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Biomedical subjects

D B Hood

Publications and source records attributed to D B Hood.

32 records · Page 2Linked to original sources
PubMed1996

Prevalence and distribution of calf vein thrombosis in patients with symptomatic deep venous thrombosis: a color-flow duplex study.

PURPOSE: This retrospective study was performed to identify the patterns of calf vein thrombosis in patients in whom deep vein thrombosis (DVT) was suspected and to better define the role of color-flow duplex scanning (CDS) in the evaluation of this patient population. METHODS: Over a recent 9-month period, we reviewed the vascular laboratory charts of 540 symptomatic patients (696 limbs) who underwent CDS for clinically suspected acute DVT. Patients who had a previous episode of DVT were excluded. RESULTS: CDS satisfactorily visualized all three paired calf veins in 655 of the limbs (94%). Inadequate scans (n = 41) were attributed to edema in 29, excessive calf size in eight, and anatomic inaccessibility in four. Peroneal veins were the most difficult to visualize (n = 29), followed by posterior tibial (n = 10) and anterior tibial (n = 9) veins. CDS identified acute DVT in 159 of 655 limbs (24%) that had adequate scans. Calf vein thrombi were detected in 110 of the 655 limbs (17%) and in 69% of the 159 limbs with DVT. Clots were confined to the calf veins in 53 limbs with DVT (33%). Isolated calf vein thrombi were found in 45% of outpatient limbs and in 27% of inpatient limbs with DVT. The peroneal (81%) and posterior tibial veins (69%) were more frequently involved (p < 0.001) than the anterior tibial veins (21%). In limbs with calf DVT, the prevalence of thrombosis isolated to the peroneal and posterior tibial veins was similar (37% and 25%, respectively); no limb had an isolated anterior tibial DVT (p = 0.02). CONCLUSION: CDS is a reliable method for evaluating calf veins for DVT. Calf vein thrombosis is common in patients who have acute DVT and often occurs as an isolated finding. The peroneal and posterior tibial veins are involved in the majority of cases; thrombi occur much less frequently in the anterior tibial veins. We conclude that CDS should be the noninvasive method of choice for the initial evaluation of patients in whom DVT is suspected, and we recommend that calf veins should always be studied but that routine scanning of the anterior tibial veins may not be necessary.

Acute Disease↗
PubMed1996

Prospective evaluation of new duplex criteria to identify 70% internal carotid artery stenosis.

PURPOSE: Large multicenter trials (North American Symptomatic Carotid Endarterectomy Trial, European Carotid Surgery Trial) have documented the benefits of carotid endarterectomy for treating symptomatic patients with >or=70% stenosis of the internal carotid artery. Although color-flow duplex scanning has become the preferred method for noninvasive assessment of internal carotid artery disease, no criteria have been generally accepted to identify this subset of patients. We previously reported a retrospective series to establish such criteria. This study details our results when these criteria were applied prospectively. METHODS: Carotid color-flow duplex scans were compared with arteriograms in 457 patients who underwent both studies. Criteria for >or=70% internal carotid artery stenosis were peak systolic velocity >130 cm/sec and end-diastolic velocity >100 cm/sec. Internal carotid arteries with peak systolic velocity <40 cm/sec in which only a trickle of flow could be detected were classified as preocclusive lesions (95% to 99% stenosis). Arteriographic stenosis was determined by comparing the diameter of the internal carotid artery at the site of maximal stenosis to the diameter of the normal distal internal carotid artery. RESULTS: Internal carotid artery stenosis of >or=70% was detected with a sensitivity of 87%, specificity of 97% positive predictive value of 89%, negative predictive value of 96%, and overall accuracy of 95%. Eighty-seven percent of 70% to 99% stenoses were correctly identified. False-positive errors (n=10) were attributed to contralateral internal carotid artery occlusion or high-grade (>90%) stenosis (n=5) and to interpreter error (n=1); no explanation was apparent in the other four. Eleven of 12 false-negative examinations occurred in patients with 70% to 80% internal carotid artery stenosis. CONCLUSIONS: In our laboratories, prospective application of the above velocity criteria identified internal carotid artery stenosis of >or=70% with a reasonably high degree of accuracy. Errors occurred when stenoses were borderline and in patients with severe contralateral disease. With suitably modified velocity criteria, color-flow duplex scanning remains the most reliable noninvasive method for identifying symptomatic patients who are candidates for carotid endarterectomy.

Angiography↗
PubMed1995

Detection of total occlusion, string sign, and preocclusive stenosis of the internal carotid artery by color-flow duplex scanning.

