A short door-to-balloon time (D2B) is considered a quality of care measure for patients of ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous intervention (pPCI). However, recent literature has documented reductions in D2B that were not associated with improved STEMI mortality. Using the National Cardiovascular Data Registry (NCDR) CathPCI Registry, Nallamothu et al. assessed this apparent contradiction at the individual and population levels. The authors examined 150,116 pPCI procedures performed on 146,940 patients at 423 US hospitals over the course of six years. They assessed both in-hospitality (in the entire cohort) and 6-month mortality (in Medicare beneficiaries ≥ 65 years old) using models that incorporated patient and population-level components relevant to the association between D2B time and outcomes. Over the 6 years included in this analysis, a significant annual decrease in D2B times [86 min (IQR 65–109) in 2005 to 63 min (IQR 47–80) in 2011 (p<0.0001)] was accompanied by an increase in risk-adjusted in-hospital (from 4.7% to 5.3%; p=0.06) and 6-month (from 12.9% to 14.4%; p=0.001) mortality. Multilevel modeling demonstrated that patient specific shorter D2B times were consistently associated with lower in-hospital (adjusted OR for each 10 min decrease 0.92; 95% CI 0.91–0.93; p<0.0001) and 6-month mortality (adjusted OR for each 10 min decrease, 0.94; 95% CI 0.93–0.95; p<0.0001) for individual patients. However, this protective association was not evident at the population level, where the overall annual increase in mortality was independent of patient-specific D2B times.

Conclusions

Shorter D2B times are associated with a patient-level mortality benefit for STEMI. These findings highlight the importance of avoiding interpretation about patient-level associations from studies of population-level results.

 Summarized by Jehu S. Mathew and Steven M. Bradley

Nallamothu BK, Normand SLT, Wang Y, Hofer TP, Brush JE Jr, Messenger JC, Bradley EH, Rumsfeld JS, Krumholz HM. Relation between door-to-balloon times and mortality after primary percutaneous coronary intervention over time: a retrospective study. Lancet. 2014. Nov 19. pii: S0140-6736(14)61932-2.