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Biomedical subjects

D Loisance

Publications and source records attributed to D Loisance.

At least 55 records · Page 3Linked to original sources
PubMed1998

Intermediate follow up of the TEKNA bileaflet valve.

BACKGROUND AND AIM OF THE STUDY: The study aim was to collect intermediate clinical data on the TEKNA bileaflet valve. METHODS: This nine-center clinical study involved 884 patients implanted between June 1990 and October 1993. The population consisted of 522 (59.0%) males and 362 (41.0%) females. Mean age at implant was 59.1 +/- 11.8 years (range: 14.7 to 88.4 years). Indication for valve replacement was dependent on the position: stenosis was the predominant reason in the aortic position; regurgitation was more pronounced for the mitral position. A total of 261 (29.5%) patients underwent concomitant procedures. Mean follow up is 2.7 +/- 1.2 years; total follow up is 2386.1 patient-years (pt-yr). RESULTS: Total operative (< or = 30 days postoperative) mortality rate was 3.7%; seven patients (0.8%) died due to valve-related causes. Total postoperative (> 30 days postoperative) mortality rate was 2.5%/pt-yr and included a valve-related mortality rate of 1.1%/pt-yr. The following valve-related complication rates (%/pt-yr) were reported for the long-term postoperative period: thromboembolism 0.6; valve thrombosis 0.3; bleeding events 1.5; non-structural deterioration 0.6; and endocarditis 0.4. No structural valve deterioration was reported. Actuarial freedom at four years was: overall survival rate 86.9 +/- 1.4%; valve-related survival rate 94.7 +/- 1.0%; freedom from thromboembolism 96.8 +/- 0.9%; valve thrombosis 99.3 +/- 0.3%; endocarditis 98.5 +/- 0.5%; bleeding events 94.3 +/- 1.0%; and non-structural deterioration 98.2 +/- 0.6%. CONCLUSIONS: The data indicate that observed mortality is due mainly to non-valve-related disorders. Risk of thromboembolic and bleeding events was low (0.9%/pt-yr and 1.5%/pt-yr, respectively). We conclude that this valve is safe and efficacious for use.

Actuarial Analysis↗
PubMed1998

[Therapeutic strategy of the management of acute heart failure].

Acute cardiac failure should be approached clinically and paraclinically as an emergency and precipitation is not always what is required. Consequently, strict clinical and paraclinical strategy leads to decisive action to improve the prognosis. The authors describe the principles of management of acute cardiac failure. The different stages which are carried out simultaneously in clinical practice are discussed: physiopathological basis, clinical and paraclinical investigations, symptomatic and aetiological treatment. The description and indications of circulatory assistance are considered. This constitutes a major therapeutic advance of the last decade and has changed the treatment of the most severe clinical forms of acute cardiac failure.

Acute Disease↗
PubMed1997

Ventriculoarterial coupling and left ventricular efficiency in heart transplant recipients.

BACKGROUND: In heart transplants, left ventricular function may be impaired in the absence of rejection or graft atherosclerosis. Matching between left ventricle and arterial receptor, i.e., ventriculoarterial coupling, and left ventricular efficiency have never been studied. METHODS: Left ventricular pressure-volume loops and single beat analysis were used to determine effective arterial elastance (Ea) and the slope of the end-systolic pressure-volume relation (end-systolic elastance; Ees). Left ventricular efficiency was evaluated by determination of external work (EW), pressure-volume area (PVA), coronary blood flow (continuous thermodilution), and myocardial oxygen consumption (MVO2). Measurements were made at baseline in 11 control subjects and 9 heart transplant recipients (HTX) without rejection and were repeated after phenylephrine in the latter group. RESULTS: At baseline, Ees, Ees/Ea, and work efficiency (EW/PVA) were lower in HTX than in control subjects (2.51+/-0.87 vs. 3.70+/-1.15 mmHg/ml/m2, P<0.01; 0.96+/-0.21 vs. 1.47+/-0.31, P<0.001; and 0.53+/-0.08 vs. 0.59+/-0.09, P<0.01, respectively). Energy conversion efficiency (PVA/MVO2) and mechanical efficiency (EW/ MVO2) were higher in HTX (0.58+/-0.08 vs. 0.45+/-0.14, P<0.001; and 0.31+/-0.05 vs. 0.26+/-0.06, P<0.001, respectively). In HTX, phenylephrine infusion increased Ees, Ea, EW, PVA, and MVO2 without modifying Ees/Ea, EW/PVA, PVA/MVO2, and EW/MVO2. CONCLUSIONS: In heart transplants, (1) left ventricular contractility is moderately depressed; (2) elevation of energy conversion efficiency compensates for the decrease in work efficiency, allowing normal mechanical efficiency; and (3) alpha 1 adrenergic stimulation does not impair ventriculoarterial coupling and mechanical efficiency.

