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  • 1
    Electronic Resource
    Electronic Resource
    The Potential Usage of Dual Chamber Pacing in Patients with Implantable Cardioverter Defibrillators (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: Bradycardia support by ICDs has been limited to fixed rate, ventricular pacing. Concomitant placement of a pacemaker and an ICD exposes a patient to potentially life-threatening device interactions. ICDs capable of dual chamber pacing have recently become available. The number of ICD recipients who stand to benefit from the addition of dual chamber pacing is debated, but no data have addressed this question. This retrospective study analyzed all patients who received nonthoractomy ICD system placement at the Mayo Clinic in Rochester, MN between March 1991 and October 1996 in order to determine the proportion of patients in whom a dual chamber pacing ICD may be indicated. Definitions: (1) Definitely indicated = pacemaker present at ICD implant or NASPE Class I pacing indication; (2) Probably indicated = NASPE Class II pacing indication, NYHA Functional Class III or IV, or history of systolic congestive heart failure; (3) Possibly indicated = history of paroxysmal atrial fibrillation or an ejection fraction ≤ 20%. The results were that nonthoracotomy ICDs were placed in 253 patients. A dual chamber ICD would have been definitely indicated in 11% of the study group, probably indicated in 28%, and possibly indicated in 14%. Chronic atrial fibrillation was present at ICD implant in 6.7% of patients and developed in 0.9%/yr during follow-up. The addition of dual chamber pacing to ICDs stands to potentially benefit approximately half (53%) of ICD recipients. These data do not address all patients who may benefit from dual chamber sensing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1999.tb00303.x
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  • 2
    Electronic Resource
    Electronic Resource
    Importance of Pacemaker Noise Reversion as a Potential Mechanism of Pacemaker-ICD Interactions (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 21 (1998), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Numerous types of interactions between pacemakers and implantable cardioverter defibrillators (ICDs) have been described. Pacemaker outputs preventing appropriate detection of ventricular tachycardia or ventricular fibrillation by the ICD is one of the more serious. Asynchronous pacemaker activity during ventricular arrhythmias maybe caused by either nonsensing of the arrhythmia or by noise reversion, which is an algorithm that causes the pacemaker to switch to asynchronous pacing when repetitive sensing at a high rate occurs. We analyzed the mechanisms underlying asynchronous pacemaker activity in ventricular arrhythmias using pacemaker telemetry during the arrhythmia. Thirty-nine induced arrhythmias from 26 different procedures in 19 patients with both pacemakers and ICDs were analyzed. Of the 39 arrhythmias, asynchronous pacemaker activity occurred in 16. The underlying mechanism was nonsensing in 4 episodes and noise reversion in 12 episodes. Clinically significant interference with detection arose on three occasions. Conditions favoring the occurrence of noise reversion include specific pacemaker models, arrhythmia cycle lengths in the range causing noise reversion of the individual pacemaker model, long noise sampling periods, and VVI pacing mode. Noise reversion can be diagnosed by telemetering the pacemaker marker channel during ventricular arrhvthmias as a part of routine pacemaker-ICD interaction evaluation. It can be prevented or minimized by programming short ventricular refractory periods or using pacemakers with shoii retriggerable refractory periods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1998.tb00158.x
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  • 3
    Electronic Resource
    Electronic Resource
    Permanent Pacing in Ebstein's Anomaly (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: Patients with Ebstein's anomaly present unique challenges to permanent pacing due to anatomical variations and tricuspid valve replacement. We retrospectively reviewed our experience with permanent pacing in patients with Ebstein's anomaly between 1976 and 1993. We identified 401 patients with Ebstein's anomaly, of whom 15 (3.7%) required permanent pacing (1 of the 15 was implanted elsewhere). Of the 15, there were 8 females and 7 males (mean age 32 years [range 7-74]); the indications for pacing were AV block in 11 and sinus node dysfunction in 4. Eight patients were programmed with WI and seven with DDD. All VVI patients were paced epicardially. Two patients with DDD pacemakers had transvenous atrial and ventricular leads, 4 DDD patients had transvenous atrial leads and epicardial ventricular leads, and 1 patient had both epicardial and transvenous systems. Associated surgical procedures included tricuspid valve replacement in 14 of 15, atrial septal defect repair in 10 of 15, atrioplasty in 7 of 15, prior tricuspid annuloplasty in 4 of 15, pulmonary vein dilation in 1 of 15, and conduction system ablation in 2 of 15. Patients had a mean follow-up of 35 months (range 1-168 months). Complications requiring operative intervention occurred in four patients. One patient had displacement of a transvenous ventricular lead. A second patient had an epicardial lead failure. A third patient had a nonfunctioning atrial lead that displaced across the tricuspid valve, causing severe tricuspid regurgitation. The fourth patient had multiple epicardial and endocardial leads exit block with secondary diaphragmatic stimulation. Permanent pacemakers were required in 3.7% of patients with Ebstein's anomaly, with the indication being intrinsic conduction disease in the majority of patients. Ninety-three percent of patients required tricuspid valve replacement, suggesting more severe manifestation of Ebstein's anomaly. Twenty-seven percent had complications requiring surgical intervention. Thus, permanent pacing in patients with Ebstein's anomaly can be challenging and should be approached by an experienced physician. (PACE 1997;20[Pt. I]:1243-1246)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1997.tb06776.x
