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Biomedical subjects

A Markewitz

Publications and source records attributed to A Markewitz.

At least 19 recordsLinked to original sources
PubMed1995

Failures of epicardial and transvenous leads for implantable cardioverter defibrillators.

Lead failures constitute a major risk for patients with an implantable cardioverter defibrillator (ICD). However, data about the incidence and patterns of ICD-lead failures in a larger population are lacking. We analyzed the short-term and midterm performance of 27 epicardial and 103 nonthoracotomy ICD-lead systems during a follow-up period of 36 +/- 21 months and 22 +/- 10 months, respectively (p < 0.05). The failure rate was 5 (19%) of 27 in the epicardial and 6 (6%) of 103 in the nonthoracotomy group (p < 0.05). The most common symptom was erroneous detection of ventricular fibrillation from artifact sensing in five patients. Two patients had to be resuscitated because of failure to defibrillate. Loss of pacing and loss of sensing were seen in two patients. Only two asymptomatic lead fractures could be diagnosed on routine radiograph. In conclusion, there was a considerable rate of lead failures, especially in epicardial systems. Long-term studies addressing the longevity of ICD leads, mechanisms of their failures, and improved diagnostic facilities are important to further increase the safety of this therapeutic approach.

Defibrillators, Implantable↗
PubMed1995

Osteosynthetic reconstruction in a patient with Gardner-Diamond syndrome.

Based on clinical observations in one female patient who suffered from Gardner-Diamond syndrome, we noticed that surgery can be performed without any bleeding complications, although operations normally are contraindicated in persons with this condition. Additionally, a correlation seems to exist between ASS and sexual and hormonal maturity.

Autoimmune Diseases↗
PubMed1995

Defibrillator implantation in a patient with a persistent left superior vena cava.

The implantation of a transvenous cardioverter defibrillator (PCD 7217B) was performed in a patient with a persistent left superior vena cava. The defibrillation electrodes were positioned in the right ventricle and the superior vena cava via the right subclavian vein. A subcutaneous patch had to be implanted at the left lateral chest wall to achieve sufficient defibrillation thresholds. Three weeks later the system had to be removed because of a generator pocket infection. During the second implantation we placed one electrode in the persistent left superior vena cava perpendicular to the electrode in the right ventricle. Using this configuration transvenous defibrillation was possible without an additional subcutaneous patch.

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↗
PubMed1994

Reduction of cyclosporine-induced nephrotoxicity by cilastatin following clinical heart transplantation.

The objective of this prospective, randomized, placebo-controlled, single-blinded study in 28 heart-transplanted patients was to investigate whether the dehydropeptidase inhibitor cilastatin reduces cyclosporine-induced nephrotoxicity. Cilastatin is available only in combination with imipenem, a beta-lactam antibiotic to which it is added for reduction of nephrotoxic side-effects of the antimicrobial agent. Patients received either 100 ml placebo (n = 12) or 100 ml (500 mg) imipenem/cilastatin (n = 16) twice perioperatively, and 4 times daily for the first 7 postoperative days. Serum creatinine and urea, as well as urine concentrations of N-acetyl-beta-D-glucosaminidase, which is directly correlated with tubular cell damage, were used as markers for renal function. Thromboxane B2 and 6-keto-prostaglandin F1-alpha serum concentrations were determined to investigate whether there is an imbalance in synthesis of thromboxane A2 and prostacyclin as a possible mechanism for cyclosporine-induced nephrotoxicity. Two placebo patients and 6 patients receiving imipenem/cilastatin had to be excluded from further analysis. Three of 10 placebo patients required hemofiltration, and 2 of them even required hemodialysis, as compared with none in the imipenem/cilastatin group. Creatinine concentrations increased significantly from the second to the fourth postoperative day in the placebo group, but remained nearly normal in cilastatin patients (P < 0.05 for intergroup comparison on postoperative days 2-4). The same trend was observed in urea and N-acetyl-beta-D-glucosaminidase concentrations, without the difference reaching statistical significance. For thromboxane B2 and 6-keto-prostaglandin F1-alpha no differences between the groups could be found. These results suggest that imipenem/cilastatin can counteract acute cyclosporine-induced nephrotoxicity, which appears to be associated with alterations of tubular cell function. The combined use of cyclosporine and imipenem/cilastatin appears to be advantageous in patients following heart transplantation during the initial postoperative period.

