BACKGROUND: Infective endocarditis (IE) is a complex disease necessitating extensive clinical guidelines. The guidelines from the American Heart Association (AHA) and the European Society of Cardiology (ESC) have been markedly extended during the last 12 years. We examined the evidence base for these changes.

METHODS: IE guidelines published by AHA and ESC were reviewed. We categorized and combined guidelines into 3 time periods: (1) 2004 (AHA) and 2005 (ESC), (2) 2007 (AHA) and 2009 (ESC), and (3) 2015 (AHA) and 2015 (ESC). Number of recommendations, classes of recommendations (I, II, or III), and levels of evidence (LOE) (A, B, or C) were assessed and the changes over time.

RESULTS: From period 1 to period 3, we found a statistically significant increase in total number of IE recommendations from 37 to 253 (P<.01), a 6.8-fold increase. There were a significant decrease in LOE A (from 7 [20.0%] in period 1 to 4 [1.6%] in period 3, P<.0001, a 57% decrease), a nonsignificant decrease in LOE B recommendations (from 17 [48.6%] in period 1 to 115 [45.9%] in period 3, P=.29, a 6.8-fold increase), and a significant increase in LOE C recommendations (from 11 [31.4%] in period 1 to 134 [53.0%] in period 3, P=.02, a 12.2-fold increase).

CONCLUSIONS: The number of IE guideline recommendations has increased 6- to 7-fold during the last decade without a corresponding increase in evidence. These results highlight the strong need for more clinical studies to improve the level of evidence in IE guidelines.