Description, Causes and Risk Factors:
The heart is a specialized muscle that contracts regularly and continuously, pumping blood to the body and the lungs. It has four chambers - two at the top (the atria), and two at the bottom (the ventricles).
The pumping action of the heart is caused by a flow of electricity through the heart that repeats itself in a cycle. The normal trigger for the heart to contract comes from the heart's natural pacemaker, the SA node (sinoatrial node), which is in the right atrium. The SA node sends out regular electrical impulses, which make the atria contract and pump blood into the ventricles. The electrical impulse then passes to the ventricles through a form of `junction box' called the AV node (atrioventricular node). This electrical impulse spreads into the ventricles, causing the heart muscle to contract and to pump blood out of the ventricles. The blood from the right ventricle goes through the pulmonary artery and then to the lungs, and the blood from the left ventricle goes through the aorta and then around the body.
The heart consists of three layers:
Myocardium: The myocardium is the thick, muscular layer of the heart that contracts and squeezes the blood out of the heart. It is the myocardium that is affected by cardiomyopathy.
Pericardium: The pericardium is a thin, double layer that forms a protective sac around the outside of the heart. It contains a small amount of fluid - called pericardial fluid - which acts as a lubricant when the heart is contracting.
Endocardium: The endocardium is a thin layer on the inside of the heart, lining the chambers and valves.
Dilated cardiomyopathy is a disease of the heart muscle. It is often a genetic condition. This means that it is caused by a mutation in one or more genes that can be passed on through families.
Having dilated cardiomyopathy means that the left ventricle becomes dilated (stretched). When this happens, the heart muscle becomes weak, thin, or floppy and is unable to pump blood efficiently around the body. This can lead to fluid building up in the lungs, ankles, abdomen and other organs of the body and a feeling of being breathless. This collection of symptoms is known as heart failure. In most cases dilated cardiomyopathy develops slowly, so most people have quite severe symptoms before they are diagnosed. There may also be `mitral regurgitation'. This is when some of the blood flows in the wrong direction through the mitral valve, from the left ventricle to the left atrium.
Other conditions - such as coronary heart disease, high blood pressure (hypertension), or heart valve disease - can also cause the heart to become dilated and these conditions can also lead to the symptoms of heart failure. So, if you have symptoms of heart failure, your doctor will need to do tests to find out exactly what is causing the symptoms. Dilated cardiomyopathy occurs because of a problem with the heart muscle and not because of another condition.
Research has shown that dilated cardiomyopathy can be linked to an individual's genetic make-up.
Each one of us has our own genetic information that makes us different. Our genes make us who we are - for example, how tall we will be or what color hair we will have. This genetic information is held in our DNA in the cells of our body. The genetic information is produced through a coding system of proteins, that tells all of the cells in our bodies what their function should be. If there is a mistake in one of these codes, the cells will do something different or not develop as they should do. These mistakes are known as genetic mutations.
Scientists have identified some abnormal genes that are known to affect the development of heart muscle, and that may cause dilated cardiomyopathy. But they have also found many other genetic mutations that could possibly cause the condition, so this makes it more difficult to do reliable genetic testing on individuals to find out if they have the condition.
Also, some non-genetic conditions are known to be linked to an increased risk of developing dilated cardiomyopathy. These are:
Autoimmune disease: The body's immune system is responsible for defending the body against infection - for example, against viruses and bacteria. Sometimes the immune system breaks down and starts to attack the body's own tissues. This is called auto-immune disease. Some people who are diagnosed with dilated cardiomyopathy appear to have this condition.
Exposure to toxins (or poisons) or certain medicines: In very rare cases, exposure to certain toxins can cause dilated cardiomyopathy. In these cases, we do not know if the person developed the condition because they already had genetic tendency to develop it or whether toxin caused the cardiomyopathy. Some of the anticancer medicines may cause dilated cardiomyopathy.
In about 1 in every 1500 to 1 in every 15,000 pregnancies, the woman can develop dilated cardiomyopathy. It can occur from mid to late pregnancy or soon after delivery and is known as peripartum cardiomyopathy. It is possible that, in these circumstances, the woman may already have had dilated cardiomyopathy but it had not been diagnosed. For most women, the dilated heart returns to normal within six to eight weeks of the delivery, provided she gets the appropriate treatment. However, it is possible that the condition could develop again in subsequent pregnancies.
Viral infections: Viral myocarditis is commonly caused by enteroviruses (most commonly Coxsackie B virus), and adenoviruses. It is thought that dilated cardiomyopathy may occur when the heart muscle is badly damaged by the initial infection. Or it may be that the virus triggers the body's own defense system (the immune system) which then attacks and damages the heart muscle.
Other factors such as alcoholism, smoking, thyroid disease, diabetes may also increases the chance of getting dilated cardiomyopathy.
Symptoms may include:
Swelling of the lower extremities.
Fainting (caused by conditions such as irregular heart rhythms, abnormal responses of the blood vessels during exercise, or no cause may be found).
Palpitations (fluttering in the chest due to abnormal heart rhythms).
