Electrophysiologic Characteristics And Radiofrequency Catheter Ablation Of Focal Atrial Tachycardia In Atrial Septum And Nearby Region

Objective Focal atrial tachycardias (FATs) originating from atrial septum have notbeen well reported yet. The study is aimed to investigate the electrophysiologicalcharacteristics and radiofrequency catheter ablation (RFCA) in patients with FATsoriginating from atrial septum and nearby region.Methods Among the227consecutive patients (pts) with FATs,77pts (33.9%)(52females, mean age56years) with FATs arising near the region of anterior atrial septum(AAS) were studied. The surface electrocardiogram features of FATs were analyzed andactivation mapping was performed during FATs to identify the earliest activation site in theatrial septum and its adjacent tissues. Radiofrequency catheter ablation was usuallydelivered at the earliest activation site. However, if activation time in right AAS (RAAS) and non coronary cusp(NCC) was similar, the initial ablation in NCC was preferred.Results In the77pts,81AAS-FATs were induced.1pt had2FATs eliminated in NCCand MAAJ.3pts all had2ATs eliminated in AAS and anterior atrial septum (PAS). In the47pts,48AAS-FATs were induced. FATs were successfully ablated in45of47pts or46of48FATs. Ablation failed in2pts. The rest46FATs were eliminated in RAS in8pts, inNCC in35pts and in MAAJ in3pts, including1pt whose2FATs were eliminatedseparately in the NCC and MAAJ. In the14pts who underwent initial ablation in RAAS,5pts had a successful ablation,9pts failed (7pts had a successful ablation in NCC,1pthad a successful ablation in MAAJ,1pt failed while ablation in RAAS only). In the33ptswho underwent initial ablation in NCC,28pts had a success in the NCC,3pts failedwhose FATs were eventually ablated in RAAS,1pt had a successful ablation in MAAJ,and1pt failed. In1pt who underwent initial ablation in LCC failed and had a successfulablation in MAAJ. Successful ablation was achieved in all the33patients in PAS. FATswere eliminated by RFCA in right PAS (RPAS) in20patients, coronary sinus (CS) ostiumor proximal CS in7patients, middle cardiac vein (MCV) in2patients, left PAS (LPAS) in4patients. During a follow-up of4months to8years，all were free of FAT except3patients have achieved the success after the second catheter ablation.The P’ wave duration during FAT was significantly shorter than the P wave duringsinus rhythm(78.4±16.9ms vs113.3±15.7ms，P<0.05).The P’ wave morphologies of FATsoriginating from RAAS and NCC were always negative in lead I、aVL, negative/positivein lead V1and with no characteristic in inferior leads. The P’ wave morphologies of FAToriginating from the MAAJ in aVL were always negative. The P’ wave morphologies ofPAS-ATs were characteristic for nearly isoelectric in lead I, deeply negative in all inferiorleads, positive in lead aVR and aVL, negative in lead V3-V5.The activation sequence in the coronary sinus was from the proximal to the distal,was present in all the cases.Activation mapping in the right atrium showed that the relativeearlier atrial activation was located at the His bundle region of AAS-FAT. The arliest atrialactivation preceded the surface P wave by37.9±17.3s. But activation mapping in the right atrium of PAS-AT showed that the site with earlier atrial activation was located close tothe CS. The earliest atrial activation time at the target sites preceded the onset of surface P’wave by34.4±18.0ms. Junctional rhythm beats presented in13patients during ablation.Conclusion FAT originating from anterior septal atria had narrow P’ wave. Themorphology of P’ wave is characteristic, especially the P’ wave of PAS-AT. Theactivation sequence in the coronary sinus was from the proximal to the distal, was presentin all the cases. Activation mapping in the right atrium and a relative earlier atrialactivation near the His bundle region. The earliest atrial potential in His bundle precededCS favored AAS-FAT, the earliest atrial potential in CS preceded His favored PAS-FAT.NCC is usually a preferential ablation site when P’ wave is positive in lead I and aVLand activation time in RAS and NCC was similar, LCC or MAAJ should be consideredwhen P’ wave is negative in lead aVL. Because of the anatomical complexity of PAS,sometimes mapping and ablation of FAT adjacent to the area were very difficult.Combination of mapping and ablation in RPAS, within the CS and its branch, or in LPASwas important to eliminate FAT of PAS in some patients.