Matrix metalloproteinases in inflammatory demyelination: targets for treatment

Matrix metalloproteinases (MMPs) degrade all protein components of the extracellular matrix. Functionally, they contribute to several different physiologic conditions, such as angiogenesis or bone remodeling, as well as pathologic conditions in humans, such as rheumatoid arthritis and tumor growth. MMPs seem to be important in the pathogenesis of inflammatory demyelinating diseases of the central and peripheral nervous system, especially in MS and in Guillain-Barré syndrome (GBS). Key mechanisms in the genesis of inflammatory demyelination, such as leukocyte recruitment, blood-brain barrier or blood-nerve barrier breakdown, myelin destruction, and release of disease-promoting cytokines, are considered to be MMP-dependent processes. In experimental autoimmune encephalomyelitis, an animal model of MS, and experimental autoimmune neuritis, an animal model of GBS, different synthetic inhibitors targeting MMP activity are able to suppress and even reverse ongoing disease. This evidence points to MMPs as new targets for treatment in inflammatory demyelination.

[Matrix metalloproteinases. Potential targets for new treatments in inflammatory demyelinating diseases of the nervous system]

Inflammatory demyelinating diseases of the nervous system, such as multiple sclerosis or the Guillain-Barré syndrome represent severely disabling disorders, often seen by the neurologist, with still only limited means for therapeutical intervention. The underlying pathomechanisms remain in large part elusive, however mounting evidence suggests that enzymes of the family of matrix metalloproteinases are of relevance in the pathogenesis of these disorders. Experimental in vivo data as well as results from other medical fields emphasize that the selective inhibition of these proteases could be a promising therapeutical approach. The following review summarizes the role of matrix metalloproteinases in inflammatory demyelinating diseases of the central as well as peripheral nervous system and discusses the therapeutical application of synthetic inhibitors in these disorders.

[Perioperative cost analysis of cemented versus uncemented total hip endoprostheses for clinical and economic management. Postoperative follow-up study over one year]

QUESTIONS

Are there and what are the differences between in-patient and out-patient costs for cemented or noncemented hip prosthesis? How to make it possible to keep in-patient costs within the limit of the a special global amount ("Fallpauschale")?

METHODS

In this study we compared in-patient and out-patient costs of 30 patients with cemented and 30 patients with noncemented hip prosthesis during the first year after surgery. We developed a perioperative management in order to keep the costs in the limits of the "Fallpauschale".

RESULTS

The average in-patient cost for the cemented prosthesis group was DM 19.644,89 and for the non-cemented group DM 20.485,33. In both groups these costs went beyond the "Fallpauschale" (DM 18.643,80). Comparing the two groups we found significant differences in costs for the endoprosthesis and for laboratory costs. We discovered a suitable perioperative management to keep costs below the "Fallpauschale".

CONCLUSION

Using an appropriate perioperative management it is possible to keep costs in the given limits.

[Results of testing defibrillator function of implanted cardioverter/defibrillators]

Postoperative tests of implantable cardioverter defibrillators (ICDs) are routinely performed to ensure appropriate defibrillation by the device. However, efficacy and complications of this procedure are unknown. To scrutinize the currently accepted indications to test the defibrillation function of the ICD we retrospectively analyzed 844 ICD-tests in 439 ICD-systems and 409 patients. 755 ICD-tests (89.4%) were routinely performed (57% before discharge and 43% during follow-up); 58 tests (6.9%) were performed after a change of the antiarrhythmic drug regimen, 24 tests (2.9%) after a revision of a part of the ICD-system, and seven tests (0.8%) because of a suspected dysfunction of the ICD. During routine-tests six ICD-systems (0.8%) failed to defibrillate the patient. However, in all but one test abnormalities of the ICD-system had been observed before the test. After addition of antiarrhythmic drugs, three of 58 ICD-systems (5.2%) failed to defibrillate the patient during the test (amiodarone: n = 2, flecainide: n = 1). Four of seven ICD-systems (57%) tested due to a suspected dysfunction failed to defibrillate the patient. After revisions of parts of the ICD-systems, ICD-tests never revealed a failure of defibrillation. During 16 ICD-tests (1.9%) complications occurred. The most frequent complications was inappropriate shocks (n = 10; 1.2%), the most severe one (transient) neurologic symptoms (n = 4; 0.48%). Our experience demonstrates that postoperative tests of the defibrillation function of ICDs rarely reveal ICD-dysfunction. As testing is unpleasant for the patient and not free of complications, tests might be restricted to those patients in whom an ICD-dysfunction is suspected (based on clinical presentation, results of chest-x-ray, testing of sensing signal and stimulation threshold) or class I or class III antiarrhythmic drugs have been added to the antiarrhythmic drug regimen.

