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Biomedical subjects

J Ristich

Publications and source records attributed to J Ristich.

7 recordsLinked to original sources
PubMed2001

Cardiopulmonary transplantation for congenital heart disease in the adult.

BACKGROUND: Patients surviving into adulthood with congenital heart disease (CHD) often succumb to progressive cardiopulmonary dysfunction. For these patients transplantation is often considered. METHODS: We performed a retrospective review of 69 adults (age >18 years) with CHD transplanted between 1984 and 1999. RESULTS: We evaluated 31 heart-lung (HLTxp), 30 lung (LTxp), and 8 heart (HTxp) transplants performed in 22 men and 47 women with CHD. Mean age was 37 +/- 10 years with a mean follow-up of 3.1 +/- 3.5 years. A concomitant cardiovascular procedure was performed in 1 HLTxp, 23 LTxp, and 2 HTxp. Early mortality (>30 days) was 26% (8/31) for HLTxp, mostly due to bleeding. Early LTxp mortality was 23% (7/30), largely due to graft failure. One and 3-year survival was similar in adults transplanted for CHD and adults transplanted for other disease. Early mortality among HTxp recipients was 50% (4/8) from rejection or technical complications. Survival for patients undergoing HLTxp versus LTxp with cardiac repair was similar. When examined by era, the survival of patients transplanted for CHD between 1992 and 1999 was greater than that of patients transplanted between 1984 and 1991. CONCLUSIONS: Adults undergoing HLTxp and LTxp for CHD can expect survival comparable to that of non-CHD adults. In the presence of a reparable cardiac lesion, LTxp with cardiovascular repair for CHD is an attractive option, optimizing organ allocation. Specific technical concerns are discussed. Survival of adults undergoing cardiopulmonary transplantation for CHD has improved over time.

Adult↗
PubMed2000

Cocaine activates platelets and increases the formation of circulating platelet containing microaggregates in humans.

OBJECTIVE: To determine whether there is evidence of platelet activation following in vivo cocaine administration in humans, as cocaine abuse is associated with myocardial infarction and stroke, and platelet activation leading to thrombosis is a possible mechanism. SETTING: University hospital. DESIGN AND SUBJECTS: Following a randomised, double blind crossover design, 14 healthy volunteers were studied twice, receiving cocaine (2 mg/kg intranasally) once and placebo once. Flow cytometric analysis of P-selectin expression (an alpha granule membrane protein found on the surface of activated platelets), quantification of the platelet specific proteins platelet factor 4 and beta thromboglobulin, and measurement of platelet containing microaggregate and platelet microparticle (fragment) formation were used to assess platelet activation. Circulating von Willebrand factor antigen (vWF) was measured to evaluate a possible role of endothelial stimulation concurrent with platelet activation. RESULTS: There was an increase in both platelet factor 4 (mean (SD), 16 (7) to 39 (22) IU/ml, p = 0. 04) and beta thromboglobulin (70 (20) to 98 (26) IU/ml, p < 0.01) at 120 minutes following cocaine administration. Platelet containing microaggregate formation was increased at 40 minutes (from 47 (3.2)% to 54 (2.0)%, p < 0.001) and 80 minutes (55 (2.5)%, p = 0.04). Bleeding time decreased following cocaine from 10 (1) to 9 (1) minutes (p = 0.07). No changes in any of the measured variables were noted following placebo administration. CONCLUSIONS: Cocaine exposure causes platelet activation, alpha granule release, and platelet containing microaggregate formation. These data support the view that cocaine, even at the relatively low doses commonly self administered by occasional abusers, may promote thrombosis and predispose healthy individuals to ischaemic events. Platelet inhibitors should be considered early in any patient with suspected cocaine related ischaemia.

Adult↗
PubMed1999

Measurement of hemostatic indexes in conjunction with transcranial doppler sonography in patients with ventricular assist devices.

