Heart Attack
What is a heart attack?
A heart attack (also known as a myocardial infarction) is the death of heart muscle from the sudden blockage of a coronary artery by a blood clot. Coronary arteries are blood vessels that supply the heart muscle with blood and oxygen. Blockage of a coronary artery deprives the heart muscle of blood and oxygen,causing injury to the heart muscle. Injury to the heart muscle causes chest pain and chest pressure sensation. If blood flow is not restored to the heart muscle within 20 to 40 minutes, irreversible death of the heart muscle will begin to occur. Muscle continues to die for six to eight hours at which time the heart attack usually is "complete." The dead heart muscle is eventually replaced by scar tissue.
Causes :
Atherosclerosis
Atherosclerosis is a gradual process by which plaques (collections) of cholesterol are deposited in the walls of arteries. Cholesterol plaques cause hardening of the arterial walls and narrowing of the inner channel (lumen) of the artery. Arteries that are narrowed by atherosclerosis cannot deliver enough blood to maintain normal function of the parts of the body they supply. For example, atherosclerosis of the arteries in the legs causes reduced blood flow to the legs. Reduced blood flow to the legs can lead to pain in the legs while walking or exercising, leg ulcers, or a delay in the healing of wounds to the legs. Atherosclerosis of the arteries that furnish blood to the brain can lead to vascular dementia(mental deterioration due to gradual death of brain tissue over many years) or stroke (sudden death of brain tissue).
In many people, atherosclerosis can remain silent (causing no symptoms or health problems) for years or decades. Atherosclerosis can begin as early as the teenage years, but symptoms or health problems usually do not arise until later in adulthood when the arterial narrowing becomes severe. Smoking cigarettes, high blood pressure,elevated cholesterol, and diabetes mellitus can accelerate atherosclerosis and lead to the earlier onset of symptoms and complications, particularly in those people who have a family history of early atherosclerosis.
Coronary atherosclerosis (or coronary artery disease) refers to the atherosclerosis that causes hardening and narrowing of the coronary arteries. Diseases caused by the reduced blood supply to the heart muscle from coronary atherosclerosis are called coronary heart diseases (CHD). Coronary heart diseases include heart attacks, sudden unexpected death, chest pain (angina), abnormal heart rhythms, and heart failure due to weakening of the heart muscle.
Atherosclerosis and angina pectoris
Angina pectoris (also referred to as angina) is chest pain or pressure that occurs when the blood and oxygen supply to the heart muscle cannot keep up with the needs of the muscle. When coronary arteries are narrowed by more than 50 to 70 percent, the arteries may not be able to increase the supply of blood to the heart muscle during exercise or other periods of high demand for oxygen. An insufficient supply of oxygen to the heart muscle causes angina. Angina that occurs with exercise or exertion is calledexertional angina. In some patients, especially diabetics, the progressive decrease in blood flow to the heart may occur without any pain or with just shortness of breath or unusually early fatigue.
Exertional angina usually feels like a pressure, heaviness, squeezing, or aching across the chest. This pain may travel to the neck, jaw, arms, back, or even the teeth, and may be accompanied by shortness of breath, nausea, or a cold sweat. Exertional angina typically lasts from one to 15 minutes and is relieved by rest or by taking nitroglycerin by placing a tablet under the tongue. Both resting and nitroglycerin decrease the heart muscle's demand for oxygen, thus relieving angina. Exertional angina may be the first warning sign of advanced coronary artery disease. Chest pains that just last a few seconds rarely are due to coronary artery disease.
Angina also can occur at rest. Angina at rest more commonly indicates that a coronary artery has narrowed to such a critical degree that the heart is not receiving enough oxygen even at rest. Angina at rest infrequently may be due to spasm of a coronary artery (a condition called Prinzmetal's or variant angina). Unlike a heart attack, there is no permanent muscle damage with either exertional or rest angina.
Atherosclerosis and heart attack
Occasionally the surface of a cholesterol plaque in a coronary artery may rupture, and a blood clot forms on the surface of the plaque. The clot blocks the flow of blood through the artery and results in a heart attack (see picture below). The cause of rupture that leads to the formation of a clot is largely unknown, but contributing factors may includecigarette smoking or other nicotine exposure, elevated LDL cholesterol, elevated levels of blood catecholamines (adrenaline), high blood pressure, and other mechanical and biochemical forces.
Unlike exertional or rest angina, heart muscle dies during a heart attack and loss of the muscle is permanent, unless blood flow can be promptly restored, usually within one to six hours.
While heart attacks can occur at any time, more heart attacks occur between 4:00 A.M. and 10:00 A.M. because of the higher blood levels of adrenaline released from the adrenal glands during the morning hours. Increased adrenaline, as previously discussed, may contribute to rupture of cholesterol plaques.
