Causes

To understand the cause of heart arrhythmias, it may be helpful to know how the heart typically works.

How does the heart beat?

The heart is made of four chambers — two upper chambers (atria) and two lower chambers (ventricles).

The heart's rhythm is normally controlled by a natural pacemaker (the sinus node) in the right upper chamber (atrium). The sinus node sends electrical signals that normally start each heartbeat. These electrical signals move across the atria, causing the heart muscles to squeeze (contract) and pump blood into the ventricles.

Next, the signals arrive at a cluster of cells called the AV node, where they slow down. This slight delay allows the ventricles to fill with blood. When the electrical signals reach the ventricles, the chambers contract and pump blood to the lungs or to the rest of the body.

In a healthy heart, this heart signaling process usually goes smoothly, resulting in a normal resting heart rate of 60 to 100 beats a minute.

Things that can cause an irregular heartbeat (arrhythmia) include:

• Current heart attack or scarring from a previous heart attack
• Blocked arteries in the heart (coronary artery disease)
• Changes to the heart's structure, such as from cardiomyopathy
• Diabetes
• High blood pressure
• Infection with COVID-19
• Overactive thyroid gland (hyperthyroidism)
• Sleep apnea
• Underactive thyroid gland (hypothyroidism)
• Certain medications, including cold and allergy drugs bought without a prescription
• Drinking too much alcohol or caffeine
• Drug abuse
• Genetics
• Smoking
• Stress or anxiety