Falls, Aspirin and a Very High Stroke Risk
An 82-year-old woman with permanent atrial fibrillation attends for review. She lives alone with carers twice daily, has hypertension, type 2 diabetes and mild cognitive impairment, and had a transient ischaemic attack two years ago. She has fallen three times in the last six months, once sustaining a wrist fracture; the falls are attributed to trips and postural symptoms, and her gait is slow but she walks with a stick indoors. She takes aspirin 75 mg, amlodipine 10 mg, metformin 500 mg twice daily and atorvastatin 20 mg. BP 152/88, pulse 78 irregular. Weight 48 kg, creatinine 104 µmol/L, reported eGFR 44 mL/min/1.73 m², haemoglobin 108 g/L, platelets 210 ×10⁹/L, no active bleeding. She is reluctant to take 'blood thinners' because her sister had a fatal intracranial haemorrhage.
1. Quantify her stroke and bleeding risk and explain how you weigh the two in her case.
Read the worked answer
Stroke risk. CHA2DS2-VASc: congestive failure 0, hypertension 1, age ≥75 2, diabetes 1, prior stroke/TIA 2, vascular disease 0, female sex 1 = 7. That corresponds to an untreated ischaemic stroke rate of roughly 7–10% per year - one of the highest-risk groups encountered in practice. Female sex is best regarded as an age-dependent risk modifier, but the decision is already clear because she has multiple independent risk factors.
Bleeding risk. HAS-BLED: hypertension not >160 (0–1), abnormal renal function 1, prior stroke 1, bleeding history 0, labile INR 0, age >65 1, antiplatelet drug 1 = 4–5, i.e. high. A high HAS-BLED score is explicitly a prompt to identify and correct modifiable factors and to review more closely - it is not a reason to withhold anticoagulation.
How to weigh them. The risks are not symmetric. Anticoagulation reduces stroke by about two-thirds, and AF-related strokes are more often fatal or severely disabling than bleeds, most of which are extracranial and manageable. Her three falls a year do not shift the balance: modelling suggests a patient would need to fall in the order of 300 times a year for subdural haematoma risk to offset the stroke reduction, and DOACs cause substantially less intracranial haemorrhage than warfarin. Aspirin, by contrast, offers minimal stroke prophylaxis in AF while carrying a comparable bleeding risk - it should stop.
Modifiable factors to act on now. Blood pressure (target <140 systolic but without provoking postural hypotension and more falls), the anaemia (haemoglobin 108 - iron studies, B12/folate, faecal immunochemical testing, and GI investigation if iron deficient), a review of amlodipine 10 mg, vision, footwear, home hazards, vitamin D and a falls physiotherapy programme. Her sister's death is a real concern to explore rather than dismiss, and the discussion with her and her carers should be documented as a shared decision.
2. Which anticoagulant and what dose would you prescribe? Show your calculations and explain why the reported eGFR is not sufficient.
Read the worked answer
Renal function - calculate it properly.
- Cockcroft–Gault: CrCl = (140 − 82) × 48 ÷ (0.818 × 104) × 0.85 = 2784 ÷ 85.1 × 0.85 ≈ 28 mL/min.
- The reported eGFR of 44 is an MDRD/CKD-EPI value normalised to 1.73 m²; it does not use her actual weight. DOAC dosing is based on Cockcroft–Gault CrCl, and in a small elderly woman the two figures differ by a third. Use the CrCl.
Choice of agent. A DOAC is preferred to warfarin: predictable pharmacokinetics, no INR monitoring (important with cognitive impairment and carer-supported administration), fewer drug and diet interactions, and lower intracranial haemorrhage. At a CrCl of 28 mL/min, apixaban is the best-supported choice - it is licensed down to CrCl 15 mL/min and has the least renal clearance of the DOACs.
Dose. Apixaban 2.5 mg twice daily is indicated when two of three criteria are met: age ≥80 years, weight ≤60 kg, serum creatinine ≥133 µmol/L. She meets age (82) and weight (48 kg) - two criteria - so the reduced dose is label-concordant: apixaban 2.5 mg twice daily. This is independent of renal function; she would otherwise receive 5 mg twice daily. Document the reasoning, because inappropriate under-dosing of DOACs is common and is associated with more strokes, and the next clinician must see that 2.5 mg was deliberate.
Alternatives worth knowing. Edoxaban 30 mg daily or rivaroxaban 15 mg daily for CrCl 15–50 mL/min; dabigatran should be avoided at CrCl <30. Warfarin (target INR 2–3) remains reasonable if adherence is in real doubt or if CrCl falls below 15.
What not to do: leave her on aspirin as a compromise; start a DOAC without checking weight and CrCl; withhold anticoagulation solely because she falls.
3. Set out your plan for modifying bleeding risk, arranging follow-up, and explaining the decision to her.
Read the worked answer
Correct the modifiable risks.
- Stop aspirin. There is no indication in AF and it adds bleeding without useful stroke protection. Confirm there is no recent coronary stent first.
- Investigate the anaemia (haemoglobin 108). Iron studies, B12/folate, coeliac serology, faecal immunochemical test, and upper and lower GI investigation if she is iron deficient - an occult gastrointestinal lesion is a more important threat than her falls.
- Blood pressure 152/88. Recheck lying and standing; amlodipine 10 mg may be contributing to postural symptoms. Treat towards <140/90 while avoiding orthostatic drops - consider lowering amlodipine and using a low-dose thiazide-like diuretic or an ACE inhibitor/ARB if a postural drop is confirmed.
- Falls. Multifactorial assessment: vision, footwear, home hazards, gait and balance training, vitamin D, review of sedating medication, and carer awareness. Falls are not a reason to stop anticoagulation, but reducing them is worthwhile in its own right.
- Avoid NSAIDs and additional antiplatelets; recommend paracetamol.
- Adherence. A dosette box or carer-supervised administration; the twice-daily apixaban regimen fits her carer visits.
Follow-up. Review at 4–6 weeks, then annually, with full blood count, creatinine and recalculated CrCl, blood pressure, falls history, adherence and any bleeding. Any illness with vomiting or diarrhoea, or any fall involving head injury, needs urgent assessment - CT head if there has been head trauma while anticoagulated.
Explain to her. Her stroke risk is very high, and AF-related strokes are often devastating. Apixaban causes far less bleeding in the brain than the older tablets her sister almost certainly took, and the small residual risk is outweighed many times over by the stroke protection. The two things that will most reduce her risk are taking the tablet every day and having her blood pressure and falls addressed. Record that the conversation included her carers and that she agreed to proceed.