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Biomedical subjects

W Jung

Publications and source records attributed to W Jung.

At least 73 records · Page 4Linked to original sources
PubMed1999

Inward and outward rectifying potassium currents set membrane potentials in activated rat microglia.

Activation of cultured rat microglial cells with lipopolysaccharide (LPS), induced outward rectifying K+ (K(V)) current in addition to already existing inward rectifying K+ current (K(IR)). By measuring zero-current membrane-potentials using whole-cell patch-clamp method, we showed that K(V) current plays a direct role in setting membrane potential to near -45 mV. Since the membrane potentials of microglia show two prominent peaks at -45 and -70 mV, we hypothesize that K(IR) current might set the membrane potential to near -70 mV. We observed that cells with larger K(IR) current had a zero-current membrane-potential at around -70 mV, and that blocking of K(IR) current with Ba2+ depolarized membrane potentials to near -45 mV. These results indicate that the amounts of K(IR), and K(V) current determine the zero-current membrane-potentials in LPS-activated microglia.

Animals↗
PubMed1999

Radiofrequency ablation of atrial flutter due to administration of class IC antiarrhythmic drugs for atrial fibrillation.

In selected patients, atrial fibrillation (AF) converts to atrial flutter (AFI) due to treatment with class IC antiarrhythmic drugs. In this study, we prospectively investigated the effects of AFI ablation and continuation of drug therapy in patients with AF who developed AFI due to long-term administration of class IC antiarrhythmic drugs. The study population consisted of 187 patients from an AF registry with paroxysmal AF who were orally treated with flecainide (n = 96) or propafenone (n = 91). Twenty-four patients (12.8%) developed AFI during the course of treatment. In 20 of these patients (10.7%), electrophysiologic study revealed typical AFI. These patients underwent radiofrequency ablation of AFI. Ablation failed in 1 patient. All patients continued preexisting drug treatment. Recurrence of AF was assessed by ambulatory Holter monitoring and serial questionnaires. During a mean follow-up of 11 +/- 4 months, the incidence of AF episodes was significantly lower in patients with a combined therapy (2.7 +/- 3.6 per year) than in control subjects with a sole drug treatment (7.8 +/- 9.2 per year, p <0.05) and than before therapy (10.2 +/- 5.4 per year, p <0.001). Subgroup analysis revealed that 7 patients (36.8%) remained symptom free with no evidence of atrial tachyarrhythmia. Eight additional patients (42.1%) had ongoing paroxysmal AF, however, with a significantly lower incidence of AF episodes than before therapy (2.3 +/- 1.6 per year vs 11.5 +/- 5.0 per year, p <0.001). In the remaining 4 patients (14.7%), no beneficial effect of AFI ablation was found. It is concluded that in patients with AF who develop typical AFI due to administration of class IC antiarrhythmic agents, a combined therapy with catheter ablation of AFI and continuation of drug treatment is highly effective in reducing occurrence and duration of atrial tachyarrhythmias.

Administration, Oral↗
PubMed1999

Characterization of an alkali-extracted peptidoglycan from Korean Ganoderma lucidum.

The biologically active peptidoglycan was purified from the alkali fraction of the fruiting bodies of Ganoderma lucidum and the composition of the peptidoglycan was investigated by conventional analyses. The alkali-extracted peptidoglycan showed differences in chemical compositions from the water-extracted. The alkali-extracted peptidoglycan contained 6.9% protein and 75.9% carbohydrates composed mainly of beta-glucose, mannose, and alpha-glucose. The molecular weight range of the peptidoglycan was determined as 2,000 kDa-17 kDa. The peptidoglycan is considered to be a hybrid molecule of polysaccharide chains covalently bound as a side chain to the polypeptide core.

Amino Acids↗
PubMed1999

[Clinical experience with the implantable atrial defibrillator (atrioverter) in patients with atrial fibrillation. Metrix Investigators].

