Persistent atrial fibrillation without the evidence of low-voltage areas: a prospective randomized trial

BACKGROUND

An effective therapy of persistent atrial fibrillation beyond pulmonary vein isolation remains unsatisfactory. Targeting endocardial low-voltage areas represents an approach of substrate modification. This prospective, randomized study investigated the efficacy of ablation of low-voltage areas versus PVI and additional linear ablations in patients with persistent atrial fibrillation in terms of single-procedure arrhythmia-free outcome and safety.

METHODS AND RESULTS

A total number of 100 patients undergoing de-novo catheter ablation for persistent AF were randomized in a 1:1 ratio into two different treatment arms: group A: pulmonary vein isolation (PVI) and, if low-voltage areas were present, a substrate modification. Group B: PVI and, if atrial fibrillation persisted, additional ablations, such as linear ablation and/or ablation of non-PV triggers. A total of 50 patients were randomized into each group without significant differences in baseline characteristics. During a mean follow-up of 17.64 ± 4.5 months after a single procedure, 34 (68%) patients of group A were free of arrhythmia recurrence versus 28 (56%) patients in group B (p = ns). In group A, 30 (60%) patients did not show endocardial fibrosis and received solely PVI. Both procedures were performed with a low number of complications; no pericardial effusion or stroke were seen in either group.

CONCLUSIONS

A significant proportion of patients with persistent atrial fibrillation do not show low-voltage areas. A total of 70% of the patients receiving solely PVI did not show any recurrence of atrial fibrillation, and therefore, extensive additional ablation should be avoided in de-novo patients.

Pulmonary vein isolation with high power, short duration ablation leads to shorter procedure times associated with high success rates: a Prospective Randomized Trial

Funding Acknowledgements

Type of funding sources: None.

Background

The single procedure success rates of durable pulmonary vein isolation (PVI) for paroxysmal atrial fibrillation (AF) varies between 85 and 90 %.

This prospective, randomized study investigated the efficacy of high power, short duration ablation in a temperature-controlled mode versus standard power settings in terms of single-procedure arrhythmia-free outcome, safety and procedural time.

Methods and results

A total number of 176 patients undergoing de-novo catheter ablation for paroxysmal AF were randomized to two different treatment arms. In group-A patients, PVI was performed with RF-energy with standard power settings of 30 Watts in a temperature-controlled mode.

The ablation procedure in group B was performed with RF-energy with higher power settings of 45 Watts. In both groups the ablation was performed with ablation index (AI) and following the CLOSE protocol (Biosense Webster Thermocool STSF).

A total of 88 patients were randomized into each group without significant differences in baseline characteristics.

During a mean follow-up of 12 ± 4 months after a single procedure, 79 (90%) patients of group A were free of arrhythmia recurrence versus 82 (93 %) patients in group B (p=ns).

With regard to the procedural data, the procedure time was significantly shorter in group B (115.35 ± 15.38 versus 96.45 ± 17.19; p<0.01), the flouroscopy time and dose area were also significantly lower in Group B (9.66 ± 3.86 vs 5.45 ± 2.35; 330.84 ± 150.36 vs 202.51 ± 135.23) and total ablation times were significantly shorter in group B ((Table 1). Both procedures were performed with a low number of complications, no pericardial effusion was seen in either group, in both groups two patients had a significant hematoma of the groin with the need of surgical repair.

Conclusions

RF-ablation with high power (45 Watts) in combination with ablation index and following the CLOSE protocol leads to shorter procedure times, a lower total ablation time and a good safety profile.

Improved durable pulmonary vein isolation with shorter procedure times and lower energy levels using RF ablation with ablation index and a stringent lesion contiguity

Background

The single procedure success rates of durable pulmonary vein isolation (PVI) for paroxysmal atrial fibrillation (PAF) varies between 80 and 90%. Ablation index, incorporating contact force, stability, time and power is a more profound parameter of significant lesion size and has been established. Equally important is a stringent contiguity of the lesion set.

