Myocardial Infarction

•  Refers to a dynamic process by which one or more regions of the heart muscle experience a severe and prolonged decrease in oxygen supply because of insufficient coronary blood flow. The affected muscle tissue subsequently becomes necrotic.
• Onset of Myocardial Infarction may be sudden or gradual, and the process takes 3 to 6 hours to run its course.
• It is the most serious manifestation of acute coronary syndrome, a complication of coronary artery disease (CAD).
• Approximately 90% of Myocardial Infarction are precipitated by acute coronary thrombosis (partial or total) secondary to severe CAD (greater than 70% narrowing of the artery).
• Other causative factors include coronary artery spasm, coronary artery embolism, infectious diseases causing arterial inflammation, hypoxia, anemia, and severe exertion or stress on the heart in the presence of significant coronary artery disease.

Explore Atrial Fibrillation

What Is Atrial Fibrillation?

Atrial fibrillation (A-tre-al fi-bri-LA-shun), or AF, is the most common type of arrhythmia (ah-RITH-me-ah). An arrhythmia is a problem with the rate or rhythm of the heartbeat. During an arrhythmia, the heart can beat too fast, too slow, or with an irregular rhythm.

AF occurs if rapid, disorganized electrical signals cause the heart's two upper chambers—called the atria (AY-tree-uh)—to fibrillate. The term "fibrillate" means to contract very fast and irregularly.

In AF, blood pools in the atria. It isn't pumped completely into the heart's two lower chambers, called the ventricles (VEN-trih-kuls). As a result, the heart's upper and lower chambers don't work together as they should.

People who have AF may not feel symptoms. However, even when AF isn't noticed, it can increase the risk of stroke. In some people, AF can cause chest pain or heart failure, especially if the heart rhythm is very rapid.

AF may happen rarely or every now and then, or it may become an ongoing or long-term heart problem that lasts for years.

Understanding the Electrical Problem in Atrial Fibrillation

In AF, the heart's electrical signals don't begin in the SA node. Instead, they begin in another part of the atria or in the nearby pulmonary veins. The signals don't travel normally. They may spread throughout the atria in a rapid, disorganized way. This can cause the atria to fibrillate.

The faulty signals flood the AV node with electrical impulses. As a result, the ventricles also begin to beat very fast. However, the AV node can't send the signals to the ventricles as fast as they arrive. So, even though the ventricles are beating faster than normal, they aren't beating as fast as the atria.

Thus, the atria and ventricles no longer beat in a coordinated way. This creates a fast and irregular heart rhythm. In AF, the ventricles may beat 100 to 175 times a minute, in contrast to the normal rate of 60 to 100 beats a minute.

If this happens, blood isn't pumped into the ventricles as well as it should be. Also, the amount of blood pumped out of the ventricles to the body is based on the random atrial beats.

The body may get rapid, small amounts of blood and occasional larger amounts of blood. The amount will depend on how much blood has flowed from the atria to the ventricles with each beat.

Most of the symptoms of AF are related to how fast the heart is beating. If medicines or age slow the heart rate, the symptoms are minimized.

AF may be brief, with symptoms that come and go and end on their own. Or, the condition may be ongoing and require treatment. Sometimes AF is permanent, and medicines or other treatments can't restore a normal heart rhythm.

The animation below shows atrial fibrillation. Click the "start" button to play the animation. Written and spoken explanations are provided with each frame. Use the buttons in the lower right corner to pause, restart, or replay the animation, or use the scroll bar below the buttons to move through the frames.

Types of Atrial Fibrillation

Paroxysmal Atrial Fibrillation

In paroxysmal (par-ok-SIZ-mal) atrial fibrillation (AF), the faulty electrical signals and rapid heart rate begin suddenly and then stop on their own. Symptoms can be mild or severe. They stop within about a week, but usually in less than
24 hours.

Persistent Atrial Fibrillation

Persistent AF is a condition in which the abnormal heart rhythm continues for more than a week. It may stop on its own, or it can be stopped with treatment.

Permanent Atrial Fibrillation

Permanent AF is a condition in which a normal heart rhythm can't be restored with treatment. Both paroxysmal and persistent AF may become more frequent and, over time, result in permanent AF.

What Causes Atrial Fibrillation?

Atrial fibrillation (AF) occurs if the heart's electrical signals don't travel through the heart in a normal way. Instead, they become very rapid and disorganized.

Damage to the heart's electrical system causes AF. The damage most often is the result of other conditions that affect the health of the heart, such as high blood pressure and coronary heart disease.

The risk of AF increases as you age. Inflammation also is thought to play a role in causing AF.

Sometimes, the cause of AF is unknown.

What Are the Signs and Symptoms of Atrial Fibrillation?

Atrial fibrillation (AF) usually causes the heart's lower chambers, the ventricles, to contract faster than normal.

When this happens, the ventricles can't completely fill with blood. Thus, they may not be able to pump enough blood to the lungs and body. This can lead to signs and symptoms, such as:

• Palpitations (feelings that your heart is skipping a beat, fluttering, or beating too hard or fast)


• Shortness of breath


• Weakness or problems exercising


• Chest pain


• Dizziness or fainting


• Fatigue (tiredness)


• Confusion

Atrial Fibrillation Complications

AF has two major complications—stroke and heart failure.