6-Ketoprostaglandin F1 alpha↗
PubMed1994

Hemodynamic deterioration during ICD implant: predictors of high-risk patients.

Defibrillation threshold (DFT) testing during implantation of the cardioverter defibrillator is associated with hemodynamic deterioration and pump failure in many patients. We investigated the influence of DFT testing on cardiac function intraoperatively using a balloon-tipped catheter. In 13 consecutive patients with a nonthoracotomy approach, a mean of 3.4 +/- 1.4 episodes of ventricular fibrillation were induced with an overall ischemic time of 87 +/- 54 seconds. At the end of DFT testing, patients with a left ventricular ejection fraction (EF) of < 30% had significant impairment of cardiac index (1.6 +/- 0.5 L/min/m2 after testing vs 2.2 +/- 0.6 L/min/m2 before the procedure). One patient with severely comprised ventricular function needed prolonged positive inotropic support. The left ventricular function of patients with a preoperative EF > or = 30%, however, was not changed (2.2 +/- 0.5 L/min/m2 after testing and 2.2 +/- 0.5 L/min/m2 before testing). The two groups did not differ with respect to the number of testing episodes, ischemic time, or DFT. Thus patients with a low preoperative EF (< 30%) are threatened by a severe left ventricular deterioration during ICD implantation. Close hemodynamic monitoring with a balloon-tipped catheter is recommended in these patients.

Cardiac Pacing, Artificial↗
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

[Surgically treated thoracic aortic dissection. The angiographic follow-up of the perfusion relations].

Control angiography in arterial DSA technique was performed in 27 patients after operative treatment of acute aortic dissection (17 patients with type A dissection) respectively chronic aortic dissection (9 patients with type A dissection/1 patient with type B dissection). The mean interval between surgery and angiography was 59 months. All patients were free from symptoms due to organ complications or redissection. Persistent patency of a false lumen was observed in 40.7% (52.9% after operative treatment of an acute dissection; 20% after operative treatment of a chronic dissection). In all cases with a persistent false lumen the dissection originated at the distal anastomosis. In all patients the beginning of the dissection and the perfusion of the supra-aortal, visceral and iliac vessels whether by the true or false lumen could be shown. In 54.5% the Tr. brachiocephalic trunk was involved in the dissection. In 45.5% the left renal artery was solely perfused by the false lumen. Angiography in arterial DSA technique is evidently a valuable technique to document the beginning and extension of a dissection, sufficiency of the aortic valve, re-entries of the dissection, perfusion of the aortal branches, and the flow in both channels.

Acute Disease↗
PubMed1994

[Inadequate therapeutic effects of implantable cardioverter/defibrillators: etiology, therapy and prevention].

With the increasing number of implantable cardioverter-defibrillator (ICD) implantations in patients with sustained ventricular tachyarrhythmias, there is a growing interest in typical complications associated with this therapy. We analyzed the reasons and the incidence of inadequate therapy deliveries in 100 patients with epicardial (n = 27) or transvenous (n = 73) ICDs during a follow-up period of 10 +/- 8 months. A total of 21 of 100 patients received inadequate therapies. The most common reason was sinus tachycardia in eleven patients. Additional unnecessary shocks were avoided by reprogramming and application of beta-blockers. Lead failures caused the erroneous detection and defibrillation of ventricular fibrillation without any preceding clinical symptoms in four patients with an epicardial and in one patient with a transvenous ICD. All patients underwent successful surgical revision of their system. Atrial fibrillation with rapid ventricular response triggered inadequate shocks in four patients. Following digoxin administration no patient had additional inadequate shocks. In one patient non-sustained tachycardias caused unnecessary defibrillations. These results demonstrate that inadequate defibrillations are a common complication in patients after ICD-placement. The performance of x-ray, stress testing, and Holter monitoring on a regular basis may facilitate early diagnosis of possible reasons for unnecessary therapy deliveries. The improvement of detection and memory functions in future ICD-generations appears to be mandatory as well.

Adolescent↗
PubMed1993

Regulation of acute phase response after cardiopulmonary bypass by immunomodulation.

