Biomedical subjects

J L Navia

Publications and source records attributed to J L Navia.

10 recordsLinked to original sources

PubMed2005

Early and late rejection and HLA sensitization at the time of heart transplantation in patients bridged with left ventricular assist devices.

Over the years, the frequency of heart transplant candidates with HLA sensitization has increased as a result of the number of patients bridged to transplant using left ventricular assist devices (LVAD). Here we have examined 119 patients who were bridged to transplant with LVAD for a relationship between HLA antibodies and early (30 days) and late (2 years or more) rejection, as evidenced by endomyocardial biopsies. Both cytotoxic panel-reactive antibody reactions against a panel of T lymphocytes (T-PRA) and the percentage of transplants that occurred across a positive class I flow cross-match were examined. Biopsies were scored using ISHLT criteria. At 30 days, patients who had a biopsy grade of 0 had a mean T-PRA at transplant of 2.2%, while the mean PRAs of the other biopsy grades were significantly higher (P < .001). A similar pattern was seen with the highest biopsy results at 2 years or later (P < .001). None of the patients who had a grade 0 biopsy at 30 days posttransplant had a positive flow cytometry class I cross-match (P = .02), although the same pattern did not occur later due to a small number of patients (n = 3) who had negative biopsies. Thus, when biopsy results were examined early or late posttransplant, patients with negative biopsy results tended to have less HLA sensitization. While the methods of HLA sensitization involve humoral responses, more aggressive immunosuppression might be warranted to attempt to reduce cellular rejection posttransplant if HLA class I antibodies are present at the time of transplant.

Flow Cytometry↗

PubMed2004

Curative surgery for atrial fibrillation. Current status and minimally invasive approaches.

Atrial fibrillation (AF) is the most common disorder of heart rhythm. Affecting 2.2 million Americans and millions more worldwide, AF is a dangerous and costly epidemic. AF is associated with an increased risk of stroke, premature death, and billions of dollars in health care expenditures. Traditional treatments of AF, which include medications aimed at rate or rhythm control, have been disappointing, leaving most patients in AF and failing to eliminate the risk of stroke. In contrast, advances in surgical and catheter-based therapies offer the chance to cure AF. With more than a decade of experience, surgical treatment AF is the most effective means of curing this arrhythmia. The classic Maze procedure eliminates AF in more than 90% of patients. A complex but safe operation, the Maze procedure is applied by relatively few surgeons. Recently, however, there has been a resurgence of interest in surgical treatment of AF. Advances in the understanding of the pathogenesis of AF and development of new ablation technologies enable surgeons to perform pulmonary vein ablation and create linear left atrial lesions rapidly and safely. Such procedures, which are generally applied to patients with AF and valvular heart disease, add 15 minutes to operative time and cure AF in approximately 80% of patients. New ablation technologies have been adapted to enable thoracoscopic and minimally invasive surgical AF ablation in patients with isolated AF, extending the possibility of cure to large numbers of patients.

Aged↗

PubMed1999

A new method of myocardial revascularization with the radial artery.

We present a new method of myocardial revascularization. The radial artery is used in combination with the left internal mammary artery, thereby providing three distal end-to-side anastomoses to the left anterior descending coronary artery and other sites as determined by the coronary artery lesions. Arterial conduits form an anastomotic network between the left internal mammary artery and the radial artery in a horseshoe pattern. Three coronary arteries are revascularized by two arterial conduits in the left coronary system.

Anastomosis, Surgical↗

PubMed1998

Minimally invasive valve operations.

BACKGROUND: To reduce the morbidity from valvular heart operations, a right parasternal approach was introduced. We report our initial experience with the procedure. METHODS: From January 1996 through July 1996, 115 patients underwent primary isolated valve procedures. One hundred (85%) patients underwent the operation through a right parasternal incision. RESULTS: There was one hospital death secondary to a stroke on the fifth postoperative day. Three patients (two with aortic valve operations and one having a mitral valve procedure) required conversion to sternotomy. Mean aortic occlusion time was 71 minutes; mean cardiopulmonary bypass time was 93 minutes. Mean stay in the intensive care unit was 27 hours and mean hospital postoperative stay was 5.7 days. Seventy-seven percent of the patients did not receive blood transfusions. Comparison with median sternotomy demonstrated a reduction in both postoperative length of stay and direct hospital costs. CONCLUSIONS: We conclude that this minimally invasive approach is safe for a variety of valve procedures and is effective in reducing surgical trauma and cost.

