Systematic reviews are rated as high-quality evidence, but they frequently do not result in strong recommendations for or against an intervention. This paper summarizes clinical results and methodological investigations from one randomized controlled trial, two systematic reviews, one meta-epidemiological study and detailed heterogeneity analyses. It was not possible to demonstrate the efficiency of a well-established medical intervention. Judgement of risk of bias in different reported trial characteristics was not associated with treatment effects within critical care medicine, but single-center trials estimated a larger mean treatment effect compared with multicenter trials. Characteristics of successful implementation strategies to improve guideline adherence of primary care physicians in the treatment of patients with cardiovascular diseases were described and potential clinical and methodological effect modifiers of these strategies were identified.