Heart Attack (Myocardial Infarction): Types, Symptoms, Causes, Treatment & Prevention

Heart attack definition

A heart attack, medically termed myocardial infarction, is a life-threatening condition that needs emergency help and is caused by the lack of blood flow and oxygen to the portion of the heart muscle (myocardium).

Most heart attacks are often caused by blockages in coronary arteries; these are the blood vessels that supply (carry) oxygen to the myocardium. If the blockage happens to this artery, it can cause a deficit of oxygen in the heart muscle. However, a prolonged shortage of oxygen to the myocardium can lead to cell damage and death. This damage can result in chest pressure or pain, spreading to the jaw, neck, shoulder, or arm.

It may be silent and unnoticed, or it can also be a major event causing a rapid drop in blood flow, which can lead to decreased heart function and sometimes potentially cause sudden death. Noticing the early signs of a heart attack and getting timely treatment is essential and may save a person's life.

Myocardial infarction meaning

"Myocardium" means "heart muscle", and "infarction" means "cram or to plug up," which refers to the clogging of an artery, derived from the Latin word "infarcire."

Prevalence of heart attack

Coronary heart disease (CHD) is the fundamental cause of most deaths of men and women worldwide. The estimated annual deaths have risen from 0.226 crore to 0.477 crore. Cases of CHD may differ between urban and rural areas, ranging from 1.6% to 7.4% in rural areas and 1% to 13.2% in urban areas. Myocardial infarction, accountable for over 15% of annual deaths, is the most common type of CHD. The incidence of MI is higher in men in all age-specific groups than in women.

As per the INTERHEART studies, it was found that smoking 1–5 cigarettes every day has elevated the chances of developing an acute MI by 40%. This risk might be raised with the amount (number) of tobacco smoked per day.

Types of heart attacks

Types of heart attacks can be categorized based on ST segment, a measurement from an Electrocardiogram (ECG), and the level of troponin (heart protein) in the blood. The below-mentioned discusses the different types of heart attacks:

A myocardial infarction is a form of ACS (ACS refers to a range of conditions where the arteries that supply oxygen, nutrients, and blood get blocked) where there is a blockage in the coronary arteries. There are three types of ACS, include:

• ST-segment elevation myocardial infarction (STEMI)
• Non-ST segment elevation myocardial infarction (NSTEMI)
• Unstable angina

ST segment defines the patterns that are visible on an electrocardiogram, which is a display of a person's heartbeat.

• STEMI: It is a type of myocardial Infarction (type of MI) which is also called as classic or massive heart attack that is characterized by a complete blockage of the coronary artery and a prolonged interruption of blood supply, resulting in extensive damage to the heart, mainly affecting the lower chambers. It requires immediate treatment to unblock the artery.
• NSTEMI: It is another type of MI, also called a mini heart attack, which is characterized by partial blockage of the coronary artery and some scarcity of blood supply. Although it causes less damage to the heart, it is still serious and needs prompt diagnosis and treatment. This mini heart attack symptoms may resemble a regular heart attack symptom. 
• Unstable angina: It is also known as a silent heart attack, which can be similar to a STEMI heart attack and may be mistaken for indigestion, muscle pain, and more. It occurs due to excessive tightening of heart arteries, resulting in a drastic reduction of blood supply.

However, diagnostic tests may not show the damage to the heart. Although it is not seriously restricting the blood supply to the heart, it increases the risk of heart attack.

Heart attack symptoms

Massive heart attack symptoms might not be identical in every person and may vary from person to person. 50% to 80% of all heart attacks may be silent, where patients don't notice any symptoms. However, possible symptoms of heart attack include the following:

• Chest pain or discomfort: This pain may radiate to arms, shoulders, neck, back, jaw, or stomach (in some cases).

• Anxiety: It may be expected in patients with coronary heart disease (CHD), often displaying feelings of extreme worry.

• Profuse sweating: Pumping blood through blocked arteries may take more effort from the heart, leading to excess sweating for balancing the body temperature.

• Shortness of breath: The patient may not be able to take enough breath, along with chest discomfort.

• Light-headedness: It may be caused due to the reduced blood supply throughout the body.

• Rapid or irregular heart rate: If the patient's oxygen supply is decreased, it may disrupt the heart's electrical activity, resulting in fast or uneven heartbeats as a response to stress and damage to the myocardium.

• Indigestion, fullness, or choking feeling

• Nausea with or without vomiting

Patients having a heart attack often experience chest pain and might notice early warning signs of a heart attack such as fatigue, cold sweats, discomfort, or a general feeling of sickness in the days leading up to the attack. However, a particular type called ST-elevation myocardial infarction (STEMI) can occur suddenly without any warning signs.

