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The “limbo” is a dance that originated in Trinidad. Participants dance below a pole that is held horizontally and is moved lower and lower as the dance progresses. Dancers who touch the pole or fall backward are excluded from further dancing. Most of us over the age of 40 can visit the bar only at the outset, because few of us have all 3 of the attributes—excellent balance, leg strength, and spinal flexibility—necessary for continued participation.
These requirements bring to mind the old adage, “Good, fast, and cheap—pick any 2.” Hospitals that treat patients with ST-elevation myocardial infarction (STEMI) are hearing the music and trying to turn back the clock. Only, instead of a Reggae band, emergency response systems and regional advisory councils are playing the music. During the next decade, the emergency response to MI is likely to become similar to the response to trauma in most metropolitan areas: patients will be taken not to the closest hospital, but to institutions that consistently open infarct-related arteries in a timely fashion. We use the phrase “timely fashion” rather than 90 minutes because, when the music starts, the bar begins to fall soon thereafter. A short-term goal will be patient contact-to-open artery in less than 90 minutes, and the only place to shave off time is the door-to-balloon time (DBT). Eventually, the combined efforts of public education and emergency response systems will enable the setting of goals for symptom onset-to-balloon time. Can this actually be done? The success stories of Seattle's response to sudden death and the Minneapolis Heart Institute's treatment of STEMI suggest that it can. In addition, we have set up a program that is working very well here at the Texas Heart Institute at St. Luke's Episcopal Hospital.
Treating patients in a timely fashion requires systemization of care—a taboo subject for many physicians. However, a timely and coordinated response to a clinical event requires a protocol that is performed the same way every time, regardless of who the treating physician is, which department first sees the patient, and whether patients come via Emergency Medical Services (EMS) or on their own. That system must be laid out so that participants in the patient's care can walk in at any point in the process and know exactly where they are in the script. An example is shown in Figures 1 and and22.
The first step in creating systemized care is measurement. Each component of the patient's care must be assigned to someone whose performance is measured. Once the duration of each component of care is measured, you set goals for performance. Missed time-performance goals most often result from problems with the design of care, rather than the efforts of individuals. Maximizing the efficiency of each component requires an interdisciplinary group of emergency department physicians and nurses, radiologists, cardiologists, cath lab nurses, pharmacists, coronary care unit nurses, and, notably, an administrator; change cannot happen unless your administrator helps with the funding or reassignment of full-time employees.
As with any major change, problems might arise, including resistance to changing local culture and tradition. The people who have the most difficulty accepting systemized care are those who say, “I've been doing this for 30 years. You don't need to tell me how to treat myocardial infarction.” Although this statement is frequently true, treating STEMI is not the job of an individual but of several people who must act quickly and with coordination. As the United States Army will tell you, quick and coordinated is difficult.
Like all other steps, the angiographic examination should be scripted. Participating physicians must agree on the necessary tools and pharmacologic agents so that a portable kit containing them is immediately available at the patient's bedside. The physician's job—performing a diagnostic examination—should be completed as quickly as possible, leaving 15 minutes of buffer time in order to plan for the possibility of a difficult revascularization procedure. Unfortunately, some patients have particularly challenging anatomy or other conditions that may impede revascularization.
Accountability is even more crucial than measurement. No one likes to hear that he or she is the reason that a target was missed. In particular, no interventional cardiologist wants to hear, “Dr. Wilson, you completed this case in 96 minutes. You took 45 minutes in the lab to achieve a patent artery. In your component of care, you failed.” That kind of feedback is usually received only once; all subsequent cases are done more quickly, or the reasons for delay are clearly documented. Accountability extends to every member of the treatment team, including nursing-education and ancillary-care personnel. Each individual receives a grade within 48 hours of the procedure's completion.
The principal financial barrier to systematizing treatment for STEMI patients is obtaining funding for a full-time employee who can coordinate these patients' care. This is crucial because communication must be seamless between each component of care—the EMS, the emergency department, the catheterization laboratory, and the participating physicians. Unless one person—to whom all are answerable—coordinates this communication, anyone can have an excuse for poor performance, which is a recipe for failure.
After assigning a hospital employee to be the coordinator, the next step is deciding whether your institution will provide care 24 hours a day, 7 days a week, 365 days a year, or whether to coordinate with another institution that will provide that care and accept all emergency transfers of suspected STEMI cases. At the Texas Heart Institute, a single physician is designated to treat STEMI during each 24-hour period. That physician, the catheterization laboratory, the nurses, pastoral care—everyone is paged immediately and simultaneously when you call the hospital operator and say, “STEMI, John Smith, room 24.” A one-button page sent out from the call center allows much faster response than does paging of individuals.
