Ravi De Silva

What is the optimal timing for surgery in infective endocarditis with cerebrovascular complications

Neurologic dysfunction complicates the course of 10-40% of left-side infective endocarditis (IE). In right-sided IE, instead, when systemic emboli occur, paradoxical embolism should be considered. The spectrum of neurologic events includes embolic cerebrovascular complication (CVC), intracranial haemorrhage, ruptured mycotic aneurysm, transient ischaemic attack (TIA), meningitis, encephalopathy and brain abscess. Cardiopulmonary bypass might exacerbate neurological deficits due to: heparinization and secondary cerebral haemorrhage; hypotension and cerebral oedema in areas of the disrupted blood brain barrier. A best evidence topic was written according to a structured protocol. The question addressed was, whether there is an optimal timing for surgery in IE with CVCs. One hundred papers were found using the reported search criteria, and out of these 20 papers, provided 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 were tabulated. We found that evidence is conflicting because of lack of controlled studies. The optimal timing for the valve replacement depends on the type of neurological complication and the urgency of the operation. The new 2009 Guidelines on the prevention, diagnosis, and treatment of infective endocarditis (IE) recommend a multidisciplinary approach and to wait for 1-2 weeks of antibiotics treatment before performing cardiac surgery. However, early surgery is indicated in: heart failure (class 1 B), uncontrolled infection (class 1 B) and prevention of embolic events (class 1B/C). After a stroke, surgery should not be delayed as long as coma is absent and cerebral haemorrhage has been excluded by cranial CT (class IIa level B). After a TIA or a silent cerebral embolism, surgery is recommended without delay (class 1 level B). In intracranial haemorrhage (ICH), surgery must be postponed for at least 1 month (class 1 level C). Surgery for prosthetic valve endocarditis (PVE) follows the general principles outlined for native valve IE. Every patient should have a repeated head CT scan immediately before the operation to rule out a preoperative haemorrhagic transformation of a brain infarction. The presence of a haematoma warrants neurosurgical consultation and consideration of cerebral angiography to rule out a mycotic aneurysm.

Myocardial steatosis and left ventricular contractile dysfunction in patients with severe aortic stenosis.

Background— Aortic stenosis (AS) leads to left ventricular (LV) hypertrophy and dysfunction. We hypothesized that cardiac steatosis is involved in the pathophysiology and also assessed whether it is reversible after aortic valve replacement. Methods and Results— Thirty-nine patients with severe AS (symptomatic=25, asymptomatic=14) with normal LV ejection fraction and no significant coronary artery disease and 20 age- and sex-matched healthy controls underwent cardiac 1H-magnetic resonance spectroscopy and imaging for the determination of steatosis (myocardial triglyceride content) and cardiac function, including circumferential strain (measured by magnetic resonance tagging). Strain was lower in both symptomatic and asymptomatic AS (−16.4±2.5% and −18.1±2.9%, respectively, versus controls −20.7±2.0%, both P<0.05). Myocardial steatosis was found in both symptomatic and asymptomatic patients with AS (0.89±0.42% in symptomatic AS; 0.75±0.36% in asymptomatic AS versus controls 0.45±0.17, both P<0.05). Importantly, multivariable analysis indicated that steatosis was an independent correlate of impaired LV strain. Spectroscopic measurements of myocardial triglyceride content correlated significantly with histological analysis of biopsies obtained during aortic valve replacement. At 8.0±2.1 months after aortic valve replacement, steatosis and strain had recovered toward normal. Conclusions— Pronounced myocardial steatosis is present in severe AS, regardless of symptoms, and is independently associated with the degree of LV strain impairment. Myocardial triglyceride content measured by magnetic resonance spectroscopy correlates with histological quantification. Steatosis and strain impairment are reversible after aortic valve replacement. Our findings suggest a novel pathophysiological mechanism in AS, myocardial steatosis, which may be amenable to treatment, thus potentially delaying onset of LV dysfunction.

