Atherosclerosis, Stroke and Heart Attack

Atherosclerosis, Stroke and Heart Attack

 

I. Atherosclerosis

Atherosclerosis is the hardening and narrowing of the arteries. It is caused by the slow buildup of plaque on the inside of artery walls. Arteries are blood vessels that carry oxygen-rich blood from the heart to other parts of the body. Plaque is made up of fat, cholesterol, calcium, and other substances found in the blood. As it grows, the buildup of plaque narrows the inside of the artery and, in time, may restrict blood flow. There are two types of plaque:

• Hard and stable
• Soft and unstable

Hard plaque causes artery walls to thicken and harden. Soft plaque is more likely to break apart from the walls and enter the bloodstream. This can cause a blood clot to partially or totally block the flow of blood in the artery. When this happens, the organ supplied by the blocked artery starves for blood and oxygen. The organ's cells may either die or suffer severe damage. The resulting complications include:

• Coronary artery disease (heart attack and angina) - if the arteries that feed heart are affected.
• Stroke or transient ischemic attack - if the arteries that feed brain are affected.
• Peripheral arterial disease - if the arteries that feed legs, pelvis, or arms are affected.
• Renovascular hypertension - if the arteries that feed kidneys are affected. .

Diseases caused by atherosclerosis are the leading cause of illness and death in the United States.

I.1 Symptoms and Diagnosis

Atherosclerosis usually does not cause symptoms until its complications occur. Diagnostic methods include:

• Ankle/brachial index (ABI), which compares the blood pressure in the ankle with the blood pressure in the arm.
• Echocardiogram. This test uses sound waves to create a moving picture of the heart. Echocardiogram provides information about the size and shape of the heart and how well the heart chambers and valves are functioning. The test also can identify areas of poor blood flow to the heart, areas of heart muscle that are not contracting normally, and previous injury to the heart muscle caused by poor blood flow.
• CT scan, which provides computer-generated images of the heart, brain, or other areas of interest.
• Angiography. A test that allows the doctor to look inside arteries to see if there is any blockage and how much. A thin flexible tube is passed through an artery in the upper leg (groin) or in the arm to reach the arteries that may be blocked. A dye that can be seen on x ray is injected into the arteries. Using an x ray, the doctor can see the flow of blood through your arteries.
• Stress Test. Some heart problems are easier to diagnose when your heart is working harder and beating faster than when it’s at rest. During stress testing, you exercise (or are given medicine if you are unable to exercise) to make your heart work harder and beat faster while heart tests are performed.

 I.2 Causes

Atherosclerosis is a slow and progressive disease that may start in childhood. It is initiated by an accumulation and subsequent oxidation of low-density lipoprotein (LDL) in the arterial intima. The oxidized LDLs stimulate a series of events similar to inflammation.  Macrophages (converted from monocytes) are recruited to ingest oxidized LDL, producing foam cells. Then T lymphocytes, platelets and smooth muscle cells also join foam cells, expanding the plaque size. 

Since LDL is the origin of atherosclerosis and its complications, the cholesterol carried by LDL is often called bad cholesterol. By contrast, high-density lipoprotein (HDL) has many properties that can prevent atherosclerosis. The cholesterol carried by HDL is called good cholesterol.

 I.3 Treatment

Treatment for atherosclerosis includes:

• Lifestyle changes
• Medicines
• Special procedures and surgery

Lifestyle Changes

• Eat a cholesterol-lowering diet.
• Exercise, which can produce nitric oxide (NO) to prevent atherosclerosis (more info).

Medicines

• Cholesterol-lowering medicines.
• Anticoagulants to prevent clots.
• Antiplatelet medicines (such as aspirin) to stop platelets from clumping together.

Special Procedures and Surgery

• Angioplasty. This procedure is used to open blocked or narrowed coronary arteries. It can improve blood flow to the heart, relieve chest pain, and possibly prevent a heart attack.
• Coronary artery bypass surgery. This surgery uses arteries or veins from other areas in the body to bypass the diseased coronary arteries.
• Carotid artery surgery. This surgery removes plaque buildup from the carotid artery in the neck. This opens the artery and improves blood flow to the brain.
• Bypass surgery of the leg arteries. This surgery uses a healthy blood vessel to bypass the narrowed or blocked blood vessels. The healthy blood vessel redirects blood around the blocked artery, improving blood flow to the leg.

