of a heart attack. Morphine may be in- function, that is provided through coronary care jected or infused through an intravenous line to re- units (CCUs). These are areas in the hospital reserved lieve pain. This old, powerful narcotic agent is for heart patients and are staffed by specially trained extremely effective and is still the standard for pain doctors, nurses, and technicians. CCU workers can relief. Oxygen may be given through a face mask or follow a patient’s status in minute detail, using so- nasal prongs to improve the oxygen content of the phisticated computerized electrocardiograms (ECGS) blood still flowing to the heart. Intravenous beta and other monitoring methods. The patient is at- blockers and nitroglycerin may also be administered tached on an ongoing basis to an ECG monitor that in an attempt to limit the size of the heart attack. sounds an alarm when an irregular heartbeat devel- Sometimes drugs used to treat or prevent irregular ops. Defibrillator and other life-saving equipment heart rhythms will also be given. (See Chapter 23 for are on hand and can be used within minutes if a prob- more information on cardiovascular drugs.) lem suddenly arises. The aim of all of these therapies is to restore blood When the patient’s heart and other vital organs flow, restore a regular heartbeat, and then give the are again functioning in a stable way, usually within damaged heart time to recover. For some people, a few days, he or she maybe moved out of the CCU however, these medical treatment methods are not into an ordinary hospital room. The hospital stay for effective and the blocked artery may fail to open. In a heart attack can vary from one to three weeks, de- some cases, further treatment, such as angioplasty or pending upon the severity and extent of heart dam- coronary bypass surgery, may be necessary. age and the occurrence of any complications. The An angiogram, an X-ray showing dye-filled blood heart begins to heal during the first several weeks vessels, can indicate where the blockage is located, after a heart attack by forming scar tissue to replace and balloon angioplasty may be used to open the the damaged or dead heart cells. Although scar tissue obstruction. In some patients who have extensive strengthens the injured part of the heart muscle, it blockage—sometimes in two or more vessels—an cannot contract like normal heart muscle. Therefore, emergency coronary artery bypass operation may be the remaining heart muscle must compensate by performed. Coronary artery bypass surgery can be working or contracting harder to pump blood. In ad- performed on an emergency basis, is relatively safe, dition to scar formation, collateral blood vessels (see and, in most cases, is quite effective. above) may develop to bring more blood to the sur- A variety of other procedures maybe deployed in rounding damaged but living heart cells in the border the CCU to assist heart attack victims, especially those regions of the myocardial infarction. who show signs of heart failure. In one, a balloonlike The presence and extent of the heart attack can be device (an intra-aortic balloon catheter) is inserted definitively diagnosed by serial electrocardiograms,
HEART ATTACKS AND CORONARY ARTERY DISEASEblood tests (that measure enzymes released from The total recovery from a heart attack usually takesdying heart cells), and possibly by an echocardi- two to three months. During this time, the patientogram or radionuclide scan to image how the various should try initially to reduce the strain on the heartregions of the heart muscle (for example, left ventri- by resting, and then to improve heart function bycle) are pumping. A severe or large heart attack can gradually increasing activities and starting routinebe complicated by: rupture of the heart wall; low exercise. The exact activity prescription for a heartblood pressure; fluid buildup (congestion) in the attack patient depends on the size and complicationslungs due to inability of the heart to pump adequate of the heart attack, the level of activity before theamounts of blood; blood clots in the heart or legs; heart attack, and how the heart responds to increasedirregular heart rhythms such as tachycardia or fi- activity.brillation; and recurrent chest pain, either due to Heart attack patients are often maintained onan inflamed heart sac (pericarditis) or recurrent treatment with aspirin and beta blockers, which haveangina. been shown to decrease the risk of subsequent heart In this era of thrombolytic therapy in which it is attacks, as well as treatment with other antianginalfrequently possible to successfully reopen a previ- drugs as needed. The goal of rehabilitation is to grad-ously occluded artery, it is important to evaluate pa- ually increase one’s activities to the point of resumingtients for their risk for another heart attack. (See box, a reasonable life-style. (See Chapter 28.)“Therapy After a Heart Attack.”) A successfully Initial avoidance of extreme stress or exercise andopened stenotic artery can reocclude with new clots extremes of hot and cold temperatures is importantin up to one-fourth of patients within days or months to minimize the risk of putting too much stress on thefollowing the initial heart attack. Therefore, patients heart or of precipitating angina. A physician can usu-frequently have an exercise stress test prior to hos- ally guide the resumption of activities based on thepital discharge to ascertain if they are at high risk for severity of the heart attack and data from an exerciseanother heart attack. Recurrent angina or a positive stress test. Most activities of daily living, includingstress test usually leads to catheterization and evalua- sexual activity, can usually be resumed within threetion for coronary artery angioplasty or bypass surgery. to six weeks after a heart attack. It will also be im- 147
IAJOR CARD1OVASCULAR DISORDERS portant in the rehabilitation period to decrease car- part, this is because there are about 25 percent fewer diac risk factors (see Chapter 3). heart attacks. There has also been a similar 25 percent Feelings of apxiety, anger, and depression are not reduction in fatalities from heart attacks. A significant uncommon during the acute and chronic phases of a part of this reduction in deaths is due to newer treat- heart attack. It is important, however, to realize that ments, careful observation and management of pa- most patients recover well from this life-threatening tients in CCUS, and improvement in other facets of event. heart attack care. Heart attack survivors require shorter hospital- izations than before. They also tend to be healthier —less disabled—after their heart attacks because ofTHE PAYOFF: SALVAGED LIVES improved treatment methods. Skillful coronary care limits the damage and disability. Most heart attack patients now can regain normal or near-normal life- The death rate from acute heart attack has dropped styles, and some actually enjoy better health than be- significantly over the last two or three decades. In fore their heart attacks.