Two studies with sufficiently large numbers of outpatients and prospective data have stratified AF patients into those with inherently high vs. low risk of stroke. The value of anticoagulation in low risk patients may be relatively less. These patients should be followed to detect development of high-risk criteria.
Risk factors are hypertension, prior stroke or TIA, and poor left ventricular function.
The INR is simply the prothrombin time ratio adjusted for different thromboplastin sensitivities which vary between manufacturers. So the conversions shown on this slide are only very roughly true and cannot be counted on. INRs are the only reliable way to safely anticoagulate. Patient education about drug interactions, compliance with medication and monitoring, and early signs of bleeding are crucial to safe anticoagulation.