Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Ventricular Oversensing: (2003)
    350 Main Street , Malden , MA 02148-5018 , U.S.A . : Blackwell Futura Publishing, Inc.
    Pacing and clinical electrophysiology 26 (2003), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: WERETKA, S., et al. : Ventricular Oversensing: A Study of 101 Patients Implanted with Dual Chamber Defibrillators and Two Different Lead Systems. Modern dual chamber ICD systems are able to overcome various sensing problems. However, improvement of their performance is still required. The aim of this study was to assess the sensing function in 101 consecutive patients (84 men, 17 women; mean age 63 ± 12 years; mean follow-up 24 ± 4 months) implanted with dual chamber defibrillators and integrated (IB) or dedicated bipolar (DB) lead systems. Follow-up data were analyzed for the presence of ventricular oversensing. Oversensing occurred in 25 (25%) patients, significantly more frequent in patients implanted with IB compared to DB lead systems (21/52 vs 4/49, P = 0.0002). Patients with cardiomyopathies (CMs) were more prone to sensing malfunctions than patients with no CM (12/30 vs 13/71, P = 0.04). T wave oversensing (n = 14), respirophasic ventricular oversensing (n = 4), and P wave oversensing (n = 6) were the most common pitfalls of ventricular sensing. P wave oversensing was unique to the IB lead system. CT scans performed in these patients disclosed the position of the RV coil to be proximal to the tricuspid area. Four patients received inappropriate ICD shocks due to oversensing. In all but two patients who received lead revision, oversensing was resolved by noninvasive means. In conclusion: (1) ventricular oversensing is a common problem occurring in up to 25% of patients with dual chamber ICDs; (2) P wave oversensing is a ventricular sensing problem affecting function of 11% of dual chamber devices with IB lead systems; (3) IB leads are significantly more susceptible to T wave and P wave oversensing than DB leads; and (4) patients with cardiomyopathies are more prone to oversensing than patients with other heart diseases. (PACE 2003; 26[Pt. I]:65–70)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2003.00152.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Far-Field R Wave Oversensing in a Dual Chamber Arrhythmia Management Device: Predisposing Factors and Practical Implications (2001)
    Oxford, UK : Blackwell Futura Publishing, Inc.
    Pacing and clinical electrophysiology 24 (2001), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: WERETKA, S., et al.: Far-Field R Wave Oversensing in a Dual Chamber Arrhythmia Management Device: Predisposing Factors and Practical Implications. Initial experience with the Medtronic Jewel 7250, the ICD designed to detect and treat ventricular and supraventricular tachyarrhythmias, is very promising. Its effectiveness, however, depends on sensing performance, which has not yet been systematically examined. The aim of the study was to determine the incidence of, predisposing factors for, and practical implications of far-field R wave oversensing (FFRWOS) in this dual chamber ICD. During a total follow-up of 797 months in 48 patients who had the Jewel 7250, follow-up strip charts, 12-channel Holter recordings and, in particular cases, Holter recordings with intracardiac markers were analyzed for the presence of FFRWOS. FFRWOS was documented in ten (21.3%) patients. Compared to other lead locations, the right atrial appendage lead position was most frequently associated with FFRWOS (7/27 vs 3/21, P 〈 0.05). Patients with FFRWOS had significantly more treated and nontreated atrial episodes, many of which were judged to have been detected inappropriately. In one case, inappropriate atrial antitachycardia pacing due to R wave oversensing triggered sustained ventricular tachycardia, terminated eventually with a high energy shock. In dual chamber ICDs, FFRWOS may represent a frequent phenomenon possibly leading to serious consequences. For atrial leads, a lateral atrial wall position seems to be preferable. In most cases, FFRWOS can be eliminated by optimization of atrial sensing parameters. Given the possibility of ventricular proarrhythmia with atrial pacing therapy, the capability of ventricular backup defibrillation in respective devices is at least reassuring.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2001.01240.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Variability of Holter Electrocardiographic Findings in Patients Fulfilling the Noninvasive MADIT Criteria (2002)
    Oxford, UK : Blackwell Futura Publishing, Inc.
