Purpose
The optimal radiofrequency (RF) power and lesion duration using contact force (CF) sensing catheters for atrial fibrillation (AF) ablation are unknown. We evaluate 50 W RF power for very ...short durations using CF sensing catheters during AF ablation.
Methods
We evaluated 51 patients with paroxysmal (
n
= 20) or persistent (
n
= 31) AF undergoing initial RF ablation.
Results
A total of 3961 50 W RF lesions were given (average 77.6 ± 19.1/patient) for an average duration of only 11.2 ± 3.7 s. As CF increased from < 10 to > 40 g, the RF application duration decreased from 13.7 ± 4.4 to 8.6 ± 2.5 s (
p
< 0.0005). Impedance drops occurred in all ablations, and for patients in sinus rhythm, there was loss of pacing capture during RF delivery suggesting lesion creation. Only 3% of the ablation lesions were at < 5 g and 1% at > 40 g of force. As CF increased, the force time integral (FTI) increased from 47 ± 24 to 376 ± 102 gs (
p
< 0.0005) and the lesion index (LSI) increased from 4.10 ± 0.51 to 7.63 ± 0.50 (
p
< 0.0005). Both procedure time (101 ± 19.7 min) and total RF energy time (895 ± 258 s) were very short. For paroxysmal AF, the single procedure freedom from AF was 86% at 1 and 2 years. For persistent AF, it was 83% at 1 year and 72% at 2 years. There were no complications.
Conclusions
Short duration 50 W ablations using CF sensing catheters are safe and result in excellent long-term freedom from AF for both paroxysmal and persistent AF with short procedure times and small amounts of total RF energy delivery.
Spectrum sensing for cognitive radio has focused on detection and estimation of aggregate spectra, without regard for latent component identification. Unraveling the constituent power spectra and the ...locations of ambient transmitters can be viewed as the next step towards situational awareness, which can facilitate efficient opportunistic transmission and interference avoidance. This paper focuses on power spectra separation and multiple emitter localization using a network of multi-antenna receivers. A PARAllel FACtor analysis (PARAFAC)-based framework is proposed, which offers an array of attractive features, including identifiability guarantees, ability to work with asynchronous receivers, and low communication overhead. Dealing with corrupt receiver reports due to shadowing or jamming can be a practically important concern in this context, and addressing it requires new theory and algorithms. A robust PARAFAC formulation and a corresponding factorization algorithm are proposed for this purpose, and identifiability of the latent factors is theoretically established for this more challenging setup. In addition to pertinent simulations, real experiments with a software radio prototype are used to demonstrate the effectiveness of the proposed approach.
Circulating microRNAs are biomarkers reported to be stable and translational across species. MicroRNA-122 (miR-122) is a hepatocyte-specific microRNA biomarker for drug-induced liver injury (DILI). ...We developed a single molecule, dynamic chemical labeling (DCL) assay to directly detect miR-122 in blood. The DCL assay specifically measured miR-122 directly from 10 μL of serum or plasma without any extraction steps, with a limit of detection of 1.32 pM that enabled the identification of DILI. Testing of 192 human serum samples showed that DCL accurately identified patients at risk of DILI after acetaminophen overdose (area under ROC curve 0.98 (95% CI; 0.96–1), P < 0.0001). The DCL assay also identified liver injury in rats and dogs. The use of specific captured beads had the additional benefit of stabilizing miR-122 after sample collection, with no signal loss after 14 days at room temperature, in contrast to PCR that showed significant loss of signal. RNA sequencing demonstrated the presence of multiple miR-122 isomiRs in the serum of patients with DILI that were at low concentration or not present in healthy individuals. Sample degradation over time produced more isomiRs, particularly rapidly with DILI. PCR was inaccurate when analyzing miR-122 isomiRs, whereas the DCL assay demonstrated accurate quantification. We conclude that the DCL assay can accurately measure miR-122 to diagnose liver injury in humans and other species and can overcome microRNA stability and isomiR challenges.
Extracellular microRNAs enter kidney cells and modify gene expression. We used a Dicer-hepatocyte-specific microRNA conditional-knock-out (Dicer-CKO) mouse to investigate microRNA transfer from liver ...to kidney.
