Heart attack (myocardial infarction): Symptoms, cause and treatment

Heart attack or myocardial infarction (MI) is a non-communicable chronic condition of the heart that occurs due to blockage of one or more blood vessels (coronary arteries) that supply blood to the heart. Due to the blockage, the coronary artery cannot supply oxygen-rich blood to the heart muscles making the heart starve of oxygen and ultimately leads to its death. 

If there is a widespread death of the heart muscles, the heart stops beating causing heart failure (cardiac arrest). The blockage of the coronary artery can be partial or complete, characterizing the two types of a heart attacks. They are: 

• ST-elevation myocardial infarction (STEMI), which occurs when there is complete blockage of the coronary artery 
• Non-ST-elevation myocardial infarction (NSTEMI) is caused when there is partial blockage of the coronary artery 

Symptoms 

The common symptoms associated with heart attack include: 

• Severe squeezing type chest pain that can radiate to the left arm, neck, back, and abdomen 
• Tightness and heaviness in the chest 
• Dizziness 
• Shortness of breath 

• Anxiety 
• Increased heart rate and irregular pulse 
• Coughing and wheezing 
• Nausea and vomiting 
• Cold body and sweating 

Though a heart attack is sudden, warning signs could be present days or weeks in advance manifesting as minimal chest pain that gets relieved after rest (angina). The chest pain is often severe, but it can sometimes radiate to the esophageal region which can mimic heartburn. It is always better to seek a doctor’s consultation when in doubt. 

Causes 

Coronary artery disease (CHD) is the major cause of most heart attacks. It is a condition where fats, cholesterol and other substances get deposited in the coronary artery. These deposits become hard over time and are called plaque, which narrows the artery and partially obstructs the blood flow to the heart. 

In other cases, plaques get ruptured and a blood clot forms at the site of rupture. Some blood clots get stuck in the coronary artery due to their large size and completely block the flow of blood. In both the above cases, the heart starves of oxygen leading to chest pain (due to exertion on the heart) and death of heart muscles (due to a lack of oxygen).
There are several factors that are associated with MI are: 

• Age 
• Gender (men are at more risk than women) 
• Diabetes mellitus 
• High blood pressure 
• High cholesterols/lipids 
• Smoking (active and passive) 
• Family history of heart diseases 
• Sedentary lifestyle 
• Medications (oral contraceptives) 

Using drugs such as cocaine and amphetamines can constrict the coronary artery and restrict blood flow, apart from other illnesses that starve the heart of oxygen which could also trigger a heart attack. 

Diagnosis 

A series of tests and inferences are made to diagnose the type, location of heart muscle damage and severity of heart attack. A typical diagnosis requires at least two positive signs of a heart attack which include history of cardiac ailments or MI symptoms, electrocardiogram and cardiac markers. Some of the best diagnostic methods are: 

• A physical examination can lead to the assessment of signs and symptoms, medical history, family history and lifestyle to predict a heart attack 
• Electrocardiogram (ECG) is a painless method to determine how well the heart is functioning and determine the type of heart attack 
• Echocardiograms use sound waves to build an internal picture of the heart and helps in inferring the exact areas of heart damage 
• Blood tests can detect cardiac markers such as proteins troponin T and I, and enzymes like creatinine kinase-MB that are required in the functioning of the heart and get leaked from damaged heart muscles 

• Cardiac angiography helps to determine whether there is a blockage or narrowing along with its exact location 
• Chest X-rays are helpful in evaluating when the heart attack is uncertain. It shows if there are any other predisposing factors such as air pockets in the lungs, or fluid buildup between the layers of the lungs or heart 
• Cardiac MRI or CT scans can show the exact location and extent of damage of heart muscle or coronary artery 

Treatment 

To prevent more damage to the heart muscle due to lack of blood perfusion, restoring the blood flow quickly is vital. There are certain medications and surgical methods to treat and improve the quality of life of individuals that have experienced a heart attack. 

Medications can treat and reduce the risk of heart attack in various ways. These include: 

• Breaking down of clots with medications such as reteplase, streptokinase, t-PAs, tenecteplase 
• Preventing or reducing the formation of blood clots using aspirin or clopidogrel 
• Blood-thinners such as heparin and warfarin reduce the stickiness of blood 
• Using nitroglycerine to dilate blood vessels that have narrowed 

• Beta-blockers such as atenolol and metoprolol, ACE inhibitors such as captopril and lisinopril reduce blood pressure 
• Statins such as atorvastatin, rosuvastatin help in controlling cholesterol levels 
• Morphine can be used to relieve chest pain 

Surgical methods that treat heart attack are: 

• Percutaneous coronary intervention (PCI), which dilates the blocked area of the coronary artery for long term by using a metal mesh stent 

• Coronary Artery Bypass Graft (CABG) in which a blood vessel from another part of the body (chest, leg, or arms) is grafted below and above the blockage area of the coronary artery to divert the blood flow and improve blood supply to the heart. It is done when there are several blockages in the artery or there are many branches coming off from the blocked artery. 

First-Aid to increase chances of survival: 

Every minute counts. 

As soon you start experiencing intense squeezing chest pain, the first you should do to call the hospital emergency or let your friend or neighbour drive you to the nearby hospital.  

An individual with a history of heart attack might be prescribed nitroglycerine and aspirin. In case they feel congestion and intense chest pain, these medicines can be taken as directed by their physician to decrease the risk of mortality. 

However, in case, you see a person getting unconscious and not breathing, give CPR (cardiopulmonary resuscitation) at the earliest. Also, use AED (automated external defibrillator) if available immediately by following the device instructions for using it. 

 Sources 

• https://www.nhs.uk/conditions/heart-attack/ 
• https://www.nhp.gov.in/disease/cardio-vascular/heart/myocardial-infarction-heart-attack 

• https://www.heart.org/