Atrial Fibrillation
Chaotic re-entrant electrical activity replaces organised atrial contraction, so the atria quiver rather than pump, producing an irregularly irregular pulse and blood stasis that drives thromboembolic risk independent of how the rhythm is managed.
First principles
Why the pulse is irregularly irregular
Instead of a single organised wave spreading from the sinus node, multiple chaotic re-entrant wavelets fire continuously across the atria, so no coordinated P wave or atrial contraction occurs. The AV node is bombarded with far more impulses than it can conduct and lets through an unpredictable, randomly timed subset, producing a ventricular rhythm with no discernible pattern: an irregularly irregular pulse and an absence of P waves on the ECG.
Educational content pending clinical review. Not medical advice.