Atrioventricular block: incidence in acute myocardial infarction and determinants of its "degrees".

There are several reasons why an atrial impulse may not reach the ventricles; only one of them is A-V block. Widespread failure to appreciate this simple truth is mainly responsible for the persisting confusion in the diagnosis and treatment of heart block. We have defined and illustrated the various "degrees" of A-V block; applied our definitions in analyzing the examples of block encountered among 300 consecutive incidents of acute myocardial infarction; listed, discussed, and illustrated the several factors that determine conduction ratios and, therefore, the "degree" of block; and used references and illustrations from widely accepted authorities to substantiate our claim that diagnostic and, therefore, therapeutic chaos reigns.