Circulatory system

Heart health and heart disease

Anatomy of the heart

The heart is a complex muscle, about the size of a fist, residing in the center of the chest. As with all muscles, the heart requires oxygen to work.

The heart has four chambers—two smaller atria and two larger ventricles. Blood comes into the heart via the atria and is pumped into the two larger chambers known as the ventricles. More specifically, the right atrium receives impure blood from the vena cavae—two large veins which enter the heart from the right side. The superior (top) vena cava brings in blood from the head, arms and upper body while the inferior (bottom) vena cava brings in blood from the trunk and legs (lower body).

Valves are similar to two-way doors and they help separate the chambers of the heart. As the heart beats, valves open and blood is pumped from one chamber to another. The right atrium and the right ventricle are separated by the tricuspid valve. Blood passes through the tricuspid valve into the right ventricle where it is moved into the pulmonary arteries. The pulmonary arteries then move blood into the lungs. It is in the lungs that blood low in oxygen is purified and loaded up with oxygen.

To summarize, the right side of the heart receives impure blood from the body and pumps it to the lungs which then purify it with oxygen. Purified blood is then returned to the left atrium via the pulmonary veins. From the left atrium, blood passes through the mitral valve to the left ventricle and is driven up the systemic arch (upper aorta) to the body.

The systemic arch first gives off a right innominate artery which further branches off into a right subclavian and a right carotid artery. These lead to the arms and head, respectively. The systemic arch then gives off a left carotid and a left subclavian, to head and arm, respectively. The systemic arch then continues around the anterior (back) of the heart to form the dorsal aorta, the great artery responsible for distributing blood to the whole posterior (back part) of the body. The left side of the heart, then, is responsible for pumping oxygen-rich blood to the body.

Heart health

Because the heart performs such an important function, it is important to maintain heart health in order to prevent or delay the onset of heart disease. Heart disease is any disease that affects the heart muscle or blood vessels. Despite efforts to educate the public about heart health, heart disease is still the leading cause of death in the United States, ahead of AIDS, cancer, and accidental death combined.¹

Risk factors for heart disease

Certain factors, called risk factors, determine a person's chances of developing heart disease. While some risk factors such as lifestyle or diet can be changed, other factors such as family history, genetics, and age cannot.

Exercise

Lack of exercise greatly affects overall health and can increase a person's risk for heart disease. Studies have shown that people need at least 30 minutes of aerobic exercise (i.e. brisk walking, jogging) at least three times a week in order to maintain good heart health. If you are unable to exercise for 30 minutes at a time, don't despair. Bouts of exercise (such as walking the dog, actively playing with children, gardening, going up and down flights of stairs, and vacumming) that add up to 30 minutes per day are just as effective as a 30-minute workout.

Exercise helps reduce the risk of heart attack and stroke by increasing levels of high-density lipoprotein (HDL or "good cholesterol"), regulating glucose, lowering blood pressure, and increasing the flexibility of arteries.

Diet

Sensible eating can also help reduce the risk of heart disease. Decreasing salt intake to no more than one teaspoon (6 grams) per day is but one heart-healthy habit. A heart-healty diet is one that consists primarily of fruits, vegetables, grains, lean meats and fish and that is low in fats, particularly saturated fats and cholesterol. Fats and cholesterol are higher in fatty red meats, whole milk, whole milk cheeses, eggs, cream-based dishes and rich desserts.²

Alcohol

Alcohol consumption also affects the heart. Moderate consumption every day has been shown to protect against heart disease and heart attacks. What is moderate drinking? Experts define moderate drinking as an average of one to two drinks per day for men and one drink per day for women. Drinking more than a moderate amount, however, can lead to heart-related problems such as high blood pressure, obesity, increased triglyceride levels, heart failure, stroke, irregular heartbeats, and cardiomyopathy (disease of the heart muscle). Alcohol contains calories but no nutrients. Beware—alcohol calories can add fat to the body, thereby increasing the risk of heart disease.³

