[Approximation of mathematical scanning simulation data and clinical results f radiofrequency ablation of perimitral atrial flutter. Condition of existence of perimitral atrial flutter].

AIM: 1) to create Perimitral Atrial Flutter (PMAFL) model and estimate theoretical probability of elimination of perimital reetntry using left atrial geometry two-dimensional mathematical modeling and ablative formatting; 2) to compare clinical results of PMAFL ablation by means of mitral vs inferioseptal isthmus ablation and mathematical modeling data.

MATERIAL AND METHODS: Clinical phase. Study was conducted on 24 pts (6 women, 57.1 ± 9.3 years) with PMAFL. Initially RF-lesions delivered in LA in the MI (endocardial approach to MI). Distal CS roof ablation (epicardial approach to MI) was a second step. As a third step linear RF-lessions of the inferioseptal isthmus (ISI)- from right pulmonary vein ostium to mitral annulus was performed (endocardial approach to ISI). As a fourth step RF-applications applied inside the proximal CS roof (epicardial approach to ISI). Mathematical phase. As the first step numeric reconstruction of the autowave process in excitable tissues of the left atrium was performed. Fitzhugh-Nagumo equation was used for simulation to enabled us to take into account the electrical inhomogeneity of the atria (pulmonary vein ostia). A special scanning method was used for calculating characteristics of autowave processes in a two-dimensional mathematical model of the atrium. As the second step simulation of linear ablation formatting which linked PV ostia and active medium boundaries (corresponding to mitral and inferioseptal isthmus ablation lines) was performed.

RESULTS: Clinical phase. Left MI endocardial RFA terminated PMAFL in 6 cases, increased CL without changes of atrial hierarchy activation in 2 cases, and transformed PMAFL to AFib in 2 cases. Distal CS ablation terminated PMAFL in 2 pts. Endocardial ISI ablation of associated with SR restoration in 2 cases and increasing of PMAFL CL in 5 cases. Proximal CS-roof ablation terminated PMAFL in 12 pts. Follow up was 26.7 ± 12.4 mos. Endocardial and epicardial MI approach terminated PMAFL in 8 pts (36%). RFA of endocardial 39nd epicardial aspects of the ISI restored SR in 12 pts (64%) (p< 0.05). MATHEMATICAL PHASE: There are three definite conditions of PMAFL existing: 1) Initial autowave spreading between superior PV and boundary of medium (corresponding to patent conduction between superior PV ostia and mitral annulus); 2) Non-active medium existing between four PV ostia (corresponding to PV isolation after index ablation); 3) Refractory characteristics of medium (corresponding to posterior wall of LA) and medium between PV ostia and boundaries (corresponding to isthmus zones) have to differ each other. The linear ablation patterns (from PV ostia to boundary of medium) suppress PAMFL in two-dimensional mathematical modeling of the left atrium.

CONCLUSION: There are definite conditions of PAMFL simulation by means autowave processing in a 2-D active medium using scanning algorithm. Those conditions may consistent with certain EP characteristics of LA after index ablation clinical results of PAMFL ablation.