Adult↗

PubMed1997

Intraoperative echocardiography is indicated in high-risk coronary artery bypass grafting.

BACKGROUND: Intraoperative echocardiography is a valuable monitoring and diagnostic technology used in cardiac surgery. This reports our clinical study of the usefulness of intraoperative echocardiography to both surgeons and anesthesiologists for high-risk coronary artery bypass grafting. METHODS: From March to November 1995, 82 consecutive high-risk patients undergoing coronary artery bypass grafting were studied in a four-stage protocol to determine the efficacy of intraoperative echocardiography in management planning. Alterations in surgical and anesthetic/hemodynamic management initiated by intraoperative echocardiography findings were documented in addition to perioperative morbidity and mortality. RESULTS: Intraoperative echocardiography initiated at least one major surgical management alteration in 27 patients (33%) and at least one major anesthetic/hemodynamic change in 42 (51%). Mortality and the rate of myocardial infarction in this consecutive high-risk study population using intraoperative echocardiography and in a similar group of patients without the use of intraoperative echocardiography was 1.2% versus 3.8% (not significant) and 1.2% versus 3.5% (not significant), respectively. CONCLUSIONS: We conclude that when all of the isolated diagnostic and monitoring applications of perioperative echocardiography are routinely and systematically performed together, it is a safe and viable tool that significantly affects the decision-making process in the intraoperative care of high-risk patients undergoing primary isolated coronary artery bypass grafting and may contribute to the optimal care of these patients.

Aged↗

PubMed1997

Third coronary artery bypass operations: risks and costs.

BACKGROUND: Third coronary artery bypass operations are technically difficult and are associated with increased risk. METHODS: We reviewed the cases of 469 patients who had undergone a third isolated coronary artery bypass operation and used univariate and multivariate testing to examine the effect of preoperative and operative variables on outcome and costs. RESULTS: The in-hospital mortality was 7.0% (33 patients). Advanced age and severe symptoms were found to increase risk (both p < 0.05): the mortality was 14% (n = 74) in patients 70 years old or older who had severe symptoms. However, the overall mortality for 1993 through 1995 was 4.3% (5/117) and only one death (1.3%) occurred among the 79 patients who were less than 70 years old. The late survival rate was 94%, 84%, and 66% at 1, 5, and 10 postoperative years, respectively, and predictors of decreased late survival were advanced age, abnormal left ventricular function, and diabetes (all p < 0.05). Again, age of 70 years or more was a predictor of a poor outcome. Only 52% of patients in that subgroup (including both early and late mortality) were alive 5 years after operation. Analysis of direct hospital costs showed that the mean costs of third coronary artery bypass operations were 21% higher than the mean costs of primary operations but that the elevation in the mean costs for third operations was related to very high costs in 4 patients. Sex was found to influence the cost of both primary and third operations (increased cost for women). CONCLUSIONS: Unfavorable outcomes after third coronary artery bypass operations have been associated with preoperatively definable variables, particularly age of 70 years or more. The in-hospital mortality in patients younger than 70 was low, and long-term survival in this group has been favorable. The increased hospital costs associated with third operations are related to high costs in only a few patients and have been unpredictable.

Age Factors↗

PubMed1996

Minimally invasive mitral valve operations.

A technique for mitral valve operations is described in which exposure is performed through a small right parasternal incision. Via a transseptal approach, excellent exposure to the mitral valve is obtained, allowing surgical correction of the diseased valve.

Cardiopulmonary Bypass↗

PubMed1988

Synthesis of a close analog of the repeating unit of the antifreeze glycoproteins of polar fish.