BACKGROUND: Stroke prevention depends on the accurate differentiation of surgically treatable preocclusive lesions from total occlusions of the internal carotid artery. This prospective study was undertaken to review the accuracy of colorflow duplex scanning for identifying carotid string signs, focal preocclusive lesions (95% to 99% stenoses), and total occlusion of the internal carotid artery. MATERIALS AND METHODS: Over an 18-month period, 4,362 patients underwent color-flow duplex scanning of the carotid arteries. Angiograms of 596 internal carotid arteries were available for comparison with the duplex scan findings. Total occlusion was diagnosed by the absence of flow in internal carotid arteries visualized on B-mode scanning. Preocclusive lesions were identified by a trickle of flow in the vessel lumen. RESULTS: Of 65 color-flow duplex scans that predicted total occlusion, 64 (98%) were confirmed by angiography. The negative predictive value for total occlusion was 99%. Twenty-six (87%) of 30 string signs and focal 95% to 99% stenoses were correctly identified. Color-flow scanning prediction of preocclusive lesions was accurate in 84% of 31 cases. Low velocities in the internal carotid artery were usually associated with a string sign, and high velocities with a focal preocclusive lesion. CONCLUSIONS: Color-flow duplex scanning accurately differentiates between stenotic and totally occluded internal carotid arteries. Identification of preocclusive lesions is not as accurate but the results are promising. Arteriographic confirmation of duplex scan findings is necessary only when scans are equivocal.

Aged↗
PubMed1995

Incorporation of endovascular training into a vascular fellowship program.

BACKGROUND: Despite expanding indications for endovascular therapy of peripheral vascular disease, vascular surgeons have largely remained bystanders in the use of this form of treatment for the disease, which is the focus of their profession. Lack of access to training in endovascular techniques is a major obstacle to increasing involvement by vascular surgeons. This paper reports our experience in the endovascular training of vascular surgical fellows without the involvement of radiologists. METHODS: The results of vascular surgery fellows receiving instruction in endovascular diagnostic and therapeutic procedures from vascular surgery faculty were reviewed. RESULTS: Endovascular training of vascular surgery fellows exceeded the case levels recommended by all involved societies. A diverse case mix of 355 endovascular diagnostic procedures were performed with a major complication rate of 0.3% and no procedure-related deaths. Two hundred six endovascular interventions were performed, with an initial technical success rate of 96.6%, a 30-day success rate of 93%, no major complications, and an overall intervention-related mortality rate of less than 1%. CONCLUSIONS: Vascular surgery fellows can receive endovascular training by vascular surgery faculty without the involvement of radiologists and can do so with acceptable success and complication rates. This experience is sufficient to qualify them to perform and teach endovascular therapy in their future practices.

Angioplasty, Balloon↗
PubMed1994

Alpha 1-proteinase inhibitor variant T345R. Influence of P14 residue on substrate and inhibitory pathways.

To test whether the presence of charged residues at position P14 of the reactive center region of noninhibitory members of the serpin family of protein proteinase inhibitors is responsible for their lack of proteinase inhibitory properties, we expressed a variant of the alpha 1-proteinase inhibitor (alpha 1-PI) with arginine substituted for threonine at this position (T345R) and characterized its functional properties. Although the T345R variant reacted with proteinases principally as a substrate, it was still capable of forming stable complexes with the three serine proteinases examined, human neutrophil elastase (HNE), porcine pancreatic elastase (PPE), and trypsin. The fraction of T345R alpha 1-PI that formed a complex with proteinase was quantitated by autoradiography of SDS gels of the variant incubated with 125I-labeled proteinase. The stoichiometry of inhibition (S.I.) (number of mol of alpha 1-PI required to completely inhibit 1 mol of proteinase), which was 1 for both plasma alpha 1-PI and wild-type recombinant alpha 1-PI interacting with each of the proteinases, was very much greater than 1 for T345R variant alpha 1-PI. Values of 9.5, 45, and about 70 were estimated for variant alpha 1-PI inhibition of trypsin, HNE, and PPE, respectively. An inverse relationship between the apparent second-order rate constant and the S.I. for inhibition of PPE by T345R alpha 1-PI suggested that the mutation did not affect the rate-determining step of formation of a transient intermediate complex. Following cleavage of the reactive center loop, there was a large increase in protein stability and changes in the CD spectrum, both consistent with insertion of the reactive center loop into beta-sheet A. This behavior is similar to that of wild-type alpha 1-PI. We conclude that the presence of a charged residue at P14 does not prevent reactive center loop insertion or the functioning of alpha 1-PI as an inhibitor of serine proteinases but does significantly alter the relative rates of the substrate and inhibitory pathways in favor of the former, probably by reducing the rate of the latter reaction.

Animals↗
PubMed1994

Hemodialysis graft salvage with endoluminal stents.