The object of this prospective, randomized trial was to study the dysregulation effects of cardiopulmonary bypass on the synthesis pattern of interleukin-1, tumor necrosis factor, and interleukin-6, which have been identified as the key mediators of acute phase response. In addition, the counterregulation achieved by administration of indomethacin, which blocks the downregulating mediator prostaglandin E2, or indomethacin combined with thymopentin, which enhances T-lymphocytic reactivity, was investigated. Sixty patients who had undergone open heart operations were included in the study. These patients were divided into three groups: group A (n = 20) received both indomethacin and thymopentin, and group C (n = 20) served as control. In control patients interleukin-1 and tumor necrosis factor synthesis were suppressed postoperatively. This effect was significantly counteracted by indomethacin with no further improvement by adding thymopentin. Interleukin-6 synthesis increased in all groups. Although indomethacin treatment alone had little effect on this phenomenon, additional administration of thymopentin significantly reduced elevated interleukin-6 synthesis. Corresponding differences in clinical outcome could not be detected due to small patient numbers. This study was, however, able to demonstrate that an immunomodulatory therapy can influence alterations in immune mechanisms after cardiopulmonary bypass.

Acute-Phase Reaction↗
PubMed1993

Hemodynamic changes due to intraoperative testing of the automatic implantable cardioverter defibrillator: implications for anesthesia management.

During the insertion of an automatic implantable cardioverter defibrillator, repeated induction of ventricular tachycardia or ventricular fibrillation and subsequent defibrillation is performed to determine the defibrillation threshold. In this study, the influence of these testing episodes on myocardial function was investigated in 13 patients under general anesthesia. Preoperative ejection fraction (EF) was 41 (14 to 84) % (median and range). Testing was performed 3 (2-5) times. During these testing episodes the patients received a total of 4 (2-8) countershocks. Patients with a preoperative EF < 30% (N = 5) showed a significant reduction of cardiac index (CI) from 2.2 (1.5-3.3) L/min/m2 before testing to 1.5 (1.3-2.3) L/min/m2 after the last testing episode, and of left ventricular stroke work index (LVSWI) from 32 (14-53) g.m/m2 before testing to 22 (7-43) after the last testing episode. These changes were not related to the total fibrillation time or the cumulative defibrillation energy. Patients with a preoperative EF > 30% (N = 8) showed no significant changes of CI (2.15 [1.8-3.0] L/min/m2 v 2.15 [1.7-3.0] L/min/m2) or LVSWI (35 [28-48] g.m/m2 v 33.5 [27-52] g.m/m2). Comparison of the two patient groups revealed similar hemodynamic baseline values, but significant differences in LVSWI after the last testing episode. Defibrillation testing may produce a further reduction in myocardial performance in patients with preexisting poor cardiac function.

Adolescent↗
PubMed1993

Successful restoration of cell-mediated immune response after cardiopulmonary bypass by immunomodulation.

The objectives of this prospective randomized trial were to quantify immunosuppressive effects of cardiopulmonary bypass, to identify mechanisms responsible for postoperative immunosuppression, and to investigate the effects of immunomodulatory intervention on these mechanisms. Sixty patients were studied after cardiopulmonary bypass. Immunomodulatory therapy consisted of the cyclooxygenase inhibitor indomethacin, which blocks the downregulating agent prostaglandin E2, and thymopentin, which enhances T-lymphocytic activity. Twenty patients each received indomethacin either alone or combined with thymopentin. Twenty patients served as the control population. Our in vitro studies showed a decrease of CD4+ helper/inducer T cells and interleukin-2 receptor expression on T lymphocytes, while CD8+ suppressor/cytotoxic T cells and monocytes increased. Additionally, a depression of interleukin-1 and interleukin-2 synthesis as well as concurrent low gamma-interferon serum concentrations could be documented. These results indicate a downregulation of cell-mediated immune response. As an in vivo correlate of the immunomechanistic alterations, patients demonstrated an impaired delayed-type hypersensitivity response to an antigen skin test battery. These changes in immunoreactivity could be successfully counteracted by the combined immunomodulatory regimen, whereas sole indomethacin treatment could only partially restore depressed host defense parameters. With this study we could demonstrate for the first time that human lymphocytic interleukin-2 synthesis, which represents the key event among forward regulatory immune mechanisms, can be protected via in vivo immunoaugmentatory therapy and that this therapy can successfully counteract immunosuppressive effects of cardiopulmonary bypass.

Aged↗
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↗