Bert Arnrich

Prevalence and Risks of Undiagnosed Diabetes Mellitus in Patients Undergoing Coronary Artery Bypass Grafting

Background— Numerous studies have shown that diabetes mellitus (DM) is not identified and, consequently, inadequately treated in a substantial proportion of the patients in the general population. We know very little about the extent and the consequences of undiagnosed diabetes in the risk group of patients with coronary heart diseases. The objective of this study was therefore to determine the prevalence and the risks of undiagnosed DM among patients with coronary artery bypass. Methods and Results— The data of 7310 patients who have undergone coronary bypass operations between 1996 and 2003 were analyzed. Depending on their diagnosis on admission and their fasting plasma glucose (FPG) level, these patients were classified as known diabetics, undiagnosed diabetics (FPG ≥126 mg/dL), or as nondiabetics (FPG <126 mg/dL) and were compared in terms of their preoperative, intraoperative, and postoperative characteristics. Among the patients with coronary bypass that we examined, we found a prevalence of diagnosed diabetics of 29.6%. The prevalence of patients with undiagnosed DM (FPG ≥126 mg/dL) was 5.2%. In comparison with the other groups (non-DM versus undiagnosed DM versus known DM), the undiagnosed diabetics more frequently required resuscitation (1.7% versus 4.2% versus 1.5%; P<0.01) and reintubation (2.1% versus 5.0% versus 3.5%; P<0.01) and often showed a longer period of ventilation >1 day (5.6% versus 10.5% versus 7.4%; P<0.01). Perioperative mortality rate was highest in this group (0.9% versus 2.4% versus 1.4%; P<0.01). Conclusions— This study is the first to publish the prevalence of undiagnosed diabetes mellitus in cardiac surgery. During the perioperative and postoperative courses, these patients displayed a substantially higher morbidity and mortality rate.

Evaluation of radiological features for breast tumour classification in clinical screening with machine learning methods

OBJECTIVEnIn this work, methods utilizing supervised and unsupervised machine learning are applied to analyze radiologically derived morphological and calculated kinetic tumour features. The features are extracted from dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) time-course data.nnnMATERIALnThe DCE-MRI data of the female breast are obtained within the UK Multicenter Breast Screening Study. The group of patients imaged in this study is selected on the basis of an increased genetic risk for developing breast cancer.nnnMETHODSnThe k-means clustering and self-organizing maps (SOM) are applied to analyze the signal structure in terms of visualization. We employ k-nearest neighbor classifiers (k-nn), support vector machines (SVM) and decision trees (DT) to classify features using a computer aided diagnosis (CAD) approach.nnnRESULTSnRegarding the unsupervised techniques, clustering according to features indicating benign and malignant characteristics is observed to a limited extend. The supervised approaches classified the data with 74% accuracy (DT) and providing an area under the receiver-operator-characteristics (ROC) curve (AUC) of 0.88 (SVM).nnnCONCLUSIONnIt was found that contour and wash-out type (WOT) features determined by the radiologists lead to the best SVM classification results. Although a fast signal uptake in early time-point measurements is an important feature for malignant/benign classification of tumours, our results indicate that the wash-out characteristics might be considered as important.