II. High Blood Cholesterol

Cholesterol is a waxy, fat-like substance that is found in all cells of the body. In addition to being a structural component of cell membranes, cholesterol also plays important roles in making hormones, vitamin D, and bile acids that aid in the digestion of foods.

Cholesterol itself is not harmful, but too much cholesterol in the blood, or high blood cholesterol, can be dangerous. Heart attack and stroke, two of the most common cardiovascular diseases, originate from high blood cholesterol, or more specifically, high concentration of cholesterol carried by low-density lipoproteins (LDLs).

Blood is watery, and cholesterol is fatty. Just like oil and water, the two do not mix. To travel in the bloodstream, cholesterol is carried in small packages called lipoproteins. There are two kinds of lipoproteins that carry cholesterol throughout the body.

• Low-density lipoprotein (LDL) - The higher the LDL level in the blood, the greater the chance to get cardiovascular diseases. The cholesterol carried by LDL is often called "bad cholesterol".
• High-density lipoprotein (HDL) - The higher the HDL level in the blood, the lower the chance to get cardiovascular diseases. The cholesterol carried by HDL is often called "good cholesterol". 

Why LDL is Bad

LDL plays an essential role in the pathogenesis of atherosclerosis, which can cause many complications, including heart attack and stroke. Diseases caused by atherosclerosis are the leading cause of illness and death in the United States. The initial step leading to atherosclerosis is the trap of LDL particles in the tunica intima (or simply called intima), which is the innermost layer of the artery wall. The intima contains endothelium, basement membrane and underlying connective tissue. The endothelium is in direct contact with the blood flow and the basement membrane separates epithelium from the underlying connective tissue.

The size of LDL particles varies from 18 to 25 nm in diameter. They can penetrate the endothelium efficiently. The LDL particle contains mainly the apolipoprotein B (ApoB), which can bind to proteoglycans in the complex matrix beneath the endothelium. The trapped LDL particles could be oxidized and eventually form a plague. The rupture of plague can induce the formation of thrombus (blood clot) and block blood flow. This will result in stroke or heart attack, depending on whether the blockage is in the brain or the heart.

Why HDL is Good

The size of HDL particles varies from 5 to 17 nm in diameter. They can penetrate the endothelium even more efficiently than LDL particles. However, they are less likely to be trapped in the intima, because the HDL particle contains mainly apolipoprotein A-I (ApoA-I) which does not bind to proteoglycans. Only a small amount of HDL particles may be trapped because they contain apolipoprotein E (ApoE) which can bind with proteoglycans.

Generally, LDL carries cholesterol from the liver to the rest of the body, while HDL carries cholesterol from the blood back to the liver. Not only can HDL remove the cholesterol in the blood, it also possesses anti-oxidant and anti-inflammatory properties to prevent atherosclerosis (reference).

II.1 Symptoms and Diagnosis

Because there are usually no signs or symptoms of high blood cholesterol, it is best to have cholesterol level checked regularly. A blood test called a lipoprotein profile will give the following information:

• Total cholesterol.
• LDL cholesterol.
• HDL cholesterol.
• Triglycerides: another form of fat in the blood.

Cholesterol levels are measured in milligrams (mg) of cholesterol per deciliter (dL) of blood.

Total Cholesterol Level	Total Cholesterol Category
Less than 200 mg/dL	Desirable
200-239 mg/dL	Borderline high
240 mg/dL and above	High
LDL Cholesterol Level	LDL Cholesterol Category
Less than 100 mg/dL	Optimal
100-129 mg/dL	Near optimal/above optimal
130-159 mg/dL	Borderline high
160-189 mg/dL	High
190 mg/dL and above	Very high
HDL Cholesterol Level	HDL Cholesterol Category
Less than 40 mg/dL	A major risk factor for heart disease
40-59 mg/dL	The higher, the better
60 mg/dL and above	Considered protective against heart disease

Triglycerides can also raise the risk for heart disease.  150?99 mg/dL are borderline high; 200 mg/dL or more are high.

 II.2 Causes

Two factors may affect the cholesterol level in the blood: genetics and foods.

An inherited genetic condition (familial hypercholesterolemia) results in very high LDL cholesterol levels. It begins at birth, and may result in heart attack at an early age.

The following types of fats may raise the cholesterol level:

Saturated fats

Saturated fats raise total blood cholesterol level. They are found in meat, seafood, cheese, milk,  ice cream and egg yolks.