The protected glycopeptide N-(benzyloxycarbonyl)-L-alanyl-[O-(2,3,4,6-tetra-O-benzoyl-beta-D- galactopyranosyl)-(1----3)-O-(2,4,6-tri-O-benzyl-alpha-D-galactopyranosy l)- (1----3)]-L-threonyl-L-alanine 2,2,2-trichloroethyl ester was made by coupling the respective disaccharide and tripeptide blocks. The disaccharide block was generated by coupling tetra-O-benzoyl-alpha-D-galactopyranosyl bromide to allyl 2,4,6-tri-O-benzyl-alpha-D-galactopyranoside and converting the product into O-(2,3,4,6-tetra-O-benzoyl-beta-D-galactopyranosyl)-(1----3)-2,4,6-tri-O -benzyl - alpha-D-galactopyranosyl chloride via the 1-propenyl glycoside and the free (1-OH) sugar. Alternatively, the 1-propenyl intermediate was obtained directly by using 1-propenyl 2,4,6-tri-O-benzyl-alpha-D-galactopyranoside as the acceptor in the initial coupling reaction. An efficient 3-step synthesis of 10 was accomplished by the dibutyltin oxide-assisted, selective crotylation of allyl alpha-D-galactopyranoside at O-3, followed by benzylation and treatment of the product with potassium tert-butoxide. The N-benzyloxycarbonyl (Z) and N-tert-butoxycarbonyl (Boc) 2,2,2-trichloroethyl esters of Thr-Ala and Ala-Thr-Ala were formed by sequential coupling. The silver triflate-promoted glycosylation of the Z-protected dipeptide and tripeptide by 2,3,4,6-tetra-O-benzyl-alpha-D-galactopyranosyl chloride, and of the tripeptide by 6, proceeded with excellent alpha-stereoselectivity. From the disaccharide tripeptide 21, the carboxyl-deprotected and fully deprotected derivatives were prepared.

Animals↗

PubMed1986

The assembly of oligosaccharides from "standardized intermediates": beta-(1----3)-linked oligomers of D-galactose.

Several 2-O-benzoyl-4,6-di-O-benzyl-3-O-R-alpha-D-galactopyranosyl chlorides, designed as general precursors of beta-linked, interior D-galactopyranosyl residues in oligosaccharides, were tested in a sequential synthesis of the galactotriose beta-D-Galp-(1----3)-beta-D-Galp-(1----3)-D-Gal (19). The chlorides having R = tetrahydro-2-pyranyl and tert-butyldimethylsilyl gave excellent results, whereas those having R = 3-benzoylpropionyl and chloroacetyl were unsatisfactory. An activated disaccharide block (17), having R = 2,3-di-O-benzoyl-4,6-di-O-benzyl-beta-D-galactopyranosyl, was also prepared and tested as a glycosyl donor. The coupling of 17 to 1-propenyl 2-O-benzoyl-4,6-di-O-benzyl-alpha-D-galactopyranoside (14), in the molar ratio 1.13:1, gave 64% of a trisaccharide derivative (18) that could be converted into 19. This latter synthesis of 19 is efficient because all three galactose units are derived from 14 or its immediate precursor.

Carbohydrate Conformation↗

PubMed1983

Assay of N-acetylheparosan deacetylase with a capsular polysaccharide from Escherichia coli K5 as substrate.

A new substrate for the deacetylase which catalyzes the removal of the N-acetyl groups from N-acetylheparosan in the course of heparin biosynthesis has been prepared. The capsular polysaccharide from Escherichia coli 010:K5:H4, which is structurally identical to N-acetylheparosan, was partially N-deacetylated by hydrazinolysis and was then radioactively labeled by N-acetylation with [3H]acetic anhydride. Upon incubation of the labeled polysaccharide with microsomes from the Furth mastocytoma, [3H]acetyl groups were released, demonstrating that the bacterial polysaccharide was a substrate for the N-deacetylase. Reaction conditions were established which permitted the quantitative assay of N-deacetylase activity; a Km of 74 mg polysaccharide/liter was determined, which corresponds to 2.1 X 10(-4) M, expressed as concentration of uronic acid; Vmax was 3.4 nmol/mg protein/liter. In confirmation of previous results, it was observed (a) that the reaction was stimulated by 3'-phosphoadenylylsulfate (up to a maximum of 45% at a concentration of 0.5 mM), suggesting that N-sulfation occurred which facilitated continued action of the N-deacetylase, and (b) that NaCl and KCl inhibited the enzyme, with 50% reduction of activity at a concentration of 25 mM. In the course of this work, a simple, single-vial assay procedure was used. Released [3H]acetate was extracted from the acidified reaction mixture with a toluene- or xylene-based scintillation fluid containing 10% isoamyl alcohol and measured directly by scintillation spectrometry.

Amidohydrolases↗