Approximately 50% of patients who develop heart attacks have warning symptoms such as exertional angina or rest angina prior to their heart attacks, but these symptoms may be mild and discounted.
Risk Factors :
Heart attack is most often caused by narrowing of the arteries by cholesterol plaque and their subsequent rupture. This is known as atherosclerotic heart disease (AHSD) orcoronary artery disease (CAD).
The risk factors for ASHD are the same as those for stroke (cerebrovascular disease) orperipheral vascular disease:
- Family history or heredity
- Smoking
- High blood pressure
- High cholesterol
- Diabetes
While heredity is beyond a patient's control, all other risk factors can be addressed to minimize the risk of developing coronary artery disease or decreasing its progression if already present.
Non-coronary artery disease causes of heart attack may also occur, these include:
- Cocaine use
- Prinzmetal angina or coronary artery vasospasm
- Anomalous coronary artery
- Inadequate oxygenation.
symptoms :
Although chest pain or pressure is the most common symptom of a heart attack, heart attack victims may experience a variety of symptoms including:
- Pain, fullness, and/or squeezing sensation of the chest
- Jaw pain, toothache, headache
- Shortness of breath
- Nausea, vomiting, and/or general epigastric (upper middle abdomen) discomfort
- Sweating
- Heartburn and/or indigestion
- Arm pain (more commonly the left arm, but may be either arm)
- Upper back pain
- General malaise (vague feeling of illness)
- No symptoms (Approximately one quarter of all heart attacks are silent, without chest pain or new symptoms. Silent heart attacks are especially common among patients with diabetes mellitus.)
Even though the symptoms of a heart attack at times can be vague and mild, it is important to remember that heart attacks producing no symptoms or only mild symptoms can be just as serious and life-threatening as heart attacks that cause severe chest pain. Too often patients attribute heart attack symptoms to "indigestion," "fatigue," or "stress," and consequently delay seeking prompt medical attention. One cannot overemphasize the importance of seeking prompt medical attention in the presence of symptoms that suggest a heart attack. Early diagnosis and treatment saves lives, and delays in reaching medical assistance can be fatal. A delay in treatment can lead to permanently reduced function of the heart due to more extensive damage to the heart muscle. Death also may occur as a result of the sudden onset of arrhythmias such as ventricular fibrillation.
complications :
Heart failure
When a large amount of heart muscle dies, the ability of the heart to pump blood to the rest of the body is diminished, and this can result in heart failure. The body retains fluid, and organs, for example, the kidneys, begin to fail.
Ventricular fibrillation
Injury to heart muscle also can lead toventricular fibrillation. Ventricular fibrillation occurs when the normal, regular, electrical activation of heart muscle contraction is replaced by chaotic electrical activity that causes the heart to stop beating and pumping blood to the brain and other parts of the body. Permanent brain damage and death can occur unless the flow of blood to the brain is restored within five minutes.
Most of the deaths from heart attacks are caused by ventricular fibrillation of the heart that occurs before the victim of the heart attack can reach an emergency room. Those who reach the emergency room have an excellent prognosis; survival from a heart attack with modern treatment should exceed 90%. The 1% to 10% of heart attack victims who later die frequently had suffered major damage to the heart muscle initially or additional damage at a later time.
Diagnosis :
Medical History
As is the case in most of medicine, the diagnosis of angina is made by history. If the story that the patient tells is suggestive of cardiac ischemia (cardiac= heart + ischemia= decreased blood supply), then the care provider will continue on the path to determine whether a heart attack has occurred.
Important questions include:
- When did the pain start?
- What were you doing?
- Did you have to stop?
- Did the pain get better with rest?
- Did the pain come back with activity?
- Did the pain stay in your chest or did it move somewhere else, like the jaw, teeth, arm or back?
- Did you get short of breath?
- Did you become nauseous?
- Were you sweating profusely?
The medical history also includes assessing risk factors for heart disease, including:
- Smoking
- Hypertension or high blood pressure
- High cholesterol
- Diabetes
- Previous history of other blood vessel problems like stroke or peripheral vascular disease
- Family history of heart disease, especially at an early age
Questions may be asked about changes in exercise tolerance that might give clues as to whether heart disease is present:
- Have there been episodes of previous chest pain?
- Is there shortness of breath on exertion?
- Can you walk to get the mail?
- Can you climb a flight of stairs?
Since other diagnoses will be considered, some questions may be asked to identify potential symptoms of conditions such as reflux esophagitis (GERD),gastritis, trauma, pulmonary embolus, or pneumonia.