Beta-blockers inhibit the modification of low-density lipoproteins by sodium hypochlorite in vitro

The effect of beta-blockers (alprenolol, oxprenolol, atenolol, acebutolol) and the non-steroidal anti-inflammatory drug, diclofenac, on modification of low-density lipoproteins (LDL) by sodium hypochlorite (NaOCl) was investigated in vitro. Beta-blockers and diclofenac inhibit the formation of thiobarbituric acid reactive substances in LDL modified by NaOCl. Beta-blockers, but not diclofenac, inhibit the hypochlorite-induced aggregation of LDL which was determined by photon correlation spectroscopy. The intracellular accumulation of cholesterol esters in J774 macrophages is inhibited by addition of beta-blockers, but not diclofenac, to LDL prior to the addition of NaOCl. The modification inhibiting effect of beta-blockers is inversely correlated to the binding capabilities of these substances to LDL which were assessed by laser electrophoresis. Inhibition of LDL modification in vivo by beta-blockers may reduce the risk of atherosclerosis and, therefore, compensate for the cholesterol-raising effect of these drugs in human plasma.

Cardiac output is not affected during intraoperative testing of the automatic implantable cardioverter defibrillator

INTRODUCTION

Perioperative mortality of patients undergoing implantation of automatic implantable cardioverter defibrillators (ICDs) has been reduced dramatically following the availability of transvenous-subcutaneous defibrillation leads. However, patients with severely reduced left ventricular function show a substantial rate of nonsudden cardiac mortality within the first year. Whether repeated intraoperative inductions of ventricular tachycardia/fibrillation (VT/VF) during implantation lead to hemodynamic deterioration and thus might contribute to development of end-stage heart failure in these patients is unknown. The purpose of the present study was to determine cardiac output and hemodynamic performance during transvenous-subcutaneous ICD implantation in patients with severe left ventricular dysfunction.

METHODS AND RESULTS

In 11 patients with a left ventricular ejection fraction (EF) < or = 0.35, cardiac output was measured automatically with a combined continuous cardiac output/mixed venous oxygen saturation pulmonary artery catheter system. ICD implantation was performed during standardized general anesthesia. In the 11 patients (EF = 27 +/- 2% [mean +/- SEM]) a total of 95 episodes of VT/VF followed by defibrillation were induced (episodes per patient = 9 +/- 1; range 6 to 11). Cardiac index was 2.2 +/- 0.2 L.min-1.m-2 after induction of anesthesia (before start of surgery), and 1.9 +/- 0.1 L.min-1.m-2 immediately before first induction of VT/VF. After the last episode of VT/VF, cardiac index was 2.1 +/- 0.2 L.min-1.m-2. Cardiac index measured 1, 2, and 3 minutes after induction of VT/VF was not significantly different when compared to the preinduction value during any episode of VT/VF induction. Similarly, stroke volume index was 39 +/- 5 mL.m-2 immediately before first induction of VT/VF and 36 +/- 3 mL.m-2 after the last episode of VT/VF (NS). At the end of surgery, hemodynamic parameters did not exhibit any significant difference when compared to the data obtained before start of ICD implantation and testing.

CONCLUSION

Extensive defibrillation tests during transvenous-subcutaneous ICD implantation in patients with severe left ventricular dysfunction are not associated with acute deterioration of cardiac performance.

Erroneous discharge of an implantable cardioverter defibrillator caused by an electric razor

We report an unusual case of the erroneous discharge of a third-generation multiprogrammable implantable cardioverter defibrillator in a 64-year-old patient with a history of recurrent ventricular tachycardias caused by electromagnetic interference while shaving with an electric razor. Electromagnetic interference was related to a defect in the electrode's insulation and could not be provoked in an intact electrode.

Method to estimate the rate and extent of intestinal absorption in conscious rats using an absorption probe and portal blood sampling

PURPOSE

A variety of methods exist which determine the rate and extent of intestinal absorption. The method described here employs an internal absorption reference probe and portal blood sampling in unanesthetized rat.

