Common types of heart disease are as follows:-
A. Coronary Heart Disease
Coronary heart disease, the most common type of heart disease in most industrialized countries, is responsible for over 515,000 deaths in the United States yearly. It is caused by atherosclerosis, the buildup of fatty material called plaque on the inside of the coronary arteries. Over the course of many years, this plaque narrows the arteries so that less blood can flow through them and less oxygen reaches the heart muscle.
The most common symptom of coronary heart disease is angina pectoris, a squeezing chest pain that may radiate to the neck, jaw, back, and left arm. Angina pectoris is a signal that blood flow to the heart muscle falls short when extra work is required from the heart muscle. An attack of angina is typically triggered by exercise or other physical exertion, or by strong emotions. Coronary heart disease can also lead to a heart attack, which usually develops when a blood clot forms at the site of a plaque and severely reduces or completely stops the flow of blood to a part of the heart. In a heart attack, also known as myocardial infarction, part of the heart muscle dies because it is deprived of oxygen. This oxygen deprivation also causes the crushing chest pain characteristic of a heart attack. Other symptoms of a heart attack include nausea, vomiting, and profuse sweating. About one-third of heart attacks are fatal, but patients who seek immediate medical attention when symptoms of a heart attack develop have a good chance of surviving.
One of the primary risk factors for coronary heart disease is the presence of a high level of a fatty substance called cholesterol in the bloodstream. High blood cholesterol is typically the result of a diet that is high in cholesterol and saturated fat, although some genetic disorders also cause the problem. Other risk factors include smoking, high blood pressure, diabetes mellitus, obesity, and a sedentary lifestyle. Coronary heart disease was once thought to affect primarily men, but this is not the case. The disease affects an equal number of men and women, although women tend to develop the disease later in life than men do.
Coronary heart disease cannot be cured, but it can often be controlled with a combination of lifestyle changes and medications. Patients with coronary heart disease are encouraged to quit smoking, exercise regularly, and eat a low-fat diet. Doctors may prescribe a drug such as lovastatin, simvastatin, or pravastatin to help lower blood cholesterol. A wide variety of medications can help relieve angina, including nitroglycerin, beta blockers, and calcium channel blockers. Doctors may recommend that some patients take a daily dose of aspirin, which helps prevent heart attacks by interfering with platelets, tiny blood cells that play a critical role in blood clotting.
In some patients, lifestyle changes and medication may not be sufficient to control angina. These patients may undergo coronary artery bypass surgery or percutaneous transluminal coronary angioplasty (PTCA) to help relieve their symptoms. In bypass surgery, a length of blood vessel is removed from elsewhere in the patient’s body—usually a vein from the leg or an artery from the wrist. The surgeon sews one end to the aorta and the other end to the coronary artery, creating a conduit for blood to flow that bypasses the narrowed segment. Surgeons today commonly use an artery from the inside of the chest wall because bypasses made from this artery are very durable. In PTCA, commonly referred to as balloon angioplasty, a deflated balloon is threaded through the patient’s coronary arteries to the site of a blockage. The balloon is then inflated, crushing the plaque and restoring the normal flow of blood through the artery.
B. Congenital Defects
Each year thousands of babies worldwide are born with a congenital heart defect. A wide variety of heart malformations can occur. One of the most common abnormalities is a septal defect, an opening between the right and left atrium or between the right and left ventricle. In other infants, the ductus arteriosus, a fetal blood vessel that usually closes soon after birth, remains open. In babies with these abnormalities, some of the oxygen-rich blood returning from the lungs is pumped to the lungs again, placing extra strain on the right ventricle and on the blood vessels leading to and from the lung. Sometimes a portion of the aorta is abnormally narrow and unable to carry sufficient blood to the body. This condition, called coarctation of the aorta, places extra strain on the left ventricle because it must work harder to pump blood beyond the narrow portion of the aorta. With the heart pumping harder, high blood pressure often develops in the upper body and may cause a blood vessel in the brain to burst, a complication that is often fatal.
An infant may be born with several different heart defects, as in the condition known as tetralogy of Fallot. In this condition, a combination of four different heart malformations allows mixing of oxygenated and deoxygenated blood pumped by the heart. Infants with tetralogy of Fallot are often known as "blue babies" because of the characteristic bluish tinge of their skin, a condition caused by lack of oxygen.