Physical examination
While the diagnosis is based on history, the physical exam can give some clues.
- Are the blood pressure and pulse rate normal?
- Do the lungs sound clear?
- Are there findings suggestive of an infection (pneumonia) or fluid (edema)?
- Are there unusual heart sounds? New murmurs can be associated with heart attack.
- Are bruits (noises produced by narrowed blood vessels that are heard with a stethoscope) present when listening to the neck, abdomen, or groin?
- Is there tenderness in the abdomen that would suggest the chest pain is due to gallbladder, pancreas, or ulcer disease?
EKGs, blood tests, and chest x-ray are other tests that are likely to be performed to assist with the diagnosis.
Electrocardiogram
The electrocardiogram (ECG or EKG) will help direct what happens acutely in the ER. The EKG measures electrical activity and conduction in heart muscle. In a heart attack in which the full thickness of the heart muscle is involved, the EKG shows characteristic changes that establish the diagnosis of a myocardial infarction. Some heart attacks only involve small parts of the heart muscle; in these cases, the EKG can look relatively normal.
Blood tests
If the EKG does not diagnose a heart attack, blood testing may be required to further look for heart damage. An EKG can be normal even in the presence of a heart attack. This is done with blood tests that can measure chemicals that leak out of irritated heart muscle cells and can be measured in the blood. Levels of the cardiac enzymes myoglobin, CPK, and troponin are often measured, alone or in combination, to assess whether heart muscle damage has occurred. Unfortunately, it takes time for these chemicals to accumulate in the blood stream after the heart muscle has been insulted. Blood samples need to be drawn at the appropriate time so that the results can be usefully interpreted. For example, the recommendation for the troponin blood test is to draw a first sample at the time the patient presents to the ER and then a second sample 6-12 hours later. Usually it requires two negative samples to confirm that no heart muscle damage has occurred. (Please note that under special circumstances, one sample may be sufficient.)
Chest X-ray
A chest x-ray may be taken to look for a variety of findings including the shape of the heart, the width of the aorta, and the clarity of the lung fields.
If a heart attack has been proven not to have occurred, further evaluation of the heart may be undertaken using stress tests, echocardiography, or heart catheterization.
Heart Attack Treatment :
If the EKG shows that there is an acute heart attack (myocardial infarction), then the goal is to open the blocked artery as soon as possible and restore blood supply to the heart muscle.
When a heart attack strikes, the key thing to remember is that time equals muscle. The longer the delay in seeking medical care, the more heart muscle will be damaged. There is a window of opportunity to restore blood supply to the heart muscle by unblocking the affected heart artery. Treatments must be done in a hospital and include administration of clot-busting drugs to dissolve the clot at the site of the ruptured plaque and heart catheterization and angioplasty (in which the blood vessel is opened by balloon, often with adjunctive placement of a stent), or both.
Emergency Medical Treatment :
Hospitals have established treatment plans to minimize the time to diagnose and treat people with heart attack. National guidelines suggest that an electrocardiogram (EKG) be done within 10 minutes of the patient's arrival in the ER.
Many things will occur at the same time as the EKG being completed. The doctor will take a history and complete a physical exam while the nurses start an intravenous line, place heart monitor lines on the chest, and administer oxygen.
Medications are used to try to restore blood supply to the heart muscle. If it wasn't taken prior to arrival in the ER, aspirin will be used for its anti-platelet action. Nitroglycerin will be used to dilate blood vessels. Heparin orenoxaparin (Lovenox) will be used to thin the blood. Morphine can also be used for pain control.
There are two options (depending on the resources at the hospital) if the EKG shows an acute heart attack (myocardial infarction), and if there are no contraindications.
Heart catheterization
The favored treatment is heart catheterization. Tubes are threaded through the femoral artery in the groin or through the brachial artery in the elbow, into the coronary arteries, and the area of blockage is identified.
Angioplasty
Angioplasty (angio= artery + plasty=repair) is then considered if possible. A balloon is placed at the blockage site and as it opens, it squashes the plaque into the blood vessel wall. Afterwards, a stent or a mesh cage is placed across the angioplasty site to keep it from closing down. Guidelines recommend that the time from the time the patient presents to the hospital to having the blood vessel open be less than 90 minutes.
Not all hospitals have the capabilities of doing heart catheterizations 24 hours a day, and may transfer the patient with an acute heart attack to a hospital that has that technology available. If the transfer time will delay angioplasty treatment beyond the 90 minute window recommendation, clot-busting drugs may be considered to dissolve the blood clot that has obstructed the coronary artery.Tissue plasminogen activator (TPA or TNK) can be used intravenously. After TPA infusion, the patient may still be transferred for heart catheterization and further care.
