Pulmonary vein isolation has become a cornerstone treatment for catheter ablation of atrial fibrillation (AF). Recent reports show that additional ablation targeting low-voltage zones reduces AF recurrence. However, the pre-procedural predictors of low-voltage zones remain elusive. We retrospectively enrolled 359 patients (mean age 63.7 ± 10.8 years; 73 females; and 149 had persistent atrial fibrillation) who underwent catheter ablation for AF and left atrial (LA) voltage mapping during sinus rhythm or atrial pacing. Low-voltage zones were defined as area of > 5 cm2 with a bipolar electrogram amplitude of < 0.50 mV. Overall, 51 (14.2%) patients had low-voltage zones. Patients with low-voltage zones were older (67.9 ± 9.9 vs. 63.0 ± 10.8 years; P = 0.003), predominantly female (33.3% vs. 18.2%; P = 0.013), had higher prevalence of dilated cardiomyopathy (DCM) (11.8% vs. 1.6%; P = 0.002) and hypertrophic cardiomyopathy (HCM) (9.8% vs. 2.6%; P = 0.025), and had larger LA volumes (153.6 ± 46.4 vs. 117.7 ± 67.8 mL; P < 0.001) than those without low-voltage zones. Multivariate logistic regression analysis revealed that age (OR 1.060; 95% CI 1.022–1.101, P = 0.002), female sex (OR 2.978; 95% CI 1.340–6.615, P = 0.007), DCM (OR 8.341; 95% CI 1.381–50.372, P = 0.021), HCM (OR 5.044; 95% CI 1.314–19.363, P = 0.018), persistent AF (OR 4.188; 95% CI 1.928–9.100, P < 0.001), and larger LA volume (OR 3.215; 95% CI 1.378–7.502, P = 0.007) were independently associated with the presence of low-voltage zones. Patient age, female sex, DCM, HCM, persistent AF and larger LA volume may predict the presence of low-voltage zones and could be useful in selecting the appropriate ablation strategy for AF.

A 78-year-old male was admitted to our hospital due to frequent palpitation. His electrocardiogram (ECG) presented regular narrow QRS tachycardia with 170 bpm, and catheter ablation was planned. During electroanatomical mapping of the right atrium (RA) with a multiloop mapping catheter, the catheter head was entrapped nearby the ostium of inferior vena cava. Rotation and traction of the catheter failed to detach the catheter head from the RA wall. Exfoliation of connective tissue twined around catheter tip by forceps, which were designed for endomyocardial biopsy, succeeded to retract and remove the catheter. Postprocedural echocardiography and pathologic examination proved the existence of Chiari's network. The handling of complex catheters in the RA has a potential risk of entrapment with Chiari's network.

Introduction: Phrenic nerve (PN) injury is a well-known complication of cryoballoon ablation (CBA) for pulmonary vein (PV) isolation in patients with atrial fibrillation.However, it is still insufficient to practically predict phrenic nerve injury (PNI) before freezing. We hypothesized that phrenic nerve capture (PNC) with phrenic nerve orifice pacing (PVOP) might be a surrogate sign of the close proximity of the PN, and that might predict PNI and changes in the compound motor action potential (CMAP) amplitude.Methods: Seventy patients (60 ± 12 years, male 80%, paroxysmal 56%) underwent PVOP with a 20-electrode ring catheter before the CBA. The clinical outcome was the occurrence of transient and persistent PNI. In addition, the PV position and pacing threshold during PNC with PVOP, and changes in the CMAP amplitude were recorded. We compared these measurements between patients with and without PNC (PNC/non-PNC group) with PVOP.Results: PNC with PVOP occurred in 39 (56%) patients and was localized only to the right superior PV. Transient PNI occurred in seven (10%) patients and permanent in none. The CMAP amplitude decreased significantly more in the PNC group (PNC 33% vs non-PNC 16%, P = .027). PNC group had a higher risk of the composite outcome of transient PNI or ≥30% decrease in the CMAP amplitude (PNC 54% vs non-PNC 13%; P < .001). Conclusions: This PVOP technique could be feasible and contribute to predicting transient PNI and CMAP amplitude reductions before cryoapplications. Further studies are necessary to elucidate the additional efficacy of PVOP over CMAP monitoring alone. K E Y W O R D S atrial fibrillation, compound motor action potential, cryoballoon, phrenic nerve injury, pulmonary vein orifice pacing

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T he early repolarization pattern (ERP) is defined as notches or slurs in the terminal portion of the QRS complex with an associated elevation of the ST segment 1,2 and has been considered to be a benign electrocardiographic finding. 3,4 Meanwhile, notching or slurring of the terminal portion of the QRS complex has been shown to be a clue for sudden cardiac death from ventricular fibrillation (VF) from idiopathic causes (also known as idiopathic VF [IVF]). 5-7 Notching and slurring are now referred to as J waves, which are categorized as either J-wave syndrome or early repolarization syndrome. 8-10 J waves have been reproduced in animal experiments, and their dynamicity has been studied both experimentally 11-13 and clinically. 11-13 A pause-dependent augmentation of the J-wave amplitude is one of the striking features of J waves in IVF patients, 5,11-14 and mechanistically, J waves are related to transient outward currents (Ito), which are augmented at slower rates. 11-13 Because J waves are augmented at a slower rate, it is natural to expect that J waves are attenuated at higher rates, although this has rarely been confirmed in the literature. 11-13 On the basis of the gap in earlier reports, 11,15 we hereby present the results of atrial pacing in IVF patients to show the tachycardia-dependent attenuation of J waves. The results from IVF patients were compared with those from non-IVF subjects. Methods IVF Patients Among 48 patients diagnosed with J-wave-associated IVF, J waves were studied in 8 patients during atrial pacing. In 1 patient, Original Article Background-To know the underlying mechanisms of J waves, the response to atrial pacing was studied in patients with idiopathic ventricular fibrillation (IVF) and patients with non-IVF. Methods and Results-In 8 patients with IVF, the J-wave amplitude was measured before, during, and after atrial pacing. All patients had episodes of ventricular fibrillation without structural heart disease. The responses of J waves were compared with those of the 17 non-IVF control subjects who revealed J waves but no history of cardiac arrest and underwent electrophysiological study. The IVF patients were younger than the non-IVF patients (28±10 versus 52±14 years, respectively; P=0.002) and had larger J waves with more extensive distribution. J waves decreased from 0.35±0.26 to 0.22±0.23 mV (P=0.025) when the RR intervals were shortened from 782±88 to 573±162 ms (P=0.001). A decrease (≥0.05 mV) in the J-wave amplitude was observed in 6 of the 8 patients. In addition, 1 patient showed a distinct reduction of J waves in the unipolar epicardial leads. In contrast, J waves were augmented in the 17 non-IVF subjects from 0.27±0.09 to 0.38±0.10 mV (P<0.001): augmented in 9 and unchanged in the 8 subjects. The different response patterns of J waves to rapid pacing suggest different mechanisms: early repolarization in IVF patients and conduction delay in non-IVF patients. Conclusions-The response to atrial pacing was different between the IVF and non-IVF patients, which suggests the p...