Trans fats

Trans fats are more harmful than saturated fats because they raise bad LDL and lower good HDL. They are produced by heating liquid vegetable oils in the presence of hydrogen (a process called hydrogenation). They are found in French fries, deep-fried chips and most margarines. 

II.3 Treatment

Lowering Cholesterol With Diets

In addition to limiting the amount of foods that are rich in saturated fats and trans fats, one can eat foods that are rich in unsaturated fats which increase HDL and decrease LDL. There are two categories of unsaturated fats: monounsaturated fats and polyunsaturated fats.

• Monounsaturated fats - found in canola, peanut, and olive oils.
• Polyunsaturated fats - found in fish, corn, and soybean. Omega-3 fatty acids are a type of fatty acid that is highly polyunsaturated. Fatty fish like mackerel, lake trout, herring, sardines, albacore tuna and salmon are rich in omega-3 fatty acids.

Lowering Cholesterol With Medicines

The five major types of cholesterol-lowering medicines are:

Statins

• Very effective in lowering LDL (bad) cholesterol levels
• Safe for most people
• Rare side effects to watch for are liver and muscle problems

Bile Acid Sequestrants

• Help lower LDL cholesterol levels
• Sometimes prescribed with statins
• Not usually prescribed as the only medicine to lower cholesterol

Nicotinic Acid

• Lowers LDL cholesterol and triglycerides, and raises HDL (good) cholesterol
• Should only be used under a doctor's supervision

Fibrates

• Lower triglycerides
• May increase HDL (good) cholesterol levels
• When used with a statin, may increase the chance of muscle problems

Ezetimibe

• Lowers LDL cholesterol
• May be used with statins or alone
• Acts within the intestine to block cholesterol absorption

 

III. Stroke

A stroke occurs when the blood supply to part of the brain is suddenly interrupted or when a blood vessel in the brain bursts, spilling blood into the spaces surrounding brain cells. Brain cells die when they no longer receive oxygen and nutrients from the blood or when they are damaged by sudden bleeding into or around the brain. Ischemia is the term used to describe the loss of oxygen and nutrients for brain cells when there is inadequate blood flow. Ischemia ultimately leads to infarction, the death of brain cells which are eventually replaced by a fluid-filled cavity (or infarct) in the injured brain.

Stroke is the third leading cause of death in the United States and a leading cause of serious, long-term disability in adults. About 600,000 new strokes are reported in the U.S. each year.

III.1 Symptoms and Diagnosis

The symptoms of stroke are distinct because they happen quickly:

• Sudden numbness or weakness of the face, arm, or leg (especially on one side of the body)
• Sudden confusion, trouble speaking or understanding speech
• Sudden trouble seeing in one or both eyes
• Sudden trouble walking, dizziness, loss of balance or coordination
• Sudden severe headache with no known cause

Physicians have several diagnostic techniques and imaging tools to help diagnose the cause of stroke quickly and accurately. The first step in diagnosis is a short neurological examination. 

When a possible stroke patient arrives at a hospital, a health care professional, usually a doctor or nurse, will ask the patient or a companion what happened and when the symptoms began. Blood tests, an electrocardiogram, and a brain scan, such as CT or MRI, will often be done.

 

III.2 Causes

There are two forms of stroke: ischemic - blockage of a blood vessel supplying the brain, and hemorrhagic - bleeding into or around the brain.

Ischemic Stroke

An ischemic stroke occurs when an artery supplying the brain with blood becomes blocked, suddenly decreasing or stopping blood flow and ultimately causing a brain infarction. This type of stroke accounts for approximately 80 percent of all strokes. Blood clots are the most common cause of artery blockage and brain infarction. The process of clotting is necessary and beneficial throughout the body because it stops bleeding and allows repair of damaged areas of arteries or veins. However, when blood clots develop in the wrong place within an artery they can cause devastating injury by interfering with the normal flow of blood. Problems with clotting become more frequent as people age.

Blood clots can cause ischemia and infarction in two ways. A clot that forms in a part of the body other than the brain can travel through blood vessels and become wedged in a brain artery. This free-roaming clot is called an embolus and often forms in the heart. A stroke caused by an embolus is called an embolic stroke. The second kind of ischemic stroke, called a thrombotic stroke, is caused by thrombosis, the formation of a blood clot in one of the cerebral arteries that stays attached to the artery wall until it grows large enough to block blood flow.

