Edward Black

Functional Effect of the C242T Polymorphism in the NAD(P)H Oxidase p22phox Gene on Vascular Superoxide Production in Atherosclerosis

BackgroundIncreased superoxide anion production increases oxidative stress and reduces nitric oxide bioactivity in vascular disease states. NAD(P)H oxidase is an important source of superoxide in human blood vessels, and some studies suggest a possible association between polymorphisms in the NAD(P)H oxidase CYBA gene and atherosclerosis; however, no functional data address this hypothesis. We examined the relationships between the CYBA C242T polymorphism and direct measurements of superoxide production in human blood vessels. Methods and ResultsVascular NAD(P)H oxidase activity was determined in human saphenous veins obtained from 110 patients with coronary artery disease and identified risk factors. Immunoblotting, reverse-transcription polymerase chain reaction, and DNA sequencing showed that p22phox protein, mRNA, and 242C/T allelic variants are expressed in human blood vessels. Vascular superoxide production, both basal and NADH-stimulated, was highly variable between patients, but the presence of the CYBA 242T allele was associated with significantly reduced vascular NAD(P)H oxidase activity, independent of other clinical risk factors for atherosclerosis. ConclusionsAssociation of the CYBA 242T allele with reduced NAD(P)H oxidase activity in human blood vessels suggests that genetic variation in NAD(P)H oxidase components may play a significant role in modulating superoxide production in human atherosclerosis.

Enhanced Superoxide Production in Experimental Venous Bypass Graft Intimal Hyperplasia: Role of NAD(P)H Oxidase

Abstract —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 p22 phox (membrane-associated) and p67 phox (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 p22 phox-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.

Comparative efficacies and durations of action of phenoxybenzamine, verapamil/nitroglycerin solution, and papaverine as topical antispasmodics for radial artery coronary bypass grafting.

OBJECTIVE Radial arteries are increasingly used as conduits for coronary artery bypass grafts, but perioperative graft vasospasm continues to be a concern. Phenoxybenzamine, verapamil/nitroglycerin solution, and papaverine have been advocated as topical antispasmodic agents. We compared the relative efficacies and durations of action of these agents. METHODS Isometric tension developed in response to clinically important vasoconstrictors was measured in 100 radial artery rings (from patients undergoing coronary artery bypass grafting, n = 25) after 15 minutes of ex vivo incubation with phenoxybenzamine, verapamil/nitroglycerin solution, papaverine, or vehicle (control). Duration of action was assessed by measuring responses to vasoconstrictors in antispasmodic pretreated and control rings at intervals through 5 hours. RESULTS Verapamil/nitroglycerin solution reduced vasoconstriction in response to epinephrine, angiotensin II, prostaglandin F(2alpha), and phenylephrine but its effect had almost completely waned after 5 hours. Phenoxybenzamine prevented vasoconstriction in response to epinephrine, dopamine, and phenylephrine, with its effect lasting at least 5 hours. Papaverine had limited antispasmodic efficacy and prevented vasoconstriction in response to potassium (60 mmol/L) and phenylephrine for only 1 hour at the longest. CONCLUSIONS Verapamil/nitroglycerin solution has a broad efficacy against a range of vasoconstrictors but a limited duration of action. Papaverine has the shortest duration of action. Phenoxybenzamine is an effective agent with a prolonged duration of action, specifically preventing catecholamine mediated vasospasm of radial artery conduits.

Minimally invasive saphenous vein harvesting: effects on endothelial and smooth muscle function.

