Figure 1. Proportion of Recommendations Classified as Level of Evidence A Overall and by Class of Recommendation in the ACC/AHA and ESC Guidelines.

Although a greater proportion of class I (“should do”) and class III (“should not do”) recommendations are supported by level of evidence (LOE) A evidence and some subspecialties have a greater proportion of LOE A recommendations than others, less than 15% of guideline recommendations in all subspecialties are supported by LOE A evidence. Missing bars represent subspecialty area/class combinations for which 0% of recommendations are classified as LOE A. ACC/AHA indicates American College of Cardiology/American Heart Association; ESC, European Society of Cardiology.