Ischemic strokes can also be caused by stenosis, or a narrowing of the artery due to the buildup of plaque (a mixture of fatty substances, including cholesterol and other lipids) and blood clots along the artery wall. Stenosis can occur in large arteries and small arteries and is therefore called large vessel disease or small vessel disease, respectively. When a stroke occurs due to small vessel disease, a very small infarction results, sometimes called a lacunar infarction, from the French word "lacune" meaning "gap" or "cavity."

The most common blood vessel disease that causes stenosis is atherosclerosis. In atherosclerosis, deposits of plaque build up along the inner walls of large and medium-sized arteries, causing thickening, hardening, and loss of elasticity of artery walls and decreased blood flow.

Hemorrhagic Stroke

In a healthy, functioning brain, neurons do not come into direct contact with blood. The vital oxygen and nutrients the neurons need from the blood come to the neurons across the thin 

walls of the cerebral capillaries. The glia (nervous system cells that support and protect neurons) form a blood-brain barrier, an elaborate meshwork that surrounds blood vessels and capillaries and regulates which elements of the blood can pass through to the neurons.

When an artery in the brain bursts, blood spews out into the surrounding tissue and upsets not only the blood supply but the delicate chemical balance neurons require to function. This is called a hemorrhagic stroke. Such strokes account for approximately 20 percent of all strokes.

Hemorrhage can occur in several ways. One common cause is a bleeding aneurysm, a weak or thin spot on an artery wall. Over time, these weak spots stretch or balloon out under high arterial pressure. The thin walls of these ballooning aneurysms can rupture and spill blood into the space surrounding brain cells.

Hemorrhage also occurs when arterial walls break open. Plaque-encrusted artery walls eventually lose their elasticity and become brittle and thin, prone to cracking. Hypertension, or high blood pressure, increases the risk that a brittle artery wall will give way and release blood into the surrounding brain tissue.

A person with an arteriovenous malformation (AVM) also has an increased risk of hemorrhagic stroke. AVMs are a tangle of defective blood vessels and capillaries within the brain that have thin walls and can therefore rupture.

Bleeding from ruptured brain arteries can either go into the substance of the brain or into the various spaces surrounding the brain. Intracerebral hemorrhage occurs when a vessel within the brain leaks blood into the brain itself. Subarachnoid hemorrhage is bleeding under the meninges, or outer membranes, of the brain into the thin fluid-filled space that surrounds the brain.

The subarachnoid space separates the arachnoid membrane from the underlying pia mater membrane. It contains a clear fluid (cerebrospinal fluid or CSF) as well as the small blood vessels that supply the outer surface of the brain. In a subarachnoid hemorrhage, one of the small arteries within the subarachnoid space bursts, flooding the area with blood and contaminating the cerebrospinal fluid. Since the CSF flows throughout the cranium, within the spaces of the brain, subarachnoid hemorrhage can lead to extensive damage throughout the brain. In fact, subarachnoid hemorrhage is the most deadly of all strokes.

Transient Ischemic Attacks

A transient ischemic attack (TIA), sometimes called a mini-stroke, starts just like a stroke but then resolves leaving no noticeable symptoms or deficits. The occurrence of a TIA is a warning that the person is at risk for a more serious and debilitating stroke. Of the approximately 50,000 Americans who have a TIA each year, about one-third will have an acute stroke sometime in the future. The addition of other risk factors compounds a person's risk for a recurrent stroke. The average duration of a TIA is a few minutes. For almost all TIAs, the symptoms go away within an hour. There is no way to tell whether symptoms will be

just a TIA or persist and lead to death or disability. The patient should assume that all stroke symptoms signal an emergency and should not wait to see if they go away.

 III.3 Treatment

Physicians have a wide range of therapies to choose from when determining a stroke patient's best therapeutic plan. The type of stroke therapy a patient should receive depends upon the stage of disease. Generally there are three treatment stages for stroke: prevention, therapy immediately after stroke, and post-stroke rehabilitation. Therapies to prevent a first or recurrent stroke are based on treating an individual's underlying risk factors for stroke, such as hypertension, atrial fibrillation, and diabetes, or preventing the widespread formation of blood clots that can cause ischemic stroke in everyone, whether or not risk factors are present. Acute stroke therapies try to stop a stroke while it is happening by quickly dissolving a blood clot causing the stroke or by stopping the bleeding of a hemorrhagic stroke. The purpose of post-stroke rehabilitation is to overcome disabilities that result from stroke damage.

