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Biomedical subjects

D Hammel

Publications and source records attributed to D Hammel.

At least 55 records · Page 3Linked to original sources
PubMed1999

Left ventricular assist system support is associated with persistent inflammation and temporary immunosuppression.

BACKGROUND: In patients undergoing left-ventricular assist system support, it has not been elucidated to which extent mechanical circulatory support itself as opposed to the underlying condition of endstage heart-failure contributes to perturbation of immune homeostasis. METHODS: In eleven heart transplant candidates who had to undergo Novacor left-ventricular assist device bridging, we prospectively sampled interleukin-6, T-cell and monocyte subsets and compared them to fifteen UNOS status II patients awaiting cardiac transplantation on medical heart failure treatment as outpatients at the time of LVAS implantation/listing decision as well as 2.0+/-1.2 months and 4.5+/-2.3 months later. In order to assess deviations in both groups from normal values, thirty-two healthy subjects served as reference group. RESULTS: Patients undergoing Novacor bridging had higher C-reactive protein, leukocyte, neutrophil, and monocyte levels at all three times, and exhibited lower CD3 +, CD4+, CD3+/CD45 RO T-cell and natural killer cell counts than medically treated patients awaiting transplantation 2 months after the LVAS implantation/listing decision. In comparison to controls, both groups had higher levels of inflammatory activation and lower levels of immunocompetence at all three times. CONCLUSIONS: While both groups of endstage heart failure patients show immunological alterations compared to controls, patients who have to be bridged by the Novacor LVAS exhibit a more pronounced activation of inflammatory markers. This may be due to more advanced heart failure but the device itself also may contribute to more pronounced inflammation and a temporary suppression of immunocompetent cells.

Adult↗
PubMed1999

Use of an intraaortic balloon pump in patients with impaired left ventricular function.

Prophylactic use of an intraaortic balloon pump (IABP) prior to open-heart surgery in patients with impaired left ventricular function is still under debate. Patients with left ventricular ejection fraction (LVEF) < 40% were therefore compared according to time of IABP placement, viz. preoperative (n = 56), intraoperative (n = 40) or postoperative (n = 17), and also with patients who did not receive mechanical support despite LVEF < 40% (n = 78). The main indication for preoperative IABP insertion was severely impaired left ventricular function (80%), while patients with intraoperative or postoperative IABP placement mainly presented with low cardiac-output syndrome (70%/53%). Preoperative IABP was associated with a low mortality rate (8.9%), whereas patients with intraoperative or postoperative IABP placement had a high mortality risk and an increased catecholamine requirement. Of the patients scheduled for surgery without prophylactic IABP, 19% required intra- or postoperative insertion. Prophylactic placement of IABP thus reduced the mortality rate as well as the postoperative need for mechanical and catecholamine support. Need for intraoperative IABP insertion was associated with high mortality, whereas the outcome after postoperative IABP placement depended on the indication for the measure.

Aged↗
PubMed1999

Intraoperative radiofrequency ablation of chronic atrial fibrillation: a left atrial curative approach by elimination of anatomic "anchor" reentrant circuits.

INTRODUCTION: The percutaneous approach to radiofrequency (RF) catheter ablation for curative treatment of atrial fibrillation (AF) is an investigational technique, and the optimal composition of lesion lines is unknown. We tested an intraoperative RF ablation concept with elimination of left atrial anatomic "anchor" reentrant circuits. METHODS AND RESULTS: In 12 patients with an indication for valve surgery and chronic AF, a right atrial-transseptal approach was chosen for access to the left atrium. AF had been present for 4.3 +/- 3.9 years; the left atria measured 56 +/- 7 mm. Under direct vision, contiguous lesion lines were placed endocardially with temperature-guided RF energy applications for treatment of AF with a specially designed probe. The lesion lines were placed between the mitral annulus and the left lower pulmonary vein, further to the left upper pulmonary vein, from there to the right upper pulmonary vein, and finally to the right lower pulmonary vein. The antiarrhythmic ablation procedure lasted 19 +/- 4 minutes. One patient died postoperatively of low cardiac output. During follow-up of 11 +/- 6 months, chronic AF was ablated successfully in 9 of 11 patients (82%). Six patients were in stable sinus rhythm or intermittent pacemaker rhythm, and three patients were in sinus rhythm with intermittent atypical atrial flutter. CONCLUSIONS: Intraoperative RF energy application for induction of contiguous lesion lines is feasible. Elimination of anatomically defined "anchor" reentrant circuits within the left atrium prevented chronic AF in > 80% of the patients treated. Intraoperative validation of lesion line concepts for curative treatment of AF may be transferred to percutaneous ablation techniques.

