A new method to assess ventricular wall stress in patients with heart failure and its relation to heart rate variability.

INTRODUCTION: Heart failure is characterized by an increase in cardiac load, wall stress and autonomic dysfunction. The neurohumoral imbalance arising from adrenergic activation and parasympathetic withdrawal is associated with worse prognosis. We addressed the hypothesis that an increased left ventricular (LV) wall stress as assessed by cardiac magnetic resonance imaging (CMR) in patients with heart failure is related to a depression of heart rate variability (HRV). METHODS: Cardiac function and mass were measured in 37 individuals with suspected cardiomyopathy using CMR imaging. A thick-walled sphere model was used to calculate ventricular wall stress. Time domain analysis of HRV was obtained by long-term Holter ECG. RESULTS: Standard deviation of both normal-to-normal (NN) intervals (SDNN) and average NN intervals over 5 minutes (SDANN-i) were negatively correlated with LV enddiastolic wall stress (r = 0.42, P < 0.01). SDNN and SDANN-i were severely decreased (P < 0.01) in patients with increased enddiastolic LV wall stress > 12 kPa (vs. normal range: < 4 kPa). CONCLUSION: A relation between increased cardiac wall stress and depressed heart rate variability was observed in patients with heart failure. CMR-based measurement of LV volume and mass is appropriate to calculate LV wall stress which should be considered not only as a potential prognostic determinant but also as therapeutic target.

B-type natriuretic peptide and wall stress in dilated human heart.

Background Although B-type natriuretic peptide (BNP) is used as complimentary diagnostic tool in patients with unknown thoracic disorders, many other factors appear to trigger its release. In particular, it remains unresolved to what extent cellular stretch or wall stress of the whole heart contributes to enhanced serum BNP concentration. Wall stress cannot be determined directly, but has to be calculated from wall volume, cavity volume and intraventricular pressure of the heart. The hypothesis was, therefore, addressed that wall stress as determined by cardiac magnetic resonance imaging (CMR) is the major determinant of serum BNP in patients with a varying degree of left ventricular dilatation or dysfunction (LVD). Methods A thick-walled sphere model based on volumetric analysis of the LV using CMR was compared with an echocardiography-based approach to calculate LV wall stress in 39 patients with LVD and 21 controls. Serum BNP was used as in vivo marker of a putatively raised wall stress. Nomograms of isostress lines were established to assess the extent of load reduction that is necessary to restore normal wall stress and related biochemical events. Results Both enddiastolic and endsystolic LV wall stress were correlated with the enddiastolic LV volume (r = 0.54, P < 0.001; r = 0.81, P < 0.001). LV enddiastolic wall stress was related to pulmonary pressure (capillary: r = 0.69, P < 0.001; artery: r = 0.67, P < 0.001). Although LV growth was correlated with the enddiastolic and endsystolic volume (r = 0.73, P < 0.001; r = 0.70, P < 0.001), patients with LVD exhibited increased LV wall stress indicating an inadequately enhanced LV growth. Both enddiastolic (P < 0.05) and endsystolic (P < 0.01) wall stress were increased in patients with increased BNP. In turn, BNP concentration was elevated in individuals with increased enddiastolic wall stress (>8 kPa: 587 +/- 648 pg/ml, P < 0.05; >12 kPa: 715 +/- 661 pg/ml, P < 0.001; normal < or =4 kPa: 124 +/- 203 pg/ml). Analysis of variance revealed LV enddiastolic wall stress as the only independent hemodynamic parameter influencing BNP (P < 0.01). Using nomograms with "isostress" curves, the extent of load reduction required for restoring normal LV wall stress was assessed. Compared with the CMR-based volumetric analysis for wall stress calculation, the echocardiography based approach underestimated LV wall stress particularly of dilated hearts. Conclusions In patients with LVD, serum BNP was increased over the whole range of stress values which were the only hemodynamic predictors. Cellular stretch appears to be a major trigger for BNP release. Biochemical mechanisms need to be explored which appear to operate over this wide range of wall stress values. It is concluded that the diagnostic use of BNP should primarily be directed to assess ventricular wall stress rather than the extent of functional ventricular impairment in LVD.

Relation of B-type natriuretic peptide to left ventricular wall stress as assessed by cardiac magnetic resonance imaging in patients with dilated cardiomyopathy.

Ventricular loading conditions are crucial determinants of cardiac function and prognosis in heart failure. B-type natriuretic peptide (BNP) is mainly stored in the ventricular myocardium and is released in response to an increased ventricular filling pressure. We examined, therefore, the hypothesis that BNP serum concentrations are related to ventricular wall stress. Cardiac magnetic resonance imaging (MRI) was used to assess left ventricular (LV) mass and cardiac function of 29 patients with dilated cardiomyopathy and 5 controls. Left ventricular wall stress was calculated by using a thick-walled sphere model, and BNP was assessed by immunoassay. LV mass (r = 0.73, p < 0.001) and both LV end-diastolic (r = 0.54, p = 0.001) and end-systolic wall stress (r = 0.66, p < 0.001) were positively correlated with end-diastolic volume. LV end-systolic wall stress was negatively related to LV ejection fraction (EF), whereas end-diastolic wall stress was not related to LVEF. BNP concentration correlated positively with LV end-diastolic wall stress (r = 0.50, p = 0.002). Analysis of variance revealed LV end-diastolic wall stress as the only independent hemodynamic parameter influencing BNP (p < 0.001). The present approach using a thick-walled sphere model permits determination of mechanical wall stress in a clinical routine setting using standard cardiac MRI protocols. A correlation of BNP concentration with calculated LV stress was observed in vivo. Measurement of BNP seems to be sufficient to assess cardiac loading conditions. Other relations of BNP with various hemodynamic parameters (e.g., EF) appear to be secondary. Since an increased wall stress is associated with cardiac dilatation, early diagnosis and treatment could potentially prevent worsening of the outcome.

