Preclinical Characterization of Vadadustat (AKB-6548), an Oral Small Molecule Hypoxia-Inducible Factor Prolyl-4-Hydroxylase Inhibitor, for the Potential Treatment of Renal Anemia.

Pharmacological inhibition of prolyl-4-hydroxylase domain (PHD) enzymes stabilizes hypoxia-inducible factors (HIFs), transcription factors that activate target genes that, among others, increase erythropoietin (EPO) synthesis, resulting in the production of new red blood cells (RBCs). Herein, we summarize the preclinical characteristics of the small molecule HIF prolyl-4-hydroxylase inhibitor vadadustat (AKB-6548), which is in development for the treatment of anemia in patients with chronic kidney disease (CKD). Vadadustat inhibits the enzyme activity of all three human PHD isozymes, PHD1, PHD2, and PHD3, with similar low nanomolar inhibitory constant values. PHD enzyme inhibition by vadadustat is competitive with endogenous cofactor 2-oxoglutarate and is insensitive to free iron concentration. In the human hepatocellular carcinoma cell line (Hep 3B) and human umbilical vein endothelial cells, PHD inhibition by vadadustat leads to the time- and concentration-dependent stabilization of HIF-1α and HIF-2α In Hep 3B cells, this in turn results in the synthesis and secretion of EPO; vascular endothelial growth factor is not measured at detectable levels. A single oral dose of vadadustat in rats potently increases circulating levels of EPO, and daily oral dosing for 14 days increases RBC indices in healthy rats and in the 5/6 nephrectomy model of CKD. In mice and dogs, once-daily repeat oral dosing increases hemoglobin and hematocrit. Vadadustat has a relatively short half-life in all nonclinical species evaluated and does not accumulate when administered as a single bolus dose (oral or intravenous) or upon repeat oral dosing. The pharmacological profile of vadadustat supports continued development for treatment of renal anemia. SIGNIFICANCE STATEMENT: Vadadustat (AKB-6548) is an orally bioavailable small molecule prolyl-4-hydroxylase inhibitor in development for anemia of chronic kidney disease. It is an equipotent inhibitor of the three human prolyl-4-hydroxylase domain isoforms, which activates erythropoiesis through stabilization of hypoxia-inducible factor (HIF)-1α and HIF-2α, increasing production of erythropoietin, without detectable stimulation of vascular endothelial growth factor.

Amelioration of chronic kidney disease-associated anemia by vadadustat in mice is not dependent on erythroferrone.

Vadadustat is an investigational hypoxia-inducible factor prolyl hydroxylase inhibitor that increases endogenous erythropoietin production and has been shown to decrease hepcidin levels, ameliorate iron restriction, and increase hemoglobin concentrations in anemic patients with chronic kidney disease (CKD). In studies of physiological responses to other erythropoietic stimuli, erythropoietin induced erythroblast secretion of erythroferrone (ERFE), which acts on the liver to suppress hepcidin production and mobilize iron for erythropoiesis. We therefore investigated whether vadadustat effects on erythropoiesis and iron metabolism are dependent on ERFE. Wild type and ERFE knockout mice with and without CKD were treated with vadadustat or vehicle. In both wild type and ERFE knockout CKD models, vadadustat was similarly effective, as evidenced by normalized hemoglobin concentrations, increased expression of duodenal iron transporters, lower serum hepcidin levels, and decreased tissue iron concentrations. This is consistent with ERFE-independent increased iron mobilization. Vadadustat treatment also lowered serum urea nitrogen and creatinine concentrations and decreased expression of kidney fibrosis markers. Lastly, vadadustat affected fibroblast growth factor 23 (FGF23) profiles: in non-CKD mice, vadadustat increased plasma total FGF23 out of proportion to intact FGF23, consistent with the known effects of hypoxia-inducible factor-1α and erythropoietin on FGF23 production and metabolism. However, in the mice with CKD, vadadustat markedly decreased both total and intact FGF23, effects likely contributed to by the reduced loss of kidney function. Thus, in this CKD model, vadadustat ameliorated anemia independently of ERFE, improved kidney parameters, and decreased FGF23. How vadadustat affects CKD progression in humans warrants future studies.

Recent advances in acute kidney injury and its consequences and impact on chronic kidney disease.