Methods and results

A total number of 100 consecutive patients undergoing de-novo catheter ablation for paroxysmal atrial fibrillation (PAF) were analyzed between 2016 and 2019. In the first 50 patients (group A) PVI was performed using a surround flow, contact force catheter (Biosense Webster Thermocool STSF, Biosense Webster, USA) with a drag-and-ablate technique to encircle the PVs. In the following 50 patients (group B), PVI was performed using ablation index and a stringent lesion contiguity with an interlesion distance (ILD) of <5 mm. The baseline characteristics showed no significant differences between both groups. During a mean follow-up of 18 ± 3 months after a single procedure, 36 (72%) patients of group A were free of arrhythmia recurrence versus 43 (86%) patients in group B (p = 0.047). A total of 14 patients (group A: 10 (20%), group B: 4 (8%); underwent a redo-procedure. 7 patients of group A (14%) and 2 patients of group B (4%) showed recovered veins. In 3 patients of group A and 2 patients of group B the PVs were durably isolated. In these patients persistent AF recurrence was caused by extra-PV AF sources. Four patients of group A and three patients of group B had continued paroxysmal or persistent AF but did not undergo redo-procedure. With regard to the procedural data, the procedure time, the total energy and the fluoroscopy time were significantly lower in group B (AI and ILD <5 mm) (128.86 ± 18.19 versus 115.35 ± 15.38; p < 0.05; 1619.16 ± 988.56 versus 1186.26 ± 756.34; p < 0.05; 11.49 ± 3.20 versus 9.66 ± 3.86; p = 0.04). Both procedures were performed with a low number of complications, no pericardial effusion was seen in either group.

Conclusions

PVI using ablation index in combination with a stringent lesion contiguity improves clinical outcome after first-time PVI with lower PVI recovery, shorter procedure times, lower total energy and shorter fluoroscopy times and therefore, is more efficient.

Tunable electrochromic filter for in situ Fourier spatial frequency filtering

Spatial optical Fourier filtering is a widespread technique for in situ image or light field processing. However, conventional fixed absorbing patterns or mechanical irises only allow an inflexible, very restricted control. Thus, we present two electrochromic spatial filters with ring-shaped or directional segments, which can be individually addressed and continuously tuned in transmission resulting in up to 512 different filtering states. For realization of the electrochromic devices, we overcome technical obstacles to realize seamless, gap-free electrochromic segments. We describe this novel fabrication process and demonstrate the successful application in an optical Fourier transform set-up.

Implantation of leadless pacing systems in patients early after tricuspid valve surgery: A feasible option

BACKGROUND

After tricuspid valve (TV) surgery due to tricuspid regurgitation (TR), patients needing a permanent pacemaker often receive an epicardial lead implantation. This may result in delayed recovery from open-chest surgery and increased postoperative risk. Leadless pacemaker (LPM) implantation may represent a valuable option.

METHODS AND RESULTS

A total of 14 consecutive patients underwent LPM implantation (Micra Transcatheter Pacing System, Medtronic, Minneapolis, MN) early after TV surgery. The pacing indication in those patients was atrial fibrillation with a slow atrio-ventricular (AV) conduction or atrial fibrillation and a concomitant AV block III. Three patients already had a pacemaker prior to surgery, which was explanted during TV repair. Three patients received a valve replacement with a bioprosthesis, while the remaining eight patients received a TV repair. All procedural data and device measurements during and after LPM implantation were recorded. Transthoracic echocardiography was performed prior and post LPM implantation, showing no changes in TV or bioprosthesis performance. The device measurements were within an adequate range: threshold: 0.83 ± 0.34 V @ 0.24 ± 0 ms, impedance: 480 ± 58.88 ohm, and R-wave: 10.10 ± 3.60 mV. LPM implantation was successful in all patients with a mean procedural time of 32 ± 11.8 minutes, fluoroscopy time of 3.71 ± 3.15 minutes, and dose-area product of 536.67 ± 811.26 cGy/m² .

CONCLUSIONS

Implantation of an LPM early after TV surgery is a feasible option. LPM implantation does not affect TV or bioprosthesis performance in transthoracic echocardiography.

Possible influence of free fatty acid receptors on pH regulation in the ruminal epithelium of sheep

High amounts of short-chain fatty acids (SCFAs) occur in the ovine rumen and constitute the animal's main energy source. However, they lead to an acidification of the ruminal epithelium. Therefore, effective intracellular pH (pH_i ) regulation by transport proteins like monocarboxylate transporter 1 (MCT1) and Na⁺ /H⁺ exchangers (NHEs) is pivotal to ruminants to avoid epithelial damage. SCFAs might function not only as nutrients but also as signalling molecules by activating free fatty acid receptors (FFARs) in the ruminal epithelium and thus influence pH_i regulation. FFARs work as nutrient sensors, transducing their information by modulating cyclic adenosine monophosphate (cAMP) levels. We hypothesized that (FFAR-modulated) decreases in cAMP levels stimulate the activity of MCT1 and NHEs in the ruminal epithelium of sheep. We detected two FFARs (GPR109A and FFAR2) immunohistochemically in the ovine ruminal epithelium. Administration of 10 mM butyrate to Ussing chamber-mounted epithelia provoked a significant reduction in intraepithelial cAMP levels. However, application of the GPR109A agonist niacin did not affect cAMP levels. MCT1 activity was analysed by measuring transepithelial ¹⁴ C-acetate fluxes, which were not inhibited by forskolin-induced increased cAMP levels. The recovery of pH_i after acidification was assessed as an indicator of NHE activity in primary cultured ruminal epithelial cells. Recovery was significantly reduced when cells with increased cAMP levels were subjected to the NHE inhibitor 5-(N-ethyl-N-isopropyl)-amiloride (10 µM). Nonetheless, with augmented cAMP levels alone, NHE activity tended to decline. We hypothesize that modulation of cAMP levels by butyrate is accomplished by FFAR2 activation, regulating NHE activity for pH_i homoeostasis at least in part.

