| Background:Cavotricuspid isthmus(CTI) dependent right atrial flutter may ensue after circumferential pulmonary vein electrical isolation(CPVI) of atrial fibrillation (AF).The isolation of a significant mass of left atrial myocardia may have some influence on the left atrial activation pattern and the flutter wave(F wave) of body surface electrocardiogram(bsECG),but little is known about it.By analyzing the characteristics of left atrial activation pattern and F wave of bsECG during CTI dependent flutter,it perhaps helps to recognize it rapidly.Methods:Under the guidance of the CartoXP-three dimensional mapping system (Biosense-Webster),the right and left ipsilateral pulmonary veins were circumferentially ablated at the antrum level,and after that the residual conductions (gap) between left atrium and pulmonary vein were eliminated with the help of circular mapping electrode(Lasso) to achieve full electrical pulmonary vein isolation. If persistent AF was not converted to sinus rhythm or regular atrial flutter,linear ablations were performed between the two ablation rings,or between left inferior pulmonary vein and mitral annulus,and,if needed,complex fractionated atrial electrograms(CFAEs) were also targeted.Once atrial flutter occurred spontaneously, or was induced by incremental atrial pacing or programmed atrial extrastimulus,three dimensional mapping of both atria accompanied by entrainment mapping was accomplished.If CTI dependent atrial flutter was validated,the following data were analyzed:the activation sequence and duration of the left atrium;the F wave's morphology and duration at inferior leads(Ⅱ,Ⅲ,and aVF) and precordial lead(V1) on bsECG;the existence of isoelectrics;and the corresponding relationship between F wave and endocardial atrial depolarization.Results:Twenty patients were demonstrated to have CTI dependent atrial flutters after CPVI of AF,including thirteen male and seven female patients,averaging 56.9±10.4 years old.The mean cycle length(CL) was 242.1±33.2ms,and the left atrial activation duration was 100.3±20.5ms,accounting for 41.4%CL.The earliest endocardial activation sites in left atrium were located at the coronary sinus ostium (19 patients) or fossa ovalis(1 patient),while the latest situated at left atrial appendage or roof.In the three dimensional electroanatomical activation map,it was manifested as simultaneous activation of the left atrial septum and free wall,and collision of activation front waves at the left atrial roof.The F wave morphology on leadsⅡ,Ⅲand aVF appears to be negative,negative-positive biphasic,positive or isoelectric,its duration averaging 109.3±30.0ms(accounting for 45.1%CL);and the counterpart on lead V1 shows to be positive or isoelectric,averaging 61.3±1.2ms (accounting for 25.3%CL),shorter than inferior leads with 48ms.Isoelectric interval is apparent between F waves in bsECG,especially in lead V1.The local activation timing of right atrial isthmus corresponds to the isoelectric after F wave,and the activation timing of CSO is compatible with the onset of F wave,while the latest activation timing in the left atrium is consistent with the midpoint of F wave.Conclusion:The F wave of CTI dependent right atrial flutter on the bsECG after PVI of AF becomes atypical,and apparent isoelectric between F waves emerges.The left atrial activation time is less than fifty percent of CL.And the activation timing of CSO is compatible with the onset of F wave.Recognizing the above characteristics will guide us to perform right atrial activation and entrainment mapping on purpose, and then identify rapidly the typical atrial flutter.
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