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Biomedical subjects

B Lüderitz

Publications and source records attributed to B Lüderitz.

At least 109 records · Page 6Linked to original sources
PubMed1999

Role of smooth muscle cell death in advanced coronary primary lesions: implications for plaque instability.

OBJECTIVE: Instability of coronary atheroma leads to the onset of acute coronary syndromes including myocardial infarction and death, as well as to the progression of the arteriosclerotic disease. As yet, the underlying factors and mechanisms causing plaque rupture are not completely understood. Since a low content of smooth muscle cells (SMCs) apparently plays a key role, the question points to the events leading to the loss of intimal SMCs. METHODS: We compared coronary atherectomy specimens from 25 patients with unstable angina to those from 25 patients with stable angina. Transmission electron microscopy was used to identify intimal cell population, to detect stage and cell type of apoptosis, and to differentiate between apoptosis and necrosis. RESULTS: Plaques associated with unstable angina contained more macrophages/lymphocytes and significantly less SMCs (P = 0.01), compared with stable angina plaques. Specific cell death forms, apoptosis and necrosis, were present in all coronary atheroma. As key findings, both the proportion of SMCs undergoing apoptosis and the frequency of cytoplasmic remnants of apoptotic SMCs (matrix vesicles) were significantly increased in unstable versus stable angina lesions (P = 0.002 and P = 0.002). In addition, cellular necrosis was more frequent in the first coronary atheroma group (P = 0.02). Positive correlations were found between the frequency of apoptotic cells and necrosis (r = 0.41, P = 0.04), and that of matrix vesicles and necrosis (r = 0.63, P = 0.001) only in plaques with unstable angina, but not in those with stable angina. CONCLUSIONS: Our data demonstrate that high cell death due to apoptosis and necrosis is a basic in situ feature found in advanced coronary primary lesions associated with unstable angina, possibly explaining their low density of (viable) SMCs. Thus, antagonization of intimal cell death should be considered in order to stabilize the intimal plaque texture of coronary atheroma with the ultimate goal to prevent plaque rupture.

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

Atrial natriuretic peptide levels and pulmonary artery pressure awake, at exercise and asleep in obstructive sleep apnoea syndrome.

Elevated nocturnal plasma atrial natriuretic peptide (ANP) levels were found in patients with obstructive sleep apnoea (OSA). The purpose of our study was to examine the secretion of ANP during the night and to measure changes in oxygen saturation, pulmonary artery pressure and intrathoracic pressure swings in patients with OSA. Moreover, we analysed the secretion of ANP and the pulmonary artery pressure in different behavioural states, e.g. awake, at exercise and asleep. Consecutive apnoeas in non-rapid eye movement (NREM) sleep at the beginning, middle and end of the sleep study were analysed in six patients with obstructive sleep apnoea. In addition, we measured the plasma levels of ANP. The apnoea duration was significantly longer (P< 0.05) at the middle of the sleep study than at the beginning or end. Correspondingly, the end-apnoeic oxygen saturation and end-apnoeic oesophageal pressure were both significantly lower (P< 0.05) in the middle of the sleep study than at the beginning or end. No significant differences were found in the end-apnoeic systolic transmural pulmonary artery pressure (P(PATM)) and the levels of ANP. Evaluation of the ANP levels during different behavioural states revealed that the asleep levels were slightly, but not significantly, higher than the awake levels (0.235+/-0.088 vs. 0.207+/-0.057 nmol/L). However, the highest levels were found during exercise (0.334+/-0.170 nmol/L) with a significant difference compared with the awake and asleep levels. These data suggest that volume effects may be a potent factor in liberating ANP during exercise, but the role of OSA in ANP secretion when asleep is questionable.

Atrial Natriuretic Factor↗
PubMed1999

[Independent radiologic prognostic factors for fatal outcome of ambulatory-acquired pneumonia requiring inpatient treatment].