BACKGROUND The long saphenous vein remains the commonest conduit used in coronary artery bypass grafting procedures. Surgical trauma during vein harvesting can cause endothelial and smooth muscle injury that has important implications for vein graft longevity. Minimally invasive vein harvesting is advocated to reduce wound morbidity. However, the functional consequences of increased handling and traction, with potentially detrimental effects, remain unknown. METHODS Forty patients were prospectively randomized into either a minimally invasive (minimal) or traditional (open) saphenous vein harvest group. Smooth muscle contractile function was assessed by responses to potassium chloride and phenylephrine. Endothelial cell function was assessed by responses to serial escalations in concentration of acetylcholine, bradykinin, calcium ionophore, sodium nitroprusside, and N-nitro-L-arginine using isometric tension studies. RESULTS Harvest times were similar for both groups. The total incision length in the minimal group was significantly shorter than in the open group. There were no differences in smooth muscle contractions to either receptor-independent or receptor-mediated agonists between the two groups. Similarly, vasorelaxation in response to both endothelium-dependent and endothelium-independent agonists were similar in both groups. CONCLUSIONS Minimally invasive saphenous vein harvesting is associated with similar medial smooth muscle and endothelial function as open harvesting. These findings suggest that minimally invasive harvesting techniques can be used without major detrimental effects on vascular integrity.

Is thymectomy in non-thymomatous myasthenia gravis of any benefit?

A best evidence topic in thoracic surgery was written according to a structured protocol. The question addressed was if thymectomy in non-thymomatous myasthenia gravis was of any benefit? Overall, 137 papers were found using the reported search, of which 16 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. The outcome variables were similar in all of the papers, including complete stable remission (CSR), pharmacological remission, age at presentation, gender, duration of symptoms, preoperative classification (Oosterhius, Osserman or myasthenia gravis Foundation of America (MGFA)), thymic pathology, preoperative medications (steroids, immunosuppressants), mortality and morbidity. We conclude that evidence-based reviews have shown that relative rates of thymectomy patients compared with non-thymectomy patients attaining outcome indicate that the former group of patients is more likely to achieve medication-free remission, become asymptomatic and clinically improve (54%, P < 0.01), particularly patients with severe and generalized symptoms (P = 0.007). Patients with generalized myasthenia gravis showed 11% stronger association with favourable outcomes after thymectomy. Some studies show early remission rates (RRs), as early as 6 months post-thymectomy, of 44%. Overall, the reported remission rate for non-thymomatous myasthenia gravis is between 38 and 72% up to 10 years of follow-up. Among these patients, those with thymic hyperplasia show the best complete stable remission rates (42%, P < 0.04) in the majority of studies. Age showed variability across the studies and the cut-off was also different among them. Overall age < 45 years showed a higher probability of achieving complete stable remission during follow-up (81% benefit rate (BR), P < 0.02). Pharmacological improvement is reported between 6 and 42%. However, the certainty of these benefits has not been established due to factors such as the confounding differences between myasthenia gravis patients receiving and not receiving thymectomy, the non-randomized nature of class II studies and the lack of Class I evidence to support its use. There is currently a randomized trial ongoing looking at thymectomy by sternotomy vs controls and the results are eagerly awaited.

UltraRapid communications : vascular superoxide production by NAD(P)H OxidaseAssociation with endothelial dysfunction and clinical risk factors