In many cases, the cause of a congenital heart defect is difficult to identify. Some defects may be due to genetic factors, while others may be the result of viral infections or exposure to certain chemicals during the early part of the mother’s pregnancy. Regardless of the cause, most congenital malformations of the heart can be treated successfully with surgery, sometimes performed within a few weeks or months of birth. For example, a septal defect can be repaired with a patch made from pericardium or synthetic fabric that is sewn over the hole. An open ductus arteriosus is cut, and the pulmonary artery and aorta are stitched closed. To correct coarctation of the aorta, a surgeon snips out the narrowed portion of the vessel and sews the normal ends together, or sews in a tube of fabric to connect the ends. Surgery for tetralogy of Fallot involves procedures to correct each part of the defect. Success rates for many of these operations are well above 90 percent, and with treatment most children with congenital heart defects live healthy, normal lives.
C. Heart valve malfunction
Malfunction of one of the four valves within the heart can cause problems that affect the entire circulatory system. A leaky valve does not close all the way, allowing some blood to flow backward as the heart contracts. This backward flow decreases the amount of oxygen the heart can deliver to the tissues with each beat. A stenotic valve, which is stiff and does not open fully, requires the heart to pump with increased force to propel blood through the narrowed opening. Over time, either of these problems can lead to damage of the overworked heart muscle.
Some people are born with malformed valves. Such congenital malformations may require treatment soon after birth, or they may not cause problems until a person reaches adulthood. A heart valve may also become damaged during life, due to infection, connective tissue disorders such as Marfan syndrome, hypertension, heart attack, or simply aging.
Some people are born with malformed valves. Such congenital malformations may require treatment soon after birth, or they may not cause problems until a person reaches adulthood. A heart valve may also become damaged during life, due to infection, connective tissue disorders such as Marfan syndrome, hypertension, heart attack, or simply aging.
A well-known, but poorly understood, type of valve malfunction is mitral valve prolapse. In this condition, the leaflets of the mitral valve fail to close properly and bulge backward like a parachute into the left atrium. Mitral valve prolapse is the most common type of valve abnormality, affecting 5 to 10 percent of the United States population, the majority of them women. In most cases, mitral valve prolapse does not cause any problems, but in a few cases the valve’s failure to close properly allows blood to leak backwards through the valve.
Another common cause of valve damage is rheumatic fever, a complication that sometimes develops after an infection with common bacteria known as streptococci. Most common in children, the illness is characterized by inflammation and pain in the joints. Connective tissue elsewhere in the body, including in the heart, heart valves, and pericardium, may also become inflamed. This inflammation can result in damage to the heart, most commonly one of the heart valves, that remains after the other symptoms of rheumatic fever have gone away.
Valve abnormalities are often detected when a health-care professional listens to the heart with a stethoscope. Abnormal valves cause extra sounds in addition to the normal sequence of two heart sounds during each heartbeat. These extra heart sounds are often known as heart murmurs, and not all of them are dangerous. In some cases, a test called echocardiography may be necessary to evaluate an abnormal valve. This test uses ultrasound waves to produce images of the inside of the heart, enabling doctors to see the shape and movement of the valves as the heart pumps.
Another common cause of valve damage is rheumatic fever, a complication that sometimes develops after an infection with common bacteria known as streptococci. Most common in children, the illness is characterized by inflammation and pain in the joints. Connective tissue elsewhere in the body, including in the heart, heart valves, and pericardium, may also become inflamed. This inflammation can result in damage to the heart, most commonly one of the heart valves, that remains after the other symptoms of rheumatic fever have gone away.
Valve abnormalities are often detected when a health-care professional listens to the heart with a stethoscope. Abnormal valves cause extra sounds in addition to the normal sequence of two heart sounds during each heartbeat. These extra heart sounds are often known as heart murmurs, and not all of them are dangerous. In some cases, a test called echocardiography may be necessary to evaluate an abnormal valve. This test uses ultrasound waves to produce images of the inside of the heart, enabling doctors to see the shape and movement of the valves as the heart pumps.
Damaged or malformed valves can sometimes be surgically repaired. More severe valve damage may require replacement with a prosthetic valve. Some prosthetic valves are made from pig or cow valve tissue, while others are mechanical valves made from silicone and other synthetic materials.
D. Arrhythmias
Arrhythmias, or abnormal heart rhythms, arise from problems with the electrical conduction system of the heart. Arrhythmias can occur in either the atria or the ventricles. In general, ventricular arrhythmias are more serious than atrial arrhythmias because ventricular arrhythmias are more likely to affect the heart’s ability to pump blood to the body.
Some people have minor arrhythmias that persist for long periods and are not dangerous—in fact, they are simply heartbeats that are normal for that particular person’s heart. A temporary arrhythmia can be caused by alcohol, caffeine, or simply not getting a good night’s sleep. Often, damage to the heart muscle results in a tendency to develop arrhythmias. This heart muscle damage is frequently the result of a heart attack, but can also develop for other reasons, such as after an infection or as part of a congenital defect.
