An 84 year old man who presented with Stokes Adams syncope with exertion was found to have complete heart block on walking with reversion to sinus rhythm on recovery. The resting ECG showed evidence of ischemic heart disease with old anteroseptal and old inferior infarction but there was no recent myocardial infarction as shown by normal cardiac enzymes levels. The probable explanation for the mechanism and causation of the transient A-V block is described.