Footnotes

• Twitter Follow Robyn A Clark at @clark_ra

• Contributors SCI: responsible for conception and design of this study and the previous versions of this review (Clark 2007a; Inglis 2010). Responsible for coordinating and completing the review. Responsible for all data included in the review including designing, undertaking searches, retrieving search results, screening studies for inclusion, assessing risk of bias of studies, extracting data from papers, contacting study authors for information, entering data into Review Manager 5, analysis and interpretation of data, drafting of the review or revising it critically for important intellectual content and final approval of the version to be published. Performed previous work that was the foundation of this study. RAC: responsible for conception and design of this study and the previous version of this review (Clark 2007a; Inglis 2010). Responsible for conceiving the initial idea for Clark 2007a. Responsible for all data included in the review including designing, undertaking searches, screening studies for inclusion, assessing risk of bias of studies, extracting data from papers, entering data into Review Manager 5, analysis and interpretation of data, drafting of the review or revising it critically for important intellectual content and final approval of the version to be published. Performed previous work that was the foundation of this study. RD: responsible for all data included in the review including undertaking handsearching of conference abstracts, retrieving search results, screening studies for inclusion, assessing risk of bias of studies, extracting data from papers, entering data into Review Manager 5, interpretation of data, drafting of the review or revising it critically for important intellectual content and final approval of the version to be published. DP-M: responsible for undertaking the heterogeneity tests between predefined subgroups and the meta-regression, review of statistical analyses undertaken in the review and drafting of sections of the review relevant to the heterogeneity analysis and meta-regression findings and approval of the version to be published. JGFC: consulted on design of review. Responsible for adjudicating study inclusion, interpretation of data (providing a methodological and clinical view), revising the review critically for important intellectual content and final approval of the version to be published. Guarantor for this review.

• Funding RAC is supported by a Heart Foundation Future Leader Fellowship (APP100847 2016-2019). SCI, Cardiovascular Life Sciences Fellow, New South Wales Cardiovascular Research Network, supported by the Heart Foundation of Australia and the NSW Office for Health and Medical Research (CR 11S 6226). JGFC, Senior Investigator, National Institute of Health Research (UK) for grant funding. This review was supported by funding from the NHS NIHR Cochrane Incentive Scheme, UK and the University of Technology Sydney, Australia. For details of funding support for previous published versions of this review, please refer to the Cochrane Review published in the Cochrane Database of Systematic Reviews.

• Competing interests None declared.

• Provenance and peer review Commissioned; internally peer reviewed.