Heart disease

http://our-medical-center.blogspot.com/2007/12/heart-disease.html
What is it?

Heart disease is a general term that refers to a variety of acute and chronic medical conditions that affect one or more of the components of the heart. The heart is a muscular, fist-sized organ that is located in the left side of the chest cavity. It continuously pumps blood, beating as many as 100,000 times a day. The blood that the heart moves carries oxygen and nutrients throughout the body and transports carbon dioxide and other wastes to the lungs, kidneys, and liver for removal. The heart ensures its own oxygen supply through a set of coronary arteries and veins. The heart is also an endocrine organ that produces the hormones atrial natriuretic hormone (ANP) and B-type natriuretic peptide (BNP), which coordinate heart function with blood vessels and the kidneys.

Internally, the heart is essentially hollow. It is divided vertically into two halves by a septum, and each side of the heart has two internal chambers – an atrium on top and a ventricle on the bottom. Venous blood enters the right side of the heart through the right atrium and is pumped by the right ventricle to the lungs, where carbon dioxide is released and oxygen acquired. Oxygenated blood from the lungs is transported to the left atrium and is pumped by the left ventricle into arteries that carry it throughout the body. Four heart valves regulate the direction and flow of blood through the chambers of the heart. It is their opening and shutting that gives the heart its characteristic “lub-dub” beat. The heart muscle itself is called the myocardium. Lining the chambers of the heart and the valves is a membrane called the endocardium. Encasing the outside of the heart is the pericardium – a layered membrane that is fibrous on the outside and serous (fluid-secreting) on the inside. The pericardium forms a protective barrier around the heart and allows it to beat in a virtually friction free environment.

Diseases affecting the heart may be structural or functional. Anything that damages the heart or decreases the heart’s supply of oxygen, makes it less efficient, reduces its ability to fill and pump, will disrupt the coordinated relationship between the heart, kidneys, and blood vessels and will harm not only the heart but the rest of the body as well.

Signs and Symptoms

Heart diseases may be acute or chronic. They may be transient, relatively stable, or progressive. They may cause a variety of signs and symptoms that frequently change and/or worsen over time. Chronic heart diseases can have episodes with acutely worsened symptoms; these may resolve (either on their own or with treatment), persist, or even become life-threatening. Patients with early heart disease may experience few or vague symptoms, such as fatigue, shortness of breath with or without effort, dizziness, and/or nausea; however, these symptoms do not indicate the particular type of heart disease present. These symptoms may also be seen with a variety of other conditions. Other signs and complications that may arise from heart disease include:

Arrhythmia – an irregular heartbeat

Dilation – stretching of one or more of the heart chambers, causing their interiors to become larger because of increased pressure

Embolism – blockage of a blood vessel by material that has traveled from a distant body site, most often a blood clot, but it can be due to fat or air or even amniotic fluid

Inability to keep up with increased demands for oxygen and clearance of waste products, such as during physical activity

Infarction – death of muscle cells due to blockage of blood flow

Insufficient contraction – not emptying or filling completely

Pain, frequently due to ischemia – a lack of sufficient oxygen because of reduced blood flow

Regurgitation – a backflow of blood causing increased pressure on the blood vessels of the lungs and liver

Stenosis – a narrowing of the openings of the heart

Tissue death – permanent loss of heart tissue due to lack of oxygen, leading to scarring

Ventricular hypertrophy – increased thickness of the walls of the heart, causing a decrease in the size of the chambers and also a decrease in the flexibility of the heart

Heart diseases may be due to:

Alcohol use

Anabolic steroid use

Atherosclerosis

Autoimmune conditions

Bacterial infection

Cocaine use

Congenital abnormalities

Diabetes

Diet, especially when high in saturated fat and cholesterol

Hypertension

Injury or trauma

Sedentary lifestyle

Smoking

Thyroid dysfunction (under and overactive)

