[Significance of exercise-induced arrhythmias].

Four personal cases of exercise-induced conduction defects occurring during stress testing are reported. The significance of these changes is discussed in the light of the authors' observations and of the cases published in the literature. The development of atrioventricular block is usually related to pre-existing disease of the conduction system, whilst left anterior or posterior hemiblock is usually due to transient ischaemia related to significant stenosis of the coronary artery responsible for the vascularisation of the relevant bundle branch (usually a proximal stenosis of the left anterior descending artery). Complete left bundle branch block may be due to a number of conditions (including chronic ischaemic heart disease).