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Biomedical subjects

C Weinhold

Publications and source records attributed to C Weinhold.

At least 19 recordsLinked to original sources
PubMed1997

Influence of anodal electrode position on transvenous defibrillation efficacy in humans: a prospective randomized comparison.

Nonthoracotomy lead systems for implantable cardioverter defibrillators (ICDs) have reduced operative mortality and morbidity as compared to epicardial lead systems but are usually associated with higher defibrillation thresholds (DFTs). The purpose of this prospective randomized trial was to investigate if the second defibrillation electrode in the left subclavian vein can increase defibrillation efficacy and decrease DFT as compared to the superior vena cava (SVC) position in nonthoracotomy lead systems for ICDs. Seventeen patients (mean age: 49.9 +/- 11.3 years, mean ejection fraction: 46.1% +/- 15.8%) were implanted with an investigational unipolar electrode (Medtronic 13001) used as the defibrillation anode. DFT testing was started in the SVC (n = 10, group A) or the left subclavian vein (n = 7, group B), and repeated in the alternative position starting at the DFT of the initial position. Fifteen patients were eligible for analysis (group A: n = 9, group B: n = 6). With the electrode in the SVC, ventricular fibrillation could be successfully terminated in 9 out of 15 patients (60%). In the left subclavian vein the success rate was 100% (P < 0.01). Mean DFT in the SVC was 13.0 +/- 5.2 J and in the left subclavian vein 10.2 +/- 4.9 J. DFTs in the left subclavian vein were either lower (group A: n = 5/9, group B: n = 5/6) or equal to the results in the SVC position (P < 0.001). Thus, the left subclavian vein appears to be a superior alternative for positioning of the defibrillation anode as compared to the SVC for nonthoracotomy lead systems using two separate leads.

Defibrillators, Implantable↗
PubMed1996

An imbalance in T-helper cell subsets alters immune response after cardiac surgery.

Growing evidence indicates that cell-mediated immunity is altered after cardiac surgery with cardiopulmonary bypass (CPB). The objective of this prospective randomized study was to investigate (1) if an imbalance in T-helper cell (TH) subsets, i.e. TH1/TH2, may be responsible for these alterations and (2) if they can be counteracted. Twenty patients formed control group A. Twenty group B patients received indomethacin and thymopentin for immunomodulation. In vitro tests included measurements of TH, interleukin (IL)-2 as a cytokine primarily produced by TH1 cells, and IL-6 as a cytokine primarily produced by TH2. Delayed-type hypersensitivity (DTH) skin response and specific antibody (AB) production were used as in vivo tests for TH1- and TH2-induced immune response, respectively. Postoperatively, group A patients showed a persistent, significant reduction of TH, IL-2 synthesis and DTH skin response as compared to baseline values, while IL-6 synthesis remained unaltered and AB production increased (P < 0.05). In group B patients no change in TH, IL-2 and IL-6 synthesis, or DTH skin response was observed (P < 0.05 vs A). Postoperative AB production increased significantly in group B. These results indicate a significant suppression of TH1-induced cell-mediated immune response following CPB, while TH2-induced response remains normal. A normal TH2 response may be helpful for recovery following cardiac surgery by cleaning the body of the byproducts of CPB. A suppression of TH1 response may gain clinical significance whenever a postoperative infection requires this response, but can be effectively counteracted by immunomodulatory intervention with indomethacin and thymopentin.

Aged↗
PubMed1995

Comparison of porcine biological valves with pericardial valves--a 12-year clinical experience with 1123 bio-prostheses.

In order to evaluate selective differences of biological porcine valves versus pericardial valves and to analyze various valve models, 8 different bioprostheses (4 porcine valves, 4 pericardial valves) were studied in a 12-year follow-up. From 1978 to 1990, 476 porcine bioprostheses (Carpentier-Edwards: n = 104, Carpentier Edwards Supraanular: n = 59, Hancock I: n = 41, Hancock II: n = 272) and 647 pericardial valves (Hancock-Extracorporeal: n = 479, Ionescu-Shiley: n = 76, Carpentier-Edwards: n = 57, Mitroflow: n = 35) were implanted. At time of implantation, the patient age ranged from 21-85 years, mean 57.1 +/- 12.4 years. 831 patients were analyzed in the long-term follow-up (62.3 +/- 18.6 months, cumulative follow-up of 6632 patient-years). The incidences of thromboembolic complications (TE), endocarditis (E), primary tissue failure (PTF), rate of reoperation (ReOp), and late mortality due to prosthesis dysfunction were analyzed, calculated, and compared within the different valve models (actuarial data, chi 2 test, log rank analysis). The incidences of TE and E were lower for pericardial valves when compared with porcine bioprostheses (TE: 0.88 vs. 1.8%/patient year; E: 0.24 vs. 0.5%/patient year); within the 2 groups, the different valve models did not show any major differences. However, the incidence of PTF was significantly higher in the pericardial valve group, being 36 +/- 6.5%, 68 +/- 10% and 86 +/- 19.5% after 6, 8, and 10 years; the respective figures for the porcine valves were 6 +/- 3.5%, 18 +/- 7.1%, and 60 +/- 13.1% (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