Some people have minor arrhythmias that persist for long periods and are not dangerous—in fact, they are simply heartbeats that are normal for that particular person’s heart. A temporary arrhythmia can be caused by alcohol, caffeine, or simply not getting a good night’s sleep. Often, damage to the heart muscle results in a tendency to develop arrhythmias. This heart muscle damage is frequently the result of a heart attack, but can also develop for other reasons, such as after an infection or as part of a congenital defect.
Arrhythmias may involve either abnormally slow or abnormally fast rhythms. An abnormally slow rhythm sometimes results from slower firing of impulses from the SA node itself, a condition known as sinus bradycardia. An abnormally slow heartbeat may also be due to heart block, which arises when some or all of the impulses generated by the SA node fail to be transmitted to the ventricles. Even if impulses from the atria are blocked, the ventricles continue to contract because fibers in the ventricles can generate their own rhythm. However, the rhythm they generate is slow, often only about 40 beats per minute. An abnormally slow heartbeat is dangerous if the heart does not pump enough blood to supply the brain and the rest of the body with oxygen. In this case, episodes of dizziness, lightheadedness, or fainting may occur. Episodes of fainting caused by heart block are known as Stokes-Adams attacks.
Some types of abnormally fast heart rhythms—such as atrial tachycardia, an increased rate of atrial contraction—are usually not dangerous. Atrial fibrillation, in which the atria contract in a rapid, uncoordinated manner, may reduce the pumping efficiency of the heart. In a person with an otherwise healthy heart, this may not be dangerous, but in a person with other heart disease the reduced pumping efficiency may lead to heart failure or stroke.
Some types of abnormally fast heart rhythms—such as atrial tachycardia, an increased rate of atrial contraction—are usually not dangerous. Atrial fibrillation, in which the atria contract in a rapid, uncoordinated manner, may reduce the pumping efficiency of the heart. In a person with an otherwise healthy heart, this may not be dangerous, but in a person with other heart disease the reduced pumping efficiency may lead to heart failure or stroke.
By far the most dangerous type of rapid arrhythmia is ventricular fibrillation, in which ventricular contractions are rapid and chaotic. Fibrillation prevents the ventricles from pumping blood efficiently, and can lead to death within minutes. Ventricular fibrillation can be reversed with an electrical defibrillator, a device that delivers a shock to the heart. The shock briefly stops the heart from beating, and when the heartbeat starts again the SA node is usually able to resume a normal beat.
Most often, arrhythmias can be diagnosed with the use of an ECG. Some arrhythmias do not require treatment. Others may be controlled with medications such as digitalis, propanolol, or disopyramide. Patients with heart block or several other types of arrhythmias may have an artificial pacemaker implanted in their chest. This small, battery-powered electronic device delivers regular electrical impulses to the heart through wires attached to different parts of the heart muscle. Another type of implantable device, a miniature defibrillator, is used in some patients at risk for serious ventricular arrhythmias. This device works much like the larger defibrillator used by paramedics and in the emergency room, delivering an electric shock to reset the heart when an abnormal rhythm is detected.
E. Myocardial inferaction (Heart attack)
Myocardial inferaction is the death of a section of the myocardium, the muscle of the heart, caused by an interruption of blood flow to the area. A heart attack results from obstruction of the coronary arteries. The most common cause is a blood clot (thrombus) that lodges in an area of a coronary artery thickened with cholesterol-containing plaque due to atherosclerosis.
Factors that contribute to the risk of atherosclerosis include high blood pressure (hypertension), diabetes mellitus, increased blood levels of low-density lipoprotein (LDL) cholesterol, smoking, and a family history of the disease. Particularly vulnerable to atherosclerosis are middle-aged men and individuals with the hereditary disease hypercholesterolemia.
Factors that contribute to the risk of atherosclerosis include high blood pressure (hypertension), diabetes mellitus, increased blood levels of low-density lipoprotein (LDL) cholesterol, smoking, and a family history of the disease. Particularly vulnerable to atherosclerosis are middle-aged men and individuals with the hereditary disease hypercholesterolemia.
Typically, a person experiencing a heart attack has severe chest pain, described as crushing, squeezing, or heavy, that is unremitting for 30 to 60 minutes and sometimes is experienced for longer periods. It often radiates to the arms, neck, and back. The pain is similar to that of angina pectoris, but it is of longer duration. Other common symptoms include shortness of breath; sweating; nausea; rapid heartbeat, often complicated by one or more arrhythmias (irregular heartbeats); and reduced blood pressure. The intensity of the symptoms depends on the size of the area of muscle affected by the heart attack. A small percentage of individuals do not experience pain; in these cases heart attack may be diagnosed from a routine electrocardiogram (ECG).
