What Is Coronary Heart Disease (Coronary Artery Disease)? What Causes Coronary Heart Disease?

Coronary heart disease (CHD), also known as coronary artery disease is a narrowing of the blood vessels (coronary arteries) that supply oxygen and blood to the heart. Coronary heart disease is a major cause of illness and death.

Coronary heart disease is generally caused by atherosclerosis - when plaque (cholesterol substances) accumulates on the artery walls, causing them to narrow, resulting in less blood flow to the heart. Sometimes a clot may form which can obstruct the flow of blood to heart muscle. Coronary heart disease commonly causes angina pectoris (chest pain), shortness of breath, heart attack (myocardial infarction) and other symptoms.

The coronary arteries are called so because they encircle the heart like a crown. The Latin word corona means "crown".

According to the National Institutes of Health (NIH), USA, coronary heart disease is the leading cause of death for males and females in the USA. 17.6 million Americans were thought to have had the condition in 2006. It caused the death of over 425,000 people in the USA in 2006.

According to the National Health Service (NHS), UK, coronary heart disease causes the death of 1 in every 4 men and 1 in every 6 women in the United Kingdom - it is the UK's biggest killer. The risk of developing the disease increases with age. More males are affected than females.

About the heart - the heart is a muscle, about the same size as an adult human fist. It beats about 70 times per minute and pumps oxygen-rich blood around the body. After leaving the heart, blood goes to the lungs where it gathers oxygen. This oxygen-rich blood returns to the heart (from the lungs) and is pumped to organs throughout the body through arteries. The blood returns to the heart through veins and is pumped to the lungs again. This whole process of blood going to the lungs from the heart, then back, and then to organs and then back, and then to the lungs again, is called circulation. Coronary arteries are the heart's own network of blood vessels; they exist on the surface of the heart - they supply the heart muscle with oxygen.

According to Medilexicon's medical dictionary:

Coronary artery disease is "narrowing of the lumen of one or more of the coronary arteries, usually due to atherosclerosis; myocardial ischemia; can cause congestive heart failure, angina pectoris, or myocardial infarction."

What are the signs and symptoms of coronary heart disease (coronary artery disease)?

A symptom is something the patient senses and describes, while a sign is something other people, such as the doctor notice. For example, drowsiness may be a symptom while dilated pupils may be a sign.

If the coronary arteries narrow, the supply of oxygen-rich blood to the heart may become insufficient, especially if the patient is exerting some kind of physical activity. Initially, the reduced blood flow may not produce any symptoms. However, as fatty deposits (plaque) build in the coronary arteries, the following signs and symptoms may emerge:

• Angina - or angina pectoris (Latin for squeezing of the chest) - is chest pain, discomfort, or tightness that occurs when an area of the heart muscle is receiving decreased blood oxygen supply. Angina is usually felt as:
  
  
  • A squeezing, pressure, heaviness, tightening, squeezing, burning or aching across the chest, usually starting behind the breastbone.
  • This pain often spreads to the neck, jaw, arms, shoulders, throat, back, or even the teeth.
  • Patients may also complain of symptoms that include indigestion, heartburn, weakness, sweating, nausea, cramping, and shortness of breath.
  • Stable (chronic) angina usually is unsurprising, lasts a short period of time, and may feel like gas or indigestion. It is brought on when the heart is working harder than usual, such as during exercise. It has a regular pattern and can be predicted to happen over months or even years. Symptoms are relieved by rest or medication.
  • Unstable angina, often caused by blood clots, occurs at rest, is surprising, last longer, and may worsen over time.
  • Variant angina occurs at rest and is usually severe. Variant angina occurs when an artery experiences a spasm that causes it to tighten and narrow, disrupting blood supply to the heart. This can be triggered by exposure to cold, stress, medicines, smoking, or cocaine use.
• Shortness of breath - if the heart and/or other body organs are not getting enough oxygen the patient may start panting. There may also be incredibly tired with exertion.
• Heart attack - if the heart muscle does not have enough blood (and consequently oxygen) it dies and a heart attack occurs. Another name for a heart attack is myocardial infarction, cardiac infarction and coronary thrombosis. A heart attack commonly occurs when a blood clot develops in one of the coronary arteries. The clot, if it is big enough, can stop the supply of blood to the heart. During a heart attack the patient may experience:
  
