Prehospital Diagnosis and Management of Acute Myocardial Infarction

The outcomes of patients suffering from acute myocardial infarction are contingent on the time taken to deliver definitive treatment. Evidence has shown that the extent of myocardial salvage is greatest if patients are reperfused in the first 3 h from the onset of symptoms [1]. For every 30-min delay in coronary reperfusion, the relative 1-year mortality rate increases by 7.5% [2]. This has driven physicians and policy-makers to popularize phrases such as ‘time is myocardium’ and concepts such as ‘door-to-balloon’ time—the latter representing the time to reperfusion with an intracoronary device from the arrival of the patient at hospital (Fig. 2.1). The biggest delays and challenges in reducing the time to reperfusion, however, are in fact mostly seen in the prehospital setting. This consists of the time from the onset of symptoms to first medical contact (FMC) and subsequently the time from FMC to diagnosis and then reperfusion treatment—termed ‘system delay’. Patient delay may be multifactorial and depends on a host of issues including socioeconomic factors and access to healthcare. The rapid patient assessment and field diagnosis of myocardial infarction has become a crucial factor in time to reperfusion as it dictates the decision on the most appropriate form of reperfusion treatment accounting for geographical factors and available facilities. Importantly, the prehospital role in the management of acute myocardial infarction also involves the initiation of therapy, the upstream of the hospital-delivered treatment. This commonly involves the administration of antiplatelet and anticoagulant therapy in metropolitan areas, while in remote areas where patients cannot be transferred to hospital facilities in a reasonable time, there are policies in place for administration of field thrombolytic agents. Other aspects of the management may involve intravenous access or, indeed in the cases of cardiac arrest, cardiopulmonary resuscitation. In this chapter we will discuss the management of patients presenting with acute myocardial infarction, in the crucial period ahead of their arrival at the heart attack centre.