Aged↗
PubMed1998

Potential benefit from implantable cardioverter-defibrillator therapy in patients with and without heart failure.

BACKGROUND: Whether patients with heart failure derive a benefit from therapy with implantable cardioverter-defibrillators (ICDs) has been questioned. The purpose of this study was to investigate whether New York Heart Association (NYHA) functional class had an impact on the potential benefit from ICD therapy as assessed from data stored in the memory of ICDs. METHODS AND RESULTS: Between 1989 and 1996, 603 patients (77% men; 59% with coronary artery disease and 16% with dilated cardiomyopathy; age, 57+/-13 years; ejection fraction, 44+/-18%) were treated with an ICD with extended memory function (storage of electrograms and/or RR intervals from treated episodes) in combination with endocardial lead systems. The stages of heart failure (NYHA functional class I through III) at implantation were correlated with overall mortality and the recurrence of fast ventricular tachyarrhythmias (>240 bpm) during follow-up. The potential benefit of the device was estimated as the difference between overall mortality and the hypothetical death rate had the device not been implanted. The latter was based on the recurrence of fast and, without termination by the devices, presumably fatal ventricular tachyarrhythmias. In the overall group, a significant difference between hypothetical death rate and overall mortality was observed (13.9%, 23.5%, and 26.6% at 1, 3, and 5 years, respectively) that suggested a benefit from ICD implantation. In patients in NYHA class I, the estimated benefit, which increased over time, was 15.2%, 29.2%, and 35.6% after 1, 3, and 5 years, respectively. In patients in NYHA class II or III, the estimated benefit increased until the third year (21.8% and 21.9%, respectively) and then remained constant until the fifth year (22.9% and 23.8%, respectively). Even those patients in NYHA class III with a history of decompensated heart failure benefited from ICD implantation. CONCLUSIONS: Analysis of stored ECG data suggests that in patients with a history of ventricular tachycardia or ventricular fibrillation, ICD therapy may lead to a prolongation of life in NYHA classes I through III. The initial benefit is greatest in patients in NYHA class II and class III, but the estimated benefit might persist longest for patients in NYHA class I.

Adolescent↗
PubMed1998

Cerebral and systemic embolization during left ventricular support with the Novacor N100 device.

BACKGROUND: Patients undergoing implantation of left ventricular assist systems (LVAS) are prone to thromboembolic complications. We analyzed the incidence, clinical findings, and outcome of neurologic and systemic thromboembolic events (TE) in patients with the Novacor N100 LVAS. In a subset of patients, transcranial Doppler sonography was used to detect microembolic signals. METHODS: Thirty-six patients underwent implantation of a Novacor N100 LVAS for various reasons. The surgical procedure was elective in 18 patients and scheduled on an urgent or emergency basis in another 18 patients. The assist period lasted from 17 to 336 days (109 +/- 88 days); 22 patients were forwarded to heart transplantation after being supported for 140 +/- 87 days. RESULTS: Clinical cerebral embolism was evident in 17 patients (47%). Thromboembolic events were singular in 8 and multiple in 9 patients; in the latter up to 10 TE occurred (mean +/- SD, 1.4 +/- 2 TE). Leading neurologic symptoms were unilateral hemiplegia in 11, as well as ocular symptoms and aphasia in 12 patients each. Noncerebral TE were detected in 4 patients, 2 of whom underwent an emergency operation for intestinal and iliac artery occlusion. The incidence of TE did not correlate strongly with the interval of LVAS support. Cerebral computed tomography confirmed lesions in 58% of patients. Transcranial Doppler sonography detected microembolic signals on 67% of all recordings, with the microembolic signals being more frequent on days with clinically manifest TE. The outcomes were good, as only 2 patients suffer from neurologic sequelae. CONCLUSIONS: Thromboembolism is still a major threat for patients with LVAS implantation. Neurologic sequelae are frequent but have a favorable prognosis, and systemic complications occur considerably less often. Patient selection, adequate anticoagulation, and transcranial Doppler sonography may help to reduce the incidence of TE.