Toxins, such as mercury, and sometimes chemotherapy drugs or HIV/AIDS drugs

Viral infection

Common Heart Diseases

Coronary heart disease (CHD) and Coronary artery disease (CAD) are the most common forms of heart disease. They are usually part of a systemic cardiovascular disease (CVD) – a narrowing of arteries in the heart and throughout the body over time due to a build-up of fatty deposits that form plaques (atherosclerosis). This narrowing can significantly limit the amount of blood carried by the arteries and decrease the amount of oxygen supplied to the tissues. As the coronary blood vessels gradually narrow, symptoms do not appear until most of the blood flow is lost to an area of the heart, when it can cause intermittent chest pain (angina) upon exercise that worsens in frequency and severity over time. When plaques suddenly enlarge (termed unstable plaques), an acute narrowing of the coronary artery can cause chest pain to develop at rest or with minimum exertion (termed unstable angina) or can even cause death of an area of the myocardium or heart attack (myocardial infarction); these forms of acute onset of chest pain are termed acute coronary syndrome.

Heart failure, usually called congestive heart failure (CHF), causes the heart to become less effective at circulating blood and less able to completely fill or empty the chambers. As a result, blood backs up into the legs, hands, feet, lungs and liver, causing swelling, shortness of breath and fatigue. Any gradual damage to the heart can lead to heart failure over time; most commonly, it is due to coronary artery disease, high blood pressure (hypertension), or heart valve damage (which can be either congenital or due to an infection) or previous heart attack. If the cause is temporary, heart failure may also be temporary; however, it usually is a chronic condition that worsens over time, often improving after treatment.

Cardiomyopathy is an abnormality of the heart muscle. It may be congenital or it may be a response by the heart to external pressures or toxins. One or more chambers of the heart may dilate (dilated cardiomyopathy), causing an enlargement in the size of one of the chambers of the heart. In other cases, one or more of walls of the heart may thicken (hypertrophic cardiomyopathy). Occasionally, cardiomyopathy may also be due to abnormal material accumulating in the wall of the heart, reducing the flexibility of the walls of the ventricles (restrictive cardiomyopathy). Cardiomyopathy may be due to decreased blood flow to the heart, exposure to chemicals that damage the heart (such as alcohol and cocaine and some drugs used to treat cancer or other conditions), to inherited muscle problems, or may have no obvious cause (called idiopathic cardiomyopathy).

Myocarditis refers to inflammation of the muscle of the heart. It often presents with an acute onset of shortness of breath or an irregular heart beat and can cause heart failure to develop quickly. It is often due to a viral infection.

Pericardial disease is a disease of the sac surrounding the heart. It may be due to a bacterial or fungal infection, trauma, an autoimmune process, cancer, or a previous heart attack. Infections of the pericardium may quickly become serious if left untreated. Pericarditis, an inflammation of the pericardium, may cause increased friction “rub” and pain in the chest cavity.

Congenital heart disease, which arises during fetal development, may potentially affect any part of the heart. The amount of dysfunction depends on what form the abnormality takes and the extent to which it alters the shape, integrity, and functionality of the heart.

Endocarditis is an inflammation of the membrane lining the heart and heart valves. It may be due to a microorganism or to an autoimmune process. When it is due to an infection, it frequently can be difficult to treat.

Heart valve conditions may cause a variety of dysfunctions, including:

Regurgitation - backflow of blood

Prolapse - part of the heart valve protrudes into the atrium, preventing a tight seal, which may lead to regurgitation and an increased risk of endocarditis

Stenosis - narrowing of the opening, which can affect blood flow rate

Tests

The goals of testing for heart disease are to distinguish between symptoms that are heart-related and those that are due to another condition. Testing is ordered to help determine which heart disease is present, to determine whether the disorder is acute or chronic, to monitor a cardiac event that is in progress – such as a heart attack, and to determine the severity and extent of the disease.

When a patient presents to the emergency room with acute coronary syndrome – a group of symptoms that suggest heart injury due to lack of blood flow – they are evaluated with a variety of laboratory blood tests and other tests. These are used to determine the cause of the pain and the severity of the condition. Since some treatments for a heart attack must be given within a short period of time to minimize heart damage, an accurate diagnosis must be quickly confirmed.

