The article by Goicolea Ruigómez et al.1 evaluated the results of coronary artery bypass grafting (CABG) in Spain from 2013 to 2015. The study established a proportional relationship between the hospital procedure volume and the in-hospital mortality and rehospitalization rates. The authors’ recommendations were to concentrate CABG procedures in high-volume centers in Spain and publish the risk-adjusted outcomes of these interventions.
In both CABG and percutaneous coronary interventions (PCI), there is a clear link between a higher volume per center and better outcomes.2 In the present article, the volume of CABG procedures was low (less than 200/y) in 87% of our centers. However, the total mortality rate reported in the Spanish Society of Thoracic and Cardiovascular Surgery registries of interventions for 2013 to 2015 was 2.8%, a value lower than the 3% reported in this article for CABG alone. In addition, the risk-adjusted mortality rate has been persistently <0.6, excellent results that are comparable to those recorded by the American (The Society of Thoracic Surgeons) and European (European Association for Cardio-Thoracic Surgery) societies.
The risk-adjusted in-hospital mortality and rehospitalization rates reported indicate that the outcome depends on the hospital volume of surgeries. However, extrapolation of data from administrative databases to analyze clinical events is subject to considerable bias. Variability in the CABG volume and mortality when clinically and administratively contrasted is, in both cases, an unacceptable 20%.3 It is telling that cardiogenic shock is listed among the comorbidities of patients “scheduled” for CABG treatment, and the article mentions that data provided by the Spanish National Health System are not based on “robust and publicly available risk-adjusted outcome indicators supported by consensus between scientific societies and health care authorities.”1 Among the total number of patients who underwent CABG, 15.9% were excluded, mainly those with a principal diagnosis of acute myocardial infarction. Non-Q wave acute myocardial infarction is one of the most common indications for surgery in our centers, and specifically, for CABG alone. Only 64.3% of patients included exclusively underwent CABG, and the additional cardiac procedures were not specified in the remainder. One must be extremely rigorous in drawing conclusions regarding the outcome of CABG by including only patients treated with this procedure alone, to avoid committing serious selection bias with an alarming impact on the results. For these reasons, caution is required when interpreting the conclusions of this article.
Clustering CABG procedures is not the solution to the low volume of coronary surgeries per center in our country. In many Spanish centers4 there has been a disproportionate indication for PCI in patients with left main coronary artery or multivessel disease. The mean number of coronary surgeries in Europe is 380/million population, whereas in Spain it is 108/million; the PCI:CABG ratio is 6:1 in Europe and 2:1 in the United Kingdom and the United States, whereas it is 14:1 in Spain.5 Obviously, as PCI use has grown, the number of CABG performed has decreased. Although PCI provides good immediate outcomes in this context, the current scientific evidence suffices to ensure that it is associated with higher mortality and major adverse events than CABG, particularly at mid and long term.6
Lastly, we completely agree that there is a need to publish outcomes, not only of CABG, but also of PCI, and at both short- and long-term. This is especially important in the local setting of each center. Only when the outcomes of both these treatments are known will cardiology teams be able to select the most appropriate individualized treatment for each patient.
We congratulate the authors for carrying out a study that aims to optimize excellence in the treatment of multivessel disease.