The most common cause of failure of hemodialysis access sites is stenosis within the site. The stenoses have traditionally been corrected surgically, but endovascular techniques may be an alternative method to treat these flow-limiting lesions and maintain graft patency. Over a recent 17-month period, endoluminal stents to relieve stenoses resistant to balloon dilatation alone were placed in 14 access sites. All sites were located on the upper extremity (13 PTFE bridge grafts and 1 A-V fistula). A total of 20 stents were placed: seven at the venous anastomosis, 12 in the venous outflow tract (including 3 in the subclavian vein), and one within the graft. Nine patients had placement of a single stent, four patients had two stents placed, and one patient had three. An additional eight stenotic lesions within these 14 sites were successfully dilated without need of a stent. After stent placement, these 14 sites have remained functional for a mean of 6.2 months. Four were functioning without further intervention at a mean of 8.5 months. Nine sites occluded at a mean of 4.7 months. The remaining site remained functional until death of the patient 10 months after stent placement. Of the nine failed sites, four developed restenosis at the site of stent placement, four developed stenoses at other sites, and the other site was abandoned. Three stents were placed in subclavian vein stenoses, and none of these has failed. Further study is necessary to determine whether endovascular stenting of dialysis access site stenoses will prove to be a durable, cost-effective alternative to surgical revision.

Angioplasty, Balloon↗
PubMed1994

Orthotopic ex vivo renal artery reconstruction.

Ex vivo renal artery reconstruction is a technique used to repair renal vascular lesions not amenable to conventional in situ methods of revascularization, either because of anatomical considerations or the inability of the kidney to tolerate the extended period of warm ischemia necessary to complete the procedure. In general, this refers to lesions at or beyond the division of the main renal artery into the segmental branches. The kidney is mobilized to the level of the abdominal wall after dividing the origins of the renal artery and vein from the aorta and inferior vena cava, respectively. The ureter is left intact. The kidney is cooled by placing it in an external slush bath and by perfusion through the renal vessels of a cold electrolyte solution. A suitable conduit (usually saphenous vein or hypogastric artery) is then prepared for grafting. After completion of the distal anastomosis(es), the kidney is returned to the renal fossa, and the proximal anastomosis to the aorta is completed. The renal vein is then reattached, thus completing revascularization of the kidney. We report our experience with five orthotopic ex vivo renal artery reconstructions. Indications for the procedure, details of the technique, and expected results are discussed.

Adult↗
PubMed1993

Nitrogen dioxide reactivity with proteins: effects on activity and immunoreactivity with alpha-1-proteinase inhibitor and implications for NO2-mediated peptide degradation.

Nitrogen dioxide (NO2), an air pollutant produced by burning fossil fuels and a component of cigarette smoke, is thought to contribute to the pathogenesis of pulmonary diseases, such as emphysema. In order to gain information on the mechanism by which NO2 damages the lung and proteins vital to its function, as well as its reaction with proteins in general, in vitro exposures of alpha-1-proteinase inhibitor (alpha 1PI), elastin, poly-L-lysine, and poly-L-arginine were performed. The ability of alpha 1PI to inhibit its natural physiological target, human neutrophil elastase (HNE), declined with exposure to 54% of the control value at molar ratios of NO2:alpha 1PI of 400:1 and greater. Exposure of alpha 1PI to NO2 resulted in a 50% loss of immunoreactivity with either monoclonal or polyclonal antibodies in an enzyme-linked immunosorbent assay at molar ratios of NO2:alpha 1PI of 100:1 and greater. The results of parallel O-phthalaldehyde and bicinchoninic acid protein assays as well as amino acid analysis on control and NO2-exposed alpha 1PI suggested a reactivity of NO2 with lysine residues. Elastin and poly-L-lysine were labeled by reductive methylation of amino groups with [3H]HCHO prior to treatment with NO2 in aqueous solutions at physiological pH. NO2 exposure of elastin resulted in the solubilization of 84% of the associated radioactivity of which 79% was identified as [3H]methyllysine by amino acid analysis. After NO2 exposure of poly-L-[3H]lysine, gel filtration chromatography revealed that the 50,000 M(r) poly-L-[3H]lysine had been degraded to small peptides of 1-3000 M(r). Similarly, after NO2 exposure of unlabeled poly-L-arginine, gel filtration chromatography, and total peptide analysis revealed that the 47,500 M(r) peptide was also partially degraded to peptides. These results suggest that NO2 reacts with the epsilon-amino groups of Lys residues (primary amines) and with the amide nitrogen (secondary amines) of surface-exposed Lys and Arg residues in the peptide backbone to result in peptide bond cleavage. These findings are the first indication of NO2-mediated peptide degradation and provide additional data on the potential of NO2 to damage proteins vital to the function of the lung in an in vitro exposure system.

