Heart attack Causes and signs.

 Heart attack Causes and signs.

Every year, nearly 735,000 Americans have a heart attack. In fact, it is estimated that every 34 seconds someone suffers a heart attack in the United States. In patients who have a heart attack and arrive at the hospital quickly, advances in treatment have reduced the number of deaths due to heart attacks. Today, patients who recover after a heart attack are more likely than ever to regain their previous health.

 

What Causes a Heart Attack?

Many heart attacks or myocardial infarctions (MI) are caused by a complete blockage of a blood vessel in the heart called the "coronary artery." The blockage of the coronary artery prevents blood rich in oxygen and nutrients from reaching a section of the heart. If blood cannot reach the heart muscle, it will die. If medical treatment is obtained immediately, the damage can be reduced, but if a section of the heart muscle dies, the damage is irreversible.

 

Heart attacks can be caused by:

 

A buildup of fat called "plaque" significantly blocks or narrows a coronary artery. The blockage cuts off blood flow to the section of heart muscle fed by the artery.

A blood clot that blocks a narrowed artery by plaque. The clot can originate in another part of the body and be carried through the bloodstream to the narrowed artery.

A clot that forms in an area of ​​soft plaque inside the artery. This plaque, covered by a thin fibrous layer, is called a vulnerable plaque. When vulnerable plaque ruptures, it can lead to the formation of a blood clot. The clot can block blood flow to the section of heart muscle fed by the artery.

A spasm of a coronary artery, which is a contraction that momentarily narrows the coronary artery. This narrowing hinders or interrupts blood flow to certain parts of the heart muscle, but it can occur in both arteries that have plaque build-up and those that do not.

Heart attacks are divided into two types based on their severity. The most serious type of heart attack is called an "acute ST-segment elevation myocardial infarction" or STEMI. In a STEMI, the coronary artery is completely blocked by a blood clot, so all of the heart muscle that normally receives blood from the affected artery begins to die.

 

Doctors can determine if a person has a STEMI because of the characteristic abnormalities seen on the electrocardiogram (ECG). One such alteration is ST-segment elevation. This elevation indicates that a large amount of the heart muscle has been injured. The name of this type of heart attack is due to the elevation of the ST segment.

 

In a “non-ST-segment elevation myocardial infarction” or STEMI, the coronary artery is only partially obstructed, so that only part of the heart muscle supplied by the affected artery can be injured. A STEMI does not produce ST-segment elevation on the electrocardiogram. For this reason, doctors sometimes have a hard time determining whether a person is having a heart attack or an episode of angina.

 

What are the symptoms of a heart attack?

The major symptoms of a heart attack are

• Chest pain or discomfort. Most heart attacks involve discomfort in the center or left side of the chest that lasts for more than a few minutes or that goes away and comes back. The discomfort can feel like uncomfortable pressure, squeezing, fullness, or pain.
• Feeling weak, light-headed, or faint. You may also break out into a cold sweat.
• Pain or discomfort in the jaw, neck, or back.
• Pain or discomfort in one or both arms or shoulders.
• Shortness of breath. This often comes along with chest discomfort, but shortness of breath also can happen before chest discomfort.

The onset of a heart attack usually manifests itself as sudden, severe pain in the chest that patients often describe as a feeling of pressure, as if something is crushing or squeezing their chest, or as if they are weighing heavily on it. The pain can spread to the arm, jaw, shoulder, back, or neck. Other possible symptoms include shortness of breath, confusion, dizziness, lightheadedness, sweating, or nausea of ​​unknown origin.

Not all have the classic symptoms. Some people feel a burning sensation, similar to indigestion or heartburn, and the pain may be concentrated in a small area of ​​the chest. Some patients do not feel any symptoms.

 

Heart attack symptoms in women may be different from those in men. Many women who have a heart attack don't know it. Women often feel burning in the upper abdomen and may have dizziness, an upset stomach, and sweating. Because they may not feel the typical pain in the left half of the chest, many women may miss the symptoms that indicate that they are having a heart attack.

 Heart   Attack   Warning    Signs.

 

How is a heart attack diagnosed?

In addition to talking with you and checking your pulse and blood pressure, the emergency room staff will usually do the following tests. An electrocardiogram (ECG) to determine which of the coronary arteries is blocked and monitor your heart rhythm.

A blood test to determine how much damage has occurred by detecting certain enzymes that pass from injured heart muscle cells into the bloodstream. The enzymes that are generally tried to detect are CK-MB (the myocardial band of the enzyme creatine kinase), myoglobin, and cardiac troponins T and I, which are released into the bloodstream when the heart muscle is damaged. They may also try to detect the levels of fibrinogen and C-reactive protein (CRP) in the bloodstream.

