Electrophysiological evaluation and ablation of atypical right atrial flutter.

Right atrial reentry which does not critically depend upon activation through the cavotricuspid isthmus is considered to be a subtype of atypical flutter. Diagnosis is dependent upon demonstrating the nonparticipation of the cavotricuspid isthmus. Right atrial free wall atriotomy incisions, the superior vena cava, the inferior vena cava, electrically silent or mute areas, incomplete variants of the posterior intercaval crista terminalis line of block and other functional/anisotropic lines of block form the central barriers around which macroreentry occurs. The length, location and orientation of fixed lines of block such as atriotomy incisions are important determinants of their arrhythmogenicity. Successful catheter ablation depends upon delineating the circuit in order to choose the optimal isthmus for ablation and producing complete block across it.