Dual Chamber Research Articles

AV nodal ablation in atrial fibrillation: long term outcomes

Abstract Background Ablation of the atrioventricular (AV) node, following the insertion of a permanent pacemaker, is a treatment option for symptomatic atrial fibrillation (AF) where rate control is poor, despite maximally tolerated pharmacological intervention or percutaneous AF ablation [1], and yet there is limited data on long-term outcomes. Purpose The purpose of this study is to investigate post AV node ablation follow up outcomes, including the incidence and timeframe of conversion of paroxysmal to persistent AF; incidence and timeframe of upgrade to biventricular pacemakers; and mortality. Methods This observational descriptive study looked at the post-procedure follow-up outcomes of patients who underwent AV node ablation at our centre between March 2015 and June 2019. Retrospective analysis of prospectively collected data was analysed. The demographics of the patients, including their age, gender, co-morbidities, pre-ablation left ventricular ejection fraction (LVEF) and medications were recorded. The follow up outcomes investigated included the change in LVEF, the proportion of patients whose AF converted from paroxysmal to persistent, the proportion of patients requiring upgrade to biventricular devices, and deaths within 6 months of ablation. Outcomes were compared between those who had a biventricular pacemaker pre-ablation and those who had single/dual chamber pacemakers. Results 296 patients with a mean age of 72.7± 8.5 years and a female to male ratio of 54.1% : 45.9% were included. 94 patients (31.8%) had paroxysmal AF pre- ablation. 51.6% of those who had paroxysmal AF pre-ablation converted to persistent AF over a median period of 3 years (interquartile range, 3 years). Among those who had a biventricular pacemaker pre-ablation, 56.5% of those with paroxysmal AF converted to persistent, compared to 47.4% of those with a dual pacemaker pre-ablation p=ns Among patients with dual chamber pacemakers, those who remained in paroxysmal AF post-ablation had a mean CHADVASC score of 3.2 (range of 1-6) compared to 3.7 (range of 2-6) in those whose AF converted to persistent (p=0.19). 9 patients (3%) died within less than 6 months of the procedure, with 1 patient dying within 6 days. 13% of the patients originally having a single or dual chamber pacemaker required an upgrade to a biventricular pacemaker over a median period of 1.25 years (interquartile range 1.1 years). All the patients who required an upgrade to a biventricular pacemaker had normal LVEF pre-ablation except for one patient who had mild LV impairment. Conclusions A significant proportion of patients with paroxysmal AF converted to persistent AF following AV node ablation and having a biventricular pacemaker did not offer benefit in keeping people in paroxysmal AF.A considerable number of people required an upgrade to biventricular pacemaker over a short time frame even though they had normal LVEF pre AV nodal ablation.

LIMITATIONS IN THE USE OF SUBCUTANEOUS DEFIBRILLATOR IN PATIENTS WITH LOW BODY MASS INDEX

Abstract Introduction Subcutaneous defibrillator is an effective and widely used tool in clinical practice but the presence of large fluctuations in the body mass index and the reduction of subcutaneous tissue may limit its application to all patients. Case Report In 2014, a 51–year–old woman underwent implantation of a dual–chamber transvenous defibrillator with left subclavian vein approach in secondary prevention for long Qt syndrome (LQT3). About 6 years after implantation she presented a ventricular lead breakage due to subclavian crush syndrome and was subjected to multiple inappropriate shocks due to lead failure. For this reason, the transvenous defibrillator was replaced with a single–chamber pacemaker for atrial stimulation and a subcutaneous defibrillator was implanted (Fig.1). In the following years the patient lost 14 kg and in the first months of 2022 she complained of the onset of stabbing pain in the precordial region near the upper face of the left sixth rib on the midclavicular line (Fig.2). Over the months, this symptomatology has become increasingly limiting and poorly responsive to normal analgesics but only to opiates; furthermore the pain has also occurred after a few weeks at the left parasternal level along the course of the distal portion of the subcutaneous catheter. For this reason, after discussing the case with the patient, we proceeded to implant a new transvenous lead via left subclavian vein and upgrade to a dual–chamber defibrillator. Subsequently, in the same operating session, the subcutaneous defibrillator was removed, finding only a modest traction resistance of the catheter in the parasternal area, resolved with the use of a 10 French introducer used as a sheet to debride the course of the same from the fibrotic adhesions (Fig .3). In the days following the procedure, the patient reported a progressive total disappearance of the pain symptoms. Reassessed after one year, the patient reports subjective well–being with total absence of chest pain and good quality of life. Conclusions The subcutaneous defibrillator represents an important resource for the management of the main ventricular arrhythmias, especially in patients with a high risk of infection and with a long life expectancy. The presence of a stable amount of subcutaneous tissue is a necessary condition to guarantee the tolerance of the lead over time and to avoid chronic pain situations that can lead to its removal.