Creatinine clearance versus serum creatinine as a risk factor in cardiac surgery

BackgroundRenal impairment is one of the predictors of mortality in cardiac surgery. Usually a binarized value of serum creatinine is used to assess the renal function in risk models. Creatinine clearance can be easily estimated by the Cockcroft and Gault equation from serum creatinine, gender, age and body weight. In this work we examine whether this estimation of the glomerular filtration rate can advantageously replace the serum creatinine in the EuroSCORE preoperative risk assessment.MethodsIn a group of 8138 patients out of a total of 11878 patients, who underwent cardiac surgery in our hospital between January 1996 and July 2002, the 18 standard EuroSCORE parameters could retrospectively be determined and logistic regression analysis performed. In all patients scored, creatinine clearance was calculated according to Cockcroft and Gault. The relationship between the predicted and observed 30-days mortality was evaluated in systematically selected intervals of creatinine clearance and significance values computed by employing Monte Carlo methods. Afterwards, risk scoring was performed using a continuous or a categorical value of creatinine clearance instead of serum creatinine. The predictive ability of several risk score models and the individual contribution of their predictor variables were studied using ROC curve analysis.ResultsThe comparison between the expected and observed 30-days mortalities, which were determined in different intervals of creatinine clearance, revealed the best threshold value of 55 ml/min. A significantly higher 30-days mortality was observed below this threshold and vice versa (both with p < 0.001). The local adaptation of the EuroSCORE is better than the standard EuroSCORE and was further improved by replacing serum creatinine (SC) by creatinine clearance (CC). Differential ROC analysis revealed that CC is superior to SC in providing predictive power within the logistic regression. Variable rank comparison identified CC as the best single variable predictor, even better than the variable age, former number 1, and SC, previously number 9 in the standard set of EuroSCORE variables.ConclusionThe renal function is an important determinant of mortality in heart surgery. This risk factor is not well captured in the standard EuroSCORE risk evaluation system. Our study shows that creatinine clearance, calculated according to the Cockcroft and Gault equation, should be applied to estimate the preoperative renal function instead of serum creatinine. This predictor variable replacement gains a significant improvement in the predictive accuracy of the scoring model.

Preoperative high leukocyte count: a novel risk factor for stroke after cardiac surgery

BACKGROUNDnStroke after cardiac surgery is a devastating complication. The relationship between white blood cell count (WBC) and perioperative cerebrovascular accident (CVA) has not been investigated. An effort was made to identify how preoperative WBC may relate to CVA development during or after cardiac surgery.nnnMETHODSnProspective data were collected from 7,483 patients who underwent coronary artery bypass grafting or valvular surgery or both. WBC was determined preoperatively and postoperatively. Differentiation of WBC was examined only preoperatively.nnnRESULTSnThere were a total of 125 CVAs (10 transient ischemic attacks [TIAs], 115 strokes). WBC was significantly higher preoperatively and directly postoperatively in patients with stroke. Qualitative changes in preoperative WBC were also found in these patients (chi2; p < 0.001). The predictive power of the stepwise logistic regression model for CVA was greater when preoperative WBC was included. The risk for perioperative CVA increased starting at preoperative WBC of 9 x 10(9)/L (p = 0.044) and progressed in higher WBC ranges. WBC had a significant impact on CVA outcome (analysis of variance, p = 0.001).nnnCONCLUSIONSnOur studies have established the correlation between high preoperative WBC and stroke during or after cardiac surgery. Furthermore, elevated preoperative WBC was related to the clinical outcome of CVA. Preoperative measures aimed at preventing or treating conditions such as infections that may cause elevated WBC may be beneficial in the prevention of stroke during or after cardiac surgery.

Is age an independent determinant of mortality in cardiac surgery as suggested by the EuroSCORE

BackgroundThe proportion of older patients in cardiac surgery is continuously increasing. 37% of patients undergoing heart surgery in Germany in the year 2000 were 70 years of age and older. We have studied the role of age as a determinant of mortality in cardiac surgery in our institutional patient population.MethodsWe have calculated the EuroSCORE and the corresponding age-adjusted EuroSCORE in 8769 patients who underwent heart surgery between January 1996 and January 2002 and collected the information on the occurrence of postoperative complications and 30-days mortality.ResultsThe multimorbidity increased with ascending age. Both the EuroSCORE and the age-adjusted EuroSCORE values increased significantly with age in the whole group of patients as well as in the group of patients who were alive 30 days after heart surgery. The incidence of postoperative complications and 30-days mortality increased significantly with age. In patients who died within 30 days after surgery, the EuroSCORE increased significantly with age, whereas the age-adjusted EuroSCORE did not. The occurrence of diabetes mellitus, arterial hypertension and atrial fibrillation, i.e., the risk factors not considered by the EuroSCORE, exhibited a significant age dependence in our patients. The univariate analysis identified the significant dependence of 30-days mortality on diabetes and atrial fibrillation. The stepwise logistic regression analysis showed the dependence of mortality on diabetes.ConclusionsOn the background of the well-known age-dependent structural and functional changes of different body organs, our data show that age is a significant risk indicator in cardiac surgery, strongly correlating with morbidity and mortality. Consequently, special preventive and therapeutic measures are required in clinical environment in the case of elderly patients undergoing cardiac surgery.

Impact of age on the results of coronary artery bypass grafting.

