Which rhythm can precede blocks or Asystole?

Which rhythm can precede blocks or Asystole?

• A. Premature Atrial Complex
• B. Normal Sinus Rhythm
• C. Atrial Flutter
• D. Junctional Rhythm

Answer: (A)

Premature atrial complexes are early impulses arising in the atria above the AV node. They often occur before the regular beat and can travel through the AV node normally, but sometimes they arrive when the AV node is refractory. In that case, the impulse is blocked and no QRS follows the premature P wave, producing a compensatory pause. That pause can appear as a block or as a brief moment of no ventricular activity, resembling asystole on the strip. So this rhythm is the one that can precede a block or a transient asystolic pause.

Normal sinus rhythm would continue with regular conduction and isn’t driven by a premature impulse that causes a pause. Atrial flutter shows a rapid, regular atrial rhythm with characteristic flutter waves, not a single premature beat that can be blocked to produce a pause. Junctional rhythm originates in the AV junction and has different P/QRS timing and morphology, and it’s not described by a premature atrial impulse causing a block followed by a pause.