What is Heart Disease?
Heart disease or cardiovascular disease is an umbrella term for any of several conditions that make it difficult for the heart to pump blood through the body. Heart disease is the leading cause of death for both men and women in the United States and is responsible for the deaths of millions of Americans each year.
Heart disease includes such conditions as coronary artery disease, heart failure, and heart arrhythmias, and can lead to the conditions known as angina and heart attack.
Causes of Heart Disease
Heart disease can be caused by a congenital problem with the heart, by infections such as rheumatic fever that damage the heart valves, or most commonly by atherosclerosis.
Atherosclerosis or hardening of the arteries is a major cause of heart disease. Atherosclerosis occurs when buildup of cholesterol and fat create plaques that thicken the walls of blood vessels causing them to stiffen and become more narrow.
When atherosclerosis is severe, it can weaken the heart in several ways. When it is widespread in arteries throughout the body, the heart must work extra hard to pump the same amount of blood through the now narrower vessels because the space for the blood to move through is smaller. Over the long term, the heart cannot sustain this heavy work load and begins to weaken, leading to the condition known as heart failure.
When atherosclerosis occurs in the vessels that nourish the heart itself, called the coronary arteries, the result is coronary artery disease. This condition results in reduced blood flow to the heart muscle tissue and can cause angina (chest pain) and if the blockage of these arteries is severe, can lead to heart attack (myocardial infarction).
Each of the different heart disease conditions has its own set of symptoms, though there is some overlap among them. However, it is important to note that in some cases a person with heart disease may experience no obvious symptoms. That is why it is important to have regular examinations by a physician, especially if you have any of the risk factors for heart disease such as a family history of heart disease, high cholesterol, smoking, or diabetes mellitus.
Coronary Artery Disease
Coronary artery disease is a narrowing of the arteries that feed the heart. While it may cause no obvious symptoms, it may also lead to angina and sometimes to heart attack.
When the coronary arteries are partially blocked by the plaques of atherosclerosis, the heart cannot nourish itself well enough when it is working hard. The result is angina, pain in the chest often described as heaviness, pressure, aching, or burning that may be brought on by stress or physical activity. The pain may also radiate into the shoulders, neck, or arms.
Other symptoms that can occur with coronary artery disease include:
-- Shortness of breath
-- Heart palpitations (feeling like your heart is "skipping a beat")
-- A faster heartbeat
-- Weakness or dizziness
When there is a near complete blockage of one of the coronary arteries, the heart muscle tissue that normally receives oxygen and nutrients from that artery begins to die. When the coronary arteries are narrowed due to atherosclerosis, all it takes is a small clot that forms spontaneously on the wall of the vessel, or a small clot from elsewhere in the body that breaks free and lodges in the already narrowed artery, to stop blood flow completely. The result is a heart attack (myocardial infarction). Symptoms of heart attack often include:
-- Discomfort, pressure, heaviness, or pain in the chest or below the breastbone
-- Discomfort radiating to the back, jaw, throat or arm (especially the left arm)
-- Fullness, indigestion or choking feeling
-- Shortness of breath
-- Sweating, nausea, vomiting or dizziness
-- Extreme weakness or anxiety
-- Rapid or irregular heartbeats
Symptoms usually last for half an hour or longer and may become progressively worse over time. If you have these symptoms, it is a medical emergency and you need to CALL 911 IMMEDIATELY. Do not wait to see if you feel better, because the longer you wait before receiving treatment, the more damage may be done to your heart and the greater your risk of death or permanent disability.
Heart failure is a chronic condition in which the heart is no longer able to pump enough blood to the body to sustain the tissues. It can be caused by anything that weakens the heart muscle. Some common causes include: chronic high blood pressure, previous myocardial infarction, heart valve disease, and cardiomyopathy.
The symptoms of heart failure may include:
-- Shortness of breath during activity or at rest, especially when you lie down flat in bed
-- Rapid weight gain
-- Cough that produces white mucus
-- Swelling (edema) in ankles, legs and abdomen
-- Fatigue and weakness
-- Rapid or irregular heartbeats
-- Nausea, palpitations, or chest pain
If the left side of the heart is primarily affected, blood may pool in the lungs causing fluid to build up in the air spaces which makes breathing difficult. If the right side of the heart is primarily affected, blood may pool in the legs and lead to fluid buildup in the feet and ankles called edema. When both sides are affected, both types of symptoms may occur.
