Any disruption in the usual electrical pathways in your heart can cause an abnormality in your heart rhythm. This is called an arrhythmia.
Abnormal heart rhythms that begin in the upper chambers of the heart are usually rapid. People who experience supraventricular arrhythmias may feel dizzy or light-headed, or have chest tightness or palpitations. Some people do not have any symptoms at all.
Supraventricular arrhythmias can last for only a few seconds or for prolonged periods of time. In general, they are usually not life threatening. However, they can disrupt the regular flow of blood throughout your body and cause you to feel unwell or have other, more serious, symptoms.
Types of Supraventricular Arrhythmias
Atrial fibrillation is an irregular heart rhythm that occurs when the SA node does not generate normal electrical impulses. Instead, the atria start to trigger rapid and disorganized electrical signals, causing the atria to quiver rather than contract normally. These abnormal impulses randomly pass through to the ventricles, resulting in an irregular and inefficient heartbeat.
Atrial flutter is similar to atrial fibrillation but less common. In atrial flutter, the electrical impulse that starts in your atria gets disrupted, interrupting its normal flow to the AV node. This creates a circular feedback loop and sets off a series of rapid-fire impulses, causing your heart to beat quite fast for periods of time. Patients with atrial flutter often also have atrial fibrillation.
Tachycardia is a rapid heart rhythm that occurs when there is a disruption in the normal electrical pathways. There are various types of supraventricular tachycardias.
- Atrial Tachycardia: With atrial tachycardia, the electrical impulse starts somewhere in the atria other than the SA node. This causes an abnormally rapid heart rate.
- AV Node Re-entrant Tachycardia: AV node re-entrant tachycardia occurs when the electrical impulse gets caught up in extra fibres around the AV node and starts to rapidly circle the AV node. This causes a rapid heart rate.
- AV Re-entrant Tachycardia (AVRT)/Wolff-Parkinson-White (WPW) Syndrome: People with AVRT/WPW syndrome were born with an extra electrical pathway in their heart that connects the atria and the ventricles, but completely bypasses the normal AV node pathway. When the electrical impulse goes through the extra pathway, it can cause periods of very rapid heartbeats.
Ventricular arrhythmias occur in the lower part of the heart and can be a bit more dangerous. During ventricular tachycardia, the heart beats so fast that it cannot properly pump blood to the rest of the body. This can cause extreme dizziness, fainting or sometimes a complete collapse.