Heart Attack (Myocardial Infarction)

A myocardial infarction or heart attack occurs when the sudden blockage of a coronary artery, usually because of blood clot, causes damage and death to heart muscle.

A myocardial infarction (myo=muscle + cardium=heart + infarction=death) or heart attack occurs when the sudden blockage of a coronary artery, usually because of blood clot, causes damage and death to heart muscle.

The heart is an electric pump with the purpose of sending oxygen-rich blood through the arteries of the body to every organ and cell to allow them to function.

The heart is a muscle and needs a constant supply of oxygen. There are three main arteries to the heart: the left anterior descending (LAD), the right anterior descending (RAD), and the circumflex. Together, they branch out into tinier and tinier arterioles and capillaries to provide oxygen to every muscle cell in the heart.

If the arteries narrow enough, some heart muscle cells may not receive enough blood supply and fail to pump blood as efficiently. Also, a heart muscle that lacks enough blood supply gets irritated and that can affect the electrical activity of the heart.

Symptoms of a heart attack or MI may include chest discomfort often described as a pain, pressure, or tightness associated with shortness of breath, sweating, and nausea. The goal for medical care is to restore blood supply back to the heart as soon as possible -- that time is measured in minutes. The longer the heart muscle cells fail to get oxygen delivered, the more likely permanent damage will occur. Dead heart muscle is eventually replaced by scar tissue, and the risk of both short- and long-term complications increase for sudden death and heart failure.

All heart attacks are a medical emergency and can be life-threatening. A “widowmaker” is a type of heart attack that is deadlier than most others.

A widowmaker heart attack occurs when the left ascending artery that supplies blood to the left ventricle, the thickest and strongest part of the heart and responsible for pumping blood to the whole body, is completely blocked because of blood clot. There is no blood flow or oxygen delivery to a large part of the heart causing many muscle cells to die.

In addition to weakening the heart, the widowmaker can also make the heart muscle irritable, increasing the risk of abnormal electrical activity like ventricular fibrillation (VFib). VFib is the cause of sudden cardiac death. Normally, the heart beats rhythmically, but in VFib, every cell of the ventricle generates its own electrical signal, not allowing a unified beating of the heart. Instead, the heart muscle fibrillates, or jiggles like a bowl of Jell-O, stopping the heart from beating and pumping blood to the body.

The immediate death rate outside of the hospital from a widowmaker heart attack is about 12% and inside the hospital the mortality is 27%.

Atherosclerosis

Atherosclerosis, also called hardening of the arteries, is a gradual process where fats and cholesterol build up inside and on the walls of an artery. These are called plaques, which narrow the inner channel (lumen) of the artery, decreasing the amount of blood flow that can get through.

Plaque can build up in any artery of the body. If the plaque involves leg arteries, the decreased blood supply to the leg muscles can cause claudication or pain in the legs with activity. Plaque buildup in arteries of the neck or brain can lead to stroke. Plaque that builds up in the arteries of the heart can lead to heart attack.

Atherosclerosis takes time to become clinically significant. An artery needs to be narrowed by 50 to 70 percent before symptoms develop. Therefore, this disease 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. The risk factors for developing atherosclerosis include cigarette smoking, high blood pressure (hypertension), high cholesterol and triglycerides, diabetes mellitus, family history, and older age.

Atherosclerosis of the coronary arteries is known by many names, including atherosclerotic heart disease (ASHD), coronary artery disease (CAD), atherosclerotic cardiovascular disease (ASCVD), and coronary heart disease (CHD). Regardless of the name, narrowing of the coronary arteries may lead to chest pain (angina), heart attack, heart failure, abnormal heart rhythms, and sudden cardiac death.

Atherosclerosis and angina pectoris

Angina pectoris, or angina, is the term used for chest pain that occurs when the blood and oxygen supply to the heart muscle cannot keep up with its needs to function. When a coronary artery is narrowed by more than 50 to 70 percent, 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. Just like legs that get tired and sore when you run too fast, not enough oxygen to the heart muscle causes pain or angina. This situation is called as myocardial ischemia (isch=holding back + emia=blood)

Angina pain in the chest can be described in many ways. It may be an intense pain or ache, pressure, heaviness, or squeezing across the chest. This pain may travel to the neck, jaw and teeth, to either shoulder and down the arm, or to the back. Symptoms that might be associated with the chest discomfort include shortness of breath, nausea, sweating, or lightheadedness.