Evaluation of the hepatocyte-derived cell line BFH12 as an in vitro model for bovine biotransformation

The knowledge of drug metabolising enzymes (DMEs) in cattle is rather limited. The capability of the bovine foetal hepatocyte-derived cell line BFH12 to serve as model for biotransformation was evaluated. Gene expression analysis of DMEs was performed by reverse transcription PCR (RT-PCR). The presence of efflux transporters was visualised by immunocytochemistry, and functional induction of cytochrome P450 (CYP) 1A was assessed by the ethoxyresorufin-O-deethylase (EROD) assay. The production of bile acids was measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). RT-PCR revealed the expression of cytochromes 1A1, 1A2, 3A4 and phase II enzymes UGT1A1, UGT1A6 and GSTM1. Immunofluorescence demonstrated efflux transporters ABCG2 and ABCC1. The EROD assay revealed a dose-dependent CYP1A induction after treatment with benzo[a]pyrene (BP). LC-MS/MS analysis of cell culture supernatants showed the production of bile acids including taurocholic acid, tauro-chenodeoxycholic acid, taurodeoxycholic acid and taurolithocholic acid. The results strongly suggest the applicability of the cell line BFH12 for subsequent experiments in the emerging field of bovine biotransformation.

Experimental Studies on the Antithrombotic Action of a Highly Effective Synthetic Thrombin Inhibitor

The antithrombotic action of the highly effective synthetic thrombin inhibitor Nα-(2-naphthylsulfonylglycyl)-4-amidino-phenylalanine piperidide was studied in various models of experimental thrombosis in rats. Intravenous infusion of the thrombin inhibitor caused a dose-dependent inhibition or prevention of stasis-induced venous thrombosis, of arterial thrombosis after electrically-induced damage of the vessel wall and of thrombotic occlusion of an extracorporeal arterio-venous shunt.

Anticoagulant and Antithrombotic Action of Novel Specific Inhibitors of Thrombin

A series of new specific inhibitors of thrombin, cyclic amides of Nα-arylsulfonyl-amidinophenylalanine, was studied for anticoagulant action in vitro and in vivo. The inhibitors showed strong anticoagulant effects in vitro. The time course of the anticoagulant effect of the inhibitors in rabbits and rats was monitored using plasma thrombin time determinations. In rats, the inhibitors prevented the formation of experimental venous thrombi and of thrombin-induced microthrombosis. The new derivatives of benz-amidine presented may be useful as immediately acting anticoagulants.

Comparison of the Anticoagulant and Antithrombotic Effects of Synthetic Thrombin and Factor Xa Inhibitors

The anticoagulant effect of selected synthetic inhibitors of thrombin and factor Xa was studied in vitro in commonly used clotting assays. The concentrations of the compounds doubling the clotting time in the various assays were mainly dependent on their thrombin inhibitory activity. Factor Xa inhibitors were somewhat more effective in prolonging the prothrombin time compared to the activated partial thromboplastin time, whereas the opposite was true of thrombin inhibitors.

In vivo, in a venous stasis thrombosis model and a thromboplastin-induced microthrombosis model in rats the thrombin inhibitors were effective antithrombotically whereas factor Xa inhibitors of numerically similar IQ value for the respective enzyme were not effective at equimolar dosage

The results are discussed in the light of the different prelequisiles and conditions for inhibition of thrombin and factor Xa in the course of blood clotting.