The left subclavian vein as an alternative site for implantation of the second defibrillation lead.

The optimal placement for the second defibrillation lead in a two-lead system has never been addressed. We retrospectively reviewed the data of 33 patients with an average age of 59.2 years (range 41-78 years), predominantly male (n = 29), who underwent implantation of a cardioverter defibrillator (ICD) for treatment of ventricular tachycardia (n = 19) or ventricular fibrillation (n = 14). In all patients an attempt was made to implant an endovenous ICD device (leads only, no subcutaneous patch). In group I (n = 18) the defibrillation anode, a separate unipolar lead, was placed in the common position, the superior vena cava. In group II (n = 15) the lead was placed in the left subclavian vein. At least two consecutive shocks reverting ventricular fibrillation at energies < or = 24 J were required for implantation of the ICD device. All shocks were monophasic. The success rate of endovenous defibrillation was significantly higher in group II than in group I (67% vs 28%, P < 0.05). Thus, it could be demonstrated that the position of the defibrillation anode can influence the defibrillation efficacy in transvenous ICD systems. Prospective randomized trials are needed to investigate the optimal position for the second defibrillation electrode, which may gain increasing importance as soon as dual chamber ICDs become available.

Adult↗
PubMed1995

Determinants of dual chamber pulse generators longevity.

The aim of this study was to investigate the effect of battery capacity, internal current drain, and stimulation energy on pulse generators longevity, and if battery impedance measurements can reliably predict pulse generators end-of-life. For this purpose, the records of 577 patients with a mean age of 65 +/- 14 years who had undergone implantation of two different dual chamber pulse generators (PG1: 409; PG2: 168) were retrospectively reviewed. Battery capacity were 2.3 Ah (PG1) and 3.0 Ah (PG2) while current drain at comparable nominal settings was 20 microA (PG1) and 30 microA (PG2) indicating a higher internal current drain of PG2. After a mean follow-up of 46 +/- 23 months, stimulation energy at reprogrammed output settings was significantly higher in PG1 as compared to PG2 (17.1 +/- 0.14) vs 15.5 +/- 0.24 J). Three PG1 (0.7%) and 12 PG2 (7.1%) (P < 0.01) had to be exchanged after a mean of 77.3 +/- 5.3 months (PG1) and 75 +/- 13.5 months (PG2) (P = NS) due to end-of-life being reached. The difference in battery impedances of PG1 and PG2 gained statistical significance 5 years after implantation (1.0 k omega vs 2.4 +/- 6.7 k omega) preceding the significant difference in PG survival after 6 years (98.7 +/- 1.3% vs 90.7 +/- 4.8%). These results indicate that internal current drain is the most important determinant of the pulse generators longevity and that battery impedance can reliably predict end-of-life. Therefore, the essential information about internal current drain should be available for each pacemaker, since it is required for adequate pulse generator selection. Diagnostic functions of dual chamber pulse generators should include measurements of battery impedance.

Adult↗
PubMed1994

One-incision approach for insertion of implantable cardioverter defibrillators.

The placement of a transvenous implantable cardioverter defibrillator (ICD) system through a single infraclavicular skin incision has been a surgical goal for years. The development of a new investigational model of ICD with substantially reduced dimensions (volume, 83 cm3; mass, 132 g) has made the one-incision approach a clinical reality. Between March and September 1993, 4 female and 19 male patients (mean age, 60 +/- 9.6 years; range, 46 to 73 years) underwent implantation of this device for the treatment of ventricular fibrillation (n = 14) or ventricular tachycardia (n = 9). One transvenous lead was placed in the right ventricular apex and another in the left subclavian vein. A subpectoral pocket was formed in the infraclavicular area from the same incision to house the ICD generator and, if necessary, the subcutaneous patch. The mean operation time (81.5 +/- 32.7 minutes; range, 54 to 195 minutes) was significantly shorter than that noted for a previous series made up of patients undergoing traditional transvenous ICD implantations. In 20 patients (87%), endovenous defibrillation without a subcutaneous patch successfully caused externally induced ventricular fibrillation to revert with a mean minimum energy output of 21.9 +/- 3.5 J (range, 12 to 24 J). Endovenous defibrillation was more successful when biphasic (n = 16/17 [94%]) shocks rather than monophasic shocks (n = 4/6 [67%]) were used. No mortality, morbidity, or surgical complications were observed. These results indicate that the one-incision approach and the small size of the ICD generator can substantially facilitate ICD implantation and result in a reduction in the surgical trauma, the operation time, and the amount of material implanted.

