Heart Disease: Overview

Heart disease is a broad term covering many conditions that prevent the heart from working properly and keep it from pumping blood effectively throughout the body.

Heart disease includes a group of diseases that prevent the heart from working as well as it should. It is the leading cause of death in developed countries, including the United States and Canada.

Only a little larger than a fist, a normal healthy heart is at the center of the body's cardiovascular system * . Each day the average heart beats, or expands and contracts, about 100,000 times. In a 70-year lifetime, an average human heart beats more than 2.5 billion times.

The circulatory system * is responsible for providing nourishment to the body's cells and removing waste from them. The arteries take oxygenated blood from the heart to the cells; the veins take blood from the right side of the heart, where it is pumped through the pulmonary arteries to the cells in the lungs for reoxygenation and recirculation by the left side of the heart.

Coronary arteries affected by atherosclerosis will eventually develop coronary artery disease, a condition in which the vessels are so narrow that they can no longer provide adequate nutrients or oxygen to nourish the heart muscle. Blood flow is blocked either partially or totally.

Heart attacks are injuries to the heart muscle that occur when blood flow through a coronary artery is interrupted, cutting off the vital supply of oxygen to the heart. Blood can be kept from the heart by narrowing of the arteries from atherosclerotic plaque; by a blood clot * blocking the narrowed vessel; or by a sudden contraction (spasm) of the artery in response to a lack of oxygen or blood. The part of the heart muscle affected by the blockage is usually slowly starved of oxygen. The longer the heart muscle goes without nourishment, the more muscle tissue deteriorates or dies. Quick action is essential. Healthcare workers use the phrase “time is muscle” to illustrate how crucial it is to seek immediate medical attention in the case of a suspected heart attack.

Whereas blocked arteries are the most common cause of heart attacks, there are many other factors that contribute to this dangerous condition, such as high blood pressure (hypertension). Pumping blood against high pressures inside the blood vessels (as occurs in people with uncontrolled hypertension) can put too much strain on the heart. Abuse of alcohol, viral infections, tuberculosis, parasites, or other vascular (blood vessel) diseases can also lead to heart disease.

Heart failure occurs when the heart can no longer sufficiently pump blood throughout the body. While the heart is still working, it cannot do its job properly. Although heart failure can affect any part of the heart, the problem usually occurs on the left side. When the left side of the heart fails, the chambers cannot keep up with the amount of oxygenated blood that is coming in, and blood can back up in the lungs, making it difficult for the person to breathe. In right-sided heart failure, the deoxygenated blood backs up in the veins, causing swelling in the legs, fatigue, and sometimes difficulty breathing. Heart failure can often be treated through diet, exercise, smoking cessation, medication, and sometimes, surgery.

Various forms of heart disease can also cause dysrhythmias (dis-RITHme-uhs), or disturbances in the normal heartbeat pattern. Although some dysrhythmias are harmless, many may cause severe problems. For example, ventricular fibrillation (ven-TRIK-yoo-lar fib-rill-AY-shun) is a type of abnormal heart rhythm in which pumping is uncoordinated and ineffective and can cause sudden death.

Sudden cardiac arrest (SCA), also known as cardiopulmonary arrest, is a life-threatening condition in which the person's heart simply stops beating. SCA is not the same as a heart attack or heart failure, although a heart attack can lead to cardiac arrest. In SCA, the complete stopping of the heart means that blood circulation also stops, starving the body's tissues of oxygen and nutrients. A person in SCA loses consciousness, stops breathing, and will die within minutes if not treated promptly. About 325,000 people experience SCA each year in the United States, and 90 percent of them die. Of those who are treated by bystanders within the critical period, however, 4 out of 10 survive.

The major diagnostic sign of SCA is the lack of a pulse. SCA is an emergency that must be treated within 3 to 5 minutes if the person is to survive. It is usually first managed with cardiopulmonary resuscitation (CPR), followed by defibrillation with the use of an automated external defibrillator (AED). People who are not healthcare professionals can take courses in CPR and the use of an AED through the American Red Cross or the American Heart Association.