Some patients experience the equivalent of angina, but without the pain. Instead, they may complain only of shortness of breath or early fatigue. This is especially true in patients with diabetes, who may experience little or no discomfort or pain at all.

Angina can be classified in many ways depending upon what situations might bring on the chest pain.

Exertional angina is pain that occurs with activity or a stressful situation. It should resolve when the patient stops and rests or takes medication like nitroglycerin to treat the anginal attack.

Rest angina occurs when the patient is sedentary, not moving, or wakens the patient from sleep.

Stable angina describes the situation where the angina is predictably reproducible with a specific activity level, for example when the patient has onset of chest pain after walking quickly for a mile, and then resolves almost immediately with rest.

Unstable angina occurs at rest or while sleeping, when one would expect that the work the heart might be expected to do would be minimal.

Episodes of angina are never normal and need to be reported to and evaluated by a health care provider promptly.

Atherosclerosis and heart attack

When the surface of a cholesterol plaque in a coronary artery ruptures, a blood clot may form on its surface, completely blocking the flow of blood in the artery beyond the clot. The lack of oxygen immediately causes the affected heart muscle tissue to suffer (myocardial ischemia), become irritable, and have difficulty contracting. If the situation is not reversed quickly, heart muscle will begin to die.

Some patients do not have previous symptoms that might warn them a heart attack could occur. There may be no warning symptoms of chest pain, shortness of breath, or fatigue. If these symptoms do exist, they should not be ignored.

The pain of a heart attack can be experienced and described in many ways.

• Chest discomfort might be pain, fullness, tightness, or squeezing. They all should be considered the same, as potentially coming from the heart.
• Jaw ache or pain, toothache
• Shortness of breath
• Nausea, vomiting, upper abdomen discomfort
• Heartburn and/or indigestion
• Sweating
• Discomfort radiating to the shoulder and down the arm. Either arm can be affected, but more often it is the left
• Upper back pain
• General malaise (vague feeling of illness)
• Symptoms that don't appear serious or severe and are ignored

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.

Chest pain should not be ignored. In people who do not have the diagnosis of coronary artery disease or angina, it may be very difficult to decide whether the chest tightness, shortness of breath, and nausea are due to a heart condition or some other cause. See a doctor if you have any of these symptoms.

Signs of a heart attack in men

Heart attacks occur when blood flow to a part of the heart is blocked, leading to damage to the heart muscle. Recognizing the symptoms early can be critical for timely medical intervention. While symptoms can vary, some common signs of a heart attack in men include:

• Chest pain or discomfort: One of the most classic signs is pain or discomfort in the chest. This often feels like heavy pressure, squeezing, fullness, or pain in the center of the chest. It may persist for more than a few minutes or may go away and return intermittently.
• Pain radiating to other areas: The discomfort may spread to other body parts, including the arms (especially the left arm), shoulders, neck, back, or jaw. This radiating pain can sometimes be a key indicator of a heart attack.
• Shortness of breath: This can occur with or without chest discomfort and may be sudden or progressive. It might feel like you cannot catch your breath or you are breathing more quickly than usual.
• Nausea or lightheadedness: Some men may experience nausea, vomiting, or lightheadedness, which can be accompanied by sweating or a cold sweat. This symptom can sometimes be mistaken for gastrointestinal issues.
• Unusual fatigue: Profound or unusual fatigue that seems out of proportion to normal tiredness may be a sign of a heart attack. This fatigue can occur suddenly or build up over a few days.
• Sweating: Breaking out in a cold sweat or sweating profusely without a clear reason can be a sign of a heart attack. This is often associated with other symptoms like chest pain or shortness of breath.
• Dizziness or weakness: Feeling dizzy or lightheaded, or experiencing an unexplained sense of weakness, can also be indicative of a heart attack.