  
  • Chest discomfort, mild pain
  • Coughing
  • Crushing chest pain
  • Dizziness
  • Dyspnea (shortness of breath)
  • Face seems gray
  • A feeling of terror that your life is coming to its end
  • Feeling really awful (general feeling)
  • Nausea
  • Restlessness
  • The person is clammy and sweaty
  • Vomiting
  A person who is having a heart attack usually feels the pain in his/her chest first. This pain then spreads to the neck, jaw, ears, arms, and wrists. With some patients, the pain also makes its way into the shoulder blades, the back, and the abdomen.
  
  The pain does not feel any better if the patient changes position, rests, or lies down. Often it is a constant pain, but it can come and go. Patients describe the pain as one of pressure, something squeezing. The pain can last from a few minutes to many hours.
  
  People with diabetes, and/or those over the age of 75 may experience a "silent heart attack". This is one that occurs with no pain at all.
  
  A heart attack is a medical emergency - it can result in permanent damage to the heart muscle if not treated immediately. Lack of prompt treatment can also result in death. People who think they are having a heart attack should call the emergency services immediately.

What are the risk factors for coronary heart disease (coronary artery disease)?

A risk factor is something which increases the likelihood of developing a condition or disease. For example, obesity significantly raises the risk of developing diabetes type 2. Therefore, obesity is a risk factor for diabetes type 2.

• Age - as people age their risk of developing narrowed arteries, or having some kind of damage in the arteries is greater.
• Sex - although the risk for women is still significant, especially after the menopause, males are at greater risk of developing coronary heart disease.
• Genetics - people who have a parent who developed coronary heart disease before the age of 60 years have a higher risk of developing it themselves, compared to other individuals.
• Smoking - carbon monoxide, which is present in tobacco smoke, can damage the inner lining of blood vessels, increasing the risk of atherosclerosis. Nicotine constricts the blood vessels (makes them narrower). A 20-per-day regular female smoker is 6 times as likely to develop coronary heart disease compared to women who have never smoked. Male regular smokers generally are three times as likely to develop the condition compared to male lifetime non-smokers.
• Uncontrolled hypertension (high blood pressure) - the lumen (the channel through which blood flows in the blood vessels) becomes narrower as the arteries thicken and harden.
• High blood cholesterol - high blood cholesterol levels makes the build-up of plaques and consequent atherosclerosis more likely. High cholesterol can be caused by high LDL (low-density lipoprotein) levels or low HDL (high-density lipoprotein) levels. LDL is also known as the bad cholesterol, while HDL is also known as the good cholesterol.
• Diabetes - both types of diabetes are linked to a higher risk of developing coronary heart disease, especially Diabetes Type II, which is often caused by obesity.
• Obesity - obese people have a higher risk of developing coronary heart disease.
• Lack of exercise - people who lead very sedentary lives have a higher risk of developing coronary heart disease.
• Emotional/mental stress - there is a link between chronic (long-term) emotional/mental stress and damage to arteries.

Some conditions, such as metabolic syndrome or diabetes type II have several signs and symptoms which are linked to a higher risk of developing coronary heart disease.

Risk factors not linked to obesity, high cholesterol, hypertension, etc.:

• C-reactive protein (CRP) - research has indicated that CRP concentration is associated with future risk of a wide range of common diseases, including: heart attack, stroke, deaths from various cancers, chronic lung disease, injuries, and other conditions. CRP is produced by the liver in response to injury or infection. Muscle cells within coronary arteries also produce CRP. However, this study suggests that the causality seems unlikely.
• Homocysteine - this is an amino acid produced by the body, often as a by-product of consuming meat. It is made from methionine, another amino acid, and is then turned into other amino acids. Coronary heart disease, as well as other cardiovascular conditions seems more likely to occur if homocysteine levels are elevated.
• Fibrinogen - a blood protein which is involved in the blood clotting process. Excess levels may encourage the clumping of platelets, resulting in the formation of clots.
• Lipoprotein (a) - may undermine the body's ability to dissolve blood clots. Lipoprotein (a) forms when an LDL particle attaches to a specific protein.