Elastin↗
PubMed1993

Advances in the treatment of phlegmasia cerulea dolens.

Phlegmasia cerulea dolens (PCD) is an uncommon, severe form of lower extremity deep venous thrombosis characterized by extremity swelling, cyanosis, and pain. Progression of the thrombotic process may result in extremity gangrene, amputation, and death. The relative value of specific therapeutic regimens in the treatment of this disease remains uncertain. Twelve patients, 9 females and 3 males, with PCD were treated during a 10-year period. Eighteen lower extremities were involved. Pre-existing conditions included malignancy (eight), postoperative state (four), diabetes (three), previous deep venous thrombosis (three), and hypercoagulation (two). Venous gangrene was present in four patients. All patients were treated initially with bedrest, fluid resuscitation, extremity elevation, and systemic high-dose heparin therapy. Five patients had complete resolution with this regimen alone. One patient required cessation of heparin therapy due to heparin-induced thrombocytopenia and developed gangrenous toes. Two patients whose condition failed to respond to heparin therapy underwent catheter-based delivery of urokinase with marked clinical improvement. Four patients, two with venous gangrene, died, three of whom had disseminated malignant disease. A significant percentage of patients with PCD will respond to extremity elevation, fluid resuscitation, and aggressive systemic anticoagulation therapy. Thrombolytic therapy selectively administered is beneficial in patients whose disease fails to respond promptly. Venous thrombectomy should be reserved for patients with contraindications to thrombolysis.

Adult↗
PubMed1991

A 1H NMR probe for mobility in the reactive center loops of serpins: spin-echo studies of native and modified forms of ovalbumin and alpha 1-proteinase inhibitor.

It has recently been proposed that the expression of inhibitory activity in serine protease inhibitors (serpins) is a function of the mobility of the extended alpha-helical reactive center loop [Stein, P.E., Leslie, A.G.W., Finch, J.T., Turnell, W.G., McLaughlin, P.J., & Carrell, R.W. (1990) Nature 347, 99-102]. We have employed solution 1H NMR methods, including the Carr-Purcell-Meiboom-Gill (CPMG) and Hahn spin-echo pulse sequences, to try to identify such regions by virtue of their anticipated longer T2 relaxation times in two of the best characterized members of the serpin superfamily, ovalbumin and alpha 1-proteinase inhibitor. The CPMG spectra of native ovalbumin reveal the presence of long-lived resonances from the methyl protons of alanine residues and the CH3 protons of leucine or valine residues as well as the acetyl and ring methine protons of the carbohydrate moieties. Following reaction of ovalbumin with subtilisin Carlsberg to generate plakalbumin [where excision from within the reactive center loop homologue of a hexa- or heptapeptide, with sequence (E)-A-G-V-D-A-A, occurs], its CPMG spectrum retained almost all of the originally present long-lived resonances. Concurrent with the retention of these mobile resonances in plakalbumin is the appearance of two additional resonances consistent with the formation of new C and N termini. On the basis of the proposed mobility of the reactive center loop, it had been expected that removal of the alanine-rich hexapeptide would result in loss of some or all of the long-lived alanine methyl resonances.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1990

Analysis of refractory period after exercise and eucapnic voluntary hyperventilation challenge.

We compared specific airway conductance (SGaw) and the FEV1 after repetitive exercise or repetitive eucapnic voluntary hyperventilation (EVH) challenges. Replicate challenges were matched in terms of inspired air conditions and minute ventilations (VE) in order to determine the degree of refractoriness after each type of challenge in patients with exercise-induced asthma. Ten patients exercised or hyperventilated dry, room temperature air at matched VE on two study days. When the patients FEV1 had returned to 90% of baseline or better, or at 3.75 h if FEV, had not returned to 90% of baseline, patients repeated the identical exercise or the EVH challenge. Minimum FEV1 values expressed as a percent of predicted FEV1 after the first and second exercise challenges were 52 +/- 16 and 58 +/- 17, respectively, which were statistically different (p less than 0.001; paired t test). Minimum FEV1 values after the first and second EVH challenges were 52 +/- 13 and 59 +/- 9% of predicted, respectively, which were also statistically different (p less than 0.01; paired t test). Seven of 10 subjects demonstrated higher SGaw values after the second exercise challenge compared with the first challenge, whereas eight of 10 subjects showed higher SGaw values after the second EVH challenge compared with the first challenge. Paired t test analysis indicated that percent protection, measured by FEV1, was similar after either type of challenge. We conclude that replicate exercise or EVH challenges with similarly matched inspired air conditions and VE induce similar degrees of refractoriness.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