Constructing custom-made radiotranscriptomic signatures from CT angiograms: an application in COVID-19 vascular inflammation

Background

Advances in computational methodologies have enabled processing of large datasets originating from imaging studies. However, most imaging biomarkers suffer from a lack of direct links with underlying biology, as they are only observationally correlated with pathophysiology.

Purpose

To develop and validate a novel AI-assisted image analysis platform, by applying quantitative radiotranscriptomics that quantifies cytokine-driven vascular inflammation from routine CT angiograms (CTA) performed as part of clinical care in COVID-19.

Methods

We used this platform to train the radiotranscriptomic signature C19-RS, derived from the perivascular space around the aorta and the internal mammary artery in routine chest CTAs, to best describe cytokine-driven vascular inflammation, defined using transcriptomic profiles from RNA sequencing data from human arterial biopsies (A). This signature was validated externally in 358 clinically indicated CT pulmonary angiograms from patients with or without COVID-19 from 3 different geographical regions.

Results

First, 22 patients who had a CTA before the pandemic underwent repeat CTA <6 months post COVID-19 infection (B). Compared with 22 controls (matched for age, gender, and BMI) C19-RS was increased only in the COVID-19 group (C). Next, C19-RS was calculated in a cohort of 331 patients hospitalised during the pandemic, and was higher in COVID-19 positives (adjusted OR=2.97 [95% CI: 1.43–6.27], p=0.004, D). C19-RS had prognostic value for in-hospital mortality in COVID-19, with HR=3.31 ([95% CI: 1.49–7.33], p=0.003) and 2.58 ([95% CI: 1.10–6.05], p=0.028) in two testing cohorts respectively (E, F), adjusted for clinical factors and biochemical biomarkers of inflammation and myocardial injury. The corrected HR for in-hospital mortality was 8.24 [95% CI: 2.16–31.36], p=0.002 for those who received no treatment with dexamethasone, but only 2.27 [95% CI: 0.69–7.55], p=0.18 in those who received dexamethasone subsequently to the C19-RS based image analysis, suggesting that vascular inflammation may have been a therapeutic target of dexamethasone in COVID-19. Finally, C19-RS was strongly associated (r=0.61, p=0.0003) with a whole blood transcriptional module representing dysregulation of coagulation and platelet aggregation pathways.

Conclusion

We present the first proof of concept study that combines transcriptomics with radiomics to provide a platform for the development of machine learning derived radiotranscriptomics analysis of routine clinical CT scans for the development of non-invasive imaging biomarkers. Application in COVID-19 produced C19-RS, a marker of cytokine-driven inflammation driving systemic activation of coagulation, that predicts in-hospital mortality and identifies people who will have better response to anti-inflammatory treatments, allowing targeted therapy. This AI-assisted image analysis platform may have applications across a wide range of vascular diseases, from infections to autoimmune diseases.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): EPSRC, British Heart Foundation, NIHR

Automated deep learning quantification of epicardial adiposity on cardiac CT predicts atrial fibrillation risk immediately following cardiac surgery and long-term

Introduction

Epicardial adipose tissue (EAT) is a visceral fat deposit within the pericardial sac which surrounds the heart myocardium and coronary arteries. The automated quantification of EAT volume is possible from routine CCTA scans via a deep-learning approach. The use of automated EAT quantification for the assessment of atrial fibrillation (AF) risk in the post-operative period, and longer-term, has not been previously investigated.

Purpose

To apply a deep-learning approach for automated segmentation of EAT from routine CCTA scans to assess the immediate post-operative and long-term risk of AF conveyed by EAT.

Methods

A deep-learning automated EAT segmentation tool using a 3D Residual-U-Net neural network architecture for 3D volumetric segmentation of CCTA data was created and trained on over 2800 consecutive CCTA performed as part of clinical care in patients with stable chest pain from 2015 onwards within the European arm of the Oxford Risk Factors And Non Invasive Imaging (ORFAN) Study. External validation in 817patients demonstrated excellent correlation between machine and human expert (CCC = 0.972). The prognostic value of deep-learning derived EAT volume was assessed in the AdipoRedOx Study (n=253; UK patients undergoing cardiac surgery) against both immediate in-hospital outcomes and longer-term outcomes from UK-wide NHS data, with adjustment for AF risk factors.

