Of 425 patients with acute myocardial infarction admitted to a coronary-care unit 77 (18 per cent) had ventricular conduction blocks. Complete heart block developed in 43 per cent with right-bundle-branch block and left-axis deviation, in 17 per cent with left-bundle-branch block, and in 6 per cent without ventricular conduction blocks. In-hospital mortality was 30 per cent in patients with and 14 per cent without ventricular conduction block. Late sudden death occurred in five of six patients with right-bundle-branch block and left-axis deviation who had transient complete heart blocks during myocardial infarction, whereas eight similar patients with complete heart block with permanent pacing were alive. These findings suggest that patients with this form of block with an acute myocardial infarction should have temporary standby pacemakers inserted. If complete heart block develops in such cases in association with an acute myocardial infarction, even though transient, permanent pacing should be instituted. IN patients with acute myocardial infarction the presence of bundle-branch block has been noted to be associated with a higher mortality and an increased frequency of complete heart block.2 Recognition of the existence of bilateral bundle-branch blocks and, recently, trifascicular blocks has stimulated interest in the clinical meaning of ventricular conduction blocks. Several forms of bilateral bundle-branch block have been described; these include right-bundle-branch block with left-axis deviation (RBBB-LAD), right-bundle-branch block with right-axis deviation (RBBB-RAD), right-bundle-branch block (RBBB) alternating with left-bundle-branch block (LBBB), and LBBB with a prolonged PR interval. These varieties of bilateral bundle-branch blocks have been recognized as.
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