USMLE Prep - Medical Reference Library

Atrial Fibrillation — Rate vs Rhythm

System: Cardiology • Reviewed: Aug 31, 2025 • Step 1Step 2Step 3

Synopsis:

Stabilize if unstable; rate control first for most; rhythm control for persistent symptoms or HF; anticoagulate per CHA₂DS₂-VASc; DOACs preferred unless mechanical valve or moderate–severe mitral stenosis.

Key Points

  • Stabilize ABCs; begin targeted evaluation without delaying life-saving therapy.
  • Use system-specific risk tools to guide testing and disposition.
  • Order high-yield tests first; escalate imaging when indicated.
  • Start evidence-based initial therapy and reassess frequently.

Algorithm

  1. Primary survey and vitals; IV access and monitors.
  2. Focused history/physical; identify red flags and likely etiologies.
  3. Order system-appropriate labs and imaging (see Investigations).
  4. Initiate guideline-based empiric therapy (see Pharmacology).
  5. Reassess response; arrange consultation and definitive management.

Clinical Synopsis & Reasoning

AF evaluation focuses on hemodynamic stability, symptom burden, and secondary precipitants (thyrotoxicosis, infection, PE, alcohol). Classify as first‑detected, paroxysmal, persistent, or long‑standing, and determine stroke risk via CHA₂DS₂‑VASc. ECG confirms diagnosis and helps identify pre‑excitation or flutter; echocardiography informs structural disease and guides rhythm‑control choices.


Treatment Strategy & Disposition

For unstable patients, perform immediate synchronized cardioversion. In stable patients, choose rate vs rhythm control based on symptoms, duration, and substrate; employ β‑blockers or non‑DHP CCBs for rate control, and consider antiarrhythmics or ablation for rhythm strategies. Anticoagulate according to thromboembolic risk and timing around cardioversion. Disposition hinges on control of rate/rhythm and comorbidities; ensure follow‑up for anticoagulation and risk‑factor modification (BP, OSA, obesity).


Epidemiology / Risk Factors

  • Atherosclerotic risk (HTN, DM, HLD, smoking)
  • Age/family history of premature CAD

Investigations

TestRole / RationaleTypical FindingsNotes
EKGRhythm/ischemiaST-T changes/arrhythmiaSerial
TroponinMyocardial injuryDynamic rise/fallTrend
CXRPulmonary edema/sizeCardiomegaly/edema
BMP/Mg2+Electrolytes/renalDerangements
CBC/CoagsBleeding riskAbnormal/INR

CHA₂DS₂-VASc (Abbrev.)

FactorPoints
CHF/LV dysfunction1
HTN1
Age ≥752
DM1
Stroke/TIA/TE2
Vascular disease1
Age 65–741
Female sex1

Pharmacology

MedicationMechanismOnsetRole in TherapyLimitations
AmiodaroneMulti-channel blockadeHoursRhythm control in HFrEF/critically illQT prolongation, interactions
DiltiazemNon-DHP calcium-channel blockadeMinutesRate control (avoid in HFrEF)Hypotension; avoid HFrEF
Metoprololβ1 blockadeMinutesRate control without decompensated HFBradycardia/hypotension
Flecainide/PropafenoneNa-channel (class IC)HoursRhythm (pill-in-pocket) without structural heart diseaseProarrhythmia; avoid CAD/HFrEF
ApixabanFactor Xa inhibitionHoursAnticoagulation per CHA₂DS₂-VAScBleeding; renal dosing

Prognosis / Complications

  • Prognosis by ischemic burden/LV function
  • Arrhythmias and HF are complications

Patient Education / Counseling

  • Explain red flags and when to seek emergent care.
  • Reinforce medication adherence and follow-up plan.

Notes

Anticoagulate ≥3 weeks before and 4 weeks after elective cardioversion unless TEE-guided strategy is used. Choice of antiarrhythmic depends on structural heart disease.


References

  1. AHA/ACC/HRS AF Guideline — Link
  2. ESC AF Guideline — Link