Biomedical subjects

J R Stewart

Publications and source records attributed to J R Stewart.

At least 19 recordsLinked to original sources

PubMed1996

Safety of remote aortic valve replacement after prior coronary artery bypass grafting.

BACKGROUND: A previous coronary artery bypass grafting (CABG) procedure may complicate subsequent aortic valve replacement (AVR). However, the operative risks and long-term outcome of patients who undergo these two procedures remain poorly defined. METHODS: The medical records of all patients undergoing AVR between February 1986 and September 1995 were reviewed retrospectively. The patients selected for analysis had previously undergone CABG. RESULTS: We performed AVR in 23 consecutive patients who had previously undergone CABG (mean number of grafts, 2.8). The AVR was performed an average of 7.6 years after CABG (range, 2 to 17 years). There were 20 men and 3 women, with a mean age of 69 years (range, 56 to 85 years). Twenty patients were operated upon for aortic stenosis (mean gradient 54 mm Hg, mean valve area 0.7 cm2), and 3 patients underwent operation for aortic regurgitation. The average aortic valve gradient at the initial revascularization operation was 8 mm Hg (range, 0 to 29 mm Hg). There was no correlation between the aortic valve gradient at the initial revascularization and the interval between CABG and AVR. At the second operation, AVR was performed alone in 11 patients, combined with repeat CABG in 11 patients (mean number of grafts, 1.4), and with mitral valve replacement in 1 patient. A mechanical prosthesis was selected in 14 patients, and a bioprosthesis was used in 9 patients. There were no perioperative deaths. There were five late deaths at an average follow-up of 44 months. The 5-year actuarial survival was 71%. CONCLUSIONS: Previous CABG poses added technical challenges at the time of reoperation for AVR. The operation can be performed safely, with the expectation of satisfactory long-term survival.

Actuarial Analysis↗

PubMed1996

Evaluation of pulmonary lesions with FDG-PET. Comparison of findings in patients with and without a history of prior malignancy.

STUDY OBJECTIVE: The purpose of this study was to evaluate the accuracy of positron emission tomography (PET) using F-18 fluorodeoxyglucose (FDG) in differentiating benign from malignant pulmonary lesions both in patients with and without a history of prior malignancy. DESIGN: Forty-eight consecutive patients with pulmonary lesions suspicious for malignancy underwent FDG-PET scanning. Group 1 included 27 patients without and group 2 included 21 patients with a history of malignancy. Pathologic proof of diagnosis was obtained for 32 patients and 16 patients were followed up clinically and radiographically for at least 6 month. The standard uptake ratio (SUR) and the lesion to background (L/B) ratio were determined in 45 patients. SETTING: Vanderbilt University Medical Center. RESULTS: In group 1, the average SUR and L/B ratio for malignant lesions (n=14) were 8.9 +/- 4.9 and 20.6 +/- 14.2, respectively. For benign lesions (n=12), the average SUR was 3.3 +/- 3.2 and L/B ratio was 5.2 +/- 5.5. In group 2, the average SUR and L/B ratio for malignant lesions were not significantly different from group 1. Using either a SUR greater than 2.5 or L/B ratio greater than 5 as an cutoff level to differentiate benign and malignant lesions, the sensitivity and negative predictive value in both groups were 100%. There were five false-positive studies in group 1 and one in group 2, including tuberculosis (n=2), a granulomatous lesion (n=1), an inflammatory lesion (n=1), a schwannoma (n=1), and a fibrous mesothelioma (n=1). The overall accuracy was 88%, 81% in group 1, and 95% in group 2. CONCLUSION: FDG-PET can identify malignant pulmonary lesions both in patients without and with a history of prior malignancy with a high sensitivity and negative predictive value for lesions greater than 1 cm (100% in this study). High FDG uptake by some inflammatory processes and benign tumors may cause false-positive results. Semiquantitative evaluation using SUR or L/B ratio provides similar accuracy.

Adult↗

PubMed1995

Embryonic development of central nervous system myelination in a reptilian species, Eumeces fasciatus.