Stroke

During AF, the heart's upper chambers, the atria, don't pump all of their blood to the ventricles. Some blood pools in the atria. When this happens, a blood clot (also called a thrombus) can form.

If the clot breaks off and travels to the brain, it can cause a stroke. (A clot that forms in one part of the body and travels in the bloodstream to another part of the body is called an embolus.)

Blood-thinning medicines that reduce the risk of stroke are an important part of treatment for people who have AF.

Atrial Fibrillation and Stroke

The illustration shows how a stroke can occur during atrial fibrillation. A blood clot (thrombus) can form in the left atrium of the heart. If a piece of the clot breaks off and travels to an artery in the brain, it can block blood flow through the artery. The lack of blood flow to the portion of the brain fed by the artery causes a stroke.

Heart Failure

Heart failure occurs if the heart can't pump enough blood to meet the body's needs. AF can lead to heart failure because the ventricles are beating very fast and can't completely fill with blood. Thus, they may not be able to pump enough blood to the lungs and body.

Fatigue and shortness of breath are common symptoms of heart failure. A buildup of fluid in the lungs causes these symptoms. Fluid also can build up in the feet, ankles, and legs, causing weight gain.

Lifestyle changes, medicines, and procedures or surgery (rarely, a mechanical heart pump or heart transplant) are the main treatments for heart failure.

Marfan syndrome

Marfan syndrome is a disorder of connective tissue, the tissue that strengthens the body's structures.

Disorders of connective tissue affect the skeletal system, cardiovascular system, eyes, and skin.

Causes, incidence, and risk factors

Marfan syndrome is caused by defects in a gene called fibrillin-1. Fibrillin-1 plays an important role as the building block for connective tissue in the body.

The gene defect also causes too much growth of the long bones of the body. This causes the tall height and long arms and legs seen in people with this syndrome. How this overgrowth happens is not well understood.

Other areas of the body that are affected include:

• Lung tissue (there may be a pneumothorax, in which air can escape from the lung into the chest cavity and collapse the lung)


• The aorta, the main blood vessel that takes blood from the heart to the body may stretch or become weak (called aortic dilation or aortic aneurysm)


• The eyes, causing cataracts and other problems (such as a dislocation of the lenses)


• The skin


• Tissue covering the spinal cord

In most cases, Marfan syndrome is inherited, which means it is passed down through families. However, up to 30% of patients have no family history, which is called "sporadic." In sporadic cases, the syndrome is believed to be caused by a new gene change.

Symptoms

People with Marfan syndrome are usually tall with long, thin arms and legs and spider-like fingers -- called arachnodactyly. When they stretch out their arms, the length of their arms is greater than their height.

Other symptoms include:

• A chest that sinks in or sticks out -- funnel chest (pectus excavatum) or pigeon breast (pectus carinatum)


• Flat feet


• Highly arched palate and crowded teeth


• Hypotonia


• Joints that are too flexible (but the elbows may be less flexible)


• Learning disability


• Movement of the lens of the eye from its normal position (dislocation)


• Nearsightedness


• Small lower jaw (micrognathia)


• Spine that curves to one side (scoliosis)


• Thin, narrow face

Signs and tests

The doctor will perform a physical exam. There may be hypermobile joints and signs of:

• Aneurysm


• Collapsed lung


• Heart valve problems

An eye exam may show:

• Defects of the lens or cornea


• Retinal detachment


• Vision problems

The following tests may be performed:

• Echocardiogram


• Fibrillin-1 mutation testing (in some people)

An echocardiogram should be done every year to look at the base of the aorta.

Treatment

Vision problems should be treated when possible.

Monitor for scoliosis, especially during the teenage years.

Medicine to slow the heart rate may help prevent stress on the aorta. Avoid participating in contact sports to avoid injuring the aorta of the heart. Some people may need surgery to replace the aortic root and valve.

People with Marfan syndrome who have heart valve conditions should take antibiotics before dental procedures to prevent endocarditis. Pregnant women with Marfan syndrome must be monitored very closely because of the increased stress on the heart and aorta.

Support Groups

National Marfan Foundation -- www.marfan.org

Expectations (prognosis)

Heart-related complications may shorten the lifespan of people with this disease. However, many patients survive well into their 60s. Good care and surgery may extend the lifespan further.

Complications

Complications may include:

• Aortic regurgitation


• Aortic rupture


• Bacterial endocarditis


• Dissecting aortic aneurysm


• Enlargement of the base of the aorta


• Heart failure


• Mitral valve prolapse


• Scoliosis


• Vision problems

Calling your health care provider

Experts recommend genetic counseling for couples with a history of this syndrome who wish to have children.

Prevention

Spontaneous new gene mutations leading to Marfan (less than 1/3 of cases) cannot be prevented. If you have Marfan syndrome, see your doctor at least once every year.

36 Interesting Facts About . . . The Human Heart

1. The average adult heart beats 72 times a minute; 100,000 times a day; 3,600,000 times a year; and 2.5 billion times during a lifetime.


