Efficacy of isoproterenol in the evaluation of dormant conduction and arrhythmogenic foci identification in atrial fibrillation ablation.

BACKGROUND: Catheter ablation for atrial fibrillation (AF) is an established therapy. However, postoperative recurrence is a serious issue caused by the reconduction of the isolated pulmonary veins (PV) and the onset of non-PV foci. The objectives of this study were to elucidate dormant conduction, confirm PV arrhythmia substrate, induce non-PV foci after PV isolation, and assess the acute efficacy of high dose isoproterenol (ISP) when administered in addition to adenosine. METHODS: The study consisted of 100 patients with drug-refractory AF (paroxysmal and persistent) who underwent ablation therapy (either radio-frequency or cryoballoon ablation) as the first-line of therapy at our hospital. All patients first underwent PV isolation (PVI) and were administered adenosine followed by ISP (6 µg × 5 min). The effects were observed, and the therapeutic strategy was evaluated. RESULTS: Persistent dormant conduction due to ISP administration was observed in 13 patients. In over half of the patients, arrhythmia substrates were identified in the PV. Ten patients presented with persistent PV firing. The ablation of non-PV foci was additionally performed in 23 patients. CONCLUSIONS: We found that dormant conduction, as a result of ISP administration, is persistent and ISP is useful when performing an ablation. In addition, ISP administration is useful for the identification of PV arrhythmia substrates and induction of non-PV foci. However, the effectiveness of ISP may be partially due to the complementary effect of adenosine, and, therefore, a combination of the two drugs seems preferable.

Comparison of Anti-factor Xa Activity Among Three Different Factor Xa Inhibitors in Non-valvular Atrial Fibrillation Patients with Renal Impairment.

BACKGROUND: Factor-Xa inhibitors (FXaIs) are widely used for the treatment of non-valvular atrial fibrillation (NVAF). Although we have previously reported the distribution of the anti-factor Xa activity (AXA) values of three different FXaIs in NVAF patients, the differences in the distribution of AXA values among the different FXaIs in patients with renal impairment (RI) have not been fully elucidated. METHODS: Trough and peak AXA values were measured in 94 patients taking rivaroxaban, 124 patients taking apixaban, and 66 patients taking edoxaban. Of them, we identified 26 patients with moderate RI [creatinine clearance (CrCl) 30-49 mL/min] and 17 patients with severe RI (CrCl 15-29 mL/min) in the rivaroxaban cohort, 37 patients with moderate RI and 17 patients with severe RI in the apixaban cohort, and 21 patients with moderate RI and 9 patients with severe RI in the edoxaban cohort. AXA values were measured using chromogenic AXA assays. Both trough and peak AXA values were compared between patients with moderate RI and those with severe RI in each cohort, and differences in the peak-to-trough ratio among the different drugs were assessed. RESULTS: In the rivaroxaban cohort, the peak AXA value was significantly higher in patients with severe RI than in those with moderate RI. In the apixaban cohort, neither the trough nor peak AXA values significantly differed between patients with moderate RI and those with severe RI. In the edoxaban cohort, the trough AXA value was significantly higher in patients with severe RI than in those with moderate RI, and peak AXA tended to be higher in patients with severe RI. The peak-to-trough ratio of AXA values was significantly lower in patients taking apixaban than in those taking rivaroxaban and edoxaban. CONCLUSION: Among Japanese NVAF patients with RI, the peak or trough AXA values were higher in patients with severe RI than in those with moderate RI when taking rivaroxaban and edoxaban, whereas both the peak and trough AXA values were similar between patients with severe RI and those with moderate RI when taking apixaban. The peak-to-trough ratio of AXA values was the lowest in patients taking apixaban.