If the EKG is normal but the history is suggestive of an heart attack or angina, the evaluation will continue with the blood tests described above. However, the patient will likely be treated as if the heart attack was happening with aspirin, oxygen,nitroglycerin and blood thinning medications until the presence of heart damage is proven not to be present. The treatment presumes heart disease until proven otherwise.
Heart Attack Complications
When a heart attack occurs, part of the heart muscle dies and is ultimately replaced with scar tissue. This leaves the heart weaker and less able to meet the needs of the body. This will lead to exercise intolerance including early fatigue or shortness of breath on exertion. The amount of disability is dependent on the amount of muscle pumping function lost.
Muscle that loses its blood supply becomes electrically irritable. This may cause a short circuit of the electrical conduction system of the heart. This may causeventricular fibrillation, a situation where the ventricles do not beat in a coordinated function. Instead, they jiggle like a bowl of Jello and cannot pump blood to the body. Sudden death occurs. Patients are kept in the ER or admitted to the hospital while assessing chest pain to monitor their heart rhythm and hopefully prevent sudden death from acute heart attack or unstable angina which may result in ventricular fibrillation.
If this rhythm occurs while monitored in the hospital, it can be rapidly treated with no adverse sequelae.
Follow-Up :
Medications that may be recommended on discharge from the hospital include:
- aspirin for its anti-platelet effect,
- a beta blocker to blunt the effect of adrenaline on the heart and make it beat more efficiently,
- a statin drug to control cholesterol and
- clopidogrel (Plavix), another anti-platelet drug.
Since the heart may have been damaged, further testing may be needed to assess its pumping capabilities. Echocardiography can measure ejection fraction, the amount of blood that heart pumps out to the body compared to how much it receives. A normal ejection fraction should be greater than 50%-60%.
A monitored exercise program may be arranged.
Attempts will be made to minimize cardiac risk factors including:
- smoking cessation,
- weight loss,
- control blood pressure, and
- lower "bad" cholesterol.
Some patients will require coronary artery bypass surgery if their angiogram shows multiple areas of blockage.
Special Situations
Prinzmetal Angina
In some people, the coronary arteries can go into spasm and cause decreased blood flow to heart muscle. This can lead to chest pain known as Prinzmetal angina, even if there is no buildup of plaque in the blood vessels. In severe episodes the EKG can suggest a heart attack, and muscle damage can be confirmed by measuring cardiac enzymes.
Cocaine
There is a strong correlation between cocaine usage and heart attack. Aside from the artery spasm that cocaine induces, the drug turns on the adrenaline system of the body, increasing pulse rate and blood pressure, requiring the heart to do more work.
Prevention :
While people cannot control their family history and genetics, they can minimize risk factors for heart disease:
- quit smoking
- manage high blood pressure,
- manage cholesterol,
- manage diabetes,
- exercise regularly
- take a baby aspirin a day.
These are all lifelong challenges to prevent heart disease, stroke, and peripheral vascular disease.
Heart Attack At A Glance :
- A heart attack results when a blood clot completely obstructs a coronary artery supplying blood to the heart muscle and heart muscle dies.
- The blood clot that causes the heart attack usually forms at the site of rupture of an atherosclerotic, cholesterol plaque on the inner wall of a coronary artery.
- The most common symptom of heart attack is chest pain.
- The most common complications of a heart attack are heart failure, and ventricular fibrillation.
- The risk factors for atherosclerosis and heart attack include elevated cholesterol levels, increased blood pressure, tobacco use, diabetes, male gender and a family history of heart attacks at an early age.
- Heart attacks are diagnosed with electrocardiograms and measurement of cardiac enzymes in blood
- Early reopening of blocked coronary arteries reduces the amount of damage to the heart and improves the prognosis for a heart attack.
- Medical treatment for heart attacks may include anti-platelet, anti-coagulant, and clot dissolving drugs as well as angiotensin converting enzyme (ACE) inhibitors, beta blockers and oxygen.
- Interventional treatment for heart attacks may include coronary angiography with percutaneous transluminal coronary angioplasty (PTCA), coronary artery stents, and coronary artery bypass grafting (CABG).
- Patients suffering a heart attack are hospitalized for several days to detect heart rhythm disturbances, shortness of breath, and chest pain.
- Further heart attacks can be prevented by aspirin, beta blockers, ACE inhibitors, discontinuing smoking, weight reduction, exercise, good control of blood pressure and diabetes, following a low cholesterol and low saturated fat diet that is high in omega-3-fatty acids, taking multivitamins with an increased amount of folic acid, decreasing LDL cholesterol, and increasing HDL cholesterol.