It is important to note not all men will experience classic symptoms of a heart attack, and symptoms can vary. Some men may have mild symptoms or none at all, which can make it challenging to identify a heart attack immediately.

Symptoms of heart attack in women

Heart disease is the number one cause of death in women in the United States, yet women are more likely to encounter delays in establishing the diagnosis of heart attack than men. Part of that delay is the fact that women tend to minimize their myocardial infarction symptoms or ascribe them to less life-threatening conditions like acid reflux or the flu.

While heart attack symptoms in women are the same as those in men, women may also present with angina symptoms that are more subtle and may include the following, in isolation or in combination:

• Neck and shoulder pain
• Upper abdominal discomfort
• Nausea and/or vomiting
• Fatigue
• Shortness of breath

Silent heart attacks (heart attacks with few or no symptoms) cause almost half of all heart attacks and occur in both men and women.

There are many causes of chest pain that are not heart related, and often, people attribute their symptoms to other causes such as heartburn (gastroesophageal reflux or GERD) or chest wall muscle soreness.

While women will present with similar symptoms as men when having an acute myocardial infarction, depending upon the type of heart attack, they are less likely to receive the same aggressive care, including heart catheterization, angioplasty, and stenting (the procedure during catheterization where the blocked heart artery is reopened).

• When the heart attack diagnosis is made by changes seen on the EKG (please see the section on diagnosis), men and women receive the same care.
• When the diagnosis is made by blood tests (elevated troponin), women tend to get less aggressive care.

Women tend to not be as aggressively treated with medications compared to men, to limit the extent of a heart attack. These medications include aspirin, beta blockers, and statins.

After having a heart attack, women are less likely to be referred for cardiac rehabilitation and physical therapy.

A heart attack, or myocardial infarction, occurs when blood flow to a part of the heart muscle is significantly reduced or blocked for a prolonged period. This interruption in blood supply deprives the heart muscle of oxygen and nutrients, leading to damage or death of the affected heart tissue.

Here’s a step-by-step overview of the physiological events during a heart attack:

• Plaque formation and atherosclerosis: The process typically begins with atherosclerosis, where fatty deposits (plaques) accumulate on the inner walls of coronary arteries. These plaques are made up of cholesterol, fatty substances, cellular debris, and other materials.
• Plaque rupture and blood clot formation: When a plaque ruptures, it exposes the underlying tissue of the artery to the bloodstream. This triggers the clotting process as platelets adhere to the exposed tissue and form a blood clot.
• Obstruction of blood flow: The clot can grow large enough to block the artery partially or completely. When this happens, the blood supply to the portion of the heart muscle supplied by the affected artery is restricted or cut off. This blockage prevents oxygen-rich blood from reaching the heart muscle cells.
• Ischemia: The lack of blood flow leads to ischemia, a condition where heart muscle cells are deprived of oxygen. Ischemia causes the cells to become damaged and can lead to their death if the blood flow is not restored quickly.
• Heart muscle damage: As the heart muscle cells die, they release enzymes and other substances into the bloodstream. The severity of the damage depends on the size of the area affected and the duration of the blockage.
• Inflammatory response and healing: The damaged area of the heart muscle triggers an inflammatory response. The heart will attempt to repair itself, but the damaged tissue is replaced by scar tissue, which does not contract like healthy heart muscle. This can hinder the heart’s ability to pump blood efficiently.

How long does a heart attack last?

A heart attack typically lasts from a few minutes to several hours, depending on how severe the blockage is and how quickly medical treatment is administered. The pain or discomfort can vary in duration, but the longer the blockage persists, the greater the damage to the heart muscle. Immediate treatment is crucial to minimize heart damage and improve outcomes.

How painful is a heart attack?

The pain of a heart attack can range from mild discomfort to severe, crushing pain. It often feels like heavy pressure, squeezing, or fullness in the chest, which may also radiate to the arms, neck, jaw, or back. Some people describe it as the most intense pain they have ever experienced, while others may only feel mild discomfort or a sensation of tightness.

