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This case is a reminder not to overlook rare causes of electrolyte shifts, which may cause reversible changes in pacemaker pacing thresholds.

Purpose: Recovery of pulmonary vein (PV) conduction is a common mechanism of atrial fibrillation recurrence after PV isolation (PVI), underscoring the need for durable lesion formation. We aimed to evaluate the utility of an automated lesion annotation algorithm (ALAA) on acute isolation rates and resulting lesion characteristics., Methods: Fifty patients underwent PVI using a contact force (CF) sensing catheter and ALAA. Single antral circles around ipsilateral PVs were performed with ALAA-1 settings including catheter stability (range of motion ≤2 mm, duration >10 s). Target CF was 10-20 g but not part of ALAA-1 settings. If PV conduction persisted after circle completion, force over time was added to automated settings (ALAA-2). Emerging gaps were subsequently ablated, followed by re-assessment for PVI., Results: ALAA-1 isolated 70 % of the left and 78 % of the right PVs using 756.3 ± 212.3 s (left) and 737.1 ± 145.9 s (right) of energy delivery. ALAA-2 settings identified 29 gaps in previously unisolated PVs, closure significantly increased isolation rates to 88 % of the left and 96 % of the right PVs with additional 325.4 ± 354.1 s (left) and 266.8 ± 279.5 s (right) of energy delivery (p = 0.001). Lesion characteristics significantly differed between ALAA-1 (n = 3521 lesions) and ALAA-2 (n = 3037 lesions) settings, and between isolated and non-isolated PV segments, particularly with respect to CF. Interlesion distances with ALAA-2 were significantly longer in the left superior, left superior-anterior, and right superior-posterior segments when compared to ALAA-1., Conclusions: Settings of an ALAA affect lesion characteristics reveal areas of insufficient lesion formation and influence acute effectiveness of PVI. Combination of CF and stability shows superior performance over stability alone.

Aims: Lesion formation during catheter ablation crucially depends on catheter-tissue contact. We sought to evaluate the impact of anatomical characteristics of the left atrium (LA) and the pulmonary veins (PVs) on contact force (CF) measurements., Methods and Results: An anatomical map of the LA was obtained in 25 patients prior to catheter ablation of atrial fibrillation. Contact force (operator blinded) and local bipolar electrogram amplitudes (EGM) were measured in eight pre-defined segments around the PVs. After unblinding, points with low CF (≤5 g) were corrected to CF >5 g, and the distance between points was measured. In a pre-procedural computed tomography of the heart, LA volume as well as sizes and circumferences of the PV ostia were measured and correlated to CF measurements. Four hundred and twenty-six points in eight pre-defined LA locations were assessed. Low CF (<5 g) was found in 25.0% (43.5%) of points superior, 33.3% (66.7%) anterior, 32.1% (44.4%) inferior, and 15.5% (15.9%) posterior to the right (left) PVs. The mean distance after correction was 5.8 ± 3.4 mm. Local bipolar electrogram amplitudes between low- and high-CF points did not differ (1.21 ± 1.54 vs. 1.13 ± 1.3 mV, P = ns). The mean CF at the left PVs was significantly lower than at the right PVs (7.91 ± 3.74 vs. 13.95 ± 6.34 g, P < 0.001), with the lowest CF anterior to the left PVs (5.2 ± 3.6 g). Contact force measurements did not correlate to LA volume, size, and circumference of the PVs., Conclusion: Contact force during LA mapping significantly differs according to the location within the LA. These differences are independent of LA volume and anatomy of the PV ostia., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2015. For permissions please email: journals.permissions@oup.com.)

Purpose: Concerning rates of pulmonary vein (PV) stenosis were reported following PV isolation (PVI) with a circular pulmonary vein ablation catheter (PVAC). As this may depend on intraprocedural imaging, we evaluated the incidence of PV stenosis in patients undergoing PVAC-PVI with continuous surveillance by intracardiac echocardiography (ICE)., Methods: Multi-slice computed tomography was performed before and 3 months after PVAC-PVI with continuous ICE surveillance in 30 patients (37 % male, 65 ± 9 years). PV areas at two levels (ostial and 1 cm distally) and left atrial (LA) volumes were measured. PV area/LA volume ratio was calculated to correct for reverse LA remodelling. PV stenosis was classified as mild (25-50 %), moderate (50-75 %) and severe (> 75 %)., Results: One hundred sixteen veins were isolated with PVAC with additional touch-up ablation in one patient. One patient was excluded from analysis for untriggered CT acquisition. Left atrial volume decreased from 109.1 ± 30.9 cm(3) before to 98.4 ± 34.4 cm(3) after ablation (p < 0.05). Overall, PV areas decreased ostially from 209.0 ± 80.3 mm(2) to 171.2 ± 74.6 mm(2) (p < 0.0001) and distally from 155.2 ± 61.5 mm(2) to 141.0 ± 51.3 mm(2) (p < 0.0001). After adjustment for LA volume reduction, PV area significantly reduced only at the ostial level (p = 0.0069). Mild PV stenosis (ostial/distal) was detected in 17/9 PVs (14.7 %/7.8 %) and moderate PV stenosis in 7/0 PVs (6.0 %/0 %). PV stenosis occurred more often in superior PVs (p = 0.0004). No severe PV stenosis occurred. All patients remained asymptomatic., Conclusions: While the use of ICE does not fully prevent the occurrence of ostial PV stenosis after PVAC-PVI, no significant narrowing in distal PVs was observed. Superior PVs are prone to PV stenosis after PVAC-PVI.