Cause of very late recurrence of atrial fibrillation or flutter after catheter ablation for atrial fibrillation

The major mechanism underlying the early recurrence of atrial fibrillation (AF) after ablation is mainly reconnection of the isolated pulmonary vein (PV); however, the mechanism responsible for very late recurrence (VLR) has not been fully elucidated. The purpose of the present study was to investigate the mechanism underlying VLR. The study population included 150 consecutive patients with AF who underwent a second session of catheter ablation because of recurrence. We divided them into 2 groups according to the point of initial AF recurrence: the late recurrence group (LR group, initial recurrence 3 to 12 months after ablation, n = 124) and the VLR group (initial recurrence >12 months after ablation, n = 26). We identified PVs with ectopic foci (trigger PVs) in the first procedure and checked their electrical reconnection in the second procedure. The prevalence of PV reconnection and trigger PV reconnection were significantly lower in the VLR group than in LR group (LR vs VLR, 90% vs 69% and 48% vs 27%, p = 0.007 and p = 0.045, respectively). In the VLR group, left ventricular systolic and diastolic function were significantly worse than in the LR group, and more patients in the VLR group required non-PV trigger ablation in the second session than did those in the LR group (30% vs 54%, p = 0.034). In conclusion, electrical PV reconnection contributed less to VLR than to LR. Progression of the AF substrate might be an important mechanism responsible for VLR.

Preprocedural ventricular rate predicts subsequent sick sinus syndrome after ablation for long-standing persistent atrial fibrillation

BACKGROUND

Concealed sick sinus syndrome may become manifest after restoration of sinus rhythm by ablation in patients with long-standing persistent atrial fibrillation (AF). The purpose of this study was to investigate the association between the preprocedural ventricular rate during AF and sinus node function in patients with long-standing persistent AF.

METHODS

Consecutive patients (n = 102) who underwent ablation for long-standing persistent AF were enrolled. We measured the ventricular rate during AF before ablation in the absence of antiarrhythmic drugs. Sinus node function was assessed by electrophysiological study and serial Holter recordings after ablation.

RESULTS

Patients in the lowest quartile of ventricular rate during AF had longer corrected sinus node recovery time (1.06 ± 1.39 seconds) than those in the other quartiles (0.54 ± 0.31 seconds; P = 0.006) and lower mean heart rate on 24-hour Holter recording 3 months after ablation (68 ± 9 beats/min vs 75 ± 10 beats/min, P = 0.01). During a mean follow-up of 23 ± 10 months, sick sinus syndrome necessitating permanent pacemaker implantation developed in five (5%) patients, and multivariate analysis revealed that a low ventricular rate during AF rate was an independent risk factor for sick sinus syndrome (odds ratio = 0.90 for a 1 beat/min increase in AF rate, P = 0.04).

CONCLUSIONS

A low preprocedural ventricular rate during AF indicates the existence of sinus node dysfunction after restoration of sinus rhythm by ablation in patients with long-standing persistent AF.

Transient expression of Xpn, an XLMR protein related to neurite extension, during brain development and participation in neurite outgrowth

KIAA2022 has been implicated as a gene responsible for expressing X-linked mental retardation (XLMR) proteins in humans. However, the functional role of KIAA2022 in the human brain remains unclear. Here, we revealed that depletion of Kiaa2022 inhibits neurite outgrowth of PC12 cells, indicating that the gene participates in neurite extension. Thus, we termed Kiaa2022 as an XLMR protein related to neurite extension (Xpn). Using the mouse brain as a model and ontogenetic analysis of Xpn by real-time PCR, we clearly demonstrated that Xpn is expressed transiently during the late embryonic and perinatal stages. In situ hybridization histochemistry further revealed that Xpn-expressing neurons could be categorized ontogenetically into three types. The first type showed transient expression of Xpn during development. The second type maximally expressed Xpn during the late embryonic or perinatal stage. Thereafter, Xpn expression in this type of neuron decreased gradually throughout development. Nevertheless, a significant level of Xpn expression was detected even into adulthood. The third type of neurons initiated expression of Xpn during the embryonic stage, and continued to express the gene throughout the remaining developmental stages. Subsequent immunohistochemical analysis revealed that Xpn was localized to the nucleus and cytoplasm throughout brain development. Our findings indicate that Xpn may participate in neural circuit formation during developmental stages via nuclear and cytoplasmic Xpn. Moreover, disturbances of this neuronal circuit formation may play a role in the pathogenesis of mental retardation.

Trigger-Based Mechanism of the Persistence of Atrial Fibrillation and Its Impact on the Efficacy of Catheter Ablation

Background—

We investigated the possibility that a frequent trigger action might play a role in the development of persistent atrial fibrillation (PeAF) and the presence of a substrate.

Methods and Results—

In 263 consecutive patients who underwent catheter ablation (CA) for PeAF, electric cardioversion was performed at the beginning of the procedure to determine the presence or absence of an immediate recurrence of AF (IRAF). We defined an IRAF as a reproducible AF recurrence within 90 s after restoration of sinus rhythm by electric cardioversion. We performed a mean±SD of 1.3±0.5 sessions of CA, including pulmonary vein isolation and ablation of the premature atrial contractions that triggered the IRAF (IRAF triggers), and observed the patients for 17 (10–27) months. An IRAF was observed in 70 patients (27%), but we could not ablate the IRAF triggers in 16 (23%) of these IRAF patients. The recurrence rate of PeAF was higher in patients with an unsuccessful IRAF trigger ablation than in those with successful IRAF trigger ablation (63% versus 11%; P <0.001). A multivariable analysis also revealed that an unsuccessful IRAF trigger ablation was 1 of the independent predictors of recurrent PeAF (odds ratio, 10.9; 95% CI, 3.4–36.7).

Conclusions—

In the PeAF patients with an IRAF, successful elimination of the IRAF triggers, in addition to pulmonary vein isolation, resulted in a successful CA. These results imply that such triggers play a major role in the AF persistence in these PeAF patients.