METHODS

Theophylline and tritiated water were selected as absorption reference probes since they are quantitatively absorbed in conscious rat. The fraction of an intestinal dose which reaches portal blood was determined from the resulting portal-systemic blood concentration gradients of the drug relative to the absorption probe. The absorption probes provide a means to calculate the drug mass reaching portal blood without the need of measuring the portal blood flow rate. The technique was evaluated with verapamil and a well-absorbed 5-lipoxygenase inhibitor, A-79035.

RESULTS

The fraction of an intrajejunal dose of A-79035 reaching the portal vein (FG) was 0.86 using theophylline as the absorption probe. Verapamil, which is susceptible to extensive hepatic first-pass elimination, was completely absorbed (FG = 0.98) within 1 hour, but was only 21.4% bioavailable. Absorption rate constants, estimated from initial appearance rates in portal blood, were used to monitor factors that affect drug absorption. For example, with a dose solution containing 30% PEG-400, the absorption rate constants of theophylline and A-79035 were significantly reduced. Anesthesia reduced the absorption rate constant for theophylline in rats by 40% compared to conscious animals.

CONCLUSIONS

The technique detailed here allows reliable, direct measurement of intestinal absorption which may assist in characterizing oral dosing for novel therapeutic agents.

Internal defibrillation with smaller capacitors: a prospective randomized cross-over comparison of defibrillation efficacy obtained with 90-microF and 125-microF capacitors in humans

INTRODUCTION

The size of current implantable cardioverter defibrillators (ICD) is still large in comparison to pacemakers and thus not convenient for pectoral implantation. One way to reduce ICD size is to defibrillate with smaller capacitors. A trade-off exists, however, since smaller capacitors may generate a lower maximum energy output.

METHODS AND RESULTS

In a prospective randomized cross-over study, the step-down defibrillation threshold (DFT) of an experimental 90-microF biphasic waveform was compared to a standard 125-microF biphasic waveform. The 90-microF capacitor delivered the same energy faster and with a higher peak voltage but provided only a maximum energy output of 20 instead of 34 J. DFTs were determined intraoperatively in 30 patients randomized to receive either an endocardial (n = 15) or an endocardial-subcutaneous array (n = 15) defibrillation lead system. Independent of the lead system used, energy requirements did not differ at DFT for the experimental and the standard waveforms (10.3 +/- 4.1 and 9.5 +/- 4.9 J, respectively), but peak voltages were higher for the experimental waveform than for the standard waveform (411 +/- 80 and 325 +/- 81 V, respectively). For the experimental waveform the DFT w as 10 J or less using an endocardial lead-alone system in 10 (67%) of 15 patients and in 12 (80%) of 15 patients using an endocardial-subcutaneous array lead system.

CONCLUSIONS

A shorter duration waveform delivered by smaller capacitors does not increase defibrillation energy requirements and might reduce device size. However, the smaller capacitance reduces the maximum energy output. If a 10-J safety margin between DFT and maximum energy output of the ICD is required, only a subgroup of patients will benefit from 90-microF ICDs with DFTs feasible using current defibrillation lead systems.

The signal-averaged ECG: time-domain analysis

During the past decade, the high-resolution electrocardiogram as a non-invasive technique for the detection of ventricular late potentials has developed from an experimental method into a routinely applied non-invasive method for risk stratification of patients after myocardial infarction. Meanwhile, several approaches have been developed for the detection of ventricular late potentials including time-domain analysis, frequency-domain analysis and spectrotemporal mapping. Clinical applications are no longer limited to patients after myocardial infarction, but cover a wider spectrum of different cardiac diseases. This review focuses on some methodological aspects as well as on the results and current clinical applications of the analysis of the signal-averaged ECG in the time domain.

[Reproducibility of the signal-averaged, high-pass filtered electrocardiogram]

In order to test the reproducibility of the signal-averaged electrocardiogram (SAECG) using Simson's method (high-pass filter cutoff frequency 25 Hz, orthogonal leads, recording of 133 s per lead), 121 patients were examined. In all patients, two signal-averaged ECGs were performed on the first day of the study immediately after each other, using identical electrode position. In a subgroup of 47 patients, the same procedure was repeated 3 days later. There was no difference between the mean values of conventionally calculated averaging parameters (heart rate, QRS-duration, root-mean-square voltage in the terminal 40 ms of the highly amplified and filtered QRS-complex [V40], the low amplitude signal duration under 40 microV in the terminal portion of the QRS-complex [LAS], total root-mean-square voltage of the QRS-complex), both with regard to immediate and short-term reproducibility. Thus, conventionally calculated averaging parameters are well reproducible.