The ECG shows elevation of the ST segment. Patients are placed on continuous ECG monitoring and an intravenous cannula is inserted to allow rapid delivery of drugs or fluids is inserted. Patients are given oxygen by mask and intravenous narcotics for analgesia. The usual cause of AMI is an acute thrombotic occlusion of an atheromatous coronary artery. In the absence of an adequate collateral blood supply the myocardium downstream of the coronary thrombosis will infarct unless blood flow can be restored.
Infarction occurs over hours and myocardium is potentially salvageable by prompt treatment.
The aim is to restore coronary blood flow as quickly as possible. Usually this is attempted by intravenous administration of thrombolytic therapy in the emergency department as soon as the diagnosis is established and any contraindications are excluded. Contraindications are a high risk of bleeding, eg recent surgery, trauma or cerebrovascular accident. Results are best when therapy is initiated within the first four hours from the onset of chest pain. The most common drugs used are streptokinase and recombinant human tissue plasminogen activator.