Can ChatGPT transform cardiac surgery and heart transplantation?

Artificial intelligence (AI) is a transformative technology with many benefits, but also risks when applied to healthcare and cardiac surgery in particular. Surgeons must be aware of AI and its application through generative pre-trained transformers (GPT/ChatGPT) to fully understand what this offers to clinical care, decision making, training, research and education. Clinicians must appreciate that the advantages and potential for transformative change in practice is balanced by risks typified by validation, ethical challenges and medicolegal concerns. ChatGPT should be seen as a tool to support and enhance the skills of surgeons, rather than a replacement for their experience and judgment. Human oversight and intervention will always be necessary to ensure patient safety and to make complex decisions that may require a refined understanding of individual patient circumstances.

Transventricular Cardioscopic Release of a Trapped Prosthetic Mitral Valve Leaflet

Trapped prosthetic valve leaflets are a rare but challenging complication. A 68-year-old male patient had previously undergone redo aortic valve replacement. Postoperatively, he decompensated with severe mitral regurgitation, requiring extracorporeal membrane oxygenation and a salvage mitral valve replacement via right thoracotomy with very difficult access. This procedure was complicated by a trapped valve leaflet. He recovered well initially but presented 2 years later with worsening heart failure due to mitral stenosis and rising pulmonary artery pressures. Due to the high risk of sternotomy and right thoracotomy, a transventricular cardioscopic release of the trapped mitral valve leaflet was undertaken by left minithoracotomy. The procedure was successful, and the patient was discharged home on day 12. This novel minimally invasive approach, which does not require myocardial preservation, is ideal for high-risk patients with this rare complication and has not previously been described. We hope that by sharing our experience, others will consider this innovative approach.

Do older surgeons have safer hands? A retrospective cohort study

Background

For complex surgical procedures a volume-outcome relationship can often be demonstrated implicating multiple factors at a unit and surgeon specific level. This study aims to investigate this phenomenon in lung transplantation over a 30-year period with particular reference to surgeon age and experience, cumulative unit activity and time/day of transplant.

Methods

Prospective databases identified adult patients undergoing isolated lung transplantation at a single UK centre between June 1987 and October 2017. Mortality data was acquired from NHS Spine. Individual surgeon demographics were obtained from the General Medical Council. Student t-test, Pearson’s Chi-squared, Logistic Regression, and Kaplan–Meier Survival analyses were performed using Analyse-it package for MicrosoftExcel and STATA/IC.

Results

954 transplants (55.9% male, age 44.4 ± 13.8 years, 67.9% bilateral lung) were performed, with a median survival to follow-up of 4.37 years. There was no difference in survival by recipient gender (p = 0.661), between individual surgeons (p = 0.224), or between weekday/weekend procedures (p = 0.327).

Increasing centre experience with lung transplantation (OR1.001, 95%CI: 1.000–1.001, p = 0.03) and successive calendar years (OR1.028, 95%CI: 1.005–1.052, p = 0.017) was associated with improved 5-year survival.

Advancing surgeon age at the time of transplant (mean, 48.8 ± 6.6 years) was associated with improved 30-day survival (OR1.062, 95%CI: 1.019 to1.106, p = 0.003), which persisted 5 years post-transplant (OR1.043, 95%CI: 1.014–1.073, p = 0.003).

Individual surgeon experience, measured by the number of previous lung transplants performed, showed a trend towards improved outcomes at 30 days (p = 0.0413) with no difference in 5-year survival (p = 0.192).

Conclusions

Our study demonstrates a relationship between unit volume, increasing surgeon age and survival after lung transplantation. A transplant volume: outcome relationship was not seen for individual surgeons.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13019-022-01943-2.

A human model of bilateral pulmonary vein sampling to assess the effects of one-lung ventilation on neutrophil function

Background

Neutrophil activation drives lung complications after cardiopulmonary bypass (CPB). Evidence suggests the healthy, ventilated lung may beneficially re-condition pro-inflammatory neutrophils. However, evidence in humans is lacking, due to a paucity of good models. CPB with simultaneous central venous and bilateral pulmonary vein sampling provides an opportunity to model effects of one-lung ventilation. The study’s primary objectives were to establish a model of intra-operative, bilateral pulmonary vein sampling and to determine whether neutrophil function differed after passing through inflated or deflated lungs.

Methods

Seventeen patients having “on pump” coronary artery bypass grafting (CABG) with one-lung ventilation (in two cohorts with tidal volume 2ml kg^-1 and FiO₂ 0.21, or tidal volume 4 ml kg^-1 and FiO₂ 0.5 respectively) were recruited. Cohort 1 consisted of 9 patients (7 male, median age 62.0 years) and Cohort 2 consisted of 8 male patients (median age 65.5 years). Recruitment was via prospective screening of scheduled elective and non-elective CABG procedures with cardiopulmonary bypass. Each patient had five blood samples taken—central venous blood pre-operatively; central venous blood pre-CPB; central venous blood post-CPB; pulmonary venous blood draining the ventilated lung post-CPB; and pulmonary venous blood draining the deflated lung post-CPB. Neutrophil phagocytosis and priming status were quantified. Plasma cytokines were measured.

Results

Phagocytosis and priming were not significantly different in neutrophils returning from the ventilated lung as compared to the non-ventilated lung. Plasma IL-6, IL-8 and IL-10 were significantly elevated by CPB.

Conclusions

The intra-operative, bilateral pulmonary vein sampling model provides unique opportunities to assess biological effects of interventions to one lung, with the other lung acting as an internal control. Single-lung ventilation during CPB had no significant effects on neutrophil function.

