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. This organized flow of electrical signals produces a normal heartbeat. Normal heartbeats can be seen in an Electrocardiogram or ECG.
During ventricular tachycardia, accelerated abnormal electrical pulses in the lower chambers, or ventricles, disrupt the normal firing of the SA node, causing the heart to beat rapidly.
During Right Ventricular Outflow Tract (R.V.O.T.) Ventricular Tachycardia, abnormal signals originate in the right ventricle near the pulmonary valve, also known as the right ventricular outflow tract. RVOT ventricular tachycardia can be seen on an electrocardiogram.
A rapid heartbeat does not give the heart enough time to refill with blood before pumping, which causes diminished blood flow to the rest of the body. This may lead to symptoms of dizziness, lightheadedness, and unconsciousness.
Figure 1: Parts of the electrical system of the heart.
Figure 2: Flow of electrical signals in a normal heartbeat.
Figure 3: RVOT VT with abnormal signals originating from fast and slow pathways in the AV node.
Figure 4: Normal ECG compared with RVOT VT ECG.
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