Due to the limited efficacy of drug therapy in atrial fibrillation and the high rate of recurrence, strong efforts were made to find non-pharmacological strategies. For three years now, the implantable atrial defibrillator Metrix from InControl has been available as an alternative therapy. From October 1995 to the present the atrial defibrillator was implanted in 179 patients worldwide. The sensitivity of the system and its algorithms to detect atrial fibrillation is 90%; the specificity to detect sinus rhythm is 100%. In 121 of 179 patients, 748 episodes of spontaneous atrial fibrillation were treated with 2.4 shocks per episode. No proarrhythmic event or stroke was seen. A cardioversion to sinus rhythm could be achieved in 95% of patients; the overall clinical success rate was 88%. In 7% of all patients, early recurrence of atrial fibrillation (ERAF) occurred that could not be converted into stable sinus rhythm after further cardioversions and antiarrhythmic therapy. In 4.1% there were lead-related complications, in 4 patients the device had to be explanted because of ineffective therapy, and in 3 patients the device had to be changed because of loss of telemetry or early depletion of battery. In 8 patients, postoperative complications were seen (infections, pneumothorax and thrombosis of the subclavian vein). Overall, the implantable atrial defibrillator Metrix is an effective and safe alternative in treating atrial fibrillation.

Adult↗
PubMed1999

Transverse conduction capabilities of the crista terminalis in patients with atrial flutter and atrial fibrillation.

OBJECTIVES: In this study, the transverse conduction capabilities of the crista terminalis (CT) were determined during pacing in sinus rhythm in patients with atrial flutter and atrial fibrillation. BACKGROUND: It has been demonstrated that the CT is a barrier to transverse conduction during typical atrial flutter. Mapping studies in animal models provide evidence that this is functional. The influence of transverse conduction capabilities of the CT on the development of atrial flutter remains unclear. METHODS: The CT was identified by intracardiac echocardiography. The atrial activation at the CT was determined during programmed stimulation with one extrastimulus at five pacing sites anteriorly to the CT in 10 patients with atrial flutter and 10 patients with atrial fibrillation before and after intravenous administration of 2 mg/kg disopyramide. Subsequently, atrial arrhythmias were reinduced. RESULTS: At baseline, pacing with longer coupling intervals resulted in a transverse pulse propagation across the CT. During shorter coupling intervals, split electrograms and a marked alteration of the activation sequence of its second component were found, indicating a functional conduction block. In patients with atrial flutter, the longest coupling interval that resulted in a complete transverse conduction block at the CT was significantly longer than that in patients with atrial fibrillation (285 +/- 49 ms vs. 221 +/- 28 ms; p < 0.05). After disopyramide administration, a transverse conduction block occurred at longer coupling intervals as compared with baseline (287 +/- 68 ms vs. 250 +/- 52 ms; p < 0.05). Subsequently, a sustained atrial arrhythmia was inducible in 15 of 20 patients. This was atrial flutter in three patients with previously documented atrial fibrillation and in eight patients with history of atrial flutter. Mapping revealed a conduction block at the CT in all of these patients. CONCLUSIONS: It was found that the CT provides transverse conduction capabilities and that the conduction block during atrial flutter is functional. Limited transverse conduction capabilities of the CT seem to contribute to the development of atrial flutter.

Aged↗
PubMed1999

Inappropriate implantable defibrillator discharge caused by a retained pacemaker lead fragment.

INTRODUCTION: Inappropriate discharge is still a major issue of implantable cardioverter defibrillator therapy. The diagnostic options of modern devices facilitate classification of the underlying abnormality. METHODS AND RESULTS: A 65-year-old woman with depressed left ventricular performance received spurious shocks from an ICD, implanted for ventricular tachycardia. A lead fragment of an explanted VVI pacemaker system could be identified as cause of erroneous ventricular fibrillation detection by the ICD. The electrical noise caused by interaction between the lead remnant and the ICD lead was detectable even on the surface ECG. CONCLUSION: Based on our findings, removal of fragmented lead material should be considered prior to ICD implantation, to avoid potentially adverse and harmful interactions with ICD systems.

