Anticoagulation in the Elderly

Abhay J. Dhond, MD, MPH, Hector I. Michelena, MD, Michael D. Ezekowitz, MD, PhD


Am J Geriatr Cardiol. 2003;12(4) 

In This Article

Anticoagulation Guidelines

Prophylaxis against stroke is a priority. The risk for stroke in the first 48 hours after known new onset of AF, although debated, seems low. Patients may be started on warfarin without using heparin unless cardioversion is to be performed, in which case, the patient must be anticoagulated with heparin and the use of transesophageal echocardiography may be considered to evaluate for the presence of left atrial appendage thrombi. The dose of heparin must achieve an activated partial thromboplastin time goal between 60-80 of the control. If cardioversion is to be performed at a later time, patients must receive oral anticoagulation for at least 3 weeks before cardioversion. Oral anticoagulation must be continued for at least 4 weeks after sinus rhythm is restored and indefinitely in chronic AF.[29]

Given the low rate of sinus rhythm maintenance, chronic oral anticoagulation in AF is a critical element of treatment. The use of multiple drugs in the elderly calls for awareness of current or new agents that may interact with warfarin and increase or decrease anticoagulation intensity. The treatment should always be individualized. The patient must be disciplined, compliant, and must participate actively in the decision-making process regarding the anticoagulation. Education of the patient on drug-to-drug interactions and on the importance of maintaining regular diet habits is critical. A tight control of both systolic and diastolic blood pressure is essential.[46]

The recommended target INR is 2.5 with a range of 2.0-3.0.[29]

The SPAF III study[14] used fixed doses of warfarin in the warfarin/aspirin arm—not INR adjusted —and failed to show benefit because the average INRs were below the therapeutic range. The SPINAF study,[16] on the other hand, using a rigorous monitoring regimen, demonstrated a 79% reduction in stroke rate in the warfarin randomized patient without an increase in bleeding complications. Patients were initiated on 4.0 mg of warfarin per day with a goal of maintaining the prothrombin time ratio (PTR) within 1.2-1.5 (INR, 1.4-2.8). Monitoring was performed weekly during a 12-week induction period and monthly thereafter during a maintenance period for a total follow-up of 36 months. Patients whose PTR was >1.5 had their warfarin reduced by 1 mg/day, while patients whose PTR was <1.5 had their dosage increased by 1 mg/day if the low PTR persisted for two consecutive visits. In the SPINAF study,[6] 260 patients were randomized to warfarin. During the induction period, the proportion of patients with PTRs in the desired range increased from 30.2% at 1 week to 67.6% at 12 weeks. The proportion of patients requiring a dose adjustment decreased from 56% during the early part of the induction period to 18% at the end. The (mean±1 SD) dose increase was 0.45±0.27 mg; the decrease was 0.58±0.51 mg.

The observations above are the basis for the current practical recommendations suggested by the authors.

Anticoagulation is recommended for all patients with AF who have 'high-risk' factors for thromboembolism (in the absence of obvious contraindication to anticoagulation). The 'high-risk' factors include hypertension, diabetes, heart failure, and history of TIA or stroke. Patients with AF under the age of 65 with no 'high-risk' factors are recommended aspirin therapy alone. Between the age of 65 and 75, in the absence of 'high-risk' factors, either aspirin therapy or anticoagulation may be considered (the decision should be individualized by the physician in consultation with the patient). However, over the age of 75, anticoagulation should be considered for all patients with AF even when the 'high-risk' factors for thromboembolism are absent. In patients with contraindication to anticoagulation, daily aspirin therapy is recommended. Although the optimal dose of aspirin has not been established, 325 mg/day seems the best compromise and is our recommendation. Patients with paroxysmal AF have thromboembolism rates similar to patients with chronic AF and thus anticoagulation guidelines in these patients are identical as above.

In the elderly it is simple and safe to initiate anticoagulation with low-dose warfarin in the outpatient setting using a dose estimated to be that required for maintenance; 3 mg/day is recommended for patients older than 70 years, 4 mg/day for patients under 70. Monitoring is essential to ensure the proper level of anticoagulation and to prevent variations in intensity of anticoagulation. After initiation of warfarin therapy INR should be monitored at least weekly until the target of 2.5 (range, 2.0-3.0) is reached. Then regular follow-up by INR monitoring at least every 4 weeks is recommended. Considerable dose adjustment is required to keep patients within range, particularly during the initiation phase. Close monitoring and dose adjustment may also be required when adding new medications. Close attention to the patient's diet habits is critical. Dose adjustments of a 1-mg increment or decrement at a time are advised. Fixed-dosage regimens are unlikely to result in patients remaining within the desired therapeutic range.[4] Reliable monitoring, in selected patients, may be achievable using INR measuring devices designed for home use.[47,48]