Heart disease is not contagious, and to a large extent, can be prevented, controlled, and, in some cases, even reversed. When looking at the causes of heart disease, researchers divide the risk factors into those that people can control and those that they cannot. Among the factors that cannot be changed are the following:

The good news is that some risk factors can be controlled. These include the following:

Other risk factors that can be controlled include drinking too much alcohol too often, and either having too much stress in one's life or not coping effectively with it.

Heart disease is also a leading cause of death worldwide. The World Health Organization (WHO) reported that 17.5 million people died worldwide in 2012 as a result of heart disease. The countries with the highest rates of heart disease in 2012 were Mongolia, Russia, and the other countries of the former Soviet Union (above 500 deaths per 100,000 people), followed by Armenia, Egypt, Iraq, Macedonia, and Sierra Leone (between 400 and 500 deaths per 100,000 people).

In 2016 WHO predicted that worldwide heart disease death rates would climb until 2028, if developing nations continue the trend toward increased smoking and more Westernized diets.

The body makes all the cholesterol it needs, but people also get cholesterol from their diets, particularly when they eat foods made from animal and dairy products. High blood cholesterol levels can have many causes, including genes * (heredity) and lifestyle choices (diet). Too much cholesterol can lead to coronary heart disease. Hyperlipid disorders, in which there is too much cholesterol or too much triglyceride in the blood, are some of the most common inherited conditions, affecting one in every 500 people. In people with such disorders, risk factors such as obesity, cigarette smoking, and high blood pressure can increase the chance of coronary heart disease even further.

Heart disease is the number one killer in developed countries, and heart attacks are recognized as the most obvious sign of heart disease. Each year, millions of Americans have heart attacks. But one problem with heart disease is that in 20 to 40 percent of people a heart attack is the first symptom of the disease. By then, plaque may have narrowed one or more arteries, limiting their ability to supply an area of the heart muscle with the oxygen and nutrients it needs.

Because a heart attack can cause severe damage by robbing the heart of oxygen, a quick reaction to the earliest signs of a heart attack is essential. Angina pectoris (AN-ji-nuh PEK-tuh-ris), a squeezing, tightness, or heaviness in the chest that can extend to the left arm, neck, jaw, or shoulder blade, is often the first sign that someone with atherosclerosis is at risk of a heart attack. Physical exercise, a heavy meal, strong emotions, or extreme temperatures can bring it on. If angina occurs when a person is at rest, it means that the heart is starving for oxygen even when it is not working hard. Besides chest pain, weakness, fainting, profuse sweating, nausea, and vomiting can accompany a heart attack, although a heart attack that arrives without angina—a “silent” heart attack—may not be revealed until a patient visits the physician's office for an unrelated condition.

Sudden cardiac arrest may be preceded by such symptoms as blackouts, dizziness, chest pain, difficulty breathing, vomiting, and weakness, but it can also occur without any warning. Valve disease can cause related symptoms of dizziness, fatigue, weakness, shortness of breath, and chest pain when exercising. These same signs, along with edema (eh-DEE-muh), an accumulation of fluid that occurs when the heart cannot keep the circulation moving properly, can indicate heart failure. Gravity often pulls the fluid downward, causing swelling in the feet, ankles, and legs.

Depending on the type of heart disease, a physician can use a number of different tests to help pinpoint heart problems. They are divided into invasive tests done internally and noninvasive tests that can be performed externally. Noninvasive procedures include the following:

Invasive procedures include cardiac catheterization, which is used to evaluate coronary artery disease, causes of angina, complications following a heart attack, heart defects, and other internal disorders. A catheter, or long, thin tube, is inserted into the cardiovascular system, usually through an artery in the arm or leg. A contrast solution (a dye that will show up on film) is then injected to visualize the blood vessels on film (angiography). Depending on its position, the catheter can help doctors diagnose the extent of coronary artery plaque buildup or abnormalities of the aorta * and valves.

Although many heart conditions cannot be cured, they can be controlled with lifestyle changes, medication, or surgery, or a combination of these strategies.

