One of the great medical advances in recent years has been the improved treatment of acute myocardial infarction. As the enormous benefits of earlier reperfusion became evident, medical systems in many parts of the world aimed to treat increasing numbers of patients in a shorter time frame. The door-to-balloon (D2B) time as a performance measure has emerged as a key part of this initiative. Now a study published in the New England Journal of Medicine finds that in-hospital mortality for acute MI patients receiving PCI has not fallen despite improvements in the D2B time. But some experts fear this finding may be misinterpreted, as it more accurately reflects a growing and changing population receiving PCI than any shortcomings in the D2B initiative.
Using the CathPCI Registry of the National Cardiovascular Data Registry, Daniel Menees and colleagues analyzed data from almost 100,000 hospital admissions for primary PCI between July 2005 and June 2009.
- Median door-to-balloon times declined over time, from 83 minutes to 67 minutes (p<0.001).
- A greater percentage of patients were treated in 90 minutes or less: from 59.7% to 83.1% (p<0.001).
- No significant change in unadjusted in-hospital mortality: 4.8% and 4.7% (p=0.43 for trend)
- No significant change in adjusted in-hospital mortality: 5.0% and 4.7% (p=0.34).
The authors write that their “findings raise questions about the role of door-to-balloon time as a principal focus for performance measurement and public reporting” and “suggest that additional strategies are needed to reduce in-hospital mortality in this population.” They point out that D2B is only “one component of total ischemic time; as door-to-balloon time is reduced, it becomes a smaller fraction of total ischemic time, making the time before arrival at a hospital a more important factor.”
In an accompanying editorial, Eric Bates and Alice Jacobs write that “the primary opportunity for reducing total ischemic time and time to treatment, and for improving outcomes, now lies in the prehospital STEMI system of care, where logistic challenges remain…. Although door-to-balloon time remains important, it’s time to turn our attention to the further development of systems that address the continuum of STEMI care, from symptom onset through return to the community.”
Another way to view the study results is that they show that the D2B initiative is an apparent victim of its own success by bringing many more difficult-to-treat patients into the system at an earlier period. Harlan Krumholz, a leader of the D2B initiative, explains:
At a patient level shorter times translate into better outcomes and reaffirm the importance of rapid treatment. The paper also reveals the remarkable improvement in care over this period. And overall mortality rates for AMI (not shown in this paper) are dropping impressively. The lack of improvement in mortality over these years for the population of patients undergoing PCI may say more about the changing population of patients being referred for primary PCI over this period (volume grew rapidly – the mortality of those treated in more than 90 minutes increased) than the effectiveness of rapid (as opposed to delayed) reperfusion therapy.
In an interview to be published on CardioExchange, study authors Daniel Menees and Hitinder Gurm propose that
It may be time to move away from D2B time, or at least recognize its limitations and consider its use in the context of other measures. We need to start trying to track total ischemic time (i.e., onset of symptoms) better as well as take a closer look at the false activation rates across different regions and hospital systems. We think this is the real message behind our study – it’s time to look beyond D2B times, and we need start looking at other ways we can favorably impact patient outcomes.