Figure 2.

Mechanism of atrioventricular re-entry tachycardias (AVRT). The right and left atria (RA/LA) and ventricles (RV/LV) are normally electrically isolated by the fibrous rings that form the mitral and tricuspid annulus (grey line), with the only connection being the atrioventricular (AV) node. If a patient has an accessory connection (acc pathway) then the requirements for a re-entry circuit (grey arrows) are fulfilled; where the mitral/tricuspid annuli form fixed conduction block and the AV node, accessory pathway and tissue of the atria and ventricles form the re-entry circuit.