Mapping of activation changes within the acutely ischaemic canine specialised conduction system

Ligation of the anterior septal artery was used to produce acute ischaemia of the specialised conduction system in ten dogs. Activation times at selected positions within the specialised conduction system were recorded. Marked delays of activation occurred between several discrete anatomic sites within the specialised conduction system. This study demonstrates that extremely slow conduction is common in localised areas of the acutely ischaemic infra-nodal conduction system. Heterogeneity of myocardial activation secondary to changes of speed of the conduction during acute septal ischaemia is postulated as a mechanism facilitating the occurrence of malignant ventricular arrhythmias.