Adult↗
PubMed1998

Effects of gender of observer and fear of negative evaluation on cardiovascular reactivity to mental stress in college men.

This study investigated the relation between mere observation, the gender of a confederate observer and cardiovascular reactivity to two laboratory challenges, a math task and verbal anagrams, in both individuals with high and low social fear (e.g. fear of negative evaluation). Forty-eight undergraduate males completed the Fear of Negative Evaluation Scale and were categorized as either high or low social fear based on a median split. Sixteen subjects were tested alone, 16 subjects were observed by a male confederate during task performance and 16 subjects were observed by a female confederate during task performance. Cardiovascular measures of heart rate and blood pressure were measured during both tasks and intervening rest periods. Results revealed subjects with high social fear exhibited higher heart rate reactions to the math task and higher diastolic blood pressure reactions to the anagram challenge than low social fear participants, but only when observed by a female confederate. In addition, participants in the male and female observation conditions exhibited greater SBP responses to the anagram task than participants in the alone condition. No group differences on task performance were observed. Cardiovascular reactivity to the two tasks used in this study was impacted by both contextual laboratory factors (i.e. gender of observer) and dispositional attributes of the participant (i.e. social fear).

Adolescent↗
PubMed1998

Successful treatment of a Novacor LVAD malfunction without repeat sternotomy.

Implantable left-ventricular assist devices have been remarkably free of mechanical failures. We describe an uncommon Novacor N100 PCq LVAS malfunction caused by an internal short circuit of the device due to urine aspiration via the vent line. Device replacement was managed via a subcostal approach without sternotomy. Patient recovery was uneventful and successful transplantation was performed one month after the device exchange.

Adult↗
PubMed1998

Effect of platelet inhibitors on thromboembolism after implantation of a Novacor N100--preliminary results.

BACKGROUND: Left-ventricular assist device implantation (LVAD) is still associated with thromboembolism as the optimal anticoagulation is still unclear. We report on the effects of adding platelet inhibitors to our anticoagulation regimen in our Novacor LVAD program. METHODS: Oral platelet aggregation inhibitors (aspirin 330 mg + dipyridamole 75 mg, three times per day) were added to the heparin/phenprocoumon treatment in 9 patients starting on postoperative day 3 to 7 (group A). Of the previous 41 patients, the last 20 patients served as a control group (group B), to reduce any learning curve effect. RESULTS: The mean interval of mechanical support between the two groups was comparable (group A vs B: 148 +/- 127 vs 104 +/- 61 days, n.s.). Accordingly, the cumulative support was much lower in group A (1051 days) as compared to group B (2091 days). In group B, 10 patients (50%) developed clinically evident thromboembolism. The number of events ranged from 1 to 10 (mean 1.4 +/- 2.3), with a total of 32. With addition of platelet inhibitors, the incidence of cerebral embolism dramatically dropped, as only one patient presented with transient ischemic attacks in group A (p < 0.05). Thoracic bleeding as defined by excessive drainage losses requiring redo thoracotomy did not increase (group A vs B: 22% vs 20%, n.s.). CONCLUSION: Addition of platelet inhibitors to heparin/phenprocoumon effectively prevents thromboembolism. However, platelet inhibitors should be postponed until sufficient hemostasis is achieved, since too early administration is associated with an increased risk of bleeding.

Anticoagulants↗
PubMed1998

Relation of urokinase-type plasminogen activator expression to presence and severity of atherosclerotic lesions in human coronary arteries.

