Although shorter door-to-balloon (D2B) times have been associated with better patient-level survival, mortality in the overall primary percutaneous coronary intervention (PCI) patient population is increasing despite improvements in D2B times over time, according to a study published Nov. 18 in The Lancet. This seeming paradox has led to great debate in the cardiology community over the last year after a similar finding was published in the New England Journal of Medicine, raising important questions about the role of D2B time as a quality metric and even the causal role of time-to-reperfusion in STEMI.

The new study, led by Brahmajee K. Nallamothu, MD, FACC, attempted to provide a deeper understanding into this paradox that was first raised by the earlier study. The crucial insight of the new study is that the population-level improvements have not occurred in all likelihood because of a changing and growing primary PCI population. The investigators looked at ST-elevation myocardial infarction (STEMI) patients who underwent primary PCI between 2005 and 2011, captured in the ACC’s CathPCI Registry. In-hospital mortality in the entire cohort and six-month mortality in elderly patients aged 65 years or older matched to data from the Centers for Medicare and Medicaid Services were assessed. The researchers analyzed the relation between D2B time and in-hospital and six-month mortality at both the individual and population levels using multilevel models that could examine both of these relationships simultaneously.

The investigators overall findings were that, while shorter patient-specific D2B times remained strongly and consistently associated with decreased risk of mortality at the individual level, larger population trends suggested increased mortality risk in patients undergoing primary PCI. A total of 423 CathPCI Registry hospitals reported data on 150,116 procedures with a 55 percent increase in the number of patients undergoing primary PCI at these facilities over time, as well as many changes in patient and procedural factors. Annual D2B times decreased significantly from a median of 86 minutes in 2005 to 63 minutes in 2011 which was consistently associated at the individual level with lower in-hospital mortality and six-month mortality – but at the same time, a rise in risk-adjusted in-hospital mortality (from 4.7 percent to 5.3 percent) and risk-adjusted six-month mortality (from 12.9 percent to 14.4 percent) at the population level was shown.

“It is important to note that the relationship between D2B time and mortality at a population level should not be construed as representing its relationship at an individual level, which is an ecological fallacy,” said Nallamothu. “The more likely explanation is that sicker patients have been undergoing primary PCI in more recent years, and taken together with the findings of the relationship between D2B time and mortality at the patient-level, it supports the concept that D2B times should remain and important quality metric for hospitals while pointing towards future opportunities for improving STEMI care.”

“Additionally, this study highlights the importance of an open science approach and reproducible research,” note the authors. Access to the same data sources used in the NEJM study also supported by the CathPCI Registry allowed the researchers to build on the earlier work and eliminated the possibility that differences in the findings are the result of variability in data collection methods, study populations or health care systems.

“These findings tell the cardiovascular community that our hard work to improve D2B times was meaningful to patients – and a great achievement. We are pleased to provide this additional insight, extending on what was reported previously,” said Harlan Krumholz, MD, SM, FACC, a member of the ACC’s Board of Trustees and senior author for the study.

Keywords: Registries, Myocardial Infarction, Hospital Mortality, Centers for Medicare and Medicaid Services, U.S., Percutaneous Coronary Intervention, National Cardiovascular Data Registries

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