| Video Resources: See the heart at work and learn more about cardiac conditions and diagnostics.|
Videos courtesy of Guidant Corp.
Heart disease affects more than 58 million Americans and remains the leading cause of death in the United States and most of the developed world.
The most common heart disease is coronary artery disease (CAD). CAD is caused by a narrowing or blocking of the arteries (blood vessels) that carry blood from the heart to the other organs. CAD is the number one killer of both men and women in the United States. Each year, more than 500,000 Americans die of heart attacks caused by CAD.
Lifestyle changes could prevent many of these deaths because risk factors for CAD include high blood pressure, high blood cholesterol, smoking, obesity, and physical inactivity--all of which can be controlled. Although medical treatments for heart disease have evolved, controlling risk factors remains key in preventing illness and death from CAD.
Risk factors are conditions that increase your risk of developing heart disease. Some can be changed and some cannot. Although these factors each increase the risk of CAD, they do not describe all the causes of coronary heart disease; even with none of these risk factors, you might still develop CAD.
Controllable risk factors include:
- High blood pressure
- High blood cholesterol
- Physical inactivity
- Stress (Although stress may be a risk factor for CHD, scientists still do not know exactly how stress might be involved in heart disease)
Uncontrollable risk factors include:
- Heredity (family history of CHD)
Coronary arteries are the blood vessels that transport oxygenated blood to the heart muscle and its electrical system. There are three main arteries: one on the right side of the heart that supplies oxygen and nutrients to the muscle pumping blood flowing to the lungs (the right ventricle), and two on the left side of the heart that supplies oxygen and nutrients to the muscle pumping blood to the rest of the body (The left ventricle). The coronary circulation moves blood through the arteries and into a smaller system of blood vessels called arterioles and capillaries. As it travels through the heart, the blood leaves nutrients and oxygen in the heart and picks up wastes through the venous system, which it finally deposits in the kidneys and liver for excretion. A blocked artery thus interrupts the functioning of the entire heart muscle pumping ability and its electrical system.
When the coronary arteries become narrowed or clogged and cannot supply enough blood to the heart, the result is CAD. If not enough oxygen-carrying blood reaches the heart, the heart may respond with pain called angina. The pain is usually felt in the chest or sometimes in the left arm and shoulder. (However, the same inadequate blood supply may cause no symptoms, a condition called silent angina.)
When the blood supply is cut off completely, the result is a heart attack. The part of the heart that does not receive oxygen begins to die, and some of the heart muscle may be permanently damaged.
The result of the injured heart muscle lead to dysfunctional pumping ability, preventing adequate forward blood flow to the body’s organs and tissues. This is called systolic dysfunction heart failure. Patients present with weakness or are limited in their ability to exert themselves or to perform daily activities. The injured heart muscle may lead to the back flow of blood (especially from the left side of the heart) that eventually creates an increase in pressure. This increased pressure is transferred to the lungs and creates a leakage of fluid within the lung that diminishes the ability to breath and obtain adequate oxygen. This is called diastolic dysfunction heart failure. The patient usually presents with symptoms of shortness of breath, inability to lay flat and swollen legs.
The other result of an injured heart muscle is an interruption of the electrical system of the heart and it leads to arrhythmias (irregular heart beats). Patients present with palpitation, dizziness and feeling of pressure and flutter on their chest.
What causes CAD?
CAD is caused by a thickening of the inside walls of the coronary arteries. This thickening, called atherosclerosis, narrows the space through which blood can flow, decreasing and sometimes completely cutting off the supply of oxygen and nutrients to the heart.
Atherosclerosis usually occurs when a person has high levels of cholesterol, a fat-like substance, in the blood. Cholesterol and fat, circulating in the blood, build up on the walls of the arteries. The buildup narrows the arteries and can slow or block the flow of blood. When the level of cholesterol in the blood is high, there is a greater chance that it will be deposited onto the artery walls, especially in the coronary circulation (the heart’s own blood supply) this process begins in most people during childhood and the teenage years, and worsens as they get older.
High blood cholesterol, high blood pressure, diabetes, male gender, advance age and smoking contribute to CAD. On average, each of these doubles your chance of developing heart disease. Therefore, a person who has all three risk factors is eight times more likely to develop heart disease than someone who has none. Obesity and physical inactivity are other factors that can lead to CAD. Being overweight increases the likelihood of developing high blood cholesterol and high blood pressure, and physical inactivity increases the risk of heart attack. Maintaining adequate blood pressure, diabetes management with blood sugar control, exercise, good nutrition, and smoking cessation are important to controlling the risk factors for CAD.
Chest pain (angina) or shortness of breath may be the earliest signs of CAD. A person may feel heaviness, tightness, pain, burning, pressure, or squeezing, usually behind the breastbone but sometimes also in the arms, neck, or jaws. These signs usually bring the patient to a doctor for the first time. Nevertheless, some people have heart attacks without ever having any of these symptoms.
It is important to know that there is a wide range of severity for CAD. Some people do not have any symptoms at all, some have mild intermittent chest pain, and some have more pronounced and steady pain. Still, others have CAD that is severe enough to make normal everyday activities difficult. Because CAD varies so much from one person to another, the way a doctor diagnoses and treats CAD will also vary. The following descriptions are general guidelines to some tests and treatments that may or may not be used, depending on the individual case.
The doctor initially asks for a description of symptoms, assesses the patient’s general physical condition through a standard medical examination and history taking. The doctor listens to the heart for swishing or swooshing sounds, collectively known as heart murmurs to gather clues about the patient’s heart condition. Abnormal heartbeats and some areas of damage, inadequate blood flow, and heart enlargement can be detected on the records. The EKG is imperative in the assessment of CAD; it is used primarily for assessment of any underlying heart problems and for further evaluation if the patient shows changes from a previous EKG. Another modality for evaluating CAD is a standard stress test exercise, where the patient walks on the treadmill and his or her response is simultaneously analyzed while the intensity increases. The patient evaluation includes blood pressure response, any change in the EKG and the capability to maintain work load during the stress test exercise protocol.
CAD is treated in a number of ways, depending on the seriousness of the disease. For many people, CAD is managed with lifestyle modification and medications. In any case, once CAD develops, it requires lifelong management and evaluation. Changes in diet include low in fat, especially saturated fat, and low cholesterol which will help reduce high serum blood cholesterol, a primary cause of atherosclerosis. In fact, it is even more important to keep cholesterol low after a heart attack to help lower the risk of a second one. Losing weight can help lower blood cholesterol and is the most effective lifestyle way to reduce high blood pressure, another risk factor for atherosclerosis and heart disease. Others with severe CAD may need surgery that includes either revascularization or heart valve repair. For the diabetic patient a strict blood sugar level, adequate blood pressure and lipid profile are imperative in their management.
People with CAD can also benefit from exercise. Recent research has shown that even moderate amounts of physical activity are associated with lower death rates from CAD. However, people with severe CAD may have to restrict their exercise somewhat. Check with a doctor to find out what are the best kinds of exercise.
Smoking is one of the three major risk factors for CAD. Quitting smoking dramatically lowers the risk of a heart attack and also reduces the risk of a second heart attack in people who have already had one.