Urokinase-type plasminogen activator (UPA) has been implicated in a broad spectrum of pathological processes - e.g. cell adhesion, migration and proliferation and matrix remodeling - that are considered important features of atherogenesis and plaque disruption. In this study, we have analyzed the content and expression of UPA in human coronary arteries and its relation to the presence and severity of atherosclerotic lesions. Segments of coronary arteries obtained from human heart explants (n = 15) were classified by the presence and types of atherosclerotic lesions. UPA was quantitatively determined in protein extracts of the intimal and medial layers. In situ hybridization and immunohistochemical analyses were performed on serial sections of representative tissue specimens. UPA was detected in the extracts as pro-UPA, UPA complexed to plasminogen activator inhibitor-1, or as otherwise inactive UPA antigen, but not in the active two-chain form. Both functional and total UPA were increased several-fold in extracts of advanced lesions, while the ratios of functional over total UPA showed the opposite trend suggesting enhanced UPA inactivation and turnover. UPA expression in early atherosclerotic lesions was particularly prominent in areas of proliferating SMCs in the abluminal part of the neointima, whereas in advanced lesions UPA was widely expressed in macrophage-rich areas adjacent to the rims and shoulder regions of the necrotic cores. The results strongly suggest a causal involvement of UPA in coronary atherogenesis and its clinical outcome.

Coronary Artery Disease↗
PubMed1998

Selection and outcome of ventricular assist device patients: the Muenster experience.

BACKGROUND: Because the number of patients on the waiting list for transplantation is increasing and the stagnation in the number of organs donated has led to a more restrictive listing for transplantation, an increased fraction of patients needs to be bridged mechanically. We examined the hypothesis that selection of these patients with regard to urgency status is critical in determining outcome. METHODS: A cohort of 631 patients referred for transplantation to our center between January 1, 1990, and December 31, 1996, was analyzed. Two hundred ninety-seven patients were listed for transplantation and 157 were given transplantation. Forty-one patients had to undergo ventricular assist device implantation (n=34, Novacor; n=6, TCI Heartmate; n=1, Medos), 39 for bridging to transplantation and 2 for permanent support. Initial transplantation evaluation data were analyzed in 3 subgroups (elective bridging, urgent bridging, emergency bridging) and compared with another and with other patients referred for transplantation, specifically those who did not have to be bridged on the waiting list. RESULTS: Patients who underwent elective or urgent assist device bridging were younger and more compromised than the rest of patients accepted on the waiting list (higher functional class, lower mean arterial pressure, lower cardiac index, lower serum sodium, higher pulmonary capillary wedge pressure). In the elective group, overall survival including perioperative mortality rate was better than in the urgent/emergency group and at least as good as in patients who were stable on the waiting list and did not undergo heart transplantation during follow-up. This should prompt cardiologists and cardiac surgeons to consider assist device implantation earlier.

Adult↗
PubMed1998

Emergency versus elective/urgent left ventricular assist device implantation.

BACKGROUND: The risk and outcome in patients undergoing left ventricular assist device (LVAD) implantation on an emergency basis is still unclear. METHODS: Since April 1993, 40 patients received a Novacor and 8 patients a Heartmate LVAD in our institution. Patients with emergency LVAD placement were compared with the remainder in a retrospective manner. Parameters studied included underlying heart disease, preimplantation dysfunction of kidney, liver, lung, and cerebrum, interval of mechanical support, outcome, and complications. RESULTS: Patients with emergency LVAD placement predominantly were seen with postcardiotomy heart failure (47%) or acute myocarditis (20%) (group A) whereas elective and urgent candidates for LVAD implantation mainly had dilative cardiomyopathy (67%) or ischemic heart disease (30%) (group B). The incidence of secondary organ failure was significantly higher for all organs in group A patients (p < .01). Mean support interval in patients who underwent emergency LVAD implantation was lower (74+/-79 days vs 115+/-80 days), and fewer patients could be forwarded to heart transplantation in this group (22% vs 78%, p < .01). Moreover, bleeding complications were increased in group A (66% vs 30%, p < .01), but not thromboembolism and infection. CONCLUSION: In conclusion, the overall success rate after emergency LVAD implantation was lower, with bleeding being the most frequent complication. To achieve acceptable outcomes in disastrous situations, LVADs should be placed as early as possible.

Adult↗
PubMed1997

[Mechanical myocardial support systems 1997: an overview of inta-aortic balloon counterpulsation to implantable left ventricular support systems].

