Biology subjects

Grace, A. A.

Publications and source records attributed to Grace, A. A..

3 recordsLinked to original sources

bioRxiv2018

Transcranial photoacoustic imaging of NMDA-evoked focal circuit dynamics in rat forebrain

Transcranial functional photoacoustic (fPA) voltage-sensitive dye (VSD) imaging promises to overcome current temporal and spatial limitations of current neuroimaging modalities. The technique previously distinguished global seizure activity from control neural activity in groups of rats. To validate the focal specificity of transcranial fPA neuroimaging in vivo, we now present proofs-of-concept that the results differentiate between low- and high-dose N-methyl-D-aspartate (NMDA) evoked neural activity in rat hippocampus. Concurrent quantitative EEG (qEEG) and microdialysis recorded real-time circuit dynamics and glutamate concentration change, respectively. We hypothesized that location-specific fPA VSD contrast would identify the neural dynamics in hippocampus with the correlation to NMDA evoked focal glutamate release and time-specific EEG signals. To test the hypothesis, we infused 0.3 to 3.0 mM NMDA at 2 l/min over 60 min via an implanted microdialysis probe. The dialysate samples collected every 20 min during the infusion were analyzed for focal changes in extracellular glutamate release. Transcranial fPA VSD imaging provided NMDA-evoked VSD responses with positive correlation to extracellular glutamate concentration change at the contralateral side of the microdialysis probe. The graded response represents the all-or-none gating system of the dentate gyrus (DG) in hippocampus. Quantitative EEG (qEEG) successfully confirmed induction of focal seizure activity during NMDA infusion. We conclude that transcranial fPA VSD imaging distinguished graded DG gatekeeping functions, based on the VSD redistribution mechanism sensitive to electrophysiologic membrane potential. The results suggest the potential future use of this emerging technology in clinics and science as an innovative and significant functional neuroimaging modality.

neuroscience↗

bioRxiv2017

Improved Outcome And Cost Effectiveness In Ablation Of Persistent Atrial Fibrillation Under General Anaesthetic

AimsOutcome of persistent atrial fibrillation (AF) ablation remains suboptimal. Techniques employed to reduce arrhythmia recurrence rate are more likely to be embraced if cost-effectiveness can be demonstrated. A single-centre observational study assessed whether use of general anaesthesia (GA) in persistent AF ablation improved outcome and was cost-effective.\n\nMethods292 patients undergoing first ablation procedures for persistent AF under conscious sedation or GA were followed. End points were freedom from listing for repeat ablation at 18 months and freedom from recurrence of atrial arrhythmia at one year.\n\nResultsFreedom from atrial arrhythmia was higher in patients who underwent ablation under GA rather than sedation (63.9% vs 42.3%, HR 1.87, 95% CI: 1.23 to 2.86, p = 0.002). Significantly fewer GA patients were listed for repeat procedures (29.2% vs 42.7%, HR 1.62, 95% CI: 1.01 to 2.60, p = 0.044). Despite GA procedures costing slightly more, a saving of {pound}177 can be made per patient in our centre for a maximum of 2 procedures if all persistent AF ablations are performed under GA.\n\nConclusionsIn patients with persistent AF, it is both clinical and economically more effective to perform ablation under GA rather than sedation.\n\nWhats New?O_LIThere is very little known regarding the clinical outcome of catheter ablation of AF under GA compared with sedation; to our knowledge there is one study only in paroxysmal AF and no studies examining cost effectiveness.\nC_LIO_LIThis study shows that in patients with persistent AF, it is both clinical and economically more effective to perform ablation under GA rather than sedation.\nC_LIO_LIThis study leads us to recommend the use of GA for the ablation of persistent AF. As PAF ablation is now increasingly being undertaken by single shot techniques which do not have the same requirements for analgesia and immobility, GA resources may be allocated for persistent AF ablation.\nC_LI

systems biology↗

bioRxiv2017

Ablation Of Complex Fractionated Electrograms Improves Outcome In Long Standing Persistent Atrial Fibrillation

PurposeThere is controversy and sparse data on whether substrate based techniques in addition to pulmonary vein isolation (PVI) confer benefit in the catheter ablation of persistent atrial fibrillation (AF), especially if long standing. We performed an observational study to assess whether substrate based ablation improved freedom from atrial arrhythmia.\n\nMethods286 patients undergoing first ablation procedures for persistent AF with PVI only, PVI plus linear ablation, or PVI plus complex fractionated electrogram (CFAE) and linear ablation were followed. Primary end point was freedom from atrial arrhythmia at one year.\n\nResultsMean duration of pre-procedure time in AF was 28+/-27 months. Freedom from atrial arrhythmia was higher with a PVI+CFAE+lines strategy then for PVI alone (HR 1.56, 95% CI: 1.04-2.34, p=0.032) but was not higher with PVI+lines. Benefit of substrate modification was conferred for pre-procedure times in AF of over 30 months. The occurrence of atrial tachycardia was higher when lines were added to the ablation strategy (HR 0.08, 95% CI: 0.01-0.59, p=0.014). Freedom from atrial arrhythmia at 1 year was higher with lower patient age, use of general anaesthetic (GA), normal or mildly dilated left atrium and decreasing time in AF.\n\nConclusionsIn patients with long standing persistent AF of over 30 months duration, CFAE ablation resulted in improved freedom from atrial arrhythmia. Increased freedom from atrial arrhythmia occurs in patients who are younger and have smaller atria, and with GA procedures. Linear ablation did not improve outcome and resulted in a higher incidence of atrial tachycardia.

systems biology↗