The myelin proteolipid proteins are a vital component of the vertebrate central nervous system (CNS), contributing essential functions to the development of the myelinating cells of the CNS and to the structure of CNS myelin. Alternative splicing of the proteolipid protein (PLP) gene to produce two related isoforms occurs in Mammalia, Aves, and Reptilia, but not Amphibia. As part of a long-term investigation into the function of the different isoforms of PLP, embryonic development, myelination, and PLP gene expression in reptilian CNS were examined. PLP gene expression was already substantial by day 19 (stage 39) of the 27-day Eumeces fasciatus egg incubation period. By day 21 of incubation, also stage 39, PLP mRNA was at peak levels; there was a significant amount of CNS myelination as demonstrated by electron microscopy of the spinal cord; and the reflexive motor response was evident. Although most axons were myelinated by the time of hatching, myelin sheaths continued to increase in size and compactness after hatching. The correlation of physiological development, CNS myelination, and expression of the PLP gene in the lizard corresponded well with the developmental pattern seen in mammals.

Animals↗

PubMed1995

Radiation injury to the heart.

For the RTOG Consensus Conference on Late Effects of Cancer Treatment we summarize the clinical manifestations of cardiac complications appearing months to years following incidental irradiation of the heart during treatment of thoracic neoplasms. The most common effects present as pericardial disease, however, it is becoming more clear that precocious or accelerated coronary artery disease is an important late effect, especially in patients treated with radiation before the age of 21 years. To the extent it is known, the pathophysiology of the various syndromes is described and the extensive literature on dose, volume, and fractionation factors is reviewed. Based upon our current understanding of late cardiac effects, a clinical grading system has been developed and is published elsewhere in this issue.

Animals↗

PubMed1995

MRI complements standard assessment of right ventricular function after lung transplantation.

BACKGROUND: Changes in right ventricular mass and ejection fraction after single-lung transplantation for pulmonary hypertension are poorly understood. METHODS: To complement functional data provided by echocardiography, radionuclide ventriculography, and right heart catheterization, magnetic resonance imaging was used to assess right ventricular function in 5 single-lung transplant recipients with preoperative pulmonary hypertension and right ventricular dysfunction (right ventricular ejection fraction, 0.21 +/- 0.09). The right and left ventricular mass, ejection fraction, and mass ratio (left ventricular mass/right ventricular mass) were calculated from the magnetic resonance images. RESULTS: The mean pulmonary artery pressure fell from 72 +/- 18 to 21 +/- 8 mm Hg after transplantation. At 3 months after transplantation both the left ventricular and right ventricular ejection fractions approached normal values, as shown by both radionuclide ventriculography and magnetic resonance imaging, but the right ventricular mass remained abnormally high with slightly low mass ratios. By 1 year both the left ventricular and right ventricular masses had regressed to normal with near-normal mass ratios. CONCLUSIONS: Right ventricular performance returns to nearly normal early after transplantation, but the right ventricular mass regresses over a more prolonged time. Cine magnetic resonance imaging provides a noninvasive means of assessing changes in right ventricular function and mass after lung transplantation.

Adult↗

PubMed1994

A comparison of the efficacy of HI6 and 2-PAM against soman, tabun, sarin, and VX in the rabbit.

This study compared the efficacy of HI6 and 2-PAM against nerve agent (soman, tabun, sarin, and VX)-induced lethality in the atropinesterase-free rabbits pretreated with vehicle (controls) or pyridostigmine. Treatment was administered at signs or 2 min after agent challenge and consisted of oxime (100 mumol/kg) + atropine (13 mg/kg) (alone or together with diazepam). Twenty-four-h LD50 values were calculated for soman- and tabun-intoxicated animals, whereas 24-h survival was noted in animals given 10 LD50s of sarin or VX. In pyridostigmine and control rabbits intoxicated with soman and treated with oxime + atropine (alone or together with diazepam), HI6 was 3-5 times more effective than 2-PAM. In contrast, HI6 was less effective than 2-PAM against tabun poisoning. In pyridostigmine-pretreated animals exposed to tabun, efficacy was increased more than 3-fold when compare to tabun-challenged animals treated with atropine + HI6 alone. Both oximes were highly effective against sarin and VX. These findings suggest that HI6 could replace 2-PAM as therapy for nerve agent poisoning, because it is superior to 2-PAM against soman, and when used in pyridostigmine-pretreated animals, it affords excellent protection against all four nerve agents when used in combination with atropine (alone or together with diazepam) therapy.