Therapies for stroke include medications, surgery, or rehabilitation.

Medications

Medication or drug therapy is the most common treatment for stroke. The most popular classes of drugs used to prevent or treat stroke are antithrombotics (antiplatelet agents and anticoagulants) and thrombolytics.

Antithrombotics prevent the formation of blood clots that can become lodged in a cerebral artery and cause strokes. Antiplatelet drugs prevent clotting by decreasing the activity of platelets, blood cells that contribute to the clotting property of blood. These drugs reduce the risk of blood-clot formation, thus reducing the risk of ischemic stroke. In the context of stroke, physicians prescribe antiplatelet drugs mainly for prevention. The most widely known and used antiplatelet drug is aspirin. Other antiplatelet drugs include clopidogrel, ticlopidine, and dipyridamole.

Anticoagulants reduce stroke risk by reducing the clotting property of the blood. The most commonly used anticoagulants include warfarin (also known as Coumadin), heparin, and enoxaparin (also known as Lovenox).

Thrombolytic agents are used to treat an ongoing, acute ischemic stroke caused by an artery blockage. These drugs halt the stroke by dissolving the blood clot that is blocking blood flow to the brain. Recombinant tissue plasminogen activator (rt-PA) is a genetically engineered form of t-PA, a thombolytic substance made naturally by the body. It can be effective if given intravenously within 3 hours of stroke symptom onset, but it should be used only after a physician has confirmed that the patient has suffered an ischemic stroke. Thrombolytic agents can increase bleeding and therefore must be used only after careful patient screening.

Surgery

Surgery can be used to prevent stroke, to treat acute stroke, or to repair vascular damage or malformations in and around the brain. There are two prominent types of surgery for stroke prevention and treatment: carotid endarterectomy and extracranial/intracranial (EC/IC) bypass.

Carotid endarterectomy is a surgical procedure in which a doctor removes fatty deposits (plaque) from the inside of one of the carotid arteries, which are located in the neck and are the main suppliers of blood to the brain. As mentioned earlier, the disease atherosclerosis is characterized by the buildup of plaque on the inside of large arteries, and the blockage of an artery by this fatty material is called stenosis. The NINDS has sponsored two large clinical trials to test the efficacy of carotid endarterectomy: the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and the Asymptomatic Carotid Atherosclerosis Trial (ACAS). These trials showed that carotid endarterectomy is a safe and effective stroke prevention therapy for most people with greater than 50 percent stenosis of the carotid arteries when performed by a qualified and experienced neurosurgeon or vascular surgeon.

Currently, the NINDS is sponsoring the Carotid Revascularization Endarterectomy vs. Stenting Trial (CREST), a large clinical trial designed to test the effectiveness of carotid endarterectomy versus a newer surgical procedure for carotid stenosis called stenting. The procedure involves inserting a long, thin catheter tube into an artery in the leg and threading the catheter through the vascular system into the narrow stenosis of the carotid artery in the neck. Once the catheter is in place in the carotid artery, the radiologist expands the stent with a balloon on the tip of the catheter. The CREST trial will test the effectiveness of the new surgical technique versus the established standard technique of carotid endarterectomy surgery.

EC/IC bypass surgery is a procedure that restores blood flow to a blood-deprived area of brain tissue by rerouting a healthy artery in the scalp to the area of brain tissue affected by a blocked artery. The NINDS-sponsored EC/IC Bypass Study tested the ability of this surgery to prevent recurrent strokes in stroke patients with atherosclerosis. The study showed that, in the long run, EC/IC does not seem to benefit these patients. The surgery is still performed occasionally for patients with aneurysms, some types of small artery disease, and certain vascular abnormalities.

One useful surgical procedure for treatment of brain aneurysms that cause subarachnoid hemorrhage is a technique called "clipping." Clipping involves clamping off the aneurysm from the blood vessel, which reduces the chance that it will burst and bleed.

A new therapy that is gaining wide attention is the detachable coil technique for the treatment of high-risk intracranial aneurysms. A small platinum coil is inserted through an artery in the thigh and threaded through the arteries to the site of the aneurysm. The coil is then released into the aneurysm, where it evokes an immune response from the body. The body produces a blood clot inside the aneurysm, strengthening the artery walls and reducing the risk of rupture. Once the aneurysm is stabilized, a neurosurgeon can clip the aneurysm with less risk of hemorrhage and death to the patient.

