Coronary heart disease
Description
Coronary heart disease (CHD) is a chronic heart disorder that is triggered by atherosclerotic changes in the coronary arteries. These changes lead to an increased narrowing (stenosis) of the affected arteries, which is called coronary stenosis. Coronary stenosis in turn causes circulatory disorders of the heart muscle.
The various manifestations of coronary heart disease can have different underlying mechanisms. One or more coronary arteries may be narrowed or closed due to arteriosclerotic deposits (arteriosclerosis or "hardening of the arteries"). A circulatory disorder can be caused by a vasospasm (also: angiospasm) or by a pathological disorder of the small blood vessels (microvascular dysfunction). Depending on the extent of the atherosclerotic changes, CHD can be divided into one-vessel coronary artery disease, two-vessel coronary artery disease, three-vessel coronary artery disease and left main artery disease.
Symptoms
Coronary heart disease can be clinically "silent", i.e. without obvious symptoms. However, in most cases it does make itself noticeable through a number of typical complaints that, along with the presence of cardiovascular risk factors, often make a clinical diagnosis possible. These symptoms include typical/atypical angina pectoris (tightness in the chest), shooting pain in the chest, feeling of pressure in the chest, burning sensation behind the breastbone as well as anxiety or sweating. The symptoms of CHD can appear spontaneously - i.e. with no apparent cause - or may depend on physical conditions. Typical triggers include physical stress, exposure to cold, overly large meals and mental stress.
Acute coronary syndrome is the term for potentially life-threatening CHD manifestations. These are: a) unstable angina pectoris without the electrocardiogram (ECG) changes typical of infarct or a noticeable increase of cardiac enzymes in the blood (troponin, creatine kinase-MB); b) acute myocardial infarction without typical ECG changes (non-ST-segment elevation myocardial infarction) but with detectable cardiac enzymes in the blood; c) acute myocardial infarction with typical ECG changes (ST-segment elevation myocardial infarction) and with detectable cardiac enzymes in the blood.
Causes and Risks
The main risk factors for the occurrence of coronary heart disease include unfavorable blood lipids - high LDL cholesterol, low HDL cholesterol, elevated triglycerides, elevated lipoprotein(a) - hypertension, diabetes mellitus, smoking, and CHD in first-degree relatives (male relatives with heart attack, bypass or coronary vessel stent before the age of 55, females before the age of 65).
Other risk factors for CHD are: advancing age, male gender, obesity (especially adiposity or abdominal fat), lack of physical activity, psychosocial stress, unhealthy diet (too much fat or red meat, too few fruits, vegetables, legumes and other fibers).
Examination and Diagnosis
Before the actual physical examination, height and weight are measured, and if possible the waist circumference in centimeters and the Body Mass Index (BMI). Blood pressure and pulse rate are very important examination data as well. Using a stethoscope, vascular noises in the carotid arteries or large leg arteries, caused by atherosclerosis, can also often be detected. Finally, listening to the lungs can reveal whether they are normally aerated or if signs of inflammation or pulmonary congestion exist. Cardiac insufficiency is indicated if palpitating the abdomen shows an enlarged liver or if there is fluid retention (edema) in the legs. If CHD is suspected, laboratory tests provide important information about risk factors, especially fat and sugar metabolism. Evaluation of cardiac enzymes plays a particularly important role in a possible case of acute coronary syndrome or cardiac insufficiency. In any event it is also necessary to confirm the blood cell count, electrolytes, and the functioning of the kidney, liver and thyroid.
CHD diagnostics are targeted at the direct or indirect detection of coronary stenosis and myocardial hypoperfusion using invasive or non-invasive procedures. Non-invasive ones include: resting ECG, stress ECG (ergometry), Holter ECG, stress echocardiography, positron emission tomography (PET), myocardial perfusion scintigraphy (MPS), cardiac computed tomography (CT), cardiac magnetic resonance imaging (MRI), stress MRI, and calcium scoring via multidetector computed tomography (MDCT). MDCT is used to determine the extent of coronary calcium deposits (calcification).
Invasive diagnostics include coronary angiography, intravascular ultrasound (IVUS), coronary angioscopy, and intracoronary doppler flow measurement.
Treatment
The main goals in the treatment of coronary heart disease are to relieve the symptoms and positively influence the course of the illness. Treatment options include a change of lifestyle, controlling risk factors, taking medications, as well as measures to help improve the blood flow in the coronary arteries.
Some medications have been shown to improve the prognosis in coronary heart disease. These include the antiplatelet agents (e.g. aspirin, clopidogrel), statins (cholesterol-lowering), ACE inhibitors, and in certain cases beta-blockers. These must be distinguished from medications that alleviate angina pectoris, i.e. the symptoms of CHD. These include nitrates, calcium channel blockers, beta blockers and newer agents such as ranolazine and ivabradine.
Revascularization measures include percutaneous coronary intervention (PCI) or bypass surgery. Compared to treatment only with drugs, a PCI or bypass surgery can more quickly and sustainably achieve freedom from symptoms.
Bypasses can be used on various parts of the body, for example the leg arteries in case of peripheral arterial occlusive disease (PAOD) or the coronary arteries in case of coronary heart disease (CHD). Most commonly, the coronary arteries are supplied with a bypass. In forming the bypass, doctors often use veins that have been removed from the upper or lower legs of the same patient (aortocoronary bypass). Or they sew the end of the internal thoracic artery to a coronary artery, so that it participates in the blood supply (internal thoracic artery bypass). Another option to consider is removing arteries from the forearm (radial artery bypass).
Bypass surgery is performed under general anesthesia and usually with the aid of a heart-lung machine. The blood vessel previously removed to form the bypass (e.g. saphenous vein or radial artery) is sewn to the aorta, behind the constriction in the coronary arteries. If it is possible to use the left or right internal thoracic artery as a bypass, this is exposed and sewn as a bypass graft. Sometimes the physician places three or four bypasses, depending on how many constrictions need to be bridged. After the cardiac surgeon has checked that blood flow at the treated sites is ensured, the blood is passed back through the heart. As soon as the heart is functioning smoothly again, the heart surgeon removes the heart-lung machine and closes the chest. The whole operation takes an average of two to three hours.
In favorable locations on the affected coronary artery, doctors can now also perform bypass surgery on a beating heart, foregoing the use of a heart-lung machine. When the heart surgeon thus opens the chest in the region of the sternum as in the conventional bypass surgery, it is called OPCAB (off-pump coronary artery bypass) surgery. If he instead opens it laterally between the ribs, this method is called MIDCAB (minimally invasive direct coronary artery bypass) surgery. General anesthesia is also necessary in both of these procedures.
Course and Prognosis
Those with increased risk of cardiovascular disease or who already have coronary heart disease, should reconsider and change their habits to beneficially affect the course of the disease. It is advisable to plan these lifestyle changes in consultation with the doctor. For example one should give up smoking, should exercise regularly, have a diet balanced and rich in fiber (whole grains), reduce excess weight - though not with strict, quick diets but proper nutrition and exercise - and learn to deal with or avoid stress.