Myocardial perfusion and oxygenation are impaired during stress in severe aortic stenosis and correlate with impaired energetics and subclinical left ventricular dysfunction.

BackgroundLeft ventricular (LV) hypertrophy in aortic stenosis (AS) is characterized by reduced myocardial perfusion reserve due to coronary microvascular dysfunction. However, whether this hypoperfusion leads to tissue deoxygenation is unknown. We aimed to assess myocardial oxygenation in severe AS without obstructive coronary artery disease, and to investigate its association with myocardial energetics and function.MethodsTwenty-eight patients with isolated severe AS and 15 controls underwent cardiovascular magnetic resonance (CMR) for assessment of perfusion (myocardial perfusion reserve index-MPRI) and oxygenation (blood-oxygen level dependent-BOLD signal intensity-SI change) during adenosine stress. LV circumferential strain and phosphocreatine/adenosine triphosphate (PCr/ATP) ratios were assessed using tagging CMR and 31P MR spectroscopy, respectively.ResultsAS patients had reduced MPRI (1.1 ± 0.3 vs. controls 1.7 ± 0.3, p < 0.001) and BOLD SI change during stress (5.1 ± 8.9% vs. controls 18.2 ± 10.1%, p = 0.001), as well as reduced PCr/ATP (1.45 ± 0.21 vs. 2.00 ± 0.25, p < 0.001) and LV strain (−16.4 ± 2.7% vs. controls −21.3 ± 1.9%, p < 0.001). Both perfusion reserve and oxygenation showed positive correlations with energetics and LV strain. Furthermore, impaired energetics correlated with reduced strain. Eight months post aortic valve replacement (AVR) (n = 14), perfusion (MPRI 1.6 ± 0.5), oxygenation (BOLD SI change 15.6 ± 7.0%), energetics (PCr/ATP 1.86 ± 0.48) and circumferential strain (−19.4 ± 2.5%) improved significantly.ConclusionsSevere AS is characterized by impaired perfusion reserve and oxygenation which are related to the degree of derangement in energetics and associated LV dysfunction. These changes are reversible on relief of pressure overload and hypertrophy regression. Strategies aimed at improving oxygen demand–supply balance to preserve myocardial energetics and LV function are promising future therapies.

Surgeon-specific mortality data disguise wider failings in delivery of safe surgical services.

OBJECTIVES Feedback of clinical outcome data to clinicians can promote and enhance patient safety. Surgeon-specific mortality data (SSMD) have been released to the public for a number of specialties. This implies that one individual is culpable for all deaths. Debate continues about SSMD because of risk-averse behaviour. In the USA, improved outcome measures derived from phase of care mortality analysis (POCMA) and the failure to rescue (FTR) are replacing SSMD, but they have not been tested in Europe. METHODS Using POCMA and FTR analysis, we studied hospital deaths in 1558 cardiac surgical patients between 2009 and 2013. Comorbidity and urgency status were used to calculate modified logistic EuroSCORE (MLE). The circumstances of death were critically reviewed by a panel of four experienced surgeons. Death certificate information and autopsy were taken into account. Deaths were then classified: Class 1 surgeon dependent, Class 2 FTR or Class 3 where multiple factors conspired to cause death. RESULTS There were 51 deaths providing 3.3% mortality, as predicted by MLE. In the 86% who underwent autopsy, no surgical error was identified. Most deaths in each group were related to high-risk status, age, frailty, comorbidity and urgency. FTR was the predominant factor occurring in 45%. Though difficult operations were implicated in 37%, no deaths occurred in the operating theatre. Some FTR deaths occurred in low-risk patients. Scrutiny of FTR deaths provided important information that could be used for quality improvement. CONCLUSIONS The study showed that most deaths cannot be prevented by the operating surgeon. They occurred through issues of patient comorbidity, lack of process or infrastructure. This casts doubt on SSMD publication alone as a tool for quality improvement. In contrast, POCMA and FTR highlight problems of process, and are more likely to promote advances in surgical care.

