Coronary heart disease overview

# Overview
Coronary heart disease  (CHD), also called coronary artery disease (CAD), ischaemic heart disease, atherosclerotic heart disease, is a narrowing of the small blood vessels that supply blood and oxygen to the heart. This is usually the end result of the accumulation of atheromatous plaques within the walls of the arteries that supply the myocardium (the muscle of the heart) with oxygen and nutrients.  While the symptoms and signs of coronary heart disease are noted in the advanced state of disease, most individuals with coronary heart disease show no evidence of disease for decades as the disease progresses before the first onset of symptoms, often a "sudden" heart attack, finally arise.  After decades of progression, some of these atheromatous plaques may rupture and (along with the activation of the blood clotting system) start limiting blood flow to the heart muscle.

# Pathophysiology
Atherosclerotic heart disease can be thought of as a wide spectrum of disease of the heart. At one end of the spectrum is the asymptomatic individual with atheromatous streaks within the walls of the coronary arteries.  These streaks represent the early stage of atherosclerotic heart disease and do not obstruct the flow of blood. The streaks increase in size and lead to the formation of plaque within the arteries. When the plaque obstruct the passage of blood within the coronary arteries, it causes ischemia, or lack of oxygen, within the heart muscle.

# Differentiating Coronary heart disease from other Diseases
There are a large number of causes of chest pain that coronary heart disease must be distinguished from.

# Epidemiology and Demographics
Coronary heart disease is the most common cause of sudden death, and is also the most common reason for death of men and women over 20 years of age.
According to present trends in the United States, half of healthy 40-year-old males will develop CHD in the future, and one in three healthy 40-year-old women. According to the Guinness Book of Records, Northern Ireland is the country with the most occurrences of CHD.

# Risk Factors
There are many risk factors and risk equivalents associated with coronary heart disease. Risk factors include cigarette smoking, hypertension, a family history of premature coronary artery disease, high LDL cholesterol, low HDL cholesterol, and older age. Some of these risk factors are modifiable, and are good targets for primary prevention in the health care setting.

# Screening and Risk Stratification
Risk stratification among patients with and at risk for coronary artery disease is critical so that the level of aggressiveness of management can match the risk of future events.  The magnitude of risk is often clearer in the patient who has had a vascular event than in the assessment of primary risk assessment (who will have a future event who does not yet have evidence of CHD).  Patients at low to intermediate risk by history and physical examination account for 75% of cardiovascular events.  There is therefore the need for improved risk stratification tools to reclassify those patients deemed to be at low risk on history and physical examination into a higher risk category.  In select populations, coronary artery calcium scoring, carotid intima-media thickness (CIMT) assessment and C reactive protein (CRP) assessment may offer addition improvements in risk stratification.

# Diagnosis

## Pretest Probability
Pretest probability of coronary artery disease is assessed basing upon the age, gender and the symptoms. Patients  are stratified into very low, low, intermediate, and high risk for CAD.

## History and Symptoms
Coronary heart disease may be asymptomatic, or have symptoms such as chest pain, shortness of breath, fatigue, weakness and lightheadedness.

## Electrocardiogram
Stress testing is used for risk stratification and diagnosis of coronary artery disease.

## Other Imaging Findings
Coronary angiography is useful in evaluating the whole length of the vessel from its origin to its branches. It is useful in identifying any thrombus, stenosis or dissections in coronary vessels.

# Treatment

## Medical Therapy
Goals for treating coronary artery disease include lowering blood pressure, maintaining HbA1c levels to less than 7%, and lowering LDL cholesterol. Long-term treatment will generally depend on the symptoms and severity of disease, and include aspirin, ACE inhibitors, and other ani-coagulant and anti-platelet regimens. The mainstay of treatment for stable angina which occurs with exertion, includes nitroglycerin. When unstable angina causes symptoms at rest, or in the setting of an acute myocardial infarction, the immediate therapy is morphine, oxygen, nitrate and aspirin. Angioplasty may also be required in cases of acute coronary syndrome.

## Primary Prevention
The LDL target in primary prevention depends upon the patient's risk factors.  If the patient has CHD or its equivalent, then the LDL goal is under 100 mg/dl.  If the patient has 2 risk factors, the LDL goal is 130 mg/dl.  If the patient has < 2 risk factors, the LDL goal is < 160 mg/dl. Attempts should be made to reduce triglyceride levels and to increase HDL levels. The underlying causes for existing dyslipidemias should be identified and appropriately managed. Drugs that cause dyslipidemias should be avoided. Patients should be evaluated reguarly for the presence of risk factors for coronary heart disease, and those with increased risk should be counseled on the beneficial effects of daily aspirin therapy. Patients should also regularly be counseled about modifying risk factors such as obesity, hypertension, smoking, and the benefits of an exercise plan.

## Secondary Prevention
Patients who should be treated with secondary prevention are those with established atherosclerosis including peripheral artery
disease; carotid artery disease; atherosclerotic aortic disease; diabetes and those with a Framingham Risk Score of > 20%.
There are 12 aspects of secondary prevention: Smoking cessation; blood pressure control; lipid-lowering; increasing physical activity; weight loss; diabetes control;  antiplatelet agents/anticoagulants; RAS blockers; beta-blockers; depression management; cardiac rehabilitation and influenza vaccine. Please note that secondary prevention guidelines, especially, those involving medication, may differ between UA/NSTEMI; STEMI; and Chronic Stable Angina.