PURPOSE OF REVIEW: Acute kidney injury (AKI) remains a major unmet medical need and associates with high morbidity, mortality, and healthcare costs. Among survivors, long-term outcomes of AKI can include development of chronic kidney disease (CKD) or progression of preexisting CKD. In this review, we focus on ongoing efforts by the AKI community to understand the human AKI to CKD continuum, with an emphasis on the cellular stress responses that underlie AKI and the maladaptive responses that persist in the acute-to-chronic phase. The emphasis is on work that has been published in the past year in this rapidly expanding field. RECENT FINDINGS: Recent studies in preclinical models highlight the importance of mitochondrial dysfunction, cell death, and inflammation on the underlying pathogenesis of AKI. These pathogenic mechanisms can resolve with adaptive kidney repair but persist in maladaptive repair that leads to progressive chronic disease. The complexity and interconnections of these pathways involve cross-talk between the tubular epithelium, endothelium, and interstitial compartments. SUMMARY: Approaches which lessen or counteract these cellular responses represent novel strategies to prevent AKI and stop or slow down the progression to CKD.

Acute Kidney Injury.

Acute kidney injury (AKI) is a global public health concern associated with high morbidity, mortality, and healthcare costs. Other than dialysis, no therapeutic interventions reliably improve survival, limit injury, or speed recovery. Despite recognized shortcomings of in vivo animal models, the underlying pathophysiology of AKI and its consequence, chronic kidney disease (CKD), is rich with biological targets. We review recent findings relating to the renal vasculature and cellular stress responses, primarily the intersection of the unfolded protein response, mitochondrial dysfunction, autophagy, and the innate immune response. Maladaptive repair mechanisms that persist following the acute phase promote inflammation and fibrosis in the chronic phase. Here macrophages, growth-arrested tubular epithelial cells, the endothelium, and surrounding pericytes are key players in the progression to chronic disease. Better understanding of these complex interacting pathophysiological mechanisms, their relative importance in humans, and the utility of biomarkers will lead to therapeutic strategies to prevent and treat AKI or impede progression to CKD or end-stage renal disease (ESRD).

Differential Ly6C Expression after Renal Ischemia-Reperfusion Identifies Unique Macrophage Populations.

Macrophages are a heterogeneous cell type implicated in injury, repair, and fibrosis after AKI, but the macrophage population associated with each phase is unclear. In this study, we used a renal bilateral ischemia-reperfusion injury mouse model to identify unique monocyte/macrophage populations by differential expression of Ly6C in CD11b(+) cells and to define the function of these cells in the pathophysiology of disease on the basis of microarray gene signatures and reduction strategies. Macrophage populations were isolated from kidney homogenates by fluorescence-activated cell sorting for whole genome microarray analysis. The CD11b(+)/Ly6C(high) population associated with the onset of renal injury and increase in proinflammatory cytokines, whereas the CD11b(+)/Ly6C(intermediate) population peaked during kidney repair. The CD11b(+)/Ly6C(low) population emerged with developing renal fibrosis. Principal component and hierarchical cluster analyses identified gene signatures unique to each population. The CD11b(+)/Ly6C(intermediate) population had a distinct phenotype of wound healing, confirmed by results of studies inhibiting the macrophage colony-stimulating factor 1 receptor,whereas the CD11b(+)/Ly6C(low) population had a profibrotic phenotype. All populations, including the CD11b(+)/Ly6C(high) population, carried differential inflammatory signatures. The expression of M2-specific markers was detected in both the CD11b(+)/Ly6C(intermediate) and CD11b(+)/Ly6C(low) populations, suggesting these in vivo populations do not fit into the traditional classifications defined by in vitro systems. Results of this study in a renal ischemia-reperfusion injury model allow phenotype and function to be assigned to CD11b(+)/Ly6C(+) monocyte/macrophage populations in the pathophysiology of disease after AKI.

Pharmacokinetics, Pharmacodynamics, and Safety of Vadadustat in Healthy Volunteers and Patients with Chronic Kidney Disease.