    Pacing and clinical electrophysiology 25 (2002), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: SENGES, J.C., et al.: Variability of Holter Electrocardiographic Findings in Patients Fulfilling the Noninvasive MADIT Criteria. In the MADIT study, a selected group of postinfarction patients with asymptomatic nonsustained ventricular tachycardia (NSVT) has been shown to benefit from prophylactic ICD treatment. The present study analyzed the variability of NSVT in a patient population fulfilling the noninvasive MADIT criteria. Three consecutive Holter ECGs were performed in weekly intervals in 68 postinfarction patients with an LVEF ≤ 0.35. Patients with NSVT underwent programmed ventricular stimulation (PVS); patients were implanted with an ICD if sustained VT or VF was inducible. If NSVT was found in at least two recordings, the arrhythmia was defined as reproducible. In 28 (41%) of the 68 patients, NSVT was found in at least one recording. Seventeen patients revealed NSVT in the first, the remaining 11 in the second registration; no patient had NSVT only in the third Holter. Of the patients with NSVT, 50% had only one, 39% had two, and 11% had three positive recordings. Thus, reproducible NSVT was found in only 50% of the patients with NSVT. Predictors for reproducibility were LVEF 〉 0.27, NYHA Class I, absence of digitalis therapy, and 〉 2 NSVT per 24-hour period. Reproducible NSVT was not associated with risk factors such as elevated mean heart rate, reduced heart rate variability, late potentials, or inducibility of sustained VT during PVS. During 17 ± 9 months of follow-up, seven (10%) patients experienced arrhythmic events: two without and five with previously documented NSVT. In the latter patients, first occurrence of NSVT was consistently in the first Holter; only two of them had reproducible NSVT. In postinfarction patients, the risk factor NSVT exhibits marked spontaneous variability, especially in those with a low number of NSVT per 24-hour period, LVEF 〈 0.27 or NYHA III, which limits its clinical value as a selection criterion for PVS. Reproducibility of NSVT itself does not seem to be an independent risk factor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2002.00183.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Rate and Time Dependent Effects of D-Sotalol on the Monophasic Action Potential After Sudden Increase of the Heart Rate (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 22 (1999), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Experimental and clinical data suggests that almost all Class III antiarrhythmic agents diminish their ability to prolong cardiac repolarization at fast heart rates. However, only limited data exists about the time course of efficacy decay of Class III agents after sudden increase of the heart rate. In the present study, we assessed both rate and time dependent changes of the efficacy of d-sotalol in higher stimulation frequencies following an abrupt increase in heart rate. This might imitate the situation seen in the development of paroxysmal tachycardias. Monophasic action potentials were recorded from the right ventricular apex during sinus rhythm and constant stimulation with the paced cycle length (PCL) of 550 ms, 400 ms, and 330 ms in the baseline and 20 minutes after intravenous administration of d-sotalol (2.5 mg/kg) in seven patients with documented life-threatening ventricular tachyarrhythmias. D-sotalol significantly prolonged monophasic action potential duration at different steady-state heart rates (sinus rhythm: 21.1%± 3.6%; PCL 550 ms: 16.6%± 4.3%, 400 ms: 11.2%± 2.7%, 330 ms: 5.8%± 2.1%). The prolongation is significantly shorter in higher steady-state pacing, confirming a pronounced reverse-use dependent decrease of the efficacy of d-sotalol at faster stimulation frequencies. After the abrupt increase in heart rate, the beat-to-beat adaptation of the postdrug action potential prolongation exhibits only slight reverse-use dependent shortening. The decrease of the efficacy of d-sotalol is insignificant for the first 20 consecutive beats at the stimulation frequency of the PCL of 400 msec (from 16.6% at PCL of 550 ms to 14.6% at the 20th beat of the PCL of 400 ms), and for the first ten consecutive beats at the stimulation frequency of the PCL of 330 ms (from 16.8% at PCL of 550 ms to 12.3% at the 10th beat of the PCL of 330 ms). This slow decay of action potential prolongation after an abrupt increase in heart rate might contribute to the antiarrhythmic action of d-sotalol in cardiac tachyarrhythmias.