BACKGROUND AND PURPOSE: Clinical thromboembolism (TE) remains an impediment to the chronic application of ventricular assist devices (VADs). Microembolic signals (MES) have been detected by transcranial Doppler ultrasound (TCD) in patients with VADs, although their origin and relation to TE remain undefined. We have investigated the hypothesis that hemostatic alterations are related to MES and that MES are associated with TE in a group of 27 VAD patients. METHODS: Indexes of coagulation, fibrinolysis, and cellular activation and aggregation were measured before and during the VAD implantation period in conjunction with TCD. Groups were defined on the basis of presence of MES, degree of MES showering, and incidence of TE. RESULTS: MES were observed in 67 (58%) of 115 of individual postoperative TCD measurements and in 21 (78%) of 27 patients. Of patients with TE, 10 (83%) of 12 had detectable MES compared with 11 (73%) of 15 patients without TE (P=0.66). MES were significantly associated with elevated thrombin generation during the implantation period, as reflected by plasma prothrombin fragment F1.2. Elevations in indexes of coagulation, platelet activation, and fibrinolysis relative to normal control subjects were found for patients with VADs with and without detected MES. CONCLUSIONS: Although no significant relation between MES and TE in VAD patients was found, the data support the hypothesis that MES are related to increased hemostatic activity in this patient group despite aggressive anticoagulant therapy.

Adolescent↗
PubMed1998

Monocyte tissue factor expression and ongoing complement generation in ventricular assist device patients.

BACKGROUND: Ongoing complement activation in patients with a ventricular assist device may contribute to observed hemostatic abnormalities and cellular aggregation by mediating leukocyte and platelet activation, formation of leukocyte-platelet conjugates, and the tissue factor pathway of coagulation. METHODS: Blood from 30 patients was collected before ventricular assist device implantation and during the implantation period. Plasma levels of thrombin-antithrombin III complexes, C3a, and SC5b-9 were measured by commercial enzyme-linked immunosorbent assay. Flow cytometry was used to measure circulating monocyte tissue factor expression and circulating monocyteplatelet and granulocyte-platelet conjugates. RESULTS: Thrombin-antithrombin III complex level and monocyte tissue factor expression peaked in the early postoperative period, with maxima occurring on postoperative days 5 and 3, respectively. Levels of C3a and SC5b-9 remained dramatically elevated over normal values for the duration of the study (6 and 5 times upper normal, respectively). Levels of monocyte-platelet conjugates were normal before implantation, decreased during the first 4 postoperative days, and then increased and remained elevated. Levels of granulocyte-platelet conjugates were elevated over the normal range before implantation and remained elevated from postoperative days 3 to 21. A positive correlation was found between levels of SC5b-9 and granulocyte-platelet conjugates (Spearman R=0.66; p < 0.001), and between levels of C3a and thrombin-antithrombin III complex (Spearman R=0.13; p=0.021). CONCLUSIONS: The data suggest a model in which complement mediates formation of leukocyte-platelet aggregates and may indirectly contribute to thrombin generation through monocyte tissue factor expression.

Adult↗
PubMed1996

Comparative in vitro analysis of topical hemostatic agents.

Hemostatic agents are broadly utilized across the surgical specialties. While specific characteristics desirable for individual applications may vary, these agents generally are expected to aid the patient's coagulation system in the rapid development of an occlusive clot. Six commonly utilized hemostatic agents were quantitatively compared in terms of their ability to mediate platelet aggregation, deposition and activation, and initiate gross clot formation in a series of in vitro tests. Three types of collagen sponges (Actifoam, Helistat, Instat), microfibrillar collagen (Avitene), a gelatin sponge (Gelfoam), and oxidized regenerated cellulose (Surgicel) were studied. Platelet aggregation: Citrated platelet rich plasma (PRP) was contacted with hemostatic agents both with and without thrombin in a stirred cuvette and the platelet count was measured over 5 min. Platelet deposition: To approximate arterial wounds, PRP was perfused in a controlled manner through hemostatic agents, and the effluent platelet count was measured over time. Platelet activation: ATP secretion from PRP contacted with hemostatic agents in a stirred cuvette was measured at 1 and 5 min. Clot formation: The clotting time of nonanticoagulated whole blood contacted with the hemostatic agents was measured. Materials which depleted platelets most rapidly and effectively in the perfusion system (Avitene, Helistat, and Actifoam) were also the most effective inducers of platelet aggregation and secretion. Clot formation (likely to be platelet dependent) was also more rapid in this group. An overall activity ranking combined the relative performance of each hemostatic agent on the various tests: Actifoam approximately Avitene > Helistat >> Gelfoam > Instat > Surgicel. The activity ranking generally reflects the materials used in these agents (collagen > gelatin > oxidized regenerated cellulose), as well as their processing (chemical crosslinking in collagen sponges may lower activity). Such in vitro assessment of the relative platelet and coagulation activities of hemostatic agents might serve as a useful screening tool before investigating properties which require more expensive animal or clinical testing.

Adenosine Triphosphate↗