CASE PRESENTATION: A COMPLEX CLINICAL SCENARIO IN A 43–YEAR–OLD MALE WITH DEVICE–RELATED COMPLICATIONS

Abstract A 43 yo male presented with an exposed pocket of his ICD in the right prepectoral and axillary region, along with total exposure of the lead electrodes up to the fixation sleeves.The patient, a known carrier of double–outlet right ventricle, underwent surgical correction. At the age of one, he received a dual–chamber pacemaker in the left prepectoral region due to AVB. Due to recurrent sustained ventricular tachycardias an ICD was implanted in the right prepectoral region, with removal of the left–sided pacemaker and concurrent abandonment of the ventricular pacing lead. In October 2019, he was admitted for a recurrence of pocket erosion.Device extraction was proposed but declined by the patient. Subsequently, he was referred to our institution for device removal. After heart team discussion, the patient was offered a transvenous lead extraction, with potential cardiothoracic surgical intervention if transvenous extraction proved to be challenging.An attempt was made to extract the leads using a transvenous approach. The procedure proceeded without complications, and the leads were released from adhesions up to the superior vena cava. However, there was an adhesion point at this location that was not overcome by mechanical dilation.Due to this limitation, a few days later, a cardiothoracic surgical intervention was performed to complete the lead wires‘ extraction using an invasive approach. In this context, a cardiac resynchronization device CRT–P was reimplanted in the left prepectoral region with epicardial electrodes. The patient underwent submuscular subclavian implantation of a SCID.The patient presented with a new pocket erosion of the CRT–P.Considering the high infection risk, It was therefore decided to implant a leadless device following electroanatomic mapping of the right ventricle, as there were surgical patches in the septal region. This approach aimed to identify the optimal anchoring site for the device. Subsequently, he will go extraction of the generator of the CRT–P.The decision to forgo biventricular stimulation was made, because of the elevated infectious risk.Complications associated with implantable devices pose an increasingly significant challenge in managing young patients with cardiac arrhythmias. Only through an integrated approach and proactive sharing of knowledge and expertise can we significantly improve clinical outcomes and the quality of life for this increasingly relevant population.

A PARTICULAR CASE OF CARDIAC ARREST

Abstract 88–year–old man with arterial hypertension, cognitive impairment, carrier of dual–chamber PM due to sinus node disease. Diagnosis of congenital long QT syndrome (LQT1) approximately 20 years ago during family screening (syncopal episodes in his son positive for LQT1), no history of syncope or major arrhythmias. In home therapy with mirtazapine and norvasc. He arrived in our cardiac intensive care unit for ACC on torsade de pointes trated with two cycles of CPR and 1 DC shock at 200 Joules with ROSC. On arrival ECG evidence of electrically induced ventricular rhythm, QTc 850 msec. On echocardiogram akinesia of the mid–basal segments of all the LV walls (takotsubo–like) with EF 25–30%. On coronary angiography non critical multivessel coronary disease. At laboratory tests increase of WBC, PCR and PCT, slight plateau movement of troponin, normal electrolytes. The patient underwent a chest CT scan with evidence of an inflammatory focus for which antibiotic therapy was started. Congenital long QT syndrome (LQTS) is an inherited condition characterized by prolongation of the QT interval (more than 450 ms in men and 460 ms in women), associated with repolarization abnormalities. There are three main forms transmitted via AD: LQT1, LQT2 and LQT3. The most common variant is LQT1 caused by a loss of function mutation in the KCNQ1 gene which causes a reduction in the outgoing potassium current during phase 3 of the action potential. In these patients, episodes of syncope caused by torsade de pointes, major arrhythmias and sudden cardiac death are frequent. Patients with LQTS should avoid taking drugs that can prolong the QT interval such as some antipsychotics, antidepressants (like mirtazapina that can cause QT prolongation, torsade de pointes, ventricular tachycardia and sudden cardiac death if administered at high doses or in patients with predisposing factors), antibiotics. Furthermore, there are various factors that can influence the QT prolongation: electrolyte alterations, physical stress, cerebrovascular events. The use of mirtazapine for a long period in association with takotsubo syndrome (probably triggered by underlying pneumonia) in a patient with LQTS, may have resulted in massive lengthening of the QT interval causing torsade de pointes and therefore ACC. During the hospitalization, mirtazapine was suspended and nadolol was introduced with a progressive reduction of the QT segment. No new arrhythmic events were recorded.

