| Level I | Good quality evidence |
Systematic review of RCTs with consistent findings High quality individual RCT |
| Level II |
Limited quality patient orientated evidence |
Systematic review of lower quality studies or studies with inconsistent findings Low quality clinical trial Cohort studies Case-control studies |
| Level III | Other |
Consensus guidelines, extrapolations from bench research, usual practice, opinion, disease-oriented evidence (intermediate or physiologic outcomes only), or case series |
[50] ACE-inhibtors (first-line option for CCF): Tai C, Gan T, Zou L, Sun Y, Zhang Y, Chen W, Li J, Zhang J, Xu Y, Lu H, Xu D. Effect of angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers on cardiovascular events in patients with heart failure: a meta-analysis of randomized controlled trials. BMC Cardiovasc Disord. 2017 Oct 5;17(1):257. https://www.ncbi.nlm.nih.gov/pubmed/28982370