Would you know what to do if a loved one — or even a stranger — went into cardiac arrest? Knowing what to do in this emergency situation, and administering cardiopulmonary resuscitation (CPR), could save a life. CPR, which involves making chest compressions on the person affected, helps increase blood flow to the organs¹ until more advanced treatment is available.

In the video above, CNN’s Dr. Tara Narula demonstrates how to perform hands-only CPR if you witness someone go into cardiac arrest. If more people learn this simple technique, it could have major implications for public health as, currently, about 350,000 Americans die annually from cardiac arrest. That’s more than the number of deaths from colorectal cancer, breast cancer, prostate cancer, influenza, pneumonia, auto accidents, HIV, firearms and house fires combined.²

Cardiac arrest occurs suddenly due to a malfunction in the heart that causes it to stop beating. Some cases of cardiac arrest have no symptoms. In other instances, the following symptoms may occur prior to the event:³

Fatigue

Dizziness

Shortness of breath

Nausea

Chest pain

Heart palpitations (fast or pounding heart beat)

Loss of consciousness

While blood loss, lack of oxygen and high levels of potassium and magnesium — which can cause arrhythmia, or irregular heartbeat — can lead to cardiac arrest, there are three primary causes:⁴

1. Arrhythmia — An electrical signal in the heart may lead to an irregular heartbeat known as ventricular fibrillation, which is the No. 1 cause of cardiac arrest. It describes a heartbeat so rapid that the heart trembles instead of pumping blood.

2. Cardiomyopathy (enlarged heart) — This leads to abnormal heart contractions.

3. Coronary artery disease — If coronary arteries become blocked by plaque, it restricts blood flow to the heart. Left untreated, this may lead to heart failure or arrhythmia, which can trigger cardiac arrest.