Ischemic heart disease

Ischaemic or ischemic heart disease (IHD), or myocardial ischemia, is a disease characterized by reduced blood supply to the heart muscle, usually due to coronary artery disease (atherosclerosis of the coronary arteries). Its risk increases with age, smoking, hypercholesterolemia (high cholesterol levels), diabetes, hypertension (high blood pressure) and is more common in men and those who have close relatives with ischaemic heart disease.

Symptoms of stable ischaemic heart disease include angina (characteristic chest pain on exertion) and decreased exercise tolerance. Unstable IHD presents itself as chest pain or other symptoms at rest, or rapidly worsening angina. Diagnosis of IHD is with an electrocardiogram, blood tests (cardiac markers), cardiac stress testing or a coronary angiogram. Depending on the symptoms and risk, treatment may be with medication, percutaneous coronary intervention (angioplasty) or coronary artery bypass surgery (CABG).

It is the most common cause of death in most Western countries, and a major cause of hospital admissions. There is limited evidence for population screening, but prevention (with a healthy diet and sometimes medication for diabetes, cholesterol and high blood pressure) is used both to prevent IHD and to decrease the risk of complications.

Signs and symptoms
Ischemic heart disease may present with any of the following problems:
 * Angina pectoris (chest pain on exertion, in cold weather or emotional situations)
 * Acute chest pain: acute coronary syndrome, unstable angina or myocardial infarction ("heart attack", severe chest pain unrelieved by rest associated with evidence of acute heart damage)
 * Heart failure (difficulty in breathing or swelling of the extremities due to weakness of the heart muscle)

The medical history distinguishes between various alternative causes for chest pain (such as dyspepsia, musculoskeletal pain, pulmonary embolism). As part of an assessment of the three main presentations of IHD, risk factors are addressed. These are the main causes of atherosclerosis (the disease process underlying IHD): age, male sex, hyperlipidaemia (high cholesterol and high fats in the blood), smoking, hypertension (high blood pressure), diabetes, and the family history.

Diagnosis
The diagnosis of ischemic heart disease underlying particular symptoms depends largely on the nature of the symptoms. The first investigation is an electrocardiogram (ECG/EKG), both for "stable" angina and acute coronary syndrome. An X-ray of the chest and blood tests may be performed.

Stable angina
In "stable" angina, chest pain with typical features occurring at predictable levels of exertion, various forms of cardiac stress tests may be used to induce both symptoms and detect changes by way of electrocardiography (using an ECG), echocardiography (using ultrasound of the heart) or scintigraphy (using uptake of radionuclide by the heart muscle). If part of the heart seems to receive an insufficient blood supply, coronary angiography may be used to identify stenosis of the coronary arteries and suitability for angioplasty or bypass surgery.

Acute chest pain
Diagnosis of acute coronary syndrome generally takes places in the emergency department, where ECGs may be performed sequentially to identify "evolving changes" (indicating ongoing damage to the heart muscle). Diagnosis is clear-cut if ECGs show elevation of the "ST segment", which in the context of severe typical chest pain is strongly indicative of an acute myocardial infarction (MI); this is termed a STEMI (ST-elevation MI), and is treated as an emergency with either urgent coronary angiography and percutaneous coronary intervention (angioplasty with or without stent insertion) or with thrombolysis ("clot buster" medication), whichever is available. In the absence of ST-segment elevation, heart damage is detected by cardiac markers (blood tests that identify heart muscle damage). If there is evidence of damage (infarction), the chest pain is attributed to a "non-ST elevation MI" (NSTEMI). If there is no evidence of damage, the term "unstable angina" is used. This process usually necessitates admission to hospital, and close observation on a coronary care unit for possible complications (such as cardiac arrhythmias - irregularities in the heart rate).

Depending on the risk assessment, stress testing or angiography may be used to identify and treat coronary artery disease in patients who have had an NSTEMI or unstable angina.

Heart failure
In patients with heart failure, stress testing or coronary angiography may be performed to identify and treat underlying coronary artery disease.

Pathogenesis
The disease process underlying most ischemic heart disease is atherosclerosis of the coronary arteries. The arteries become "furred up" by fat-rich deposits in the vessel wall (plaques).

Stable angina is due to inability to supply the myocardium (heart muscle) with sufficient blood in situations of increased demand for oxygen, such as exertion.

Unstable angina, STEMI and NSTEMI are attributed to "plaque rupture", where one of the plaques gets weakened, develops a tear, and forms an adherent blood clot that either obstructs blood flow or floats down further the blood vessel, causing obstruction further down.

Treatment
In stable IHD, antianginal drugs may be used to reduce the rate of occurrence and severity of angina attacks. Treatments for acute coronary syndrome and established coronary artery disease is discussed above in "diagnosis".

Treatment of coronary artery disease includes addressing "modifiable" risk factors. This includes suppression of cholesterol (usually with statins), even in those with statistically normal cholesterol levels, control of blood pressure, blood sugars (if diabetic), regular exercise and a healthy diet. Smokers are encouraged to stop smoking.

Prevention
Various treatments are offered in people deemed to be at high risk of coronary artery disease. These include control of cholesterol levels in those with known high cholesterol, smoking cessation, and control of high blood pressure.