Pathophysiology
Clinical meaning
The clinician prescribes anticoagulation for atrial fibrillation using the CHA2DS2-VASc score for stroke risk stratification: Congestive heart failure (1 point), Hypertension (1), Age 75 or older (2), Diabetes (1), Stroke/TIA/thromboembolism history (2), Vascular disease (1), Age 65-74 (1), Sex category female (1). Score interpretation: 0 in males or 1 in females = low risk, anticoagulation not recommended; 1 in males = consider anticoagulation; 2 or greater = anticoagulation recommended. The clinician assesses bleeding risk using the HAS-BLED score (Hypertension, Abnormal renal/liver function, Stroke, Bleeding history, Labile INR, Elderly, Drugs/alcohol) -- a high bleeding risk score is NOT a contraindication to anticoagulation but identifies modifiable risk factors to address. DOACs (direct oral anticoagulants) are preferred over warfarin per current guidelines: apixaban (ARISTOTLE trial -- superior efficacy and lower bleeding), rivaroxaban (ROCKET-AF), dabigatran (RE-LY -- 150 mg dose superior for stroke prevention, 110 mg dose lower bleeding), edoxaban (ENGAGE AF-TIMI 48). The clinician selects based on patient factors: renal function (dabigatran is 80% renally cleared -- avoid if CrCl less than 30 mL/min; apixaban has the least renal dependence and can be...