What are the causes of coronary heart disease (coronary artery disease)?

Experts say that coronary artery disease starts with injury or damage to the inner layer of a coronary artery. According to the Mayo Clinic, USA, in some cases this damage/injury may occur during childhood.

When the artery's inner wall is damaged plaques (fatty deposits) build up at the site of the injury. The fatty deposits - known as called atheroma - consist of cholesterol and other cellular waste products. This accumulation at the site of the damage is called atherosclerosis. If bits from the fatty deposits break off or rupture, platelets will clump in the area in an attempt to repair the blood vessel - sometimes this clump can block the artery, which either reduces or blocks blood flow, and can result in a heart attack.

Diagnosing coronary heart disease (coronary artery disease)

The doctor will probably ask the patient questions about their medical history, symptoms and carry out a physical examination. One or some of the following diagnostic tests may also be ordered:

• ECG (electrocardiogram) - this device records the electrical activity and rhythms of the patient's heart. Electrodes are attached to the patient's skin and impulses are recorded as waves are displayed on a screen (or printed on paper). The test may also reveal any damage to the heart from a heart attack.
• A Holter monitor - the patient wears a portable device which records all his/her heartbeats. It is worn under the clothing and records information about the electrical activity of the heart while the patient goes about his/her normal activities for one or two days. It has a button which can be pressed if symptoms are felt - then the doctor can see what heart rhythms were present at that moment. Some abnormalities may indicate a problem with blood flow.
• An echocardiogram - this is an ultrasound scan that checks the pumping action of the patient's heart. This test also helps distinguish systolic heart failure from diastolic heart failure (the heart is stiff and does not fill properly). Sound waves are used to create a video image of the patient's heart, which helps the doctor see how well the heart is pumping. The doctor measures the percentage of blood pumped out of the patient's left ventricle (the main pumping chamber) with each heartbeat - this measurement is call the ejection fraction.
  
  An ejection fraction is a crucial measurement which determines how well the heart is pumping. A healthy heart pumps out approximately 60% of the blood that fills the ventricle with each beat - a healthy heart has an ejection factor of 60%.
• Stress test - the aim here is to stress the heart and study it. The patient may have to use a treadmill or exercise machine, or take a medication that stresses the heart. Sometimes nuclear medicine or echocardiographic techniques are used to take pictures of the heart to find out whether there are any blockages in the heart arteries - such a blockage could be causing the heart failure. An oxygen uptake stress test will determine how well the patient's body is making up for his/her condition.
• Coronary catheterization - the doctor injects a special dye into the arteries of the heart through a catheter which is threaded through an artery, often in the leg, to the arteries in the heart. An X-ray machine is used to detect narrow spots or blockages revealed by the dye. If any blockage is found, a balloon may be pushed through the catheter and inflated; this squashes the clot and improves blood flow. A stent may be placed to keep the artery dilated.
• CT (computerized tomography) scan - CT scans can help the doctor visualize the arteries, detect calcium within fatty deposits that narrow coronary arteries, and some other heart abnormalities.
• MRA (magnetic resonance angiogram) - MRI imaging technology is frequently used with an injected contrast dye to determine whether there is any narrowing or blockages in the coronary arteries.
• Nuclear ventriculography - this test uses tracers (radioactive materials) to show the heart chambers. It is a non-invasive procedure and is done while the patient is resting. The doctor injects technetium (radioactive material) into the vein. The substance attaches to red blood cells and passes through the heart. Special cameras/scanners trace the technetium as it travels through the heart.
• Blood tests - to measure blood cholesterol levels. The patient may be asked not to eat for at least 12 hours before the test. Blood tests are particularly important if the patient:
  
  
  • Is aged over 40 years
  • Has a family history of cardiovascular disease
  • Has a family history of a cholesterol-related condition
  • Is obese/overweight
  • Has hypertension (high blood pressure)
  • Has another medical condition, such an under-active thyroid gland, kidney disease, acute pancreatitis, or any condition which may elevate blood levels of cholesterol.