Dizziness or lightheadedness.
Blood clots due to blood flowing more slowly through the body. If a blood clot breaks off, it can be carried to the lungs (pulmonary emboli), kidney (renal emboli), brain (cerebral emboli or stroke), or limbs (peripheral emboli).
Chest pain or pressure (occurs usually with exercise or physical activity, but can also occur with rest or after meals).
Shortness of breath.
Your doctor may suspect that you have dilated cardiomyopathy because of your symptoms, or because you have a heart murmur, or because of the results of your ECG (electrocardiogram). Or, you may be going for tests because someone else in your family has been diagnosed with the condition.
If your doctor suspects that you may have a dilated cardiomyopathy, he or she will send you to the hospital, usually as an outpatient, for a series of tests.Your doctor will also refer you to a cardiologist for specialist advice.
The most common tests for dilated cardiomyopathy are:
An electrocardiogram (ECG): This is the most basic test. It involves taping electrical leads onto your legs, arms and chest and taking readings of the electrical activity of your heart.
An echocardiogram: This test uses ultrasound waves to look at the structure of the heart. It produces a picture of the heart and allows doctors to measure the size of the chambers of the heart and how thick the heart muscle is and how well it is working. It also looks at the heart valves and can show if there is any regurgitation. Additional equipment, called Doppler ultrasound, can produce a color image of blood flow within the heart and provide information on how well the heart is working.
Exercise testing: This test is the same as the ECG described above, but is recorded before, during and after a period of time spent exercising on a treadmill or an exercise bike. This allows the doctor to examine any changes in the electrical patterns that occur with exercise, and analyze any abnormalities.
An angiogram: If you have chest pain or an abnormal heart rhythm, your cardiologist may suggest that you have other tests such as a coronary angiogram or an electrophysiological study (EPS). Both these tests are performed in an x-ray laboratory. The tests allow doctors to see parts of the body, and any medical items such as cardiac catheter tubes or pacing wires, using an x-ray camera. You will be asked to lie down on a special table and will be given a local anaesthetic in your groin. The cardiologist will then place fine tubes, called cardiac catheters or electrodes, into blood vessels in your groin. These are gently passed through the heart. During a coronary angiogram, the coronary arteries (the arteries that supply blood to the heart muscle) are injected with a dye to reveal any narrowing that could be caused by coronary heart disease.An EPS (electrophysiological study) involves placing electrical leads inside the heart to analyze its electrical properties and to bring on arrhythmias. This test can be useful for diagnosing and treating abnormal heart rhythms.
A physical examination: Your cardiologist will ask you lots of questions about your medical history. They will also ask you about your family, including your parents and possibly your grandparents. They may ask you if you have ever had symptoms such as blackouts or palpitations. Your cardiologist will also take your pulse to check your heart rhythmand the pumping action of your heart, listen to your heart and lungs with a stethoscope, and take your blood pressure.
At present there is no cure for dilated cardiomyopathy, but treatment with medicines helps to control symptoms and reduce the risk of the condition getting worse or of getting new symptoms. Some people may need to have a pacemaker or an ICD (internal cardiac defibrillator) fitted. In some very rare cases, a heart transplant may be considered.
Medicines may include:
Angiotensin II receptor antagonist.
Calcium channel blockers.
ACE inhibitors (angiotensin converting enzyme inhibitors).
Side effects of medicines: Positive.
Other Treatment Options:
ICD (internal cardiac defibrillator): An ICD acts in the same way as a pacemaker, but it can also identify any dangerous arrhythmias and deliver an electrical shock to `reset' the heart. Some people have described the shock as feeling like having a `kick in the chest'. An ICD is slightly larger than a pacemaker and is usually positioned under the chest wall muscle below the left shoulder. The procedure may take between one to three hours. Most people have a local anaesthetic as well as sedation, but some may have a full (general) anaesthetic. You will need to have check-ups at the ICD clinic once every three to six months. The battery lasts between four and eight years. When a new battery is needed, the box containing it can be replaced easily.
Biventricular pacemaker: If your symptoms are severe, you may need to have a biventricular pacemaker. This is a special type of pacemaker that helps to organize the electrical impulses and coordinate the contracting of the heart muscle. This is sometimes known as cardiac resynchronisation therapy (CRT).
Left ventricular assist device: If your heart failure is very severe, an artificial mechanical device can be fitted to help the heart muscle pump blood out of the heart. The device allows people to live as normal a life as possible out of hospital. These devices are commonly used if someone is waiting for a heart transplant.
Heart transplantation: For a very small number of people, heart transplantation may be considered.
Pacemaker: A pacemaker controls the heart rate and stops any excessive slowing of the heart that could trigger an arrhythmia. The pacemaker is usually implanted just under your left collarbone. The procedure usually takes about an hour and is normally done with a local anaesthetic and sedation. You will need to have follow-up checks every three to twelve months. The pacemaker battery usually lasts between six and 10 years (and sometimes even longer). When a new battery is needed, the box containing it can be replaced easily.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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