Inadequate Erythropoietin Response to Anaemia in HIV Patients: Relationship to Serum Levels of Tumour Necrosis Factor-Alpha, Interleukin-6 and Their Soluble receptors

Severe anaemia is a frequent complication in advanced HIV infection. In our study we investigated the interaction between cytokine network, HIV infection and erythropoietin (Epo) response with increasing anaemia levels. No correlations could be established between circulating tumour necrosis factor (TNF)-alpha and any of the examined parameters. However, a negative correlation was found between haemoglobin values and soluble TNF receptor levels (sTNF-R-I: r  = −0.54; P  < 0.001; sTNF-R II: r  = −0.47; P  < 0.001) as well as interleukin-6 levels ( r  = −0.29; P  < 0.001). In contrast, no significant increase in log[Epo], counterbalancing haemoglobin decline and paralleling the rise in sTNF receptors, was found. In patients classified as stage III, according to the Centers for Disease Control (CDC) classification, the erythropoietin response was significantly more impaired than in patients from CDC groups I and II ( P  < 0.001). The results of this study suggest that similar to its action in vitro , activation of the TNF/TNF-R system may impair erythropoietin production in HIV-associated anaemia. Due to the brief half-life of TNF-α, this activation is particularly reflected by elevations of soluble TNF receptor levels.     

Management of Patients After Catheter Ablation of Ventricular Tachycardia

The management of patients after catheter ablation of ventricular tachycardia is not well defined. In this article we summarize recently published results and report our own experience. Factors influencing the clinical outcome of these patients and methods to identify patients with an increased risk of recurrence of ventricular tachycardia are discussed. Furthermore, a review is given on current concomitant therapeutic tools including antiarrhythmic drugs and the implantation of an automatic cardioverter defibrillator.     

Doppler echocardiographic analysis of cardiac flow during the Mueller manoeuver

The inspiration against a closed airway, the Mueller manoeuver, leads to a negative intrathoracic pressure. It is controversially discussed whether this is causing an augmentation of right heart murmurs. There is only limited knowledge on the temporal relationship of the negative intrathoracic pressure with right and left ventricular filling and stroke volume. To investigate this relationship, the flow through the mitral, aortic, tricuspid and pulmonary valves was studied continuously by Doppler echocardiography during a standardized Mueller manoeuver in 15 healthy subjects (age 45 +/- 10 years). Five heart beats after the initiation of the manoeuver, flow through the mitral and aortic valve decreased 12.2 +/- 7.2% (P less than 0.001) and 10.1 +/- 6.6% (P less than 0.001), respectively. A transient increase of 15.1 +/- 9.2% (P less than 0.001) in tricuspid flow was followed by a 14.3 +/- 9.8% (P less than 0.005) increase of flow through the pulmonary artery. Ten heart beats after the initiation of the Mueller manoeuver, flow through the pulmonary artery again reached baseline, while tricuspid flow remained below baseline values. In contrast to previous studies, our results indicate that the Mueller manoeuver causes a small and transient increase in right ventricular stroke volume which is unlikely to cause a marked augmentation in right heart murmurs.     

EFFICIENCY OF THE LEFT VENTRICLE ASSIST DEVICE HEMOPUMP IN CARDIAC FIBRILLATION

We have examined in sheep the efficiency of the Hemopump duringventricular fibrillation. Circulatory arrest was induced byelectrical stimulation and maintained for 30 min. Haemodynamicmeasurements were recorded continuously and blood samples weretaken before, during and after fibrillation to determine totalbody and myocardial metabolic activity. All hearts were defibrillatedsuccessfully after 30 min of fibrillation. During fibrillation,the Hemopump sustained a mean arterial pressure of about 60mm Hg with a blood flow rate of about 2.3 litre min^–1.These perfusion conditions were sufficient for maintenance ofaerobic myocardial metabolism, but with a borderline circulatorysupply to the total organism.     

