Figure 10 highlights one of the current scoring systems for assessing the major risk of anticoagulation therapy, bleeding.  The HAS-BLED score[7] is an algorithm that was not designed to enable the physician to tell a patient, "Your bleeding risk is so high that we cannot possibly put you on one of these agents." As reviewed by Bhatt (Bhatt, Figure 13), the risk factors calculated by the algorithm include hypertension, abnormal liver or renal function, prior stroke, a bleeding history, a labile INR, age >65 years, or prescription of a concomitant drug that greatly increases the risk of bleeding (such as aspirin or NSAIDs).  What is immediately apparent, of course, is the degree of overlap of these risk factors with the risk factors for ischemic stroke.  To briefly highlight a couple of these factors:

Hypertension:  One clear point about hypertension is that a patient with poorly-controlled blood pressure, defined as systolic blood pressure >160 mm Hg, should not be on an anticoagulant.  This is because in addition to hypertension’s being a potent risk factor for ischemic stroke, being on an anticoagulant will greatly increase the risk of intracerebral hemorrhage, stressing the importance of blood pressure control. 

Abnormal renal function:  A new risk score [ATRIA, based on the Anticoagulation and Risk Factors in Atrial Fibrillation Study (ATRIA)] has just been published that says abnormal kidney function is also a risk factor for ischemic stroke.[8]

Finally, having had a prior stroke is the most potent risk factor for having another stroke.