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Biomedical subjects

D B Ross

Publications and source records attributed to D B Ross.

At least 37 records · Page 2Linked to original sources
PubMed1998

Atrioventricular septal defect with tetralogy of Fallot: results of surgical correction.

BACKGROUND: The outcome of surgical correction of complete atrioventricular septal defect with tetralogy of Fallot has improved in recent years. Controversy exists about the optimal approach to this complex lesion. Our experience over the past 8 years with a single technique is reviewed. The important anatomic features of this lesion are discussed in relation to our method of repair. METHODS: Between 1988 and 1996, 11 consecutive patients underwent correction of complete atrioventricular septal defect with tetralogy of Fallot. Nine patients had undergone prior palliative shunts. The two-patch technique for atrioventricular septal defect was used. The ventricular septal defect was closed through a right ventriculotomy in each case. The commissure between the superior and inferior bridging leaflets of the left portion of the common atrioventricular valve was closed in each patient. Management of the right ventricular outflow tract was individualized. RESULTS: There was one mortality in the early postoperative period. One patient required reoperation for closure of a dehiscent left atrioventricular valve cleft. All survivors are currently in New York Heart Association functional class I or II at follow-up ranging from 2 to 101 months. CONCLUSIONS: Atrioventricular septal defect with tetralogy of Fallot can be corrected with low mortality using the two-patch technique and closure of the ventricular septal defect through a combined approach using a right ventriculotomy and right atriotomy. Routine closure of the commissure of the left portion of the atrioventricular valve results in a low incidence of regurgitation. A good functional result can be achieved in most patients at intermediate-term follow-up.

Cardiac Surgical Procedures↗
PubMed1997

Aortic valve grafts in the rat: evidence for rejection.

OBJECTIVE: The histopathologic changes of fresh rat aortic valve allografts over time and the effect of cryopreservation were examined. METHODS: Fifty-six syngeneic and allogeneic rat aortic valves were transplanted, either fresh or after cryopreservation, and then at different time points they were explanted and histologically examined in a blinded fashion. RESULTS: Histopathologic changes in the first week are similar in syngeneic and allogeneic grafts. Fresh syngeneic grafts and leaflets retained normal structure up to 56 days. Allogeneic grafts showed retrovalvular thrombus formation with leaflet ghosts and neointimal proliferation. Cryopreservation did not alter this process. CONCLUSIONS: Cardiac allograft valves in the rat model undergo changes that are characteristic of cell-mediated rejection and lead to valve failure.

Animals↗
PubMed1996

Factors in the early failure of cryopreserved homograft pulmonary valves in children: preserved immunogenicity?

METHODS: Between 1990 and 1995, 48 homograft valves (15 aortic and 33 pulmonary), cryopreserved on-site, were implanted to reconstruct the right ventricular outflow tracts in 44 children (mean age 6.2 +/- 6.0 years; range 3 days to 20.2 years). Blinded serial echocardiographic follow-up evaluation was performed for all 45 valves in the 41 survivors. RESULTS: Four homograft valves were replaced because of pulmonary insufficiency (3) or stenosis and insufficiency (1). Freedom from reoperation was 90% (70% interval, 84% to 97%) at 50 months. During the follow-up period 15 valves developed progressive pulmonary insufficiency of at least two grades. Three valves developed transvalvular gradients of > or = 50 mm Hg, and one of these valves was also insufficient. The freedom from echocardiographic failure (two or more grades of pulmonary regurgitation or > or = 50 mm Hg gradient) was 44% at 50 months (70% confidence interval, 32% to 55%). Young age (p = 0.03), low operative weight (p = 0.04), small graft size (p = 0.04), and homograft retrieval-to-cryopreservation time of less than 24 hours (p = 0.02) were significantly associated with failure. The type of donor valve (pulmonic or aortic), donor age, and blood group mismatch were not associated with failure, although blood group mismatch approached significance (p = 0.05). CONCLUSIONS: Homografts function well as conduits between the pulmonary ventricle and pulmonary arteries if long-term valve competency is not crucial. However, many rapidly become insufficient. This has important implications for the choice of a valve if the indication for valve replacement is to protect a ventricle failing due to pulmonary insufficiency. Short periods between homograft retrieval and cryopreservation enhance viability and antigenicity. This may suggest an immunologic basis for the failure.

