Zinc metalloprotease ProA of Legionella pneumophila increases alveolar septal thickness in human lung tissue explants by collagen IV degradation

ProA is a secreted zinc metalloprotease of Legionella pneumophila causing lung damage in animal models of Legionnaires' disease. Here we demonstrate that ProA promotes infection of human lung tissue explants (HLTEs) and dissect the contribution to cell type specific replication and extracellular virulence mechanisms. For the first time, we reveal that co-incubation of HLTEs with purified ProA causes a significant increase of the alveolar septal thickness. This destruction of connective tissue fibres was further substantiated by collagen IV degradation assays. The moderate attenuation of a proA-negative mutant in A549 epithelial cells and THP-1 macrophages suggests that effects of ProA in tissue mainly result from extracellular activity. Correspondingly, ProA contributes to dissemination and serum resistance of the pathogen, which further expands the versatile substrate spectrum of this thermolysin-like protease. The crystal structure of ProA at 1.48 Å resolution showed high congruence to pseudolysin of Pseudomonas aeruginosa, but revealed deviations in flexible loops, the substrate binding pocket S₁ ' and the repertoire of cofactors, by which ProA can be distinguished from respective homologues. In sum, this work specified virulence features of ProA at different organisational levels by zooming in from histopathological effects in human lung tissue to atomic details of the protease substrate determination.

Conductivity-Based Hematocrit Measurement During Cardiopulmonary Bypass

OBJECTIVE

In a recent clinical study on the reliability of a point-of-care (POC) analyzer, we described a downward bias in hematocrit measurement during cardiopulmonary bypass leading potentially to overtreatment with packed red cells. We hypothesized that the detected deviation is caused by variations in electrolyte concentration rather than by colloids used.

METHODS

Blood was sampled from patients before cardiac surgery to obtain undiluted anticoagulated whole blood samples (n = 53). From each sample, four dilution series covering a hematocrit range of 15-30% were made using NaCl (0.9%), modified gelatine (4%), hydroxyethylstarch (6%), or a potassium-based (16 mEq/l) solution, respectively. In each dilution series, hematocrit was measured by POC and via the "golden standard" microcentrifugal method to determine whether the deviation of the POC-analyzer to the microcentrifuge was dependent on the type and dilution level of the solution used.

RESULTS

In contrast to the colloid-based dilution series, the crystalloids revealed a significant downward bias of the POC-analyzer with respect to the microcentrifuge (p < 0.05). Due to the correction algorithm for sodium in the POC-analyzer, this deviation was nearly constant for NaCl (mean of difference: -1.8 +/- 0.1%), but increased significantly in case of the potassium-based solution (up to -8.2 +/- 0.4% after 1.5-times dilution). The starch- and gelatine-based solutions led to a significant upward bias (p < 0.05) that increased with progressing dilution (up to 1.2 +/- 0.1% for hydroxyethylstarch and up to 1.3 +/- 0.1% for modified gelatine after 1.5-times dilution).

CONCLUSIONS

Conductivity-based POC hematocrit measurement suffers from biases due to changes of the plasma constituents. The downward bias in hematocrit as often seen during cardiopulmonary bypass is driven by changes of different electrolyte concentration rather than by colloids used per se.

The EuroSCORE as predictor for prolonged hospital and intensive care stay after cardiac surgery?

OBJECTIVE

Validation of the EuroSCORE as predictor for a prolonged hospital and intensive care stay after CABG vs. institution-specific scoring systems.

METHODS

For the evaluation of a prolonged hospital stay, 3359 patients were included in the analysis of EuroSCORE vs. the CORRAD morbidity score. For a prolonged intensive care stay, 1638 patients were included in the analysis of the EuroSCORE vs. the PICUS score.

RESULTS

There was no significant difference in hospital stay between the three different EuroSCORE risk groups. The difference in hospital stay between the high-risk and low-risk groups, identified by the CORRAD morbidity score, was significant (6.9 vs.11.2 days). For a prolonged intensive care stay, the patients identified as high risk by the EuroSCORE and by the PICUS score also had a significantly longer intensive care stay; however, the discriminatory power was low.

CONCLUSION

The EuroSCORE is not of value as a predictive system for a prolonged hospital stay. There is a relation between the high-risk patients identified by the EuroSCORE and a prolonged intensive care stay.

Evaluation of long-term quality of life after reoperative coronary artery surgery: preliminary results

OBJECTIVE

The risks of reoperative coronary artery bypass surgery (RECABG) still exceed those of a primary revascularisation and late results are not very favourable either. The subject of the present study is an evaluation of the long-term quality of life after RECABG.

METHODS

We studied the outcome of 541 patients who underwent a RECABG from January 1987 to December 1998. The endpoint of the study was December 2002, or the patient's death. Quality of life, using the EuroQol registration, was evaluated.