Seek medical attention immediately-call 911 for help

It is very important to seek prompt medical attention in the presence of new symptoms that may suggest a heart attack. Early diagnosis and treatment saves lives, and delays in reaching medical assistance can be fatal. A delay in treatment may lead to a permanently weakened heart due to heart muscle damage.

Sudden cardiac death is always a concern for health care providers. Monitoring for heart rhythm abnormalities, like ventricular fibrillation, is one of the first steps in caring for a patient with chest pain. That monitoring begins with paramedics on scene and continues throughout the care provided.

Factors that increase the risk of developing atherosclerosis and heart attacks include the following:

• High blood pressure (hypertension)
• High blood cholesterol and triglycerides (metabolic syndrome)
• Tobacco use
• Diabetes mellitus
• Male sex (although women may still be very much at risk)
• Family history of coronary heart disease

While you cannot change the risks of family history and being male, the other risk factors can be minimized by the use of medications and making positive changes in lifestyle.

High blood cholesterol (hyperlipidemia)

Cholesterol and triglyceride are lipids (fats) that can increase the risk of heart disease if their levels in the body are too high.

These compounds are transported in the bloodstream attached to lipoproteins, but all lipoproteins are not created equal.

• HDL (high-density lipoproteins) are considered “good” because they may help remove cholesterol from plaques in the artery wall.
• LDL (low-density lipoproteins) and VLDL (very low-density lipoproteins) are “bad” since they deposit cholesterol into artery plaques.

Blood tests can measure the levels of these fats and can direct treatment.

Losing weight, eating a healthy diet, and taking medications (statins) may help lower the bad cholesterol levels in the blood and decrease the risk of heart attack.

Patients who have other increased risks of heart disease may benefit from taking statins, even if their cholesterol levels are normal.

High blood pressure (hypertension)

High blood pressure is a risk factor for developing atherosclerosis and heart attack. Both high systolic pressure (the blood pressure as the heart contracts) and high diastolic pressure (the blood pressure as the heart relaxes) increase the risk of a heart attack.

Medications to treat high blood pressure and keep it controlled decrease the risk of heart attack and stroke.

Tobacco use (smoking)

Cigarette smoking is a major controllable risk factor in preventing heart disease. Men who smoke a pack of cigarettes per day have 3 times the chance of having a heart attack. That risk in women who smoke increases to 6 times the non-smoking population.

When a patient stops smoking, their risk drops 50% in the first year after quitting smoking and after two years, the risk returns to that of a nonsmoker.

Diabetes (diabetes mellitus)

Diabetes is a major risk factor for atherosclerosis and can affect all the arteries in the body. Diabetic patients, or those with elevated blood sugars or glycosylated hemoglobin (H1C), not treated with insulin or other medications are at higher risk for reduced blood flow to their heart (heart attack), legs (claudication), and brain (stroke).

Other complications of poorly controlled diabetes include peripheral neuropathy, altering their ability to feel pain, and chronic kidney disease (which can be another risk factor for heart attack).

Patients with diabetes may lower their risk of heart attack by controlling blood sugar levels, getting regular exercise, weight control, diet, and if needed, medication including insulin.

Male sex

Men are more likely to suffer heart attacks than women. As people get older, the risk of heart attack becomes the same for men and women.

Family history of heart disease

Individuals with a family history of coronary heart disease have an increased risk of a heart attack. The risk is highest if there is a first degree relative (parent or sibling) who has a heart attack at an early age: male younger than 55, female younger than 65.

It is important to know your family medical history. Many times, those details get lost, forgotten, or were never shared.

Coronary heart disease and heart attack do not discriminate by sex. Women have the same risks of having heart disease as men, and the risk factors for developing CAD in women are the same as in men. They include the following:

• High blood cholesterol
• High blood pressure
• Smoking cigarettes
• Diabetes mellitus
• Family history of coronary heart disease

Sudden death

When a person dies in the first minutes or hours after having a heart attack, it is most likely due to ventricular fibrillation (VFib), a heart rhythm disturbance.

