A 72-year-old woman with a 3-year history of paroxysmal atrial fibrillation and a prior ischemic stroke (2 years ago) presents for routine follow-up. She is currently on metoprolol 50 mg BD for rate control and aspirin 75 mg daily. Her CHA₂DS₂-VASc score is 5 (age 72, hypertension, prior stroke). ECG confirms sinus rhythm. She reports occasional palpitations but denies dyspnea or chest pain. What is the most appropriate anticoagulation strategy?

Explanation

## Risk Stratification & Anticoagulation in Paroxysmal AF ### CHA₂DS₂-VASc Score Interpretation | Score | Risk Category | Annual Stroke Risk | Anticoagulation | |-------|---------------|-------------------|-----------------| | 0 (male) / 1 (female) | Low | < 1% | No anticoagulation | | 1 (male) / 2 (female) | Low–Intermediate | 1–2% | Consider anticoagulation | | ≥ 2 (male) / ≥ 3 (female) | High | ≥ 2% | **Anticoagulation mandatory** | **Key Point:** This patient's CHA₂DS₂-VASc score is **5**, placing her in the **high-risk category** for stroke. The **paroxysmal nature of AF does NOT reduce stroke risk**—paroxysmal AF carries the same thromboembolic risk as persistent/permanent AF. Prior ischemic stroke is a major risk factor (score +2). ### Anticoagulation Recommendation **High-Yield:** All patients with AF and CHA₂DS₂-VASc ≥ 2 (males) or ≥ 3 (females) **require anticoagulation with either a DOAC or warfarin**, regardless of AF pattern (paroxysmal, persistent, or permanent). **Clinical Pearl:** DOACs are **NOT contraindicated after prior stroke**. In fact, DOACs are preferred over warfarin in most patients because they offer: - Predictable pharmacokinetics (no INR monitoring) - Lower risk of intracranial hemorrhage (vs. warfarin) - Better efficacy in secondary stroke prevention - Greater convenience and adherence ## Why Apixaban 5 mg BD? ```mermaid flowchart TD A[AF with CHA₂DS₂-VASc ≥ 2]:::outcome --> B{Anticoagulation needed?}:::decision B -->|Yes| C{Contraindication to DOAC?}:::decision C -->|No| D[DOAC preferred: apixaban, dabigatran, edoxaban, rivaroxaban]:::action C -->|Yes: severe renal failure, mechanical valve| E[Warfarin]:::action D --> F[Apixaban 5 mg BD: best safety profile]:::outcome E --> G[Target INR 2–3]:::outcome ``` **Apixaban advantages:** - Twice-daily dosing improves adherence - Lowest risk of major bleeding among DOACs - No dose adjustment needed for age alone (unlike dabigatran) - Effective in secondary stroke prevention ## Why NOT the Other Options? **Option A (Aspirin monotherapy):** - Aspirin is **ineffective** for stroke prevention in AF (NNT >> 100) - Guidelines recommend against aspirin monotherapy in AF with CHA₂DS₂-VASc ≥ 2 - Prior stroke mandates anticoagulation, not antiplatelet therapy **Option C (Warfarin only):** - Warfarin is **not contraindicated** after stroke, but DOACs are **preferred** due to: - Lower intracranial hemorrhage risk - No need for INR monitoring - Better adherence - Warfarin is reserved for patients with mechanical valves or severe renal impairment **Option D (Dual antiplatelet therapy):** - Aspirin + clopidogrel is **inferior** to anticoagulation for AF stroke prevention - Dual antiplatelet therapy is used in acute coronary syndrome, not AF - Increases bleeding risk without adequate stroke protection **Warning:** ~~Paroxysmal AF does not require anticoagulation~~ — **FALSE**. Paroxysmal AF carries the same stroke risk as persistent AF and requires anticoagulation if CHA₂DS₂-VASc ≥ 2. [cite:Harrison 21e Ch 226]