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1999.tb00301.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Ventricular Arrhythmias in Dilated Cardiomyopathy (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 20 (1997), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Although prognosis of dilated cardiomyopathy (DCM) has improved due to advances in diagnosis and therapy, still too many sudden cardiac deaths occur in DCM. Spontaneous ventricular ectopy is a very common finding in patients with DCM, but the prognostic significance of Holter monitoring remains controversial. Other noninvasive methods, e.g., late potentials and QT dispersion, have not yet contributed to the evaluation of prognosis for arrhythmogenic events in DCM. Programmed ventricular stimulation has been repeatedly used to stratify long-term prognosis, yet satisfactory data are still missing as many deaths occur in patients without inducible arrhythmias. Several prognostic studies are still in progess, and preliminary data for the use of ICDs already appear to be promising. In patients with poor left ventricular function and ICDs in situ, prognosis is determined by progression of heart failure. Heart transplantation may be the ultimate therapeutic instrument for end-stage heart failure patients. For patients with advanced DCM and increased risk for malignant arrhythmias who are unsuitable for orthotopic heart transplantation, the combined therapy with an ICD and dynamic cardiomyoplasty may be an alternative treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1997.tb06121.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Inefficient ventilation and reduced respiratory muscle capacity in congestive heart failure (2000)
    Springer
    Basic research in cardiology 95 (2000), S. 333-342 
    Details
    ISSN: 1435-1803
    Keywords: Key words Chronic heart failure – lung function – respiratory muscles – exercise – outcome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The extent and time-course of changes in lung volumes, ventilatory efficiency at rest and during exercise, and respiratory muscle function and their influence on exercise limitation in congestive heart failure (CHF) are unclear. It is unknown whether respiratory muscle function may predict changes in exercise limitation or may be impaired in patients with poor outcome. 145 male patients (54±1 years) suffering from CHF (NYHA class I–III, mean 2.3±0.1), with a LVEF of 23±1 %, and a mean peak O2 uptake (VO2peak) 15.0±:0.5 mL×min−1×kg−1, were studied. They were grouped in Weber functional classes A to D according to their VO2peak. Significant increases in ventilatory equivalents for O2 and CO2 (VE/VCO2peak) and in dead space ventilation at rest and during exercise were found with increasing exercise limitation. Moreover, there was a correlation of static and dynamic lung volumes (inspiratory vital capacity, IVC, r = 0.43, P 〈 0.01), as well as of maximal inspiratory pressure (MIP; r = 0.46, P 〈 0.01) with VO2peak. Patients who died (n = 26) or were heart transplanted (n = 20) during a follow-up (mean 800 ± 10 days) had a reduced MIP (6.4 ± 0.4 kPa) as compared with survivors (n = 82; 9.3±0.7 kPa, P 〈 0.01). In a subgroup of 33 patients re-evaluated after six months, individual changes in IVC and VE/VCO2peak, but not in MIP, correlated to changes in VO2peak (r = 0.69 and r = 0.72 respectively; P 〈 0.01). In CHF, exercise limitation is associated with reversible lung restriction and inefficient ventilation at rest and during exercise. Patientss with severe CHF have a significant reduction in MIP, a finding that is associated with poor outcome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003950070053
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Influence of intercellular junctions on endothelin secretion of human umbilical vein endothelial cells in vitro (2000)
    Springer
    Basic research in cardiology 95 (2000), S. 299-307 