The heart is a two-stage electric pump. Normally, an electric signal is generated by specialized cells in the upper chamber of the heart (atrium) and then spreads along the electrical pathways to the ventricle to allow all the heart muscle cells to contract in sync, and pump blood to the body.

When a heart attack occurs, heart muscle cells that lose their blood supply can become irritable and beat chaotically instead of together with the other muscle cells. Instead of generating a heartbeat, the ventricle fibrillates and no oxygen is delivered to the body. This is sudden death.

The treatment for sudden death is the same regardless of whether the patient collapses at home or in the hospital.

Outside the hospital, bystander CPR, calling 911 for help, and the use of an automatic external defibrillator (AED), increase the chance of survival.

The AED delivers an electrical shock (defibrillation) to the patient in VFib that may return the heart to normal rhythm and restore a heartbeat. CPR helps maintain some circulation in the body while attempts are made to defibrillate the heart.

In the hospital (and in ambulances), the heart attack patient may be on a monitor to continually check the heart rate and rhythm. If there are warning signs, medication can be used to try to stabilize the electrical activity of the heart and prevent VFib. If VFib does occur, CPR and defibrillation remain the first steps to restore a heartbeat.

Heart failure

Heart muscle that loses its blood supply and is damaged because of a heart attack is replaced by scar tissue. Depending upon how much muscle is damaged, the heart may no longer be able to beat as strongly and efficiently as before. The heart may not be able to pump blood to all parts of the body and supply the oxygen that is needed for normal function.

Symptoms of heart failure include fatigue, shortness of breath, cough, and swelling in the feet and ankles.

The diagnosis of a heart attack begins with patient history (family history, symptoms) and a high index of suspicion that a heart attack is happening. There is urgency to start the treatment as soon as possible. This is a medical emergency because the heart muscle begins to suffer and die almost immediately.

Whether in the emergency department or in the ambulance, the first steps are the same. Diagnosis and treatment happen at the same time when the suspicion is high for a heart attack.

Electrocardiogram (EKG, ECG)

The first step in the diagnosis of a heart attack is an electrocardiogram. The EKG maps the electrical activity of the heart by using patches or leads on the chest that can sense electricity. Each EKG usually has 12 leads that “look” at the heart’s electrical patterns from different directions.

Heart muscle that is losing its blood supply does not conduct electricity in the same way as normal heart muscle. These changes in the electrical pattern in the heart may be detected on the EKG, confirming the diagnosis. However, it may take many minutes for the changes to occur, so repeated EKG tracings may be done to see whether the EKG’s electrical pattern is evolving over time.

Sometimes the EKG can appear to be normal even when a heart attack and heart muscle damage is occurring.

Blood tests

Regardless of what the EKG may show, blood tests are performed if the diagnosis of heart attack is considered. Heart muscle cells that are stressed or injured leak chemicals into the bloodstream that can be measured.

Troponin is the preferred blood test to evaluate whether the cause of a patient’s complaints is a heart attack. This protein complex is not normally found in the blood, and its presence may confirm the diagnosis. This is especially important if the EKG is normal. However, it may take time for the levels of troponin in the blood stream to rise to a level where they can be measured. Depending upon the hospital, its lab and the clinical situation, the troponin blood test may have to be repeated after a few hours.

If the patient’s history, physical exam, and EKG confirm the diagnosis of heart attack, time is of the essence to try to re-establish blood flow to the heart muscle, either by removing the blood clot in the artery, or by dissolving it with medication.

If the EKG does not confirm a heart attack, the diagnosis will depend on the troponin lab test and supportive care will begin to protect the heart from damage.

In some patients, a heart attack may occur even when coronary arteries are not occluded. In approximately 6 percent of patients, the heart catheterization reveals normal heart arteries, yet blood tests confirm heart damage.

A heart attack is a medical emergency. The goal is to open the blocked coronary artery and return blood supply to the heart muscle and limit any potential damage or complication.

The first step that a patient, family member, or bystander can do is call 911 or seek medical care immediately.

