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Early coronary reperfusion has been established as the optimal treatment for acute ST segment elevation myocardial infarction. A treatment protocol, previously described, has been designed to reduce delay in achieving recanalization of the culprit coronary artery. Over a period of about 4 years, Door-to-Balloon time has been analyzed for patients arriving in the Emergency Department with this condition. During that time the process was enhanced by the ability of ambulance personnel to transmit 12 lead EKG's from the field. Door-to-Balloon times have been analyzed and compared to the American College of Cardiology target of 90 minutes. After just over one year of gradually improving results, 100% compliance was achieved. From that time on, this was achieved during the period under consideration in 97% of cases.
It has been well established that the optimal treatment for acute ST segment elevation myocardial infarction (STEMI) is recanalization of the occluded coronary artery responsible for the infarct, by coronary angioplasty and stent placement, provided that this can be done in a timely manner. This results in improved left ventricular function and decreased mortality. Results of initial experience with this approach at The Queen's Medical Center have previously been reported.1 With the addition of subsequent experience, cumulative results, now extending through the end of the second quarter of 2011, form the basis for this report.
A new protocol for management was implemented in May, 2007, based on Bradley et al.2 This was described in our previous report and includes activation of the call to the cardiologist and cathlab staff by the emergency department physician, having a group of interventional cardiologists each committed to arrive within 20 minutes, activating a timer at patient arrival, and use of a designated sealed box containing needed supplies. Acceptable limits for time components were established, as listed in table 1. These have been analyzed, with prompt feedback to involved physicians and staff, within 48 hours. The records of all patients arriving in the emergency department with clinical and EKG evidence for STEMI have been scrutinized and entered into a database, in accordance with the specification manual of The Joint Commission and CMS core measures. Those fulfilling the criteria provide the basis for this report. This report combines the experience described earlier with that between October 2008 and June 2011.
A major innovation since the onset of the program has been the equipping of Honolulu City and County ambulances, in May 2008, with the capacity to record and transmit good quality twelve-lead EKG tracings from the field. This has permitted the emergency department physician to call in the cardiologist and the cardiac catheterization laboratory (cathlab) staff prior to the patient's arrival.
A steady improvement in Door-to-Balloon time (D2B) followed initiation of the program. By the third quarter of 2008, the American College of Cardiology national guideline for D2B of less than 90 minutes3 was being achieved in 100% of patients. The total experience is summarized in Figures 1 and and2.2. There has been nearly complete compliance with the 90 minute guideline for D2B, with failure to achieve this in only 4 instances (out of a total of 117), as noted in Figure 1. As seen in Figure 2, median D2B time has been around 60 minutes since 2009. Substantially shorter times have often been achieved, including less than 20 minutes on 2 occasions. Hospital mortality has been 4.7% for the whole group and 4.0% since the time at which 100% quarterly compliance with the 90 minute guideline was first achieved.
STEMI is usually caused by acute thrombotic occlusion at the site of a ruptured atherosclerotic plaque. Early recanalization of the artery has been well established as the optimal treatment. As described by Bradley, et al,2 small reductions in time at various stages of the process added up to a significant decrease in the total D2B time, in our experience. Acceptable time limits are noted in Table 1. Any such subdivisions of the total D2B time that are longer than acceptable are investigated, including discussion with individuals and departments involved.
This approach resulted in a steady improvement in the measures being evaluated, as noted above. In fact the improvement started before the program was formally instituted, presumably as a result of increased awareness of existing problems while planning was in progress. Following the initiation of the program, in May, 2007, improvement continued over the next year, as caregivers became increasingly familiar with the protocol, and has largely been maintained. Maintenance of a satisfactory D2B time has been an ongoing challenge, given a 24/7 operation involving a busy emergency department, and vigilance is needed to insure continued success. Continued regular meetings of the D2B committee, with prompt feedback to involved individuals, has been felt to be the key to success. While we have been gratified to achieve the results described, we hope to effect further improvements in patient outcomes, by incorporating new innovations in cathlab and adjunctive techniques. In a process where time is crucial, there is an advantage to a uniform approach by all operators, and to using methods that do not risk causing delay. These considerations need to be balanced against the potential advantages of modifying the process, to incorporate changes shown to improve prognosis. Such newer techniques were used in a small minority of the cases under review, and are not considered to have impacted outome of the group as a whole. They include:
Since implementing a protocol for the management of patients with acute STEMI, there has been a largely successful maintenance of D2B time within the 90 minute ACC/AHA guideline, with the median recently mostly under 60 minutes. Hospital mortality has been 4.0%, well below national levels. The ability of ambulance personnel to transmit high quality EKGs, prior to hospital arrival has enhanced the process. Further improvement in outcomes is anticipated with evolving cathlab techniques, including the increasing use of the trans-radial approach, of bivalirudin in place of heparin with a glycoprotein IIb/IIIa inhibitor, and in selected cases, of thrombectomy, and the use of newer platelet inhibitors.
The authors recognize that the results achieved are the product of the dedication of many members of the staff at The Queen's Medical Center, and indeed of the City and County ambulance service. We especially thank the many members of the Emergency Department team, and the Cathlab staff, whose willing and prompt response during a 24 hour a day call has been an essential component of the project's success.
None of the authors identify any conflict of interest relating to this report.