Aged↗
PubMed1999

Intra-atrial defibrillation in humans.

The frequency of atrial fibrillation (AF) and its economic impact on the health-care system ensure that AF will be a focus for future research. At present, the chronic use of an atrioverter (IAD) is a major challenge in the nonpharmacological treatment of AF. Studies in animals as well as in humans have demonstrated the feasibility and safety of internal atrial defibrillation. The major issues that have to be addressed are the pain perception and the potential risk of inducing life-threatening ventricular arrhythmias during delivery of low-energy atrial shocks. A first step to this novel approach is a physician activated device. At the very beginning, the IAD should be restricted to highly selected patients with drug refractory, poorly tolerated, recurrent AF episodes. The extenuation of this therapy to wider subsets of patients should be dependent on the initial results with regard to clinical efficacy and safety as well as patient tolerance. Finally, cost-effectiveness as well as quality of life studies are needed to demonstrate the benefit of this specific therapy among other therapeutic strategies available for the management of AF. A new arrhythmia management system that combines both detection and treatment in the atrium as well as in the ventricle may represent an important milestone and a significant improvement in the management of patients with both supraventricular and ventricular tachyarrhythmias.

Atrial Fibrillation↗
PubMed1999

Temperature response following nontraumatic low power radiofrequency application.

A marker for the efficiency of heating would be helpful in radiofrequency ablation of tachyarrhythmias. We hypothesized that changes of the catheter tip temperature during nontraumatic, very low power radiofrequency exposure would correlate with the temperature achieved during radiofrequency ablation, and therefore, could be used as a marker for heating efficiency. In 71 ablation attempts for drug refractory supraventricular tachycardias, the catheter tip temperature response to a 1-W-5-second test pulse was measured. Subsequently at the same site, radiofrequency current was delivered with a target temperature of 70 degrees C and a power limit of 50 W. The test pulse, with a measured power level of 1.62 +/- 0.28 W, resulted in a heating efficiency of 0.78 +/- 0.60 degree C/W. During ablation, the achieved tip temperature was 52.9 +/- 7.5 degrees C, requiring a power output of 40.7 +/- 10.9 W. The heating efficiency was 0.57 +/- 0.74 degree C/W. The correlation between heating efficiency at low power and during radiofrequency ablation was linear with a correlation coefficient of 0.88. Regression analysis demonstrated that a heating efficiency above 1 degree C/W predicts a mean ablation temperature above 50 degrees C with more than 95% confidence interval. The temperature response to a very low power radiofrequency application correlates with the temperature rise achieved during radiofrequency ablation. It is suggested that delivery of low power radiofrequency current could be used to determine and monitor efficiency of heating during catheter mapping and ablation procedures.

Catheter Ablation↗
PubMed1999

Oxygen uptake to work rate relation throughout peak exercise in normal subjects: relevance for rate adaptive pacemaker programming.

The oxygen uptake to work rate (VO2/WR) relationship observed throughout peak exercise testing is already being applied for rate adaptive pacemaker programming. However, the detailed curve design of VO2/WR with respect to the anaerobic threshold (AT) has not yet been investigated. It was the purpose of this study to determine the VO2/WR slope below and above the AT in a healthy control group. Seventy-eight healthy control subjects (45.9 +/- 17.4 years; 34 women: 49.9 +/- 18.6 years 44 men: 43.6 +/- 16.6 years) were exercised on a treadmill with "breath-by-breath" gas exchange monitoring using the symptom limited "ramping incremental treadmill exercise" (RITE) protocol. The slope of the VO2/WR relationship from rest to peak exercise (r-p), rest to AT (slope A), and AT to peak exercise (slope B) in mL oxygen uptake per watt of external treadmill work was determined by linear regression analysis. [table: see text] The oxygen uptake to work rate relationship throughout peak exercise in the entire study group generated a significant slope change at the AT (31%, P < 0.0001) with a decreasing slope during higher work load intensities. Female subjects demonstrated a greater percentage of slope change at AT (43%), as compared to men (22%, P < 0.01). When using the oxygen uptake to work rate relationship for the programming of the pacemaker's rate response to exercise, the significant slope change at the AT should be considered to more appropriately pace during higher work intensities supported by anaerobic metabolism. Female pacemaker patients should be programmed to generate a steeper VO2/WR slope below AT with a greater slope change at AT, as compared to men. Abnormally high oxygen uptake to work rate ratios above the AT may be possibly used as an indicator of overpacing.