The focus of treatment is to limit the size of the area of tissue lost from lack of blood (infarct) and to prevent and treat complications, such as arrhythmia. Thus, the sooner the heart rate can be monitored by an ECG and the more promptly the arrhythmia is reversed by defibrillation with either antiarrhythmic drugs or electrical shock, the greater the chance of survival. Pain is treated with analgesics such as morphine, and rest and sedation are required. Other drugs that may be administered include beta-adrenergic-blocking drugs (beta-blockers) to relax the heart muscle, anticoagulants (e.g., heparin) to prevent clotting, fibrinolytic drugs to dissolve existing clots, and nitroglycerin to improve blood flow to the heart. Coronary thrombolysis therapy is widely used; it involves the administration of drugs such as streptokinase or tissue plasminogen activator (tPA) to prevent further blood clots from forming. Angioplasty or coronary artery bypass surgery are additional measures for patients requiring further treatment. The prognosis for patients who survive a heart attack is generally favourable, depending on the degree of injury to the heart.
E. Other Forms of Heart Disease
In addition to the relatively common heart diseases described above, a wide variety of other diseases can also affect the heart. These include tumors, heart damage from other diseases such as syphilis and tuberculosis, and inflammation of the heart muscle, pericardium, or endocardium.
Myocarditis, or inflammation of the heart muscle, was commonly caused by rheumatic fever in the past. Today, many cases are due to a viral infection or their cause cannot be identified. Sometimes myocarditis simply goes away on its own. In a minority of patients, who often suffer repeated episodes of inflammation, myocarditis leads to permanent damage of the heart muscle, reducing the heart’s ability to pump blood and making it prone to developing abnormal rhythms.
Cardiomyopathy encompasses any condition that damages and weakens the heart muscle. Scientists believe that viral infections cause many cases of cardiomyopathy. Other causes include vitamin B deficiency, rheumatic fever, underactivity of the thyroid gland, and a genetic disease called hemochromatosis in which iron builds up in the heart muscle cells. Some types of cardiomyopathy can be controlled with medication, but others lead to progressive weakening of the heart muscle and sometimes result in heart failure.
Myocarditis, or inflammation of the heart muscle, was commonly caused by rheumatic fever in the past. Today, many cases are due to a viral infection or their cause cannot be identified. Sometimes myocarditis simply goes away on its own. In a minority of patients, who often suffer repeated episodes of inflammation, myocarditis leads to permanent damage of the heart muscle, reducing the heart’s ability to pump blood and making it prone to developing abnormal rhythms.
Cardiomyopathy encompasses any condition that damages and weakens the heart muscle. Scientists believe that viral infections cause many cases of cardiomyopathy. Other causes include vitamin B deficiency, rheumatic fever, underactivity of the thyroid gland, and a genetic disease called hemochromatosis in which iron builds up in the heart muscle cells. Some types of cardiomyopathy can be controlled with medication, but others lead to progressive weakening of the heart muscle and sometimes result in heart failure.
In pericarditis, the most common disorder of the pericardium, the saclike membrane around the heart becomes inflamed. Pericarditis is most commonly caused by a viral infection, but may also be due to arthritis or an autoimmune disease such as systemic lupus erythematosus. It may be a complication of late-stage kidney disease, lung cancer, or lymphoma; it may be a side effect of radiation therapy or certain drugs. Pericarditis sometimes goes away without treatment, but it is often treated with anti-inflammatory drugs. It usually causes no permanent damage to the heart. If too much fluid builds up around the heart during an attack of pericarditis, the fluid may need to be drained with a long needle or in a surgical procedure. Patients who suffer repeated episodes of pericarditis may have the pericardium surgically removed.
Endocarditis is an infection of the inner lining of the heart, but damage from such an infection usually affects only the heart valves. Endocarditis often develops when bacteria from elsewhere in the body enter the bloodstream, settle on the flaps of one of the heart valves, and begin to grow there. The infection can be treated with antibiotics, but if untreated, endocarditis is often fatal. People with congenital heart defects, valve damage due to rheumatic fever, or other valve problems are at greatest risk for developing endocarditis. They often take antibiotics as a preventive measure before undergoing dental surgery or certain other types of surgery that can allow bacteria into the bloodstream. Intravenous drug users who share needles are another population at risk for endocarditis. People who use unclean needles, which allow bacteria into the bloodstream, frequently develop valve damage.