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  • 4
    Electronic Resource
    Electronic Resource
    Advance Program (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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1997.tb05513.x
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  • 5
    Electronic Resource
    Electronic Resource
    Permanent Pacing in Patients with Univentricular Heart (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: Patients with one of several varieties of malformation designated as “univentricular hearts” may be especially challenging when permanent pacing is required. Our objective was to review our experience in this subset of patients that had undergone permanent pacing and thus determine the optimal approach. A retrospective chart review was done of 32 patients with some variety of “univentricular” malformation who had required permanent pacing at our institution. Although technically challenging, permanent pacing in this group of patients can be successful through several approaches. The various approaches, as well as consideration of the differences that exist between patients undergoing septation and those undergoing a Fontan procedure are discussed. Although long-term permanent pacing is possible in this group of patients, before pacing begins, a thorough understanding of the anatomy and prior surgical procedures is necessary. Use of a combined atrial transvenous and ventricular epicardial pacing system may work well for some patients. With the development of newer and more reliable coronary sinus leads, dual chamber transvenous pacing with ventricular stimulation via the coronary sinus could become the approach of choice in some patients with “univentricular hearts.”
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1999.tb00600.x
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  • 6
    Electronic Resource
    Electronic Resource
    Clinical Surveillance of a Tined, Bipolar, J-Shaped, Steroid-Eluting, Silicone-Insulated Atrial Pacing Lead (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: Since 1990, 558 Medtronic 5524 bipolar, silicone-insulated, J-shaped, tined, steroid-eluting atrial leads have been implanted at the Mayo Clinic (Rochester, MN, USA) and the Midelfort Clinic (Eau Claire, WI, USA). Implantation data were favorable, with pacing thresholds at implantation (median threshold, 0.6 V) better than most published data on other atrial leads. The rate of acute lead-related complications (dislodgment and diaphragmatic pacing) necessitating reoperation or electrical abandonment of the atrial lead was 0.9%. This rate is lower than that in most published series of atrial leads. Over a median follow-up time of 17.5 months (up to 69 months), there were no chronic lead-related complications and no definite or suspected failures of lead material. This rate is much lower than that with other atrial leads studied previously. We conclude that the Medtronic 5524 atrial lead combines the reliability of silicone insulation with a lack of chronic complications and high thresholds due to its steroid elution and with stability in the atrium due to its J shape despite a passive fixation mechanism. There is no evidence of lead material failure during up to 6 years of follow-up.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1999.tb00573.x
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  • 7
    Electronic Resource
    Electronic Resource
    Clinical Surveillance of a Tined, Bipolar, Steroid-Eluting, Silicone-Insulated Ventricular Pacing Lead (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: Since 1990, 1,068 Medtronic 5024 bipolar, silicone-insulated, tined, steroid-eluting ventricular leads have been implanted at the Mayo Clinic (Rochester, MN) and Midelfort Clinic (Eau Claire, WI). Implantation data were favorable: median pacing thresholds of 0.5 V at 0.5 ms, median R wave of 13.4 mV, and median impedance of 593 Ω. Of the 2.1% acute lead-related complications (dislodgment, microdislocation, diaphragmatic pacing, and undersensing), 1.2% necessitated reoperation. This rate is lower than that in most published series of other leads. During a median follow-up of 23 months (up to 76 months), 12 (1.1 %) chronic lead-related complications (high thresholds, loss of capture, and undersensing) and no instances of definite or suspected lead material failure occurred. This rate is much lower than that in studies of other leads. Thus, the 5024 lead combines the reliability of silicone insulation with a low rate of chronic complications that is probably the result of its steroid elution. No evidence of failure of lead material has appeared up to 6 years after implantation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1999.tb00541.x