Aged↗
PubMed1994

Studies of the nucleoside transporter inhibitor, draflazine, in the human myocardium.

1. The aim of the present study was to determine the effect of the nucleoside transporter inhibitor, draflazine, on the force of contraction in human myocardium and the affinity of the compound for the nucleoside transporter. Nucleoside transport inhibitors, like draflazine, are of potential importance for cardiopreservation of donor hearts for heart transplantation. 2. Functional experiments were performed in isolated electrically driven (1 Hz, 1.8 mmol l-1 Ca2+) human atrial trabeculae and ventricular papillary muscle strips. The affinity of draflazine for the myocardial nucleoside transporter was studied in isolated membranes from human ventricular myocardium and human erythrocytes in radioligand binding experiments using [3H]-nitrobenzylthioinosine ([3H]-NBTI). Dipyridamole was studied for comparison. 3. In membranes from human myocardium and erythrocytes, [3H]-NTBI labelled 1.18 pmol mg-1 protein and 23.0 pmol mg-1 protein, respectively, nucleoside transporter molecules with a KD value of 0.8 nmol l-1. Draflazine concentration-dependently inhibited binding of [3H]-NBTI to myocardial and erythrocyte membranes with a K(i)-value of 4.5 nmol l-1. The potency as judged from the K(i) values was ten times greater than that of dipyridamole in both myocardial and erythrocyte membranes. 4. Draflazine, at concentrations up to 100 mumol l-1, did not produce negative inotropic effects in atrial and ventricular myocardium. (-)-N6-phenylisopropyladenosine (R-PIA) and carbachol did not reduce force of contraction in ventricular myocardium, but exerted concentration-dependent direct negative inotropic effects in atrial myocardium. 5. The data provide evidence that draflazine specifically binds to the nucleoside transporter of the human heart and erythrocytes with high affinity. The compound does not produce negative inotropic effects at concentrations as high as 100 micromol 1-1.6. Draflazine could be a useful agent for cardio preservation because it does not produce cardio depressant effects. Thus, it may be possible to perfuse explanted hearts directly with this agent without the hazard of cardiodepression.

Adult↗
PubMed1994

Endothelialization of cardiac valve bioprostheses.

The main disadvantage of implanted xenograft valves used in cardiac surgery is their poor clinical long-term result, due to early tissue degeneration. In order to improve the performance of such glutaraldehyde fixed bioprostheses, a biological coating with viable endothelial cells was suggested. Therefore, glutaraldehyde preserved bovine pericard patches, as well as commercially available xenograft valves, were lined using human venous endothelial cells or microvascular cells from the subcutaneous fat tissue. Before cells were transplanted into their new environment, grafts were treated with an amino acid solution in order to neutralize the cytotoxic effect of free aldehydes, and precoated with fibronectin-heparin and basic fibroblast growth factor (bFGF) or endothelial cell growth supplement (ECGS) in order to enhance cell proliferation. Coated specimens were kept in culture conditions for a further seven days. Proliferation of transplanted cells was verified by an increase of activation following 3H-thymidine incorporation, while the maintained metabolic cell activity was demonstrated via Prostacycline (PGI2) measurement. Morphology was evaluated by means of scanning electron microscopy (SEM). As evaluated by the beta-Counter, 7 ng/ml bFGF (288,727 +/- 39,668 counts on day 4) substantially enhanced cell proliferation after seeding, opposed to the stimulation with 30,000 ng/ml ECGS (91,924 +/- 1129 counts on day 4), (p < 0.001). The PGI2 release of transplanted cells was stimulated with 25 microM Na arachidonic acid by the factor 2.6 +/- 0.3 and inhibited with 5 mM acetylsalicylic acid by the factor 0.7 +/- 0.2 on day 4 when compared with the basic level.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMed1994

Homograft aortic root replacement for destructive valve endocarditis. The benefit of an in-house homograft bank.