Results

There were 97 cases of new-onset AF in the immediate post-operative period (38.3%). EAT volume was found to be an independent predictor of post-operative AF regardless of body mass index. Utilising the median EAT volume as the cut point, the adjusted hazard ratio (HR [95% CI]) for risk of new-onset post-operative AF in-hospital was 1.56 [1.09–3.85], p&lt;0.01 (Figure 1A). In receiver-operator characteristic analysis EAT volume added significant incremental prognostic power for the discrimination of in-hospital post-operative AF over a traditional risk factor model ΔAUC=0.101, p&lt;0.01 (Figure 1B).

Over a median follow-up period of 89 months there were 48 unique cases (19%) of confirmed AF found in nation-wide NHS hospital episode statistics data for the AdipoRedOx cohort. EAT volume was found to be a significant independent predictor of long-term AF. Utilising the median EAT volume as the cut point, the adjusted HR for risk of new-onset long-term AF following cardiac surgery was 1.25 [1.08–3.17], p&lt;0.01 (Figure 1C).

Conclusions

Automatically segmented EAT volume measured using a deep learning network predicts risk of both short-term new onset AF following cardiac surgery, and long-term risk of AF in the 7 years following the surgery independently of BMI and AF risk factors. This suggests that EAT is a potent mediator of AF risk in the post cardiac surgery setting.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation - TG/19/2/34831EU Commission - 965286

Adipose tissue derived ceramides regulate myocardial redox state and predict cardiovascular outcomes

Background

Obesity is linked to both dysfunctional adipose tissue (AT) and heart failure, but the exact mechanisms mediating these associations are unknown. Although ceramides biosynthesis is dysregulated in obesity, their role as mediators of obesity-induced myocardial dysfunction is unclear.

Purpose

We investigate the causal role of AT-derived ceramides in the regulation of myocardial redox state and explore their role in predicting cardiovascular outcomes.

Methods

The study population included a total of 880 patients undergoing cardiac surgery. A panel of 20 sphingolipids was measured in plasma as well as in biopsies of subcutaneous AT (ScAT), thoracic AT (ThAT) and epicardial AT (EpAT) and their secretome, obtained from a subgroup of n=48. Myocardial redox state was measured using lucigenin chemiluminescence and the contribution of NOXs, uncoupled nitric oxide synthases and mitochondrial oxidases in O2•– production was quantified. The cohort was followed up for a median of 8.3 years. Genome-wide genetic analysis was done using the UK Biobank array. A total of 99,524 SNPs within 50kb of 110 genes involved in sphingolipid biosynthesis were analysed to identify genetic variants that could predict CVD outcomes using cis-Mendelian Randomisation. The underlying mechanisms were then explored further, using differentiated H9c2 cardiomyocytes in vitro and human right atrial tissue ex vivo.

Results

The production and secretion of C16:0-ceramide (CerC16) was higher in visceral AT (EpAT and ThAT) compared to ScAT (p&lt;0.0001). Patients with high plasma levels of CerC16 and its derivative C16:0-glucosylceramide (GlcC16) had higher myocardial O2•– production vs those with low/int. levels (p&lt;0.05 for both) (A). To test the causality of this association, we performed a targeted single-SNP analysis for the genetic prediction of GlcC16 levels demonstrating that rs112572487, an intronic variant in UGCG (an enzyme that catalyses glucosylceramide formation from ceramides), was the top hit (B). Indeed, those with the rs112572487 minor allele (G) displayed significantly increased myocardial NOX-derived O2•– (C) and plasma GlcC16 levels (D) vs those without. Exogenous CerC16 (20nM) induced NOX-derived O2•– production in H9c2 cardiomyocytes, an effect prevented by the UGCG inhibitor D-PDMP (E), suggesting that GlcC16 is a modifiable regulator of myocardial NOX-O2•–. Importantly, high plasma GlcC16 levels were associated with a higher risk of cardiac death and/or heart failure (adj. HR=2.128 [95% CI: 1.101, 4.115], p=0.025, for high vs low/int. levels), a relationship also seen with rs112572487 (F).

