Fig. 3.
Types of atrial rhythms induced during mediastinal nerve stimulation prior to (preblock, control) and following treatment with hexamethonium or combined α1&2 blockade. Rhythm types were classified as atrial fibrillation/flutter (AF/AFL), sinus tachycardia, sinus rhythm/bradycardia, and other (3- to 4-beat salvos). Rhythm types post α1&2 blockade were subgrouped based upon those in which atrial tachyarrhythmias (including AF/AFL) were extinguished (α-block sensitive; 71.9% of sites) and those in which tachyarrhythmias were maintained (α-block resistant; 28.1% of sites). The number of stimulation sites for each group is indicated above each chart, as well as numbers for each subgrouping of induced atrial rhythms.