Adolescent↗
PubMed1995

Cost-effectiveness and efficacy of an on-site homograft heart-valve bank.

OBJECTIVE: To compare the performance and cost-effectiveness of cryopreserved homograft cardiac valves prepared on site to valves prepared commercially. DESIGN: A review of all patients who received homograft heart valves between January 1990 and December 1993, with cost-effectiveness analysis. Follow-up ranged from 1 to 37 months (mean 12 months). SETTING: Tertiary-care adult and pediatric hospitals. PATIENTS: All consecutive patients receiving homograft heart valves in either the aortic or right ventricular outflow tract (RVOT) position since on-site preparation of cryopreserved cardiac valves began in 1990. Forty-three patients received 47 homograft valve replacements: 18 in the aortic position and 29 in the RVOT position. No patients were lost to follow-up. MAIN OUTCOME MEASURES: Valve function as assessed by patient survival, actuarial freedom from reoperation and Doppler echocardiographic assessment of transvalvar gradients and valvar insufficiency. Cost-effectiveness as assessed by a formal evaluation of on-site costs compared with current prices for commercially prepared valves. RESULTS: There were four operative deaths but no late deaths. Four valves were removed. Freedom from reoperation at 3 years was 100% for aortic valve replacement and 85% for RVOT reconstruction. Echocardiographic follow-up of 34 of the remaining 39 patients showed mild or no insufficiency in 24 valves, moderate insufficiency in 8 valves and severe, but not clinically significant, insufficiency in 2 valves. The cost of on-site preparation of the valves was $1363 compared with $5040 for the commercially prepared valves, a cost saving for the group of $172,819. CONCLUSION: On-site preparation is an effective method of preparing cryopreserved cardiac valves and permits significant cost savings.

Cost-Benefit Analysis↗
PubMed1994

Nematode burdens and productivity of grazing cattle treated with a prototype sustained-release bolus containing ivermectin.

One hundred and twenty four-month-old Hereford-Friesian cross heifers weighing from 88 to 130 kg were divided into two equal groups. One group acted as a control with each animal receiving one placebo bolus, the other animals received one prototype intraruminal sustained-release bolus designed to deliver approximately 8 mg ivermectin/day for 100 to 120 days. The boluses were administered the day before turnout in mid-May. Each group was grazed separately for 167 days on pastures contaminated with parasitic nematode larvae including the lungworm Dictyocaulus viviparus, and the gastrointestinal worms Ostertagia ostertagi, Cooperia oncophora and Nematodirus helvetianus. Parasitic disease did not occur in the ivermectin-bolus group, but the control group required anthelmintic treatment to control parasitic gastroenteritis at 111 and 154 days after turnout. Up to the 111th day after turnout, the peak mean nematode egg and larval counts per gram of faeces in controls was, respectively, 564 epg and 0.5 lpg. Based on faecal nematode egg counts and worm burdens in bolus-treated cattle removed from pasture at 119 days after turnout and bolus function studies, it was concluded that ivermectin delivery from the prototype bolus ceased between 95 and 98 days after administration. However, unlike the controls, the treated cattle did not develop parasitic gastroenteritis at any time. Their faecal nematode egg output was significantly (P < 0.01) lower (< 1 epg) compared to the controls and lungworm larval output zero during the functional life of the bolus. The faecal egg and larval outputs continued low until the end of the trial.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Small aortic root in childhood: surgical options.