What is a heart attack?
A heart attack (also known as a myocardial infarction) is the death of heart muscle from the sudden blockage of a coronary artery by a blood clot. Coronary arteries are blood vessels that supply the heart muscle with blood and oxygen. Blockage of a coronary artery deprives the heart muscle of blood and oxygen,causing injury to the heart muscle. Injury to the heart muscle causes chest pain and chest pressure sensation. If blood flow is not restored to the heart muscle within 20 to 40 minutes, irreversible death of the heart muscle will begin to occur. Muscle continues to die for six to eight hours at which time the heart attack usually is "complete." The dead heart muscle is eventually replaced by scar tissue.
Causes :
Atherosclerosis
Atherosclerosis is a gradual process by which plaques (collections) of cholesterol are deposited in the walls of arteries. Cholesterol plaques cause hardening of the arterial walls and narrowing of the inner channel (lumen) of the artery. Arteries that are narrowed by atherosclerosis cannot deliver enough blood to maintain normal function of the parts of the body they supply. For example, atherosclerosis of the arteries in the legs causes reduced blood flow to the legs. Reduced blood flow to the legs can lead to pain in the legs while walking or exercising, leg ulcers, or a delay in the healing of wounds to the legs. Atherosclerosis of the arteries that furnish blood to the brain can lead to vascular dementia(mental deterioration due to gradual death of brain tissue over many years) or stroke (sudden death of brain tissue).
In many people, atherosclerosis can remain silent (causing no symptoms or health problems) for years or decades. Atherosclerosis can begin as early as the teenage years, but symptoms or health problems usually do not arise until later in adulthood when the arterial narrowing becomes severe. Smoking cigarettes, high blood pressure,elevated cholesterol, and diabetes mellitus can accelerate atherosclerosis and lead to the earlier onset of symptoms and complications, particularly in those people who have a family history of early atherosclerosis.
Coronary atherosclerosis (or coronary artery disease) refers to the atherosclerosis that causes hardening and narrowing of the coronary arteries. Diseases caused by the reduced blood supply to the heart muscle from coronary atherosclerosis are called coronary heart diseases (CHD). Coronary heart diseases include heart attacks, sudden unexpected death, chest pain (angina), abnormal heart rhythms, and heart failure due to weakening of the heart muscle.
Atherosclerosis and angina pectoris
Angina pectoris (also referred to as angina) is chest pain or pressure that occurs when the blood and oxygen supply to the heart muscle cannot keep up with the needs of the muscle. When coronary arteries are narrowed by more than 50 to 70 percent, the arteries may not be able to increase the supply of blood to the heart muscle during exercise or other periods of high demand for oxygen. An insufficient supply of oxygen to the heart muscle causes angina. Angina that occurs with exercise or exertion is calledexertional angina. In some patients, especially diabetics, the progressive decrease in blood flow to the heart may occur without any pain or with just shortness of breath or unusually early fatigue.
Exertional angina usually feels like a pressure, heaviness, squeezing, or aching across the chest. This pain may travel to the neck, jaw, arms, back, or even the teeth, and may be accompanied by shortness of breath, nausea, or a cold sweat. Exertional angina typically lasts from one to 15 minutes and is relieved by rest or by taking nitroglycerin by placing a tablet under the tongue. Both resting and nitroglycerin decrease the heart muscle's demand for oxygen, thus relieving angina. Exertional angina may be the first warning sign of advanced coronary artery disease. Chest pains that just last a few seconds rarely are due to coronary artery disease.
Angina also can occur at rest. Angina at rest more commonly indicates that a coronary artery has narrowed to such a critical degree that the heart is not receiving enough oxygen even at rest. Angina at rest infrequently may be due to spasm of a coronary artery (a condition called Prinzmetal's or variant angina). Unlike a heart attack, there is no permanent muscle damage with either exertional or rest angina.
Atherosclerosis and heart attack
Occasionally the surface of a cholesterol plaque in a coronary artery may rupture, and a blood clot forms on the surface of the plaque. The clot blocks the flow of blood through the artery and results in a heart attack (see picture below). The cause of rupture that leads to the formation of a clot is largely unknown, but contributing factors may includecigarette smoking or other nicotine exposure, elevated LDL cholesterol, elevated levels of blood catecholamines (adrenaline), high blood pressure, and other mechanical and biochemical forces.
Unlike exertional or rest angina, heart muscle dies during a heart attack and loss of the muscle is permanent, unless blood flow can be promptly restored, usually within one to six hours.
While heart attacks can occur at any time, more heart attacks occur between 4:00 A.M. and 10:00 A.M. because of the higher blood levels of adrenaline released from the adrenal glands during the morning hours. Increased adrenaline, as previously discussed, may contribute to rupture of cholesterol plaques.
