PRACTICAL ASPECTS OF THROMBOLYTIC THERAPY IN ACUTE MYOCARDIAL-INFARCTION

Myocardial infarction (MI) is the result of acute coronary occlusion and the prognosis depends on the infarct size. In experimental studies, infarct size is reduced by early coronary reperfusion which may be obtained by intravenous thrombolytic therapy. This simple, rapid and widely used technique is the clinical treatment of choice. The diagnosis of MI must be confirmed by clinical and electrocardiographic findings. The clinical history is important because the value of reperfusion when started after the 6th hour after the onset of chest pain is questionable. However, it is often difficult to determine the beginning of MI when preceded by unstable angina. Contraindications to thrombolytic therapy must be carefully excluded irrespective of the thrombolytic agent because of the risk of haemorrhage. This must be weighed up against the risk of the MI itself. Therefore, age is not a systematic exclusion criterion. The choice of thrombolytic is based on the efficacy, mode of administration and cost. Heparin therapy at effective doses is associated in all cases to prevent reocclusion. Aspirin is given orally. The association of a calcium inhibitor or a betablocker may also be considered. Reperfusion and ischaemia may give rise to arrhythmias and haemodynamic changes which have to be rapidly corrected. Haemorrhagic complications during thrombolysis are treated according to the severity and time of onset by blood transfusion sometimes associated with a plasmin inhibitor. Reocclusion is an indication for emergency coronary angioplasty but in some cases repeat thrombolytic therapy may be beneficial. When the MI is extensive, rapid transfer to a cardiological centre with catheter facilities is advisable. Even if the hospital course of MI is uncomplicated, thrombolytic therapy does not change the classical strategy in these patients : coronary angiography is always useful when signs of myocardial ischaemia are observed on stress testing. This investigation should almost be systematic in young patients as it contributes to the long term management.