Rehabilitation Therapy

Stroke is the number one cause of serious adult disability in the United States. Stroke disability is devastating to the stroke patient and family, but therapies are available to help rehabilitate post-stroke patients.

For most stroke patients, physical therapy (PT) is the cornerstone of the rehabilitation process. A physical therapist uses training, exercises, and physical manipulation of the stroke patient's body with the intent of restoring movement, balance, and coordination. The aim of PT is to have the stroke patient relearn simple motor activities such as walking, sitting, standing, lying down, and the process of switching from one type of movement to another.

Another type of therapy involving relearning daily activities is occupational therapy (OT). OT also involves exercise and training to help the stroke patient relearn everyday activities such as eating, drinking, dressing, bathing, cooking, reading and writing, and toileting. The goal of OT is to help the patient become independent or semi-independent.

Speech and language problems arise when brain damage occurs in the language centers of the brain. Due to the brain's great ability to learn and change (called brain plasticity), other areas can adapt to take over some of the lost functions. Speech language pathologists help stroke patients relearn language and speaking skills, including swallowing, or learn other forms of communication. Speech therapy is appropriate for any patients with problems understanding speech or written words, or problems forming speech. A speech therapist helps stroke patients help themselves by working to improve language skills, develop alternative ways of communicating, and develop coping skills to deal with the frustration of not being able to communicate fully. With time and patience, a stroke survivor should be able to regain some, and sometimes all, language and speaking abilities.

Many stroke patients require psychological or psychiatric help after a stroke. Psychological problems, such as depression, anxiety, frustration, and anger, are common post-stroke disabilities. Talk therapy, along with appropriate medication, can help alleviate some of the mental and emotional problems that result from stroke. Sometimes it is also beneficial for family members of the stroke patient to seek psychological help as well.

 IV. Heart Attack

A heart attack occurs when the supply of blood and oxygen to an area of heart muscle is blocked, usually by a clot in a coronary artery. If treatment is not started quickly, the affected area of heart muscle begins to die. This injury to the heart muscle can lead to serious complications, and can even be fatal. Sudden death from heart attack is most often due to an arrhythmia (irregular heartbeat or rhythm) called ventricular fibrillation. If a person survives a heart attack, the injured area of the heart muscle is replaced by scar tissue. This weakens the pumping action of the heart and can lead to heart failure and other complications.

Effective treatments for heart attack are available that can decrease the chances of sudden death and long-term complications. To be most effective, these treatments must be given fast—within 1 hour of the start of heart attack symptoms. Acting fast can save your life and limit damage to your heart.

 

Figure A is an overview of the heart and coronary artery showing damage (dead heart muscle) caused by a heart attack. Figure B shows a cross-section of the coronary artery with plaque buildup and a blood clot.

A heart attack is a life-threatening event. Everyone should know the warning signs of a heart attack and how to get emergency help. Many people suffer permanent damage to their hearts or die because they do not get help immediately.

Each year, more than a million persons in the United States have a heart attack, and about half (515,000) of them die. About one-half of those who die do so within 1 hour of the start of symptoms and before reaching the hospital.

Both men and women have heart attacks.

Emergency personnel can often stop arrhythmias with emergency cardiopulmonary resuscitation (CPR), defibrillation (electrical shock), and prompt advanced cardiac life support procedures. If care is sought soon enough, blood flow in the blocked artery can be restored in time to prevent permanent damage to the heart. Most people, however, do not seek medical care for 2 hours or more after symptoms begin. Many people wait 12 hours or longer.

 IV.1 Symptoms and Diagnosis

Symptoms

The warning signs and symptoms of a heart attack can include:

• Chest discomfort. Most heart attacks involve discomfort in the center of the chest that lasts for more than a few minutes or goes away and comes back. The discomfort can feel like uncomfortable pressure, squeezing, fullness, or pain. Heart attack pain can sometimes feel like indigestion or heartburn.
• Discomfort in other areas of the upper body. Pain, discomfort, or numbness can occur in one or both arms, the back, neck, jaw, or stomach.
• Shortness of breath. Difficulty in breathing often comes along with chest discomfort, but it may occur before chest discomfort.
• Other symptoms. Examples include breaking out in a cold sweat, having nausea and vomiting, or feeling light-headed or dizzy.

