Mapping of non pulmonary vein triggers for the initiation of atrial fibrillation can be complex and time consuming. We describe a technique where templates are created by pacing from different locations with the right and left atria during sinus rhythm whilst positioning a high definition (HD) Grid catheter along the posterior wall of the left atrium and recording the activation sequence. Following this AF is initiated using decremental atrial pacing and the administration of intravenous isoprenaline and the activation across the HD Grid is compared with the templates. In our case series this appears to easily locate the focus source for the initiation of AF.