    Details
    ISSN: 1435-1803
    Keywords: Key words Endothelial junctions – calcium – endothelin – cadherins – von Willebrand factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The endothelium plays a pivotal role in the theological regulation of blood flow by the secretion of vasoactive factors. The interaction between shear forces and the endothelium is determined by the mechanical properties of the endothelial cell layer which are associated with intercellular junctions. Cell-cell contacts could therefore modulate the secretion of vasocative factors in response to theological stimuli. We investigated the relationship between intercellular junctions and the secretion of the vasoconstrictor peptide endothelin and the coagulation co-factor von Willebrand factor (vWF). Human umbilical vein endothelial cells (HUVECs) were used as in vitro endothelial model system. Intercellular junctions were reversibly disrupted by calcium chelation or hypertonic stress; alternatively, the formation of intercellular junctions was inhibited by culturing the cells in suspension or by plating them in the presence of an inhibitory anti-VE-cadherin antibody. The opening of intercellular junctions was verified by assessing transmonolayer electrical resistance (TMR) and immunofluorescence morphology. The concentration of endothelin and vWF was measured in the cell culture supernatants using specific ELISAs. The secretion of endothelin was inhibited by EGTA (5 mM) and stimulated by incubation with tumor necrosis factor α (TNFα, 40 ng/ml). Treatment with hypertonic medium (glycerol, 1200 mosmol/l) for 10 minutes opened intercellular junctions and markedly reduced the secretion of endothelin. HUVECs in suspension culture did not secrete endothelin and failed to respond to TNFα, but readily resumed these functions upon forming a new monolayer on plastic. The reconstitution of intercellular junctions after suspension culture could be inhibited using a specific anti-VE-cadherin antibody. This antibody, but not a non-specific anti-humanIgG antibody reduced endothelin secretion. The secretion of von Willebrand Factor was less dependent on intercellular junctions. The opening of intercellular junctions did not induce cell death, since the cells continued to exclude trypan blue. The results of this study suggest a novel and potentially pathophysiologically/clinically relevant correlation between intercellular junctions and the secretion of endothelin in endothelial cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003950070049
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Electrophysiologic effects of the new IKs-blocking agent chromanol 293b in the postinfarction canine heart (2000)
    Springer
    Basic research in cardiology 95 (2000), S. 324-332 
    Details
    ISSN: 1435-1803
    Keywords: Key words Antiarrhythmic agents – myocardial infarction – heart – mapping – M cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objectives. Aim of the present study was to investigate site- and rate dependent effects of the IKs-blocking agent chromanol 293b on conduction and refractoriness in normal, infarcted, and transitional regions of in-situ canine hearts. Methods. In five dogs with subacute myocardial infarction, three-dimensional mapping was performed after insertion of 6 × 6 needle electrodes in the left ventricle. Before and after application of chromanol 293b (10 mg/kg), activation patterns and local refractory periods (ERPs) at pacing intervals of 300, 500 and 850 ms were obtained for the surviving epicardial muscle layer of the infarct zone (IZ) and for epi-, endo-, and midmyocardial muscle layers of both the normal zone (NZ) and the border zone (BZ) separating normal and infarcted areas. Results. At baseline, both the NZ and the BZ exhibited uniform ERPs throughout the ventricular wall. Epicardial ERPs were longer in the IZ than in the NZ, and intermediate in the BZ. Chromanol 293b did not affect total activation times. However, at fast heart rates regional areas of slow conduction occurred. Chromanol 293b ubiquitously prolonged local ERPs, most markedly in the IZ. A preferential effect on individual muscle layers of the NZ or BZ and, thus, drug-induced transmural dispersion of ERP