• Obstructive coronary artery disease.
• Nonobstructive coronary artery disease.
• Coronary microvascular disease.

If coronary arteries are narrow, they cannot supply enough oxygen-rich blood to heart — especially when it’s beating hard, such as during exercise. At first, the decreased blood flow may not cause any symptoms. As plaque continues to build up in your coronary arteries, however, may develop the following coronary artery disease signs and symptoms:

• Chest pain (angina).You may feel pressure or tightness in your chest. This pain, called angina, usually occurs on the middle or left side of the chest. Angina is generally triggered by physical or emotional stress. The pain usually goes away within minutes after stopping the stressful activity. In some people it may radiate to right side of chest, jaw or upper abdomen.
• Shortness of breath.Usually due to either the arteries are reducing supply to heart muscle due to narrowing or If heart can’t pump enough blood to meet your body’s needs, you may develop shortness of breath or extreme tiredness with activity.
• Heart attack (Myocardial infarction)A completely occluded coronary artery will cause a heart attack. The classic signs and symptoms of a heart attack include crushing pressure in your chest and pain in shoulder or arm, sometimes with shortness of breath and sweating.

Women are somewhat more likely than men are to have less typical signs and symptoms of a heart attack, such as neck or jaw pain. And they may have other symptoms such as shortness of breath, fatigue and nausea.

Sometimes a heart attack occurs without any apparent signs or symptoms called as Silent MI

Causes

Coronary artery disease is thought to begin with damage or injury to the inner layer of a coronary artery, sometimes as early as childhood. The damage may be caused by various factors, including:

• Smoking
• High blood pressure
• High cholesterol
• Diabetes or insulin resistance
• Not being active (sedentary lifestyle)

Once the inner wall of an artery is damaged, fatty deposits (plaque) made of cholesterol and other cellular waste products tend to collect at the site of injury. This process is called atherosclerosis. If the plaque surface breaks or ruptures, blood cells called platelets clump together at the site to try to repair the artery. This clump can block the artery, leading to a heart attack.

• Age.
• Sex: Men are generally at greater risk of coronary artery disease. However, the risk for women increases after menopause.
• Family history: A family history of heart disease is associated with a significantly higher risk of coronary artery disease, especially first degree relative developed heart disease at an early age (<50 years).
• People who smoke have a significantly increased risk of heart disease especially at younger age and their chance of death is also higher compared to older people. Second hand smoke also increases a person’s risk of coronary artery disease.
• High blood pressure: Uncontrolled high blood pressure can result in hardening and thickening of arteries, it significantly contributes to other risk factors. This is infact most common risk factor
• High blood cholesterol levels:Cholesterol is like hard water in bathroom pipes, harder the water earlier the pipes get blocked. High levels of cholesterol in blood can increase the risk of formation of plaque and atherosclerosis.
• Diabetes is associated with an increased risk of coronary artery disease. Type 2 diabetes and coronary artery disease share similar risk factors, such as obesity and high blood pressure. Patients with diabetes usually have very diffusely diseased arteries which also reduces treatment options and complications significantly.
• Overweight or obesity : Excess weight typically worsens other risk factors.
• Physical inactivity: Lack of exercise also is associated with coronary artery disease and some of its risk factors, as well.
• High stress: Unrelieved stress in life may damage arteries as well as worsen other risk factors for coronary artery disease.
• Unhealthy diet: Eating too much food can increase risk of coronary artery disease. 

Coronary artery disease can lead to:

• Heart attack : If a cholesterol plaque ruptures and a blood clot forms, complete blockage of heart artery may trigger a heart attack. The lack of blood flow to heart may damage heart muscle. The amount of damage depends in part on how quickly receive treatment.
• Heart failure: If some areas of heart are chronically deprived of oxygen and nutrients because of reduced blood flow, or if your heart has been damaged by a heart attack, heart may become too weak to pump enough blood to meet body’s needs. This condition is known as heart failure.
• Abnormal heart rhythm (arrhythmia): Inadequate blood supply to the heart or damage to heart tissue can interfere with heart’s electrical impulses, causing abnormal heart rhythms.

The same lifestyle habits used to help treat coronary artery disease can also help prevent it. A healthy lifestyle can help keep arteries strong and clear of plaque. To improve heart health, follow these tips:

• Quit smoking.
• Control conditions such as high blood pressure, high cholesterol and diabetes.
• Stay physically active.
• Eat a low-fat, low-salt diet that’s rich in fruits, vegetables and whole grains.
• Maintain a healthy weight.
• Reduce and manage stress.