A 58-year-old woman with mechanical mitral valve replacement (on warfarin, INR 2.5) presents with acute coronary syndrome (NSTEMI). Troponin is elevated. Coronary angiography is planned within 6 hours. She has no contraindications to dual antiplatelet therapy. What is the most appropriate immediate next step?

Explanation

## Clinical Scenario A 58-year-old woman with a mechanical mitral valve replacement (on warfarin, INR 2.5) presents with NSTEMI. Coronary angiography is planned within 6 hours. The key challenge is balancing anticoagulation for the mechanical valve against the need for dual antiplatelet therapy (DAPT) in ACS. ## Management Principle: Warfarin + DAPT in Mechanical Valve + ACS **Key Point:** In patients with a mechanical heart valve presenting with ACS, warfarin must **NOT** be stopped. Mechanical valves carry a high risk of acute thrombosis if anticoagulation is interrupted — a potentially fatal complication. The accepted strategy is to **continue warfarin** and add DAPT (aspirin + clopidogrel), accepting the increased bleeding risk of triple therapy as the lesser of two evils. **High-Yield (ESC 2021 / ACC/AHA Guidelines):** For mechanical valve patients with ACS undergoing early invasive strategy, warfarin is continued (not bridged with heparin, which adds further bleeding risk without valve benefit), and DAPT is initiated immediately. Radial access is preferred to reduce access-site bleeding. The INR may be targeted at the lower end of the therapeutic range (2.0–2.5) during the DAPT period to mitigate bleeding risk. ## Rationale for Correct Answer (Option C) 1. **Continue warfarin:** Stopping warfarin risks acute mechanical valve thrombosis — mortality from prosthetic valve thrombosis can reach 5–15% even with emergency surgery (Horstkotte et al., *Eur Heart J* 1995; ESC Valvular Heart Disease Guidelines 2021). 2. **Aspirin 300 mg loading:** Standard ACS loading dose; reduces platelet aggregation via COX-1 inhibition. 3. **Clopidogrel 600 mg loading:** P2Y12 inhibitor loading is essential in NSTEMI to reduce recurrent ischaemic events; deferring it until after angiography is suboptimal when angiography is imminent (within 6 hours). 4. **Proceed with angiography:** Radial access is preferred in patients on anticoagulation to minimise access-site bleeding. ## Comparison Table: Anticoagulation Strategies in Mechanical Valve + ACS | Strategy | Valve Thrombosis Risk | Bleeding Risk | Recommendation | |----------|----------------------|---------------|----------------| | **Continue warfarin + DAPT (Triple therapy)** | Low | Moderate–High | ✓ **Standard of care** | | **Stop warfarin + DAPT only** | **HIGH** | Lower | ✗ Contraindicated in mechanical valve | | **Warfarin + aspirin only** | Low | Low–Moderate | ✗ Inadequate for ACS | | **Warfarin + aspirin, defer clopidogrel** | Low | Moderate | ✗ Suboptimal ACS management | ## Why NOT the Other Options **Option A (Stop warfarin; add aspirin + clopidogrel):** - Stopping warfarin in a mechanical valve patient is dangerous. Acute prosthetic valve thrombosis is catastrophic and carries high surgical mortality. - The verifier's suggestion of heparin bridging is not standard for this scenario; bridging adds bleeding risk and is not recommended when warfarin can be safely continued through the procedure (radial access). **Option B (Continue warfarin; aspirin only; defer clopidogrel):** - Deferring clopidogrel loading reduces acute ischaemic benefit in NSTEMI. - When angiography is planned within 6 hours, pre-loading with clopidogrel 600 mg is appropriate per ACC/AHA NSTEMI guidelines (Amsterdam et al., *JACC* 2014). **Option D (Stop warfarin; aspirin only; clopidogrel after stent):** - Combines two errors: stopping warfarin (valve thrombosis risk) and delaying clopidogrel (inadequate ACS management). **Clinical Pearl:** Triple therapy (warfarin + aspirin + clopidogrel) carries a major bleeding risk of approximately 2–4% per month (WOEST trial, *Lancet* 2013; RE-DUAL PCI, *NEJM* 2017). This is accepted in mechanical valve + ACS because the alternative — stopping warfarin — risks catastrophic valve thrombosis. Duration of triple therapy should be minimised (typically 1–4 weeks), transitioning to dual therapy (warfarin + single antiplatelet) thereafter. **Mnemonic:** **WAVE** = **W**arfarin continue, **A**spirin load, **V**alve protection, **E**arly DAPT. In mechanical valve + ACS, you do NOT stop warfarin.