What is the approach to anticoagulation in patients with Non-ST-Elevation Myocardial Infarction (NSTEMI) and Pulmonary Embolism (PE), considering factors such as Impaired renal function?

Anticoagulation in NSTEMI and PE

NSTEMI Anticoagulation Strategy

All NSTEMI patients require immediate parenteral anticoagulation in addition to dual antiplatelet therapy (aspirin plus P2Y12 inhibitor), with choice of anticoagulant guided by management strategy and bleeding risk. 1, 2, 3

Initial Anticoagulation Options for NSTEMI

For invasive strategy (planned catheterization):

• Enoxaparin 1 mg/kg subcutaneously every 12 hours is preferred over unfractionated heparin (UFH) unless CABG is planned within 24 hours 2
• UFH with weight-based dosing (60 IU/kg bolus, maximum 4000 IU, followed by 12 IU/kg/hour infusion, maximum 1000 IU/hour) adjusted to therapeutic aPTT 3
• Bivalirudin 0.75 mg/kg IV bolus followed by 1.75 mg/kg/hour infusion 2
• Fondaparinux 2.5 mg subcutaneously once daily, but must be supplemented with UFH or bivalirudin during PCI due to insufficient anti-IIa activity and risk of catheter thrombosis 2, 3

For conservative strategy (medical management):

• Enoxaparin, fondaparinux, or UFH are all reasonable options 4
• Fondaparinux is preferred in patients with increased bleeding risk 4

Duration of Anticoagulation in NSTEMI

• Minimum 48 hours for medical management 1
• Up to 8 days for extended medical therapy 1
• Until PCI is performed for invasive strategy 1
• For patients requiring long-term anticoagulation (e.g., atrial fibrillation), transition to triple therapy (DOAC + aspirin + clopidogrel) for up to 1 month, then DOAC + clopidogrel for up to 1 year, then DOAC monotherapy 5

Critical Pitfalls in NSTEMI Anticoagulation

• Never use fibrinolytic therapy in NSTEMI—it causes harm without benefit (Class III: Harm recommendation) 3
• Never use fondaparinux alone during PCI—always add UFH or bivalirudin to prevent catheter thrombosis 2, 3
• Avoid switching between anticoagulants (e.g., enoxaparin to UFH or vice versa) when proceeding to PCI, as this increases bleeding risk 1
• Never abruptly discontinue UFH—causes rebound thrombotic events; transition to LMWH or fondaparinux for extended therapy 1

Renal Impairment Considerations in NSTEMI

• For creatinine clearance <30 mL/min: Reduce enoxaparin to 1 mg/kg once daily 3
• Bivalirudin or UFH are preferred in renal insufficiency 4
• Calculate creatinine clearance using Cockcroft-Gault formula to guide dosing 1
• Fondaparinux requires dose adjustment or avoidance in severe renal dysfunction 1

Pulmonary Embolism Anticoagulation Strategy

Immediate anticoagulation is mandatory for all suspected PE patients while awaiting diagnostic confirmation, given the high mortality in untreated patients. 4

Initial Anticoagulation Options for PE

Parenteral anticoagulation options:

• Intravenous UFH: 80 U/kg bolus followed by 18 U/kg/hour infusion, adjusted using aPTT-based nomogram to maintain aPTT 1.5-2.3 times control 4
• Subcutaneous LMWH (enoxaparin preferred) 4
• Subcutaneous fondaparinux 4

Duration and Transition in PE

• Parenteral anticoagulation followed by oral vitamin K antagonists (VKAs) is the standard approach 4
• Initial course of heparin in addition to VKAs is required—starting VKAs alone results in three-fold higher rate of recurrent VTE 4
• For intermediate-risk (submassive) or high-risk (massive) PE, more aggressive therapy beyond anticoagulation alone should be considered 6

Special Considerations for High-Risk PE

• High-risk PE patients with contraindications to thrombolysis or inadequate response may require surgical pulmonary embolectomy or catheter-directed interventions 4
• Catheter embolectomy or fragmentation may be considered as alternative to surgery when thrombolysis is contraindicated or has failed 4
• Anticoagulation remains the cornerstone even in high-risk patients, with additional interventions layered on top 6

Critical Pitfalls in PE Anticoagulation

• Never delay anticoagulation while awaiting diagnostic confirmation in patients with suspected PE—start immediately given high mortality risk 4
• Always use weight-adjusted UFH dosing (80 U/kg bolus, 18 U/kg/hour infusion) rather than fixed doses, with subsequent aPTT-guided adjustments 4
• Never start VKAs without concurrent heparin—this increases recurrent VTE risk three-fold 4

Key Differences Between NSTEMI and PE Anticoagulation

• NSTEMI requires dual antiplatelet therapy plus anticoagulation, whereas PE requires anticoagulation alone (no antiplatelet agents) 1, 2, 3, 4
• NSTEMI anticoagulation duration is shorter (48 hours to 8 days or until PCI), while PE requires transition to long-term oral anticoagulation with VKAs 1, 4
• Fondaparinux can be used as monotherapy in PE, but in NSTEMI undergoing PCI it requires supplementation with UFH or bivalirudin 4, 2, 3
• NSTEMI management is driven by invasive vs. conservative strategy, while PE management is driven by risk stratification (low, intermediate, high-risk) 1, 2, 6