HeartyBeats

The contraction of the atria and ventricles makes a heartbeat. When your heart beats, it makes a “lub-DUB” sound. You may have heard this if you listened with a stethoscope or with your ear on someone's chest.

After your atria pump blood into the ventricles, the valves between the atria and ventricles close to prevent backflow. The “lub” is the sound of these valves closing.

After your ventricles contract to pump blood away from the heart, the aortic and pulmonary valves close and make the “dub” sound.

Electrical activity

Electrical signals cause muscles to contract. Your heart has a special electrical system called the cardiac conduction system. This system controls the rate and rhythm of the heartbeat.

With each heartbeat, an electrical signal travels from the top of the heart to the bottom. As the signal travels, it causes the heart to contract and pump blood. The heartbeat process includes the following steps.

The signal begins in a group of cells, called pacemaker cells, located in the sinoatrial (SA) node in the right atrium.

The electrical signal travels through the atria, causing them to pump blood into the ventricles.

The electrical signal then moves down to a group of pacemaker cells called the atrioventricular (AV) node, located between the atria and the ventricles. Here the signal slows down slightly, allowing the ventricles time to finish filling with blood.

The AV node fires another signal that travels along the walls of your ventricles, causing them to contract and pump blood out of your heart.

The ventricles relax, and the heartbeat process starts all over again in the SA node.

Some conditions affect the heart's electrical system. Examples are included below.

Arrhythmia is an irregular heart rhythm. Atrial fibrillation is one of the most common types of arrhythmia.

Conduction disorders can happen when electrical signals either do not generate properly, do not travel properly through the heart, or both.

Blood pressure

Your blood pressure is the force of the blood pushing against the walls of your arteries as the heart pumps blood. It is made up of two numbers: systolic and diastolic.

Systolic pressure is the pressure when the ventricles pump blood out of the heart. The pressure on your arteries is highest during this time.

Diastolic pressure is the pressure between beats, when the heart is filling with blood. The pressure on your arteries is lowest during this time.

For most adults, healthy blood pressure is usually less than 120 over 80, which is written as your systolic pressure number over your diastolic pressure number.

High blood pressure is what happens when blood flows through blood vessels at higher-than-normal pressures

Arrest

Cardiac arrest happens because of an electrical issue that makes your heart stop beating. When your heart stops pumping blood, you become unconscious. Cardiac arrest can be fatal in minutes. This is why bystanders should call for help and start CPR immediately. A person’s chances of survival are best when they get help right away.

What is cardiac arrest?

Cardiac arrest happens when your heart stops beating or beats so fast that it stops pumping blood. During cardiac arrest, victim typically collapse and become unresponsive. Symptoms may occur without warning. This is why people also call it sudden cardiac arrest.

This life-threatening condition can become fatal if you don’t get immediate treatment.

During cardiac arrest (cardiopulmonary arrest), your heart isn’t pumping blood anymore. Within minutes, this puts your organs and whole body at risk of death because they must constantly receive oxygen. Your blood delivers that oxygen.

Emergency treatment includes cardiopulmonary resuscitation (CPR) and defibrillation. CPR keeps enough oxygen in your lungs and gets it to your brain until an electric shock restores a normal heart rhythm. CPR and defibrillators may save your life.

Call 112 (or your local emergency services number) if you see someone drop to the ground and you suspect sudden cardiac arrest