An arrhythmia is an irregular heartbeat and can be caused by several factors, including congenital heart abnormalities, previous myocardial infarction, damage to heart tissue, and an electrolyte imbalance. Symptoms of arrhythmias may include:
-- Pounding in your chest
-- Heart palpitations (feeling like your heart is "skipping a beat")
-- Dizziness or feeling light-headed
-- Shortness of breath
-- Chest discomfort
-- Weakness or extreme fatigue
Many risk factors for heart disease are well known to doctors, while others are currently under intense study to verify their role in the development of the disease. What follows are some of the well established major risk factors that increase one¿s risk of developing heart disease.
Non-Controllable Risk Factors
Put very simply, the older you get, the more likely you are to develop heart disease. Age causes tissues to become less resilient and the heart and blood vessels are no exception.
Men are more likely to develop heart disease throughout their lifetime than women. However, most of this difference is accounted for by the fact that young males are more likely than young females to develop the disease because reproductive age women are protected from developing it by their high levels of the hormone estrogen. After menopause, women's levels of estrogen drop off significantly and so post-menopausal women have almost the same rate of heart disease as similarly aged men (though their rate is still slightly lower).
Family history of heart disease
If your brother, father, or grandfather had a heart attack before age 55, or your sister, mother or grandmother had one before age 65, your risk of having a heart attack is increased. Also, if you yourself have had a previous heart attack, this also increases your risk of having subsequent heart attacks. Genetic conditions may also predispose you to having high cholesterol or triglycerides, high blood pressure, diabetes, or obesity, all of which are themselves risk factors for developing heart disease.
The risk of heart disease is higher in African Americans, Mexican Americans, American Indians, and Native Hawaiians than in Caucasians. Some of this increased heart disease risk is due to a greater risk of high blood pressure, diabetes, or obesity in these populations
Diabetics have difficulty regulating their blood sugar due to an inability to make (type I) or respond to (type II) insulin. They also tend to have low levels of the "good" HDL cholesterol. Even if their disease is well-managed, diabetics have an increased risk of heart disease because blood sugar fluctuations tend to cause damage to the blood vessels over time and can lead to circulatory problems and atherosclerosis.
Controllable Risk Factors
All of the risk factors mentioned above cannot be controlled. However, several risk factors can be controlled, so if you have one or more of the risk factors above, you may want to pay special attention to limiting the risk factors that you can control.
Am I at risk for heart disease?
You can assess your own risk for heart disease by answering the following questions:
-- Do you smoke?
-- Is your blood pressure 140/90 mmHg or higher, OR have you been told by your doctor that your blood pressure is too high?
-- Has your doctor told you that your total cholesterol level is 200 mg/dL or higher, OR your HDL (good cholesterol) is less than 40 mg/dL?
-- Has your father or brother had a heart attack before age 55, OR has your mother or sister had one before age 65?
-- Do you have diabetes OR a fasting blood sugar of 126 mg/dL or higher, OR do you need medicine to control your blood sugar?
-- Are you over 55 years old?
-- Do you have a body mass index (BMI) score of 25 - 30 or higher?
-- Do you get less than a total of 30 minutes of physical activity on most days?
-- Has a doctor told you that you have angina (chest pains), OR have you had a heart attack?
If you answer yes to any of these questions, you have an increased risk of having a heart attack. If you have more than one of these risk factors, you should be sure to see your physician regularly and you may want to ask him or her how you can lower your risk.
Symptoms of Heart Disease
Heart disease may cause many of the recognizable symptoms mentioned above like shortness of breath and chest pain, or it may cause no symptoms at all until it is too late. Seeing your doctor for regular physical examinations may allow your doctor to notice signs of heart disease before you ever experience symptoms. Your doctor can assess your risk factors for developing heart disease, which include: advancing age, family history of heart disease, high blood pressure, high cholesterol and triglycerides, obesity, diabetes mellitus, sedentary lifestyle, and exposure to tobacco smoke.