Animals↗

PubMed1994

Electron arc therapy of the postmastectomy prosthetic breast.

PURPOSE: Reconstructive surgery of the postmastectomy breast presents new challenges to postoperative radiation therapy. This paper evaluates the dosimetric significance of oblique incidence of the electron field on the reconstructed mound during arc therapy. METHODS AND MATERIALS: Using film densitometry, the relative dose distributions resulting from electron arc therapy incident on phantoms simulating the breast and chest wall dimensions of an actual patient are evaluated. RESULTS: Irradiation of the breast phantom in normal supine position results in constriction of the dose distribution at the junction of the reconstructed mound with the chest wall. Angulation of the phantom to provide a more normal incidence of the electron beam during arc reduces the constriction by minimizing obliquity of the incident electrons. CONCLUSION: These measurements suggest that, with proper positioning of the patient relative to the incident electron beam, electron arc therapy may be used as an alternative treatment technique for treatment of the postmastectomy reconstructed breast and chest wall.

Breast Neoplasms↗

PubMed1994

Thymectomy for the myasthenia gravis patient: factors influencing outcome.

Thymectomy is a therapeutic option for patients with myasthenia gravis with moderate to severe disability. To document the efficacy of thymectomy coupled with medical therapy to treat this disease and to identify clinical factors that influence outcome, the clinical courses of all 46 patients (12 male and 34 female; mean age, 30 +/- 16 years) with myasthenia gravis who underwent thymectomy through a median sternotomy at a single institution over a 21-year period were reviewed. Clinical staging was determined preoperatively, at 1 month, 6 months, and 12 months postoperatively, and at last follow-up (mean time, 75 months postoperatively) using the Oosterhuis classification. Changes in severity of illness were graded as "deteriorated," "unchanged," "improved," or "much improved." Preoperative Oosterhuis classification was 3.3 +/- 1.1 and at last follow-up, 1.4 +/- 1.2 (p = 0.022). At last follow-up, 40 patients (87%) were in the improved or much improved category, and 6 patients were in the deteriorated or unchanged category. Status at 1 month, 6 months, and 12 months after operation predicted outcome at last follow-up visit (p = 0.007, p = 0.005, and p = 0.001, respectively). Clinical factors that positively influenced outcome were age less than 45 years (p = 0.004), female sex (p = 0.0309), and preoperative stage (p = 0.021).

Acetylcholine↗

PubMed1994

Operative risk factors and durability of repair of coarctation of the aorta in the neonate.

The risk factors for the operative mortality and long-term durability of repair after surgical correction of coarctation of the aorta in neonates remain controversial. Between January 1970 and January 1993, 139 patients under 1 month of age underwent repair of coarctation of the aorta. Complex intracardiac defects were present in 59 patients. Another 44 patients had an associated ventricular septal defect. Subclavian artery flap repair was performed in 92 patients; end-to-end anastomosis (38 patients) and patch angioplasty (9 patients) were performed less commonly. The hospital mortality was significantly higher in patients with complex intracardiac defects (9 of 59 patients; 15.2%) than in those with a ventricular septal defect (1 of 44 patients; 2.3%) or with isolated coarctation (none of 36 patients; p = 0.007). Elevated pulmonary artery diastolic pressure (p = 0.041) and complex intracardiac anomalies (p = 0.048) were found to be independent predictors of hospital mortality. The presence of a complex cardiac defect (p < 0.001) was an independent predictor of poor long-term survival. Recurrent stenosis requiring reoperation had occurred or balloon dilation had been necessary in 27.9% of the children at 5 years postoperatively. In patients followed up for at least 5 years, the recurrence-free survival was better in those who had undergone subclavian artery flap repair than in those who had undergone end-to-end repair (p = 0.017). When coarctation of the aorta must be repaired in the neonate, operative mortality and long-term survival are affected by the complexity of associated intracardiac anomalies.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Coarctation↗