Conclusions

We demonstrate for the first time, that AT-derived ceramides are causally related with dysregulated myocardial redox signalling and adverse cardiovascular disease outcomes in patients with advanced atherosclerosis. As such, GlcC16 may be an important therapeutic target for the prevention and treatment of cardiovascular complications in obesity and diabetes.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): The British Heart FoundationBritish Heart Foundation Chair Award

Automated quantification of epicardial adipose tissue on CCTA via deep-learning detection of the pericardium: clinical implications

Background

Epicardial adipose tissue (EAT) is a visceral fat deposit within the pericardial sac which surrounds the heart myocardium and coronary arteries. EAT volume has been demonstrated to be strongly associated with the development and prognosis of cardiovascular diseases, but its measurement is subjective and challenging in practice.

Purpose

To develop a deep-learning approach for automated segmentation of EAT from routine CCTA scans, that could assist clinical interpretation of CCTA.

Methods

A deep-learning method using a 3D Residual-U-Net neural network architecture for 3D volumetric segmentation of CCTA data was created. The network was trained on a diverse sample of 1900 CCTAs, each manually segmented by a single expert, drawn from the UK sites of the Oxford Risk Factors And Non-invasive imaging (ORFAN) Study. Three iterations of feedback learning were used to fine tune the algorithm for the segmentation of the whole heart within the bounds of the pericardium. In each iteration, the machine analysed sets of 100–250 unannotated CCTAs unseen by the machine which were then corrected by experts. EAT volumes were calculated by automated thresholding of adipose tissue (−190HU through −30HU) from within the bound of the pericardial segment (Figure 1). The network was then applied to 817 unseen CCTAs from US sites of the ORFAN Study. These scans were also segmented for ground truth by two experts blind to all other data. Comparisons between machine vs expert total pericardial volume and EAT volume were made using Lin's concordance correlation coefficient (CCC). The algorithm was then applied externally in 1588 CCTAs from the SCOTHEART trial (UK), and the EAT volume was automatically calculated for each case. Cross-sectional associations between standardised EAT volumes and prevalent AF and CAD were performed.

Results

Within both the internal (UK ORFAN sites) and external (USA ORFAN sites) validation cohorts correlation between human and machine segmented total pericardium and EAT was excellent, with CCC of 0.97 for both volumes (external validation cohort shown in Figure 2A). Utilising SCOTHEART CCTAs with automatically segmented EAT volumes, a multivariable-adjusted logistic regression model accounting for risk factors of age, sex, BMI, hypertension, diabetes mellitus, valvular disease, and previous heart surgery found that EAT volumes were significantly associated with prevalent AF, with odds ratio (OR) per 1 SD increase of EAT volume of 1.20 (95% CI, 1.06 to 1.44; P=0.03). A similar model for prevalent CAD, adjusted for age, sex, BMI, hypertension, non-HDL cholesterol, diabetes mellitus, and coronary artery calcium score resulted in an OR per 1 SD increase of EAT volume of 1.26 (95% CI, 1.10 to 1.45; P=0.001) (Figure 2B).

Conclusion

Highly accurate, reproducible, and instantaneous EAT volume quantification is possible utilising deep-learning detection of the whole human heart within the pericardial sac.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): British Heart FoundationNational Institute for Health Research - Oxford University Hospitals Biomedical Research Centre Figure 1Figure 2

Direct effects of canagliflozin on human myocardial redox signalling: a novel role for SGLT1 inhibition

Background

Recent clinical trials have demonstrated a role for sodium glucose cotransporter 2 (SGLT2) inhibitors in improving cardiovascular outcomes in heart failure patients, but the underlying mechanisms remain unknown. We investigated the direct effects of canagliflozin, a non-selective SGLT1/SGLT2 inhibitor on myocardial redox signalling in humans.

Methods

Study 1 included 364 patients undergoing cardiac surgery. Human right atrial appendage biopsies, obtained during surgery, were used to quantify the sources of superoxide (O2.-) and the gene expression of inflammation, fibrosis and myocardial stretch markers. In Study 2, myocardial biopsies from 51 patients were used ex vivo to study the direct effects of canagliflozin on O2.- generation and understand its role in controlling the activity of NADPH-oxidases and uncoupled nitric oxide synthase (NOS). Finally, we used differentiated H9C2 and human primary cardiomyocytes (hCM) to further characterise the key regulatory mechanisms (Study 3).