Aortic valve replacement in the pediatric population is complicated by the often complex nature of the left ventricular outflow tract obstruction. Techniques to enlarge the annulus frequently are necessary. From 1977 to 1991, 32 children underwent an annular enlargement procedure at The Hospital for Sick Children, Toronto. During this same era, 110 children underwent a total of 138 aortic valve replacements. Eleven had the annulus enlarged with a posterior patch technique and implantation of a valve (mechanical 8, porcine heterograft 2, homograft 1) ranging from 20 to 25 mm in diameter. Twenty-two children had an anterior annular enlargement (aortoventriculoplasty) and aortic valve replacement with a valve (mechanical 8, porcine 2, homograft 12) 12 to 27 mm in diameter. One child had a posterior patch enlargement performed, followed by a second operation involving anterior annular enlargement. There was one early death in the posterior annuloplasty group and one late death due to failure of a bioprosthetic valve. There were five hospital deaths in the anterior annuloplasty group (22%; 70% confidence interval [CI], 14% to 32%) and two late deaths. Actuarial survival for the 32 children was 78% (70% CI, 70% to 86%) at 5 years and 65% (70% CI, 48% to 82%) at 10 years after repair. Younger children (age less than 1 year) had a significantly worse survival at 5 years (33%; 70% CI, 14% to 52%) than older children (88%; 70% CI, 82% to 95%). The survivors are well, and no reoperations have been necessary because of the children's outgrowing their valve.

Adolescent↗
PubMed1994

Thromboembolism after the Fontan procedure and its modifications.

The frequency of thromboembolism after the Fontan procedure has not been specifically addressed. Seventy patients underwent this operation between 1987 and 1992, and complete information was available on 64. Forty-five had a right atrium-pulmonary artery anastomosis, 17 had a total cavopulmonary connection, and 2 had a right atrium-right ventricle anastomosis. No patient received anticoagulants for more than 8 months postoperatively. Seven patients died in the early postoperative period (< 30 days). Ten cases of thromboembolism were identified in the follow-up, which ranged from 6 to 55 months (mean follow-up, 24.5 +/- 17 months). They occurred 7 days to 4.5 years after the Fontan repair. Seven thombi were on the systemic venous or pulmonary aspect of the circulation and three, on the systemic arterial aspect. Freedom from thromboembolism was 75% at 4 years. We conclude that thromboembolism is common after the Fontan procedure; it can occur several days to years postoperatively; it is an important cause of morbidity; and it may partly explain late death after the Fontan operation. Our data suggest that all patients undergoing this procedure require long-term anticoagulant therapy.

Anticoagulants↗
PubMed1990

Growth, feed efficiency and carcass composition of finishing Friesian steers fed the beta-adrenergic agonist L-644,969.

The beta-adrenergic agonist L-644,969 was evaluated to determine its effects on growth performance and carcass composition of Friesian steers. L-644,969 is the R,R isomer of 6-amino [[(1-methyl-3-phenylpropyl) amino] methyl]-3-pyridine methanol dihydrochloride. Four groups of 18 steers, averaging 380 kg body weight, were individually given ad libitum access to a pelleted concentrate diet that contained either 0, .25, 1.0 or 4.0 ppm L-644,969 for the final 12 wk of the finishing period. Live weight gain was not affected by L-644,969, but feed consumption was linearly reduced (5.5, 6.3 and 15.7%; P less than .01) and feed conversion efficiency was linearly increased (16, 25 and 31%; P less than .01) relative to unmedicated controls, respectively. In addition, L-644,969 quadratically increased carcass weight (3.7, 9.3 and 8.5%; P less than .01) and dressing percentage (2.7, 7.9 and 7.9%; P less than .001). The proportion of trimmed fat in the carcass was quadratically reduced (14.5, 29 and 36%; P less than .001) and yield of lean meat quadratically increased (6.7, 13 and 15.6%; P less than .001). beta-adrenergic agonist treatment altered the distribution of lean meat such that a greater (P less than .001) proportion of the total lean was in the hind portion of carcasses from treated animals. Based on these findings, we suggest that L-644,969 may have utility as an agent to improve efficiency of production of lean beef.

Adrenergic beta-Agonists↗
PubMed1989

Chemoprophylaxis and immunity to parasitic bronchitis in cattle--a field experiment comparing topical ivermectin and an oxfendazole intraruminal device.