Vadadustat is an oral hypoxia-inducible factor prolyl hydroxylase inhibitor for treating anemia in chronic kidney disease (CKD). Single ascending dose (SAD) and multiple ascending dose (MAD) studies assessed pharmacokinetics (PK), pharmacodynamics (PD), and safety of vadadustat in healthy volunteers. A single-dose, open-label study was conducted in patients with CKD stages 3 and 4 not on dialysis. In the SAD study, 48 healthy adult men (n = 8/cohort) received single doses of vadadustat (80-1,200 mg) or placebo. In the MAD study, 34 healthy adult men (n = 8-9/cohort) received daily vadadustat (500-900 mg) or placebo for 10 days. In the single-dose CKD study, 22 male and female patients with CKD (stage 3: n = 10; stage 4: n = 12) received single doses of vadadustat (500 mg). PK parameters included plasma vadadustat; PD biomarkers were measured, including erythropoietin (EPO) levels, reticulocytes, and others. Plasma vadadustat peaked 3-4 hours after single or multiple dosing in healthy volunteers, with a mean t1/2 of approximately 4.5 hours. In patients with CKD, plasma vadadustat peaked at 5-6 hours, with a mean t1/2 of 7.2 (stage 3) and 8.5 (stage 4) hours. Vadadustat AUC∞ and Cmax increased dose proportionally in SAD and MAD trials. In all trials, EPO concentrations increased in a dose-related manner and returned approximately to baseline by 24 hours. Adverse events were mild and considered not study drug related. The PK and PD results of these studies were utilized for further clinical development of vadadustat for treatment of anemia in CKD patients.

An extension of biorelevant fed-state dissolution tests to clinical pharmacokinetics - A study on gastrointestinal factors influencing rivaroxaban exposure and efficacy in atrial fibrillation patients.

A direct oral anticoagulant rivaroxaban fails to prevent stroke and systemic embolism in one-to-several percent of patients with nonvalvular atrial fibrillation (NVAF), but the reasons are unknown. The study used semi-mechanistic in vitro-in vivo prediction (IVIVP) modeling to explore the reasons for ineffective thrombosis prevention in NVAF patients. Steady-state drug concentrations in plasma were measured at 0 h (Ctrough), 3 h (C3h), and 12 h post-dosing in thirty-four patients treated with 20 mg rivaroxaban daily. The clinical data were compared against "virtual twins" generated with a novel IVIVP model that combined drug dissolution modeling, mechanistic description of gastric drug transit, and population pharmacokinetics defining the variability of drug disposition. The nonresponders had significantly lower C3h and Ctrough than the responders (p < 0.001) and the covariates included in the population pharmacokinetic submodel did not fully explain this difference. Simulations involving varied gastrointestinal parameters in the "virtual twins" revealed that lower small intestinal effective permeability (Peff), rather than a slower stomach emptying rate, could explain low rivaroxaban exposure in the nonresponders. IVIVP modeling was effectively used for exploring pharmacotherapy failure. Low Peff, found as a major determinant of ineffective rivaroxaban treatment, encourages further research to find (pato)physiological factors influencing suboptimal absorption.

Well-palpable pulse over an occluded radial artery: A case series reporting ultrasound outcomes.

We report a case series of four patients with radial artery occlusion complicating vascular access who were scheduled for coronary angiography. We describe the challenges in selecting adequate vascular access in patients with a history of coronary angiography and percutaneous coronary intervention, as well as the benefits of using preprocedural ultrasound examination of forearm arteries to detect radial artery occlusion. Our case series suggests that if the anterior interosseous artery provides partial blood supply to the hand as a collateral circulation of the occluded radial artery, the transulnar approach may be an alternative safe option for coronary angiography and percutaneous coronary intervention in this population.

Variability of baroreceptor reflex assessed by tilt table test in a patient undergoing pulmonary vein isolation.