Adult↗
PubMed1999

Percutaneous extraction of an abandoned coiled pacing lead.

Abandoning redundant pacing leads has been an accepted practice in most cases. Late migration of a lead is a rare, unpredictable, and potentially lethal complication of this approach and requires immediate removal. We report the case of an atrial pacing lead that had migrated and was found coiled in the right atrium. It was removed by a snare catheter via a femoral approach.

Aged↗
PubMed1999

Verification of linear lesions using a noncontact multielectrode array catheter versus conventional contact mapping techniques.

INTRODUCTION: Creation of linear lesions is an established ablation goal. Verification of complete conduction block at the ablation line is required to determine ablation success. Conventional mapping techniques are sequential endocardial activation mapping and documentation of double potentials. Recently, a noncontact multielectrode array catheter was developed that allows instantaneous three-dimensional mapping by simultaneous reconstruction of > 3,000 electrograms. In this study, we prospectively compared the accuracy of noncontact mapping to identify discontinuities in linear lesions and to verify a conduction block with that of conventional mapping techniques. METHODS AND RESULTS: In 12 patients with atrial flutter, radiofrequency pulses were applied between the tricuspid annulus and either the inferior vena cava or the eustachian ridge. Following each application, pulse propagation at the ablation line was determined during pacing by conventional mapping techniques. The findings were compared to high-density isopotential mapping using the noncontact multielectrode array catheter. It was found that noncontact mapping reliably distinguished conduction delays from a conduction block as defined by contact mapping. In addition, noncontact mapping instantaneously identified the area where a discontinuity in the line of block was present. In these patients, complete conduction block was achieved by radiofrequency pulses guided by the noncontact mapping system. CONCLUSION: Noncontact mapping is highly accurate in distinguishing conduction delays from a complete conduction block. By providing an instantaneous high-density propagation vector at all sites along the ablation line, three-dimensional isopotential mapping is helpful in localizing discontinuities of linear lesions and, thus, may facilitate the creation of a complete conduction block.

Adult↗
PubMed1999

Radiofrequency catheter ablation of frequent monomorphic ventricular ectopic activity.

INTRODUCTION: Frequent ventricular ectopic beats can result in severe symptoms and may even be incapacitating in some patients. Although radiofrequency catheter ablation is an effective and safe therapy for drug refractory idiopathic ventricular tachycardia, it has not been widely used in ventricular ectopy. The purpose of this study was: (1) to assess the potential role of catheter ablation in eliminating monomorphic ventricular ectopy in symptomatic patients regarding feasibility and safety and (2) to determine the usefulness of various mapping strategies. METHODS AND RESULTS: Forty-one patients with symptomatic ventricular ectopic activity (right ventricular origin in 23 patients, left ventricular origin in 18 patients) were enrolled. The mean frequency of ventricular ectopic beats was 1512+/-583/hour documented by Holter ECG monitoring. These patients had previously been unable to tolerate or had been unsuccessfully treated with a mean of 3+/-1 antiarrhythmic agents. The site of origin was mapped using earliest endocardial activation times, unipolar electrograms and pace mapping. Radiofrequency ablation was successful in 34 (83 %) of 41 patients. Multivariate logistic regression analysis revealed pace mapping as the only independent predictor for a successful ablation site (P < 0.01). After a follow-up of 3 months, the overall success rate was 71%. The mean frequency of ventricular ectopic beats after successful ablation was 12+/-10 ventricular premature beat/hour. CONCLUSION: Radiofrequency catheter ablation is an effective and safe treatment for frequent symptomatic drug refractory monomorphic ventricular ectopic activity. Pace mapping predicts best successful ablation of ventricular ectopic beats.

