What causes AVNRT?

What causes AVNRT?

Electrical signals control the rate and rhythm of your heart. They start in the sinoatrial (SA) node, a special group of muscle fibers in your heart’s upper right chamber (atrium). The SA node is your heart’s natural pacemaker.

In a healthy heart, an electrical impulse from the sinoatrial node makes the two upper chambers (the atria) contract (pump). The impulse then travels through pathways to the atrioventricular (AV) node and into your heart’s two lower chambers (the ventricles). The AV node acts as a gate between the upper chambers and the lower chambers.

That is how a normal heart moves blood through the chambers and into the rest of your body. But a problem with your heart’s electrical system can cause an abnormal heartbeat (irregular, too fast or too slow). That’s called arrhythmia.

SVT is one type of arrhythmia, and AVNRT is the most common type of SVT.

In AVNRT, a premature contraction occurs. The heart has a small extra pathway near the AV node, called a reentrant circuit. The early contraction can make the electrical impulse enter the circuit and circle around. That can cause sudden sustained fast heartbeats.

Some families may have several members with the condition, suggesting that AVNRT can be inherited, but research has not yet found a genetic explanation.