The review addressed a clear question with well-defined inclusion criteria. Only two databases were searched so relevant data may have been missed. The search was restricted to English language articles, so language bias may have been introduced. There did not appear to have been any attempts to identify unpublished data. Publication bias was assessed and ruled out, but the small number of included studies made it difficult to fully rule out publication bias. There was insufficient information on the review process to rule out the possibility of reviewer error and bias.
Study quality was not assessed so it was unclear how reliable the findings were. Most included studies were of weaker methodological design. For some studies, the numbers of patients who received angiotensin-converting enzyme inhibitor, angiotensin 2 receptors blockers or beta blockers appeared to differ between groups; it was unclear whether these results were significant and may have confounded the results. Both randomised and non-randomised studies were combined in the meta-analysis, which may have affected the reliability of the results. The authors reported that statins significantly reduced the risk of ventricular tachycardia/ventricular fibrillation when the result was not significant. Statistical heterogeneity was assessed but the authors set significant levels for heterogeneity at p≤0.05 rather than p≤0.10, as was more common for tests of statistical heterogeneity, so significant heterogeneity may not have been detected.
Given the limited search, unclear quality of included studies and possible limitations in the analysis, the authors' caution is warranted.