Establishment and Characterization of an SV40 Large T Antigen-Transduced Porcine Colonic Epithelial Cell Line

Continuous cell lines have become indispensable tools that have enabled investigations into cellular mechanisms by increasing experimental reproducibility and sample availability, and decreasing the use of experimental animals. To facilitate studies of epithelial barrier function of the porcine colon, we aimed to establish an epithelial cell line with an extended replicative capacity. Cells were isolated from the proximal colon of a 3-week-old piglet and transduced using a recombinant retroviral vector construct containing the simian virus 40 large T antigen (SV40 TAg). We established a clonal epithelial cell line, referred to as PoCo83-3, that stably expressed the SV40 TAg, verified at mRNA and protein levels. PoCo83-3 showed epithelial cell-specific features, such as cobblestone-like morphology, dome structure formation, the presence of apical microvilli, and the expression of keratin 18, E-cadherin and the tight junction-associated proteins zonula occludens-1, occludin, and claudin-1. To validate PoCo83-3 as an in vitro model in epithelial barrier research, proinflammatory cytokine-inducible alterations in barrier integrity were demonstrated by incubating the cells with TNF-α and IFN-γ for 48 h. These cytokine treatments promoted a decreased transepithelial electrical resistance. In summary, PoCo83-3 exhibited an extended life span and a differentiated phenotype while maintaining epithelial characteristics. Based on these results, we present this cell line as a valuable in vitro model for investigations of epithelial barrier function in the porcine colon.

Silicon based tandem cells: novel photocathodes for hydrogen production

A photovoltaic tandem cell made of amorphous silicon (a-Si) and microcrystalline silicon (μc-Si) was investigated as a photocathode for hydrogen evolution in a photoelectrochemical device. The electronic and electrochemical properties of the samples were characterized using X-ray photoemission spectroscopy (XPS) and cyclic voltammetry (CV), whereas the morphology of the surface in contact with the electrolyte was investigated by scanning electron microscopy (SEM). The electric efficiency of the tandem cell was determined to be 5.2% in a photoelectrochemical (PEC) setup in acidic solution which is only about half of the photovoltaic efficiency of the tandem cell. A significant improvement in efficiency was achieved with platinum as a catalyst which was deposited by physical vapour deposition (PVD) under ultra-high vacuum (UHV) conditions.

[Clinical relevance and indications for cardiac magnetic resonance imaging 2013: an interdisciplinary expert statement]

During the last years the indications of Cardiac Magnetic Resonance Imaging (CMRI) have been continuously expanded. However, the acceptance of the method by cardiologists and radiologists does not correlate with respect to the diagnostic potential. Several factors, such as expensive equipment, relatively long examination times, high technical know how and lack of remuneration, limit the application of CMRI in everyday clinical practice. Furthermore, doctors tend to apply more conventional, well established diagnostic procedures, the access to the method is still limited and there exist difficulties in the interdisciplinary collaboration. The interdisciplinary Austrian approach to Cardiac Imaging is aimed to improve the aforementioned problems and to support the implementation of CMRI in the diagnostic tree of cardiac diseases thus enabling a cost efficient management of patients in cardiology.

Effect of abiraterone acetate plus prednisone on the pharmacokinetics of dextromethorphan and theophylline in patients with metastatic castration-resistant prostate cancer

PURPOSE

To assess the effect of abiraterone acetate plus prednisone on the pharmacokinetics of dextromethorphan HBr (CYP2D6 substrate) and theophylline (CYP1A2 substrate) in patients with metastatic castration-resistant prostate cancer (mCRPC).

METHODS

Men with progressive metastatic mCRPC who failed gonadotropin-releasing hormone therapy and ≥1 lines of chemotherapy were enrolled. Patients received two doses of dextromethorphan HBr-30 mg (n = 18; group A) or theophylline-100 mg (n = 16; group B) under fasting conditions; one dose on cycle 1, day -8, and the other dose on cycle 1, day 8. Only patients with extensive CYP2D6 metabolizing status were assigned to group A. All patients received continuous daily oral abiraterone acetate (1,000 mg) plus prednisone (10 mg) starting on cycle 1, day 1.

RESULTS

Coadministration of abiraterone acetate plus prednisone increased the systemic exposure of dextromethorphan by approximately 100%. Ratios of geometric means for maximum plasma concentration (C(max)) (275.36%) and area under plasma concentration-time curves from time 0 to 24 h (AUC(24h)) (268.14%) of dextromethorphan were outside the bioequivalence limit. The pharmacokinetics of theophylline was unaltered following coadministration of abiraterone acetate plus prednisone. Ratios of geometric means [C(max); 102.36% and AUC(24h); 108.03%] of theophylline exposure parameters were within the bioequivalence limit. The safety profile of abiraterone acetate was consistent with reported toxicities.

CONCLUSION

Abiraterone acetate plus prednisone increased the exposure of dextromethorphan, suggesting a need for caution when coadministrating with known CYP2D6 substrates. The pharmacokinetics of theophylline was unaffected when coadministered with abiraterone acetate plus prednisone.