Extended trans-septal versus left atrial approach in mitral valve surgery: 1017 patients experience

OBJECTIVE

The mitral valve may be accessed directly through the left atrium but visualisation can sometimes be challenging. A trans-septal interatrial approach provides better exposure and easy access for concomitant tricuspid procedures especially in difficult cases. This retrospective study evaluates the safety and effectiveness of the extended vertical trans-septal approach (EVTSA) for routine mitral valve exposure.

METHOD

1017 consecutive patients undergoing an isolated primary mitral valve procedure (repair/replacement) through a median sternotomy were retrospectively studied between 2000 and 2015. Up to 135 patients were operated by EVTSA (group A) while 882 patients underwent a traditional left atrial (LA, group B) approach.

RESULTS

There were 135 patients (M/F=56/79) in group A and 882 patients (M/F=398/484) in group B. Logistic EuroSCORE was significantly lower in EVTSA group (0.61 vs 0.90, p=0.000001). In the LA group there were more patients with preoperative transient ischaemic attack or stroke (94 vs 6, p=0.005). Cumulative cross-clamp time was 82 (44-212) min (EVTSA group) and 78 (30-360) min (LA group) (p=0.271) while cardiopulmonary bypass time was 107 (58-290) and 114 (43-602) min, respectively (p=0.121).Postoperative blood loss was 415 mL (EVTSA) vs 427 mL (LA) (p=0.273). No significant difference was found in the incidence of postoperative atrial fibrillation (p=0.22) or heart block requiring permanent pacemaker (p=0.14).

CONCLUSION

In our opinion, EVTSA to the mitral valve is safe and reproducible. It gives excellent exposure of the mitral valve under all circumstances without any significant increase in cross-clamp or bypass time, postoperative arrhythmia, heart block/pacemaker rate or bleeding.

Outcomes of lung transplantation in adults with bronchiectasis

Background

Lung transplantation is a well-established treatment for end-stage non-cystic fibrosis bronchiectasis (BR), though information regarding outcomes of transplantation remains limited. Our results of lung transplantation for Br are reported here.

Methods

A retrospective review of case notes and transplantation databases was conducted for patients that had underwent lung transplantation for bronchiectasis at the Freeman Hospital between 1990 and 2013.

Results

Fourty two BR patients underwent lung transplantation, the majority (39) having bilateral sequential lung transplantation. Mean age at transplantation was 47.1 years. Pre-transplantation osteoporosis was a significant non-pulmonary morbidity (48%). Polymicrobial infection was common, with Pseudomonas aeruginosa infection frequently but not universally observed (67%). Forced expiratory volume in 1 second (% predicted) improved from a pre-transplantation mean of 0.71 L (22% predicted) to 2.56 L (79 % predicted) at 1-year post-transplantation. Our survival results were 74% at 1 year, 64% at 3 years, 61% at 5 years and 48% at 10 years. Sepsis was a common cause of early post-transplantation deaths.

Conclusions

Lung transplantation for end-stage BR is a useful therapeutic option, with good survival and lung function outcomes. Survival values were similar to other bilateral lung transplants at our centre. Pre-transplantation Pseudomonas infection is common.

ISHLT Consensus Statement on adult and pediatric airway complications after lung transplantation: Definitions, grading system, and therapeutics

Airway complications remain a major cause of morbidity and mortality after cardiothoracic transplantation. The reported incidence of airway ischemic complications varies widely, contributed to by the lack of a universally accepted grading system and standardized definitions. Furthermore, the majority of the existing classification systems fail to integrate the wide range of possible bronchial complications that may develop after lung transplant. Hence, a Working Group was created by the International Society for Heart and Lung Transplantation with the aim of elaborating a universal definition of adult and pediatric airway complications and grading system. One such area of focus is to understand the problem in the context of a more standardized consensus of classifying airway ischemia. This consensus definition will have major clinical, therapeutics, and research implications.

Profiling inflammation and tissue injury markers in perfusate and bronchoalveolar lavage fluid during human ex vivo lung perfusion

OBJECTIVES: Availability of donor lungs suitable for transplant falls short of current demand and contributes to waiting list mortality. Ex vivo lung perfusion (EVLP) offers the opportunity to objectively assess and recondition organs unsuitable for immediate transplant. Identifying robust biomarkers that can stratify donor lungs during EVLP to use or non-use or for specific interventions could further improve its clinical impact.

METHODS: In this pilot study, 16 consecutive donor lungs unsuitable for immediate transplant were assessed by EVLP. Key inflammatory mediators and tissue injury markers were measured in serial perfusate samples collected hourly and in bronchoalveolar lavage fluid (BALF) collected before and after EVLP. Levels were compared between donor lungs that met criteria for transplant and those that did not.

RESULTS: Seven of the 16 donor lungs (44%) improved during EVLP and were transplanted with uniformly good outcomes. Tissue and vascular injury markers lactate dehydrogenase, HMGB-1 and Syndecan-1 were significantly lower in perfusate from transplanted lungs. A model combining IL-1β and IL-8 concentrations in perfusate could predict final EVLP outcome after 2 h assessment. In addition, perfusate IL-1β concentrations showed an inverse correlation to recipient oxygenation 24 h post-transplant.

CONCLUSIONS: This study confirms the feasibility of using inflammation and tissue injury markers in perfusate and BALF to identify donor lungs most likely to improve for successful transplant during clinical EVLP. These results support examining this issue in a larger study.

