Reperfusion therapy for ST-elevation acute coronary syndromes aims at early and complete recanalization of the infarct-related artery to salvage myocardium and improve both early and late clinical outcomes. Prehospital diagnosis of ST-elevation acute coronary syndrome can be made by echocardiogram (ECG) with or without transtelephonic transmission, and subsequent fibrinolytic therapy can be instituted at home or in the ambulance. Prehospital fibrinolysis decreases time to treatment by about 1 hour compared to in-hospital therapy, resulting in a significant 15% relative risk reduction of early mortality. This may compare well with primary angioplasty for ST-elevation acute coronary syndrome, although more studies are necessary.

Reperfusion therapy has become the indisputable gold standard for the early management of acute ST-segment elevation coronary syndromes. The benefit of this strategy rises exponentially the earlier the therapy is initiated. The highest number of lives saved by reperfusion therapy is within the first hour after symptom onset: a window of opportunity aptly termed the golden hour (1). Clearly and logically, the mechanism of this benefit relates to maximizing myocardial salvage by early restoration of adequate coronary blood flow, resulting in preservation of left ventricular function, thereby enhancing both early and long-term survival.

According to the principle of the infarct wave front by Reimer and Jennings, a brief interruption of blood flow is associated with a small infarct size (2). The temporal dependence of the beneficial effect of coronary reperfusion has also been characterized by multiple metrics, including positron emission tomography (3). Irrespective of the methodology, however, the relationship between duration of symptoms and infarct size remains consistent.

The exponential form of the curve illustrating the benefit of reperfusion therapy on mortality and myocardial salvage has major implications for the timing of treatment. The impact of delay in time to treatment lessens as the duration of ischemia lengthens. Consequently, reducing delays will have a much more positive return in patients presenting early versus those presenting late (4). These considerations have provided strong incentive for the initiation of very early reperfusion therapy, including the use of prehospital fibrinolysis (5).

In 1985 Gotsman and coworkers implemented prehospital triage and treatment of patients with ST-segment elevation myocardial infarction in Jerusalem, Israel (6). They demonstrated the presence of minimal myocardial damage after the early administration of streptokinase. Nine years later, in a larger and randomized prehospital fibrinolysis study, prehospital treatment achieved significantly less Q wave infarctions, which may be correlated with a greater number of smaller infarctions (7). The same trial also demonstrated accelerated and more extensive ST-segment resolution with prehospital treatment suggesting enhanced myocardial perfusion (8). Subsequently, the large In-TIME-2 study demonstrated that with each additional hour of symptom onset to the start of fibrinolytic reperfusion therapy, the chance of achieving complete ST-segment resolution decreases by 6% (9). In an ASSENT-2 substudy, including 13,100 patients, the earlier lytic therapy was initiated, the higher the likelihood of ST-segment resolution on the ECG. Moreover, earlier therapy was inversely related to 1-year mortality (10).

Hence the ultimate objective of reperfusion therapy is early and effective treatment, which can only be established by prehospital treatment.

Clearly, medical history and appropriate electrocardiographic recording is necessary for the proper diagnosis of ST-elevation acute myocardial infarction. Transtelephonic or computer diagnosis can be used for this purpose and seems to be equivalent in accuracy (11). Also, the ambulance staff is important in the quality of prehospital triage. In The Netherlands a national ambulance protocol is used for the triage of patients with suspected acute myocardial infarction to initiate the optimal prehospital reperfusion strategy (Fig. 2-1). Usually ambulances are staffed with nurses with or without physicians. Importantly, nurses seem to work faster than physicians in the diagnosis of ST-elevation myocardial infarction and proper administration of a fibrinolytic agent (Fig. 2-2) (12). This is useful in reducing the treatment delay. In general, treatment delay can be shortened by about 55 minutes using prehospital thrombolysis versus in-hospital thrombolysis (13). This results in a 15% reduction of early mortality in comparison to in-hospital fibrinolysis (Fig. 2-3). This benefit applies to low-, middle-, and high risk patients to about the same extent as depicted in Figure 2-4.