Approximately 50% of patients who develop heart attacks have warning symptoms such as exertional angina or rest angina prior to their heart attacks, but these symptoms may be mild and discounted.
Risk Factors :
Heart attack is most often caused by narrowing of the arteries by cholesterol plaque and their subsequent rupture. This is known as atherosclerotic heart disease (AHSD) orcoronary artery disease (CAD).
The risk factors for ASHD are the same as those for stroke (cerebrovascular disease) orperipheral vascular disease:
- Family history or heredity
- Smoking
- High blood pressure
- High cholesterol
- Diabetes
While heredity is beyond a patient's control, all other risk factors can be addressed to minimize the risk of developing coronary artery disease or decreasing its progression if already present.
Non-coronary artery disease causes of heart attack may also occur, these include:
- Cocaine use
- Prinzmetal angina or coronary artery vasospasm
- Anomalous coronary artery
- Inadequate oxygenation.
symptoms :
Although chest pain or pressure is the most common symptom of a heart attack, heart attack victims may experience a variety of symptoms including:
- Pain, fullness, and/or squeezing sensation of the chest
- Jaw pain, toothache, headache
- Shortness of breath
- Nausea, vomiting, and/or general epigastric (upper middle abdomen) discomfort
- Sweating
- Heartburn and/or indigestion
- Arm pain (more commonly the left arm, but may be either arm)
- Upper back pain
- General malaise (vague feeling of illness)
- No symptoms (Approximately one quarter of all heart attacks are silent, without chest pain or new symptoms. Silent heart attacks are especially common among patients with diabetes mellitus.)
Even though the symptoms of a heart attack at times can be vague and mild, it is important to remember that heart attacks producing no symptoms or only mild symptoms can be just as serious and life-threatening as heart attacks that cause severe chest pain. Too often patients attribute heart attack symptoms to "indigestion," "fatigue," or "stress," and consequently delay seeking prompt medical attention. One cannot overemphasize the importance of seeking prompt medical attention in the presence of symptoms that suggest a heart attack. Early diagnosis and treatment saves lives, and delays in reaching medical assistance can be fatal. A delay in treatment can lead to permanently reduced function of the heart due to more extensive damage to the heart muscle. Death also may occur as a result of the sudden onset of arrhythmias such as ventricular fibrillation.
complications :
Heart failure
When a large amount of heart muscle dies, the ability of the heart to pump blood to the rest of the body is diminished, and this can result in heart failure. The body retains fluid, and organs, for example, the kidneys, begin to fail.
Ventricular fibrillation
Injury to heart muscle also can lead toventricular fibrillation. Ventricular fibrillation occurs when the normal, regular, electrical activation of heart muscle contraction is replaced by chaotic electrical activity that causes the heart to stop beating and pumping blood to the brain and other parts of the body. Permanent brain damage and death can occur unless the flow of blood to the brain is restored within five minutes.
Most of the deaths from heart attacks are caused by ventricular fibrillation of the heart that occurs before the victim of the heart attack can reach an emergency room. Those who reach the emergency room have an excellent prognosis; survival from a heart attack with modern treatment should exceed 90%. The 1% to 10% of heart attack victims who later die frequently had suffered major damage to the heart muscle initially or additional damage at a later time.
Diagnosis :
Medical History
As is the case in most of medicine, the diagnosis of angina is made by history. If the story that the patient tells is suggestive of cardiac ischemia (cardiac= heart + ischemia= decreased blood supply), then the care provider will continue on the path to determine whether a heart attack has occurred.
Important questions include:
- When did the pain start?
- What were you doing?
- Did you have to stop?
- Did the pain get better with rest?
- Did the pain come back with activity?
- Did the pain stay in your chest or did it move somewhere else, like the jaw, teeth, arm or back?
- Did you get short of breath?
- Did you become nauseous?
- Were you sweating profusely?
The medical history also includes assessing risk factors for heart disease, including:
- Smoking
- Hypertension or high blood pressure
- High cholesterol
- Diabetes
- Previous history of other blood vessel problems like stroke or peripheral vascular disease
- Family history of heart disease, especially at an early age
Questions may be asked about changes in exercise tolerance that might give clues as to whether heart disease is present:
- Have there been episodes of previous chest pain?
- Is there shortness of breath on exertion?
- Can you walk to get the mail?
- Can you climb a flight of stairs?
Since other diagnoses will be considered, some questions may be asked to identify potential symptoms of conditions such as reflux esophagitis (GERD),gastritis, trauma, pulmonary embolus, or pneumonia.
