LevelClass scale recommendations suggested by the American Heart Association/American Stroke Association
IRecommendation that the procedure or treatment is useful/effective. Sufficient evidence from randomized trials or meta-analyses
II-ARecommendation in favor of treatment or procedure being useful/effective. Some conflicting evidence from randomized trials or meta-analyses
II-BRecommendation’s usefulness/efficacy less well established. Greater conflicting evidence from randomized trials or meta-analyses
IIIRecommendation that the procedure or treatment is not useful/effective and may be harmful. Evidence from single randomized trial or non-randomized studies