The heartbeat is controlled by the electrical system of the heart (Fig. 1). 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 (Fig. 2). Normal heartbeats can be seen in an Electrocardiogram or ECG.
Atrial Tachycardia is a heart arrhythmia, or irregular heartbeat. In atrial tachycardia, abnormal electrical pulses in the atria disrupt the normal firing of the SA node, the pacemaker of the heart (Fig. 3). This can be seen on an Electrocardiogram or ECG (Fig. 4). These signals cause the heart to beat rapidly, which does not give the heart enough time to fully refill with blood before pumping. This may cause the heart to not pump enough blood, which can lead to symptoms of dizziness, lightheadedness, and fainting.
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