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Biomedical subjects

A Markewitz

Publications and source records attributed to A Markewitz.

At least 55 records · Page 3Linked to original sources
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↗
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↗
PubMed1991

Immunomodulatory therapy with thymopentin and indomethacin. Successful restoration of interleukin-2 synthesis in patients undergoing major surgery.

Prostaglandin E2 (PGE2)-mediated monocyte (M phi) suppressor activity and inadequate T-helper cell function represent the mechanistic keystones of trauma-induced impairment of cell-mediated immunity (CMI). In a prospective randomized trial, the immunorestorative potential of a combined therapy with the thymomimetic substance Thymopentin (TP-5; Timunox, Cilag GMBH, Sulzbach, FRG) and the cyclooxygenase inhibitor indomethacin (Indo) in 60 patients (mean age, 63 +/- 2 years) undergoing open heart surgery was studied. Perioperative immunologic screening was carried out on days -2, 3, 1, 5, and 7 and included the in vivo delayed type hypersensitivity (DTH) skin response, phenotyping for peripheral blood mononuclear cell (PBMC)-specific and nonspecific induction of lymphoproliferative responses, in vitro interleukin-2 (IL-2) synthesis, as well as the serum concentration of D-erythro-Neopterin (NPT) and of gamma interferon (gamma-IFN). The study protocol comprised three groups (n = 20): PA (Indo 150 mg administered intravenously on days 0 to 5), PB (TP-5 administered subcutaneously on days 0, 2, 4, and Indo), and PC (control). In contrast to PC, significant immunorestoration could be demonstrated in PB, as DTH scores on day 7, as well as proliferative responses in cell cultures were not depressed after operation (p less than 0.05). Cell-surface receptor expression for the CD3+, CD4+, and IL-2 receptor-positive (IL-2R+) lymphocyte subpopulations following surgery was reduced to 75% of baseline values in PC, while in PB, receptor protection for CD4+ and IL-2R+ subpopulations (more than 15% above baseline) was observed. Interleukin-2 synthesis (average baseline value, 0.7 + 0.08 U/mL) in cell cultures of PC was massively suppressed, with lymphokine concentrations in the supernatants never more than 0.27 +/- 0.05 U/mL. In PA cultures, IL-2 synthesis was impaired as well but not as precipitously as in PC. In contrast, in PB cultures, the average IL-2 production on consecutive postoperative days was never below baseline values. This study clearly demonstrates that the combined Indo/TP-5 therapy is superior to single Indo administration and can adequately preserve and/or restore intact M phi T-cell interaction and thus appears to be a feasible approach to maintain normal host defense activity in traumatized individuals.

Adjuvants, Immunologic↗
PubMed1991

What's the price to be paid for rate response: AV sequential versus ventricular pacing?

The purpose of this study was to compare the effects of atrioventricular (AV) sequential and ventricular pacing at rest and during exercise on parameters of left ventricular performance. Twenty-five patients were studied by means of first pass radionuclide angiography. Pacing rates increased significantly (P less than 0.001) during exercise in both pacing modes, resulting in a significant increase in the cardiac index (P less than 0.001). Pulmonary transit times decreased significantly (P less than 0.001) during exercise in both pacing modes with a significantly shorter pulmonary transit time for AV sequential pacing at rest (P less than 0.01) and during exercise (P less than 0.05), indicating impaired left ventricular function in ventricular pacing. Regional left ventricular wall movement deteriorated significantly during exercise in both pacing modes (P less than 0.02), with a significantly worse performance during ventricular pacing at rest (P less than 0.05) and during exercise (P less than 0.05). Therefore, the price to be paid for rate response is a deterioration of regional wall movement. An additional loss of AV synchrony worsens the situation. It is concluded that rate modulated pacing requires preservation of AV coordination to optimize left ventricular performance.

Arrhythmia, Sinus↗
PubMed1990

[Fully implantable catheter systems. Long-term results--complications].

Between January 1984 and March 1989 we employed two different types of totally implantable venous access systems (57 Port A Cath/25 Theraport) in 82 patients (24 male/58 female). The indication for implantation was the need for long-term parenteral drug treatment of a malignant disease. The duration of the follow-up period was limited by the residual lifespan of the respective patient, 7.2 months on average (range: 3-37 months). In more than 90% (n = 75; 91.5%) of the patients the device functioned normally. Complications were observed in 7 patients (8.5%) (thrombosis in 3, pneumothorax in 2, infections in 2). The results indicate that the use of a totally implantable venous access system is a useful supportive measure in patients requiring long-term Cytostatic and parenteral therapy.

Adolescent↗
PubMed1989

[Atrial septum rupture following blunt thoracic injury within the scope of polytrauma].

Blunt thoracic trauma is a frequent diagnosis in polytraumatic patients, blunt cardiac trauma a rare finding. Severe cardiac injuries e.g. myocardial rupture normally result in immediate death of the patients. If patients survive a cardiac trauma, it often remains unrecognized. The interval between trauma and diagnosis of cardiac injury can make up several months up to years. This applies in particular for the traumatic atrial septal defect. A case report of a traumatic atrial septal defect with left to right shunting due to blunt thoracic trauma in a young man is presented. To our knowledge this is the second case of a successfully repaired traumatic atrial septal defect in literature. Problems regarding diagnosis of the less commonly observed blunt cardiac traumas are discussed.

Adolescent↗
PubMed1988

Reliability of atrial screw-in leads.