BACKGROUND: The autonomic nervous system (ANS) plays a significant role in atrial fibrillation (AF). Catheter ablation (CA) affects the ANS balance. The assessment of baroreceptor (BR) function is an established method to measure parasympathetic activity; however, it has been rarely used in patients undergoing CA of AF. AIMS: This study is to assess changes in BR function caused by CA and to compare these changes between two different types of CA: point-by-point radiofrequency (RF) versus cryoballoon (CB). METHODS: In this observational, prospective, single center study, 78 patients (25 females, mean age 58 ± 9) with paroxysmal AF and first CA were included: 39 patients (RF group) and 39 (CB group). The BR function was assessed non-invasively using tilt testing and three parameters: event count (BREC) depicting overall BR activity, slope mean depicting BR sensitivity (BRS), and BR effectiveness index (BEI). RESULTS: The groups did not differ in clinical or demographic data. Before CA, tilting caused a marked decrease in BR function parameters in the whole study group (BREC (29 ± 14.0-50.0 vs 28 ± 9.0-44.0, p < 0.068), BRS (10.2 ± 7.1-13.2 vs 5.8 ± 4.9-8.5; p < 0.001), and BEI (52.9 ± 39.9-65.5 vs 39.6 ± 23.6-52.1; p < 0.001), supine vs tilting, respectively). These changes were similar in the both groups. After CA, BR function decreased in the whole group (BREC 12.0 ± 3.0-22.0 vs 6.0 ± 3.0-18.0, p = 0.004; BRS 4.8 ± 3.6-6.8 vs 4.0 ± 3.0-5.8, p = 0.014; BEI 18.7 ± 8.3-27.4 vs 12.0 ± 5.1-21.0, p = 0.009). BREC was significantly more decreased in the CB vs RF. Similar trend was noted for BRS and BEI. CONCLUSIONS: CA significantly affects BR function. These changes were more pronounced following CB rather than RF CA.

Stiffness changes of tumor HEp2 cells correlates with the inhibition and release of TRAIL-induced apoptosis pathways.

Tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL) is a promising apoptotic agent that can selectively act on tumor cells. However, some cancer cells are resistant to TRAIL mediated apoptosis. In specific type of cells, sensitization by chemotherapeutic drugs may overcome the resistance to TRAIL induced apoptosis. In this work, atomic force microscopy (AFM) nanoindentation spectroscopy combined with fluorescence methods were used to investigate the biomechanical aspects of the resistance and unblocking of apoptosis in larynx carcinoma HEp2 cells treated with TRAIL. It is shown that there is a direct correlation between the increase in mechanical cell stiffness and the inhibition of apoptosis induced by TRAIL in HEp2 cells. Conversely, unblocking of apoptosis by sensitization of HEp2 cells with a chemotherapeutic drug Actinomycin D is related to the depolymerization of F-actin and to the decrease in the cell stiffness. Both effects, that is, changes in the mechanical stiffness of the cell and the inhibition of apoptotic pathway, are closely related to the Bcl-2 activity. Most probably, the depolymerization of F-actin results from downregulation of Rho protein, which in turn is accompanied by a lower activity of Bcl-2 and in consequence releases the intrinsic apoptotic channel. The presented results reveal a promising application of nanoindentation spectroscopy with an AFM tip as a novel tool for monitoring the processes of apoptosis inhibition.

Ultrasound-guided extracardiac vagal stimulation-New approach for visualization of the vagus nerve during cardioneuroablation.

BACKGROUND: Fluoroscopy-guided extracardiac vagal stimulation (ECVS) from the internal right and left jugular veins (RIJV and LIJV) is routinely used to document vagal response (sinus arrest and/or atrioventricular block) during cardioneuroablation. Ultrasound-guided ECVS allows direct visualization and selective stimulation of the vagus nerve (VN). OBJECTIVES: The objectives of this study were to assess the feasibility of ultrasound-guided ECVS and to compare it with fluoroscopy-guided ECVS. METHODS: The study group consisted of 48 patients (25 men [52%]; mean age 38 ± 15 years) in whom fluoroscopy-guided ECVS and ultrasound-guided ECVS were performed. For fluoroscopy-guided ECVS, a pacing electrode was introduced into the RIJV and into the LIJV up to the level of the jugular foramen under fluoroscopic guidance. For ultrasound-guided ECVS, the VN and electrode were visualized using ultrasonography. Partial vagal response was defined as induction of sinus arrest or atrioventricular block, whereas full vagal response was defined as induction of both. RESULTS: ECVS was performed in all patients from the RIJV and in 45 from the LIJV. Visualization of the VN using ultrasound was possible in 44 patients (92%). During ECVS from the RIJV, partial vagal response was obtained in 39 (81%) using fluoroscopy-guided ECVS vs 45 (94%) using ultrasound-guided ECVS (not significant) whereas full vagal response was obtained in 27 patients (56%) using fluoroscopy-guided ECVS vs 40 (83%) using ultrasound-guided ECVS (P = .0071). For ECVS from the LIJV, partial vagal response was achieved in 40 (89%) vs 44 (98%) patients (not significant) whereas full vagal response was achieved in 30 (67%) vs 40 (89%) patients (P = .021) (fluoroscopy-guided ECVS vs ultrasound-guided ECVS, respectively). CONCLUSION: Ultrasound-guided ECVS is feasible and full vagal response is achieved significantly more frequently than using fluoroscopy-guided ECVS.