Recruitment to UK cardiothoracic surgery in the era of public outcome reporting.

OBJECTIVES Since 1999 important widely publicized issues have affected morale in UK cardiothoracic (CT) surgery. Because more surgeons are needed, we sought to investigate whether these events have affected recruitment and demographic change in the specialty between 1999 and 2014. METHODS We collected information on UK consultant CT surgeons using the SCTS public portal, the GMC Specialist Register and the NHS Annual Workforce Census via the Health & Social Care Information Centre. We analysed the demographics of UK CT surgeons with regard to country of primary medical qualification and ethnicity between 1999 and 2014. We compared the changes with other surgical specialties, cardiology and respiratory medicine. RESULTS There has been a worrying decline in UK medical graduates entering the specialty and a 4-fold increase (282%) in consultant appointments from Europe. Whilst consultant numbers expanded by 83% overall, 59% of congenital heart surgeons, 46% of thoracic surgeons and 36% of adult cardiac surgeons are overseas graduates. It is found that 5% are female. Currently, only 32% of trainee surgeons are UK graduates. Of those receiving UK Certificate of Completion of Training in 2013, only 18% were UK graduates compared with 68% in 2000. Comparison with other specialties shows fewer UK graduates in CT surgery with the exception of Obstetrics and Gynaecology (52%). In cardiology, 77% are UK graduates with only 8% from Europe. CONCLUSIONS Repeated negative messages have had a detrimental influence on recruitment. Because 55% of UK medical graduates, but less than 5% of CT surgeons are female, recruitment problems may worsen. Action is needed to restore interest in the specialty.

Extra Corporeal Membrane Oxygenation as Right Heart Support Following Left Ventricular Assist Device Placement: A New Cannulation Technique

Extracorporeal membrane oxygenation is an established treatment for acute respiratory failure, or low cardiac output syndrome. This can be veno-venous, in which de-oxygenated blood is drained from the venous system and oxygenated before being returned to the venous system, and veno-arterial where the re-oxygenated venous blood is returned to the arterial system. Haemorrhage, sepsis and thrombo-embolism are common and potentially lethal complications. Left ventricular assist devices are a continually evolving technology, that may be used as a bridge to transplantation or destination therapy in end-stage cardiac failure. The VentrAssist™ left ventricular assist device is a small implantable, continuous flow centrifugal pump, that is controlled and powered by a percutaneous lead. However, in these patients, right heart failure may present as an acute event following weaning from cardiopulmonary bypass (CPB), or post-operatively in the intensive care unit. Patients who do not respond to inotropes and pulmonary vasodilators may need a right ventricular assist device (RVAD). We report a successful case of right heart assist extra corporeal membrane oxygenation used as temporary right heart support in combination with a VentrAssist™ left ventricular assist device. The use of right heart assist extra corporeal membrane oxygenation to help a failing right heart during left ventricular assist device placement is not new, however, our technique describes a novel method of cannulation of the femoral vein and pulmonary trunk via a tunnelled vascular tube graft, which allows the chest to be closed whilst on right heart support, and decannulation to proceed without resternotomy. This technique has also been used successfully subsequent to this.

A lipopolysaccharide adsorber in adult cardiopulmonary bypass: a single centre randomised controlled pilot trial

OBJECTIVES The aim of this study was to describe the biochemical effects and safety of selective removal of endotoxin from whole blood using a lipopolysaccharide adsorber during complex cardiac surgery. METHODS We carried out a single centre prospective randomised controlled pilot trial in patients undergoing elective cardiac surgery using cardiopulmonary bypass (CPB) at a large UK cardiothoracic institution. Seventeen patients were randomly allocated to one of two groups: with or without an adsorber included in the CPB circuit. Fourteen patients were included in a complete case analysis. Blood samples were taken at the time of consent, immediately following anaesthesia, at 60, 180 and 360 min after the institution of CPB, and the morning following surgery. Primary outcomes were plasma levels of endotoxin, IL-6, IL-8 and TNF-alpha. Secondary outcomes were measures of patient safety including blood chemistry and coagulation parameters, length of stay, and adverse events. RESULTS No differences were seen in endotoxin or cytokine levels between adsorber and control groups at any of the measured time-points. No difference between groups was detected in measures of patient safety following the intervention. Haemoglobin and haematocrit were significantly lower in the intervention group pre-bypass, P=0.02 in both instances. CONCLUSION There was no effect of the adsorber on endotoxin levels or inflammatory response in this study, we have demonstrated the device to be safe in a complex cardiac surgery setting.