PubMed1994

Effects of procainamide and lidocaine on defibrillation energy requirements in patients receiving implantable cardioverter defibrillator devices.

INTRODUCTION: In acute canine studies, lidocaine, but not procainamide, increases defibrillation energy requirements. We evaluated the effects of lidocaine or procainamide on defibrillation energy requirements in 27 patients undergoing intraoperative testing for implantable cardioverter defibrillator device placement. METHODS AND RESULTS: Patients were tested off antiarrhythmic drugs and again following either lidocaine (200 to 250 mg loading and 3 mg/min maintenance infusions) or procainamide (1 gm loading and 3 to 4 mg/min maintenance infusions). The defibrillation testing protocol consisted of initial testing at 15 J, followed by higher or lower energies to determine the lowest energy producing three consecutive successful defibrillations. Overall, the mean defibrillation energy increased from 14 +/- 5 J to 18 +/- 7 J during lidocaine (plasma concentration 5.1 +/- 1.6 micrograms/mL; P < 0.02) but were similar at baseline (12 +/- 5 J) and during procainamide infusion (13 +/- 6 J) (plasma concentration: procainamide 10.7 +/- 7.2 micrograms/mL; N-acetyl procainamide 1.0 +/- 0.4 micrograms/mL). A positive linear correlation was found between lidocaine plasma concentration and percent change in defibrillation energy (lidocaine: r = 0.61; P = 0.01). Procainamide raised the defibrillation energy in three patients, two with supratherapeutic plasma concentrations. The increase in defibrillation energy equaled or exceeded 25 J in four patients after lidocaine and in one patient after procainamide. CONCLUSION: The data suggest that at high plasma concentrations, lidocaine and procainamide adversely affect defibrillation energy requirements consistent with an adverse, concentration-dependent effect of sodium channel blockade on defibrillation energy requirements in patients.

Aged↗

PubMed1994

Single lung transplantation: a temporal look at rejection, infection, and survival.

Single lung transplantation (SLT) has emerged as routine therapy for selected patients with end-stage lung disease. This study examines the incidence of rejection, infection, and survival during the first posttransplant year. Twenty-one patients (12 male, 9 female; mean age 46 +/- 13 years) underwent 23 SLT procedures (12 left, 11 right lung). Indications were pulmonary fibrosis in six, emphysema in seven, primary pulmonary hypertension in three, Eisenmenger's syndrome in one, pulmonary veno-occlusive disease in one, a-1 antitrypsin deficiency in two, CREST syndrome in one, and retransplantation (graft failure and bronchiolitis obliterans) in two. All were maintained on triple immunotherapy. Survival at 1 year was 100%. The five patients with preoperative pulmonary hypertension had normal hemodynamics at follow up. Freedom from event at 1 year was rejection 23 per cent, all infections 6 per cent, viral 40 per cent, bacterial 55 per cent, fungal 74 per cent. At 1 year, cumulative incidence (events/patient-year) was rejection 1.61, all infections 2.18, viral 0.78, bacterial 1.12, fungal 0.28. Two of 21 patients have developed bronchiolitis obliterans at 1 and 2 years posttransplant. SLT provided safe, effective treatment for a wide variety of end-stage lung diseases. Rejection and infection, although common, may be safely treated with resolution.

Actuarial Analysis↗

PubMed1993

Nonsanction seat belt law enforcement: a modern day tale of two cities.