Signs and symptoms vary from person to person. In fact, if you have a second heart attack, your symptoms may not be the same as for the first heart attack. Some people have no symptoms. This is called a "silent" heart attack.

The symptoms of angina (chest pain) can be similar to the symptoms of a heart attack. If you have angina and notice a change or a worsening of your symptoms, talk with your doctor right away.

Diagnosis

Diagnosis of a heart attack may include the following tests:

• EKG (electrocardiogram). This test is used to measure the rate and regularity of your heartbeat. A 12-lead EKG is used in diagnosing a heart attack.
• Blood tests. When cells in the heart die, they release enzymes into the blood. These enzymes are called markers or biomarkers. Measuring the amount of these markers in the blood can show how much damage was done to your heart. These tests are often repeated at intervals to check for changes. The specific blood tests are:
• Troponin test. This test checks the troponin levels in the blood. This blood test is considered the most accurate to see if a heart attack has occurred and how much damage it did to the heart.
• CK or CK-MB test. These tests check for the amount of the different forms of creatine kinase in the blood.
• Myoglobin test. This test checks for the presence of myoglobin in the blood. Myoglobin is released when the heart or other muscle is injured.
• Nuclear heart scan. This test uses radioactive tracers (technetium or thallium) to outline heart chambers and major blood vessels leading to and from the heart. A nuclear heart scan shows any damage to your heart muscle.
• Cardiac catheterization. A thin, flexible tube (catheter) is passed through an artery in the groin (upper thigh) or arm to reach the coronary arteries. Your doctor can use the catheter to determine pressure and blood flow in the heart's chambers, collect blood samples from the heart, and examine the arteries of the heart by x ray.
• Coronary angiography. This test is usually performed along with cardiac catheterization. A dye that can be seen by using x ray is injected through the catheter into the coronary arteries. Your doctor can see the flow of blood through the heart and see where there are blockages.

 IV.2 Causes

Most heart attacks are caused by a blood clot that blocks one of the coronary arteries (the blood vessels that bring blood and oxygen to the heart muscle). When blood cannot reach part of your heart, that area starves for oxygen. If the blockage continues long enough, cells in the affected area die.

Coronary artery disease (CAD) is the most common underlying cause of a heart attack. CAD is the hardening and narrowing of the coronary arteries by the buildup of plaque in the inside walls (see Atherosclerosis). Over time, plaque buildup in the coronary arteries can:

• Narrow the arteries so that less blood flows to the heart muscle
• Block completely the arteries and the flow of blood
• Cause blood clots to form and block the arteries

A less common cause of heart attacks is a severe spasm (tightening) of the coronary artery that cuts off blood flow to the heart. These spasms can occur in persons with or without CAD. Artery spasm can sometimes be caused by:

• Taking certain drugs, such as cocaine
• Emotional stress
• Exposure to cold
• Cigarette smoking

IV.3 Treatment

A heart attack is a medical emergency. Delaying treatment can mean lasting damage to your heart or even death. The sooner treatment begins, the better your chances of recovering. Your treatment may begin in the ambulance or in the emergency room and continue in a special area called a cardiac care unit (CCU).

Immediate Treatment in the Hospital

If you are having a heart attack, doctors will:

• Work quickly to restore blood flow to the heart
• Continuously monitor your vital signs to detect and treat complications

Restoring blood flow to the heart is vital to prevent or limit damage to the heart muscle and to prevent another heart attack. The main treatments are the use of thrombolytic (clot-busting) drugs and procedures such as angioplasty.

• Thrombolytic drugs (clot busters) are used to dissolve blood clots that are blocking blood flow to the heart. When given soon after a heart attack begins, these drugs can prevent or limit permanent damage to the heart. To be most effective, these drugs must be given within 1 hour after the start of heart attack symptoms.
• Angioplasty procedures are used to open blocked or narrowed coronary arteries. A tiny metal mesh tube, called a stent, may be placed in the artery to help keep it open.
• Coronary artery bypass surgery uses arteries or veins from other areas in your body to bypass your blocked coronary arteries.