Results

SGLT1 was abundantly expressed in the human myocardial biopsies and hCM whilst SGLT2 was barely detectable. SGLT1 expression levels were positively correlated with basal O2.- production and the expression of natriuretic peptides, proinflammatory cytokines and pro-fibrotic markers in human myocardial biopsies from study 1. Incubation of human myocardium with canagliflozin significantly reduced basal and NADPH-oxidase-derived O2.- via AMP kinase (AMPK)-mediated suppression of GTP-activation and consequent reduction of membrane translocation of Rac1, an NADPH-oxidase subunit. This resulted in reduced oxidation and increased bioavailability of tetrahydrobiopterin, the nitric oxide synthase (NOS) co-factor essential for enzymatic coupling, leading to improved NOS coupling. These findings were replicated in hCM, where canagliflozin was shown to regulate AMP/ATP ratio, which could be upstream of AMPK activation. The effects of canagliflozin were significantly attenuated by knocking-down SGLT1 in hCM. Transcriptional profiling of hCM treated with canagliflozin revealed that canagliflozin had striking effects on myocardial redox signalling, causing suppression of apoptotic and inflammatory pathways in the human heart.

Conclusions

We demonstrate for the first time in humans that canagliflozin suppresses myocardial NADPH-oxidase activity and improves NOS coupling through an SGLT1/AMPK/Rac1-mediated pathway, leading to global anti-inflammatory and anti-apoptotic effects in the human myocardium. These findings provide a mechanistic basis for the beneficial effects of SGLT1/2 inhibitors in patients with heart failure.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): 1. British Heart Foundation (FS/16/15/32047 and PG/13/56/30383 to CA, CH/16/1/32013 to KC, and Centre of Research Excellence award RG/13/1/30181), 2. The Japanese Heart Rhythm Society-European Heart Rhythm Association fellowship grant sponsored by Biotronik.

Real world cost and health outcomes of patients presented with chest pain in England: which is the most cost-effective first-line test?

Background

The National Institute for Health and Care Excellence (NICE) updated their guidance for the management of patients with stable chest pain and recommended that all patients undergo computed tomography coronary angiography (CTCA). This update has sparked a great deal of debate, and was followed by upgrade of CTCA into a Class I indication in the recent ESC guidelines. The cost-effectiveness of using CTCA as first line investigation is still unclear.

Purpose

To describe the current clinical pathway of patients with stable chest pain presented to outpatient clinics, assess the compliance with the updated NICE guideline, and explore the costs and health outcomes of different non-invasive diagnostic tests in real-world clinical setting.

Methods

We used data of 4,297 patients who attended chest pain clinics in Oxford between 1 January 2014 and 31 July 2018. Data included clinical presentation (e.g. age and previous cardiovascular conditions), diagnostic tests, outpatient visits, hospitalization, and hospital mortality and was compared between 6 alternative first-line diagnostic tests. Multinomial regressions were performed to estimate the probability of receiving each alternative and the associated cost after adjusting for clinical presentation. A decision tree was developed to describe the clinical pathway for each alternative first-line diagnostic in terms of subsequent diagnostic tests and treatments and to estimate the associated costs and life days.

Results

The proportion of patients who received CTCA as first line diagnostic test increased from 1% in 2014 to 17% in 2018, while the publication of the updated NICE guidelines in 2016 led to a threefold increase in this proportion. CTCA is less likely to be provided as a first-line diagnostic to patients who are younger age, males, smokers, and have angina, PVD, or diabetes. The standardised rate of hospital admission was the lowest in the exercise ECG cohort (0.35 admissions per 1,000 life-days) followed by the CTCA cohort (0.40 admissions per 1,000 life-days) while the latter cohort had the lowest standardised rate of cardiovascular treatment (2.74% per 1,000 life days). Stress echocardiography and MPS were associated with higher costs compared with CTCA, other ECG, and exercise ECG after adjusting for clinical presentation and days of follow-up. CTCA is the pathway most likely to be cost-effective, even compared to exercise ECG, while the other diagnostic alternatives are dominated (i.e. they cost more for less life-days).