Lung Injury after Cardiopulmonary Bypass

Pulmonary injury during cardiopulmonary bypass is common as patient factors (smoking, pain, pneumonia) and the effects of cardiopulmonary bypass combine to compromise lung function after cardiac surgery. Lung injury follows the propagation of an inflammatory response involving cytokines, complement, neutrophils, monocytes, activated endothelial cells and platelets. Neutrophils sequester in the lung in response to chemo-tactic agents and release injurious oxygen free radicals and specific enzymes resulting in widespread pulmonary injury.

To alleviate this lung injury a number of possible interventions exist. Off pump surgery may reduce the degree of systemic inflammation but respiratory impairment still occurs and the clinical advantage is uncertain. The use of leukocyte filtration can attenuate the acute inflammatory response with encouraging though variable results. Aprotinin, Pentoxyfilline, Nitric oxide, Aspirin and other agents have shown benefits in lung function after cardiopulmonary bypass induced lung injury.

Given the magnitude and diversity of the inflammatory response to cardiopulmonary bypass many possible interventions exist to attenuate lung injury resulting from extracorporeal circulation. Immediate clinical benefits are likely to result from successful amelioration of the processes involved.

Unusual cause of hypoxemia after automatic implantable cardioverter-defibrillatorleads extraction

The indication of pacemaker/AICD removal are numerous. Serious complication can occur during their removal, severe tricuspid regurgitation is one of the complication. The occurrence of PFO is not uncommon among adult population. Shunting across PFO in most circumstance is negligible, but in some necessitates closure due to hypoxemia. We report a case of 62 year old man, while undergoing AICD removal, had an emergency sternotomy for cardiac tamponade. Postoperatively, he experienced profound hypoxemia refractory to oxygen therapy. Transthoracic Echocardiogram was performed to rule out intracardiac shunts at an early stage, but it was difficult to obtain an good imaging windows poststernotomy. A small pulmonary emboli was noted on CTPA, but was not sufficient to account for the level of hypoxemia and did not resolve with anticoagulation. Transesophageal echocardiogram showed flail septal tricuspid valve with severe TR and bidirectional shunt through large PFO. Patient was posted for surgery, tricuspid valve was replaced and PFO surgically closed. Subsequently, patient recovered well ad was discharged to home. Cause of hypoxemia might be due to respiratory or cardiac dysfunction. But for hypoxemia refractory to oxygen therapy, transoesophageal echocardiogram should be always considered and performed early as an diagnostic tool in post cardiac surgical patients.

National Healthcare Delivery Systems Influence Lung Transplant Outcomes for Cystic Fibrosis

Successful lung transplantation (LTx) depends on multiple components of healthcare delivery and performance. Therefore, we conducted an international registry analysis to compare post-LTx outcomes for cystic fibrosis (CF) patients using the UNOS registry in the United States and the National Health Service (NHS) Transplant Registry in the United Kingdom. Patients with CF who underwent lung or heart-lung transplantation in the United States or United Kingdom between January 1, 2000 and December 31, 2011 were included. The primary outcome was all-cause mortality. Kaplan-Meier analysis and Cox proportional hazards regression evaluated the effect of healthcare system and insurance on mortality after LTx. 2,307 US LTx recipients and 451 individuals in the United Kingdom were included. 894 (38.8%) US LTx recipients had publically funded Medicare/Medicaid insurance. US private insurance and UK patients had improved median predicted survival compared with US Medicare/Medicaid recipients (p < 0.001). In multivariable Cox regression, US Medicare/Medicaid insurance was associated with worse survival after LTx (US private: HR0.78,0.68-0.90,p = 0.001 and UK: HR0.63,0.41-0.97, p = 0.03). This study in CF patients is the largest comparison of LTx in two unique health systems. Both the United States and United Kingdom have similar early survival outcomes, suggesting important dissemination of best practices internationally. However, the performance of US public insurance is significantly worse and may put patients at risk.

Vascular anastomotic complications in lung transplantation: a single institution's experience

OBJECTIVES

Lung transplant recipients were reviewed to compare our early and current experience of vascular complications. Since 1995, we have had a policy of early identification and intervention.

METHODS

We undertook a retrospective review of all adult lung transplants performed at our centre. Patients with pulmonary vascular complications before and after 1995 were identified and reviewed to determine changes in management and outcome.

RESULTS

We identified a total of 13 patients with either pulmonary artery or venous obstruction out of a total of 720 adult lung transplants (1.8%). There were 9 females and 4 males with an age range of 25-64 years. Complications were more common in patients with fibrotic lung disease and involved 15 vascular anastomoses, most commonly the pulmonary arterial anastomosis. Prior to 1995, 5 cases were identified, all postoperatively. In this group, the mean time for identification of the complication was 9.4 (range 4-14) days. Only 1 patient survived to discharge. After 1995, vascular complications were identified intraoperatively in 4 cases and corrected immediately. Four cases were identified postoperatively (at <1-17 days) by a computed tomography pulmonary angiogram. Three were treated surgically within 24 h of diagnosis (using cardiopulmonary bypass with cold preservation). One patient was managed conservatively. Among patients identified after 1995, 5 survived to discharge.

CONCLUSIONS

Though rare, pulmonary vascular complications after lung transplantation carry high mortality. In our opinion, early identification and intervention improves outcome. Intraoperative assessment by pressure gradient measurement and transoesophageal echocardiography is recommended. Despite this, mortality remains high and prevention is better than cure.

Comparison of single lung transplant with and without the use of cardiopulmonary bypass

OBJECTIVES

Many centres avoid using cardiopulmonary bypass (CPB) for lung transplant due to concerns over aggravated lung reperfusion injury and excessive blood loss. We reviewed our 23-years' experience of single lung transplantation.