A VENTRICULAR TACHYCARDIA CASE NOT TREATABLE WITH TRANSCATHETER ABLATION DUE TO APICAL THROMBOSIS OF THE LEFT VENTRICLE RESOLVED WITH RADIOTHERAPY BASED ON THE NON–INVASIVE MAPPING SYSTE

Abstract The clinical case focuses on a 52–year–old man smoker, heavy alcohol consumer. In 2017 he began with sustained ventricular tachycardia (VT) effectively treated with DC–shock. The following ECG showed signs of anterior necrosis. Severe left ventricular (LV) dilatation, apical thrombosis and severe impairment of LV function were found on echocardiogram. Angiography was performed and LAD occlusion was found. Since of 68% necrosis of the LV at myocardial scintigraphy, no revascularization was performed. He underwent to a dual chamber ICD implantation and started oral anticoagulation therapy. In the following years recurrence of arrhythmic episodes, despite the optimization of antiarrhythmic therapy, led the patient to numerous hospitalizations. Unfortunately the persistence of the apical thrombosis, made transcatheter ablation NOT possible. The only chance for the patient remained stereotactic arrhythmia radioablation. But which area of the LV to highlight as responsible for the arrhythmia and how to program the radiotherapy treatment plan was a challenging problem. We proposed in March 2023 non–invasive mapping of arrhythmia using Cardioinsight. The patient performed heart high–resolution computed tomography (CT) for the anatomical reconstruction with precise spatial resolution of all LV aereas and surrounding structures. A 252–electrode vest is applied to the patient’s torso and connected to the system Cardioinsight. A programmed ventricular stimulation was performed using ICD inducing two VT morphologies. Through electroanatomical mapping we identified the mid LV antero–septal and infero–septal sites as target areas. Thanks to multidisciplinary team a personalized treatment plan was created to deliver an effective lesion in the target area and minimize exposure to nearby organs at risk. The treatment was generated, optimized and delivered by TrueBeam, lasted 3 minutes and no complications arose. The patient was quickly discharged in good clinical condition. After 3 months of clinical well–being he was hospitalized for a single episode of VT. Up to now no hospitalizations occurred. This treatment may represent a "bail–out" choice in patients with advanced heart failure with arrhythmic storm who have exhausted all other therapeutic options.

Studies on agar salt bridge based dual chamber microbial fuel cells using sludge and dustbin waste

Studies on agar salt bridge based dual chamber microbial fuel cells using sludge and dustbin waste

THROW YOUR LEAD OVER THE OBSTACLE: A CHALLENGING CRT UPGRADING

Abstract High percentage of right ventricular pacing could lead to pacing induced cardiomyopathy in a non–negligible proportion of patients. Cardiac resynchronization therapy upgrading could represent an option to improve ventricular function, reducing heart failure hospitalizations. A 82 yo male was admitted to hospital with symptomatic heart failure. He had history of complete AV block treated with dual chamber pacemaker implantation five years earlier following coronary artery bypass graft surgery, bioprosthetic aortic valve replacement and septal myectomy. He had also history of cardiac arrest occurred in the context of acute coronary syndrome treated with PCI so that ICD implant was not considered at that time, and two more HF hospitalizations in previous years. Progressive LVEF decline was documented since PM impantation until last echo showed severe left ventricular dysfunction (EF 20% from baseline EF 60%). The ECG showed sinus rhythm and wide paced QRS (206 ms) with 100% pacing percentage. A CRT device upgrading was planned. Baseline venography initially showed pervious axillary–subclavian left axis, but unfortunately the guidewire encountered a complete occlusion before entering the superior vena cava. Nevertheless, dye contrast injection documented the presence of a proximal collateral branch (fig A) having a vertical course in the thorax and reaching the lateral wall of the left ventricle with an extrapericardic course then entering the right heart through inferior vena cava. Using a IM 5Fr sheath (usually used by interventional cardiologists to cannulate internal mammary artery) we could reach this branch, inserting a guidewire and finally advancing a quadripolar lead (Fig B–C) which reached the lateral left ventricular wall. LV capture was confirmed when pacing from the three proximal poles, while the distal one caused phrenic nerve capture. The quadripolar lead was connected to the LV port of a three chamber PM along with previous implanted leads thus obtaining biventricular pacing. QRS paced was 50 ms shorter than baseline. No peri–procedural complications occurred. Lead–related venous occlusion might represent an obstacle to CRT upgrade requiring high technical expertise. The presence of a complete venous occlusion might cause procedural failure, particularly in hospitals without surgical facility. In this case, the presence of a collateral branch reaching the lateral wall of the left ventricle allowed to successfully complete the CRT upgrade.