With nursing personnel, we have had to be creative. If only one cath lab tech has arrived when we need to begin the case, a cross-trained night call-nurse can provide pharmacologic assistance from our infarct cart, enabling treatment to begin before all assigned staff members have reached the hospital.
Coordinating with local EMS has proved even more important. Many ambulance crews can perform electrocardiograms. If they see evidence of STEMI, they can send the electrocardiogram digitally, thereby activating our system while the patient is being transported. This has substantially improved DBTs, our shortest being 16 minutes.
The results of systemizing care are shown in Figure 3. In January 2008, no patient had a DBT <90 minutes. By April, just under 40% of patients had a DBT <90 minutes. The systematized protocol and the new call schedule were instituted on May 1. For the first 8 months, the protocol was used with all eligible patients, and our DBTs were consistently <90 minutes.
The next step in coordination with EMS is for the regional advisory council to determine which area hospitals are willing and able to provide timely STEMI care. All participants will submit data to a database so that the regional advisory council can audit performance and ensure that each institution meets the requirements for a STEMI hospital. This is the same procedure that is currently used for trauma.
For more information about setting up this type of program, visit the Society of Chest Pain Centers of America's website (www.scpcp.org).
Salvaging the myocardium after STEMI depends not only on timely reperfusion but also on how well reperfusion injury is handled. During that first golden hour after symptom onset, reopening the artery quickly will result in a smaller MI. Most patients with STEMIs present within 1 to 4 hours of symptom onset. The most rapid myocardial loss occurs during this period, increasing the risk of reperfusion injury, which enlarges the MI. Reperfusion injury results from platelet embolization and from the generation of reactive oxygen species, which can promote inflammation and destroy proteins within cells. Thus, the cells become overloaded with calcium and enter tonic contraction. The reactive oxygen species also increase mitochondrial permeability, causing the generation of more oxygen radicals within the cells. This self-perpetuating cycle keeps the cells contracting until they die.
Finding a way to disrupt any part of this cycle has been an area of active research interest. Only recently has there been any evidence of clinical success. Some available drugs might work—including erythropoietin, atrial natriuretic peptide, and, oddly enough, atorvastatin. Perhaps there is a reason why the MIRACL Trial found statins to have positive effects even before they could cause any reduction in cholesterol levels.
Interestingly enough, cyclosporine inhibits reperfusion injury. A small trial by Piot and colleagues1 examined the effects of administering cyclosporine (2.5 mg/kg bolus) to patients before transporting them to the cath lab. The idea was that the cyclosporine would affect mitochondrial pore opening. Rather than clinical endpoints, investigators examined infarct size estimated from creatine kinase curves or troponin levels. In patients treated with cyclosporine, the area under the creatine kinase curve was substantially reduced, which suggested that cyclosporine ameliorates reperfusion injury. In Europe, a similar small trial (n=20 in each arm) showed that administering thrombolytic streptokinase (250 units) to MI patients led to a substantially reduced end-systolic volume at 2 days and at 6 months after infarction.
As recent studies have shown, measuring infarct size with cardiac magnetic resonance imaging (MRI) is a useful way to assess reperfusion injury. In a study by Sardella and colleagues,2 MRI showed that the use of a particular thrombectomy catheter reduced the area of microvascular occlusion from 73% to 32% of the infarct, indicating a significant reduction in infarct size.
To implement the systemization of patient care for STEMI, you first must find champions who can change opinions among emergency department and cardiology staff members and in the administration. Then, start measuring times from door to diagnosis and from diagnosis to intervention, and determine which steps in the chain can be completed more quickly than is now the case. Also, you need a multidisciplinary taskforce, because all participants have to buy in—the emergency department, your infarct-response team, and the cardiac cath lab. Last, develop systems and protocols so that everything is scripted. That way, everyone knows what he or she is supposed to do and what is going to happen next.
Reducing post-reperfusion injury is probably the next major step in improving infarct care. We will almost certainly see more trials, most of which, I suspect, will use MRI to measure infarct size. As with Horizon's AMI trial, most patients who qualify for clinical trials will have such a low probability of death, even during follow-up, that demonstrating a 20% reduction in mortality rates will require trial sizes of 15,000 to 20,000 patients. Therefore, I believe that future studies of reperfusion injury will measure infarct size solely by nuclear scintigraphy or MRI.
Address for reprints: James M. Wilson, MD, 6624 Fannin St., Suite 2480, Houston, TX 77030
Presented at the 9th Texas Update in Cardiovascular Advancements; Houston, Texas; 4–5 December 2009
Program Director: James T. Willerson, MD