The development of cardiopulmonary bypass (CPB) to support the systemic circulation during cardiac surgical procedures became a clinical reality in 1953. Although the use of CPB for the treatment of post-infarction cardiogenic shock met with little success, intra-aortic balloon counterpulsation was used successfully in 1968 to reduce ischaemic injury in a patient with cardiogenic shock. Today, a broad spectrum of circulatory assist devices for short- and long-term application is available. Three major indication groups for the use of support devices are established. In low-cardiac-output syndrome after cardiac surgical procedures, short-term devices are utilised to enable myocardial recovery. In transplantation candidates suffering from drug-resistant pump failure, the implantation of long-term devices as a bridge to heart transplantation is indicated, and in NYHA class IV patients with contraindications to heart transplantation, the implantation of long-term devices as an alternative to transplantation is under discussion. In the literature, post-cardiotomy support survival is less than 30% on average. About 70% of mechanically bridged patients have survived to undergo heart transplantation and were transplanted with over 90% survival. Major problems during mechanical support are infection, bleeding, and thromboembolism. In view of patients' natural course without support, these clinical results are favourable.

Defibrillators, Implantable↗
PubMed1997

Influence of enoximone on systemic and splanchnic oxygen utilization and endotoxin release following cardiopulmonary bypass.

OBJECTIVE: We investigated whether the administration of enoximone during and after cardiopulmonary bypass (CPB) improves splanchnic oxygen utilization and thereby gut mucosal integrity in humans by its vasodilating and inotropic properties. SETTING: Surgical intensive care unit (ICU) in a university hospital. DESIGN/PATIENTS: 21 patients (ASA III classification) scheduled for elective coronary artery bypass grafting were enrolled in the study. After induction of general anesthesia, patients were randomly assigned to received a bolus of 0.2 mg/kg enoximone, followed by 5 microg/kg per min (enoximone group), or followed by an equal volume of saline (NaCl group) during and 24 h after the surgical procedure. The following parameters were evaluated at different time intervals: systemic and pulmonary hemodynamics, blood gas analysis of arterial, mixed venous, and liver venous blood, venous and liver venous lactate level, venous and liver venous endotoxin level and intramucosal partial pressure of carbon dioxide for calculation of intramucosal pH (pHi). RESULTS: Enoximone raised cardiac output and oxygen delivery to higher levels than those observed in the NaCl group. In both groups, gastric pHi fell continuously during the study period. The values were significantly decreased 12 h following admission to the ICU. Endotoxin was not detectable at baseline. Both groups showed increased endotoxin levels, with the highest values during the first 6 h postoperatively. The hepatic venous endotoxin level was almost doubled in the NaCl group in comparison to the enoximone group. Endotoxin levels differed in the two groups 6 and 12 h after admission to the ICU. CONCLUSIONS: Improvement of oxygen delivery by enoximone did not prevent gastric mucosal acidosis following CPB. However, since the increase in endotoxin levels in liver venous blood was diminished by using enoximone, the drug seems to have a beneficial effect on tissue damage and barrier function of the gut.

Aged↗
PubMed1997

Cardiac pacemaker infection: surgical management with and without extracorporeal circulation.

BACKGROUND: Pacemaker infections are rare, but serious complications of pacemaker therapy. The generator pocket, the pacing leads, or both may be involved. METHODS: We report on 12 patients with infected pacemaker systems. Four patients suffered from localized generator pocket infections, 6 had infected leads, and 2 patients had both. Pacemaker systems were completely removed in all patients. When the infection was limited to the generator pocket, the pacemaker system was removed at the original implantation site. Extracorporeal circulation was employed for the explantation of infected pacing leads. RESULTS: No complications occurred in patients with localized generator pocket infections. One patient with infected leads who was preoperatively already in a serious clinical condition died of septic shock in the early postoperative period; another patient died of pulmonary complications after tricuspid valve replacement 14 months after pacemaker explantation. No recurrent infections were observed. CONCLUSIONS: Explantation of the complete pacemaker system has proved a reliable method to eradicate infection. Complications have been rare, except in patients in a critically ill state who undergo cardiopulmonary bypass.

Adult↗
PubMed1997

Comparative analysis of plasminogen activator inhibitor-1 expression in different types of atherosclerotic lesions in coronary arteries from human heart explants.