INTERATRIAL BLOCK AS A FIRST CLINICAL PRESENTATION OF ATRIAL CARDIOMYOPATHY RELATED TO A NOVEL LMNA VARIANT: A CASE REPORT

Abstract Interatrial block (IAB) is a conduction delay in Bachmann’s bundle with a well–described association with structural heart disease, supraventricular arrhythmias, and cardiovascular events. We report the case of an asymptomatic 35–year–old man in whom the presence of IAB at electrocardiogram led to a comprehensive evaluation including speckle–tracking echocardiography, 24 h Holter monitoring, and genetic testing. Speckle–tracking echocardiography demonstrated a decrease in the longitudinal strain of interventricular septum, a typical feature of LMNA–related cardiomyopathy, and decreased indices of left atrial deformation. A diagnosis of cardiac laminopathy related to the frame shift variant c.1367 (p.Asn456Thrfs*24) of the LMNA gene was made. A dual–chamber implantable cardioverter defibrillator implantation was performed for the high risk of life–threatening ventricular tachyarrhythmias. This case demonstrates that IAB could be a rare presentation of a life–threatening laminopathy. Strain echocardiography is an essential tool to evaluate the deposition of fibrosis tissue in subclinical cardiomyopathies. Our report describes a novel variant of LMNA gene associated with a high risk of sudden cardiac death.

Deciphering characteristics of Macaranga tanarius leaves extract with electron shuttle-associated anti-inflammatory activity via microbial fuel cells, molecular docking, and network pharmacology

Recent studies have shown that the potential disease-treating characteristics of traditional Chinese medicine (TCM) were associated with electron-shuttling and bioenergy-stimulating capabilities. These redox-mediating characteristics are possibly even beneficial in the treatment of a wide variety of diseases ranging from viral infections to inflammations. This first-attempt study tended to investigate electron-mediating and bioenergy-extracting potentials of Macaranga tanarius leaves extract using dual chamber microbial fuel cells (MFCs) to unveil correlations of the anti-inflammatory potential for value-added applications. Network pharmacology and molecular docking studies were conducted with compounds identified to own electron-shuttling capabilities in the leaves extract to determine inhibitory activity with inflammation receptors. M. tanarius has shown significant bioenergy-stimulating characteristics, with the water extract having a 1.72±0.21-fold power generation. The underlying mechanism of action of M. tanarius was proposed via network pharmacology, suggesting how it targets specific proteins to inhibit potential diseases, such as kidney nephropathy. The findings revealed that major flavonoids bound to receptors via hydrogen bonds and π-interactions stabilizing the protein-ligand complex. Thus, exhibiting a high binding affinity with inflammation receptors, suggesting how it targets specific proteins to inhibit potential diseases.

Effect of different particle sizes on combustion characteristics of DCR engines

The ramjet engine has undergone rapid development in recent decades, and the dual combustion chamber ramjet (DCR) engine was proposed in the last century. Boron, with its high volumetric and gravimetric heating values, is one of the most attractive fuel additives for ramjet engines. However, due to the problem of low combustion efficiency, boron is difficult to achieve high efficiency combustion in practical applications. In order to investigate the combustion characteristics of boron-containing gas solid phase components in DCR engines, the Realizable k-ε model, finite rate/vortex dissipation model and boron particle King model ignition combustion calculation program were written. A three-dimensional full-scale two-phase flow numerical simulation was carried out in the combustion chamber of the DCR engine to calculate the effects of different particle sizes on the combustion characteristics. Through the analysis of the simulation results, the particle size affects the ignition time of boron particles and is positively correlated with the combustion efficiency, but with a non-linear growth. A smaller particle size can promote the ignition of boron particles, improve the solid phase combustion efficiency and achieve efficient combustion.

