ABSTRACT
<p><b>OBJECTIVE</b>To investigate how the intra-cardiac activation was translates into the characterized flutter wave in patients with cavatricuspid isthmus-dependent counter-clockwise atrial flutter (CTI-AFL).</p><p><b>METHODS</b>A total of 15 hospitalized CTI-AFL patients (mean age: (60 ± 14) years old, 1 female) from October 2012 to February 2014 were enrolled in the study. The activation map was re-constructed during AFL rhythm for left atrium and right atrium using 3-dimensional mapping system. The flutter wave in surface electrocardiogram was analyzed in combination with the intra-cardiac activation.</p><p><b>RESULTS</b>The mean left ventricular ejection fraction was (60.8 ± 6.6)%, and the left atrial diameter was (39.0 ± 3.4) mm. The mean tachycardia cycle length was (220 ± 24) ms. The activation map was completed in all cases. In inferior leads, the flutter wave was divided into three parts: slowly downward part, sharp downward part and the terminal positive part. The three parts corresponded to the fixed activation part of the macro-reentry.</p><p><b>CONCLUSION</b>The distinctive flutter wave of CTI-AFL was determined by the unique macro-reentry activation in the right atrium. The activation of left atrium contributes to the downward part of the wave.</p>