Conclusions

Currently, the updated NICE guidelines for stable chest pain are implemented only to a fifth of the cases in England. Our findings support existing evidence that CTCA is the most-cost effective first-line diagnostic test for this population. Hopefully, this will inform the debate around the implementation of the guidelines and help commissioning and clinical decision processes worldwide.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): National Institute of Health Research Oxford Biomedical Research Centre

P6267Novel direct effects of SGLT2 inhibitor, Canagliflozin, on myocardial redox state in humans

Background

Sodium glucose cotransporter 2 (SGLT2) inhibitors are antidiabetic drugs that control plasma glucose levels by inhibiting reabsorption of glucose in kidney. Recent clinical trials have suggested a class effect of SGLT2 inhibitors in preventing hospitalization due to heart failure. However, the underlying mechanism has not been fully elucidated.

Purpose

We investigated the direct effect of the SGLT2 inhibitor, Canagliflozin (Cana), on myocardial redox state in humans.

Methods

The study included 48 patients undergoing cardiac surgery. Fresh myocardial tissues were incubated ex vivo with or without Cana and then used for superoxide quantification and Western immunoblotting. NADPH-oxidases activity was evaluated with NADPH 100μM stimulation, while nitric oxide synthase (NOS) coupling was assessed by using N(ω)-nitro-L-arginine methyl ester (L-NAME, a NOS inhibitor). A human cardiomyocyte (HCM) cell line was also used for in vitro validation of the effects of Cana on myocardium.

Results

Ex vivo incubation of myocardium with Cana significantly reduced baseline (A) and NADPH-oxidase-derived O2·− (B) and improved NOS coupling reflected by positive L-NAME delta O2·− values (C). Regulation of NADPH-oxidases activity by Cana was found to result from reduced GTP-activation (D) and consequent membrane translocation (E) of Rac1, a key subunit of NADPH-oxidases. Cana also reduced tetrahydrobiopterin (BH4) oxidation, increasing its bioavailability (F), which is a key mechanism to improve NOS coupling. Incubation with Cana enhanced phosphorylation of AMPK, and the downstream signalling, ACC (not shown). Additional Compound C, which is inhibitor of AMPK, significantly reversed these effects of Cana (A, B, C, D, E, F). These findings were replicated in HCM (not shown). In line with these, Cana increased the ADP/ATP ratio of cytoplasm in HCM, which could provide an upstream mechanism for AMPK activation.

Conclusions

We demonstrate for the first time in humans, that Cana suppresses myocardial NADPH-oxidases activity and improves NOS coupling through an AMPK-mediated pathway. This could be an underlying mechanism for the cardioprotective effects of SGLT2 inhibitors.

2161Redox-mediated PKA-RIalpha localisation to the lysosome inhibits myocardial calcium release and robustly reduces myocardial injury

Background

Kinase oxidation is a critical signalling mechanism through which changes in the intracellular redox state alter cardiac function. In the myocardium, type-1 protein kinase A (PKARIα) can be reversibly oxidised, forming interprotein disulphide bonds within the holoenzyme complex. However, the effect of PKARIα oxidation on downstream signalling in the heart, particularly under states of oxidative stress, remains unexplored.

Purpose

To determine the direct functional consequences of PKARIα oxidation in the heart and investigate their impact on ischaemia/reperfusion (I/R) injury.

Methods and results

Experiments using the AKAR3ev FRET biosensor in murine left ventricular (LV) myocytes and Fluorescence Recovery After Photobleaching (FRAP) of GFP-tagged wild-type (WT) and mutant RIα proteins expressed in RIα-null fibroblasts showed that PKARIα oxidation does not increase the kinases' catalytic activity, but enhances its binding to A-kinase anchoring proteins (AKAP; n=30–39/N=3, p<0.01). Super-resolution microscopy revealed localisation of oxidised PKARIα to lysosomes in WT myocytes, which was completely absent in “redox dead” Cys17Ser PKARIα knock-in mice (KI; panel A; n=38–41/N=3, p<0.01) and reduced when AKAP binding was prevented using the RIAD disruptor peptide (30.6±5.1% reduction; n=35–37/N=3, p<0.01).

Displacement of PKARIα from lysosomes resulted in spontaneous sarcoplasmic reticulum calcium release and dramatic calcium oscillations in KI LV myocytes (panel B), which were preventable by ryanodine receptor blockade (1 mM tetracaine; n=14, p<0.01), acute depletion of endolysosomal calcium stores (100 nM bafilomycin; n=7; p<0.01), or lysosomal two-pore channel inhibition (5 μM Ned-19; n=9; p<0.05).