Impairment of peroxisomal structure and function in rat liver allograft rejection: prevention by cyclosporine.

BACKGROUND: During allograft rejection, cytokines and lipid mediators contribute to cell injury and organ failure. Peroxisomes play a crucial role in lipid metabolism, including the degradation of lipid mediators by peroxisomal beta-oxidation. Therefore, we investigated the alterations of hepatic peroxisomes after allogeneic rat liver transplantation. METHODS: MHC-incompatible Dark Agouti (RT1a) donor rats and Lewis (RT1(1)) recipient rats were used for allogeneic transplantation. For immunosuppression, a group of these animals received cyclosporine (CsA) intraperitoneally (1 mg/kg body weight per day). Lewis rats were used for isogeneic transplant combination. Ten days after transplantation, livers were investigated using morphometrical methods for determination of peroxisomal diameter and volume density. The activities of peroxisomal catalase (CAT) and acyl-coenzyme A oxidase (AOX) were determined, and the corresponding proteins were evaluated by quantitative immunocytochemistry and immunoblotting. The expressions of mRNAs encoding CAT and AOX were investigated by Northern blotting. RESULTS: The volume density and diameter of peroxisomes were significantly decreased in allogeneic transplanted livers but were unchanged in CsA-treated animals. Both the activities of CAT and AOX and their protein levels were significantly reduced in liver allografts. Moreover, the corresponding mRNA levels of CAT and AOX were decreased significantly in liver allografts, whereas CsA treatment led to an increase of those mRNAs. Isogeneic transplanted livers showed only a slight reduction of the corresponding enzyme values. CONCLUSIONS: Peroxisomes are severely affected both morphologically and functionally after allogeneic liver transplantation. These results suggest that impairment of peroxisomal lipid beta-oxidation could contribute to the pathogenesis of the rejection process by decreased catabolism of lipid mediators involved in the regulation of the inflammatory response. CsA, in addition to its immunosuppressive effects, may contribute to allograft survival by maintenance of those important peroxisomal functions.

Significant increase of Kuppfer cells associated with loss of Na+,K+-ATPase activity in rat hepatic allograft rejection.

BACKGROUND: Cholestasis is a complication that occurs during the rejection of liver transplants. The aim of this study was to investigate the association of activated Kupffer cells (KCs) and Na+,K+-ATPase activity for taurocholate cotransport and bile canalicular (BC) Mg++-ATPase activity for hepatobiliary excretion in rat liver allograft. METHODS: Quantitative analyses of KC number and size in relationship to enzyme activity of Na+,K+-ATPase and of BC Mg++-ATPase were conducted in rejected liver after allogenic transplantation and after prevention of rejection using cyclosporine. RESULTS: The animals were examined on the 10th postoperative day. In the rejection group, the number of KCs significantly increased more than fourfold in comparison with the number of KCs in the control livers. Some KCs were found in the sinusoids, but the majority were located in the space of Disse. Na+,K+-ATPase activity vanished from the basolateral plasma membrane, whereas BC Mg++-ATPase activity was restored in the apical domain. With immunosuppression, KCs showed the same behavior as in the control group, and activity of both ATPases was observed as strong electron-dense precipitates in basolateral and apical plasma membrane domains. CONCLUSIONS: In this study, we demonstrate that activated KCs migrate into the donor liver and release cytokines, which leads to the loss of Na+,K+-ATPase activity in the rejection group. BC Mg++-ATPase activity was not influenced by these mediators of activated macrophages. Since Na+,K+-ATPase is the cotransporter for hepatocyte taurocholate uptake, these data may contribute to understanding the mechanisms for cholestasis during hepatic allograft rejection.

[Forearm fractures in children]. / Frakturen im Bereich des Unterarms bei Kindern.

A total of 285 children out of an 8 year period with fractures of the forearm were studied. Of these 175 (62.2%) had a fracture of the distal radius and 51 (18.2%) had a fracture of the distal forearm and there were 42 (14.7%) fractures in the middle or proximal third in this region. Three children with injuries of the distal radial epiphysis had to be treated by percutaneous wire fixation. Except for 2 cases who needed surgery all severe dislocated forearm fractures could be treated by closed reduction. In all cases the children were immobilized with a long upper arm cast for 3 to 4 weeks. Follow-up examinations up to 6 years after injury showed excellent results in distal forearm and distal radial fractures whereas results were only satisfactory in midshaft forearm fractures.