Adult↗
PubMed1997

[Indication of mechanical circulatory assistance].

Over the last decade, we have seen considerable progress both in medical treatment of acute and chronic heart failure and in circulatory assist systems, including the first used aorta counter-pulse system. More sophisticated systems have been developed with specific indications recognized by specialized teams. However, in the treatment of chronic heart failure, whether caused by idiopathic dilated cardiomyopathies or ischemic heart disease (frequently improved with coronary revascularization), the nature of the disease in patients hospitalized in intensive care units has greatly changed. There is a net tendency towards hospitalizing older patients who may no longer be reasonable candidates for transplantation. The option of circulatory assist is thus undoubtedly reasonable for these patients due to the lack of a sufficient number of donor organs.

Acute Disease↗
PubMed1997

[Wearable Baxter-Novacor mechanical ventricular assistance].

Progressive technological developments have permitted clinical use of the wearable Baxter-Novacor left ventricular assist system. The system allows total bypass of the left ventricular function, and recovery of and adequate circulation in patients in cardiogenic shock. Since the first clinical use, in March 1993, eight patients about to die have been supported with a cardiac transplantation. This experience suggests that an an acceptable answer to the problem of organ shortage is now available.

Adolescent↗
PubMed1997

Mechanical circulatory support towards the permanent implantation.

Experience on wearable LVAS Novacor support accumulated since the first implantation in March 1993, includes in November 1995, seven cases (six male, one female, mean age 34) of cardiogenic shock, unresponsive to optimal medical management referred for urgent transplantation. Post-implantation period was free of any major incident in all but one, allowing transplantation in five, on an elective basis, and prolongation of the waiting period, at home in two. This experience suggests that a major breakthrough in the technology of mechanical support has been achieved: patients awaiting transplantation can be discharged home, which is both the result and an contributing factor of a satisfactory quality of life. This improvement allows speculations on coming studies on permanent implantation of the wearable LVAS Novacor, as an alternative therapy to cardiac transplantation.

Adult↗
PubMed1997

External biodegradable supporting conduit protects endothelium in vein graft in arterial interposition.

The prevention of circumferential distension could reduce structural damage in arteriovenous grafts. We studied the effect of an external biodegradable supporting conduit on the endothelium and extracellular matrix in vein graft in a pig model. Cephalic vein control grafts (Group I) and jugular veins wrapped in a vicryl mesh tube (I.D. 4 mm) (Group II) were implanted into autologous carotid arteries (n = 14). The grafts were explanted after 1 and 24 hours and at 1 and 3 weeks and evaluated by ELISA for endothelial DNA synthesis and by immunohistoenzymic assays for cells and extracellular matrix. In group I an initial loss of endothelial and smooth muscle cells along with elastin breakdown was followed by an impaired endothelial regeneration and significant graft wall thickening. The elastic tissue was replaced by collagen type I and chondroitin sulfate accumulations, which included a disarray of alpha-smooth muscle actin positive cells. The endothelium was preserved in group II. After 3 weeks the circumferential elastin layers were densified, distended and separated from the endothelium by a neointimal growth of irregular thickness. Biodegradable perivenous conduit minimized endothelial injury and allowed the partial preservation of elastin fibers and smooth muscle cells in the arteriovenous graft. It did not however, prevent myofibroblastic cell proliferation and triggered a macrophagic reaction.

Actins↗
PubMed1996

Sympathetic stimulation overrides flow-mediated endothelium-dependent epicardial coronary vasodilation in transplant patients.