Hospitals capable of percutaneous cardiac intervention (PCI), the ability of having a cardiologist perform a cardiac catheterization, identify the blocked artery, and then open it.

The PCI includes heart catheterization where dye is injected into the coronary arteries to find the blockage, potential removal of clot fragments, inserting a balloon to open the artery, and stenting where a small cage is placed across a narrowed portion of the artery to prevent it from narrowing again.

The goal is to perform that catheterization and open the blocked artery within 120 minutes or two hours of the patient arriving to the hospital door. Most hospitals train to bring that target time to less than 60 minutes.

During that time from door to catheterization (“cath”) lab, much needs to be done. The diagnosis must be made (remember that conditions other than heart attack can cause chest pain), the patient needs to be prepared for the procedure, and the cath lab and the team need to get ready. As well, other supportive medical myocardial infarction treatments will occur simultaneously.

If there is a delay for any reason, an alternative to heart catheterization is fibrinolytic therapy (fibrin=clot + lytic=dissolve). Intravenous medication (e.g., alteplase, tenecteplase) may be considered.

However, not all hospitals have the capabilities to perform heart catheterization. At those hospitals, the time frame expectations are no different, except that transport time to a PCI hospital must be considered when deciding to use a fibrinolytic.

Patients who have been treated with fibrinolytic therapy will still need a heart catheterization to deal with their heart issues.

While the patient is being prepared for the heart catheterization, other medications are used to protect the heart, including:

• Aspirin is used as an antiplatelet medication. Platelets help form blood clots and aspirin makes platelets less sticky.
• Nitroglycerin dilates blood vessels, and its goal is to increase blood flow to the heart muscle.
• Beta blockers (metoprolol) counter some of the effects of adrenalin in the body, slow the heart and make it beat more efficiently. This lessens the oxygen requirements for heart muscle cells.
• Other medications may be used before or during the heart catheterization to treat for clot prevention and heart function.
• The patient’s heart will be continually monitored, and should any heart rhythm disturbances be observed, medication will be used to control them and to prevent VFib.

Hormone therapy in women to decrease the risk of coronary artery disease is NOT recommended. The HERS studies did not show any benefit to estrogen treatment. Discuss the risk and benefit of any hormonal treatments with your doctor.

Women’s Health Initiative (WHI) trial results

Based upon the Women’s Health Initiative (WHI), the increased risk of coronary artery disease applies to older women who are more than 10 years past menopause.

While there is an increased risk of blood clots in the leg or to the lung, that risk is very small in otherwise healthy postmenopausal women. The risk increases if a clotting disorder, like factor V Leiden, is present.

The use of estrogen therapy for menopause symptoms may be reasonable with minimal risk, but patients should check with their health care provider. Those at risk for complications include patients with coronary artery disease, stroke, history of blood clots, liver disease, and breast cancer.

Every patient and every heart attack are different. Depending upon the initial health status of the patient, underlying medical conditions, and the size and severity of the heart attack, each patient will have a different journey in recovery.

Cardiac rehabilitation will help maximize outcome and the potential that each patient will reach. The goal is to return the patient to the same level of activity as before the heart attack. This may require significant changes in lifestyle to minimize risk of future heart damage.

The rehabilitation time is measured in months.

• Can a heart attack be cured? A heart attack cannot be cured, but its effects can be managed and minimized with prompt medical treatment and lifestyle changes. Treatments such as medications, procedures to restore blood flow, and cardiac rehabilitation can improve heart function and prevent further damage.
• What is the first aid for a heart attack? In the event of a suspected heart attack, emergency services (911) should be contacted immediately. While awaiting professional help, the person should be seated comfortably and remain calm. If they are not allergic to aspirin, a standard aspirin (chewed) may be administered to help prevent further clotting.
• How to avoid a heart attack. To avoid a heart attack, focus on adopting a heart-healthy lifestyle, including regular physical activity, a nutritious diet low in saturated fats and cholesterol, and avoiding smoking and excessive alcohol consumption. Additionally, regular checkups to manage risk factors such as high blood pressure, high cholesterol, and diabetes are crucial.