METHODS

A retrospective review of single lung transplants at our institution (1987-2010), examining differences in allograft function and postoperative complications between CPB and non-bypass (non-CPB) cases.

RESULTS

Two hundred and fifty-nine single lung transplants were undertaken. Fifty-three (20.5%) with CPB. There was no difference demographically between the two groups. No difference existed in preoperative PO(2)/FiO(2). At 1 and 24 h, the postoperative PO(2)/FiO(2) ratio was no different (mean 2.95 and 3.24 in non-CPB cases; 3.53 and 3.75 in CPB patients, P = 0.18 and P = 0.34, respectively). Extubation time was not influenced by the use of CPB. Postoperative blood loss was greater in the CPB group. The usage of fresh frozen plasma and platelets was similar (P = 0.64 and 0.41, respectively). More blood was transfused during postoperative care of CPB patients (P = 0.02).

CONCLUSIONS

Fears of poor postoperative lung function after CPB appear unfounded. We could detect no difference in function or extubation time. Although the use of CPB increases postoperative bleeding and the need for transfusion, it may be used safely to facilitate lung transplantation.

Single lung transplantation with cardiopulmonary bypass

Single lung transplantation can rarely become complicated by hypoxia, hypercarbia and haemodynamic instability which requires extracorporeal support in order to conduct the transplant safely. The decision to use cardiopulmonary bypass must be taken by the surgeon and anaesthetist together after assessing the circumstances but should then be executed without delay. The need for bypass can sometimes be predicted before surgery or becomes obvious most often after induction of anaesthesia or at the time of clamping the pulmonary artery. The use of cardiopulmonary bypass for single lung transplantation is becoming less frequent as its use becomes increasingly confined to patients who have deteriorated significantly on the waiting list or those who are older. Peripheral cannulation of the femoral artery and vein with transoesophageal echocardiographic guidance of venous cannula position and the use of venous assisted drainage allows for rapid institution of cardiopulmonary bypass and an unobstructed operative field in the thorax. Alternatively, cannulation of the main pulmonary artery can be used to effect venous drainage or direct cannulation of the right atrium can be used if the transplant is to be undertaken on that side. Left thoracotomy permits cannulation of the aortic arch or descending aorta for arterial return. Under conditions of cardiopulmonary bypass with modest hypothermia single lung transplantation can proceed in safety. Although many have suggested adverse outcomes when lung transplantation is undertaken with bypass, several series have not indicated high incidences of significant complications. The likelihood of needing bypass may be suggested preoperatively by low right ventricular ejection fraction and poor 6-min walk test results in patients with restrictive lung pathology. This allows the surgeon and anaesthetist to predict problems and be more prepared to intervene with extracorporeal circulation.

Measurement of human interleukin 11

This unit describes an ELISA and a cell proliferation assay that can be used, respectively, to measure the protein level or biologic activity of human and murine interleukin 11 (IL-11). The bioassay is based on the ability of IL-11 to support growth of the B9-11 cell line, a subline of B9 that has traditionally been used to measure levels of IL-6. B9-11 is substantially more responsive to IL-11 than the T10 line used in older protocols. This new bioassay therefore provides improved sensitivity, with a detection limit of 20 pg/ml. An alternate procedure is provided that employs neutralizing antibodies in the cell proliferation bioassay to use to ensure that the activity of the desired molecule (IL-11) is being measured in samples containing multiple cytokines. A describes maintenance of B9-11 cells.

Infective endocarditis during pregnancy: case report

A 29-year-old woman was transferred at 31 weeks gestation for management of infective endocarditis (IE). Echocardiography demonstrated vegetations on aortic valve and severe mitral regurgitation. Blood cultures were positive for Streptococcus sanguis. Due to impending hemodynamic collapse, a cesarean section was performed followed by aortic valve replacement and mitral valve repair with a patch of bovine pericardium. At 10-month review, both mother and baby are doing well.

First report of no-react bovine internal mammary artery performance and patency

BACKGROUND

No-React treatment is known to render tissues resistant to calcific degeneration and to reduce early inflammatory response. No-React bovine internal mammary artery (NR-IMA) is available for restricted use in Europe. In this first study, our aim was to use magnetic resonance imaging (MRI) to investigate the clinical performance and patency rates of this conduit.

METHODS

Seven patients received 8 grafts with NR-IMA. Approval from the Medical Devices Agency of the United Kingdom was obtained for use of this material. One patient needed salvage coronary artery bypass grafting (CABG). Graft patency was investigated with cardiac MRI. One patient was excluded from the MRI study because of the presence of intracerebral metal clips. The mean follow-up period was 2.5 years with a range of 1 to 4.5 years.

RESULTS

There was no mortality in this group. After treatment 6 patients were asymptomatic, and 1 patient had class II anginal symptoms. Four (57%) of the 7 NR-IMA grafts remained patent. The longest patency was 4.5 years in a patient who underwent salvage CABG. Other associated grafts in this cohort of patients were 5 left internal mammary arteries (all patent), 1 radial artery graft (patent), and 7 saphenous vein grafts (4 [57%] of 7 patent). There were no occluded NR-IMA grafts in a patient with patent vein grafts.

CONCLUSION

We concluded that at 2.5 year follow-up, NR-IMA had a patency rate of 57% (4 of 7 cases). This rate matched the vein graft patency rate in this cohort of patients. With the longest patency of 4.5 years, use of NR-IMA seems to hold promise for the future.

