Clinical Questions What is the ri...

Clinical Questions

What is the risk of pat in a patient with nonvalvular atrial fibrillation, and should that patient be given warfarin (Coumadin) or aspirin?

Evidence Summary

loched data from randomized trials display that warfarin reduces the risk of thump from 4.5 percent to 14 percent by year in patients with nonvalvular atrial fibrillation and no history of shock or tran-sient ischemic attack (TIA). Approximately single half of these strokes are moderate, rigid or fatal. (1) Warfarin increases the risk of major hemorrhage from 10 percent to 13 percent for year and increases the risk of intracranial hemorrhage from 01 per-cent to 03 percent through year. Therefore, at the Seventh parley on Antithrombotic and Thrombolytic Therapy, the American association of Chest Physicians (ACCP) make acceptableed warfarin for atrial fibrillation patients at high risk of blow aspirin for patients at soft risk of stroke, and either physic of patients with an intermediate risk. (1) The ACCP defines a low-risk patient as younger than 65 years with no predisposing risk factors (eg previous rap TIA, embolism, heart failure, hypertension, diabetes).

A clinical mastery regarding warfarin and aspirin treatment for knock patients was recently proposed by the agency of van Walraven and colleagues. While promising, it has not been prospectively validated in a of the present day population. (2) The ACCP sway and several other clinical decision conducts have been prospectively validated in modern populations of patients, which is the best way to evaluate a clinical decision conduct (see Tables 1 and 2 online at http://www.AAFP.org/AFP/20050615/poc.html for a summary of data). (3-5) Pearce and colleagues (3) used data from hardship Prevention in Atrial Fibrillation (SPAF) III, a randomized trial that evaluated three methods by studying the effects of aspirin versus the issues of warfarin. A 2001 studious mood by Gage and colleagues4 used data from a national registry of Medicare patients with atrial fibrillation who were discharged from the hospital on the other hand not given warfarin (only 31 percent were receiving aspirin). Because principally patients with atrial fibrillation who are not candidates for warfarin should be taking aspirin, the principally appropriate study population for evaluation of these clinical decision governments includes patients who have no history of rap and who are receiving aspirin. Therefore, the 2004 application of mind by Gage and colleagues (5) used data from the aspirin-only arms of five prospective clinical trials, including SPAF-III, (2) and involves in the greatest degree of the same patients studied by way of Pearce in 20003; therefore, recommendations in this Point-of-Care Guide are based onward data from Gage's 2004 validation reflection (5) and the ACCP guideline. (1) The overall risk of blow in both studies was 25 percent Approximately undivided third of patients in these studies were women the mean age was approximately 70 years, and all patients were receiving aspirin.

All five masterys evaluated in the study effectively identify low-risk patients (i.e., patients with 05 to 14 attacks per 100 patient-years). This risk is similar to that seen in studies of patients taking aspirin alone. However, the masterships vary considerably regarding the percent-age of patients falling into the low-risk clump The most useful rule would accurately classify the largest possible percentage of patients as depressed risk so that as many patients as possible can avoid the inconvenience, costliness and risk of oral anticoagulation with warfarin. The ACCP and Atrial Fibrillation Intervention (AFI) directions only classify 9 percent and 12 percent of patients as gentle risk, respectively. Combining the ACCP's low- and moderate-risk assign places tos yields a larger 23 percent of patients with an annual hardship risk of 0.85 percent. The Framingham command identified the largest percentage of patients at grave risk (49 percent) but they had a fairly high annual risk of affliction (1.4 percent). Between these greatests was the Stroke Prevention in Atrial Fibrillation (SPAF) control which classified 33 percent of patients as subdued risk (1.1 percent annual thump risk), and the CHAD[S.sub.2] lordship (named for the components of the score: congestive heart failure [past or present] hypertension [at least 160/90 mm Hg past or present] age [older than 75 years], diabetes, and rap or transient ischemic attack [past or present]) which classified 23 percent of patients as subdued risk (0.8 percent annual rap risk).

Figure 1 displays the ACCP and CHAD[S.sub.2] methods and their interpretations. Physicians may pick to use either rule or the pair in conjunction. By using more than common rule, the physician and patient may be more confident in a low- or high-risk assignment if the commands are consistent. When patients are at intermediate risk or when the risk assessment is inconsistent between the regularitys the physician may evaluate the patient's risk of bleeding while taking warfarin before making a decision. While there is no definitive command to determine the risk of bleeding in patients receiving anticoagulation therapy because of atrial fibrillation, single has been developed and validated in 222 patients receiving long-term anticoagulation for venous thromboembolism (mean follow-up 18 months) (6) In this contemplation there were five cases of major hemorrhages, all in patients classified as moderate or high risk of bleeding. Therefore, patients who have intermediate risk of thump and low risk of bleeding may be well adapted candidates for oral anticoagulation. For additional guidance upon initiating and adjusting oral anticoagulation with warfarin, please view two recent articles in this Point-of-Care Guides series. (78)