Adolescent↗
PubMed1999

Imaging of thrombi and assessment of left atrial appendage function: a prospective study comparing transthoracic and transoesophageal echocardiography.

OBJECTIVE: To compare the value of current transthoracic echocardiographic systems and transoesophageal echocardiography for assessing left atrial appendage function and imaging thrombi. DESIGN: Single blind prospective study. Patients were first investigated by transthoracic echocardiography and thereafter by a second investigator using transoesophageal echocardiography. The feasibility of imaging the left atrial appendage, recording its velocities, and identifying thrombi within the appendage were determined by both methods. PATIENTS: 117 consecutive patients with a stroke or transient neurological deficit. SETTING: Tertiary cardiac and neurological care centre. RESULTS: Imaging of the complete appendage was feasible in 75% of the patients by transthoracic echocardiography and in 95% by transoesophageal echocardiography. Both methods were concordant for the detection of thrombi in 10 cases. Transoesophageal echocardiography revealed two additional thrombi. In one of these patients, transthoracic echocardiography was not feasible and in the other the thrombus had been missed by transthoracic examination. In patients with adequate transthoracic echogenicity, the specificity and sensitivity of detecting left atrial appendage thrombi were 100% and 91%, respectively. Recording of left atrial appendage velocities by transthoracic echocardiography was feasible in 69% of cases. None of the patients with a velocity > 0.3 m/s had left atrial appendage thrombi. In the one patient in whom transthoracic echocardiographic evaluation missed a left atrial appendage thrombus, the peak emptying velocity of the left atrial appendage was 0.25 m/s. CONCLUSIONS: A new generation echocardiographic system allows for the transthoracic detection of left atrial appendage thrombi and accurate determination of left atrial appendage function in most patients with a neurological deficit.

Adult↗
PubMed1998

Atrioverter: an implantable device for the treatment of atrial fibrillation.

BACKGROUND: During atrial fibrillation, electrophysiological changes occur in atrial tissue that favor the maintenance of the arrhythmia and facilitate recurrence after conversion to sinus rhythm. An implantable defibrillator connected to right atrial and coronary sinus defibrillation leads allows prompt restoration of sinus rhythm by a low-energy shock. The safety and efficacy of this system, called the Atrioverter, were evaluated in a prospective, multicenter study. METHODS AND RESULTS: The study included 51 patients with recurrent atrial fibrillation who had not responded to antiarrhythmic drugs, were in New York Heart Association Heart failure class I or II, and were at low risk for ventricular arrhythmias. The atrial defibrillation threshold had to be </=240 V during preimplant testing. Atrial fibrillation detection, R-wave shock synchronization, and defibrillation threshold were tested at implantation and during follow-up. Shock termination of spontaneous episodes of atrial fibrillation was performed under physician observation. Results are given after a minimum of 3 months of follow-up. During a follow-up of 72 to 613 days (mean, 259+/-138 days), 96% of 227 spontaneous episodes of atrial fibrillation in 41 patients were successfully converted to sinus rhythm by the Atrioverter. In 27% of episodes, several shocks were required because of early recurrence of atrial fibrillation. Shocks did not induce ventricular arrhythmias. Most patients received antiarrhythmic medication during follow-up. In 4 patients, the Atrioverter was removed: in 1 because of infection, in 1 because of cardiac tamponade, and in 1 because of frequent episodes of atrial fibrillation requiring His bundle ablation. CONCLUSIONS: With the Atrioverter, prompt and safe restoration of sinus rhythm is possible in patients with recurrent atrial fibrillation.

Adult↗