If your doctor determines that you are at elevated risk for developing heart disease, he or she may order further tests to assess heart function. The main tests that can diagnose heart disease and heart attacks are below.
Non-Invasive Tests for Heart Disease
Electrocardiogram (EKG or ECG)
The ECG records the electrical activity of the heart using electrodes that are positioned on the chest. The ECG detects abnormalities in heart rhythm (arrhythmias) and can determine if you recently suffered a heart attack and predict if a heart attack is developing.
An X-ray of the chest can show if there is fluid accumulating in the lungs as commonly happens in heart failure and can also show if the heart is enlarged, which can occur when the heart is working too hard to pump blood through arteries narrowed by atherosclerosis.
An echocardiogram uses ultrasonic waves to produce an image of the heart in action similar to an ultrasound image of an unborn fetus. The echocardiogram shows structural problems with the heart, such as cardiomyopathy, and can also diagnose arrhythmias.
Exercise stress test
A stress test involves donning a lot of recording equipment and jogging on a treadmill to measure how your heart reacts to the stress of exercise. Heart rate, breathing rate, blood pressure, and ECG can be monitored simultaneously. Abnormal findings on the stress test can diagnose coronary artery disease or diagnose the cause of angina. It can also help determine what level of exercise is safe for you and also predict impending heart attacks.
Blood samples can be assessed for levels of proteins and enzymes related to heart disease. Important measures include cardiac enzymes (including troponin and creatine kinase), C-reactive protein (CRP), fibrinogen, homocysteine, lipoproteins, triglycerides, and brain natriuretic peptide (BNP).
An angiogram involves threading a flexible catheter through an artery in the leg up into the heart, then injecting a dye into the coronary blood vessels. An X-ray machine then allows visualization of the blood flow through the coronary arteries. Angiography is one of the most useful and accurate tools in diagnosing where and to what degree the coronary arteries are narrowed by atherosclerosis. It also measures blood pressure within the heart, blood oxygenation levels, and can help evaluate heart muscle function.
Thallium stress test
Just like the noninvasive exercise stress test mentioned above but with the addition of an injection of radioactive thallium before the test. This allows pictures of the heart in action to be taken with a special gamma camera. In addition to the findings of a noninvasive stress test, the thallium test measures blood flow of your heart muscle at rest and during stress and helps determine the extent of coronary artery blockage.
Heart Disease Treatments
Many treatments are available to help heart disease patients manage their disease. People who have many risk factors for heart disease or who already have a heart disease diagnosis should try to limit their risk factors. Several drugs are also available to help manage the factors that contribute to heart disease.
Cholesterol lowering drugs
These drugs help lower LDL cholesterol and raise HDL and include the drugs known as statins. They work by lowering the amount of cholesterol produced and released by the liver (statins), by blocking absorption of cholesterol from food in the small intestine (cholesterol absorption inhibitors), by causing greater release of cholesterol in bile (resins), or by changing the production of blood fats in the liver (niacin).
Blood pressure lowering drugs
Several classes of drugs help lower blood pressure in different ways. Diuretics cause increased elimination of water and sodium through the urine which lowers the blood pressure by reducing blood volume. ACE (angiotensin-converting enzyme) inhibitors and angiotensin II receptor antagonists are vasodilators that reduce blood pressure by opening blood vessels wider and allowing blood to flow more easily. Alpha and beta blockers reduce the heart rate and the output from the heart, thus reducing blood pressure.
Drugs that help prevent blood clots can help reduce the risk of heart attack. These include aspirin and warfarin that thin the blood as well as several anti-platelet drugs that limit the effects of these clotting agents. Thrombolytics are clot-busting drugs given in the hospital to heart attack and stroke patients to help dissolve the clot that is causing arterial blockage.
Antiarrhythmia drugs help keep abnormal heart rhythms under control. All of them work by affecting ion channels in the heart muscle cell membrane. There are sodium channel blockers, calcium channel blockers, potassium channel blockers and beta blockers.
Drugs that treat heart failure
For severe heart failure, therapy with inotropic drugs that help the heart beat with more force may be needed when other treatments no longer work. Sometimes called heart pump drugs, these medications must be delivered by intravenous infusion.
