(VT) An electrical heart rhythm disturbance that originates in the lower chambers and occurs when the heart beats too frequently at rest. VT is characterized by a rapid heart rhythm during which patients may feel faint or dizzy, or even pass out. During VT, the heart does not pump blood as efficiently as it does during a normal rhythm, and rapid contractions prevent the ventricles from filling adequately with blood between beats. VT often progress to VF (cardiac arrest).
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