Combin'ation therapies including thrombolytics may reduce mortality after MI Most patients with an acute myocardial infarction should receive thrombolytic therapy as soon as possible to preserve left ventricular function, reduce the incidence of cardiac arrest, and improve survival. Streptokinase and alteplase are the agents currently available in New Zealand: streptokinase is cheaper than alteplase and superior efficacy cannot, at present, be attributed to either agent. The reduction in mortality is greater when thrombolytic therapy is administered early after symptom onset; mortality has been reduced by 47 and 23% when streptokinase was administered within 1 and 6 hours, respectively, of symptom onset. Late thrombolysis. although not as effective as early thrombolysis. does have beneficial effects on the healing phase of myocardial infarction. and therefore the treatment of late entry patients should be considered Adverse effects include major and minor bleeding complications which occurred in 05 and 2.8%. respectively. of thrombolysis recipients in the large ISIS-2 study. Streptokinase is not clot-selective and thus reduces fibrinogen levels, but this does not appear to increase the incidence of bleeding complications, and may contribute to a decreased incidence of reocclusion. Alteplase is not allergenic and so, unlike streptokinase, can be given repeaiediy without antibodies developing. Aspirin reduced the incidence of stroke, reinfarction and cardiac arrest in the ISIS-2 study and had additive benefits when combined with streptokinase. Aspirin should therefore be administered on presentation and, because the effects of aspirin are not time-dependent, it should be continued on a long term basis. Heparin has been shown to be minimally advantageous after thrombolysis in acute myocardial infarction, but does contribute substantially to the risk of bleeding. Beta blockers, presumably by reducing the rate and force of ventricular contraction, appear to prevent cardiac rupture and hence to reduce early mortality. Since thrombolytics have had no effect on mortality during the first 24 hours of acute myocardial infarction in 2 large studies, a combination of thrombolysis and beta blockade should prove to be beneficial, and appears well tolerated. Long term beta blocker therapy appears justified in patients without contraindications. In patients treated by alteplase, angioplasty had no additional beneficial effect on mortality and it may therefore be wise to restrict invasive interventions to patients with recurrent or very severe ischaemia. 4 INPHARMA'" 1 Jul 1989 Post thrombolysis management should include long term low dose aspirin, exercise testing and general health education on smoking and diet. In conclusion, very large scale trials to compare the efficacy of different thrombolytics, and to assess combination therapies are needed. White HD Acute myocardial infarction a true medical emergency. New Zeaiand Medical Journal 102 281-283. 14 Jun 1989 363 0156-2703/89/0701-0004/0$01.00/0 © ADIS Press

Combination therapies including thrombolytics may reduce mortality after MI

Download PDF Report

Upload
nguyennga
View
213
Download
0

Embed Size (px)

Citation preview

Combin'ation therapies including thrombolytics may reduce mortality after MI

Most patients with an acute myocardial infarction should receive thrombolytic therapy as soon as possible to preserve left ventricular function, reduce the incidence of cardiac arrest, and improve survival. Streptokinase and alteplase are the agents currently available in New Zealand: streptokinase is cheaper than alteplase and superior efficacy cannot, at present, be attributed to either agent.

The reduction in mortality is greater when thrombolytic therapy is administered early after symptom onset; mortality has been reduced by 47 and 23% when streptokinase was administered within 1 and 6 hours, respectively, of symptom onset. Late thrombolysis. although not as effective as early thrombolysis. does have beneficial effects on the healing phase of myocardial infarction. and therefore the treatment of late entry patients should be considered Adverse effects include major and minor bleeding complications which occurred in 05 and 2.8%. respectively. of thrombolysis recipients in the large ISIS-2 study. Streptokinase is not clot-selective and thus reduces fibrinogen levels, but this does not appear to increase the incidence of bleeding complications, and may contribute to a decreased incidence of reocclusion. Alteplase is not allergenic and so, unlike streptokinase, can be given repeaiediy without antibodies developing.

Aspirin reduced the incidence of stroke, reinfarction and cardiac arrest in the ISIS-2 study and had additive benefits when combined with streptokinase. Aspirin should therefore be administered on presentation and, because the effects of aspirin are not time-dependent, it should be continued on a long term basis. Heparin has been shown to be minimally advantageous after thrombolysis in acute myocardial infarction, but does contribute substantially to the risk of bleeding.

Beta blockers, presumably by reducing the rate and force of ventricular contraction, appear to prevent cardiac rupture and hence to reduce early mortality. Since thrombolytics have had no effect on mortality during the first 24 hours of acute myocardial infarction in 2 large studies, a combination of thrombolysis and beta blockade should prove to be beneficial, and appears well tolerated. Long term beta blocker therapy appears justified in patients without contraindications.

In patients treated by alteplase, angioplasty had no additional beneficial effect on mortality and it may therefore be wise to restrict invasive interventions to patients with recurrent or very severe ischaemia.

4 INPHARMA'" 1 Jul 1989

Post thrombolysis management should include long term low dose aspirin, exercise testing and general health education on smoking and diet.

In conclusion, very large scale trials to compare the efficacy of different thrombolytics, and to assess combination therapies are needed. White HD Acute myocardial infarction a true medical emergency. New Zeaiand Medical Journal 102 281-283. 14 Jun 1989 363

0156-2703/89/0701-0004/0$01.00/0 © ADIS Press