Cardioneuroablation changes the type of vasovagal response in patients with asystolic reflex syncope.

BACKGROUND: Cardioneuroablation (CNA) has been recently proposed as a new therapy in patients with asystolic vasovagal syncope (VVS) caused by parasympathetic overactivity. OBJECTIVE: To assess the impact of CNA on the type of VV response during tilt testing (TT). METHODS: The study group consisted of 20 patients (7 males, mean age 38 ± 9). All patients had a history of syncope due to asystole and confirmed asystolic VVS at baseline TT (TT1). CNA was performed in the right and left atrium. The second TT (TT2) and Holter ECG were performed three months later. All patients completed one-year follow up. RESULTS: At TT1, twenty patients had cardioinhibitory syncope and 1 had mixed VVS with asystole > 3 s. During one-year follow-up no spontaneous syncopal episodes were noted. At TT2, 6 patients had no syncope whereas the remaining 13 had syncope - twelve due to vasodepressor mechanism and only one due to asystole. Mean heart rate after CNA was significantly faster and heart rate variability parameter (SDNN) lower than before the procedure (82 ± 9 vs 69 ± 11 beats/min, p = 0.0003 and 74 ± 22 vs 143 ± 40 ms, p = 000001, respectively). These changes were similar in those who fainted during TT2 and those who did not (84 ± 10 vs 81 ± 5 beats/min, p = NS and 72 ± 24 vs 72 ± 19 ms, p = NS, respectively). CONCLUSIONS: CNA profoundly affects type of VV reaction causing normalization of the response to tilting or changing cardiodepression to vasodepression. Changes in heart rate and heart rate variability are consistent with attenuation of parasympathetic activity.

The Impact of Using a Larger Forearm Artery for Percutaneous Coronary Interventions on Hand Strength: A Randomized Controlled Trial.

(1) Background: The exact mechanism underlying hand strength reduction (HSR) after coronary angiography with transradial access (TRA) or transulnar access (TUA) remains unknown. (2) Methods: This study aimed to assess the impact of using a larger or smaller forearm artery access on the incidence of HSR at 30-day follow-up. This was a prospective randomized trial including patients referred for elective coronary angiography or percutaneous coronary intervention. Based on the pre-procedural ultrasound examination, the larger artery was identified. Patients were randomized to larger radial artery (RA) or ulnar artery (UA) or a group with smaller RA/UA. The primary endpoint was the incidence of HSR, while the secondary endpoint was the incidence of subjective HSR, paresthesia, and any hand pain. (3) Results: We enrolled 200 patients (107 men and 93 women; mean age 68 ± 8 years) between 2017 and 2018. Due to crossover between TRA and TUA, there were 57% (n = 115) patients in larger RA/UA and 43% (n = 85) patients in smaller RA/UA. HSR occurred in 29% (n = 33) patients in larger RA/UA and 47% (n = 40) patients in smaller RA/UA (p = 0.008). Subjective HSR was observed in 10% (n = 12) patients in larger RA/UA and 21% (n = 18) patients in smaller RA/UA (p = 0.03). Finally, paresthesia was noted in 7% (n = 8) patients in larger RA/UA and 22% (n = 15) in smaller RA/UA (p = 002). Independent factors of HSR were larger RA/UA (OR 0.45; 95% CI, 0.24-0.82; p < 0.01) and the use of TRA (OR 1.87; 95% CI, 1.01-34; p < 0.05). (4) Conclusions: The use of a larger artery as vascular access was associated with a lower incidence of HSR at 30-day follow-up.

Impact of the Use of a Larger Forearm Artery on the Efficacy and Safety of Transradial and Transulnar Access: A Randomized Trial with Preprocedural Ultrasonography.

