Atrial flutter vector loops derived from the surface ECG: does the plane of the loop correspond anatomically to the macroreentrant circuit?

We hypothesized that if the right atrial circuit during isthmus dependent atrial flutter provides the dominant contribution to the surface electrocardiogram (ECG), the three-dimensional vector loop of the flutter waves would primarily be in a plane approximately parallel to the tricuspid ring. Twenty vectorcardiograms of isthmus dependent atrial flutter derived from 12-lead ECGs of 19 patients recorded prior to radiofrequency ablation were analyzed. The plane of each loop, described by azimuth and elevation angles relative to the frontal plane, was estimated with two methods: 1) plane of maximum loop area and 2) plane of best fit. The plane of maximum loop of the loops had mean azimuth of -58 +/- 37 degrees. and elevation of 15 +/- 15 degrees. The plane of best fit of the loops had mean azimuth of -50 +/- 46 degrees and elevation of 15 +/- 14 degrees. Thus, clinical implications include the potential to predict atrial flutter mechanisms prior to intracardiac mapping.