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Atrial Fibrillation (SVR)

caution
Lead II
25 mm/s10 mm/mV
HR
72
bpm
RR
833
ms
QT
328
ms
Type

Atrial Fibrillation (SVR)

Atrial fibrillation in which the AV node conducts poorly, giving a slow ventricular rate (<60 bpm) while the rhythm stays irregularly irregular. Points to AV-nodal disease or rate-controlling drug effect.

Recognition· 4
  • Irregularly irregular rhythm
  • No P waves (fibrillatory baseline)
  • Narrow QRS, ventricular rate <60 bpm
  • Still irregular — if it goes regular, think complete heart block
Mechanism

Same chaotic atria — but the AV node blocks most impulses

The atria fire chaotically as in any AFib, but a poorly-conducting AV node (disease, vagal tone, or rate-control drugs) passes few impulses through, giving a slow but still irregularly irregular ventricular response.

Findings· 2
  • Irregularly irregular, no discrete P waves (fibrillatory baseline), narrow QRS, ventricular rate <60 bpm with long, obviously variable RR gaps.
  • CAUTION: if it becomes slow AND regular, suspect complete heart block with a junctional/ventricular escape (regularized AFib) — a different, higher-acuity finding.
Clinical Impact
Symptomatic bradycardia (fatigue, syncope)
↓
Over-aggressive rate-control drug effect
↓
Underlying complete AV block if the rhythm regularizesRISK

Slow + irregular → review drugs; slow + regular → suspect heart block

Management· 2
1

Primary Treatment

Review and reduce AV-nodal blocking drugs; assess for intrinsic conduction disease.

2

Additional Options

Pacing if symptomatic bradycardia or complete AV block.