New Atrial Fibrillation in an Older Adult with HFrEF and Stage 4 CKD

Estimate clearance with Cockcroft-Gault (the equation used for DOAC labeling), not the reported eGFR:

CrCl = [(140 - 78) x 58] / (72 x 1.6) = 3596 / 115.2 = about 31 mL/min

Choose apixaban 2.5 mg PO twice daily. Apixaban is reduced to 2.5 mg BID only when at least 2 of 3 criteria are met: age >= 80 years, weight <= 60 kg, SCr >= 1.5 mg/dL. She is 78 (does not meet the age criterion) but weighs 58 kg and has an SCr of 1.6 mg/dL, so she meets exactly 2 criteria and the reduced dose applies. Meeting only the SCr criterion would not justify 2.5 mg BID.

Why treat at all: CHA2DS2-VASc 5 is a high stroke risk; a HAS-BLED of 3 flags modifiable bleeding risks (blood pressure control, avoiding NSAIDs/antiplatelets) but is not a reason to withhold anticoagulation.

Alternatives rejected:

• Dabigatran: labeled dosing requires CrCl > 30 mL/min for 150 mg BID, she is borderline at ~31 mL/min and renal function may drift; also higher dyspepsia/GI bleeding risk.
• Warfarin: acceptable but requires INR monitoring and consistency; apixaban has lower intracranial hemorrhage and fewer drug/food interactions, and she has no mechanical valve or moderate-severe mitral stenosis.
• Rivaroxaban 15 mg daily with the evening meal (for CrCl 15-50) and edoxaban 30 mg daily (CrCl 15-50) are both reasonable second choices if apixaban is unaffordable or unavailable.
• No anticoagulation / aspirin only: aspirin is inadequate for AF stroke prevention.

Act on the potassium of 5.4 mEq/L with an eGFR of ~28 mL/min:

1. Hold spironolactone. Mineralocorticoid receptor antagonists are not recommended when eGFR is below 30 mL/min and potassium exceeds 5.0 mEq/L; the hyperkalemia risk outweighs benefit in this setting.
2. Hold the potassium chloride 20 mEq. With a potassium of 5.4 and a failing kidney, continued supplementation is unnecessary and unsafe.
3. Do not reflexively stop lisinopril. ACE inhibition carries a mortality benefit in HFrEF. If potassium remains above 5.5 mEq/L after holding the MR antagonist and supplement, reduce lisinopril to 10 mg daily or add a potassium binder (patiromer or sodium zirconium cyclosilicate) rather than abandoning RAS inhibition.
4. Recheck a basic metabolic panel in 2-3 days, before any of these changes are considered final.
5. Carvedilol and furosemide stay unchanged today; reassess volume status before adjusting the diuretic, and note that non-dihydropyridine calcium channel blockers (e.g., diltiazem) should be avoided for rate control in HFrEF.
6. Reinforce avoidance of NSAIDs - the combination of ACE inhibitor, diuretic, and NSAID plus an anticoagulant is a high-risk stack for acute kidney injury and bleeding.

• Potassium and SCr in 2-3 days after holding spironolactone and KCl; if stable, repeat weekly for 2 weeks, then at 3 months and with any acute illness or new medication.
• Renal function for apixaban every 6 months while CrCl is 30-60 mL/min (more often if CrCl falls below 30, with dehydration, or after any acute illness); reassess dose criteria at each check.
• Hemoglobin/hematocrit at baseline (11.8 g/dL) and periodically, plus explicit teaching on melena, hematuria, epistaxis, and unusual bruising.
• Drug interaction screen at every fill: avoid strong dual CYP3A4/P-gp inhibitors (ketoconazole, itraconazole, clarithromycin) and inducers (rifampin, carbamazepine, St. John's wort).
• Rate and symptom control: home pulse checks, and cardiology follow-up for rate control and echocardiogram.
• Patient teaching with teach-back: do not stop apixaban abruptly; for a missed dose take it the same day and do not double up; disclose apixaban before any dental or surgical procedure; avoid NSAIDs and potassium-containing salt substitutes.