OBJECTIVES: Clinical manifestations of coronary heart disease result primarily from the progressive development of atherosclerotic plaques and subsequent thrombus formation: processes which may be accelerated by an enhanced expression of plasminogen activator inhibitor (PAI-1) in the vessel wall. In the present study, content and expression of PAI-1 were comparatively analyzed in human coronary arteries in relation to the presence and severity of atherosclerotic lesions. METHODS: Segments of coronary arteries obtained from heart explants (n = 15) were classified by the presence and types of atherosclerotic lesions. Antigen and activity levels of PAI-1 were determined in protein extracts of intimal and medial layers. In situ hybridization and immunohistochemical analyses were performed on serial sections of representative tissue specimens. RESULTS: Total PAI-1 antigen consistently increased from macroscopically normal areas (MNAs) to early lesions (ELs) and to maximal levels in fibrous (FPs) and calcified (CPs) plaques. No PAI activity was detected, although PAI-1 in its free form was present in all vascular specimens. Both free PAI-1 and PAI-1 complexed with plasminogen activators were significantly increased in extracts of advanced lesions. However, there was a 2-3 fold molar excess of free versus complexed PAI-1 in FPs and CPs. These findings suggest the presence of relevant amounts of PAI-1 in its substrate rather than in its inhibitor conformation in areas of advanced lesions. Compared with MNAs, PAI-1 mRNA was strongly expressed within the thickened intima of ELs. The highest PAI-1 expression was observed in FPs and CPs, being mainly localized in areas surrounding the necrotic cores in co-localization with infiltrating macrophages. CONCLUSIONS: PAI-1 content is consistently increased in relation to the severity of the lesions in atherosclerotic coronary arteries. The concomitant elevation of PAI-1 mRNA suggests that the PAI-1 increase in regulated by local synthesis in the areas of atherosclerotic lesions.

Antigens↗
PubMed1997

Cardiopulmonary effects of enoximone or dobutamine and nitroglycerin on mitral valve regurgitation and pulmonary venous hypertension.

OBJECTIVE: To compare the cardiovascular and pulmonary effects of the phosphodiesterase III inhibitor enoximone (EN) or a combination of dobutamine (DOB) and nitroglycerin (NTG) before and after mitral valve repair or replacement. DESIGN: Prospective, randomized, controlled clinical study. SETTING: University hospital. PARTICIPANTS: Twenty patients with mitral regurgitation and pulmonary venous hypertension scheduled for elective mitral valve surgery. INTERVENTIONS: Patients fulfilling the inclusion criteria of the study were randomly allocated into a group treated with EN (group 1, n = 10) or DOB and NTG (group 2, n = 10). A cardiopulmonary status was obtained after induction of anesthesia and mechanical ventilation during stable hemodynamic conditions (control). Then the patients received either EN (bolus dose 1.0 mg/kg followed by a continuous infusion of 10 micrograms/kg/min) or DOB (8.0 micrograms/kg/min) and NTG (1.0 microgram/kg/min) according to the randomization. After a period of 20 minutes, all parameters were measured again. The study drugs were stopped, and cardiac surgery was performed. Infusions of EN (without additional loading dose) or DOB and NTG were started again in the above-described doses 10 minutes before separation from cardiopulmonary bypass (CPB). Respiratory and hemodynamic measurements were made 20 minutes after weaning from CPB and 60 minutes after admission of the patient to the intensive care unit. MEASUREMENTS AND MAIN RESULTS: Both groups were comparable regarding preoperative and control data. Before mitral valve surgery, cardiac output (CO) and heart rate (HR) increased by 46% (p < 0.05) and 31% (p < 0.01) during infusion of EN with minor changes of mean systemic arterial pressure (PSA) and gas exchange. Mean pulmonary arterial pressure (PPA) decreased from 32 +/- 11 mmHg to 23 +/- 11 mmHg (p < 0.05). Similar alterations were observed in group 2 (delta CO + 26%, p < 0.05, delta HR + 39%, p < 0.01); however, PPA and calculated pulmonary vascular resistance remained unchanged. After separation from CPB, EN and DOB-NTG achieved comparable effects on CO, HR, and PSA, but PPA was significantly lower in group 1. In addition, venous admixture and alveolo-arterial oxygen tension gradient were lower in EN-treated patients. CONCLUSION: Enoximone or DOB and NTG have comparable effects on CO, PSA, and HR in mitral regurgitation and pulmonary hypertension, but EN is more effective in reducing PPA without deterioration of gas exchange.

Adrenergic beta-Agonists↗