RESULTS

Hospital mortality was 6.7%. Follow-up was 95.6% complete, mean 7.7 years. There were 177 late deaths. The cumulative survival rates were 83.8, 76.9, and 60.6%, and cardiac survival rates were 84.8, 78.5, and 66.5%, at the one-year, five-year and ten-year follow-up, respectively. For 255 patients (89%), NYHA and EuroQol information was complete. In total 23% of the patients were in NYHA class I, 51% in class II, 21% in class III and 5% were in class IV. In the EuroQol registration, 54% of the patients declared they had no mobility problems, 85% no problems with self-care, and 65% no problems with usual activities. However, 60% suffered from moderate pain or discomfort, and 33% from anxiety or depression. On the visual analogue scale (mean 63.5), 13% of the patients scored >90, 68% between 50 and 90, and 19% of the patients <50.

CONCLUSION

The long-term results of cumulative survival and cardiac survival, and NYHA class in our patient population who underwent RECABG are comparable with other studies. Quality of life is acceptable regarding the high risk of a RECABG.

Identification of patients at risk for early out-of-hospital mortality after redocoronary artery surgery

OBJECTIVE

Analyse risk factors and construct a predictive model for identification of patients at risk of early out-of-hospital mortality after coronary reoperations (RECABG).

METHODS

505 patients, discharged from hospital after a RECABG (1987-1998), were studied by univariate and multivariate analysis. A stepwise selective procedure (p<0.05) was used to identify a subset of variables with prognostic value for early out-of-hospital mortality. This subset was used to calculate a prognostic score 'S' and a predicted probability 'p' for early out-of-hospital mortality, p=1/1+ e^-s. Sensitivity analysis was used for evaluation.

RESULTS

The best predictive variables for early out-of-hospital mortality were diabetes (p=0.002), lung disease (p=0.05), emergency operation (p=0.0001) and a perioperative myocardial infarction (p=0.0001). Emergency operation (p=0.001) and antegrade/retrograde cardioplegia (p<0.0000) were independent predictors of a perioperative myocardial infarction. The prognostic accuracy (ROC area) was 86%. Patients were classified into low risk (5%), intermediate risk (15%), high risk (30%) and very high risk (≥40%). A predicted probability of ≥0.40 was used as cut-off point. The specificity of this test was 99%, sensitivity 33%, predictive value of a positive test 79%, and 95% for a negative test.

CONCLUSION

The results show that patients discharged from hospital after RECABG can be stratified according to their early out-of-hospital risk. A perioperative myocardial infarction is the major independent risk factor and can be affected by use of retrograde cardioplegia.

Papillary fibroelastoma of the mitral valve

We present a case of a 69-year-old woman with a history of stroke five years previously and an abnormal ECG prior to eye surgery. There were no signs of cardiac disease. Echocardiography disclosed a tumour of the papillary muscle. Surgical excision was performed and histological examination confirmed the diagnosis of a papillary fibroelastoma.

Smoking behaviour of patients undergoing cardiac surgery

OBJECTIVES

Investigate smoking behaviour and opinions on tobacco use in patients undergoing cardiac surgery.

METHODS

In this descriptive study, 200 patients were preoperatively asked to complete a questionnaire on their 'smoking habits'. Smoking behaviour, smoking cessation, tobacco and health, smoking in hospital and smoking after the operation were the main subjects. Eighty percent of the questionnaires (161 patients) could be used in the study. The total group was divided into three groups: group A: patients smoking at the moment of hospitalisation, group B: patients who had stopped smoking and group C: patients who had never smoked.

RESULTS

There is a difference in the answers between the three groups. For most patients the relation between tobacco use and cardiovascular disease is not clear; there is obviously an information gap. More than 50% of the patients do not agree with smoking in hospital, not even in 'smokers rooms'. Most patients have the intention of stopping smoking after their heart operation. This is an individual decision and support seems minimal.

CONCLUSION

This study confirms that the relation between smoking and cardiovascular diseases is not clear for many cardiac patients. Hospitalisation can be a good moment for smoking cessation, but support is necessary.

A nineteen-millimetre aortic valve prosthesis: is this really a risk?

BACKGROUND

Aortic valve replacement in patients with a small aortic root is a subject of ongoing controversy. We summarised our clinical experience with aortic valve replacement with 19 mm valves and combined this with a review of literature.

METHODS

Between January 1994 and December 1999, 603 patients underwent aortic valve replacement; 51 of these patients (8.3%) received a 19 mm heart valve prosthesis. The mean age was 72±9.7 years. Twenty-eight patients had concomitant coronary artery disease, six patients a combined mitral or tricupid valve disease. In four patients, the intervention was a reoperation. The mean EuroSCORE of the total group was 6.4±2.8, and 34 patients had a high operative risk.

RESULTS

Hospital mortality was 7.8% (4/51 patients). Follow-up of 47 hospital survivors was complete. At 12 months the survival was 90%, at 24 months 85% and at 48 months 60%. NYHA class improved at least one class in 35 patients (85%), and 34 patients declared that their quality of life had improved since the operation.

CONCLUSION

Aortic valve replacement with a small (19 mm) prosthesis can be performed with an acceptable operative mortality and results in excellent symptomatic improvement and quality of life.