Some risk factors are beyond your control. If you have one or more of these non-controllable risk factors, you may want to pay special attention to reducing the risk factors that you can control. All of the following risk factors can be controlled and doing so may lower your risk of developing heart disease.
Controllable Risk Factors
High blood pressure
High blood pressure is defined as resting systolic pressure (the pressure when the heart contracts) above 140 mm Hg and/or resting diastolic pressure (the pressure when the heart is relaxed) above 90 mm Hg. It contributes to the development of heart disease in two ways: by making the heart work harder than normal which may cause the heart to enlarge and become weaker over time, and by damaging the arteries contributing to atherosclerosis. While the cause of elevated blood pressure is often unknown, lowering your blood pressure with medication may significantly reduce your chance of developing heart disease or if you already have heart disease, make progression or the disease less likely.
High levels of blood cholesterol, a lipid molecule that is used in all cells and in the synthesis of some hormones, raise the risk of heart disease and heart attack. Two kinds of cholesterol are recognized. LDL (low density lipoprotein) is a protein/cholesterol complex which carries cholesterol from the liver through the blood to all cells of the body, and HDL (high density lipoprotein) which carries cholesterol from cells back to the liver.
LDL is known as the "bad" cholesterol because high levels of LDL raise heart disease risk. LDL levels above 160 mg/dL increase the risk of cholesterol adhering to the walls of blood vessels and causing the plaques that lead to atherosclerosis. Levels of LDL below 100mg/dL are considered optimal and may lower your risk of developing heart disease or worsening existing heart disease. LDL levels increase when your diet contains a lot of saturated fats, cholesterol, and trans fats and decrease when you restrict your intake of these foods.
HDL is called "good" cholesterol because it represents cholesterol being sent to the liver and removed from the blood. High levels of HDL may reduce the risk of heart disease: 60mg/dL or above is considered protective, while below 40mg/dL is a major risk factor.
Triglycerides are the most plentiful type of fat in the body. They are the molecules stored by fat cells for use when energy is needed. Levels of blood triglycerides above 200mg/dL are considered high, while levels below 150mg/dL are considered low and may be protective against heart disease. High triglycerides are especially a problem when combined with high LDL and low HDL levels.
Obesity is defined as having a body mass index above 30 and raises the risk of heart disease. Belly fat contributes most to the effect. To find your BMI, multiply your weight in pounds by 705, divide by your height in inches, then divide again by your height in inches.
While it is often difficult to lose all of your excess weight, even a modest amount of weight loss may help lower your risk of heart disease. Losing even five percent of your body weight may help lower cholesterol and blood pressure. Improved diet and increased physical activity can help control weight and improve your cardiovascular health.
While developing diabetes is not always controllable, managing your diabetes is. Diabetics have difficulty regulating their blood sugar due to an inability to make or respond to insulin. They also tend to have low levels of the "good" HDL cholesterol. It is important to manage your diabetes by checking your blood sugar often and avoiding foods with high glycemic index that cause a spike in blood sugar. Medications are available that may help diabetics manage their disease better than ever before. Regular medical check ups and controlled blood pressure are critical to maintaining cardiovascular health for those with diabetes. Unfortunately, even well-controlled diabetes still increases one's risk of heart disease.
Lack of physical activity is a risk factor for heart disease because it contributes to the development of several other risk factors including: high blood pressure, low HDL and high LDL levels, obesity, and increased risk of diabetes. Regular, moderate-to-vigorous exercise is important to reduce the risk of heart and blood vessel disease because exercise can help control blood cholesterol, diabetes and obesity as well as help lower blood pressure in some people. The American Heart Association recommends 30 minutes of moderate exercise five times per week or 20 minutes of vigorous exercise three times per week to benefit the heart and lungs.
Exposure to tobacco smoke
The single most preventable risk factor for heart disease is cigarette smoking. Smokers face double the risk of heart attack than non-smokers and are also more likely to die if they do have a heart attack. Smoking is the single greatest risk factor for sudden cardiac arrest. Secondhand smoke can also increase the risk of heart disease.
Quitting smoking lowers blood pressure, raises HDL levels and begins to reverse some of the damage done to the heart and vessels from tobacco smoke. If you smoke, quit now and over time your risk of heart disease will return to the same level as a non-smoker.