As the average age of patients undergoing cardiac surgery is increasing, the effects of age on the incidence of postoperative complications and 30-day mortality after coronary artery bypass grafting were examined. The EuroSCORE and corresponding age-stripped EuroSCORE were calculated in 6,057 patients who underwent isolated coronary bypass between January 1996 and January 2002. Both EuroSCORE and age-stripped EuroSCORE exhibited a significant increase with age in the whole group of patients and in those who were alive 30 days after surgery. The 30-day mortality and the incidence of postoperative complications increased significantly with age. A significant age-dependent increase in EuroSCORE was found in patients who died within 30 days postoperatively, whereas no age dependence was observed in the age-stripped EuroSCORE. Univariate analysis showed diabetes mellitus and atrial fibrillation to be significant risk factors for 30-day mortality; atrial fibrillation was also found to significantly affect 30-day mortality on multivariate analysis. In view of the increasing co-morbidity and age-dependent organ changes in the elderly, specific preventive and therapeutic measures are needed in this group of patients undergoing cardiac surgery.

Is there any impact of the shape of aortic end-hole cannula on stroke occurrence? Clinical evaluation of straight and bent-tip aortic cannulae

Objective: To compare the impact of straight and bent-tip aortic cannulae on stroke occurrence, location, and severity. Methods: Prospective data were collected on 8129 patients (coronary artery bypass grafting (CABG) and/or valvular surgery). ‘Bent-tip’ aortic cannulae were used in 15.6% of cases and ‘straight’ end-hole cannulae in 84.4% of cases. Results: There were a total of 137 strokes: right anterior 52, left anterior 39, bilateral 23, posterior 18, and location not established5. With the use of bent-tip cannulae, the incidence of strokes was 0.9% versus 1.8% with straight cannulae (c2, p=0.026). Bilateral and posterior strokes occurred more often with the use of straight cannulae (c2, p = 0.015). Straight cannulae also related to the severity of strokes (c2, p = 0.003). Conclusions: There is an influence of the type of cannula on the occurrence, location, and severity of strokes. Straight cannulae cause significantly more often and more severe bilateral and posterior strokes than bent-tip cannulae.

Diabetes mellitus as a risk factor for pulmonary complications after coronary bypass surgery

OBJECTIVESnIn the past few years there has been increasing evidence that the respiratory function of patients with diabetes is impaired in the course of their disease. The objective of this article was to investigate whether patients with diabetes are particularly at risk of pulmonary complications during the perioperative stage of coronary bypass surgery.nnnMETHODSnThe data of 8555 patients who had undergone coronary bypass operations in the years between 1996 and 2004 were analyzed. Depending on their diagnosis on admission and their fasting plasma glucose levels, these patients were classified as having no diabetes (fasting plasma glucose level < 126 mg/dL), undiagnosed diabetes (glucose level > or = 126 mg/dL), oral therapy diabetes, or insulin-treated diabetes. The 3 diabetic groups were compared with the nondiabetic group in terms of the preoperative and postoperative characteristics.nnnRESULTSnThe reintubation rate among patients with undiagnosed diabetes (4.6%) and among those with insulin-treated diabetes (4.5%) was significantly higher than that of nondiabetic patients (1.8%; P < .01). The proportion of patients who required respiration for periods longer than 1 day was also significantly higher among patients with undiagnosed diabetes (9.9%) and those with insulin-treated diabetes (8.6%) than among the nondiabetic patients (4.8%; P < .01). The regression models show that unidentified diabetes and insulin-treated diabetes constitute independent risk factors for perioperative pulmonary complications.nnnCONCLUSIONSnPatients with undiagnosed and insulin-treated diabetes have a higher risk of having pulmonary complications in the perioperative course of coronary bypass operations than do nondiabetic patients. These results may be explained if one considers the lung as another target organ of the diabetic disease.

Gabor filters for object localization and robot grasping

We present a system for learning the 3 DOF fine-positioning task of a robot manipulator (Puma 260) using a gripper mounted camera. Small lateral gripper-target misalignments are corrected in one step. Larger ones employ a previous coarse adjustment move in order to bound the parallax effects of the close camera focus. We build object specialized, neural network-based pose estimators with a rather small set of Gabor filters. Gabor filters perform a spatially localized frequency analysis and resemble the spatial response profile of receptive fields found in visual cortex neurons. The system demonstrates efficiency w.r.t. speed and accuracy, as well as robustness against changing illumination and object conditions.

