In automatic tachycardia, phase 4 elevation indicates increased automaticity. which statement is true?

In automatic tachycardia, phase 4 elevation indicates increased automaticity. which statement is true?

• A. Phase 4 elevation is associated with automatic tachycardia
• B. Phase 0 elevation is associated with automatic tachycardia
• C. Phase 2 elevation is associated with automatic tachycardia
• D. Phase 3 elevation is associated with automatic tachycardia

Answer: (A)

In automatic tachycardia, the key feature is increased automaticity of ectopic pacemaker tissue, which shows up as elevated phase 4 depolarization. This diastolic depolarization brings the membrane potential toward the threshold more quickly, so impulses fire spontaneously at a faster rate, independent of the SA node. Phase 0 is the rapid upstroke for conduction, and phases 2 and 3 are the plateau and repolarization phases; they drive contraction and electrical recovery, not the spontaneous firing that defines automaticity. Thus, phase 4 elevation directly reflects the mechanism behind automatic tachycardia.

In automatic tachycardia, the key feature is increased automaticity of ectopic pacemaker tissue, which shows up as elevated phase 4 depolarization. This diastolic depolarization brings the membrane potential toward the threshold more quickly, so impulses fire spontaneously at a faster rate, independent of the SA node. Phase 0 is the rapid upstroke for conduction, and phases 2 and 3 are the plateau and repolarization phases; they drive contraction and electrical recovery, not the spontaneous firing that defines automaticity. Thus, phase 4 elevation directly reflects the mechanism behind automatic tachycardia.