Titration of the RF application time to the maximal EGM attenuation based on the ME recordings represents atrial lesion maturation and deep ventricular lesions. Prolonging the RF application results in greater extracardiac injury and char formation without increasing lesion size.
Impedance rise of 500 Ω at <90 seconds with freeze time of 90 seconds resulted in 100% PVI. Impedance measurements from the nose of the balloon is a direct measure of ice formation on the balloon. It provides real-time feedback on the quality of the ablation and defines the cryoapplication termination time based on ice formation, limiting ice expansion to extracardiac tissues.
Plant derivatives offer a novel and natural source of therapeutics. The desert plant Achillea fragrantissima (Forssk) Sch. Bip (Af) is characterized by protective antioxidative and anti-inflammatory properties. Here, we examined the effect of two Af-derived phytochemicals on learning and memory, amyloid-β protein precursor (AβPP) metabolism, and tau phosphorylation in the familial Alzheimer’s disease-linked APPswe/PS1∆E9 mouse model. We observed that mice that were injected with the phytochemicals showed a trend of improvement, albeit statistically insignificant, in the Novel Object Recognition task. However, we did not observe improvement in contextual fear conditioning, suggesting that the benefits of treatment may be either indirect or task-specific. In addition, we observed an increase in the full-length form of AβPP in the brains of mice treated with Af–derived phytochemicals. Interestingly, both in vivo and in vitro, there was no change in levels of soluble Aβ, oligomeric Aβ, or the carboxyl terminus fragments of AβPP (APP-CTFs), suggesting that the increase in full length AβPP does not exacerbate AβPP pathology, but may stabilize the full-length form of the molecule. Together, our data suggest that phytochemicals present in Af may have a modest positive impact on the progression of Alzheimer’s disease.
BackgroundA direct indicator of effective pulmonary vein isolation (PVI) based on early ice formation is presently lacking.ObjectiveThe initial impedance rise within 30 to 60 seconds (sec) of single cryoablation relating to ice on the distal surface of the cryoballoon could; predict effective PVI with early termination, the need for prolonging the cryoablation, or failure to achieve effective ablation.MethodsImpedance measurements were taken between two ring electrodes, at the anterior balloon surface and at the shaft behind the balloon. Ice covering the anterior ring leads to impedance rise. Single cryoablation (eight animals, 37 veins) was applied for 90 to 180 sec. Cryoapplication was terminated if the impedance reached ≥500 Ω. Impedance levels at ≤60 sec of cryoablation were divided into three groups based on the characteristics of the impedance rise. PVI was confirmed acutely and at 45 ± 9 days recovery by electrophysiology mapping and histopathology.ResultsAt 60 sec of freezing, an impedance rise of 34.1 ± 15.2 Ω (13‐50 Ω) and slope of the impedance rise (measured during 15‐30 sec of cryoapplication) less than 1 Ω/sec resulted in failed PVI. An impedance rise of 104.4 ± 31.5 Ω (76‐159 Ω) and slope of 2 Ω/sec resulted in 100% PVIs. An impedance rise of 130.9 ± 137.8 Ω (40‐590 Ω) and slope of 10 Ω/sec resulted in 100% PVIs with early termination at 90 sec.ConclusionThe efficacy of single cryoablation can be defined within 30 to 60 sec based on ice impedance. Three unique impedance profiles described in this investigation are associated with the uniformity and thickness of the ice buildup on the anterior surface of the balloon. One cryoablation with an adequate impedance rise is needed for successful outcomes.
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