Irregular heartbeats, heart failure, and angina are often treated with a combination of lifestyle changes and medications. One of the most common medications used is nitroglycerin (ny-tro-GLIS-er-in), in the form of a tiny pill dissolved under the tongue, which acts to open the heart's blood vessels and permit more oxygen to flow to the heart muscle. Beta-blockers decrease the heart's demand for oxygen by slowing down the heart rate. Studies have shown that aspirin can help to prevent recurring heart attacks by thinning the blood, which can prevent clots and make it easier for the blood to travel through narrowed vessels. At the time of a heart attack, patients may be given special clot-dissolving medications intravenously (injected into a vein) to help unclog the diseased coronary arteries. Medications are also used to control high blood pressure.

Angioplasty (AN-je-o-PLAS-tee), also called balloon angioplasty, opens up vessels blocked by plaque buildup. A specially designed balloon is threaded through an artery. Once positioned, the balloon is set at the narrowest portion of the blocked artery and inflated, pumping up and widening the channel. After the artery is opened, the balloon is withdrawn.

One problem with angioplasty is that coronary arteries opened by the procedure often close within three to six months. To prevent this closing, surgeons often place a stent, a 1-inch (2.54-centimeters) tube of wire like stainless steel shaped like a tiny coiled spring, into the vessel, where it is expanded. The stent props the vessel open like scaffolding supporting a tunnel. Stents can also be lifesaving for patients whose arteries suddenly collapse or become spastic (contract suddenly) and close during angioplasty, setting off a heart attack.

A pacemaker is an electrical device that can be inserted under the skin in the chest or abdomen to restore a regular heartbeat. Advanced devices can sense and respond to changes in body movement, temperature, and breathing rate.

Bypass surgery is a procedure in which a segment of vein taken from the leg or an artery from the chest is grafted to an opening in the side of the normal coronary artery above the obstructed (blocked) segment and then to the normal portion of the artery below the obstruction. Blood then bypasses the obstructed segment, much like a road that serves as a route around a construction site.

Damaged valves can be replaced with mechanical valves made of plastic or Dacron, or a biological valve taken from a pig, cow, or human donor.

Heart disease often represents a turning point in a person's life. People who formerly led unhealthful and inactive lives may be inspired to change the way they live by eating more healthful foods, exercising regularly, and quitting smoking.

In the case of a heart attack, full recovery generally takes about four to six weeks, depending on the extent of the injury, the patient's overall health, and the condition of the rest of the heart. Most people are able to resume regular activities within a few weeks or months. Like all patients with heart disease or damage, those who have had heart attacks need to adopt a more healthful lifestyle, including eating a low-fat diet. Most go on to recover and enjoy many more productive years of life.

See also Angina • Arteriosclerosis/Atherosclerosis • Diabetes • Dysrhythmia • Emergency Resuscitation (CPR) • Endocarditis, Infectious • Heart Attack (Myocardial Infarction) • Heart Murmur • Hypertension • Metabolic Syndrome • Obesity • Rheumatic Fever • Stress and Stress-Related Illness • Stroke • Tobacco-Related Diseases: Overview

* cardiovascular (kar-dee-o-VASku- lur) system is made up of heart and blood vessels.

* circulatory (SIR-ku-la-tor-ee) system is made up of the heart, arteries, veins, capillaries, and circulating blood.

* plaque (PLAK) is a raised patch or swelling on a body surface. Arterial plaque is a deposit of cell debris, calcium, and fatty materials that occurs on the inner surface of an artery.

* blood clot is a thickening of the blood into a jellylike substance that stops blood flow.

* menopause (MEN-o-pawz) is the end of menstruation.

* aerobic exercise (air-O-bik) is designed to increase oxygen consumption by the body; it helps keep the heart and lungs in shape.

* genes (JEENS) are chemical structures composed of deoxyribonucleic acid (DNA) that help determine a person's body structure and physical characteristics. Inherited from a person's parents, genes are contained in the chromosomes found in the body's cells.

* pacemaker is a device whose function is to send electrical signals that control the heartbeat. The heart's natural pacemaker is the sinoatrial node, a special group of cells. Sometimes it is necessary to implant a batterypowered pacemaker that sends small electrical impulses through an electrode placed next to the wall of the heart.

* congenital (kon-JEH-nih-tul) means present at birth.

* congestive (kon-JES-tiv) means characterized by accumulation of too much fluid.

* aorta (ay-OR-ta) is the major artery that carries blood from the heart to the rest of the body.