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Table 3 Level of Evidence [4]

From: Representation of cardiovascular magnetic resonance in the AHA / ACC guidelines

Level Definition
Level A • High quality evidence from more than 1 randomized controlled trial
• Meta-analyses of high-quality randomized controlled trials
• One or more randomized controlled trial corroborated by high-quality registry studies
Level B-R (randomized) • Moderate-quality evidence from 1 or more randomized controlled trial
• Meta-analyses of moderate-quality randomized controlled trials
Level B-NR (nonrandomized) • Moderate-quality evidence from 1 or more well-designed well-executed nonrandomized studies, observational studies, or registry studies
• Meta-analyses of such studies
Level C-LD (limited data) • Randomized or nonrandomized observational or registry studies with limitations of design or execution
• Meta-analyses of such studies
• Physiological or mechanistic studies in human subjects
Level C-EO (expert opinion) • Consensus of expert opinion based on clinical experience