BACKGROUND: Abnormal coronary vasomotor responses have been described in transplant patients. The aim of this study was to evaluate the graft epicardial vasomotor responses to different stimuli that increase coronary blood flow. METHODS AND RESULTS: Twelve heart transplant recipients with angiographically normal epicardial coronary arteries were compared 2.7 +/- 1.2 months after surgery with 6 control subjects. Coronary flow velocity was measured with a guidewire Doppler. Coronary diameter changes of the proximal and midportion of the left anterior descending coronary artery were assessed by quantitative coronary angiography during rapid atrial pacing, cold pressor test, supine exercise, and subselective infusion of papaverine and after intracoronary injection of linsidomine (SIN-1). Catecholamine plasmatic levels were determined at the different stages of the protocol. In 6 other transplant patients, a cold pressor test was performed before and after intracoronary infusion of phentolamine (10 micrograms.kg-1.min-1). Coronary flow velocity increased significantly in both groups during each phase of the protocol. In control subjects, dilation was observed in response to atrial pacing (8.7 +/- 7.6%; P < .05), CPT (8.8 +/- 2.3%; P < .01), exercise (14.5 +/- 9.4%; P < .001), and papaverine infusion (14.2 +/- 6.1%; P < .001) and after injection of SIN-1 (26.8 +/- 11.9%; P < .001). In transplant patients, similar dilation was observed during atrial pacing (8.2 +/- 8.3%; P < .05) and papaverine infusion (14.6 +/- 7.8%; P < .001) and after SIN-1 (25.8 +/- 10.8%; P < .001). CPT and exercise caused slight constriction (-3.5 +/- 4.5% and -2.7 +/- 10.5%, respectively; both P < .001 versus control subjects). Norepinephrine plasmatic levels increased in both groups during CPT and exercise. Slight constriction during the cold pressor test (-4.5 +/- 9.6%) changed to dilation (6.8 +/- 7.0%) after alpha-blockade with phentolamine (P < .001). CONCLUSIONS: These results show that flow-mediated, endothelium-dependent vasodilation is preserved early after trans-plantation. Sympathetic stimulation, which overrides the endothelium-dependent mechanism, can be related to hypersensitivity to catecholamines due to denervation.

Adrenergic alpha-Antagonists↗
PubMed1996

Increased serum nitrate concentration in cardiac transplant patients. A marker for acute allograft cellular rejection.

The purpose of the present study was to investigate whether nitrate serum level, reflecting total body production of nitric oxide in vivo, could serve as a noninvasive marker for acute human cardiac rejection. Serum nitrate concentration was determined by an enzymatic method. During routine right ventricular endomyocardial biopsies in 59 recipients, 145 tissue samples were obtained. Two groups of biopsy specimen were considered on the basis of posttransplant delay: group 1, < or = 90 days (n=47; 12-90 days); and group 2, >90 days (n=98; 3-81 months). All patients had normal ventricular systolic function on the day of biopsy and none had evidence of infection. Rejection grade correlated closely with serum nitrate concentration (P<0.001). In both groups, nitrate serum concentrations differed significantly (P<0.001) among cases without rejection, those with mild ongoing rejection (grade 1A/1B), and those with focal or diffuse aggressive infiltrates (grade 2 or higher). A cutoff value of 20 micromol/L, was determined that was positively predictive for grade 2 or higher rejection in 62% cases of early episodes of rejection and in 68% cases of late rejection. Conversely, a serum nitrate level below 20 micromol/L was negatively predictive in 97% and 94% of early and late cases, respectively. We conclude that the acute rejection process of the human transplanted heart is accompanied by a significant increase in serum nitrate level, reflecting increased nitric oxide production during the immune response. Because of its high negative predictive value, irrespective of the posttransplantation delay, nitrate serum determination may have clinical utility in the noninvasive monitoring of the cardiac transplant patient and could also add important information to endomyocardial biopsy analysis for treatment decision making.

Graft Rejection↗
PubMed1996

[Wearable mechanical ventricular support].