What are the treatment options for coronary heart disease (coronary artery disease)?

Although coronary heart disease cannot be cured, it can be managed much more effectively today than in the past. Treatment consists mainly of lifestyle changes, and perhaps some medical procedures and medications.

Lifestyle - some specific lifestyle changes can significantly improve the health of the arteries:

• Stop smoking
• Eat a healthy and well balanced diet
• Exercise regularly
• Aim for an ideal bodyweight
• Reduce emotional/mental stress

Medications:

• Medications to modify cholesterol levels - these include statins, fibrates and bile acid sequestrants. These drugs reduce the main material that deposits on the coronary arteries. They lower LDL levels.
• Low-dose aspirin and clot-busting medication - blood clots in the coronary arteries can cause heart attacks. The doctor may prescribe a low-dose aspirin and/or a clot-busting medication. If the patient has a bleeding disorder these medications may be unsuitable. These drugs help prevent the blood from clotting so easily, reducing the risk of angina or heart attack.
• Beta blockers - they reduce blood pressure as well as the heart rate, resulting in a lower demand of oxygen by the heart. Beta blockers help lower the risk of future heart attacks for patients who have had a heart attack.
• Nitroglycerin - these may be in the form of patches, sprays or tablets and control chest pain by reducing the heart's demand for blood and opening up (widening) the coronary arteries.
• ACE (angiotensin-converting enzyme) inhibitors - they lower blood pressure and also help slow down or stop the progression of coronary artery disease. If a patient has had a heart attack they may also help reduce the risk of future ones. Patients who take ACE inhibitors should not stop taking them without first checking with their doctor - there is a serious risk of rapidly-worsening symptoms.
• Calcium channel blockers - these drugs widen the coronary arteries, resulting in greater blood flow to the heart. They also help treat hypertension.

Surgery - if fatty deposit build-up has left the blood vessels very narrow, or if symptoms are not responding well enough to medications, surgery may be required to open up or replace blocked arteries.

• Percutaneous coronary revascularization (angioplasty and stent placement) - a catheter is inserted into the narrowed part of the artery. A deflated balloon is passed through the catheter to the affected area. When the balloon is inflated it compresses (squashes) fatty deposits against the artery walls. A stent (mesh tube) is sometimes left in the artery to help keep it open. In some cases, the stent releases a medication.
• Coronary bypass surgery - in this surgical procedure the surgeon creates a graft to bypass the blocked artery by using a vessel from another part of the body; the bypass graft can be a vein from the leg or an inner chest-wall artery. The blood, effective flows around the blocked/narrowed coronary artery. This procedure is usually done only when the patient has several blocked/narrowed arteries. Put simply, a small length of vein tubing is taken from one part of the body, one end of it is attached to just before the blockage, while the other end is attached to just after the blockage - the blood then effectively bypasses the blockage.
• Heart transplant - in some rare cases, if the heart is badly damaged and the patient is not responding well enough to treatment, the doctor may recommend a heart transplant. This involves replacing the damaged heart with a healthy donor one.
• Laser surgery - the surgeon makes several tiny holes in the heart muscle. These encourage the formation of new blood vessels to grow in the affected heart muscle.

Prevention of coronary heart disease (coronary artery disease)

If you can keep your LDL levels low and your HDL levels high, your risk of developing coronary heart disease is significantly lower (than someone who can't). The following lifestyle measures can help:

• Be physically active
• Consume alcohol in moderation or not at all
• Do not smoke
• Eat a healthy and balanced diet
• Keep your blood pressure under control
• Keep your diabetes under control
• Maintain a healthy body weight
• Reduce/control emotional and mental stress
• If you already have coronary heart disease, follow your doctor's instructions in order to prevent complications. This includes taking the prescribed medications.