Sex-Specific Mitochondrial Bioenergetics Differences in Heart and Kidney Cortex

Rationale: Mitochondrial bioenergetics of different tissues have been studied widely, but their sex-specific differences have not been systematically studied. The goal of this study was therefore to investigate the sex-specific differences in mitochondrial respiration (oxygen consumption rate; OCR) and membrane potential (Δψ) in the heart and kidney cortex and to explore underlying mechanisms responsible for any observed differences. Methods: Mitochondria were isolated from adult male and female Sprague-Dawley rat heart and kidney cortex and were used to study their bioenergetics responses. Three different substrate combinations, namely, pyruvate+malate (PM), glutamate+malate (GM), and succinate in the presence of complex I inhibitor rotenone (SR) were used. This was followed by two different ADP addition protocols to determine how different substrates influence mitochondrial OCR and Δψ to ADP perturbations during oxidative phosphorylation (OxPhos) in male and female heart and kidney cortex. In one, a single saturated dose of ADP, while in the other, sequentially increasing doses of ADP were added to mitochondria in the presence of different substrates. Mitochondrial OCR was measured using a dual chamber Oroboros Oxygraph-2k Instrument and Δψ was measured using a spectrofluorometer and rhodamine-123 dye. From these measurements, OCR and Δψ alterations under different respiratory states and as functions of added ADP concentration were determined for different substrates and for both male and female rats. Results: Male and female mitochondria exhibited distinct respiratory patterns in the kidney cortex and heart with different substrates. In the kidney cortex, male mitochondria showed significantly higher OCR than female mitochondria when fueled with PM or SR. However, no significant sex differences in the OCR were observed when GM were used as substrates. In contrast, heart mitochondria exhibited negligible sex differences in the OCR for PM and SR, but significant differences emerged with GM, where female mitochondria displayed higher OCR than their male counterparts. Interestingly, sex-specific variations of Δψ in ADP-stimulated respiration were not apparent for either tissue or substrate when a single saturated dose of ADP was used. Instead, a trend similar to the OCR emerged when ADP was administered in gradually increasing concentrations. Conclusion: Heart and kidney cortex mitochondrial Δψ for males and females did not differ conclusively with the two ADP addition protocols. However, there were significant differences in the OCR of mitochondria from the heart and kidney cortex of males and females, depending on the respiratory substrate utilized. Males were found to have enhanced OCR in the kidney cortex, whereas females exhibited higher OCR in the heart. These observed sex-specific differences in the OCR could be attributed to differential regulation of mitochondrial metabolic pathways by respiratory substrates and sex hormones. NIH R01-HL151587. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Altered Hepatic Mitochondrial Bioenergetics and Oxidant Emission with Ischemia and Reperfusion

Rationale: Ischemia-reperfusion injury (IRI) is inevitable in liver transplantation (LT) which can be mitigated by normothermic machine perfusion (NMP) before LT. The current NMP liver viability criteria for LT mainly rely on bile production and perfusate lactate levels, factors that can also be affected by external variables such as NMP conditions and perfusate additives. Incorporating mitochondrial bioenergetic data could improve the predictive value of current NMP viability criteria for LT. Thus, the goal of this study was to evaluate mitochondrial oxygen consumption rate (OCR), membrane potential (Δψ), and H2O2 oxidant emission in control livers and in livers with IRI and to explore underlying mechanisms responsible for any observed differences. Methods: Healthy control livers and livers exposed to 60 minutes warm ischemia time (WIT) through in situ clamping of the portal vein and hepatic artery followed by 60 minutes reperfusion (IRI) were harvested from adult male Sprague-Dawley rats. Mitochondria from control and IRI livers were isolated using established protocols and assessed for their bioenergetics responses. Three different substrate combinations, namely, pyruvate+malate (PM), glutamate+malate (GM), and succinate were used, followed by addition(s) of ADP and the uncoupler FCCP. Two different ADP addition protocols were designed to determine how different substrates influence mitochondrial OCR, Δψ, and H2O2 emission during oxidative phosphorylation (OxPhos) between control and IRI conditions. In one protocol, a single saturated dose of ADP addition, and in the other, sequentially increasing doses of ADP additions were made following substrate addition. The OCR and Δψ were measured simultaneously using a dual chamber Oroboros Oxygraph-2k Instrument coupled to a fluorometer using the TMRM dye. The H2O2 emission was measured spectrofluorometrically using the amplex red and horseradish peroxidase assay. Results: The measured data show that the kinetics and effciency of OxPhos defining mitochondrial OCR and Δψ responses in the liver are negatively affected by IRI, characterized by enhanced H2O2 emission, in a substrate-dependent manner. Interestingly, the respiratory rates are higher when GM and succinate are utilized as substrates, whereas the use of PM shows comparatively lower respiration in both conditions. Control mitochondria exhibited higher respiratory rates than IRI mitochondria irrespective of the substrate utilized. The ADP-induced state 3 OCR in IRI mitochondria was 50% lower than that in control mitochondria resulting in doubling the duration of state 3 OCR. Similar differences were observed in Δψ for both ADP addition protocols. Compromised mitochondrial bioenergetics during IRI was observed using both single and sequentially increasing doses of ADP and was concomitant with a higher rate of H2O2 emission. Conclusion: This study provided novel quantitative data demonstrating the substrate specific changes in mitochondrial bioenergetics in hepatic IRI, which can be used to improve the NMP viability criteria for LT. The obtained bioenergetics and H2O2 emission data indicate that, during IRI, mitochondrial function is highly affected which may critically impact energy dependent metabolism and lactate/pyruvate ratio. NIH R01-HL151587. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Changes in hemodynamic parameters and atrial fibrillation risk in patients after permanent pacemaker implantation

