“…In the case presented here (angina, diabetes mellitus, myocardial infarction) and even in other forms of heart disease, right bundle-branch block may come and go if the right bundle is involved in a zone of ischemia or inflammatory edema. Its conductivity at any given time is affected by the degree of ischemia present at that time, since the conductivity is depressed but not abolished (6). The bundle is able to conduct when the cycle length is long enough to allow for the increased time needed for the bundle to recover.…”