Clinical Case: Mrs. R, a 66 year old female with newly diagnosed atrial fibrillation presents to your office for evaluation.  She has no history of TIA, but has a history of well controlled diabetes mellitus type II.  Her BP is 148/76 mmHg.  She has no history of heart disease.  Should this patient be placed on coumadin or aspirin for the prevention of thromboembolism related to her AF?

The annual stroke risk for patients older than 65 with non-rheumatic AF is at least fivefold greater than those patients of similar clinical characteristics. (2)  This translates into a 5-7% yearly risk for stroke.   A recent systematic review of the available medical literature found that the risk of stroke in a patient with AF was most significantly elevated by a prior history of stroke or a transient ischemic attack. (2)  Other major risk factors for stroke include advanced age (> 75 years of age), history of hypertension, or diabetes mellitus.  Interestingly enough, a history of heart failure or CAD were not conclusively linked with an increased risk of stroke. (2) 

Current ACC guidelines recommend warfarin adjusted to achieve an INR between 2 and 3 to prevent stroke among patients with AF and a history of prior cerebrovascular disease, prosthetic heart valves, or mitral stenosis. (3)  Warfarin therapy should also be considered for those patients age 75 years and older and those with hypertension, diabetes mellitus, heart failure or a documented left ventricular ejection fraction of less than 35%.  Other patients with AF may receive aspirin for protection against stroke. 

Pooled data from randomized trials show that warfarin reduces the risk of stroke from 4.5% to 1.4% per year in patients with non-rheumatic AF and no history of stroke or TIA.  The current generalized consensus among many medical practioners and treatment guidelines recommend warfarin for AF patients at high risk of stroke, aspirin for patients at low risk for stroke, and either drug for patients at intermediate risk.  It is this subset of patients that is the clinical conundrum for clinicians. There are a number of risk stratification schemes that help to predict stroke risk among patients with atrial fibrillation.  An ACCP model and CHADS2 (named for components of the score: CHF, HTN (160/90mm Hg, Age (older than 75), Diabetes, and Stroke or TIA has been proposed to help in decision making for treating patients with nonvalvular AF (see table 1) below. 



Singer DE, Albers GW, Dalen JE, Go AS, Halperin JL, Manning WJ. Antithrombotic therapy in atrial fibrillation: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy [Review]. Chest 2004; 126(3 suppl):429S-56S.

The risk of bleeding and intracranial hemorrhage is an obvious concern to patients and physicians. In pooled analysis (4) the annual risk of intracranial hemorrhage from controls to those patients on warfarin therapy rose from 0.1% to 0.3%. In “real world” terms this translates into an additional 2 intracranial bleeds for every 1000 patients treated with warfarin. Bleeding risks should be discussed in detail with patients. Major risk factors for bleeding include age > 65 years, history of GI tract bleeding, history of stroke, history of recent MI, hematocrit lower than 30 or a creatinine of 1.5 or greater. (6).
In our fictitious patient described above, in applying the ACCP risk criteria, the patient would be a candidate for warfarin given her 2 major risk factors of diabetes and hypertension. Using the CHADS2 criteria she would fall into the “moderate” risk for stroke with 2 points for hypertension and diabetes. The use of both “rules” in conjunction may be helpful in giving treating physicians and patients alike more confidence in the treatment decisions made.

There remains considerable controversy in the medical community and literature for treatment of “moderate” stroke risk patients with AF. For the present time being, a strategy of careful clinical assessment and risk stratification for atrial fibrillation in which the highest-risk groups for stroke and thromboembolism are targeted for anticoagulation (with warfarin) and low-risk groups being treated with aspirin appears to be most clinically appropriate.

REFERENCES
1. Feinberg WM, Blackshear JL, Laupacis, A, Kronmal R, Hart RG. Prevalence, age distribution, and gender of patients with atrial fibrillation. Analysis and implications. Arch Intern Med. 1995; 155:469-473.
2. Stroke Risk in Atrial Fibrillation Working Group. Independent predictors of stroke in patients with atrial fibrillation: a systematic review. Neurology. 2007; 69:546-554.
3. Writing Committee to Revise the 2001 Guidelines for the Management of Patients with Atrial Fibrillation. ACC/AHA/ESC 2006 guidelines for the management of patients with atrial fibrillation. Circulation. 2006; 114:e257-e354.
4. Singer DE, Albers GW, Dalen JE, Go AS, Halperin JL, Manning WJ. Antithrombotic therapy in atrial fibrillation: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy [Review]. Chest 2004;126(3 suppl):429S-56S
5. Pearce LA, Hart RG, Halperin JL. Assessment of three schemes for stratifying stroke risk in patients with nonvalvular atrial fibrillation. Am J Med 2000; 109:45-51.
6. Wells PS, Forgie MA, Simms M, Greene A, Touchie D, Lewis G, et al. The outpatient bleeding risk index: validation of a tool for predicting bleeding rates in patients treated for deep venous thrombosis and pulmonary embolism. Arch Intern Med 2003; 163:917-20.

Bio:
Joel R. Garcia, MD is a General and Invasive Cardiologist at The Orlando Heart Center, Sand Lake office. A native of Reading, Pennsylvania, he attended the Pennsylvania State University. He completed his residency in Internal Medicine at The Pennsylvania State University College of Medicine (LVH) program. He then completed his Cardiovascular Diseases Fellowship at The Pennsylvania State University College of Medicine, Milton S Hershey Medical College Program. He is board certified in Internal Medicine and Cardiology (BE). Dr Garcia is proficient in all aspects of invasive (non-interventional) cardiology, nuclear cardiology, echocardiography and coronary CT angiography. He is available to see new patients at the Orlando Heart Center, Sandlake office at 7236 Stonerock Circle, Orlando Fl 32819. Phone 407-370-5800.