Bipolar catheter ablation strategies for outflow tract ventricular arrhythmias refractory to unipolar ablation.

INTRODUCTION: Conventional unipolar catheter ablation (UA) is generally effective for the treatment of outflow tract ventricular arrhythmias (OT-VAs). However, deep foci refractory to UA remains a clinical challenge. The present study evaluated the efficacy and safety of bipolar ablation (BA) in the treatment of OT-VAs refractory to UA. METHODS: A total of 1022 consecutive patients with antiarrhythmic drugs resistant OT-VAs were screened for inclusion in this study, from 1643 VAs cases who underwent catheter ablation in two centers from October 2014 to May 2019. BA was performed after failed sequential UA. The pair of catheters used for BA was positioned on opposing surfaces of the earliest activation (EA) sites or on adjacent anatomical structures. RESULTS: Twelve patients (seven males, mean age 33.3 ± 16.2 years) who met the inclusion criteria were recruited: one patient suffered sustained monomorphic ventricular tachycardia (VT), six patients had frequent premature ventricular contractions (PVCs), and nonsustained VT (NSVT), and five patients had PVCs only. The 24-hPVC/NSVT burden was 36.9 ± 21.7%. The mean distance between two ablation catheters during BA was 11.1 ± 4.3 mm (range 6.5-23.9 mm). The "rS" morphology of the unipolar electrogram was recorded simultaneously in both EA regions in seven cases (58.3%). Acute eradication of VAs was obtained in 10 (83.3%) cases. At a median follow-up of 58 months, 10 patients (83.3%) remained free from VAs. CONCLUSION: BA was highly effective and safe for the treatment of OT-VAs refractory to UA.

Kinetics of chromium (VI) reduction and phenol biodegradation by Pseudomonas sp. JF122.

Kinetics of chromium (VI) reduction and phenol biodegradation by a pure culture of Pseudomonas sp. JF122 was studied. High inoculum (volume) increased both chromium (VI) reduction and phenol biodegradation velocity, which are ascribable to shorter acclimation period requirement for cell growth. Haldane's kinetics model adequately described the substrate kinetics with kinetic constants µ(max1) =0.113 h⁻¹, K(s1) = 0.4009 mM, K(i1) =5.165 mM for chromium (VI) reduction and µ(max2) =0.3081 h⁻¹, K(s2) =7.411 mM K(i2) =2.511 mM for phenol biodegradation. Further, the growth yield for phenol biodegradation and chromium (VI) reduction were 30.6 mg cell/mmol phenol and 8880.2mg cell/mmol Cr (VI), respectively.