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Changing strategies for managing acute myocardial infarctions

Treatment of acute myocardial infarction has evolved considerably over the past few decades. The first dedicated coronary care units, opened during the 1960s, resulted in reduced mortality. It took a further two decades before thrombolysis was demonstrated to rapidly recanalise occluded coronary arteries (1), and the results of several large, multi-centre trials showed a mortality benefit with streptokinase use, of between 23% and 50% (2,3). Meta-analysis revealed that administering thrombolysis early after symptom onset conferred a significant survival benefit (4), and the importance of prompt treatment was incorporated into various guidelines (5). However, for several years it has been recognised that mechanical intervention is superior to chemical thrombolysis (6). In parallel with the thrombolysis trials, the evidence shows that a primary percutaneous coronary intervention (PPCI) will have the greatest mortality benefit when performed early (7,8). The logistical difficulty is that not all hospitals are capable of delivering PPCI; hence debate continues as to the acceptable time to transfer a patient presenting with ST elevation myocardial infarction (STEMI) from a local community hospital to an interventional centre. Door-to-balloon time (DTB) is defined as the time elapsing between the arrival of the patient at the hospital door and the initial balloon dilatation of an occluded coronary artery. The guidelines suggest the optimum time to be <90 min, with mortality increasing in proportion to DTB irrespective of symptom onset-to-door time (9,10). Single-photon emission computed tomographical (SPECT) imaging using technetium-99m sestamibi has been used to evaluate myocardial salvage and infarct size following PPCI and has been shown to correspond to left ventricular function and volumes. Longer DTB correlates with larger infarcts when assessed using this technique (11). Many factors have been identified as presenting potential obstacles to achieve DTB of <90 min. Strategies to encourage timely PPCI include publicity campaigns to familiarise the general public with the symptoms of a heart attack, as late presenters have been shown to have longer DTB and even reduced likelihood of receiving reperfusion therapy (12). Paramedic crews have been educated in STEMI recognition, facilitating field triage, bypassing the emergency department (ED) (13). This shortens DTB and results in improved early survival (14,15). The impact of ED physician activated PPCI has been shown to reduce DTB (16), as have measures to expedite involvement of cardiac laboratory staff, such as Cardiologists being contacted by mobile telephone rather than pager (17). Prioritising transfer of STEMI patients to regional sites, known as STEMI Receiving Centres in America, has shortened DTB (18). Others however, document reduced DTB when PPCI is carried out in community hospitals with off-site cardiac surgery backup, with comparable clinical and procedural success to the regional centre (19). Finally, auditing practice results in improved DTB (20). In 2008, the American College of Cardiology launched the Door-to-Balloon Alliance, enrolling approximately 1000 PCI hospitals in a quality improvement programme through promotion of effective strategies (21). The findings of an audit of performance of 167 hospitals have recently been reported, detailing a 20% increase in the number of patients with DTB <90 min between the period July–September 2006 (DTB <90 min in 54.1% patients) and January– March 2008 (DTB <90 min in 74.1% patients). The traditional route to primary angioplasty involves the patient being transported to the centre in which the PPCI operator practices, termed patient-to-physician. However in a bid to further reduce DTB, the concept of transferring the physician to the patient has recently been introduced (22). This requires the Cardiologist travelling to the patient’s local hospital to perform PPCI, potentially bypassing the need for inter-hospital transfer and the time delay this may incur. Zhang et al. compared 334 STEMI patients randomised to receive PPCI either at their presenting hospital (physician-topatient) or from their regional centre (patient-tophysician). They documented comparable procedural success and length of stay in hospital. DTB was significantly reduced using the physician-to-patient model (95 ± 20 min vs. 147 ± 29 min) and the percentage of patients receiving PPCI in <90 min significantly increased (21.2% vs. 7.7%). The composite incidence of major adverse cardiac events (MACE), defined as death, non-fatal re-infarction and target Strategies to encourage timely PPCI include campaigns to familiarise the public with heart attack symptoms Linked Comment: Kong et al. Int J Clin Pract 2009; 63: 1693–701. 1670 Editorials