If you encounter someone who is unconscious from a presumed heart attack, call for emergency medical help. If you have received training in emergency procedures, begin cardiopulmonary resuscitation (CPR). This helps deliver oxygen to the body and brain.
According to guidelines by the American Heart Association, regardless of whether you’ve been trained, you should begin CPR with chest compressions. Press down about 2 inches (5 centimeters) on the person’s chest for each compression at a rate of about 100 a minute. If you’ve been trained in CPR, check the person’s airway and deliver rescue breaths after every 30 compressions. If you haven’t been trained, continue doing only compressions until help arrives.
Sudden cardiac arrest during a heart attack is commonly caused by a deadly heart rhythm in which the heart quivers uselessly (ventricular fibrillation). Without immediate treatment, ventricular fibrillation leads to death. The timely use of an automated external defibrillator (AED), which shocks the heart back into a normal rhythm, can provide emergency treatment before a person having a heart attack reaches the hospital. But, if you’re alone, it’s important to continue chest compressions. If there’s a second person present, that person can look for a nearby AED.

Angina and Coronary Artery Disease

Angina is pain or discomfort that comes when your heart does not get enough oxygen. Angina is usually a symptom of a heart problem known as coronary heart disease (CHD), also called coronary artery disease (CAD)
Your heart is a muscle. It pumps oxygen-rich blood to your whole body. Your heart also needs oxygen to work. Blood vessels called coronary arteries carry blood with oxygen to your heart.
In healthy coronary arteries, blood flows freely to bring oxygen to the heart. In coronary heart disease, these arteries become stiff and narrow. This lowers blood flow and the amount of oxygen that gets to the heart.

With exercise or emotional stress, the heart works harder and needs more oxygen. Lower blood flow can lead to angina. You could feel discomfort or pain in the chest, arm, shoulder, back, neck, or jaw. When angina has been present for months or years without much change, it is called chronic stable angina. It most often goes away with rest or nitroglycerin.
If a clot forms in a coronary artery, it can further block blood flow. This can lead to chest pain known as unstable angina. It often occurs at rest. Unstable angina is a medical emergency and requires medical help right away.