Ist das Alter eine unabhängige Determinante der Letalität in der Herzchirurgie, wie es im EuroScore behauptet wird?

Zusammenfassung. Der Anteil älterer Patienten in der Herzchirurgie nimmt zu. 37% der am Herzen in Deutschland operierten Patienten im Jahre 2000 waren 70 Jahre alt oder älter. Wir haben in unserem Patientengut die Frage untersucht, ob das Alter eine unabhängige Determinante der Letalität in der Herzchirurgie darstellt. u2002u2009u2009Bei 8769 Patienten, die im Zeitraum Januar 1996 bis Januar 2002 am Herzen operiert wurden, berechneten wir den EuroScore sowie den entsprechenden altersbereinigten EuroScore und erfassten die postoperativen Komplikationen sowie die 30-Tage-Letalität. Die Multimorbidität nahm mit dem Alter zu. Sowohl der EuroScore als auch der altersbereinigte Wert zeigten einen signifikanten Zuwachs mit steigendem Alter bei der Gesamtgruppe und bei den Patienten, die den 30. postoperativen Tag überlebten. Die 30-Tage-Letalität und die postoperativen Komplikationen stiegen mit dem Alter signifikant an. Während der EuroScore bei Patienten, die innerhalb von 30 Tagen nach der Operation verstarben, eine signifikante altersabhängige Zunahme zeigte, war bei dem altersbereinigten EuroScore keine signifikante Änderung mit dem Alter zu verzeichnen. Das Vorkommen von Diabetes mellitus, arterieller Hypertonie und Vorhofflimmern, Faktoren die im EuroScore nicht berücksichtigt werden, zeigte ebenfalls eine signifikante Altersabhängigkeit. Bei der univariaten Analyse war eine signifikante Abhängigkeit der 30-Tage-Letalität von Diabetes mellitus und Vorhofflimmern festzustellen. Die stufenweise logistische Regressionsanalyse zeigte eine Abhängigkeit der Letalität von Diabetes mellitus. u2002u2009u2009Unter Berücksichtigung der aus der Literatur bekannten altersbedingten strukturellen und funktionellen Änderungen verschiedener Organe zeigen unsere Daten, dass das Alter einen mit der Morbidität und Letalität hoch korrelierenden bündelnden Risikoindikator in der Herzchirurgie darstellt. Als klinische Konsequenz sind besondere vorbeugende und therapeutische Maßnahmen bei älteren herzchirurgischen Patienten erforderlich.Summary. The number of “older” patients undergoing cardiac surgery is steadily increasing. In the year 2000, 37% of all patients who underwent a cardiac operation in Germany were 70 years of age or older. Looking at data form our institution, we focused on the topic, whether age on its own is an independent determinant for mortality in cardiac surgery. u2002u2009u2009Data from 8769 patients who underwent cardiac surgery in our institution from January 1996 until January 2002 were analyzed. For all patients, EuroScore and the corresponding age-stripped value was calculated. All recorded postoperative complications and 30-day mortality were statistically analyzed. u2002u2009u2009EuroScore as well as the age-stripped EuroScore showed a significant rise with increasing age in the total number of patients as well as in the patients, who did not die during the first 30 days after the operation. The 30 day mortality and the incidence of postoperative complications increased significantly with age. While the EuroScore showed a significant age-dependant increase in patients who died within 30 days after the operation, the age-stripped EuroScore did not reveal a significant discrepancy in mortality with respect to age. Arterial hypertension, diabetes mellitus and atrial fibrillation, parameters not mentioned in EuroScore, showed significant differences among age groups. According to univariate analysis, arterial hypertension and diabetes mellitus were significant predictors of mortality. Entered into a multivariate logistic regression analysis, only diabetes mellitus achieved statistical significance. u2002u2009u2009Our data and the known age-associated functional and structural changes of different organ systems show that age integrates risk factors together. In order to limit mortality in the steadily growing number of older and multi-morbid patients undergoing cardiac surgery, exceptional emphasis has to be put on patient selection and therapeutic measures to improve preoperative status.