Physical examination
While the diagnosis is based on history, the physical exam can give some clues.
- Are the blood pressure and pulse rate normal?
- Do the lungs sound clear?
- Are there findings suggestive of an infection (pneumonia) or fluid (edema)?
- Are there unusual heart sounds? New murmurs can be associated with heart attack.
- Are bruits (noises produced by narrowed blood vessels that are heard with a stethoscope) present when listening to the neck, abdomen, or groin?
- Is there tenderness in the abdomen that would suggest the chest pain is due to gallbladder, pancreas, or ulcer disease?
EKGs, blood tests, and chest x-ray are other tests that are likely to be performed to assist with the diagnosis.
Electrocardiogram
The electrocardiogram (ECG or EKG) will help direct what happens acutely in the ER. The EKG measures electrical activity and conduction in heart muscle. In a heart attack in which the full thickness of the heart muscle is involved, the EKG shows characteristic changes that establish the diagnosis of a myocardial infarction. Some heart attacks only involve small parts of the heart muscle; in these cases, the EKG can look relatively normal.
Blood tests
If the EKG does not diagnose a heart attack, blood testing may be required to further look for heart damage. An EKG can be normal even in the presence of a heart attack. This is done with blood tests that can measure chemicals that leak out of irritated heart muscle cells and can be measured in the blood. Levels of the cardiac enzymes myoglobin, CPK, and troponin are often measured, alone or in combination, to assess whether heart muscle damage has occurred. Unfortunately, it takes time for these chemicals to accumulate in the blood stream after the heart muscle has been insulted. Blood samples need to be drawn at the appropriate time so that the results can be usefully interpreted. For example, the recommendation for the troponin blood test is to draw a first sample at the time the patient presents to the ER and then a second sample 6-12 hours later. Usually it requires two negative samples to confirm that no heart muscle damage has occurred. (Please note that under special circumstances, one sample may be sufficient.)
Chest X-ray
A chest x-ray may be taken to look for a variety of findings including the shape of the heart, the width of the aorta, and the clarity of the lung fields.
If a heart attack has been proven not to have occurred, further evaluation of the heart may be undertaken using stress tests, echocardiography, or heart catheterization.
Heart Attack Treatment :
If the EKG shows that there is an acute heart attack (myocardial infarction), then the goal is to open the blocked artery as soon as possible and restore blood supply to the heart muscle.
When a heart attack strikes, the key thing to remember is that time equals muscle. The longer the delay in seeking medical care, the more heart muscle will be damaged. There is a window of opportunity to restore blood supply to the heart muscle by unblocking the affected heart artery. Treatments must be done in a hospital and include administration of clot-busting drugs to dissolve the clot at the site of the ruptured plaque and heart catheterization and angioplasty (in which the blood vessel is opened by balloon, often with adjunctive placement of a stent), or both.
Emergency Medical Treatment :
Hospitals have established treatment plans to minimize the time to diagnose and treat people with heart attack. National guidelines suggest that an electrocardiogram (EKG) be done within 10 minutes of the patient's arrival in the ER.
Many things will occur at the same time as the EKG being completed. The doctor will take a history and complete a physical exam while the nurses start an intravenous line, place heart monitor lines on the chest, and administer oxygen.
Medications are used to try to restore blood supply to the heart muscle. If it wasn't taken prior to arrival in the ER, aspirin will be used for its anti-platelet action. Nitroglycerin will be used to dilate blood vessels. Heparin orenoxaparin (Lovenox) will be used to thin the blood. Morphine can also be used for pain control.
There are two options (depending on the resources at the hospital) if the EKG shows an acute heart attack (myocardial infarction), and if there are no contraindications.
Heart catheterization
The favored treatment is heart catheterization. Tubes are threaded through the femoral artery in the groin or through the brachial artery in the elbow, into the coronary arteries, and the area of blockage is identified.
Angioplasty
Angioplasty (angio= artery + plasty=repair) is then considered if possible. A balloon is placed at the blockage site and as it opens, it squashes the plaque into the blood vessel wall. Afterwards, a stent or a mesh cage is placed across the angioplasty site to keep it from closing down. Guidelines recommend that the time from the time the patient presents to the hospital to having the blood vessel open be less than 90 minutes.
Not all hospitals have the capabilities of doing heart catheterizations 24 hours a day, and may transfer the patient with an acute heart attack to a hospital that has that technology available. If the transfer time will delay angioplasty treatment beyond the 90 minute window recommendation, clot-busting drugs may be considered to dissolve the blood clot that has obstructed the coronary artery.Tissue plasminogen activator (TPA or TNK) can be used intravenously. After TPA infusion, the patient may still be transferred for heart catheterization and further care.
