NUR 557 Module 3 Milestone One Example

Milestone One: Stasis, Clot and a Choice of Anticoagulant in a 78-Year-Old With Atrial Fibrillation

[Student Name]

Southern New Hampshire University

NUR 557: Advanced Pathophysiology and Pharmacology Across the Lifespan

Milestone One

[Instructor Name]

[Date]

The organization, setting and figures below are a composite written as a model document. No real employer, client, colleague or patient is described.

Milestone One: Stasis, Clot and a Choice of Anticoagulant in a 78-Year-Old With Atrial Fibrillation

Atrial fibrillation matters less for the irregular pulse it causes than for the strokes it makes possible. The disorganized atria stop contracting effectively, blood pools, and clots that form in the atria can travel to the brain. This milestone explains that chain in a composite 78-year-old man and joins it to the choice of anticoagulant. It argues that his stroke risk clearly justifies anticoagulation, that apixaban is the better anticoagulant for him than warfarin because of how the two drugs act on the clotting cascade and how they behave in older adults, and that his kidney function, not his age alone, determines the dose.

The Case

The patient is a 78-year-old retired machinist found to have an irregular pulse of 96 at a routine visit; an electrocardiogram confirms atrial fibrillation. He reports mild fatigue but no chest pain or shortness of breath. He has hypertension and type 2 diabetes but no history of stroke, heart failure or vascular disease. He weighs 72 kg, his serum creatinine is 1.3 mg/dL and he takes lisinopril, metformin and, on his own initiative, a daily low-dose aspirin. He fell once last winter on ice.

From Irregular Rhythm to Stroke

In atrial fibrillation, multiple disorganized electrical wavelets replace the coordinated firing of the sinus node, often triggered from the pulmonary veins and sustained by atrial stretch and fibrosis. The atria quiver rather than contract. Blood moves slowly, particularly in the left atrial appendage, a small pouch where flow is poorest. Of the three factors in Virchow's classic triad for clot formation, stasis is now clearly present, and the fibrillating atrial wall adds endothelial changes and a hypercoagulable local environment (Rosenthal & Burchum, 2021). A clot formed in the appendage can break free, travel to the brain and cause a stroke that is typically larger and more disabling than strokes from other causes.

The irregular, often rapid ventricular response explains his fatigue: filling time varies from beat to beat, and the atrial contribution to filling, significant in an older, stiffer heart, is lost.

How High Is His Stroke Risk?

Current guidance estimates stroke risk with the CHA2DS2-VASc score and recommends anticoagulation when the annual risk is high enough, generally a score of 2 or more in men (Joglar et al., 2024). He scores 2 for age 75 or older, 1 for hypertension and 1 for diabetes, a total of 4, which places him clearly in the group that benefits. Aspirin is not an adequate substitute for anticoagulation in atrial fibrillation, and taking it alongside an anticoagulant raises bleeding risk, so his self-started aspirin should stop once anticoagulation begins, since he has no other reason to take it.

Placing the Drugs on the Clotting Cascade

Warfarin and apixaban both prevent clots but act at different points. Warfarin blocks vitamin K epoxide reductase in the liver, so the liver cannot activate factors II, VII, IX and X; its effect builds over days and depends on diet, genetics and many interacting drugs, so it requires regular INR testing to keep the level between 2 and 3. Apixaban directly inhibits factor Xa, the enzyme where the intrinsic and extrinsic pathways converge; it works within hours, has fewer interactions and needs no routine level monitoring (Rosenthal & Burchum, 2021). Table 1 compares them for this patient.

Table 1

Warfarin and Apixaban Compared for This Patient

For patients with atrial fibrillation who have neither an artificial mechanical valve nor significant narrowing of the mitral valve, the guideline recommends direct oral anticoagulants over warfarin, reflecting trials that showed at least similar stroke prevention with less intracranial bleeding (Joglar et al., 2024). For a 78-year-old who has already fallen once, the lower risk of bleeding into the brain is especially relevant. A single fall does not by itself outweigh the benefit of anticoagulation, but it does call for a home safety review.

Controlling the Rate

Anticoagulation prevents strokes but does nothing for the rhythm. His ventricular rate of 96 at rest is only mildly fast, and his fatigue suggests that slowing it may help. A beta-blocker such as metoprolol succinate blocks beta-1 receptors in the heart, slowing conduction through the atrioventricular node so fewer of the chaotic atrial impulses reach the ventricles, which lengthens filling time (Rosenthal & Burchum, 2021). Guidance accepts a lenient resting target in many patients without symptoms, with tighter control when symptoms persist (Joglar et al., 2024). Age and diabetes shape this choice too. Older adults are more prone to slow heart rates and dizziness on beta-blockers, so a low starting dose is sensible, and beta-blockade can blunt the tremor and racing pulse that warn of low blood sugar, although with metformin alone his risk of hypoglycemia is low.

Kidneys, Age and Dose

Under its labeling, apixaban for atrial fibrillation is halved, from 5 mg to 2.5 mg twice a day, only if two of three features are present, namely an age of 80 or more, a body weight no higher than 60 kg and a serum creatinine at or above 1.5 mg/dL. He has none, so the standard 5 mg twice daily applies. Kidney function still matters for monitoring. Using the Cockcroft-Gault equation, which estimates creatinine clearance from age, weight and serum creatinine (Cockcroft & Gault, 1976), his clearance is about 48 mL/min: (140 minus 78) times 72, divided by 72 times 1.3. That reflects the age-related decline in filtration typical of older adults (Mangoni & Jackson, 2004) and calls for rechecking kidney function at least yearly, and sooner if he becomes ill, dehydrated or starts interacting drugs.

Conclusion

In this patient, disorganized atrial activity has created stasis in the left atrial appendage, and his age, hypertension and diabetes give him a CHA2DS2-VASc score of 4, well above the threshold for anticoagulation. Apixaban, acting directly on factor Xa, offers stroke prevention with less intracranial bleeding and simpler management than warfarin, and his kidney function supports the standard dose. His aspirin should stop, his home should be made safer and his kidneys should be checked regularly. Milestone Two will build on this plan.

References

Cockcroft, D. W., & Gault, M. H. (1976). Prediction of creatinine clearance from serum creatinine. Nephron, 16(1), 31-41. https://doi.org/10.1159/000180580

Joglar, J. A., Chung, M. K., Armbruster, A. L., Benjamin, E. J., Chyou, J. Y., Cronin, E. M., Deswal, A., Eckhardt, L. L., Goldberger, Z. D., Gopinathannair, R., Gorenek, B., Hess, P. L., Hlatky, M., Hogan, G., Ibeh, C., Indik, J. H., Kido, K., Kusumoto, F., Link, M. S., . . . Van Wagoner, D. R. (2024). 2023 ACC/AHA/ACCP/HRS guideline for the diagnosis and management of atrial fibrillation: A report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation, 149(1), e1-e156. https://doi.org/10.1161/CIR.0000000000001193

Mangoni, A. A., & Jackson, S. H. D. (2004). Age-related changes in pharmacokinetics and pharmacodynamics: Basic principles and practical applications. British Journal of Clinical Pharmacology, 57(1), 6-14. https://doi.org/10.1046/j.1365-2125.2003.02007.x

Rosenthal, L. D., & Burchum, J. R. (2021). Lehne's pharmacotherapeutics for advanced practice nurses and physician associates (2nd ed.). Elsevier.