(1) Background: We aimed to assess the impact of the selection of a larger radial or ulnar artery on the efficacy of access and vascular complications, based on preprocedural ultrasonographic examination. (2) Methods: This prospective, randomized trial included patients undergoing coronary angiography (CAG) or percutaneous coronary intervention (PCI). Patients were randomized into either a larger ulnar artery (UA) or radial artery (RA) group or smaller UA/RA group. The primary endpoint was successful CAG/PCI without crossover to another artery. The secondary endpoints were incidences of radial or ulnar artery occlusion (RAO/UAO) at the 24 h and 30 day follow-up. (3) Results: Between 2017 and 2018, 200 patients (107 men, mean age 68 ± 8 years) were enrolled. The success of CAG/PCI via the access site was 98% and 83% (p < 0.001) in the larger UA/RA group and smaller UA/RA group, respectively. The independent factor for CAG/PCI success was the larger artery (OR 9.8, 95%CI 2.11-45.5; p < 0.005). The larger UA/RA was superior, with RAO/UAO at 24 h: OR 0.07, 95%CI 0.09-0.61; p < 0.016; and RAO/UAO at 30 days: OR 0.25, 95%CI 0.05-0.12; p < 0.001. (4) Conclusions: Larger artery access was shown to be more efficient and safer than recessive forearm artery access.

Protective effect of 20-HETE analogues in experimental renal ischemia reperfusion injury.

While it is known that the arachidonic acid metabolite 20-hydroxyeicosatetraenoic acid (20-HETE) contributes to ischemic injury in the heart and brain, its role in kidney injury is unclear. Here we determined the effects on ischemia-reperfusion injury of the 20-HETE analogues, 20-hydroxyeicosa-5(Z), 14(Z)-dienoic acid (5,14-20-HEDE), and N-[20-hydroxyeicosa-5(Z),14(Z)-dienoyl]glycine (5,14-20-HEDGE), and of the inhibitor of 20-HETE synthesis N-hydroxy-N-(4-butyl-2 methylphenyl) formamidine (HET0016). Using Sprague-Dawley rats we found that while treatment with the inhibitor exacerbated renal injury, infusion of both 5,14-20-HEDE and 5,14-20-HEDGE significantly attenuated injury when compared to vehicle or inhibitor-treated rats. Medullary blood flow, measured by laser-Doppler flowmetry, decreased to half of the baseline one hour after reperfusion in the control rats, but 5,14-20-HEDGE completely prevented this. Treatment of control animals with 5,14-20-HEDGE increased urine output and sodium excretion without altering their mean arterial pressure or glomerular filtration rate. Our results suggest that 20-HETE analogues protect the kidney from ischemia-reperfusion injury by inhibiting renal tubular sodium transport and preventing the post-ischemic fall in medullary blood flow. Analogues of 20-HETE may be useful in the treatment of acute ischemic kidney injury.

Regulated synthesis and functions of laminin 5 in polarized madin-darby canine kidney epithelial cells.

Renal tubular epithelial cells synthesize laminin (LN)5 during regeneration of the epithelium after ischemic injury. LN5 is a truncated laminin isoform of particular importance in the epidermis, but it is also constitutively expressed in a number of other epithelia. To investigate the role of LN5 in morphogenesis of a simple renal epithelium, we examined the synthesis and function of LN5 in the spreading, proliferation, wound-edge migration, and apical-basal polarization of Madin-Darby canine kidney (MDCK) cells. MDCK cells synthesize LN5 only when subconfluent, and they degrade the existing LN5 matrix when confluent. Through the use of small-interfering RNA to knockdown the LN5 alpha3 subunit, we were able to demonstrate that LN5 is necessary for cell proliferation and efficient wound-edge migration, but not apical-basal polarization. Surprisingly, suppression of LN5 production caused cells to spread much more extensively than normal on uncoated surfaces, and exogenous keratinocyte LN5 was unable to rescue this phenotype. MDCK cells also synthesized laminin alpha5, a component of LN10, that independent studies suggest may form an assembled basal lamina important for polarization. Overall, our findings indicate that LN5 is likely to play an important role in regulating cell spreading, migration, and proliferation during reconstitution of a continuous epithelium.

Acceleration of sinus rhythm following ablation for atrial fibrillation: a simple parameter predicting ablation efficacy.