Heart disease that is causing few symptoms may be detected during a visit to the doctor for nonspecific symptoms such as fatigue. Doctors may order a variety of blood and other tests to investigate possible causes for the patient’s symptoms. Diagnosis of heart disease in these people may take time and patience.

Testing patients for existing heart disease is not the same as cardiac risk testing (which actually mostly determines risk of coronary heart disease). Cardiac risk testing is performed to screen asymptomatic people – to help determine their risk of developing coronary heart disease.

Laboratory Blood Tests
Cardiac biomarkers, proteins that are released when muscle cells are damaged, are frequently ordered when patients have symptoms of acute coronary syndrome, such as chest pain, pain in the jaw, neck, abdomen, back, or that radiates to the shoulder or arms, nausea, dyspnea, and lightheadedness.

Tests include:

Troponin - the most commonly ordered and cardiac-specific of the markers; will be elevated within a few hours of heart damage and remain elevated for up to two weeks

CK-MB – one particular form of the enzyme creatine kinase that is found mostly in heart muscle and rises when there is damage to the heart muscle cells

Myoglobin – a protein released into the blood when heart or other skeletal muscle is injured

BNP or NT-proBNP – released by the body as a natural response to heart failure; increased levels of BNP, while not diagnostic for a heart attack, indicate an increased risk of cardiac problems in persons with acute coronary syndrome

Because BNP is also released by the heart when it is stretched, BNP is also measured in those who have swelling of the legs or abdomen, or shortness of breath, to see if heart failure may be present.

More general blood tests that may be ordered:

Blood Gases – performed to evaluate oxygen, carbon dioxide, and pH levels

Complete Metabolic Panel (CMP) – a group of tests used to evaluate organ function

Electrolytes – four tests that evaluate the body’s electrolyte balance

Complete Blood Count (CBC) – looks at the body’s cells, checks for anemia

Other Evaluations
A range of other evaluations and tests are used to assess chest pain and other symptoms. These include:

A medical history, including an evaluation of risk factors such as age, CAD, diabetes, and smoking

A physical examination

An electrocardiogram (ECG or EKG) – a test that looks at the heart’s electrical activity and rhythm

Echocardiography – ultrasound imaging of the heart

Based on the findings of these tests, other procedures may be necessary, including:

Stress testing

Chest X-ray

CT (Computerized tomography) scan

Continuous ECG monitoring (sometimes also called Holter monitoring) – the patient wears a monitor that evaluates heart rhythm over a period of time

MRI (Magnetic resonance imaging)

PET (Positron emission tomography)

Radionuclide imaging

Cardiac catheterization – in this procedure, a thin flexible tube is inserted into an artery in the leg and threaded up to the coronary arteries to evaluate blood flow and pressure in the heart and the status of the arteries in the heart

Coronary angiography – X-rays of arteries using a radiopaque dye to help diagnose CAD; this procedure is performed during coronary catheterization

Tilt table test – ordered to evaluate syncope

Treatments

Treatments for heart disease depend on the condition and its severity. Acute conditions, such as a heart attack, require prompt medical intervention to minimize heart damage. For chronic conditions, doctors may recommend that their affected patients modify their diets, lose excess weight, exercise (under supervision), manage stress, and quit smoking. Conditions such as hypertension and diabetes should be controlled to minimize their affect on the heart. Heart failure often requires treatment with low salt diet and diuretics (to try to reduce the amount of fluid accumulating) as well as drugs to improve the function of the heart muscle, such as digoxin.

Medications may be necessary to help manage symptoms and control heart diseases. Surgical procedures may be required to bypass blocked arteries, replace defective heart valves, or fix congenital abnormalities. Those with infections may need to take antimicrobial drugs.

New medications, procedures, and guidelines for addressing heart disease continue to be developed. Patients should talk to their doctor about the best treatment options for their condition.

from labtestsonline.org
http://our-medical-center.blogspot.com/2007/12/heart-disease.html