Stress

Stress can also contribute to heart disease, and people with heart disease report experiencing heart pain during stressful situations. Heart attacks are more likely to occur during periods of high stress. This is because, when we feel stressed, heartrate and blood pressure increase, increasing the heart's need for oxygen. Increased blood flow and the release of additional hormones during stress response can also injure arteries. As arterial walls begin to heal, they thicken, making them more prone to artherosclerosis (plaque buildup).⁴

Smoking

Smoking is a major risk factor for heart disease. Smoking lowers levels of high-density lipoprotein (HDL or "good cholesterol"), increasing the risk of heart disease. Smoking combined with the use of oral contraceptives (see below) has also been shown to increase the risk of heart attack or stroke. Regardless how long or how much you have smoked, the good news is that you can immediately reduce your risk of heart attack by quitting.⁵

High blood pressure

If left untreated, high blood pressure, also known as hypertension, makes the heart work harder, accelerates artherosclerosis (hardening of the arteries), and increases the risk of heart attack, stroke, and kidney failure. Pregnancy, particularly during the third trimester, may trigger high blood pressure, but elevated blood pressure caused by pregnancy usually returns to normal after childbirth. Risk of heart disease is higher in black women, women with high blood pressure, and overweight women with high blood pressure. Although there is no cure for high blood pressure, it can be controlled through sensible diet, exercise, and medications.⁶

Cholesterol

In determining a person's risk for heart disease, doctors examine how levels of high-density lipoprotein (HDL or "good cholesterol"), low-density lipoprotein (LDL or "bad cholesterol"), and fats known as triglycerides relate to one another and to overall cholesterol levels. Because estrogen increases HDL levels in the blood (see below), women of childbearing age, in general, have higher cholesterol levels. The higher a woman's level of HDL, the less likely she is to suffer a heart attack or stroke. After menopause, however, HDL levels tend to drop, increasing the risk of heart disease. Blood cholesterol levels can be improved through diet, exercise, and in more severe cases, through cholesterol-lowering medications.⁷

Obesity

In women especially, obesity is a high risk factor of heart disease. Fat distribution is also an important consideration. Those with excess amounts of body fat around the waist are at greater risk than those with fat around the hips. Your doctor can help you design a program of diet and exercise to help you safely lose weight.⁸

Diabetes

Because it cancels the protective effects of estrogen in pre-menopausal women, diabetes is more common in women and poses a greater risk. One study has shown that women with diabetes have a higher risk of death from heart disease than men with diabetes. Increased risk may also be explained by the fact that diabetics tend to be overweight and sedentary, have high cholesterol levels, and are more likely to have high blood pressure. Your doctor can help you effectively manage your diabetes to help you reduce your risk of heart disease.⁹

Oral contraceptives (birth control pills)

Oral contraceptives have been shown to increase cardiovascular risk in women, particularly in women who smoke. Birth control pills raise blood pressure and blood sugar levels in some women. They have also been shown to increase the risk of blood clots. The risks associated with oral contraceptives increase as women age. Be sure to tell your doctor about any other risk factors before beginning any birth control pills.¹⁰

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1. How to Be Heart Healthy. Denton A Cooley, MD. Texas Heart® Institute. (2004)
2. How to Be Heart Healthy. Denton A Cooley, MD. Texas Heart® Institute. (2004)
3. How to Be Heart Healthy. Denton A Cooley, MD. Texas Heart® Institute. (2004)
4. How to Be Heart Healthy. Denton A Cooley, MD. Texas Heart® Institute. (2004)
5. Women & Heart Disease. Texas Heart® Institute. (2004)
6. Women & Heart Disease. Texas Heart® Institute. (2004)
7. Women & Heart Disease. Texas Heart® Institute. (2004)
8. Women & Heart Disease. Texas Heart® Institute. (2004)
9. Women & Heart Disease. Texas Heart® Institute. (2004)
10. Women & Heart Disease. Texas Heart® Institute. (2004)