Heart attack symptoms in women

Signs of heart attack in women include chest pain or discomfort, but they are more prone than men to experience heart attack without any chest pain or discomfort. Nausea, dizziness or extreme fatigue, and shortness of breath are the common heart attack symptoms in women. Women might experience these types of common symptoms before a heart attack, and most of them are similar to the symptoms of heart attack in men.

Heart attack causes​

Massive heart attack causes include the following:

• Coronary artery disease: Blockage or narrowing of coronary arteries. The leading cause of heart attack is a condition known as coronary artery disease. However, some (5%) heart attacks may occur due to another cause such as 

• Coronary artery spasm: Unusual narrowing of blood vessels.

• Coronary artery dissection: Sudden tear in the wall of a coronary artery.

• Uncommon medical conditions: Any disease that may cause unusual narrowing of blood vessels.

• Anomalous coronary arteries: A congenital heart defect.

• Stress cardiomyopathy or broken heart syndrome: A sudden weakness in heart muscle.

• Electrolyte imbalance: It is linked with cardiovascular emergencies and cause serious issues such as seizures, coma, and cardiac arrest

• Obstruction: Migrated from other areas in the body.

• Causes for sudden heart attack

• Hypertrophic cardiomyopathy: A condition that is characterized by the thickening of the heart muscle.

• Coronary artery abnormalities: A congenital condition that is characterized by a defect in one or more of the coronary arteries of the heart.

• Primary arrhythmias: Fluttering, racing, or pounding (irregular) heartbeats that occur within the heart.

• Arrhythmogenic right ventricular dysplasia: Uncommon, fatal disorder presented with dangerous heart rhythms.

• Myocarditis: Inflammation of the heart muscle called myocardium
• Marfan syndrome: An inherited condition that affects connective tissue.

The causes of a heart attack in women are the same as in men. However, women are more prone to MI that are not caused by coronary artery disease than men.

Heart attack risk factors

Heart attack risk factors are strongly associated with coronary artery disease (CAD). The following are the modifiable and non-modifiable risk factors of heart attack:

INTERHEART study identified many modifiable risk factors for CAD. The following are the myocardial infarction modifiable risk factors:

• Smoking: As per the INTERHEART studies, it was found that smoking causes heart attacks by increasing the formation of plaque in blood vessels.

• Hypertension: It may increase the workload of the heart, leading to structural and functional changes in heart muscle. As per some studies, it was proved that untreated high BP causes heart attack or increases the risk of heart disease.

• Diabetes mellitus: Elevated blood sugar levels may harm the nerves and the blood vessels that control the person's heart.

• Abnormal lipid profile: Having a high lipid can raise the chances of development of heart disease.

• Alcohol consumption: Consuming can raise blood pressure and heartbeat, which may increase the workload on the heart and the risk of heart disease.

• Lack of physical activity: Sedentary lifestyles may lead to weight gain, which elevates the risk of high blood pressure, cholesterol, and diabetes.

• Obesity: Obese persons tend to have more blood, due to that, the heart pumps harder and may lead to heart disease over time.

• High-stress levels: Increased stress levels can release cortisol (stress hormone) and temporarily raise blood pressure. Chronic (long-term) stress can lead to increased blood pressure.

These factors should be modified to aid in reducing the risk of heart disease. Heart attack causes, and risk factors are not the same but might be linked in many cases.

The following are the non-modifiable risk factors for myocardial infarction:

• Older age: The risk of heart attack may increase as a person gets older
• Male gender: Males are more suspectable to heart attack than woman
• Family history: A family history of stroke or heart disease may raise the risk of heart disease

Heart attack complications

Heart attack complications can be serious, and include as the following:

Ischemic (common in first few days)

• Angina pectoris: It is a condition that is characterised by chest pain caused by decreased blood flow to the myocardium
• Extension of infraction: Damage to a new area occurring after the first injury
• Reinfarction: Another heart attack (second heart attack) that occurs after the first heart attack

Arrhythmias (within 1–3 days)

• Sinus bradycardia: Slow heart rate that develops in the sinus node and 
• Atrioventricular block: Disruption of electrical signals between the lower and upper chambers of the heart, leading to slowed conduction of signals
• Supraventricular arrhythmia: Unusual or abnormal heartbeat originates in atria (upper chambers) or
• Ventricular arrhythmia: Unusual or abnormal heartbeat originates in the ventricles (lower chambers)

Mechanical (usually 1st week to 1st month)