Superoxide anion plays important roles in vascular disease states. Increased superoxide production contributes to reduced nitric oxide (NO) bioactivity and endothelial dysfunction in experimental models of vascular disease. We measured superoxide production by NAD(P)H oxidase in human blood vessels and examined the relationships between NAD(P)H oxidase activity, NO-mediated endothelial function, and clinical risk factors for atherosclerosis. Endothelium-dependent vasorelaxations and direct measurements of vascular superoxide production were determined in human saphenous veins obtained from 133 patients with coronary artery disease and identified risk factors. The predominant source of vascular superoxide production was an NAD(P)H-dependent oxidase. Increased vascular NAD(P)H oxidase activity was associated with reduced NO-mediated vasorelaxation. Furthermore, reduced endothelial vasorelaxations and increased vascular NAD(P)H oxidase activity were both associated with increased clinical risk factors for atherosclerosis. Diabetes and hypercholesterolemia were independently associated with increased NADH-dependent superoxide production. The association of increased vascular NAD(P)H oxidase activity with endothelial dysfunction and with clinical risk factors suggests an important role for NAD(P)H oxidase-mediated superoxide production in human atherosclerosis. The full text of this article is available at http://www.circresaha.org. Key Words:atherosclerosis endothelium superoxide nitric oxide diabetes Two Distinct Congenital Arrhythmias Evoked by a Multidysfunctional Na(+) Channel Marieke W. Veldkamp, Prakash C. Viswanathan, Connie Bezzina, Antonius Baartscheer, Arthur A.M. Wilde, Jeffrey R. Balser Abstract-The congenital long-QT syndrome (LQT3) and the Brugada syndrome are distinct, life-threatening rhythm disorders linked to autosomal dominant mutations in SCN5A, the gene encoding the human cardiac Na(+) channel. It is believed that these two syndromes result from opposite molecular effects: LQT3 mutations induce a gain of function, whereas Brugada syndrome mutations reduce Na(+) channel function. Paradoxically, an inherited C-terminal SCN5A mutation causes affected individuals to manifest electrocardiographic features of both syndromes: QT-interval prolongation (LQT3) at slow heart rates and distinctive ST-segment elevations (Brugada syndrome) with exercise. In the present study, we show that the insertion of the amino acid 1795insD has opposite effects on two distinct kinetic components of Na(+) channel gating (fast and slow inactivation) that render unique, simultaneous effects on cardiac excitability. The mutation disrupts fast inactivation, causing sustained Na(+) current throughout the action potential plateau and prolonging cardiac repolarization at slow heart rates. At the same time, 1795insD augments slow inactivation, delaying recovery of Na(+) channel availability between stimuli and reducing the Na(+) current at rapid heart rates. Our findings reveal a novel molecular mechanism for the Brugada syndrome and identify a new dual mechanism whereby single SCN5A mutations may evoke multiple cardiac arrhythmia syndromes by influencing diverse components of Na(+) channel gating function. The full text of this article is available at http://www.circresaha.org. Key Words: Na(+) channel inactivation long-QT syndrome Brugada syndrome

Fast-track video-assisted bullectomy and pleurectomy for pneumothorax: initial experience and description of technique

OBJECTIVE Pleurectomy+/-bullectomy by video-assisted thoracoscopic surgery (VATS) is an established surgical procedure for pneumothorax. Early ambulation and discharge should be a reasonable goal. This study explores the feasibility of day-case surgery and identifies the obstacles requiring further work to facilitate day-case pneumothorax surgery. METHODS Between June 2007 and May 2008, 16 consecutive patients underwent video-assisted thoracoscopic surgery bullectomy+/-pleurectomy (under the care of a single surgeon) with immediate connection to an ambulatory drainage system in the theatre following surgery. Analgesia comprised temporary paravertebral with early conversion to oral opiate+/-paracetamol. There were 13 males (81%), average age 23 (range: 17-29) years, and three females (19%), average age 35 (range: 22-46) years. Twelve patients (75%) had left-sided disease, of which nine (56%) underwent elective surgery. All patients had previously suffered at least one primary spontaneous pneumothorax. Patients with probable secondary pneumothorax were excluded from the study. Length of stay (LOS) was compared with a control group of patients conventionally treated prior to the study. RESULTS In 13 patients (81%), early discharge was achieved 1 (range: 1-2 days) day post-op, whilst connected to an ambulatory drainage system. In three patients, early discharge was not achieved. One of these patients had the chest drain removed prematurely and remained an inpatient for 3 days with aspiration and observation for a small pneumothorax. The two remaining patients required extended inpatient admissions due to postoperative non-surgical complications. In the 13 patients discharged immediately, the time to drain removal (in clinic) was electively 7 days (range: 2-11 days). Two patients required re-admission: one for contralateral spontaneous pneumothorax and another for an ipsilateral basal pneumothorax treated with a drain. CONCLUSION We have shown early discharge with ongoing ambulatory drainage following VATS pleurectomy+/-bullectomy in patients with primary pneumothorax to be feasible with paravertebral in the theatre and rapid conversion to oral analgesia. Patients managed intercostal drains at home. Limiting factors such as postoperative nausea and pain control usually can be sufficiently managed in the outpatient. Shorter stays may have a beneficial financial result. Long-term follow-up and a quantification of the patients experience is warranted.