Data on the development of left ventricular dysfunction after permanent pacemaker implantation are available. According to data from the DAVID (The Dual Chamber and VVI Implantable Defibrillator) study, it was shown that DDDR-paced patients had significantly more fatal events and HF deterioration cases requiring hospitalization. Similar were the results of the MOde Selection Trial (MOST), which poses serious questions to the cardiology community. For that reason it is important to understand how PPM implantation changes the hemodynamic parameters of the heart and what consequences this may have. On the one hand, asynchronous contraction of the paced heart and increase in AF risk with advancing age require active screening of asymptomatic paroxysms of tachyarrhythmias to promptly adjust therapy. On the other hand, minimizing the rate of ventricular pacing through proper programming of the devices should not be overlooked. Recently, various biomarkers have been validated to select high-risk patients in which the therapeutic strategy can be modulated on time.

Wastewater remediation and bioelectricity generation in dual chambered salt bridge microbial fuel cell: A mini‐review

AbstractThe purpose of this article is to assess the feasibility analysis of microbial fuel cells (MFCs), particularly in the configuration of dual chamber salt bridge microbial fuel cell (DCSB‐MFC), as a promising approach for simultaneous bioelectricity generation and wastewater remediation. The application of a salt bridge presents an economically viable alternative to the use of a proton exchange membrane, which is known for its high cost, in the construction of MFCs. This arrangement has been demonstrated to offer significant benefits in terms of enhancing the performance of new elements and evaluating operational parameters. However, it also encounters issues related to the total internal resistance (Rint) of the MFCs as well as power density (P). In addition, it has been found that traditional packing materials such activated carbon and gravel demonstrate poor permeability, internal resistance, and slow biofilm growth. Furthermore, there is a necessity to search for electrodes that possess high resistance to corrosion and are cost‐effective to achieve optimal bioelectricity generation. Therefore, this article aims to emphasize the research areas that require attention. By addressing these areas, the actual implementation of this configuration can be brought closer to practical implementation.

Enhanced Pollutant Removal and Power Generation in Wastewater Using Microbial Fuel Cells: A Pathway to Sustainable Energy

Microbial fuel cells (MFCs) demonstrate potential for wastewater treatment while concurrently generating renewable electricity. This investigation aimed to enhance current output by optimising the operational parameters of a dual-chamber MFC. The study utilized a household-constructed dual-chamber MFC with an agarose gel-based proton exchange membrane to enhance current generation in municipal wastewater treatment. The MFC effectively reduced the chemical oxygen demand (COD) from 291 mg/L to 134 mg/L, demonstrating substantial degradation of organic contaminants. An increase in total dissolved solids (TDS) and electrical conductivity (EC) was observed, indicating material decomposition and ionization. The pH level decreased slightly from 7.7 to 7.3, presumably due to hydrogen ion movement during electrochemical processes. Through optimisation of wastewater volume and operational conditions, a peak current production of 1124 μA was achieved. Future studies should focus on refining operational parameters and examining the catalytic properties of the cathodic microbial community to enhance MFC performance and scalability. These findings highlight the dual chamber MFC’s potential as a sustainable solution for concurrent wastewater treatment and renewable energy production, establishing a foundation for scalable applications in environmental remediation and clean energy generation.