This paper describes the implementation and evaluation of a nonsanction seat belt law enforcement program in two experimental communities of contrasting size in a state with a mandatory belt law. The main ingredients of the program were seat belt "salutes," public information and education, and limited use of inexpensive economic incentives. Driver shoulder belt use data collected before, during, and after the experimental programs, compared to similar data collected in a comparison community, showed the approach to be effective. While standard seat belt enforcement activities without incentives have been shown to be effective, many police departments, especially in smaller communities, are reluctant to make wholesale increases in seat belt citations. Although requiring some additional level of manpower and resources, a nonsanction approach to seat belt law enforcement can provide an alternate way of increasing belt use in these communities.

Ethnicity↗

PubMed1993

Observed and self-reported seat belt wearing as related to prior traffic accidents and convictions.

During the summer of 1987, 10,000 color-coded mailback questionnaires that identified belted and unbelted North Carolina drivers were handed out at the 72 sites that constitute the probability sample for determining the statewide belt use rate in North Carolina. By obtaining identifying information to determine the winner of a $500 prize from among the 5,074 respondents, police-reported traffic accident and conviction records from the North Carolina driver history file were linked to the belted and unbelted respondents. Analyses found that drivers who had been observed not wearing seat belts had 35% more accidents and 69% more convictions than did belted drivers in the previous four-year period. Similar findings were obtained from self-reported belt use.

Accidents, Traffic↗

PubMed1993

Seat belt use and accident involvement: a comparison of driving behavior before and after a seat belt law.

In an earlier study, researchers at the University of North Carolina Highway Safety Research Center found drivers classified as seat belt nonusers on the basis of direct observation and self-reported belt use to be overrepresented in prior accidents and violations. This study represents a follow-up and extension of the earlier study where accident and violation rates over a 2.5-year interval following the classification by seat belt use status are compared. Seat belt nonusers were again found to be overrepresented in both accidents and violations. In other analyses of these data, changes in seat belt use status were found not to be associated with changes in accident or violation rates, and seat belt use rates reported by police in accidents following the mandatory seat belt law greatly exceeded both the observed and self-reported use rates. This was especially pronounced for drivers who responded that they rarely or never used seat belts.

Accidents, Traffic↗

PubMed1993

Third-time coronary artery bypass grafting: midterm results.

Minimal data are available regarding the results of patients who have undergone myocardial revascularization more than twice. The records of 13 consecutive patients who underwent a coronary artery bypass procedure for the third time were reviewed. The indication for operation was unstable angina in all patients. All patients were placed on cardiopulmonary bypass through a median sternotomy. The mean number of bypass grafts placed at the third operation was 1.9 (range, 1 to 3 grafts). A new internal mammary artery graft was placed in 6 patients (2 had prior internal mammary artery grafts). Hospital mortality was 7.7% (1/13). The single death was due to incomplete revascularization in a patient with poor distal vessels. Three patients required intraaortic balloon pump support postoperatively, and 2 patients had prolonged ventilatory insufficiency. There have been no late deaths. The 12 survivors have been followed up a mean of 44 months (range, 6 to 90 months). Four remain asymptomatic; 5 have mild angina easily controlled with medication. All except 1 are in improved condition compared with their preoperative status. We conclude that a third myocardial revascularization can be performed with low mortality and morbidity and with the expectation of long-lasting symptomatic improvement.

Aged↗

PubMed1993

Cytomegalovirus disease after heart transplantation: is acyclovir prophylaxis indicated?