Progressive technological developments have permitted clinical use of the wearable Baxter-Novacor left ventricular assist system. The system allows total bypass of the left ventricular function, and recovery of an adequate circulation in patients about in cardiogenic shock. Since the first clinical use, in March 1993, six patients about to die have been supported with a cardiac transplantation. This experience suggests that an acceptable answer to the problem of organ shortage is non available.

Assisted Circulation↗
PubMed1996

Immunoglobulins and complement deposits in mitroflow pericardial bioprosthetic heart valves--a contributing factor to structural deterioration.

BACKGROUND AND AIMS OF THE STUDY: Twenty-two bovine pericardial Mitroflow prostheses were explanted after 73-114 months from either the aortic or mitral position because of clinical failure. All the samples exhibited cuspal tears and foldings. Eleven prostheses were calcified. The aim was to study biological factors involved in the structural deterioration. METHODS: Histologic and biochemical assays were carried out on the deteriorated, non-calcified and on the calcified leaflets. Labelled antibodies and avidinbiotinyilated peroxydase complex were used to detect plasma proteins and cells in the cusps. RESULTS: Fibrin covered the cuspal surface and accumulated in the deep disrupted layers (19/22). Scattered fibronectin filaments were seen across the transversal sections (20/22). IgG, complement fractions C1q, C3, C4 (20/22), macrophages (sixteen) and cells containing granulocyte elastase were revealed in the altered matrix. These plasma proteins and cells were detected in the disintegrated matrix of non-calcified and of calcified leaflets. IgA was present in amorphous cuspal thickenings with lipid infiltration (12/22). Western blot analysis of the PBS-2% SDS extracts from the leaflets indicated the breakdown of fibrinogen/fibrin, fibronectin and of complement proteins C3, C4 and C5. CONCLUSIONS: The results suggest the activation of the complement by the non-hemocompatible, chemically processed bovine pericardium. The bioactive peptides generated in this process can stimulate monocyte migration, phagocytosis and exocytosis of proteases able to degrade the glutaraldehyde cross-linked macromolecular matrix. These biological factors can contribute, together with the mechanical stress, to the structural deterioration of the bioprosthesis.

Aged↗
PubMed1996

[Baxter-Novacor type implanted ventricular device: a possible alternative to transplantation].

After nearly 25 years of continuous technological development, the therapeutic arsenal for treating severe cardiac failure has been reinforced by the addition of a new weapon: a mechanical bridge whilst waiting for emergency cardiac transplantation for patients in cardiogenic shock and an alternative to transplantation in certain categories of chronic disease. The author describes the system and the results in the indication of a bridge to transplantation and the problems posed by the indication of chronic cardiac failure are discussed.

Assisted Circulation↗
PubMed1996

[Mechanical circulatory assistance using the Novacor implanted device. A postoperative follow-up].

The postoperative follow-up of 8 patients on the waiting list for cardiac transplantation, with implanted left ventricular assist devices of the Novacor type, was marked by right ventricular failure in the first week, controlled by positive inotropic agents and the maintenance of high right ventricular preload. The outcome later on showed that an ambulatory life was possible for 6 of the 8 patients, allowing the wait for cardiac transplantation under excellent conditions. Three major complications were observed: a case of aspergillosis endocarditis, one vertebrobasilar cerebrovascular accident and one low output state by progressive degradation of right ventricular function: after a period of circulatory assistance of 52 to 201 days. 6 out of the 8 patients underwent cardiac transplantation, 5 of which were successful.

Adolescent↗
PubMed1995

Coronary artery response to cold-pressor test is impaired early after operation in heart transplant recipients.