This report concerns the surgical treatment of a 45-year old patient with active staphylococcus-endocarditis of the aortic valve which resulted in an aortic root abscess and consequently in a ventricular aortic discontinuity. A technique of homograft aortic root replacement after removal of all infected and necrotic areas is described. After a six month follow-up, the patient is asymptomatic (New York Heart Association functional class I) and shows no signs of recurrence of endocarditis. This case report makes the benefit of an in-house homograft-bank system obvious.

Abscess↗
PubMed1994

New morphologic aspects of explanted Hancock Extracorporeal pericardial bioprostheses.

Between 1981 and 1987 a total of 479 Hancock Extracorporeal bovine pericardial bioprostheses were implanted in 458 patients. During the time period from 1990 to 1993, 21 valves, 15 in the aortic and six in the mitral position, had to be removed 72 to 109 months after implantation. The mean age of these patients at the time of implantation was 49.7 +/- 10.5 years. All 21 removed as well as one unimplanted bioprosthesis were morphologically investigated. Visual examination, radiography, histology and ultrastructural observations were performed using scanning and transmission electron microscopy. In addition, clinical data were correlated to morphological findings. All valves failed due to cusp tears originating at the stent posts. Calcification was minimal in five valves, moderate in 10, and severe in five valves. Only one valve showed no mineralization at all. The late morphologic changes were associated with thickening of valve leaflets, tissue delamination, calcification, degeneration of collageneous network, and extensive insudation of plasma proteins and lipids. The present findings suggest that denatured collagen molecules may be capable of inducing immune response.

Adult↗
PubMed1993

Alterations of cell-mediated immune response following cardiac surgery.

Nosocomial infections in patients following cardiac surgery are frequently associated with opportunistic microorganisms indicating a dysregulation of cell-mediated immune response. The objective of this prospective randomized trial, therefore, was to investigate the mechanisms of dysregulation and the counterregulatory effects of immunomodulation. Twenty patients underwent conventional postoperative therapy, another 20 patients received indomethacin, which inhibits synthesis of the down-regulating mediator prostaglandin E2, and a further 20 patients were given thymopentin in addition to indomethacin, thereby augmenting activation and differentiation of the T-lymphocytes. The immunologic parameters studied included T-lymphocytes and monocytes as well as interleucin (IL)-1 and IL-6 synthesis by monocytes, and IL-2 and IL-6 synthesis by T-lymphocytes. Following cardiac surgery a significant, persistent reduction of T-lymphocytes and IL-2 synthesis as well as significant monocytosis could be observed. Indomethacin treatment resulted in a normalization of the cellular imbalance at the end of the first postoperative week, but IL-2 synthesis remained significantly reduced during the entire observation period. Conversely, with combined indomethacin and thymopentin treatment restoration of cellular distribution as well as protection of IL-2 synthesis could be achieved. These results indicate a quantitative and functional impairment of the forward regulation of cell-mediated immunity. It was shown for the first time that combined indomethacin and thymopentin treatment could successfully counteract these immunomechanistic alterations.

Aged↗
PubMed1993

CT and MR evaluation of pericardial constriction: a new diagnostic and therapeutic concept.

Eighty patients with pericardial constriction confirmed by catheter data were studied by CT (n = 79), MR imaging (n = 24), or both. To determine the validity of these imaging methods for subsequent treatment, 30 patients' studies were evaluated retrospectively (1980-1984) and 50 (1985-1991) prospectively. Twenty patients from the first group and 30 patients from the second group underwent pericardiectomy. By systematic analysis of CT scans and MR images it was possible to characterize the morphology of pericardial constriction (n = 80); to identify global (n = 27), right-sided (n = 46), left-sided (n = 2), annular (n = 2), effusive (n = 2), and epicardial (n = 1) forms of pericardial constriction; and to define parameters of myocardial atrophy and fibrosis (n = 17). Seventeen patients had myocardial atrophy, fibrosis, or both. Seven of them underwent pericardiectomy; all died of acute myocardial failure (100%). Four (9.3%) of 43 patients without myocardial atrophy or fibrosis died as a consequence of other complications. The method of thoracotomy and periepicardiectomy was continuously adjusted to the preoperative CT and MR findings. Thus, the clinical use of CT and MR imaging in patients with known or suspected pericardial constriction is based on (a) exclusion of patients with restrictive hemodynamics from diagnostic thoracotomy, (b) preoperative determination of the method of thoracotomy and extent of pericardiectomy, and (c) exclusion of patients with myocardial atrophy or fibrosis from pericardiectomy.