If the EKG is normal but the history is suggestive of an heart attack or angina, the evaluation will continue with the blood tests described above. However, the patient will likely be treated as if the heart attack was happening with aspirin, oxygen,nitroglycerin and blood thinning medications until the presence of heart damage is proven not to be present. The treatment presumes heart disease until proven otherwise.
Heart Attack Complications
When a heart attack occurs, part of the heart muscle dies and is ultimately replaced with scar tissue. This leaves the heart weaker and less able to meet the needs of the body. This will lead to exercise intolerance including early fatigue or shortness of breath on exertion. The amount of disability is dependent on the amount of muscle pumping function lost.
Muscle that loses its blood supply becomes electrically irritable. This may cause a short circuit of the electrical conduction system of the heart. This may causeventricular fibrillation, a situation where the ventricles do not beat in a coordinated function. Instead, they jiggle like a bowl of Jello and cannot pump blood to the body. Sudden death occurs. Patients are kept in the ER or admitted to the hospital while assessing chest pain to monitor their heart rhythm and hopefully prevent sudden death from acute heart attack or unstable angina which may result in ventricular fibrillation.
If this rhythm occurs while monitored in the hospital, it can be rapidly treated with no adverse sequelae.
Follow-Up :
Medications that may be recommended on discharge from the hospital include:
- aspirin for its anti-platelet effect,
- a beta blocker to blunt the effect of adrenaline on the heart and make it beat more efficiently,
- a statin drug to control cholesterol and
- clopidogrel (Plavix), another anti-platelet drug.
Since the heart may have been damaged, further testing may be needed to assess its pumping capabilities. Echocardiography can measure ejection fraction, the amount of blood that heart pumps out to the body compared to how much it receives. A normal ejection fraction should be greater than 50%-60%.
A monitored exercise program may be arranged.
Attempts will be made to minimize cardiac risk factors including:
- smoking cessation,
- weight loss,
- control blood pressure, and
- lower "bad" cholesterol.
Some patients will require coronary artery bypass surgery if their angiogram shows multiple areas of blockage.
Special Situations
Prinzmetal Angina
In some people, the coronary arteries can go into spasm and cause decreased blood flow to heart muscle. This can lead to chest pain known as Prinzmetal angina, even if there is no buildup of plaque in the blood vessels. In severe episodes the EKG can suggest a heart attack, and muscle damage can be confirmed by measuring cardiac enzymes.
Cocaine
There is a strong correlation between cocaine usage and heart attack. Aside from the artery spasm that cocaine induces, the drug turns on the adrenaline system of the body, increasing pulse rate and blood pressure, requiring the heart to do more work.
Prevention :
While people cannot control their family history and genetics, they can minimize risk factors for heart disease:
- quit smoking
- manage high blood pressure,
- manage cholesterol,
- manage diabetes,
- exercise regularly
- take a baby aspirin a day.
These are all lifelong challenges to prevent heart disease, stroke, and peripheral vascular disease.
Heart Attack At A Glance :
- A heart attack results when a blood clot completely obstructs a coronary artery supplying blood to the heart muscle and heart muscle dies.
- The blood clot that causes the heart attack usually forms at the site of rupture of an atherosclerotic, cholesterol plaque on the inner wall of a coronary artery.
- The most common symptom of heart attack is chest pain.
- The most common complications of a heart attack are heart failure, and ventricular fibrillation.
- The risk factors for atherosclerosis and heart attack include elevated cholesterol levels, increased blood pressure, tobacco use, diabetes, male gender and a family history of heart attacks at an early age.
- Heart attacks are diagnosed with electrocardiograms and measurement of cardiac enzymes in blood
- Early reopening of blocked coronary arteries reduces the amount of damage to the heart and improves the prognosis for a heart attack.
- Medical treatment for heart attacks may include anti-platelet, anti-coagulant, and clot dissolving drugs as well as angiotensin converting enzyme (ACE) inhibitors, beta blockers and oxygen.
- Interventional treatment for heart attacks may include coronary angiography with percutaneous transluminal coronary angioplasty (PTCA), coronary artery stents, and coronary artery bypass grafting (CABG).
- Patients suffering a heart attack are hospitalized for several days to detect heart rhythm disturbances, shortness of breath, and chest pain.
- Further heart attacks can be prevented by aspirin, beta blockers, ACE inhibitors, discontinuing smoking, weight reduction, exercise, good control of blood pressure and diabetes, following a low cholesterol and low saturated fat diet that is high in omega-3-fatty acids, taking multivitamins with an increased amount of folic acid, decreasing LDL cholesterol, and increasing HDL cholesterol.
0 comments:
Post a Comment