The Use of Next Generation Sequencing to Detect Early Implant Infections: The Future of Microbiology and Targeted Antibiotic Treatment

Abstract Goals/Purpose The presence of fluid around foreign bodies, particularly breast implants, is a well-established phenomenon; However scant data exists regarding the composition of this fluid. The difficulty in studying this fluid arises from the lack of safe access to aspirate fluid post-breast augmentation, and by the loss of sterility once fluid exits the body via a drain bulb as traditionally placed during breast reconstruction. Our innovative breast reconstruction approach utilizes a drainless technique with a dual chamber tissue expander (TE) in the pre-pectoral plane, offering a unique avenue to sterilely aspirate peri-implant fluid through a percutaneous drainage port. In this study, we employ Next Generation Sequencing (NGS), utilizing polymerase chain reaction technology, to discern the composition of microbial DNA within peri-prosthetic breast implant fluid. NGS, known for its precision and cost-effectiveness, circumvents the biases inherent in traditional culture methods. By integrating this cutting-edge technology with our breast reconstruction methodology, we sought to study peri-prosthetic breast implant fluid to better understand when implant infections arise and if peri-prosthetic fluid could detect infections before clinical symptoms arise. Methods/Technique This is a single surgeon, prospective study of patients undergoing mastectomy, followed by pre-pectoral, drainless, TE reconstruction. Peri-prosthetic fluid was collected through the TE drainage port in the OR immediately after closure, at 1 week post op, and 3 weeks post op. This fluid was sent for traditional culture and NGS. Patients were observed for signs of infection, antibiotics, return to OR, or implant loss. Results/Complications 33 breasts from 20 patients were included. Patients had a mean age of 50 years. The average length of drainage was 21 days post-operative, with a mean of 131 cc of fluid drained per breast per week. Eight breasts had concern for skin necrosis. In 25 breasts (76%), complete sterility was achieved at the end of the case with no NGS detection of microorganisms in the initial peri-implant fluid sample. However, NGS detected microorganisms in the initial sample in 8 breasts (24%). In 5 of these 8 breasts, microorganisms were cleared by the 1-week sample and another 2 cleared by 3 weeks. The remaining 1 breast continued to have positive NGS and developed clinical signs of infections by week 2, which were not picked up by traditional culture until week 3. One breast with skin necrosis developed a positive NGS at week 3 and clinical signs of infection at week 4. No other clinical infections were seen throughout the study. Conclusion We are one of the first groups to demonstrate the ability to achieve peri-implant sterility at the time of implant insertion in the operating room. This could have significant implications for understanding the necessity of peri-operative antibiotics following breast implant placement. Our investigation into the microbial composition of ostensibly "sterile" peri-prosthetic breast implant fluid provides insight into when microorganisms arise and when they become clinical infections. These promising preliminary results suggests that peri-prosthetic fluid monitoring through Next-Generation Sequencing (NGS) holds significant potential in preemptively detecting implant infections before the onset of clinical symptoms, thereby reducing infection rates. Furthermore, our findings open avenues for targeted antibiotic therapy, contributing to the imperative goal of antibiotic stewardship. Ongoing work is beginning to explore the impact of microorganisms within the fluid on breast capsule formation, as we strive to enhance our understanding of breast implants and infections.

Internal Mammary Artery Graft Flow Steal by a Large Dialysis Arteriovenous Fistula Characterized by Electrical Storm

Background: Steal syndrome describes a condition in which a dilated vessel distal to a smaller artery attempts to compensate for decreased blood flow by “stealing” from the smaller artery. Steal syndrome is not uncommon and can be seen in certain physiologic and pathologic states. The classic example is an occluded atherosclerotic coronary artery resulting in a misdirection of blood flow into the open channels that have developed over time resulting in downstream ischemia. Case Report: A 66-year-old male fourteen years post 4-vessel coronary artery bypass grafting using his left internal mammary artery to bypass a stenotic segment of the left anterior descending artery, along with three saphenous venous conduits to the right coronary artery. He also had a stent placement by PCI. He was on dual antiplatelet therapy with aspirin and clopidogrel. An electrophysiology study revealed inducible VF and he underwent implantation of a dual chamber ICD 9 months prior to presentation. He experienced an unprovoked fall at home and a workup revealed the flow volume through the patient’s fistula increased to such a degree that the patient developed a steal syndrome from his left internal mammary artery graft. In addition, went into a state of electrical storm caused by ischemic damage to cardiac tissue distal to the graft. By ligating the fistula, the patient’s steal syndrome resolved and he did not suffer further ventricular arrhythmias. Conclusion: Both coronary bypass grafting and fistula formation are common and necessary interventions and providers should take care to monitor for interactions between these proposed interventions to best serve their patients without causing additional harm. Increased vascular flow through any portion of the body can induce a steal syndrome from an upstream region. Patients who undergo arteriovenous (AV) fistula placement may develop a steal syndrome from ipsilateral bypass grafts.

