ObjectivesCardiac surgery is highly demanding and the ideal teaching method to reach competency is widely debated. Some studies have shown that surgical trainees can safely perform full operations with equivocal outcomes compared with their consultant colleagues while under supervision. We aimed to compare outcomes after cardiac surgery with supervised trainee involvement versus consultant-led procedures. MethodsWe systematically reviewed databases (PubMed/MEDLINE, Embase, the Cochrane Central Register of Controlled Trials, ClinicalTrials.gov, Google Scholar) and reference lists of relevant articles for studies that compared outcomes of cardiac surgery performed by trainees versus consultants. Primary end points included: operative mortality, coronary events, neurological/renal complications, reoperation, permanent pacemaker implantation, and sternal complications. Secondary outcomes included cardiopulmonary bypass and aortic cross-clamp times and intensive care/in-hospital length of stay. Random effects meta-analysis was performed. ResultsThirty-three observational studies that reported on a total of 81,616 patients (trainee: 20,154; consultant: 61,462) were included. There was a difference favoring trainees in terms of operative mortality in the main analysis and in an analysis restricted to propensity score-matched samples, whereas other outcomes were not consistently different in both analyses. Overall cardiopulmonary bypass and aortic cross-clamp times were longer in the trainee group but did not translate in longer intensive care unit or hospital stay. ConclusionsIn the right conditions, good outcomes are possible in cardiac surgery with trainee involvement. Carefully designed training programs ensuring graduated hands-on operative exposure as primary operator with appropriate supervision is fundamental to maintain high-quality training in the development of excellent cardiac surgeons.