The aim of this study was to investigate long-term performance of a carbon coated atrial screw-in lead. During implantation of 247 leads of this type we measured an average stimulation threshold of 0.74 (range: 0.2-1.6 V) at 1 ms pulse width. Mean lead impedance came to 446 ohms (range: 263-1000 ohms) resulting in an arithmetical energy consumption of 1.51 microJ (range: 0.1-7.21 microJ). Average P wave amplitude was 3.9 mV (range: 1.3-11 mV). After a mean follow-up of 16.4 months (range: 3-60 months) we found excellent threshold results in 76% of the patients permitting a safety programming at half of nominal value. An additional 14% nominal settings could be retained. With regard to chronic lead impedance of 488 ohms (range: 315-1327 ohms) we calculated an average chronic energy consumption of 10.83 microJ (range: 1.62-22.78 microJ) during safety programming. This made up 34.6% of the corresponding energy consumption during nominal programming. Eighty percent of the patients showed chronic P waves above 2 mV; nearly half of them (n = 94 = 38%) showed a proper sensing function even when programmed to minimal sensitivity settings or above 4 mV. In 19 leads (8%) we observed unsatisfying threshold results requiring high output programmings. All threshold increases occurred within the first year, 84% (n = 16/19) within the first 3 postoperative months. An additional five leads (2%) were found to have a loss of capture, and one (0.5%) a loss of sensing.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbon↗
PubMed1987

Particularities of dual chamber pacemaker therapy in patients after orthotopic heart transplantation.

Since August 1981, 33 orthotopic heart transplantations were performed in our hospital. Three of these patients (9%) had sinus bradycardias with rates as low as 30 beats/min; they were treated by implantation of a dual chamber pacemaker. These patients had two atria as a result of orthotopic heart transplantation, but only the donor atrium was suitable for positioning the atrial lead. In the postoperative period, some nonsurgical complications were observed in one patient who developed atrial fibrillation which we treated with drugs. A cyclosporin-evoked tremor produced several asystoles due to false inhibition by myopotential interference in the VVI mode. During an episode of acute rejection combined with renal insufficiency, loss of atrial and ventricular sensing occurred. The other patients showed no pacemaker-related complications. Our findings in this unique population of pacemaker patients are discussed.

Adult↗
PubMed1986

[Improved regional myocardial function after aortocoronary bypass surgery noninvasive studies using the first-pass technic].

50 patients after coronary artery bypass grafting were matched with 50 not-operated patients. After a follow-up period of four years they were investigated by first pass radionuclide angiography. Revascularized myocardial areas showed significantly higher regional ejection fraction during exercise and in territories with prior myocardial infarction. The results proved the hemodynamic benefits of coronary artery bypass grafting even in territories with poor myocardial function.

Angina Pectoris↗
PubMed1986

Surgical treatment of aneurysms of the ascending aorta. Twelve years' experience in 66 patients.

This study presents the results in 66 patients undergoing surgery for concomitant supracoronary vascular interposition and valve replacement carried out at the Department of Cardiac Surgery of the University of Munich, West-Germany, over a period of 12 years (from July 1, 1973 to June 30, 1985) using a technique similar to that described by Wheat. Forty-seven percent of the cases were true aneurysms and 20% chronic dissections. Thirty-three percent of patients had acute dissections. Early mortality was 16% in the total patient population, 9% in the group having true aneurysm and 32% in the group having acute dissection. No early death was observed in association with chronic dissections. The actuarial one-year survival rate in patients with true aneurysm or chronic dissection was 83.6%, and 54.1% in patients with acute dissection. The corresponding 4-year survival rates were 76.4% and 54.1%, respectively. The average improvement according to the New York Heart Association classification was 1.5 grades. These results confirm that the operative approach to ascending aortic aneurysms is superior to medical treatment, with the operative method involving vascular graft without concomitant aortic valve replacement as well as the method described by Wheat having both proved successful.

Acute Disease↗
PubMed1986

Ventricular preexcitation following catheter ablation of the His bundle in concealed WPW syndrome.

Catheter ablation of the His bundle is reported in a patient with drug-refractory supraventricular tachycardia meeting standard criteria of concealed WPW syndrome (conduction of the accessory atrioventricular pathway in retrograde direction only). After successful ablation of the His bundle, anterograde conduction along the accessory pathway, to our surprise, became apparent. During twelve months of follow-up, the patient was free of the tachycardia recurrences off antiarrhythmic drugs. While the clinical problem has been solved, the patient may--in case he should develop atrial fibrillation--present with rapid anterograde conduction via the accessory pathway. Based on this experience, better electrophysiologic protocols are needed to evaluate anterograde accessory pathway conduction properties in 'concealed' WPW syndrome, thus permitting one better to decide whether and which site of ablation should be chosen in drug-refractory cases.

Bundle of His↗
PubMed1986

Complications in dual chamber pacing: a six-year experience.

In a six-year period (1980-1985), 345 dual chamber pacing systems were implanted in our hospital. Intraoperative complications were rare (n = 5/345 = 1.4%). 25 patients (7%) have died, 11 (3%) were lost to follow-up. A total of 39 patients (13%) showed minor problems, which could be overcome by reprogramming. Another 48 complications (15%) required reoperation. Nearly 70% of those reoperations (n = 31/48) were caused by a malfunction of the atrial lead. This high complication rate of 9% related to all implanted atrial leads could be reduced in the last three years to 2%. We could maintain a dual chamber stimulation mode (DDD, DDI, DVI, VDD) in 396 patients (99%). We conclude that improvements in lead design, pulse generator's programmability, and surgical experience have reduced complication rates to acceptable low values. Meanwhile, dual chamber pacing can be considered as safe as single chamber pacemaker therapy.

Adolescent↗