2. Though weighing only 11 ounces on average, a healthy heart pumps 2,000 gallons of blood through 60,000 miles of blood vessels each day.


3. A kitchen faucet would need to be turned on all the way for at least 45 years to equal the amount of blood pumped by the heart in an average lifetime.


4. The volume of blood pumped by the heart can vary over a wide range, from five to 30 liters per minute.


5. Every day, the heart creates enough energy to drive a truck 20 miles. In a lifetime, that is equivalent to driving to the moon and back.


6. Because the heart has its own electrical impulse, it can continue to beat even when separated from the body, as long as it has an adequate supply of oxygen.


7. The fetal heart rate is approximately twice as fast as an adult’s, at about 150 beats per minute. By the time a fetus is 12 weeks old, its heart pumps an amazing 60 pints of blood a day.


8. The heart pumps blood to almost all of the body’s 75 trillion cells. Only the corneas receive no blood supply.

1. In 1903, physiologist Willem Einthoven (1860-1927) invented the electrocardiograph, which measures electric current in the heartFive percent of blood supplies the heart, 15-20% goes to the brain and central nervous system, and 22% goes to the kidneys.


2. The “thump-thump” of a heartbeat is the sound made by the four valves of the heart closing.


3. The heart does the most physical work of any muscle during a lifetime. The power output of the heart ranges from 1-5 watts. While the quadriceps can produce 100 watts for a few minutes, an output of one watt for 80 years is equal to 2.5 gigajoules.


4. The heart begins beating at four weeks after conception and does not stop until death.


5. A newborn baby has about one cup of blood in circulation. An adult human has about four to five quarts which the heart pumps to all the tissues and to and from the lungs in about one minute while beating 75 times.


6. The heart pumps oxygenated blood through the aorta (the largest artery) at about 1 mile (1.6 km) per hour. By the time blood reaches the capillaries, it is moving at around 43 inches (109 cm) per hour.


7. Early Egyptians believed that the heart and other major organs had wills of their own and would move around inside the body.


8. An anonymous contributor to the Hippocratic Collection (or Canon) believed vessel valves kept impurities out of the heart, since the intelligence of man was believed to lie in the left cavity.


9. Plato theorized that reasoning originated with the brain, but that passions originated in the “fiery” heart.


10. The term “heartfelt” originated from Aristotle’s philosophy that the heart collected sensory input from the peripheral organs through the blood vessels. It was from those perceptions that thought and emotions arose.


11. Prolonged lack of sleep can cause irregular jumping heartbeats called premature ventricular contractions (PVCs).


12. Some heavy snorers may have a condition called obtrusive sleep apnea (OSA), which can negatively affect the heart.


13. Cocaine affects the heart’s electrical activity and causes spasm of the arteries, which can lead to a heart attack or stroke, even in healthy people.


14. Galen of Pergamum, a prominent surgeon to Roman gladiators, demonstrated that blood, not air, filled arteries, as Hippocrates had concluded. However, he also believed that the heart acted as a low-temperature oven to keep the blood warm and that blood trickled from one side of the heart to the other through tiny holes in the heart.


15. Galen agreed with Aristotle that the heart was the body’s source of heat, a type of “lamp” fueled by blood from the liver and fanned into spirituous flame by air from the lungs. The brain merely served to cool the blood.


16. In 1929, German surgeon Werner Forssmann (1904-1979) examined the inside of his own heart by threading a catheter into his arm vein and pushing it 20 inches and into his heart, inventing cardiac catheterization, a now common procedure.


17. On December 3, 1967, Dr. Christiaan Barnard (1922-2001) of South Africa transplanted a human heart into the body of Louis Washansky. Although the recipient lived only 18 days, it is considered the first successful heart transplant.


18. “Atrium” is Latin for “entrance hall,” and “ventricle” is Latin for “little belly.”


19. A woman’s heart typically beats faster than a man’s. The heart of an average man beats approximately 70 times a minute, whereas the average woman has a heart rate of 78 beats per minute.


20. Blood is actually a tissue. When the body is at rest, it takes only six seconds for the blood to go from the heart to the lungs and back, only eight seconds for it to go the brain and back, and only 16 seconds for it to reach the toes and travel all the way back to the heart.


21. French physician Rene Laennec (1781-1826) invented the stethoscope when he felt it was inappropriate to place his ear on his large-buxomed female patients' chests.


22. Physician Erasistratus of Chios (304-250 B.C.) was the first to discover that the heart functioned as a natural pump.


23. In his text De Humani Corporis Fabrica Libri Septem, the father of modern anatomy, Andreas Vesalius (1514-1564), argued that the blood seeped from one ventricle to another through mysterious pores.


24. Galen argued that the heart constantly produced blood. However, William Harvey’s (1578-1657) discovery of the circulation system in 1616 revealed that there was a finite amount of blood in the body and that it circulated in one direction.


25. The right atrium holds about 3.5 tablespoons of blood. The right ventricle holds slightly more than a quarter cup of blood. The left atrium holds the same amount of blood as the right, but its walls are three times thicker.


26. Grab a tennis ball and squeeze it tightly: that’s how hard the beating heart works to pump blood.