Characterisation of atrial tachycardia in patients after Fontan surgery using a non-contact mapping system

Atrial tachycardia (AT) is a major late complication of surgical procedures used to palliate congenital heart disease. Surgical scars/unusual anatomy/prosthetic materials create the substrate for complex arrhythmias which are difficult to map using conventional techniques. We have used a non-contact multielectrode array (MEA) to construct isopotential maps of the systemic venous return ("atrial") chamber in 3pts with AT after Fontan-type surgery. The MEA allows reconstruction of 3360 unipolar electrograms which are superimposed on a 3-dimensional model of the endocardium. The endocardial geometry and low amplitude electrical activity in the diseased atrial myocardium of these "atrial" chambers challenge the accuracy of this mapping technology. Nevertheless, AT reentry circuits could be identified in 2 pts and an ectopic atrial focus in 1. The isopotential maps constructed could be correlated with known features of the "Fontan atrial" anatomy, including activation fronts determined by atriotomy scars, cardiac structures or "patch" tissue. Guided by these maps, RF was used to create linear or focal lesions to abolish AT in 2pts (1 requiring 2 procedures). In 1pt AT was slowed and then terminated by a series of RF applications. However, the AT remained inducible (with a much longer cycle and rendered sensitive to termination by adenosine. Conclusion: Non-contact mapping of the systemic venous atrium late after Fontan surgery identifies mechanisms of AT. It may be superior to conventional mapping techniques and allow catheter ablation of these complex arrhythmias.