The CCU is specially equipped with monitors that continuously measure your vital signs. Those that can show signs of complications include:

• EKG (electrocardiogram), which detects problems with the heart rhythm or function
• A blood pressure monitor
• Pulse oximetry, which measures the amount of oxygen in the blood and provides an early warning sign of a low level of oxygen in the blood

Medicines

Several kinds of medicines can be used in treating heart attacks:

• Beta blockers decrease the workload on your heart by slowing your heart rate. This makes your heart beat with less force and lowers your blood pressure. Some beta blockers are also used to relieve angina (chest pain), and they are used in heart attack patients to help prevent additional heart attacks. Beta blockers are also used to correct irregular heartbeat.
• Angiotensin-converting enzyme (ACE) inhibitors lower blood pressure and reduce the strain on your heart. These medicines are used in some patients after a heart attack to increase survival rate and help slow down further weakening of the heart.
• Nitrates, such as nitroglycerin, relax blood vessels and stop chest pain.
• Anticoagulants thin the blood and prevent clots from forming in your arteries.
• Antiplatelet medicines (such as aspirin and clopidigrel) stop platelets from clumping together to form clots. These medicines are given to people who have had a heart attack, have angina, or experience angina after angioplasty.
• Glycoprotein IIb-IIIa inhibitors are potent antiplatelet medicines given intravenously to prevent clots from forming in your arteries.
• Other medicines may be given to relieve pain and anxiety.
• Some medicines treat arrhythmias (irregular heart rhythms) that often occur during a heart attack.

Oxygen therapy also may be given while you are in the hospital.

Long-Term Treatment

The length of your hospital stay after a heart attack depends on your condition and response to treatment. Most people spend several days in the hospital after a heart attack. While you are in the hospital, your heart will be monitored, and you will receive needed medicines. You will probably have further testing, and you will be treated for any complications that arise.

While you are still in the hospital or after you go home after your heart attack, your doctor may order other tests, such as:

• Echocardiogram. In this test, ultrasound is used to make an image of your heart that can be seen on a video monitor. It shows how well the heart is filling with blood and pumping it to the rest of the body.
• Exercise stress test. Some heart problems are easier to diagnose when the heart is working hard and beating fast. During stress testing, a patient exercises, or is given medicine, to make the heart work harder and beat fast while heart tests are performed. During exercise stress testing, blood pressure and EKG readings are monitored while the patient runs on a treadmill or pedals a bicycle.
• In addition to an EKG, other heart tests, such as nuclear heart scanning or echocardiography, can also be done at the same time. During nuclear heart scanning, radioactive dye is injected into the bloodstream, and a special camera shows the flow of blood to the heart muscle. If a person is unable to exercise, a medicine can be injected into the bloodstream to make the heart work harder and beat fast. Nuclear heart scanning or echocardiography is then done.
• Two newer tests that are being done with stress testing are magnetic resonance imaging (MRI) and positron emission tomography (PET) scanning of the heart. MRI shows detailed images of the structures and beating of the heart. PET scanning shows blood flow to the heart muscle and areas of damaged heart muscle.

After You Leave the Hospital

After a heart attack, your treatment may include cardiac rehabilitation (see section below) in the first weeks or months, checkups and tests, lifestyle changes, and medicines. You will need to see your doctor for checkups and tests to see how your heart is doing. Your doctor will most likely recommend lifestyle changes, such as quitting smoking, losing weight, changing your diet, or increasing your physical activity.

After a heart attack, most people take daily medicines that may include:

• Aspirin
• Medicines to lower cholesterol or blood pressure
• Other medicines to help reduce the heart's workload

Always take medicines as your doctor directs.

Cardiac rehabilitation

Your doctor may prescribe cardiac rehabilitation (rehab) to help you recover from a heart attack and to help prevent another heart attack. Almost everyone who has survived a heart attack can benefit from rehab.

The cardiac rehab team may include:

• Doctors
• Your family doctor
• A heart specialist
• A surgeon
• Nurses
• Exercise specialists
• Physical therapists and occupational therapists
• Dietitians
• Psychologists or other behavior therapists

Rehab has two parts:

• Exercise training helps you learn how to exercise safely, strengthen your muscles, and improve your stamina. Your exercise plan will be based on your individual ability, needs, and interests.
• Education, counseling, and training help you to understand your heart condition and find ways to reduce your risk of future heart problems. The cardiac rehab team will help you learn how to cope with the stress of adjusting to a new lifestyle and to deal with your fears about the future.                                                                                                                                                                                                                                                                               * (References: internet and books)