could not be observed. Again ubiquitously, the effect on ERP was more pronounced at faster than at slower heart rates, that is, positive use-dependent. At a basic cycle length of 300 ms, chromanol 293b prolonged local ERPs in the IZ by 46 ± 24 %, in the BZ by 34 ± 26 %, and in the NZ by 20 ± 17 %( p ≤ 0.05). Conclusions. At least in theory, the electrophysiologic properties of chromanol 293 b, that is, preferential prolongation of refractoriness in ischemic myocardium, more pronounced at faster than at slower heart rates, but homogeneously throughout in intact ventricular wall, appear to be favorable. Whether this translates into a clinical benefit, particularly in the treatment of ischemia-related ventriular tachyarrhythmias, remains to be determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003950070052
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Catechol-O-methyl transferase in human erythrocytes (1972)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 272 (1972), S. 265-276 
    Details
    ISSN: 1432-1912
    Keywords: Erythrocytes ; Catechol-O-Methyl Transferase (COMT) ; Catccholamines ; Isoproterenol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Washed human red cells, suspended in an isotonic electrolyte solution, were incubated with radioactive catecholamines (epinephrine, norepinephrine, dopamine and isoproterenol). Their conversion to 3-O-methyl derivatives was demonstrated by ion exchange chromatography for each substrate. There was no O-methylation if the erythrocytes were boiled or hemolyzed prior to incubation or if the catechol-O-methyl transferase (COMT) inhibitor pyrogallol was added to the incubation medium. Only catecholamines were methylated by this system, as could be demonstrated by using the non-catecholamine orciprenaline as substrate. Experiments with l-methionine-(methyl-14C) showed that the methylation was brought about by the transfer of a methyl group from l-methionine to the 3-hydroxy group of epinephrine. Thus, this enzymatic system had the properties of COMT. Our experiments therefore suggest that COMT is present in human erythrocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00499038
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Opioid receptor agonists activate pertussis toxin-sensitive G proteins and inhibit adenylyl cyclase in canine cardiac sarcolemma (1996)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 354 (1996), S. 643-649 
    Details
    ISSN: 1432-1912
    Keywords: Cardiac sarcolemma ; Opioid receptors ; Adenylyl cyclase ; Low Km ; GTPase ; G proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Although both opioid receptors and endogenous opioids are abundant in cardiac tissues, the signal transduction pathways of opioids in cardiac sarcolemmal membranes have yet to be identified. In highly purified canine cardiac sarcolemmal membranes, binding of the opioid receptor antagonist [3H]diprenorphine and effects of μ, δ and κ agonists on low Km GTPase and adenylyl cyclase were measured. Equilibrium binding of [3H]diprenorphine revealed a maximal binding capacity of 7.2 pmol/mg protein and a Kd of 1.3 nmol/1. In the presence of GTP, (D-Pen2,5, p-Cl-Phe4)enkephalin and (D-Arg6)dynorphin A 1-13 fragment both inhibited adenylyl cyclase by 20–25% (from 206 ± 30to164 ± 28 pmol·min− 1·mgprotein−1, EC506 μmol/Landfrom254 ± 109to204 ± 90 pmol·min− 1·mg protein−, EC50 8 pmol/L, respectively; P〈0.001). Both substances stimulated low Km GTPase by 20%and13%,respectively(from12.7 ± 3.0 to 15.2 ± 3.7 pmol·min−1.mgprotein−1,EC50 12 μmol/L, P〈0.01, and from 9.1 ± 2.8 to 10.4 ± 3.2 pmol-min− 1·mg protein−1, EC50 6 μmol/L, P〈0.05, respectively). These effects were blocked by the opioid receptor antagonist naltrexone and by pretreatment of sarcolemmal membranes with pertussis toxin. The μ opioid receptor agonists (D-AIa2, Me Phe4, Gly-[ol]5)enkephalin and morphiceptin had no effect on either cardiac adenylyl cyclase or low Km GTPase activities. These data suggest that in cardiac sarcolemma, opioid receptors are coupled to pertussis toxin sensitive G proteins and mediate inhibition of adenylyl cyclase activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00170840
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...