Development and characterization of discontinuous atmospheric pressure interface - Dual pressure chamber miniature mass spectrometer

Miniaturized mass spectrometers have become increasingly prevalent for real-time detection and analysis, owing to their compact size and portability. The pursuit of performance enhancement in these instruments is a pivotal objective within the domain of mass spectrometry miniaturization. This study introduces a novel miniature mass spectrometer featuring a discontinuous atmospheric pressure interface and a dual pressure chamber. Compared to conventional single-chamber, discontinuous sampling interface mass spectrometers, the newly developed instrument demonstrates a more than tenfold improvement in detection efficiency. This significant enhancement is achieved without the need for complex control of switch coupling time series, thereby streamlining the circuit design and improving the instrument's fault tolerance. Furthermore, by capitalizing on the benefits of discontinuous sampling, the instrument reduces the operational pressure relative to traditional continuous sampling in differential pressure vacuum chambers. It accommodates larger inlet capillary (0.38 mm) and skimmer (0.5 mm) diameters, leading to a ninefold increase in response strength for risperidone and lowering the detection limit to 0.5 ppb. The instrument's capacity for rapid drug detection, along with enhanced resolution and detection limits, underscores its potential utility. Additionally, it facilitates the use of smaller mechanical pumps, significantly diminishing both the instrument's volume and power consumption. This presents a promising avenue for further miniaturization of mass spectrometers.

Performance of Dual Chamber Microbial Fuel Cells with Waste Water for Power Production and Treatment

Abstract: Dual-chamber microbial fuel cells (MFCs) have garnered significant attention in recent years due to their promising potential for sustainable energy generation from organic waste. This review provides a comprehensive overview of the advancements, challenges, and future prospects of dual-chamber MFC technology. The paper begins with an introduction to the principles of microbial fuel cells and the rationale behind the dual-chamber configuration. It discusses the design considerations including electrode materials, membrane selection, and reactor configurations, highlighting recent innovations aimed at enhancing performance and scalability. Key advancements in dual-chamber MFCs are reviewed, focusing on improvements in power output, microbial community dynamics, and substrate utilization. Strategies such as microbial enrichment, biofilm engineering, and electrode modifications are discussed in detail, showcasing their impact on MFC performance and stability. Furthermore, the review explores the application of dual-chamber MFCs in various fields including wastewater treatment, bioenergy productions.

Improving wave energy conversion performance of a floating BBDB-OWC system by using dual chambers and a novel enhancement plate

In this study, a novel floating dual-chamber backward bent duct buoy oscillating water column (BBDB-OWC) wave energy converter (WEC) is introduced, featuring a horizontal plate at the bottom of the front chamber to act as an enhancement plate. A three-dimensional computational fluid dynamics (CFD) model is developed and validated by comparing its results with existing experimental measurements. The validated model is employed to investigate the hydrodynamic performance and power generation characteristics of the dual-chamber BBDB-OWC WEC under various conditions, including variations in the length of the horizontal plate (lp/lf) and different regular wave conditions. Key performance metrics, including peak to average ratio of power (PTARP), wave energy capture width ratio (ξtotal), and its wave period respond bandwidth (indicated by Pξtotal > 0.5 and Pξtotal > 0.7), are analyzed and compared with those of a traditional single-chamber BBDB-OWC WEC. The results reveal that, compared to the single-chamber WEC, the dual-chamber WEC with a specific horizontal plate length reduces the average PTARP from 2.88 to a minimum value of 1.82 for lp/lf = 0.5, improves the average ξtotal from 0.55 to a maximum value of 0.64 for lp/lf = 2.5, and increases Pξtotal > 0.5 and Pξtotal > 0.7 from 71 % and 14 % to maximum values of 86 % and 43 % for lp/lf = 2.5, respectively. An explanation for these observations is also provided in the context of structure motion and flow fields.