How to map and ablate atrial scar macroreentrant tachycardia of the right atrium

A special form of macroreentrant atrial tachycardia (MRAT), due to reentran t activation around surgical scars, can occur in patients after cardiac sur gery. Scar MRAT occurs usually after correction of congenital defects, such as atrial or ventricular septal defects, and especially after Mustard, Sen ning or Fontan procedures, but it can occur also after myxoma, valvular or coronary bypass surgery. The simplest form of scar MRAT is reentry around a lateral right atrial sur gical scar. A basic mapping array with multiple simultaneous recordings fro m the anterior and septal right atrium is very useful to make the electroph ysiological diagnosis. A line of double electrograms can be mapped in the c entre of the circuit and a fragmented electrogram usually marks the pivotin g point between the inferior end of the scar and the inferior vena cava (IV C). Extension of the scar toward the closest fixed obstacle, usually the IV C, by means of radiofrequency ablation, can interrupt the tachycardia and m ake it non-inducible. Typical atrial flutter usually coexists with scar MRA T and flutter isthmus ablation is probably indicated in all cases. In patients having undergone baffle atrial surgery it can be impossible to map the whole circuit and entrainment-mapping is helpful to localize critic al isthmuses in the circuit. After the Fontan operation the right atrium ca n be severely dilated and scarred, and multiple, complex reentry circuits c an be found. Left atrial MRAT based on large areas of scar has been describ ed, but there is still too little experience with these to propose general rules for diagnosis and management. (Europace 2000; 2: 193-200) (C) 2000 Th e European Society of Cardiology.