4.3 | Mitral isthmus block durability
Previous reports described improved durability and lower arrhythmia recurrence after VOM-EI facilitated mitral isthmus block. Liu et al. stratified 254 patients into three groups: 1) VOM-EI with supplement pulmonary vein isolation with substrate modification; 2) pulmonary vein isolation with substrate modification; and 3) pulmonary vein isolation alone.15 They demonstrated a significant lower atrial arrhythmia recurrence rate in the VOM-EI group in comparison with pulmonary vein isolation with substrate modification or pulmonary vein isolation alone (28.1% vs. 54.7% vs. 43.8%, P = 0.018). Another study by Takigawa et al. reported a better outcome of perimitral flutter treated by VOM-EI than by radiofrequency alone at one year and a reduction of atrial tachycardia recurrence rate of 65% in the VOM-EI group compared to the radiofrequency ablation group.19
The Bordeaux group described mitral isthmus line reconnection in 37.1% of the patients with redo procedures after VOM-EI.13We found a reconnected mitral isthmus line in three out of five patients with recurrent arrhythmia (60%). The gap on the mitral isthmus line was located on the annular side of the mitral isthmus in two out of three patients (66%), where VOM-EI is ineffective and additional radiofrequency ablation is necessary to achieve mitral isthmus block.
Evolution of the low-voltage area induced by VOM-EI during follow-up showed shrinking of the low-voltage area in four out of five patients. Although a meaningful analysis was not possible because of the low number of patients, it is reassuring that the low-voltage area induced by VOM-EI remained stable and did not expand unpredictably during follow-up. Further studies are needed to analyse the correlation between induced low-voltage area and the rate of arrhythmia recurrence after VOM-EI.