I/R (secondary to cardiopulmonary bypass) was found to induce PKARIα oxidation in the myocardium of patients undergoing cardiac surgery (panel C; n=18, p<0.05). Absence of this response in KI mouse hearts resulted in 2-fold larger infarcts (p<0.01) and a concomitant reduction in LV contractile recovery (final LVDP of 55.9±8.6 vs 82.5±7.1 mmHg in WT; n=7–8, p<0.05), both which were prevented by addition of Ned-19 at the time of reperfusion (panel D; n=4, p<0.01).

Conclusions

Oxidised PKARIα acts as a potent inhibitor of intracellular calcium release in the heart through its redox-dependent interaction with the lysosome. In the setting of I/R, where PKARIα oxidation is induced, this regulatory mechanism is critical for protecting the heart from injury and offers a novel target for the design of cardioprotective therapeutics.

Acknowledgement/Funding

British Heart Foundation CH/12/3/29609, RG/16/12/32451; Garfield-Weston Foundation MPS/IVIMS-11/12-4032; Wellcome Trust Fellowship 0998981Z/12/Z

A robust route to enzymatically functional, hierarchically self-assembled peptide frameworks

The addition of enzyme biofunctionality to self-assembling peptide nanofibers is challenging since such additions can inhibit functionality or self-assembly. We introduce a method for peptide nanofiber enzyme functionalization, demonstrated by the attachment of a polymerization synthase to peptide nanofibers. The enzyme generates a biocompatible, biodegradable biopolyester coat on the fibers with applicablity in medical engineering. This approach provides a template for generation of functional bionanomaterials.

Fabrication of gold tips by chemical etching in aqua regia

We present a method to produce sharp gold tips for applications in apertureless near-field optical microscopy and spectroscopy. Thin gold wires are tapered by chemical etching in aqua regia, covered by an isooctane protective layer. Tips with apical radii of curvature of <50 nm are obtained with a 40% yield. The tip performances have been checked by shear-force imaging of amyloid fibrils samples and compared to optical fiber probes. The analysis of the tip morphology, carried out by scanning electron microscopy, shows the existence of two different etching processes occurring in bulk and at the liquid-liquid interface. A simple analytical model is presented to describe the dynamics of the tip formation at the liquid-liquid meniscus interface that fits remarkably well the experimental results in terms of tip shape and length.

Total arterial revascularisation as a primary strategy for coronary artery bypass grafting

BACKGROUND

Bilateral internal thoracic arteries confer improved survival benefit after coronary artery bypass grafting (CABG). Despite increasing evidence, the use of arterial conduits has not been accepted as a primary practice in most of the centres in the UK for various reasons. A series of patients has been analysed to assess the feasibility of total arterial revascularisation as a primary strategy in patients requiring first time CABG.

METHODS

Altogether 245 patients undergoing first time CABG by one surgeon, from June 1999 to October 2000, were studied. Group 1 consisted of 165 patients undergoing total arterial revascularisation (using bilateral internal thoracic and radial arteries) and group 2 consisted of 80 patients undergoing conventional CABG (using one internal thoracic artery and supplemental veins). Thirty day mortality and early morbidity with particular reference to resternotomy for bleeding, cerebrovascular accidents, renal failure, and sternal dehiscence were the main outcome measures.

RESULTS

Patients in group 1 were younger (mean (SD) 60 (10) v 65 (9) years; p<0.001), had lower Parsonnet scores (mean (SD) 5 (5) v 11 (7); p<0.001), and better left ventricular function. Both groups received a similar number of grafts. The percentage of patients undergoing total arterial revascularisation rose from 44% in the first three months to over 75% in the three latter three month periods. Overall 30 day mortality was 1.3%, one patient (0.6%) in group 1 and two patients (2.5%) in group 2. There was a similar incidence of postoperative complications and length of median postoperative stay in both groups.

CONCLUSION

Total arterial revascularisation can be adopted as a primary strategy in most patients undergoing CABG with no increase in mortality or morbidity.

