Prediction of Wenckebach Behavior and Block Response in DDD Pacemakers

At higher atrial rates, the behavior of a DDD pulse generator will depend on the atrial rate or spontaneous atrial interval (SAI) and the settings of the pacemaker: upper rate interval (URI), atrioventricular interval (AVI), and atrial refractory interval (ARI). An algorithm was developed enabling the prediction of the degree of Wenckebach block using the parameters mentioned above. In the absence of the programmed settings of the pacemaker, these parameters can be determined by noninvasive methods. AVI can be measured by application of a magnet over the pulse generator, while URI and ARI can be estimated during chest wall stimulation by progressively increasing the frequency of the external extrastimuli. The use of the formula in combination with chest wall stimulation allows the evaluation of the proper functioning of any DDD pacemaker during exercise and in patients with atrial rhythm disturbances, even when no information about the pacemaker settings is available.     

Complicated Forms of Tachycardia‐Mediated Cardiomyopathy Associated with Idiopathic Left Ventricular Tachycardia

Idiopathic left ventricular tachycardia is an infrequent form of ventricular tachycardia associated with a structurally normal heart. The prognosis is usually benign; however, sustained cases have been reported. In this report, we describe two cases of persistent idiopathic left ventricular tachycardia complicated by tachycardia‐mediated cardiomyopathy. In the first case, the patient developed a right ventricular thrombus with subsequent pulmonary embolism. In the second case, the patient developed acute pulmonary edema. Both cases were cured by catheter ablation. (PACE 2011; e52–e55)     

Immunoelectron-microscopic Localization of Immunoglobulin A and Secretory Component in Jejunal Mucosa from Children with Coeliac Disease

Using peroxidase-labelled antibodies, the ultrastructural localization of IgA and secretory component (SC) was investigated in duodeno-jejunal biopsies from six children with coeliac disease and compared with that observed in non-coelic mucosa. In normal intestinal mucosa this study confirmed the presence of IgA in the rough endoplasmic reticulum and the perinuclear space of numerous subepithelial plasma cells and one the lateral cell membranes of villous and especially crypt epithelial cells. SC was only detected in the epithelium and principally in crypt epithelium where it was identified in endoplasmic reticulum, Golgi saccules, perinuclear spaces and on lateral cell membranes. These findings support the suggestion that SC is synthesized mainly in crypt epithelium and acts as a receptor on epithelial cell membranes for dimeric IgA. In untreated coeliac patients, SC was observed at the same sites, but SC staining was reduced in damaged surface epithelial cells. The number of IgA immunocytes was increased and heavy deposits of IgA were found on basement membranes. In post-treatment biopsies, no abnormality was apparent. After re-exposure to gluten, depositions of IgA on basement membranes were the only early change. The unaltered distribution of SC and IgA in crypt epithelium strongly suggests that the epithelial transport mechanism of secretory IgA is normal in coeliac disease.     

A COMPARISON OF NSP-RETICULONS WITH CONVENTIONAL NEUROENDOCRINE MARKERS IN IMMUNOPHENOTYPING OF LUNG CANCERS

Neuroendocrine-specific protein (NSP)-reticulons are endoplasmic reticulum-associated protein complexes, which have been identified as markers for neuroendocrine differentiation. In this study, the expression of two members of the family of NSP-reticulons, NSP-A and NSP-C, have been investigated in different types of lung cancer and compared with the expression patterns of five conventional neuroendocrine markers, the neural cell adhesion molecule (NCAM), synaptophysin, chromogranin A, Leu-7, and neurofilament proteins. NSP-A and NSP-C antibodies were reactive with most carcinoid tumour and small cell lung carcinoma (SCLC) cases, while atypical carcinoid tumours showed a variable expression. In the total group of neuroendocrine tumours, a high concordance of expression was found between NSP-A and NSP-C, while their expression correlated well with NCAM and synaptophysin positivity. Chromogranin A, Leu-7, and neurofilament proteins were shown to be expressed to a limited extent in these neuroendocrine tumours. In a selected group of non-SCLCs known to exhibit neuroendocrine features, NSP-A expression was detected at much higher frequency than NSP-C. In virtually all NSP-A positive cases, this expression was associated with one or more of the other neuroendocine markers. NSP-A expression showed a stronger correlation with conventional neuroendocrine markers than NCAM. In detecting neuroendocrine differentiation in non-SCLC, NSP-A is more sensitive than synaptophysin, chromogranin A, Leu-7, and neurofilament proteins. It is concluded that NSP-reticulons are valuable markers in the diagnosis of neuroendocrine differentiation in non-SCLC and should be used in conjunction with NCAM. © 1997 John Wiley & Sons, Ltd.     

Circulating soluble tumor necrosis factor receptors,interleukin-2 receptors,tumor necrosis factor α, and interleukin-6 levels in rheumatoid arthritis.

Objective. To assess whether circulating concentrations of soluble tumor necrosis factor receptors (sTNFR; p55 and p75), soluble interleukin-2 receptors (sIL-2R), tumor necrosis factor α (TNFα), and interleukin-6 (IL-6) reflect clinical response and whether changes are dependent on the drug used in rheumatoid arthritis (RA) patients taking methotrexate (MTX) or azathioprine (AZA). Methods. These cytokines and soluble receptors were assessed in 20 control subjects and serially for up to 48 weeks in 61 RA patients, by bioassay (IL-6) and immunoassays (sTNFR, sIL-2R, TNFα, and IL-6). Results. Concentrations of p55 and p75, sIL-2R, and TNFα (but not IL-6) were significantly higher in RA patients than in controls. Significant decreases in sIL-2R and p55 concentrations were associated with clinical improvement and were observed in patients treated with MTX, but not AZA. Both treatments induced decreases in IL-6 concentrations, but circulating AZA (or its metabolites) appears to interfere with the measurement of IL-6 bioactivity. TNFα and p75 levels did not show significant changes. Conclusion. Measurement of circulating sIL-2R, p55, and IL-6 may be useful in the evaluation of RA disease activity and response to therapy. Interference by circulating levels of drugs must be ruled out when bioassays are used to evaluate cytokine levels.