Right pulmonary artery occlusion by an acute dissecting aneurysm of the ascending aorta.

We describe the case of a 76-year old female who presented with a Type A aortic dissection requiring repair with an interposition graft and aortic valve replacement. Post-operatively she had clinical features and computerised tomographic images suggestive of a pulmonary embolus and died 24 hours later. The extremely rare finding of intramural thrombus occluding the right pulmonary artery was seen at post mortem.

Cannulation techniques for temporary right and left ventricular support: simple solutions for a difficult problem.

End-stage cardiac failure where appropriate is best treated with cardiac transplantation. With improvements in medical therapy, the emergence of primary percutaneous coronary intervention, and an increasingly ageing population, patients with right, left or biventricular failure, who are not suitable for cardiac transplantation or long-term ventricular assist device therapy, present for cardiac surgery. The modern cardiac surgeon needs to have a safe strategy for dealing with these complex cases. We report two cases that illustrate simple and safe cannulation techniques for temporary left and right ventricular failure.

Molecular mechanisms of myocardial nitroso-redox imbalance during on-pump cardiac surgery

BACKGROUND The mechanism responsible for left ventricular dysfunction after cardiac surgery is only partly understood. In isolated rat hearts subjected to an ischaemia-reperfusion protocol, left ventricular dysfunction was associated with uncoupling of endothelial nitric oxide synthase (NOS) activity secondary to oxidation of the NOS cofactor, tetrahydrobiopterin (BH4). Here we investigated the effect of cardiopulmonary bypass and reperfusion on myocardial nitroso-redox balance in patients undergoing cardiac surgery. METHODS From 116 patients who underwent elective cardiac surgery on cardiopulmonary bypass, paired samples of the right atrial appendages were obtained before venous cannulation of the right atrium and after myocardial reperfusion. Superoxide production from atrial samples was measured by lucigenin (5 μmol/L) enhanced chemiluminescence and 2-hydroxyethidium (2-OHE) detection by high-performance liquid chromatography (HPLC). BH4, oxidised biopterins, GTP-cyclohydrolase 1 (GTPCH-1, the rate-limiting enzyme in BH4 synthesis), and NOS activity ((14)C L-arginine to L-citrulline conversion) were measured by HPLC. FINDINGS Atrial superoxide production increased significantly after reperfusion (from mean 37·83 relative light units per s per mg [SE 3·71] before cannulation to 65·02 [6·01] after reperfusion, p<0·0001; n=46 samples from 23 patients) due to increased mitochondrial and NOX2 oxidase activity (by 309% and 149%; p=0·002 and p=0·0002, respectively) and uncoupling of NOS activity. Atrial content of BH4 after perfusion was reduced (by 32%, p=0·001), as was activity of GTPCH1 (50%, p<0·0001). NOS activity decreased significantly after reperfusion (60%, p=0·0005) and this reduction was not affected by BH4 supplementation (10 μM) or NOX2 inhibition ex vivo. Instead, we identified increased endothelial NOS s-glutathionylation as the main mechanism for NOS uncoupling after reperfusion. Reversing NOS s-glutathionylation with dithiothreitol (100 μmol/L) completely restored NOS activity after reperfusion (p=0·34). INTERPRETATION Our findings suggest that NOS s-glutathionylation, rather than BH4 depletion, accounts for NOS dysfunction in patients after cardiac surgery and cardiopulmonary bypass. FUNDING British Heart Foundation.