OBJECTIVES: The aim of the present study was to evaluate the coronary vasomotor response to the cold-pressor test within 3 months after heart transplantation. BACKGROUND: Normal epicardial coronary arteries dilate in response to sympathetic stimulation evoked by the cold-pressor test. In transplant recipients, abnormal coronary vasomotion has been described shortly after operation. METHODS: Fourteen heart transplant recipients were compared 52 +/- 15 days (mean +/- SD) after operation with 10 control subjects. All had angiographically normal epicardial coronary arteries. Coronary blood flow velocity was measured with a Doppler catheter placed in the proximal left anterior descending coronary artery. Four segments in each patient were analyzed by quantitative coronary angiography to assess the diameter changes during the cold-pressor test and after intracoronary injection of isosorbide dinitrate. RESULTS: Coronary flow velocity increased similarly during the cold-pressor test in control subjects and in transplant recipients, from 7.5 +/- 2.3 to 11.0 +/- 3.9 cm/s and from 10.3 +/- 3.2 to 13.7 +/- 4.8 cm/s (both p < 0.01). In control subjects, 39 of 40 segments analyzed dilated during the cold-pressor test. In transplant recipients, 48 of 56 segments analyzed did not change or constricted. The mean epicardial coronary diameter increased significantly during the cold-pressor test in control subjects (+13 +/- 6%, p < 0.001), whereas it did not change significantly in transplant recipients (-2 +/- 9%, p = NS). In transplant recipients, isosorbide dinitrate elicited coronary vasodilation similar to that in control subjects. CONCLUSIONS: These data indicate that in human transplanted denervated hearts, coronary vasodilation in response to sympathetic stimulation by cold exposure is impaired shortly after operation.

Adult↗
PubMed1995

Inhibition of hydroxyl radical production by lactobionate, adenine, and tempol.

Superoxide and hydroxyl free radicals are strongly implicated in the deleterious effects of reperfusion of grafted organs. Iron ions are critical in the Fenton-like reaction that generates oxygen-free radicals from H2O2. Using the ADP/Fe2+/H2O2 .OH-generating system, we demonstrated that components of an organ-preservation solution (Henri Mondor solution): sodium lactobionate, adenine, and a nitroxide radical: 4-hydroxy-2,2,6,6-tetramethylpiperidine-n-oxyl (TEMPOL), showed unexpected inhibition properties on the production of hydroxyl radicals by complexation of Fe2+ for lactobionate and nitroxide or Fe3+ for adenine. This inhibition was 75.5% at 12 mM lactobionate. Moreover, a complete inhibition was observed at 50 mM. At 0.25 mM adenine, the reduction was 14.8% (maximum effect: 34.1%). Henri Mondor solution, at an identical adenine and lactobionate concentration, inhibited the radical production by 91.5%, indicating an additive effect. Nitroxide totally inhibited .OH production by the ADP/Fe2+/H2O2 system (maximum effect: 95.6%) and partially the production by an O2.- generating system (maximum effect: 74.8%). Thus, the association of these three components in preservation solutions would be an original method to limit the reperfusion injury observed in isolated ischemic organs.

Adenine↗
PubMed1995

Effects of cryopreservation on the proliferation and anticoagulant activity of human saphenous vein endothelial cells.

Human saphenous veins were cryopreserved in 4% human albumin and 10% dimethyl sulfoxide. The effect of cryopreservation on endothelial cells was studied in terms of the anticoagulant activity of thrombomodulin and in terms of cell proliferation. After storage for 2 weeks at -150 degrees C, 0.45 +/- 0.07 x 10(5) endothelial cells/cm2 were detected in cryopreserved veins and 1.03 +/- 0.04 x 10(5) endothelial cells/cm2 in fresh veins (p < 0.01). The thrombin-catalyzed activation of protein C decreased after cryopreservation, indicating altered thrombomodulin activity in the endothelial cells. On a cell number basis, the release of soluble thrombomodulin was three times higher from the cryopreserved endothelium than from the fresh endothelium (p < 0.05). The amount of spontaneous release of von Willebrand factor from the endothelial surface was not significantly different between fresh and cryopreserved veins. Endothelial cells were cultured from fresh veins and from their cryopreserved counterparts. On plating of endothelial cells in primary culture, the number of adhered cells was 0.9 +/- 0.09 x 10(3) cells/cm2 from fresh veins and 0.25 +/- 0.03 x 10(3) cells/cm2 from cryopreserved veins (p < 0.01). The positive immunohistochemical stain for von Willebrand factor indicated that the endothelial cell character was maintained after cryopreservation. The endothelial desquamation with loss of anticoagulant function and the slow proliferation of surviving cells in vitro suggest an impaired endothelial healing in vivo. The loss of anticoagulant activity complicates the problems of the exposure of thrombogenic subendothelial matrix to blood in implanted cryopreserved veins.

Blood Coagulation↗