A chest x-ray to determine if your heart is enlarged or if there is fluid in your lungs. When it has stabilized, doctors may order further tests to determine how much damage your heart has suffered.

 

A thallium stress test, a nuclear medicine study, involves injecting a radioactive substance into the bloodstream to see how the blood flows through the arteries. This study can determine if parts of the heart muscle are damaged or dead, or if an artery is significantly narrowed.

An echocardiogram, which allows determining if the heart muscle is damaged, by studying the movement of the lower-left chamber (the left ventricle). A measurement that is typically taken during an echocardiogram is the left ventricular ejection fraction or LVEF of the heart. During a heartbeat, which is a two-phase pumping action, the heart contracts and relaxes. When the heart contracts, it ejects (or ejects) blood from the ventricles. When the heart relaxes, the ventricles fill with blood. No matter how strong the contraction, the heart never ejects all the blood from the ventricles. LVEF is the percentage of blood expelled from the left ventricle with each beat. The LVEF in a healthy heart is between 55 and 70 percent. LVEF may be lower if the heart attack has damaged the heart muscle. Echocardiography is also used to see if the movement of the heart wall has decreased (this is known as "hypokinesia").

A coronary angiography, a study performed in a cardiac catheterization laboratory, administering a mild sedative. A dye is injected into the bloodstream to produce an "animated" x-ray of the heart's activity and blood flow through the valves and arteries (called an "angiogram"). The angiogram shows how many obstructions there are and how severe they are. Doctors often do this study to determine what would be the most effective treatment. Outcomes of a heart attack.

The outcome of a heart attack depends on several factors:

 

Where the coronary obstruction occurs. Blockages on the left side of the heart are generally more dangerous.

If there was a rhythm disturbance. When the obstruction also causes an irregular pulse called an arrhythmia, it could lead to sudden death. There can be both a fast heartbeat (called "tachycardia") and rapid, uncoordinated contractions (called "ventricular fibrillation"). Ventricular fibrillation interrupts blood flow, which must be quickly restored by cardiopulmonary resuscitation (CPR) or electrical treatment (defibrillation).

If the heart receives blood from another source. In some cases, the body responds to gradual blockage of an artery by dilating another vessel that supplies blood to the same part of the heart. This vessel becomes what is called a "collateral source of blood supply." In that case, the damage caused by the obstruction would be less.

How quickly assistance is received. In most cases, getting medical help within an hour of the attack will limit the loss of heart muscle.

What treatments are there?

The goals of treatment after a heart attack are to restore blood flow to the heart muscle, normalize the pulse, and give the heart time to recover.

 The development of drugs capable of dissolving clots, called 'thrombolytic agents', such as streptokinase, urokinase, and tissue plasminogen activators, has increased survival rates in patients who have suffered a heart attack when they are administered as soon as possible after an attack. The term "thrombolysis" means "clot-dissolving" and that is exactly what these drugs do. In some cases, they can do it in a matter of minutes. To be most effective they should be given as soon as possible after a heart attack.

 

Most patients respond well to thrombolytic agents. But if they are in a facility that has a cardiac catheterization laboratory, they may not receive these clot-dissolving medications but may be taken immediately to the cardiac catheterization laboratory, where techniques such as balloon angioplasty and placement of stents to open blood vessels. Sometimes patients who do not respond well to these interventions may need an additional emergency procedure, such as a coronary bypass or a related procedure.

 

Patients who have had a heart attack may also receive antiplatelets such as aspirin and blood thinners (anticoagulants) to prevent clots from forming or enlarging. Oxygen can also be given to increase the amount of oxygen in the blood that is still flowing through the heart. Pain relievers may be given to reduce pain. Some patients are also given medications to slow the heart rate, dilate and relax the blood vessels, and reduce the work of the heart.

 

Rest is important immediately after a heart attack. But within a few days, the patient must get up and move, walk a few steps, and do other types of limited physical exercise. Studies show that the heart benefits from physical exercise, even after a heart attack.

Sometimes after a heart attack, an aneurysm forms in the left ventricle, which is the main pumping chamber of the heart. If a section of the heart wall is damaged after a heart attack, scars form and the heart wall becomes thinner and weaker. This could lead to the formation of a ventricular aneurysm. The weakened area of ​​the aneurysm does not work well, causing the heart to work harder to pump blood to the rest of the body. Ventricular aneurysms can cause shortness of breath, chest pain, or an irregular pulse (arrhythmia). If a ventricular aneurysm is causing congestive heart failure, left ventricular failure, or arrhythmia, your doctor may recommend surgery.