• Cardiogenic shock: Severe damage to heart muscles 
• Heart rupture: Where the heart’s muscles, valves, or walls split apart
• Heart failure: Heart muscle cannot pump enough blood 
• Myocardial dysfunction: It refers to a range of conditions that cause weakened heart muscle

Embolic (within first 2 weeks)

• Pericardial embolus: Blockage in a blood vessel that 
• Left ventricular mural thrombus: Blood clot that develops in the inner wall of the left ventricle

Inflammatory: (first week to months)

• Pericardial effusion: Blocks blood supply to the heart sac
• Pericarditis: Inflammation and swelling of thin, sac-like tissue called pericardium (surrounds the heart)

The post heart attack complications may happen rapidly after a heart attack and become a cause of death. Within the 1st month after the heart attack or before reaching the hospital, some individuals die suddenly from a complication of heart attack.

Heart attack diagnosis

Heart attack diagnosis tests may start with a physical exam by a cardiologist using a stethoscope to find the abnormal sounds in the lungs (crackles). The following are the tests that might be performed to check heart health as well as to confirm the heart attack:

• History and symptoms
• Blood tests
• Electrocardiogram (ECG)
• Coronary angiography
• Exercise stress test
• Nuclear stress test

Silent heart attack diagnosis tests include electrocardiogram or echocardiogram stress test.

Heart attack treatment

If the patient receives heart attack treatment faster, there is a better chance to survive and alleviate the symptoms. It includes the following:

• First aid treatment for heart attack
• Medical management of myocardial infarction
• Surgical management of myocardial infarction

First aid treatment for heart attack

It is crucial to provide emergency management to a heart attack patient to prevent significant heart damage. Management of myocardial infarction may be classified into two types in the hospital as follows:

• Medical management of myocardial infarction
• Surgical management of myocardial infarction

The goal of the treatment is to restore blood flow quickly to reduce damage to the heart muscle. A cardiologist can choose the type of management based on the type of heart attack the patient has had and the overall condition of the patient.

Medical management of myocardial infarction

It is also called the pharmacological management of myocardial infarction, where medications are used to treat the heart attack. Medications for heart attack include the following:

• Thrombolytic therapy
• Oxygen therapy
• Anti-emetic drugs
• Pain medications
• Beta-blockers
• Blood thinners
• ACE inhibitors
• Statins
• Nitrates
• Antihypertensive drugs

Surgical management of myocardial infarction

Before proceeding with emergency surgery, a cardiologist may recognize signs of a heart attack, including an increased heartbeat and an irregular pulse. Blood pressure may initially be elevated but can drop later, leading to hypotension and cardiogenic shock, where the heart cannot pump enough blood and oxygen. The following surgical procedures can be performed by cardiothoracic surgeons or interventional cardiologists based on the patient's needs and condition:

• Percutaneous Coronary Intervention (PCI)
• Balloon angioplasty
• Stent placement
• Coronary Artery Bypass Grafting (CABG) or bypass surgery
• Heart valve surgery
• Heart transplant

After a heart attack, cardiac rehabilitation and lifestyle modifications can help patients recover.

Heart attack prevention​

Prevention of myocardial infarction may depend on many factors. It is not possible to control some risk factors, such as age and sex. However, many ways can help a person reduce the risk of a heart attack. These include:

• Getting regular health checkups: A checkup of overall health every year might detect early warning signs of heart disease, including symptoms that patients cannot feel.

• Stopping smoking: Quitting smoking and all vaping products can decrease the risk of heart disease.

• Maintaining a healthy weight: This may help prevent cholesterol deposition in arteries.

• Exercising regularly: Moderate physical activity four to five days a week can help achieve a healthy weight and lower the risk of heart attack.

• Managing the stress: Stress can increase the risk of heart disease; controlling the stress may help stay away from it.

• Eating healthy food: A healthy, balanced diet, which contains high protein and fibre foods, and avoiding highly saturated foods, is advised.

• Managing the existing conditions: Medical conditions, including high blood pressure, diabetes, obesity, etc, may increase the risk of heart disease. It is recommended to manage them to avoid getting heart problems.

• Limiting alcohol intake: Alcohol consumption can raise blood pressure and heart rate. Hence, a person may be less likely to get heart disease by limiting alcohol.

Patients have to take the prescribed medicine for heart attack prevention regularly.

Difference between cardiac arrest and heart attack

Cardiac arrest vs heart attack

Cardiac arrest and heart attack are the conditions that cause damage to the heart. Although these are similar, they have some differences:

Difference between heart failure and heart attack

Heart failure vs heart attack

Heart failure and heart attack are both types of heart disease. Although they have some common causes, they may also differ in many ways such as:

Difference between panic attack and heart attack

Panic attack vs heart attack