PURPOSE: To evaluate the independent prognostic impact of the chest radiograph for mortality from community-acquired pneumonia requiring hospitalization. METHODS: Chest radiographs of 67 patients with hospital-treated community-acquired pneumonia were analyzed with regard to the prognostic implications of radiographic patterns, extent and density of infiltrates, and its evolution during treatment. RESULTS: Non-survivors had a significantly higher extent of infiltrates (p = 0.008), density of infiltrates (p = 0.05), and radiographic spread during follow-up within 48-75 hours (p = 0.0001). In multivariate analysis, persistent or progressive infiltrates were associated with a 47-fold increase, and persistent or progressive density of infiltrates with an 18-fold increase in risk of mortality. The presence of both parameters could correctly predict 96% of survivors and 90% of non-survivors. CONCLUSIONS: The chest radiograph is an independent predictor of the severity of pneumonia. Both persistent or progressive infiltrates and persistent or progressive density of infiltrates are independently associated with mortality from community-acquired pneumonia.

Adolescent↗
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↗
PubMed1999

Obstructive sleep apnea as a risk marker in coronary artery disease.

STUDY OBJECTIVES: Obstructive sleep apnea (OSA) is associated with a range of cardiovascular sequelae and increased cardiovascular mortality. The aim of our study was to assess the prevalence of OSA in patients with symptomatic angina and angiographically verified coronary artery disease (CAD). In addition, we analyzed the association of OSA and other coronary risk factors with CAD and myocardial infarction. METHODS: Overnight non-laboratory-monitoring-system recordings for detection of OSA was performed in 223 male patients with angiographically verified CAD and in 66 male patients with exclusion of CAD. A logistic regression analysis was performed to assess associations between risk factors and CAD and myocardial infarction. RESULTS: CAD patients were found to have OSA in 30.5%, whereas OSA was found in control subjects in 19.7%. The mean apnea/hypopnea index (AHI) was significantly higher (p < 0.01) in CAD patients (9.9 +/- 11.8) than in control subjects (6.7 +/- 7.3). Body-mass-index (BMI) was significantly higher in patients with CAD and OSA than in patients with CAD without OSA (28. 1 vs. 26.7 kg/m(2); p < 0.001). No significant difference was found with regard to other risk factors and left ventricular ejection fraction (LVEF) between both groups. Hyperlipidemia (OR 2.3; CI 1. 3-3.9; p < 0.005) and OSA defined as AHI >/=20 (OR 2.0; CI 1.0-3.8, p < 0.05) were independently associated with myocardial infarction. CONCLUSIONS: There is a high prevalence of OSA among patients with angiographically proven CAD. OSA of moderate severity (AHI >/=20) is independently associated with myocardial infarction. Thus, in the care of patients with CAD, particular vigilance for OSA is important.

Adult↗
PubMed1999

Myocardial uptake of technetium-99m-furifosmin (Q12) versus technetium-99m-sestamibi (MIBI).

AIM: This study was performed to compare the myocardial uptake of Tc-99m-furifosmin (Q12) versus Tc-99m-sestamibi (MIBI) in correlation to the whole-body uptake under resting conditions. METHODS: 21 patients with coronary artery disease and no rest ischemia were examined. A whole-body scan was performed 60 min. p.i. under resting conditions. A quantification of the uptake (whole-body, heart and right lung) was done by ROI technique. RESULTS: The heart-to-lung ratio of Q12 (1.56 +/- 0.191) was significantly lower as compared to MIBI (1.94 +/- 0.197; p < 0.01). In contrast, the heart-to-whole-body ratios (Q12 versus MIBI: 0.027 +/- 0.012 versus 0.026 +/- 0.004; p < 0.76) did not differ. The lung-to-whole-body ratio (Q12 versus MIBI: 0.018 +/- 0.009 versus 0.013 +/- 0.002; p < 0.17) were different, but did not reach significance. CONCLUSION: These data show that under resting conditions the total myocardial uptake of Q12 does not differ significantly from that of MIBI. However, the pulmonary uptake of Q12 is slightly higher, resulting in a significant lower heart-to-lung ratio. These findings imply a lower image quality of Q12 compared to MIBI.

Adult↗