3-DIMENSIONAL MAPPING OF THE COMMON ATRIAL-FLUTTER CIRCUIT IN THE RIGHT ATRIUM

Background The full circuit of common atrial flutter using conventiona l methods of sequential or multielectrode activation mapping is not co mpletely understood. Methods and Results We performed three-dimensiona l right atrial endocardial activation mapping during common counterclo ckwise atrial flutter in 17 patients (16 men, 1 woman; mean age, 53+/- 11 years) by using the Cordis-Biosense EP Navigation system and assess ed the distribution of estimated conduction velocities and double and fractionated potentials. ECG flutter wave morphologies were compared w ith activation patterns. Points (91+/-29) were sequentially acquired c overing 88+/-11% of the flutter cycle length of 239+/-22 ms. A wide an d variable posterior zone of double and fractionated potentials coinci ded with blocking and colliding wave fronts and formed the posterior l imit of the circuit. A progressively widening septal (sep) wave front ascending from just beyond the coronary sinus ostium, passed cranially as a broad front anterior to the superior vena cava (SVC) in 14 patie nts, whereas fusion around the SVC formed the superior (sup) limb of t he circuit in 3. Bounded anteriorly by the tricuspid valve, the wave f ront descended down the lateral (lat) aspect of the right atrium befor e completing the circuit in all cases through the inferior vena cava-t ricuspid annulus isthmus. The estimated conduction velocity in the med ial isthmus (0.6+/-0.3 m/s) was lower than in the other limbs of the c ircuit (sup=1+/-0.5 m/s, lat=1+/-0.5 m/s, sep=0.9+/-0.4 m/s, P=.05). D ouble and fractionated potentials were constant and more prevalent in the posterior right atrium. ECG flutter wave morphology did not correl ate with three-dimensional activation maps. Conclusions Interindividua l variations occur in the right atrial circuit of common atrial flutte r, with constant activation through the cavotricuspid isthmus. A varia ble zone of block forms the posterior limit. Fusion around the SVC can occur, and ascending medial septal activation does not follow a consi stent pattern.