Figure 1.

Heterogeneity of pathology in acute myocardial infarction. In the first 3–4 h after the onset of ischaemia, the primary pathology is ischaemia. Accordingly, the emphasis for treatment during this early period is on reperfusion. Delays to treatment are associated with reductions in clinical benefit. Even within those first hours, additional secondary pathological processes begin. These occur because of ischaemia, but they are not amenable to modification by its relief. Moreover, some of these processes, e.g., intramyocardial haemorrhaging, can even be exacerbated by treatments such as fibrinolysis. These heterogenous processes lead to considerable differences in the active processes of injury and repair and variability between patients.