A Fatal Fungus

We report the case of a 66-year-old man who presented with a prodromal type illness and pre-sternal swelling after having coronary artery bypass grafts 4 years earlier. Computed tomography showed that the mass had a retrosternal extension, to join a collection anterior to the right ventricle. Candida famata was isolated from operative specimens and he was treated with aggressive antifungal therapy. We believe that this is the first reported case of mediastinal Candida famata.

Pentoxifylline is as effective as leukocyte depletion for modulating pulmonary reperfusion injury

OBJECTIVE

Previous studies have suggested the amelioration of lung reperfusion injury when initial reperfusion is undertaken with leukocyte-depleted blood. Pharmacologic agents, such as pentoxifylline, are also effective, but no previous studies have demonstrated which is superior. We investigated these agents in a porcine model of left single-lung transplantation.

METHODS

Donor lungs were preserved with modified Euro-Collins solution for a mean ischemic time of 18.6 hours. Gas exchange, pulmonary vascular resistance, neutrophil elastase level, and free radical release (measured on the basis of malonaldehyde levels) were assessed over a 12-hour period. Group A (n = 5) was a control group with no interventions added. Group B was reperfused through an extracorporeal circuit incorporating a leukocyte-depleting filter for 30 minutes before conventional blood flow was restored. Group C was reperfused with the addition of intravenous pentoxifylline (2 mg x kg(-1) x h(-1)).

RESULTS

Groups B and C were similar in terms of oxygenation, pulmonary vascular resistance, and free radical release. Group B displayed increased levels of neutrophil elastase. Both groups were superior with regard to these outcome measures compared with control group A.

CONCLUSIONS

Pentoxifylline, when administered to recipient animals, attenuates reperfusion injury to a degree similar to that seen with leukocyte-depleted reperfusion. This technique is simple, safe, and as effective as using a more complex extracorporeal circuit incorporating a leukocyte-depleting filter to ameliorate acute lung injury.

Improvements in lung compliance after pulmonary transplantation: correlation with interleukin 8 expression

OBJECTIVE

Previous studies have suggested reductions in lung reperfusion injury when initial reperfusion is undertaken with the addition of pharmacological modulators. We investigated three pharmacological agents in a porcine model of left single lung transplantation to determine the effect on lung compliance and its relationship with the expression of the cytokine, interleukin-8 (IL-8).

METHODS

Donor lungs were preserved with modified Euro-Collins for a mean ischaemic time of 18.6 h. Pulmonary venous oxygenation, lung compliance and IL-8 expression were assessed over a 12-h period. Group A (n=5) was a control group with no interventions added, Group B was reperfused with the addition of intravenous inositol hexakisphosphate (InSP6) (0.02 mg/kg per min), Group C received the nitric oxide donor, 3-morpholinosydnonimine (SIN-1) (0.02 mg/kg per min) and Group D received intravenous Pentoxifylline (2 mg/kg per h). All interventions were administered at a pulmonary artery pressure of 20 mmHg.

RESULTS

Group D yielded the best oxygenation (P=0.0041) while Groups B and C were similar. All were superior to Group A (P<0.001). Lung compliance was significantly improved in Groups B, C and D compared to group A. In Group D, the greatest improvements in lung compliance were observed (P<0.0001). Similar observations were seen with regard to pulmonary vascular resistance. IL-8 expression was delayed until after 30 min of reperfusion in Group D, but was evident after 10 min in all the other groups. This correlates with the compliance and oxygenation data.

CONCLUSIONS

The addition of InSP6 or SIN-1 at reperfusion significantly attenuates reperfusion injury compared with controls and improves lung compliance. The unique comparison with Pentoxifylline afforded by this study indicates that at the doses studied Pentoxifylline appears to be superior, correlating with a greater inhibition of IL-8 expression.

Laser flash photolysis of bismaleimidesThis paper is dedicated to Professor Fred Lewis on the event of his 60th birthday

Bismaleimides containing between 2 and 12 methylene spacer units have been synthesized and characterized using laser flash photolysis spectroscopy. In the case of the monofunctional N-methylmaleimide, the 1,4-biradical was observed only at maleimide concentrations high enough to effectively quench the triplet state, indicating that the 1,4-biradical is Formed from self-quenching of the triplet excited state. The transient spectral features and the transient lifetimes of bismaleimides containing 2 and 9 methylene spacer units closely resemble those of N-methylmaleimide and are attributed to triplet-state transients. N,N'-Alkylenebismaleimides with 3 and 6 methylene spacer groups exhibit a transient with a very short lifetime attributed to a singlet 1,4-biradical species formed from intramolecular interaction. The absence of triplet spectra in these latter bismaleimides indicate that the 1,4-biradical is formed directly from the excited singlet state. The large difference in the lifetime of the 1,4-biradical formed in monofunctional maleimide solutions and bismaleimide solutions is reflective of differences in the biradical spin-state multiplicity. The bismaleimide with a 12 methylene spacer group exhibits transient spectra corresponding to both a triplet state of the maleimide and a 1,4-biradical formed by exo interaction of two maleimide groups. As a demonstration of the ability of acrylate monomers to react with the short-lived singlet biradicals, it is shown that the photopolymerization of a multifunctional acrylate monomer is readily initiated by the 1,4-biradical formed from the bismaleimides with 3 and 6 methylene spacer groups, presumably by direct reaction of the biradical with the acrylate.

Clinical and hemodynamic evaluation of small Perimount aortic valves in patients aged 75 years or older

BACKGROUND

There is the potential for iatrogenic aortic stenosis and poor quality of life when small aortic valve bioprostheses are used in elderly patients. The alternative is enlarging the aortic annulus to accommodate larger size prostheses, increasing operative mortality. It was hoped that bovine pericardial valves would improve hemodynamic performance in the smaller valve sizes.