Examination of Explanted Polyurethane Pacemaker Leads Using the Scanning Electron Microscope

Since 1978, 2,365 polyurethane (PU) insulated cardiac pacing leads were implanted transvenously at our institution. To date, there have been no insulation failures in those leads. Thirty-seven PU leads were explanted, mainly for exit block, and 28 of these were investigated using the scanning electron microscope. We found a homogeneous distribution of surface changes in all lead segments in 56% of the 28 examined. These changes were more pronounced at the ligature site; severe surface cracking was noticed in 21%, with the deepest crack being 40 micron (average range of 10-15 micron). There appeared to be no time-dependency of the surface changes as indicated by regression analysis (r = 0.32, p greater than 0.05). The ultimate severity and outcome of this degradation process in the leads reported in this study will only be known in the future after longer use. We conclude that excess stress must be avoided during the implantation procedure and that careful surveillance is necessary.     

Three-Year Clinical Experience with a New Endocardial Screw-In Lead with Introduction Protection for Use in the Atrium and Ventricle

There is still a high incidence of dislodgement, threshold rises, and loss of sensing with permanent transvenous endocardial leads. Atrial leads are an even greater problem and require particularly reliable methods of fixation. In March, 1976 we reported our preliminary results from animal experiments using a new transvenous screw-in lead with introduction protection. This lead differs from other screw-in models as its spiral tip is retracted in the insulating tube during insertion. For fixation purposes a torque is applied to the proximal end of the conductor coil, which is loosely positioned within the tube, and this moves the helical electrode forward. One hundred and fifty endocardial electrodes have been implanted; 127 of them in the dilated ventricle and 23 in the atrium. The technique of introducing the lead into the vein (cephalic or jugular) was the same as that for conventional leads. It was easy to manage and quite uncomplicated. The fixation features in the atrium or the ventricle were sufficiently reliable to allow some patients to go home several hours post-implant. The total working time of the leads used has been 900 months; the overall complication rate is 2%.     

Ventilation and dyspnoea during exercise in patients with heart failure

Patients with chronic heart failure have an increased ventilation/carbondioxide production ratio (VE/Vco₂) during exercise. Recentlyit was discussed whether the cause of this increase was a ventilatorystimulus driven other than by CO₂ Dyspnoea during exercise isthought to be related to impaired respiratory function. However,clinical confirmation is scarce. Ninety-two patients (age 51± 9 years) with heart failure due to idiopathic dilatedcardiomyopathy exercised on a bicycle ergometer to exhaustion,and measurement of ventilatory gases and Swan-Ganz catheterizationwere performed. The maximal oxygen consumption corrected forbody weight (Vo₂max kg^–1) was 16·6 ± 5·5ml x min^–1 x kg^–1 The increase in (VE/Vco₂ duringexercise was related to an increase in respiratory rate (r=0·43;P<0·00001) but not to an increase in cardiac indexor capillary wedge pressure. Nineteen patients stopped exercisingbecause of dyspnoea. Their maximal tidal volume and Vo₂max kg^–1were lower than the 67 patients who stopped exercise becauseof fatigue (P<0·001 and P<0·00001 respectively).Other variables showed no significant difference. In conclusion, the increase in VE/Vco₂ during exercise may reflecta non-CO₂ driven ventilatory stimulus as it cannot be attributedto increased pulmonary vascular pressures or an insufficientincrease in cardiac output leading to a ventilation-perfusionmismatch. Low oxygen uptake is a prominent finding in patientswith chronic heart failure who experienced dyspnoea during exercise,and dyspnoea is in part related to impaired respiratory function.     

Polyurethane Leads: Facts and Controversy

Une comparaison des électrodes de stimulation en polyuréthane et en silicone est présentée. Lorsue ľon compare tes qualités mécaniques et électriques, les qualités de friction et la stabilité hydrolytique, les deux matériaux paraissent capables ďêtre utilisés comme game des sondes ďélectrode. Néanmoins, en raison des craquelures de surface observé'es avecle polyuréthane il est nécessaire ďobtenir des surfaces aussi précises et parfaites que possible. De plus, les manoeuvres de torsion et de courbure doivent être évitées lors de ľimplantation. Enfin, la surveillance à long terme doit être assurée ďune façon routiniere.
A comparison of polyurethane and silicone cardiac pacing leads is presented. In comparing mechanical and electrical properties, friction coefficient and hydrolytic stability, both are highly qualified for use as electrode sheaths. The occurrence of surface cracking of polyurethane leads is examined. Several suggestions are proposed for dealing with the manufacture of new leads, the technique of implantation, and the follow-up required for successful surveillance.