BACKGROUND: Pulmonary vein isolation (PVI) is a well­established treatment method in patients with paroxysmal atrial fibrillation (AF). However, the predictors of a successful outcome are less well known. It has been suggested that PVI­induced changes in autonomic control of sinus rate (SR) may correspond to ablation efficacy. AIMS: We aimed to assess whether PVI­induced changes in SR may help identify responders to PVI. METHODS: The study group consisted of 111 consecutive patients (mean [SD] age, 55 [10] years; 81 men) who underwent the first ablation of paroxysmal AF (radiofrequency [RF] ablation, 56 patients; cryoballoon [CB] ablation, 55 patients). The SR was calculated from a standard 12­lead electrocardiogram recorded a day before and 2 days after ablation. Patients were followed for 1 year on an outpatient basis and underwent serial 4- to 7­day Holter electrocardiogram recordings at 3, 6, and 12 months after ablation. RESULTS: Ablation was effective in 74 patients (67%). Univariate and multivariate analyses showed that younger age, faster SR, and a greater increase in SR (ΔSR) after ablation were significantly associated with successful outcome. The results were similar between patients who underwent RF and CB ablation. The sensitivity, specificity, negative predictive value, and positive predictive value of ΔSR higher than 15 bpm for the identification of responders were 53%, 73%, 80%, and 44%, respectively. CONCLUSIONS: Acceleration of SR following ablation for paroxysmal AF may serve as an additional simple clinical parameter that may improve the prediction of outcome after PVI.

Iatrogenic Arteriovenous Fistula and Atrial Septal Defect Following Cryoballoon Ablation for Atrial Fibrillation - Two Correctable Causes of Right Heart Failure.

BACKGROUND Catheter ablation for atrial fibrillation is an important therapeutic intervention. One of the most frequent complications of this procedure is vascular issues including arteriovenous fistula. Iatrogenic atrial septal defect (IASD) has been reported as a complication of transseptal puncture; however, no data are available demonstrating any coexistent of arteriovenous fistula with IASD. CASE REPORT A 61-year-old female patient was admitted to our center for catheter ablation for persistent atrial fibrillation. Her past medical history was significant for cryoballoon ablation for atrial fibrillation in 2015, which was subsequently complicated by hematoma and arteriovenous fistula at puncture site. After general surgery consultation, the patient was qualified for conservative treatment. To exclude left atrial thrombus before redo procedure, transesophageal echocardiography was performed which visualized the presence of 9-mm atrial septal defect with left-to-right shunting, detecting right-to-left shunting using Valsalva maneuver. No significant valvular abnormalities were identified. The next day, pulmonary vein isolation for atrial fibrillation was performed. One month later, a control transthoracic echocardiogram (TTE) revealed hemodynamic significant left-to-right shunting with Qp/Qs 2.0 and high probability of pulmonary hypertension. Vascular surgery for arteriovenous fistula was successfully performed in October 2018. Subsequent TTE, performed a month later, confirmed no left-to-right shunting and no signs of pulmonary hypertension or diminishment of the right atrium. CONCLUSIONS Vascular access during catheter ablation for atrial fibrillation may result in arteriovenous fistula. This condition might affect right atrium pressure leading to increased diameter of previous puncture site at the interatrial septum, causing IASD with significant shunting. In this group of patients, arteriovenous fistula should be treated as soon as possible.

Overcoming Translational Barriers in Acute Kidney Injury: A Report from an NIDDK Workshop.

AKI is a complex clinical condition associated with high mortality, morbidity, and health care costs. Despite improvements in methodology and design of clinical trials, and advances in understanding the underlying pathophysiology of rodent AKI, no pharmacologic agent exists for the prevention or treatment of AKI in humans. To address the barriers that affect successful clinical translation of drug targets identified and validated in preclinical animal models of AKI in this patient population, the National Institute of Diabetes and Digestive and Kidney Diseases convened the "AKI Outcomes: Overcoming Barriers in AKI" workshop on February 10-12, 2015. The workshop used a reverse translational medicine approach to identify steps necessary to achieve clinical success. During the workshop, breakout groups were charged first to design feasible, phase 2, proof-of-concept clinical trials for delayed transplant graft function, prevention of AKI (primary prevention), and treatment of AKI (secondary prevention and recovery). Breakout groups then were responsible for identification of preclinical animal models that would replicate the pathophysiology of the phase 2 proof-of-concept patient population, including primary and secondary end points. Breakout groups identified considerable gaps in knowledge regarding human AKI, our understanding of the pathophysiology of AKI in preclinical animal models, and the fidelity of cellular and molecular targets that have been evaluated preclinically to provide information regarding human AKI of various etiologies. The workshop concluded with attendees defining a new path forward to a better understanding of the etiology, pathology, and pathophysiology of human AKI.