METHODS

To determine long-term results and in vivo hemodynamic performance of small-size aortic Carpentier-Edwards bovine pericardial valves (Perimount) in elderly patients, we analyzed our follow-up and echocardiographic data from patients 75 years of age or older receiving isolated 19-mm and 21-mm Perimount valves. Ninety-four patients with a mean age of 77 +/- 2.2 years were followed for 12 years. Seventeen patients with 19-mm and 25 patients with 21-mm Perimount valves underwent transthoracic echocardiograms.

RESULTS

Operative mortality was 6.3% (6 of 94). Twelve-year survival was 82.7%. Freedom from thromboembolism was 86.9% at 12 years. Two patients had anticoagulation-related bleeding. Overall New York Heart Association class decreased from 3 +/- 1 to 1.6 +/- 0.7 at the end of follow-up. Hemodynamic performances were satisfactory in both 19-mm and 21-mm Perimount valves, with low peak and mean transvalvular gradients and good effective orifice areas, orifice area indices, and performance indices.

CONCLUSIONS

Perimount aortic valve in the small aortic annulus has yielded excellent long-term results and hemodynamic performances. Perimount is a very satisfactory option in elderly patients. Implantation of a Perimount bioprosthesis avoids enlargement of the small aortic annulus, reducing mortality and morbidity associated with this procedure.

Effect of WBC reduction of transfused RBCs on postoperative infection rates in cardiac surgery

BACKGROUND

WBC-replete blood transfusion has been suggested as an independent cause of increased postoperative infection.

STUDY DESIGN AND METHODS

A total of 597 patients undergoing elective coronary artery or heart valve surgery were randomly assigned to receive plasma-reduced (PR), buffy coat-depleted (BCD), or WBC-filtered (WCF) RBCs in the event of requiring blood transfusion. Details of postoperative course were recorded. Further information was collected from the patient's general practitioner 3 months after discharge.

RESULTS

No significant difference in inpatient infection rates was observed among patients randomly assigned to receive PR, BCD, or WCF RBCs. When only those receiving transfusion were analyzed (n = 509), use of PR RBCs was associated with more events coded as infections (p < or = 0.05) compared with BCD or WCF RBCs. However, when events coded as urinary tract infections were excluded, there was no significant difference among the three groups. Follow-up performed after discharge showed no difference in readmission rates, but a higher reported rate of infection in those randomly assigned to receive WCF RBCs (p < 0.02).

CONCLUSION

No evidence has been found, analyzed by intention to treat, that use of WBC-reduced, BCD, or WCF RBCs reduces postoperative inpatient infection in patients undergoing cardiac bypass surgery.

Effect of low molecular weight heparin (fragmin) on bleeding after cardiac surgery

BACKGROUND

Fragmin (Dalteparin, Pharmacia Ltd, Milton Keynes, UK), a low molecular weight heparin, is now recommended in the treatment of unstable angina. Due to the greater bioavailability and longer half-life of Fragmin compared with conventional heparin we postulated that this may influence postoperative bleeding after cardiac surgery for unstable angina.

METHODS

We investigated the influence of the agent on postoperative bleeding after cardiac surgery. Patients undergoing first-time coronary artery bypass grafting were prospectively studied in four groups: group A (n = 100) were elective patients; group B (n = 60) had unstable angina and received conventional heparin intravenously until operation; group C (n = 115) received Fragmin with the last dose administered more than 12 hours before surgery; and group D (n = 115) received Fragmin within 12 hours of operation.

RESULTS

Patients in group D had significantly greater blood loss (p < 0.001) and increased blood transfusion than groups A, B, and C (p = 0.047). Patients receiving Fragmin more than 12 hours before surgery (group C) had similar rates of blood loss and transfusion to group B (p > 0.05) but greater than in group A (p = 0.021). There were no differences in reopening rate.

CONCLUSIONS

The risks of bleeding and transfusion must be weighed against the risks of acute ischemic events if Fragmin is stopped more than 12 hours before operation.

Brain event-related potentials (ERPs) in schizophrenia during a word recognition memory task

Impairments of recognition memory for words and attenuation of the ERP 'old-new' effect have been found in patients with left medial temporal lobe damage. If left temporal lobe dysfunction in schizophrenia involves medial structures (e.g. hippocampus), then schizophrenic patients might show similar abnormalities of verbal recognition memory. This study recorded ERPs from 30 electrode sites while subjects were engaged in a continuous word recognition memory task. Results are reported for 24 patients having a diagnosis of schizophrenia (n = 16) or schizoaffective disorder (n = 8) and 19 age-matched healthy controls. Both patients and controls showed the expected 'old-new' effect, with greater late positivity to correctly recognized old words at posterior sites, and there was also no significant difference between groups in P3 amplitude. However, accuracy of word recognition memory was poorer in patients than controls, and patients showed markedly smaller N2 amplitude. Reduced amplitudes of N2 and N2-P3 were associated with poorer performance, with highest correlations over the left inferior parietal (N2) and left medial parietal (N2-P3) region. Moreover, patients failed to show significantly greater left than right hemisphere amplitude of N2-P3 at posterior sites, which was seen for healthy controls. These findings suggest that impaired word recognition in schizophrenia may arise from a left lateralized deficit at an early stage of processing, beginning at 200-300 ms after word onset.

