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The treatment of patients presenting with acute ST elevation myocardial infarction (STEMI) has evolved tremendously during the past 25 years. From conservative observation and hemodynamic support in the early 1980s, to contemporary urgent reperfusion, the observed age-adjusted mortality has decreased from 407 per 100,000 in 1988 to 286 per 100,000 in 2004 (1). Major contributors to this success have been the use of acetylsalicylic acid and reperfusion using thrombolysis.
The next step in further decreasing mortality from STEMI has been explored in the past 10 years, with more than 20 trials examining the role of primary percutaneous coronary intervention (PCI) as the preferred approach to rapid reperfusion. Compared with thrombolysis, primary PCI is associated with a higher percentage of reperfusion and a comparable rate of significant bleeding incidents (2). More importantly, when performed in a timely fashion at a centre with experience, primary PCI consistently reduces short- and long-term mortality by 15% to 25%, reinfarction by 50% to 60% and stroke by 50% (3). In parallel with the primary PCI success story, there have been disappointing results from trials examining the role of adjuvant antithrombotic drugs on mortality of STEMI patients treated with thrombolysis (4,5). Hence, the evidence in favour of primary PCI has become so convincing that, according to the updated American Heart Association/American College of Cardiology 2007 guidelines on STEMI (6), primary PCI should be performed in patients presenting at PCI-capable centres within 90 min of arrival. As a consequence, the number of tertiary care centres offering primary PCI therapy 24 h/day, seven days per week has been increasing steadily in Canada (7).
Because of the immense territory and small population, many Canadian STEMI patients are presenting to smaller community hospitals without catheterization laboratories. How then, should we care for patients presenting to centres that are not equipped to offer PCI? This is the question raised by Janda and Tan (8) in the current issue of The Canadian Journal of Cardiology (pages e382–e384). The article detailed the initial experience of transferring STEMI patients from the Chilliwack General Hospital (CGH; Chilliwack, British Columbia) to the Royal Columbian Hospital (RCH; New Westminster, British Columbia) for primary PCI, and compared this strategy with thrombolysis. For the purpose of this exercise, effectiveness was measured by comparing time delays to revascularization in the context of the recommendations published in the American Heart Association/American College of Cardiology guidelines. This update recommended that fibrinolysis should be given (within 30 min of first medical contact) to patients who cannot be transferred to a PCI centre and undergo PCI within 90 min of first medical contact (6). The rationale behind this recommendation stems from a published meta-analysis (9), involving more than 3500 subjects, that compared transfer for primary PCI versus on-site thrombolysis. Transfer for PCI (always less than 3 h delay) was associated with a 42% reduction in the rate of death, reinfarction or stroke (P<0.001).
There is a distance of 83 km between CGH and RCH, a journey that takes 45 min to 60 min by ambulance, depending on the time of day, traffic and road conditions. This leaves only 30 min to 45 min to perform the numerous pre- and post-transport steps. Any single delay in this long chain of events will result in exceeding the 90 min door-to-balloon time limit. In reality, the CGH is on the border of the RCH primary PCI transfer program area. Given the time constraint, this is a geographic position demanding the utmost efficiency in all steps of the process.
Invariably, successful programs result from the seamless collaboration of very different health care professionals, including managers, emergency physicians and staff, emergency transport personnel as well as catheterization laboratory teams guaranteeing continuous 24 h/day coverage with rapid response times. Most importantly, the efforts must be spearheaded by a coordinating committee responsible for the design of an institution-specific protocol, accepted by all involved parties and disseminated through hours of meetings and lectures. Data collection and ongoing monitoring of the process are also imperative to enable rapid feedback to everyone involved.
Janda and Tan reported on a retrospective chart review of the first 67 patients who presented to the emergency department of the CGH with confirmed STEMI during the initial two years of the regional RCH STEMI transfer program (2004/2005). The first important finding resides not in patients who were reperfused, but in those who were denied this therapy. Indeed, 27 patients (40%) with STEMI did not receive thrombolysis or primary PCI for a variety of reasons, including advanced age alone. Often, patients with contraindications to thrombolysis are ideally suited to benefit from primary PCI, irrespective of the delays involved. There is no age limit to benefit from reperfusion. In patients older than 75 years of age, there is some degree of controversy about the overall effect of thrombolysis on mortality (10,11), in the context of increased rate of stroke. The beneficial effects of primary PCI, on the other hand, are not age specific and tend to increase as mortality risk becomes higher (12). Hence, patients with contraindications to fibrinolysis are ideal candidates to initiate a PCI transfer program, allowing health professionals to work out the bugs and perfect the system.
Of the 40 patients who were reperfused, only eight were selected to be transferred for primary PCI – an average of one patient every three-months! Considering the complexity of the task, the distance involved and the lack of preparation to implement such a program, it is not surprising to end up with disappointing delays in reperfusion (average door-to-balloon time of 186 min). The breakdown of delays, detailed in the table, is revealing as to which steps could be expedited. On average, the 90 min limit was already reached by the time patients were leaving the emergency department for the ambulance transfer. This delay could be shortened significantly by improving communication channels, using infield electrocardiograms and establishing transfer priority for STEMI patients. A more efficient and predictable transfer procedure would also help the receiving catheterization laboratory to decrease the door-to-balloon time at the RCH (13).
Most importantly, when a primary PCI transfer program is initiated, the majority of eligible STEMI patients should be included, particularly when the volume of STEMI in the community is low. The rapid transfer of a single STEMI patient requires the concerted effort of a dozen individuals who happen to be on duty at that time. But maintaining an efficient transfer program requires hundreds of professionals to achieve and maintain proficiency in their respective fields. This can only be accomplished through repetition and critical feedback. The exception to this rule would be for the patient who presents within 90 min to 120 min of the onset of symptoms. Indeed, the advantage of primary PCI is modulated by time to presentation (and risk profile). As time from symptom onset to presentation increases, so does the mortality reduction associated with primary PCI (14,15). For example, a subset analysis of the Comparison of Angioplasty and Prehospital Thrombolysis In acute Myocardial infarction (CAPTIM) trial (16) indicated that pharmacological reperfusion may be more effective (or equivalent) than primary PCI within this early time window. Even when thrombolysis is given, immediate transfer should be considered for high-risk patients such as those with hemodynamically compromising ventricular arrhythmia or Killip class of greater than 2, given the encouraging results of recent rescue PCI trials (17,18).
Improvement in medical care is often met with inertia, the magnitude of which depends on several factors, such as upfront cost, complexity or local referral patterns. In the case of primary PCI, inertia resides in our inability to work together and plan ahead. Success will come to centres in which individuals are capable of establishing connections between emergency medical services technicians, nurses, physicians, administrators and between professionals from different institutions. Only then will our remote communities benefit from more effective therapies available in larger centres, a goal shared by most Canadians.