Antagonism of the antithrombotic and anti-atherosclerotic actions of aspirin by rofecoxib in the cholesterol-fed rabbit

BACKGROUND AND PURPOSE

Most patients at elevated cardiovascular risk receive long-term aspirin (ASA) anti-platelet treatment. The present study specifically addresses the pharmacological interactions between selective COX-2 inhibitors and ASA and the possible consequences for the thrombotic risk during long-term treatment.

EXPERIMENTAL APPROACH

New Zealand white rabbits were fed a standard laboratory diet supplemented with 1% cholesterol (CON) for 12 weeks. Age-matched control rabbits were fed the same standard diet without addition of cholesterol (SD). Rabbits were randomly assigned to one of the following groups: rofecoxib (ROFE, 25 mg·kg⁻¹, bid), acetylsalicylic acid (ASA, 5 mg·kg⁻¹, bid) or a combination of both (ASA + ROFE). At the end of the feeding period, the severity of atherosclerotic plaque formation was assessed in the aorta. Thrombus formation was assessed in the left carotid artery using a modified Folts procedure.

KEY RESULTS

Treatment of cholesterol-fed rabbits with ASA significantly reduced plaque formation. This reduction in lesion size was not observed in animals treated with the combination of rofecoxib and ASA. In the modified Folts model, treatment with either rofecoxib or ASA increased the total blood flow above that of untreated animals. This increase was statistically significant in the case of ASA, while cotreatment with rofecoxib abolished this ASA effect completely and reduced the total flow rate to the levels seen in untreated hypercholesterolaemic controls.

CONCLUSIONS

COX-2 inhibition by rofecoxib attenuates the antithrombotic and anti-atherosclerotic effects of ASA during long-term treatment in cholesterol-fed rabbits.

Electromagnetic navigation bronchoscopy (ENB): Increasing diagnostic yield

OBJECTIVES

To determine factors associated with diagnostic yield of ENB.

METHODS

In 112 consecutive patients referred to our department between March 2010 and December 2010 the diagnostic work-up for solitary pulmonary lesions included a FDG-PET-CT scan, and ENB in combination with ROSE. The final diagnosis was confirmed by histopathological evaluation of specimen obtained either by ENB, or - if ENB was not diagnostic - by CT-guided fine needle aspiration or surgery.

RESULTS

Thirty-seven (33%) subjects were female, mean age was 66.7 (±1.04) years. The mean diameter of lesions was 27mm (range: 6-46mm). In 83.9% the combination of PET-CT, ENB, and ROSE established a correct diagnosis, as defined by the definite histopathological result. 15.2% (17/112) of lesions were benign, and 84.8% (95/112) were malignant. For 112 procedures we observed a steep learning curve with a diagnostic yield of 80% and 87.5% for the first 30 and last 30 procedures, respectively. The diagnostic yield in lesions ≤20mm and >20mm in diameter was 75.6% and 89.6% (p=0.06), respectively. No significant difference in diagnostic yield was seen depending on lung function, and the localization of the lesions. Two cases (1.8%) of pneumothorax were seen during and up to 24h after bronchoscopy, none of them required a chest tube.

CONCLUSION

Diagnostic yield increased with experience but was independent from the size of the lesion, the localisation in the lungs, and lung function. The diagnostic yield of ENB can be as high as for CT-guided transthoracic biopsies but carries a significantly lower complication rate.

An improved time-of-flight method for cluster deposition and ion-scattering experiments

A molecular beam apparatus has been developed for deposition and scattering experiments of size-selected clusters. The new setup combines a bimetallic laser ablation cluster source with a collinear time-of-flight mass spectrometer. Mass selection is achieved with a pulsed electrostatic mirror. A significantly improved transmission in combination with a reduction of the kinetic energy distribution of the mass selected clusters has been obtained. Without further modification of the apparatus, surface-induced dissociation of mass selected tin clusters has been investigated, demonstrating the possibility to combine cluster beam deposition and scattering experiments.

Ultrasonic force microscopy on strained antimony nanoparticles

Ultrasonic force microscopy (UFM) is used to resolve the elastic nanostructure of strained antimony (Sb) particles. These nanoparticles were formed by aggregation and spontaneous rapid crystallization of thermally deposited Sb onto the (0001) basal planes of highly oriented pyrolytic graphite (HOPG) and molybdenum disulfide (MoS(2)). UFM reveals clear contrast within individual nanoparticles, which can be attributed to differences in the local stiffness. This interpretation is confirmed by transmission electron microscopy (TEM) images, in which bending contours prove the existence of strained regions within the nanocrystals.