Improved Adenoviral Vector for Vascular Gene Therapy

Abstract —First-generation, E1-deleted adenoviral vectors (ΔE1-AV) can transduce the vascular endothelium with high efficiency, but their use is limited by the resulting acute endothelial injury and the long-term development of intimal hyperplasia. To reduce the impact of viral proteins on the gene-modified cells, a second-generation adenoviral vector with an additional pair of deletions in the E4 region was developed. To determine whether this ΔE1/ΔE4-AV vector would be useful for vascular gene transfer, we directly compared the efficiency of gene transfer to uninjured rabbit carotid arteries using either an ΔE1/ΔE4-AV or an ΔE1-AV vector encoding β-galactosidase. Both vectors efficiently transduced vascular endothelium; however, the ΔE1/ΔE4-AV vector gene–modified vessels showed higher β-galactosidase expression 10 days after gene transfer. Importantly, the ΔE1/ΔE4-AV vector produced substantially less endothelial cell activation, less inflammation, and reduced neointimal hyperplasia compared with the ΔE1-AV vector–treated vessels. The ΔE1-AV vector–transduced vessels also demonstrated significantly impaired endothelium-dependent relaxation whereas the ΔE1/ΔE4-AV vector did not impact vasomotor function, even at doses of virus in 5-fold excess of the amount required for >90% transduction of the endothelium. We conclude that the ΔE1/ΔE4-AV vector is superior to the ΔE1-AV vector for vascular gene therapy because of the prolonged transgene expression, reduced vascular inflammation, reduced intimal hyperplasia, and maintenance of normal vasomotor function.

Enhanced superoxide production in experimental venous bypass graft intimal hyperplasia: role of NAD(P)H oxidase

-Vein graft intimal hyperplasia, due to smooth muscle cell (SMC) proliferation, remains a limiting factor in long-term vein graft patency. Increased superoxide production regulates SMC mitogenesis and contributes to reduced NO bioactivity in systemic models of vascular disease. We compared superoxide production in experimental venous bypass grafts with ungrafted veins and determined its enzymatic sources and cellular localization. Vascular superoxide production was measured in vein grafts and control jugular veins obtained from normocholesterolemic rabbits undergoing jugular vein-carotid artery interposition bypass grafting. Surgical isolation of the contralateral jugular vein, without bypass grafting, provided an additional control for the effects of surgical manipulation. Superoxide production was increased 3-fold in vein grafts compared with control veins. Systematic stimulation and inhibition of specific oxidases revealed that the major source of increased vein graft superoxide production was a membrane-associated NAD(P)H-dependent oxidase. Western blotting of vascular homogenates demonstrated corresponding increases in NAD(P)H oxidase p22phox (membrane-associated) and p67phox (cytosolic) subunits in vein grafts compared with jugular veins. There was marked intimal hyperplasia in vein grafts, and immunohistochemical staining of vessel cryosections revealed increased p22phox-expressing cells in vein grafts that were predominantly intimal SMCs. Superoxide generation is increased in experimental vein grafts compared with ungrafted veins. The principal source of increased superoxide generation in vein grafts is an NAD(P)H oxidase, expressed by intimal SMCs. These findings suggest a role for NAD(P)H oxidase-mediated superoxide production in the proliferative response to vascular injury in vein grafts.

Mechanism of pacemaker induced cough

Single chamber ventricular pacing (VVI) may be associated with a group of adverse symptoms known as the pacemaker syndrome. Cough is an unusual but recognised feature of the pacemaker syndrome. A patient with a VVI permanent pacemaker experienced a disturbing cough during VVI pacing. There were no other symptoms associated with the pacemaker syndrome. The effects of short-term ventricular pacing on the cough were examined while the subject was standing and lying. After control recordings, the pulse generator was programmed to either VVI 50 beats/min or 90 beats/min and recordings made over 60 seconds. There was an interval of 60s between recordings. Overall, five recording periods at VVI of 50 beats/min and VVI of 90 beats/min were made in random order. The patient was blinded to the order of programming. The recordings were repeated with the subject lying. Cough was not found during normal sinus rhythm. During VVI pacing the patient experienced a tickling sensation in the throat associated with intermittent coughing. The number of coughs decreased during each successive recording period. The pacing cough reflex was enhanced when the patient was lying down. The mechanism of cough during VVI pacing is uncertain. The findings suggest a possible role for afferent vagal receptors from the airways.