The relationship between procedure volume and prognosis after a percutaneous coronary intervention remains unclear. Intuitively, we tend to think the larger the volume, the better the results and, consequently, the lower the mortality. But when analyzing the literature, we find studies for and against this thesis.

Evidence does support the idea that volume improves outcomes in specific procedures such as chronic total occlusions, but when considering all PCI procedures in the daily practice, the differences tend to disappear.

This study provides current information from one of the few countries with a representative national registry of percutaneous coronary intervention procedures.

All adult patients undergoing PCI in 93 national hospitals in the UK between 2007 and 2013 were included. Data was provided by the British Cardiovascular Intervention Society and adjusted for differences.

Also read: “Less volume, more mortality: should we worry?”

Of 427,467 performed procedures (22% primary PCI) mortality rate at 30 days was 1.9% (4.8% in primary PCI). 87.1% of centers performed between 200 and 2000 procedures a year.

In centers that had between 200 and 399 procedures a year, there was a smaller proportion of primary PCI (8.4%) compared to centers with 1500 to 1999 interventions a year (with nearly one fourth of procedures ─24.2%─ in the context of ST elevation MI).

However, even though smaller volume centers did less primary PCI procedures, proportionally more were done for MI in the context of cardiogenic shock (8.4% vs 4.3%). This could be explained simply by the fact that more serious cases are generally taken to the nearest center possible.

Also read: “Outcomes still associated to operator experience and center volume”.

For the entire cohort (and after multiple adjustments) no evidence of better or worse outcomes were found to be associated to the number of procedures performed in one year. This was true even for primary PCI outcomes.

Conclusion

After adjusting for multiple variables, this study supports the idea that there is higher mortality in centers with smaller volume of percutaneous coronary intervention procedures.

Editorial Comment

Even though methodologically correct, adjusting for multiple variables is still a limitation to this study; however, given the fact that randomization could be impossible in real life, we must believe these figures. 

The difference in cardiogenic shock rates could be explained by the higher selectivity of high volume centers. This requires further research, since a recent study has shown cardiogenic shock patients evolve better in high volume centers.

Finally, these data could be true only for places like the UK, where operators performing less than 75 PCI procedures a year are discouraged from practicing. Indeed, in these countries, operators from centers with smaller volume attend PCI sessions for training purposes, to maintain experience. This detail could make all the difference, since “lower volume centers” is not necessarily synonymous with “low volume operators”.

Título original: Total Center Percutaneous Coronary Intervention Volume and 30-Day Mortality. A Contemporary National Cohort Study of 427 467 Elective, Urgent, and Emergency Cases

Referencia: Darragh O’Neill et al. Circ Cardiovasc Qual Outcomes. 2017;10:e003186.

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