A study of the relationship between unit and surgeon volume and the outcomes of cardiac surgery in Australia Ch'ngStephanie 2017 In recent decades, increased emphasis on patient safety in cardiac surgery has provoked scrutiny of the research findings that suggest an association between hospital and/or surgeon volume and patient mortality for various inpatient procedures. Volume is an easy to measure variable, more so than other aspects or processes of care, and the potential relationship between cardiac surgical volume and mortality is widely documented. However, volume itself, especially hospital/unit volume, may not be a meaningful proxy for quality of care; some of the less commonly measured factors including processes of care and individual surgeon caseload, may have a more direct or larger influence on outcomes. This has important implications, given the trend among policymakers to use hospital volume as a central factor in deliberations regarding patient referrals, regionalisation and agreement on accreditation standards for certain procedures. As such, the purpose of this thesis is to explore the potential association and the strength of that association between unit volume and operative mortality in Australia and New Zealand with a specific focus on two areas of cardiac surgery: coronary artery bypass grafting (CAB G), and valve surgery (aortic valve replacement, mitral valve replacement, and tricuspid valve surgery).