LAUSR

In manual disciplines, increasing levels of practice are expected to parallel the individual’s ability to perform a specific action or technique. In the field of interventional cardiology, a skilled operator is able to optimize all the steps of percutaneous coronary intervention (PCI), from vascular access to stent implantation, while reducing the total amount of contrast dye administered and procedural time. On top of sound clinical judgment, these factors may translate into a better prognosis. Improved outcomes with proficient operators are even more obvious in complex anatomical (e.g. left main disease or chronic total occlusions) and clinical (e.g. primary PCI or cardiogenic shock) settings, or at the time of managing procedural complications (e.g. perforations, dissections, or bleeding). Based on European guidelines for myocardial revascularization, interventional cardiologists are considered independent operators if they have personally performed at least 200 PCI procedures under the guidance of a supervisor, including a third of cases performed in the setting of an emergency or an acute coronary syndrome (ACS). Maintaining proficiency in interventional cardiology also requires a certain volume of procedures performed per year, e.g. at least 75 PCIs in the context of an ACS or at least 75 PCIs in the context of stable coronary artery disease. All these recommendations are class IIa, indicating conflicting evidence and/or a divergence of opinion about the true impact of practice volumes on the early prognosis of PCI (the so-called ‘volume–outcome relationship’). A study of more than 3 million procedures from the National Cardiovascular Data Registry CathPCI registry, which collects detailed information on >90% of PCIs performed in the USA, recently suggested an inverse relationship between operator volume and in-hospital mortality that persisted in risk-adjusted analyses. In this issue of the European Heart Journal, Hulme et al. add to the debate on the volume–outcome relationship with conflicting findings from the UK’s perspective. Using data from 133 970 PCI procedures performed by 540 interventional cardiologists in England and Wales, the authors did not find a significant relationship between 30-day mortality and operator volume (defined as the total number of procedures the operator was responsible for in the previous 12 months) after accounting for operatorand center-level effects and adjusting for case-mix and potential confounders. This finding, which was consistent across subgroups of patients presenting with ACS or undergoing primary PCI, and in a sensitivity analysis using in-hospital mortality as the outcome measure, applies to a quite contemporary (2013–14) scenario where radial access was the dominant strategy, most patients had an ACS, 30-day mortality was 2.6%, the median volume across all procedures was as high as 178 per year, and only 5% of procedures were performed by low-volume operators. These figures should be considered when generalizing the study findings outside the boundaries of the UK, where many countries have lower operator volumes. To put these results in perspective, for example, the proportion of operators who performed <50 PCI procedures per year was only 14% in this study vs. 44% in the CathPCI registry. Compared with previous studies addressing the volume–outcome relationship in PCI, this report has several strengths. First, the definition of operator volume was based on a rolling measure that allowed the updating of operator volume every month instead of using the calendar year as a reference value. Through one year (i.e. from January to December), this approach overcomes the caveat of considering the total number of PCI procedures performed up to December (i.e. a future calendar date) when assessing 30-day mortality in January. Second, the British Cardiovascular Intervention Society registry is one of the few platforms in Europe offering complete national coverage of all consecutive patients undergoing PCI with subsequent administrative linkage to mortality outcomes. Third, the authors must be congratulated for proficiently undertaking complex