APOBEC-2, a cardiac- and skeletal muscle-specific member of the cytidine deaminase supergene family

APOBEC-1, which mediates the editing of apolipoprotein (apo) B mRNA, is the only known member of the C (cytidine)-->U (uridine) editing enzyme subfamily of the cytidine deaminase supergene family. Here we report the cloning of APOBEC-2, another member of the subfamily. Human and mouse APOBEC-2 both contain 224 amino acid residues, and their genes are mapped to syntenic regions of human chromosome 6 (6p21) and mouse chromosome 17. By phylogenetic analysis, APOBEC-2 is shown to be evolutionarily related to APOBEC-1, and analysis of substitution rates indicates that APOBEC-2 is a much better conserved gene than APOBEC-1. APOBEC-2 mRNA and protein are expressed exclusively in heart and skeletal muscle. APOBEC-2 does not display detectable apoB mRNA editing activity. Like other editing enzymes of the cytidine deaminase superfamily, APOBEC-2 has low, but definite, intrinsic cytidine deaminase activity. The identification of APOBEC-2 indicates that APOBEC-1 is not the only member of the C-->U editing enzyme subfamily, which, like the A (adenosine)-->I (inosine) subfamily of editing enzymes, must encompass at least two and possibly more different deaminase enzymes. It suggests that the C-->U editing affecting apoB mRNA and other RNAs is not an isolated event mediated by a single enzyme but involves multiple related proteins that have evolved from a primordial gene closely related to the housekeeping enzyme cytidine deaminase.

A new porcine model of reperfusion injury after lung transplantation

Rodent models have been described to investigate lung preservation and reperfusion injury but have significant disadvantages. In large animals single lung transplant studies are probably optimal but problems remain over the ability to rigorously separate the lungs for assessment while promoting medium to long-term animal survival for meaningful investigation. Our aim was to develop a novel and refined large animal model to assess reperfusion injury in the transplanted lung, overcoming the difficulties associated with existing models. Specifically, small animal models of lung transplantation usually have short perfusion times (often one hour) and include extracorporeal circuits while larger animal models often require the contralateral lung to be excluded after transplantation-an unphysiological situation under which to evaluate the graft. A porcine model of left lung allotransplantation was developed in which native and donor lungs are individually ventilated. Sampling catheters placed within the graft lung allowed specimen withdrawal without mixing of blood from the contralateral lung after reimplantation. The model permits a variety of clinical scenarios to be simulated with the native lung supporting the animal irrespective of function in the graft. This model has been used in over 60 transplant procedures with a postoperative survival time of 12 h being readily achieved. The mean operating time was 2.6 h. The mortality rate is 4% in our series. We have found the model to be reliable, reproducible and flexible. We propose this model as an adaptable investigation for evaluating lung reperfusion injury and preservation.

Modulation of reperfusion injury after single lung transplantation by pentoxifylline, inositol polyanions, and sin-1

OBJECTIVE

Previous studies have suggested reductions in lung reperfusion injury with pentoxifylline, inositol polyanions, and the nitric oxide donor, SIN-1, but these agents have never been directly compared to ascertain which is superior. We investigated these agents in a porcine model of left single lung transplantation.

METHODS

Donor lungs were preserved with modified Euro-Collins solution for a mean ischemic time of 18.4 hours. Neutrophil trapping in the graft, pulmonary vascular resistance, free radical release (measured by malonaldehyde levels) and gas exchange were assessed over a 12-hour period. All groups were reperfused at an initial pulmonary artery pressure of 20 mm Hg. Group A (n = 5) was a control group with no interventions added; group B was reperfused with the addition of intravenous inositol polyanions (0.02 mg/kg/h), and group C was reperfused with intravenous SIN-1 (0.02 mg/kg/h). Group D was reperfused with the addition of intravenous pentoxifylline (2 mg/kg/h).

RESULTS

Neutrophil sequestration was observed within 10 minutes of reperfusion in group A. This was attenuated significantly by interventions in groups B, C, and D. In group D, malonaldehyde levels were significantly lower than in other groups and was associated with superior oxygenation. Pulmonary vascular resistance was reduced in groups B, C, and D compared with group A.

CONCLUSIONS

Pentoxifylline, when administered only to recipient animals was superior to the other interventions studied. Inositol polyanions are promising as a possible therapeutic intervention but were not as effective as the other agents studied.

Controlled reperfusion and pentoxifylline modulate reperfusion injury after single lung transplantation

OBJECTIVE

Rodent models have suggested that initial low-pressure reperfusion of transplanted lungs reduces injury after ischemia. We investigated this phenomenon and the use of pentoxifylline in a porcine model of left single lung transplantation.

METHODS

Donor lungs were preserved with Euro-Collins solution for a mean ischemic time of 18.4 hours. Neutrophil trapping in the graft, pulmonary artery pressure, and gas exchange were assessed over a 12-hour period. Partial occlusion of the contralateral pulmonary artery allowed manipulation of the pulmonary artery pressure in the transplanted lung. Group A (n = 5) was perfused at a mean pulmonary artery pressure of 20 mm Hg, group B was reperfused at a mean pulmonary artery pressure of 45 mm Hg for 10 minutes before reducing the pressure to the same as group A, and group C was reperfused at a mean pressure of 20 mm Hg for 10 minutes, then increased to a mean of 45 mm Hg for the remainder of the experiment. Group D was reperfused as in group A with the addition of intravenous pentoxifylline.

RESULTS

Leukocyte sequestration was observed in the first 10 minutes after reperfusion in groups A, B, and C, with maximal sequestration at 2 minutes. Significantly more sequestration was observed in the first 6 minutes in group B than in groups A and C, which were similar. Pentoxifylline significantly reduced leukocyte sequestration. Pulmonary venous oxygen tension in the allograft lung was worst in group B. Groups A and C were similar, but group D was superior to all other groups (p < 0.001).

