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. 2011 Sep 16;108(37):623–634. doi: 10.3238/arztebl.2011.0623
A Data from several randomized studies or meta-analyses of adequate size
B Data from a randomized study or several large non-randomized studies
C Expert consensus opinion based on case reports or clinical experience

*1Following the guidelines of the American College of Cardiology, the American Heart Association, and the European Society of Cardiology