Dicerflox/flox mice were treated with a Cre recombinase-expressing adenovirus (AAV8) to selectively inhibit hepatocyte microRNA production (Dicer-CKO). Organ microRNA expression was measured in health and following paracetamol toxicity. The functional consequence of hepatic microRNA transfer was determined by measuring the expression and activity of cytochrome P450 2E1 (target of the hepatocellular miR-122), and by measuring the effect of serum extracellular vesicles (ECVs) on proximal tubular cell injury. In humans with liver injury we measured microRNA expression in urinary ECVs. A murine model of myocardial infarction was used as a non-hepatic model of microRNA release.
Dicer-CKO mice demonstrated a decrease in kidney miR-122 in the absence of other microRNA changes. During hepatotoxicity, miR-122 increased in kidney tubular cells; this was abolished in Dicer-CKO mice. Depletion of hepatocyte microRNA increased kidney cytochrome P450 2E1 expression and activity. Serum ECVs from mice with hepatotoxicity increased proximal tubular cell miR-122 and prevented cisplatin toxicity. miR-122 increased in urinary ECVs during human hepatotoxicity. Transfer of microRNA was not restricted to liver injury –miR-499 was released following cardiac injury and correlated with an increase in the kidney.
Physiological transfer of functional microRNA to the kidney is increased by liver injury and this signalling represents a new paradigm for understanding the relationship between liver injury and renal function.
Kidney Research UK, Medical Research Scotland, Medical Research Council.
Pulmonary vein isolation (PVI) ablation is a standard therapy for paroxysmal atrial fibrillation (PAF). Lesion Index (LSI) is a metric to guide radiofrequency (RF) ablation using the TactiCath ...Ablation Catheter, Sensor Enabled with the EnSite Cardiac Mapping System (Abbott).
This study (NCT-03906461) was designed to capture best practices using LSI-guided catheter ablation to treat PAF subjects in a real-world setting.
This prospective single-arm observational study enrolled 143 PAF subjects in the United States, Europe, and Japan undergoing de novo PVI with RF ablation. PVI lesions were assigned to 10 anatomically defined segments. Mean LSIs achieved for all lesions were analyzed. Follow-up was conducted between 3–6 months and 12 months after the procedure.
Pulmonary veins were isolated in all subjects. The mean achieved LSI was 4.9, with lower values in Europe (4.4) and Japan (4.5) than the United States (5.5). First-pass success, defined as no gaps requiring touch-up ablation after 20 minutes post isolation, was achieved in 76.2% of subjects. Use of high LSI (≥5) resulted in shorter procedure, RF, and fluoroscopy times and fewer touch-up ablations compared to low LSI (<5). At 12 months, 99.3% of subjects were free from procedure- or device-related serious adverse events and 95.7% (112/117) (35.0% on antiarrhythmic drugs) were free from recurrence and/or a repeat ablation procedure for atrial fibrillation / atrial flutter / atrial tachycardia.
LSI-guided ablation strategies proved safe and effective despite differences in LSI workflows. Use of high LSI values resulted in shorter procedure, RF, and fluoroscopy times and fewer touch-up ablations compared to low LSI.
Display omitted
Although lesion transmurality is required for durable pulmonary vein isolation, excess ablation is associated with increased risk of complications.
We sought to understand the impact of interrupted ...radiofrequency (RF) delivery conditions on lesion characteristics in the atrial free wall.
Thirty-three (11 left atrial, 22 right atrial) RF ablation lesions were created in the atria of 6 swine using power control mode (25 W, target contact force 15 g) with 1 of 3 conditions: 15 seconds ablation (n = 8), 30 seconds ablation (n = 14), or 2 15-second ablations at the same site separated by a 2-minute interruption (15 seconds × 2) (n = 11).
Thirty of 33 lesions were transmural. Rates of transmurality (P = .45) and endocardial lesion width (5.6 ± 1.2 mm, P = .70) were similar between conditions. Mean tissue thickness was 1.7 ± 0.8 mm for transmural lesions. Wide variability in bipolar electrogram attenuation was observed across and within conditions and there were no significant between-group differences. Although impedance reductions were numerically greater in the 30-second and 15-second × 2 conditions (-14.6 ± 6.6 ohms and -14.0 ± 4.4 ohms, respectively) compared to the 15-second condition (-10.3 ± 6.4 ohms), variability was large, and differences were not statistically significant (P = .243). Impedance changes after ablation were largely transient.