To determine the efficacy of acyclovir prophylaxis in preventing cytomegalovirus (CMV) disease after heart transplantation, the clinical course of 103 patients (ages, 0.1 to 62 years; mean age, 41.8 years; 87 males, 16 females) was analyzed. Active CMV infection (defined as a positive culture from any site or a fourfold increase in immunoglobulin G antibody titers) occurred in 64% (66/103) and clinical CMV disease (defined as pathologic evidence of CMV in tissue biopsy or a typical CMV syndrome with fever and two of the following: leukopenia, thrombocytopenia, atypical lymphocytes, and elevated liver function test results in a patient with CMV infection) occurred in 25% (26/103). Independent variables studied included acyclovir prophylaxis, duration of acyclovir use, duration and type of induction therapy, donor and recipient CMV status, total steroid dose at 3 and 6 months, azathioprine dose and cyclosporine level at 3 months, age, and sex. In a multivariate regression analysis, acyclovir prophylaxis was independently associated with freedom from CMV disease (p = 0.029). Positive donor CMV status (p = 0.025), higher total steroid dose at 3 months (p = 0.036), and lower azathioprine dose at 3 months (p = 0.047) were associated with higher occurrence of CMV disease. The use of antilymphocyte induction therapy was associated with an increased occurrence of active CMV infection (p = 0.022) but not CMV disease. The prophylactic administration of acyclovir reduced the occurrence of CMV disease after heart transplantation.

Acyclovir↗

PubMed1993

Preliminary results with neoadjuvant therapy and resection for esophageal carcinoma.

Between December 1988 and August 1992, 68 patients with adenocarcinoma (n = 39) and squamous carcinoma (n = 29) of the esophagus were entered prospectively in a treatment protocol to receive two cycles of cisplatin, 5-fluorouracil, etoposide, leucovorin, and 3,000 cGy of radiation to the involved esophagus and adjacent mediastinum, followed by resection. There were four deaths during chemotherapy, and 7 patients had a decline in condition or were denied operation. Fifty-six patients have come to operation, and 1 awaits resection. Twenty-two patients had transhiatal esophagectomy and 29 patients had esophagogastrostomy with a combined abdominal and right thoracic approach. Five patients did not undergo resection at operation. There was one hospital death (2%). A complete response to preoperative therapy was seen in 12 patients (21%): 5 of 20 with squamous cancer (25%) and 7 of 36 with adenocarcinoma (19%). Average follow-up is 19 months. Median survival in these patients after entrance in the protocol is 24 months. Actuarial survival at 12, 18, and 24 months is 72% (confidence limits, 66% and 78%), 53% (confidence limits, 46% and 60%), and 51% (confidence limits, 44% and 58%). Significantly better survival was associated with adenocarcinoma (p = 0.041). There is no survival advantage based on complete response to preoperative therapy. This neoadjuvant regimen is effective in patients with squamous carcinoma and adenocarcinoma. These preliminary results demonstrate an improved median and actuarial survival compared with historical controls in 137 patients operated on between 1966 and 1985 at our institution.

Adenocarcinoma↗

PubMed1993

Noninvasive detection of acute rejection in a new experimental model of heart transplantation.

We have shown that positron emission scintigraphy detects changes in the uptake of 18-F 2-deoxyglucose and 13-N ammonia by the acutely rejecting myocardium in a nonworking model of heterotopic heart transplantation in the rat. We developed a new working model of heterotopic heart transplantation to determine the possible relevance of these changes to clinical transplantation. Moderate aortic valvular regurgitation was produced allowing the heterotopic left ventricle to fill and eject. Rejecting allografts and nonrejecting isografts (controls) were studied 4 days after transplantation. Histologically, isografts were normal and all allografts showed mild acute rejection. Decay-corrected uptakes of 18-F 2-deoxyglucose and 13-N ammonia reflect glucose metabolism and blood flow, respectively. Values are presented as percent of injected dose per gram of tissue. Uptake of 18-F 2-deoxyglucose was higher in rejecting allografts compared with nonrejecting isografts (3.0 +/- 1.8 versus 1.1 +/- 0.4; p = 0.024). Ammonia uptake was elevated in allografts compared with isografts (2.2 +/- 0.5 versus 1.3 +/- 0.5; p = 0.023). Uptakes of 18-F 2-deoxyglucose and 13-N ammonia are higher in mildly rejecting allografts, implying increased glucose utilization and blood flow during acute rejection. These data support our earlier findings of changes in myocardial metabolism in the absence of diminishing blood flow in acutely rejecting hearts. This model may lead to a better understanding of the physiology and metabolism of acute rejection.

Animals↗