What is the extent of the advantage of video-assisted thoracoscopic surgical resection over thoracotomy in terms of delivery of adjuvant chemotherapy following non-small-cell lung cancer resection?

OBJECTIVES Video-assisted thoracoscopic surgery (VATS) lobectomy for early stage non-small cell lung cancer (NSCLC) is a safe and effective alternative to open lobectomy. Adjuvant chemotherapy is part of the treatment recommended for patients with performance status (PS) 0-1 following resection of NSCLC of stages T1-3 N1-2 M0 and T2-3 N0 M0. If VATS reduces morbidity, does it help delivery of postoperative chemotherapy? We studied our data to compare the delivery and toxicity of chemotherapy in patients following VATS or open lung resections. METHODS We performed a retrospective study of all patients who had resection of primary NSCLC in a single surgical centre between October 2008 and August 2013. Surgical and chemotherapy databases were reviewed to extract data on patient characteristics, operative details, pathological stage, chemotherapy delivery and toxicity. RESULTS Three hundred and twenty-three resections were undertaken for NSCLC; 142 (44%) underwent VATS resection and 181 (56%) open thoracotomy; 16 (11.3%) and 28 (15.5%) of each group received adjuvant chemotherapy, respectively. Patient demographics and tumour stage were as follows: median age (range) was 65.5 (44-77) vs 67.5 (49-76); male: 43.8 vs 50% (P = 1.0); Stage I/II 75 vs 76.9%; Stage III 12.5 vs 30.8%; pre-chemotherapy PS 0 75 vs 78.2% for VATS and thoracotomy groups, respectively. All patients received platinum/vinorelbine therapy. Chemotherapy was initiated significantly earlier in the VATS group (mean 55.7 ± 3.1 vs 68.2 ± 4.3 days, P = 0.046); 68.8% of patients in the VATS group completed four cycles of chemotherapy compared with 60.1% in the open group (P = 0.75). There was a non-significant trend towards reduction in Grade 3/4 haematological toxicity in the VATS group compared with the open group (12.5 vs 39.3%, P = 0.09). CONCLUSIONS Adjuvant chemotherapy was started significantly earlier in patients following VATS lung resections for NSCLC compared with thoracotomy. There was also a trend towards improved tolerance with more complete courses and reduced haematological toxicity.

Tracheo-oesophageal compression due to massive spontaneous retropharyngeal haematoma.

Spontaneous retropharyngeal haematoma and dissecting intramural haematoma of the oesophagus are two distinct, but rare, phenomena. We describe the first case of complete tracheo-oesophageal obstruction due to spontaneous retropharyngeal haematoma presenting with chest pain and dysphagia. Rapid imaging allowed life-saving transfer to the regional specialist centre, with immediate surgical intervention. The importance, aetiology and clinical features of both diagnoses are discussed.

Off-Pump Coronary Artery Bypass Surgery

Off-pump coronary artery bypass surgery has been adopted enthusiastically worldwide. However, despite more than 6 years’ experience and refinement, many surgeons use it only sporadically and some hardly at all. This reluctance persists despite support for the procedure because of the lack of properly designed risk models and/or randomized studies. Although it has not been overwhelmingly shown that off-pump surgery is superior to the conventional on-pump procedure, the technique has its place in our specialty. It has been shown to be better for noncritical end points in selected patients in the hands of selected surgeons. That there are differences in surgical skill among surgeons is something we all know but rarely discuss in public. Until now, disparities in skill have been most salient with uncommon and extraordinarily challenging operations. Perhaps the off-pump procedure should be regarded as the “challenging” aspect of coronary artery bypass surgery, and self-restraint may need to remain in force if we are to continue to achieve the highest level of clinical excellence.