Effects of Two Different Catheter Ablation Techniques on Spectral Characteristics of Atrial Fibrillation

ObjectivesThe aim of this study was to determine the effects of circumferential pulmonary vein ablation (CPVA) and electrogram-guided ablation (EGA) on the spectral characteristics of atrial fibrillation (AF) and the relationship between changes in dominant frequency (DF) and clinical outcome.BackgroundCircumferential pulmonary vein ablation and EGA have been used to eliminate AF. Spectral analysis may identify high-frequency sources.MethodsIn 84 consecutive patients, CPVA (n = 42) or EGA (n = 42) was performed for paroxysmal (n = 49) or persistent (n = 35) AF. During EGA, complex electrograms were targeted. Lead V1and electrograms from the left atrium and coronary sinus were analyzed to determine the DF of AF before and after ablation.ResultsThe left atrial DF was higher in persistent (5.83 ± 0.86 Hz) than paroxysmal AF (5.33 ± 0.76 Hz, p = 0.03). There was a frequency gradient from the left atrium to the coronary sinus (p = 0.02). Circumferential pulmonary vein ablation and EGA resulted in a similar decrease in DF (18 ± 17% vs. 17 ± 15%, p = 0.8). During a mean follow-up of 9 ± 6 months, the change in DF after CPVA was similar among patients with and without recurrent AF. An acute decrease in DF after EGA was associated with freedom from recurrent AF only in patients with persistent AF (19 ± 14% vs. 3 ± 6%, p = 0.02).ConclusionsBoth CPVA and EGA decrease the DF of AF, consistent with elimination of high-frequency sources. Whereas the efficacy of EGA is associated with a decrease in DF in patients with persistent AF, the efficacy of CPVA is independent of changes in DF. This suggests that CPVA and EGA eliminate different mechanisms in the genesis of persistent AF

Geotechnical characterization and stabilization of muskeg soils using the microbially induced calcite precipitation technique (MICP)

Muskeg is the landform that describes the organic terrain. Muskeg soils are widespread in Canada. They cover around 15% of the Canadian landscape. Their problematic nature is attributed to their high compressibility and low shear strength when subjected to loads due to their high initial void ratio and water content. This study aims to investigate the problematic nature of Muskeg soils and provide a solution for their stabilization. Water and organic contents of Muskeg soils are the two primary index properties, and they are easy and inexpensive to determine. Therefore, many studies in the literature correlate the other index and compressibility with these two simply measured properties. An extensive review of the literature was conducted, and new correlations to determine some index and compressibility properties as a function of the organic and water contents were presented. These new proposed correlations would help the design engineers provide reasonable estimations in the concept design phase for projects that deal with this soil. Extensive laboratory and field testing programs were conducted for Muskeg soil samples retrieved from Bolivar Park, Surrey, British Columbia, Canada, to determine their geotechnical properties. New correlations for determining the maximum shear modulus Gmax as a function of the undrained shear strength Su, measured from the electronic vane shear test, and ball net tip resistance qb-net, measured from the ball penetration test, were demonstrated. Moreover, new correlations for the undrained shear strength Su as a function of the cone tip resistance qnet, measured from the seismic cone penetration test (SCPTu), and ball net tip resistance qb-net, measured from the ball penetration test (BPT), were presented. The excessive settlement of Muskeg soil was treated through the environmentally-friendly technique, the Microbially Induced Calcite Precipitation MICP using the urease active bioslurry approach. The results showed a substantial improvement in the compressibility properties when the bioslurry concentration was 0.4, the bioslurry weight was 10%, and cementation solution volume equals twice the pores' volume. The second round of stabilization was conducted to achieve further improvement by coupling the bioslurry with sand as additives. Further improvement was achieved by adding 10% of sandy soils while keeping the bioslurry concentration at 0.4 Mole/Litre, the bioslurry weight at 10% and cementation solution volume the same as the pores' volume.Applied Science, Faculty ofEngineering, School of (Okanagan)Graduat

Radiofrequency Ablation of a Left Atrial Appendage Tachycardia on ECMO Support

Extracorporeal membrane oxygenation (ECMO) has been utilized in the pediatric population for cardiogenic shock secondary to medically intractable arrhythmias. There is limited experience with cardiac radiofrequency ablation (RFA) on these patients while on ECMO. A 7-year-old girl presented with a tachycardia-mediated cardiomyopathy secondary to a left atrial appendage tachycardia. She suffered a cardiac arrest due to pulseless electrical activity and was placed on ECMO. Due to elevated left atrial pressures and the refractoriness of her arrhythmia to cardioversion and antiarrhythmic therapy, while on ECMO, blade atrial septostomy and radiofrequency ablation were performed. The patient tolerated the procedure well and was successfully decannulated. Her cardiac function normalized within four weeks of the ablation procedure. Twelve months after the procedure, she remains completely well, with no symptoms or tachycardia