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  • 8
    Electronic Resource
    Electronic Resource
    Newer Clinical Applications of Pacing (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 8 (1997), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Newer Clinical Applications of Pacing. For many years, the indications for permanent cardiac pacing consisted primarily of AV block and sinus node dysfunction. In recent years, the indications for pacing have expanded considerably. This article details recent advances in the application of permanent pacing and the use of permanent pacing for patients with hypertrophic cardiomyopathy, dilated cardiomyopathy, prevention of atrial fibrillation, and pacing in the long QT syndrome. Pacing is now an accepted therapeutic modality in hypertrophic cardiomyopathy and has rapidly gained acceptance in the United States, although there are still many unknowns about selection of patients and long-term benefits. Even less is known about pacing for dilated cardiomyopathy. Certain patients do respond with definite subjective improvement and improved quality of life, although there are no data to date to suggest improved longevity. Pacing for long QT syndrome is now a well-accepted indication for this relatively small subset of patients. Pacing for the prevention of atrial fibrillation is still in the very early stages of development. Multiple methods have been tried with the current method of choice being dual site atrial pacing. However, it is too early to predict the long-term success of this modality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1997.tb01006.x
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  • 9
    Electronic Resource
    Electronic Resource
    Regulation of macrophage production of vascular endothelial growth factor (VEGF) by hypoxia and transforming growth factor β-1 (1998)
    Springer
    Annals of surgical oncology 5 (1998), S. 271-278 
    Details
    ISSN: 1534-4681
    Keywords: Vascular endothelial growth factor ; Human macrophage ; Hypoxia ; Breast cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Breast tumors contain high numbers of infiltrating macrophages. The role and function of these cells within the tumor remain unclear, but a number of studies have found an association between poor prognosis and macrophage content in human breast cancer. Both hypoxia and TGFβ-1 have been shown to regulate VEGF in other cell types. We hypothesized that breast tumor-associated macrophages produce VEGF and that macrophage production of this factor is regulated by both hypoxia and TGFβ-1. Methods: Paraffin-embedded breast tumor sections were stained immunohistochemically with anti-VEGF, anti-CD68, and anti-cytokeratin. Monocytes were matured for 3 days in 20% autologous plasma and activated with 1000 U/mL interferon-γ for 24 hours. Supernatants were assayed for VEGF protein by ELISA. Total RNA was isolated from cells and reverse transcribed to cDNA, which was used as a template in PCR reactions for VEGF and β-actin. Results: Both tumor cells and tumor macrophages produce VEGF in human breast tumors. Hypoxia increases VEGF protein and mRNA levels in monocyte-derived macrophages, whereas TGFβ-1 increases VEGF protein but not mRNA under hypoxic growth conditions. Conclusions: Breast tumor-associated macrophages may contribute to the angiogenic activity of human breast tumors by producing VEGF. Macrophage production of VEGF is upregulated by hypoxia and TGFβ-1, both of which occur in the tumor environment. Macrophage production of VEGF is regulated at both the mRNA and protein levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02303785
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  • 10
    Electronic Resource
    Electronic Resource
    TGFβ-1 regulation of VEGF production by breast cancer cells (1997)
    Springer
    Annals of surgical oncology 4 (1997), S. 621-627 
    Details
    ISSN: 1534-4681
    Keywords: Vascular endothelial growth factor ; Transforming growth factor β-1 ; Breast cancer ; Angiogenesis ; Metastasis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Angiogenesis is essential for tumor growth and metastasis. Vascular endothelial growth factor (VEGF) is the most potent angiogenic factor identified to date. TGFβ-1 acts as an indirect angiogenic agent. Methods: VEGF and TGFβ-1 were measured in the serum of breast cancer patients and agematched controls and in tumor tissue of cancer patients by ELISA. VEGF protein and mRNA expression by breast tumor cell lines were examined, and the effect of TGFβ-1 on VEGF production in these cells was assessed. Results: VEGF levels were significantly higher (P=.03) in the serum of patients with breast cancer compared to age-matched controls. A positive correlation was found between serum (r=0.539) and tumor tissue (r=0.688) levels of VEGF and TGFβ-1. Metastatic MDA-MB-231 breast cancer cells produce more VEGF than do the primary BT474 cells. TGFβ-1 significantly (P〈.05) increased production of VEGF. Conclusions: Breast cancer cells constitutively produce VEGF protein and mRNA. There is a relationship between VEGF and TGFβ-1 levels in breast cancer patients, and TGFβ-1 regulates VEGF expression by breast cancer cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02303745
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