The heartbeat is controlled by the electrical system of the heart. This system is made up of several parts that tell the muscle of the heart when to contract. The SA node starts the heartbeat, causing the atria, or upper chambers of the heart, to contract. The signal then travels through the AV node, bundle of His, bundle branches, and Purkinje fibers. This causes the ventricles, the lower chambers of the heart, to contract. The flow of electrical signals produces a normal heartbeat. Normal heartbeats can be seen in an Electrocardiogram or ECG.
Supraventricular Tachycardias include a group of heart arrhythmias, or irregular heartbeats that originate in the atria. In each of these conditions, electrical signals begin in the atria, sending abnormal signals to the ventricles. These irregular heartbeats can be seen on an Electrocardiogram or ECG. SVTs include several different types of arrhythmias, such as atrial fibrillation, atrial flutter, atrial tachycardia, AVNRT, and AVRT (WPW). All of these arrhythmias cause the ventricles to contract too fast or irregularly, making them less efficient at pumping blood. These tachycardias can lead to symptoms of dizziness, lightheadedness, or chest pain.