Effects of -blockers and calcium channel blockers in acute myocardial infarction
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beta-blockers and calcium channel blockers have been evaluated extensively during the acute phase and following myocardial infarction. beta-blockers, when administered early and intravenously, reduce early mortality, reinfarction and cardiac arrests by about 16%. The reduction in mortality is likely to be due to multiple mechanisms including reductions in cardiac rupture, reinfarction and ventricular fibrillation. Recent data also suggest a reduction in intracranial haemorrhage when administered in conjunction with thrombolytic therapy. Prolonged use of beta-blockers for a year or two after myocardial infarction leads to significant reductions in total mortality, sudden deaths and reinfarction. The benefits of beta-blockers are probably mediated through a number of mechanisms, including reduction in heart rate and prevention of plaque rupture, in addition to the mechanisms stated above. Calcium channel blockers do not reduce mortality. It appears that some agents that increase heart rate (e.g. dihydropyridines) may increase the risk of death and reinfarction. On the other hand, agents that reduce heart rate (verapamil and diltiazem) appear to have a neutral effect on mortality but may reduce reinfarction rates. The benefits of beta-blockers appear to be consistent in most subgroups of patients examined, whereas the adverse effects of calcium channel blockers are most marked in those with large infarcts or heart failure. In conclusion, beta-blockers are preferable to calcium channel blockers in the acute phase and long-term after myocardial infarction.
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