A single 15-second ablation at 25 W (target contact force of 15 g) with good stability produced similarly sized lesions compared to 30-second ablations and 2 15-second ablations at the same site in atrial free wall tissue. These data suggest over-ablation in the atria is common, larger-diameter lesions may require greater power, and many clinically available parameters of lesion size may be unreliable on the posterior wall.
High-power, short-duration (HPSD) radiofrequency ablation (RFA) reduces procedure time; however, safety and efficacy thresholds vary with catheter design.
The study sought to determine optimal HPSD ...ablation conditions with a novel flexible-tipped, contact force–sensing RFA catheter.
RFA lesions were created in thigh muscle (16 swine) over a range of conditions (51–82 W, 2–40 g, 8–40 mL/min irrigation). An intracardiac study was performed (12 swine) to characterize steam pop thresholds. Lesions were created in a second intracardiac study (14 swine, n = 290 pulmonary vein isolation PVI lesions) with combinations of radiofrequency power, duration, and contact force. PVI was tested, animals were sacrificed, and lesions were measured.
The likelihood of coagulation formation in the thigh model was <20% when power was ≤79 W, when contact force was ≤40 g, when duration was ≤11 seconds, and when irrigation rates were 8 to 40 mL/min. The impact of contact force on lesion safety and efficacy was more pronounced using HPSD (60 W/8 seconds) compared with conventional ablation (30 W/45 seconds) (P = .038). During PVI, focal atrial lesions ranged in width from 4.2 to 12.5 mm and were transmural 80.8% of the time. PVI was achieved in 13 of 14 veins. Logistic regression identified that the optimal parameters for radiofrequency application were 60 to 70 W with a duration <8 seconds and <15 g contact force.
Optimal HPSD lesions with this this flexible-tipped, force-sensing RFA catheter were created at 60 to 70 W for <8 seconds with <15 g contact force. Chronic studies are ongoing to assess radiofrequency parameter refinements and long-term lesion durability using these conditions.
Display omitted
Unit-modulus least squares (ULS) problems arise in many applications, including phase-only beamforming, sensor network localization, synchronization, phase retrieval, and radar code design. ULS ...formulations can always be recast as unit-modulus quadratic programs, to which semidefinite relaxation (SDR) can be applied, and is often the state-of-the-art approach. However, SDR lifts the problem dimension (i.e., the number of variables) from N to N 2 , which drastically increases the memory burden and computational cost when the problem size is already large-e.g., when designing phase-only beamformer weights for massive multiple-input-multiple-output systems. This paper focuses on scalable first-order algorithms for the ULS problem and some of its variants. It advocates using simple gradient projection (GP) as a starting point for solving the ULS problem, establishes global convergence of GP to a Karush-Kuhn-Tucker point for this NP-hard problem, and bounds its iteration complexity. Then it proposes ULS extensions tailored to reflect practical beamformer design objectives, bringing in and exploiting new degrees of freedom to improve the beampattern designs. Simple variants of GP are proposed to deal with these extended ULS problems. Simulations are used to showcase the effectiveness of the proposed algorithms in both the plain ULS problem and in the context of phase-only beamforming.
Winner 2006 CJ Dennis Prize for Poetry (Victorian Premier's Literary Awards)Urban Myths: 210 Poems brings the best work to date from a poet considered one of the most original of his generation in ...Australia, together with a generous selection of new work. Smart, wry and very stylish, John Tranter's poems investigate the vagaries of perception and the ability of language to converge life, imagination and art so that we arrive, unexpectedly, at the deepest human mysteries.JUDGES REPORT - Victorian Premier's Literary AwardsThe new and uncollected poems in John Tranter's Urban Myths make a significant addition to his oeuvre. Control and ease are evident in the writing, which displays personages, occasions and moods of the metropolitan modern world. Tranter's latest poems refresh through the exercise of urbane skills: this is a poet suave and playful, but never aloof; linguistically various, assured in style, and never less than fully attentive.
PDF