Seeder calves infected with Dictyocaulus viviparus were used to contaminate a field divided into three similar paddocks. Twenty-four autumn-born calves were allocated to three matched groups; one group was given topical ivermectin treatments (0.5 mg/kg) at 3, 8 and 13 weeks after turnout (Day 0); each member of a second group was given an oxfendazole pulse-release intraruminal device (OPRB) at turnout; while a third group was kept as untreated controls to monitor the natural epidemiological pattern of events. Severe pasteurella pneumonia exacerbated by lungworm infection occurred in the controls after Day 24. Two died and repeated doses of antibiotic and anthelmintic therapy were necessary to save the remainder. Clinical signs were much milder in the ivermectin and OPRB groups and resolved with only a single dose of antibiotic. The OPRB group excreted some lungworm larvae at this time, but none was detected in the faeces of the ivermectin group during the grazing season. At housing, five calves from each group and four lungworm-naive calves were challenged with D. viviparus larvae. The infection became patent in all challenge-control calves, but no larvae were passed by any of the trial animals. Post-mortem worm-counts revealed percentage takes for the challenge controls, trial controls, ivermectin and OPRB groups of 16.7, 0.01, 0.9 and 0.2, respectively. All trial groups had therefore developed a substantial immunity.

Administration, Topical↗
PubMed1989

Spontaneous rupture of the diaphragm in labour: a case report.

Spontaneous rupture of the diaphragm during normal labour is extremely rare. It requires emergency surgical correction. The authors report what they believe is only the second reported case. Eleven hours after delivery of a male infant, a 27-year-old woman experienced severe epigastric pain, vomiting and dyspnea, followed by cardiopulmonary arrest. Although the ruptured diaphragm was diagnosed and repaired, she suffered severe anoxic encephalopathy and died 3 weeks after operation without regaining consciousness. Clinicians must be aware of the existence of this rare condition because failure to diagnose and treat the ruptured diaphragm will almost certainly lead to the patient's death.

Adult↗
PubMed1988

Spinous process segmental instrumentation for scoliosis.

Spinous process segmental instrumentation (SPSI) for spinal fusion was devised in 1983 by Drummond et al. in an attempt to achieve the stability of segmental fixation without the known neurologic risks of passing sublaminar wires. We used SPSI in 75 scoliosis patients. Sixty-one had idiopathic scoliosis, 12 had neurogenic scoliosis, and 2 had congenital scoliosis. There were no deep infections, pseudarthroses, or neurologic complications. Two patients experienced upper hook dislodgement with 10 degrees loss of correction. We concluded that SPSI can achieve the correction of Harrington rod instrumentation and the stability of Luque rod segmental instrumentation, without the neurologic risk of sublaminar wiring.

Adolescent↗
PubMed1987

An algorithm for planning stereotactic brain implants.

A computer software package was developed for the planning and execution of brain biopsy and radioactive implant procedures with the BRW Stereotaxic System. With the application of computer graphics and a zero-one integer variable programming algorithm, an implant plan with accompanying isodose distributions and stereotactic coordinates can be easily accomplished at the time of the operation when the computer imaging terminal and a printer/plotter is placed in the operating room.

Algorithms↗
PubMed1985

Persistent anthelmintic activity of ivermectin in cattle.

Two studies are described which demonstrate the persistent activity of ivermectin injected subcutaneously into cattle at 200 micrograms/kg in preventing the establishment of induced infections with the gastrointestinal parasites Ostertagia ostertagi and Cooperia oncophora and the lungworm Dictyocaulus viviparus. These results indicated a reduction in mean worm count compared with the control group for O ostertagi of more than 99, 45 and 94 per cent with a seven, 14 or 21 day interval between treatment with ivermectin and the administration of infective larvae, respectively, in trial 1 and more than 99, more than 99 and 99 per cent at seven, 10 or 14 days, respectively, in trial 2. Corresponding values against C oncophora were 99, 0 and 45 per cent at seven, 14 and 21 days in trial 1 and more than 99, 84 and 31 per cent at seven, 10 and 14 days in trial 2. Against D viviparus, reduction in counts were more than 99, 98 and more than 99 per cent at seven, 14 and 21 days, respectively, in trial 1 and 100, 100 and 100 per cent at seven, 10 and 14 days, respectively, in trial 2. The relevance of these results to the build-up of infective larvae on pasture and infection in cattle is discussed.

Animals↗