F. Heart Failure
The final stage in almost any type of heart disease is heart failure, also known as congestive heart failure, in which the heart muscle weakens and is unable to pump enough blood to the body. In the early stages of heart failure, the muscle may enlarge in an attempt to contract more vigorously, but after a time this enlargement of the muscle simply makes the heart inefficient and unable to deliver enough blood to the tissues. In response to this shortfall, the kidneys conserve water in an attempt to increase blood volume, and the heart is stimulated to pump harder. Eventually excess fluid seeps through the walls of tiny blood vessels and into the tissues. Fluid may collect in the lungs, making breathing difficult, especially when a patient is lying down at night. Many patients with heart failure must sleep propped up on pillows to be able to breathe. Fluid may also build up in the ankles, legs, or abdomen. In the later stages of heart failure, any type of physical activity becomes next to impossible.
Almost any condition that overworks or damages the heart muscle can eventually result in heart failure. The most common cause of heart failure is coronary heart disease. Heart failure may develop when the death of heart muscle in a heart attack leaves the heart with less strength to pump blood, or simply as a result of long-term oxygen deprivation due to narrowed coronary arteries. Hypertension or malfunctioning valves that force the heart to work harder over extended periods of time may also lead to heart failure. Viral or bacterial infections, alcohol abuse, and certain chemicals (including some lifesaving drugs used in cancer chemotherapy), can all damage the heart muscle and result in heart failure.
Despite its ominous name, heart failure can sometimes be reversed and can often be effectively treated for long periods with a combination of drugs. About 4.6 million people with heart failure are alive in the United States today. Medications such as digitalis are often prescribed to increase the heart’s pumping efficiency, while beta blockers may be used to decrease the heart’s workload. Drugs known as vasodilators relax the arteries and veins so that blood encounters less resistance as it flows. Diuretics stimulate the kidneys to excrete excess fluid.
A last resort in the treatment of heart failure is heart transplantation, in which a patient’s diseased heart is replaced with a healthy heart from a person who has died of other causes. Heart transplantation enables some patients with heart failure to lead active, healthy lives once again. However, a person who has received a heart transplant must take medications to suppress the immune system for the rest of his or her life in order to prevent rejection of the new heart. These drugs can have serious side effects, making a person more vulnerable to infections and certain types of cancer.
A last resort in the treatment of heart failure is heart transplantation, in which a patient’s diseased heart is replaced with a healthy heart from a person who has died of other causes. Heart transplantation enables some patients with heart failure to lead active, healthy lives once again. However, a person who has received a heart transplant must take medications to suppress the immune system for the rest of his or her life in order to prevent rejection of the new heart. These drugs can have serious side effects, making a person more vulnerable to infections and certain types of cancer.
The first heart transplant was performed in 1967 by South African surgeon Christiaan Barnard. However, the procedure did not become widespread until the early 1980s, when the immune-suppressing drug cyclosporine became available. This drug helps prevent rejection without making patients as vulnerable to infection as they had been with older immune-suppressing drugs. About 3,500 heart transplants are performed worldwide each year. Today, about 83 percent of heart transplant recipients survive at least one year, and 71 percent survive for four years.
A shortage of donor hearts is the main limitation on the number of transplants performed today. Some scientists are looking for alternatives to transplantation that would help alleviate this shortage of donor hearts. One possibility is to replace a human heart with a mechanical one. A permanent artificial heart was first implanted in a patient in 1982. Artificial hearts have been used experimentally with mixed success. They are not widely used today because of the risk of infection and bleeding and concerns about their reliability. In addition, the synthetic materials used to fashion artificial hearts can cause blood clots to form in the heart. These blood clots may travel to a vessel in the neck or head, resulting in a stroke. Perhaps a more promising option is the left ventricular assist device (LVAD). This device is implanted inside a person’s chest or abdomen to help the patient’s own heart pump blood. LVADs are used in many people waiting for heart transplants, and could one day become a permanent alternative to transplantation.
Some scientists are working to develop xenotransplantation, in which a patient’s diseased heart would be replaced with a heart from a pig or another species. However, this strategy still requires a great deal of research to prevent the human immune system from rejecting a heart from a different species. Some experts have also raised concerns about the transmission of harmful viruses from other species to humans as a result of xenotransplantation.
Some scientists are working to develop xenotransplantation, in which a patient’s diseased heart would be replaced with a heart from a pig or another species. However, this strategy still requires a great deal of research to prevent the human immune system from rejecting a heart from a different species. Some experts have also raised concerns about the transmission of harmful viruses from other species to humans as a result of xenotransplantation.