Door-to-Balloon Time in ST-Elevation Myocardial Infarction is an Established Quality Indicator, but Does Reducing it Save Lives?

Results from several interesting studies that looked at efforts to decrease door-to-balloon time in ST-elevation myocardial infarction (STEMI) and whether time reductions had any effect on mortality rates were presented during abstract poster sessions and abstract oral sessions Monday and Tuesday at the American Heart Association Scientific Sessions 2009.

In "Impact on Door-to-Balloon Time of Integrating Pre-hospital Electrocardiograms into Systems of Care: The Mayo Clinic Pre-hospital Electrocardiogram Program," Henry Ting and colleagues at the Mayo Clinic looked at whether the use of pre-hospital electrocardiograms (PH ECG) can decrease door-to-balloon time for patients with STEMI. Mayo implemented a PHECG program with an emergency medical services provider. During the "pre-phase" of the program, no PH ECG protocol was implemented. During the "post-phase" of the program, patients were designated as "Definite STEMI" when the "computer and paramedic had concordant interpretation" of new STEMI in the patient; "Possible STEMI" when the computer and paramedic interpretations differed; and "Not STEMI." A designation of "Definite STEMI" activated the hospital's cath lab and enabled the patient to bypass the emergency room.

The authors reported that for pre-phase patients transported by the emergency services company, median door-to-balloon time was 61 minutes. During the post-phase, median door-to-balloon time for "Definite STEMI" patients was 32 minutes (median for "Possible STEMI" was 67 minutes and median for "Not STEMI" was 66 minutes).

Impressive results, but does a reduced door-to-balloon time have a beneficial impact on mortality? Anneliese Flynn and colleagues presented results from their study, "Reducing Door-to-Balloon Time in Patients with ST-Elevation Myocardial Infarction Undergoing Percutaneous Coronary Intervention: Does a Decrease in Door to Balloon Time Translate into a Reduction in Mortality?" which looked at change in door-to-balloon time and mortality rates in a cohort of 8,770 STEMI patients who underwent primary PCI from 2003-2008 as part of the Blue Cross Blue Shield of Michigan Cardiovascular Consortium. The authors reported that although median door-to-balloon time "decreased dramatically" over the period of the study-only 28.5% of patients in 2003 experienced door-to-balloon times of 90 minutes or less; by 2008 the percentage had increased to 67%‑‑overall mortality was basically unchanged (4.1% in 2003 compared to 3.6% in 2008).

However, the authors of another study reported positive benefits from a reduction in door-to-balloon time in primary PCI for the treatment of STEMI. Robert Minutello and colleagues presented "Community-based Fire Department Ambulance Protocol Reduces Door-to-Balloon Times in ST-Elevation Myocardial Infarction," which examined the results from a program to track STEMI patients who presented for primary PCI implemented by the Fire Department of New York City, New York Presbyterian Hospital, and Cornell Medical College. Researchers also analyzed whether the program helped to reduce door-to-balloon times and whether this led to "a reduction in myocardial necrosis as measured by creatine kinase - MB (CKMB) levels."

Researchers identified 189 consecutive STEMI patients treated with primary PCI before and after the program was implemented. In this study, door-to-balloon time was defined as "emergency room nursing triage to intra-coronary device time." CKMB levels were measured for all patients and plotted. Researchers integrated and measured the area under the curve (AUC) and used "a curve estimation regression model using the natural logarithm (ln) of AUC [CKMB]"‑‑considered to be "the best correlate of total CKMB enzyme released"‑‑to evaluate the effect of DBT on myocardial cell death."

The authors reported that patient angiographic and clinical variables were similar pre- and post-implementation of the program. There was a "significant decrease" in average door-to-balloon time post-implementation (to 78 minutes from an average of 95 minutes prior to implementation). They also found "significant correlation" of ln AUC [CKMB] with respect to door-to-balloon time, with door-to-balloon time remaining "a significant independent predictor of ln AUC [CKMB]. The authors also reported that data from the participating hospitals shows that door-to-balloon time was "independently predictive of CKMB levels," with the time reduction leading to a decrease in myocardial necrosis.