CONCLUSIONS

Low-pressure reperfusion, even when limited to the first 10 minutes, modulates reperfusion injury possibly through a leukocyte-dependent mechanism. The addition of pentoxifylline in the recipient confers significant additional benefit.

A randomized, double-blind, placebo-controlled study of growth hormone in the treatment of fibromyalgia

PURPOSE

The cause of fibromyalgia (FM) is not known. Low levels of insulin-like growth factor 1 (IGF-1), a surrogate marker for low growth hormone (GH) secretion, occur in about one third of patients who have many clinical features of growth hormone deficiency, such as diminished energy, dysphoria, impaired cognition, poor general health, reduced exercise capacity, muscle weakness, and cold intolerance. To determine whether suboptimal growth hormone production could be relevant to the symptomatology of fibromyalgia, we assessed the clinical effects of treatment with growth hormone.

METHODS

Fifty women with fibromyalgia and low IGF-1 levels were enrolled in a randomized, placebo-controlled, double-blind study of 9 months' duration. They gave themselves daily subcutaneous injections of growth hormone or placebo. Two outcome measures--the Fibromyalgia Impact Questionnaire and the number of fibromyalgia tender points-were evaluated at 3-monthly intervals by a blinded investigator. An unblinded investigator reviewed the IGF-1 results monthly and adjusted the growth hormone dose to achieve an IGF-1 level of about 250 ng/mL.

RESULTS

Daily growth hormone injections resulted in a prompt and sustained increase in IGF-1 levels. The treatment (n=22) group showed a significant improvement over the placebo group (n=23) at 9 months in both the Fibromyalgia Impact Questionnaire score (P <0.04) and the tender point score (P <0.03). Fifteen subjects in the growth hormone group and 6 subjects in the control group experienced a global improvement (P <0.02). There was a delayed response to therapy, with most patients experiencing improvement at the 6-month mark. After discontinuing growth hormone, patients experienced a worsening of symptoms. Carpal tunnel symptoms were more prevalent in the growth hormone group (7 versus 1); no other adverse events were more common in this group.

CONCLUSIONS

Women with fibromyalgia and low IGF-1 levels experienced an improvement in their overall symptomatology and number of tender points after 9 months of daily growth hormone therapy. This suggests that a secondary growth hormone deficiency may be responsible for some of the symptoms of fibromyalgia.

Solitary fibrous tumour of the diaphragm

Solitary fibrous tumours are uncommon neoplasms that have been described as occurring in the pleura, peritoneum, lung, mediastinum, pericardium, nose and paranasal sinuses. This report describes the first known case of a solitary fibrous tumour of the diaphragm, occurring in a 60 year old woman with a two year history of respiratory symptoms. The lesion was initially misdiagnosed as an elevated left hemidiaphragm. The operative findings and histological appearance of the tumour are described. A review of the literature examines the various types and presenting features of solitary fibrous tumours as well as their clinical behaviour and postulated origin.

Crucial role of the residue R280 at the F'-G' loop of the human granulocyte/macrophage colony-stimulating factor receptor alpha chain for ligand recognition

The receptor for granulocyte/macrophage colony-stimulating factor (GM-CSF) is composed of two chains, alpha and betac. Both chains belong to the superfamily of cytokine receptors characterized by a common structural feature, i.e., the presence of at least two fibronectin-like folds in the extracellular domain, which was first identified in the growth hormone receptor. The GM-CSF receptor (GMR)-alpha chain confers low affinity binding only (5-10 nM), whereas the other chain, betac, does not bind GM-CSF by itself but confers high affinity binding when associated with GMR-alpha (25-100 pM). The present study was designed to define the assembly of the GMR complex at the molecular level through site-directed mutagenesis guided by homology modeling with the growth hormone receptor complex. In our three-dimensional model, R280 of GMR-alpha, located in the F'-G' loop and close to the WSSWS motif, is in the vicinity of the ligand Asp112, suggesting the possibility of electrostatic interaction between these two residues. Through site directed mutagenesis, we provide several lines of evidence indicating the importance of electrostatic interaction in ligand-receptor recognition. First, mutagenesis of GMR-alphaR280 strikingly ablated ligand binding in the absence of beta common (betac); ligand binding was restored in the presence of betac with, nonetheless, a significant shift from high (26 pM) toward low affinity (from 2 to 13 nM). The rank order of the dissociation constant for the different GMR-alphaR280 mutations where Lys > Gln > Met > Asp, suggesting the importance of the charge at this position. Second, a mutant GM-CSF with charge reversal mutation at position Asp112 exhibited a 1,000-fold decrease in affinity in receptor binding, whereas charge ablation or conservative mutations were the least affected (10-20-fold). Third, removal of the charge at position R280 of GMR-alpha introduced a 10-fold decrease in the association rate constant and only a 2-fold change in the dissociation rate constant, suggesting that R280 is implicated in ligand recognition, possibly through interaction with Asp112 of GM-CSF. For all R280 mutants, the half-efficient concentrations of GM-CSF required for membrane (receptor binding) to nuclear events (c-fos promoter activation) and cell proliferation (thymidine incorporation) were in the same range, indicating that the threshold for biologic activity is governed mainly by the affinity of ligand-receptor interaction. Furthermore, mutation of other residues in the immediate vicinity of R280 was less drastic. Sequence alignment and modeling of interleukin (IL)-3R and IL-5R identified an arginine residue at the tip of a beta turn in a highly divergent context at the F'-G' loop, close to a conserved structural element, the WSXWS motif, suggesting the possibility of a ligand association mechanism similar to the one described herein for GMR.