Adult↗
PubMed1993

Long-term results of pacemaker therapy after orthotopic heart transplantation.

The objectives of this study were to identify: (1) the indications for pacemaker implantation; (2) the long-term survival; (3) the percentage of bradyarrhythmias below 50 beats/min persisting for more than 3 months; and (4) the variables predicting persistent bradyarrhythmias following orthotopic heart transplantations. During the recent decade (August 1, 1981 through December 31, 1991), 237 patients underwent orthotopic heart transplantation at our institution. Twenty-six recipients (11%) showed evidence of a symptomatic bradyarrhythmia due to sinus node dysfunction (n = 25) or complete heart block (n = 1), which required insertion of a permanent pacing device. During a mean follow-up period of 17.2 months (range 3 to 57 months), five patients (19%) died and one was lost to follow-up. Actuarial survival at 1 and 4 years were 81% and 65%, respectively, as compared to 79% and 69%, respectively, in patients without permanent pacemakers. Holter monitoring after 3 months (n = 25) and 1 year (n = 14) showed a spontaneous heart rate below 50 beats/min in six (24%) and three patients (18%), respectively. None of the tested variables predicted the necessity of initial pacemaker implantation. However, in patients requiring permanent pacing for a period longer than 3 months, ischemic time of the donor heart was found to be significantly longer as compared to the other patients (221 +/- 76 min vs 137 +/- 91 min, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Changes in lymphocyte subsets and mitogen responsiveness following open-heart surgery and possible therapeutic approaches.

Septic multi-organ failure represents a common cause for operative mortality following open-heart surgery. One major reason might be the depression of cell-mediated immunity. The purpose of this prospective randomized trial was to quantify and specify the effects of open-heart surgery on cell-mediated immune mechanisms. In addition, the immunorestorative potential of a combined immunomodulatory therapy with the cyclooxygenase inhibitor indomethacin and the thymomimetic substance Thymopentin versus single drug administration of indomethacin was investigated. Twenty patients were given indomethacin for the first 5 postoperative days (group A). Another 20 patients also received Thymopentin perioperatively and on the second and fourth postoperative days (group B), while 20 patients underwent conventional therapy (group C). Cell-mediated immune response was quantified in vitro by measuring CD3+ T-lymphocytes and their subsets, CD4+ T-helper and CD8+ T-suppressor cells. Lymphocyte responsiveness to a specific (Antigen-Cocktail) and non-specific mitogen (phytohemagglutinin) provided information about the quality of cell-mediated immune response. On the first postoperative day CD3+ T-lymphocyte counts and Antigen-Cocktail-induced lymphocyte proliferation decreased significantly in all groups. The number of CD4+ T-Helper cells fell significantly only in groups A and C, while the decrease in group B was not statistically significant; the same applied to phytohemagglutinin-induced lymphocyte response. The CD4+/CD8+ ratio was significantly depressed only in group C, decreased slightly in group A and did not change as compared to baseline values in group B. All investigated parameters remained significantly depressed until the seventh postoperative day in group C.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Haemodynamic and oxymetric investigations on patients under rate-responsive dual-chamber stimulation during exercise.

Rate-response dual-chamber pacing combines the advantages of atrio-ventricular synchrony and rate adaptation in patients suffering from binodal disease. However, it is not known if patients really benefit from the additional rate response under exercise conditions. Therefore, 15 patients suffering from binodal disease received rate-responsive dual-chamber pacemakers. 1, 3, and 6 months postoperatively haemodynamic parameters and oxygen consumption were measured during treadmill ergometry under conventional (DDD) and rate-modulated AV-universal stimulation (DDDR). Using the NCCOM3-R7 (Osypka) technique, rate (f), cardiac index (CI), stroke volume index (SVI), and the end-diastolic volume index (EDVI) were determined non-invasively. Oxygen consumption (VO2) was measured with the Biotec Oxysuper. Based on preoperative status (NYHA) and ventricular contractility, which was determined by means of echocardiography, the patients were divided into two groups: Group I (n = 8) with normal ventricular contractility demonstrated a moderate increase of intrinsic heart rate during exercise. Group II (n = 7) with impaired ventricular contractility showed only a slight or no increase in intrinsic heart rate. When comparing DDD and DDDR pacing a significant increase of CI and VO2 was found for the rate-modulated pacing mode in group II. The reverse was found for patients of group I. The difference between the two groups was statistically significant. According to these results, only patients with nearly no increase in intrinsic sinus heart rate and impaired ventricular function can be expected to benefit from the additional rate-adaptation of a dual-chamber pacemaker.

Adult↗