The “Making” of a Bundle Branch Block

Abstract

Bundle branch block (BBB) is known to be caused by a wide variety of processes, such as ischemia, inflammation, compression, stretch or degeneration of the conduction system [1]. With the exception of acute myocardial infarction and myocarditis, most of these processes are assumed to operate in a rather slow and progressive way. However, the natural history of BBB is not well known. Several authors studied prospectively groups of patients in whom BBB was discovered during check up examinations, epidemiologic surveys, or clinical consultation for related or unrelated causes [2–5]. With or without a His bundle recording, the patients were periodically reexamined, in order to define their short- and long-term prognosis and to find out signs that might predict the occurrence of complete A-V block, sudden death, or other complications. Although the results are still controversial [6–12], such studies are certainly likely to provide clinically useful information. However, they suffer from two important limitations: 1) in practically none of those studies efforts were made to determine whether the BBB was reversible or irreversible when first observed; and 2) this method of studying the natural history of BBB does not taxe into consideration the early stages. In a way, this is like studying the natural course of ischemic heart disease in patients who have had already a myocardial infarction, overlooking the perhaps more decisive preclinical stages. In this article, we will discuss the earliest stages of chronic BBB. To that effect, we studied 32 patients in whom intermittent BBB (not related to acute events) was documented.