Ischemic Ventricular tachycardia is an abnormally rapid heartbeat that is caused by an abnormal firing of electrical signals in a damaged area of the ventricle.
The electrical system of the heart is made up of several parts that communicate with one another to signal the heart muscle fibers when to contract (see fig. 1). The SA node starts the signal causing the atria to contract. This signal travels through the AV node and on to the bundle of His, bundle branches, and Purkinje fibers causing the ventricles to contract. The flow of electrical signals is what produces a normal heartbeat (see fig. 2).
In ischemic ventricular tachycardia, abnormal firing of electrical signals in the ventricle interfere with the normal flow of electrical signals (see fig. 3 and 4). Tissue that is damaged by lack of blood flow (ischemia) slows electrical signals. This delay in the damaged tissue can then allow the electrical signal to reemerge and cause the ventricle to contract again with out proper signaling from the AV node. The rapid heartbeat does not allow enough time for the heart to fill before it contracts so blood flow to the rest of the body is compromised which may lead to symptoms of dizziness, lightheadedness, unconsciousness, and cardiac arrest.
Figure 1: Parts of the electrical system of the heart.
Figure 2: Flow of electrical signals in a normal heartbeat.
Figure 3: Ventricular tachycardia with abnormal signals originating in a damaged portion of the ventricles.
Figure 4: Normal ECG compared with ventricular tachycardia ECG.
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