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Biomedical subjects

G W Williams

Publications and source records attributed to G W Williams.

At least 55 records · Page 3Linked to original sources
PubMed1987

The International Apheresis Registry: results of 1983 second pilot.

Results of the second pilot of the International Apheresis Registry for 1983 involving 37 centers on four continents are presented. This report is a follow-up of the initial pilot reported previously and includes the results of 37 additional centers reporting on 659 patients for a total of 5,780 treatments. The results were collected through a single-page questionnaire. Information gathered included patient demographics, medical history, treatment specifics (type, methodology, access type, anticoagulants, drugs), side effects, response, and payment provider. The data are grouped by regions (East, Europe, and North America). Analysis of the data identifies the regional differences in apheresis usage and treatment specifics, suggesting that an international view of apheresis is more representative of this therapeutic modality than national results, which are highly dependent on the local economics and available technology.

Adult↗
PubMed1986

Influence of the internal-mammary-artery graft on 10-year survival and other cardiac events.

We compared patients who received an internal-mammary-artery graft to the anterior descending coronary artery alone or combined with one or more saphenous-vein grafts (n = 2306) with patients who had only saphenous-vein bypass grafts (n = 3625). The 10-year actuarial survival rate among the group receiving the internal-mammary-artery graft, as compared with the group who received the vein grafts (exclusive of hospital deaths), was 93.4 percent versus 88.0 percent (P = 0.05) for those with one-vessel disease; 90.0 percent versus 79.5 percent (P less than 0.0001) for those with two-vessel disease; and 82.6 percent versus 71.0 percent (P less than 0.0001) for those with three-vessel disease. After an adjustment for demographic and clinical differences by Cox multivariate analysis, we found that patients who had only vein grafts had a 1.61 times greater risk of death throughout the 10 years, as compared with those who received an internal-mammary-artery graft. In addition, patients who received only vein grafts had 1.41 times the risk of late myocardial infarction (P less than 0.0001), 1.25 times the risk of hospitalization for cardiac events (P less than 0.0001), 2.00 times the risk of cardiac reoperation (P less than 0.0001), and 1.27 times the risk of all late cardiac events (P less than 0.0001), as compared with patients who received internal-mammary-artery grafts. Internal-mammary-artery grafting for lesions of the anterior descending coronary artery is preferable whenever indicated and technically feasible.

Coronary Artery Bypass↗
PubMed1985

Interobserver variability in EEG interpretation.

A random sample of 100 active electroencephalographers in the United States evaluated 10-second samples of 12 selected EEGs. The evaluations consisted of multiple-choice questions related to the age of the patient, EEG finding, artifact, and consciousness of the patient. The rate of reporting the "correct" response was examined in terms of various respondent characteristics such as EEG board certification, age, percent of time in clinical EEG work, and number of recordings interpreted annually. This study indicates that, even today, there is considerable variability in EEG interpretation, and that this variability is influenced by specific reader characteristics.

Action Potentials↗
PubMed1985

Hemodynamic response to oxygen therapy in chronic obstructive pulmonary disease.

At six centers, 203 patients with stabilized hypoxemic chronic obstructive pulmonary disease were evaluated hemodynamically during a continuous or 12-hour oxygen therapy program. Neither oxygen therapy program resulted in correction or near-correction of the baseline hemodynamic abnormalities. The continuous oxygen therapy group did show improvement in pulmonary vascular resistance, pulmonary arterial pressure, and stroke volume index. The improvement in pulmonary vascular resistance was associated with improved cardiac function, as evidenced by an increase in baseline and exercise stroke volume index. The nocturnal oxygen therapy group showed stable hemodynamic variables. For both groups, changes in mean pulmonary artery pressure during the first 6 months were associated with subsequent survival after adjustment for association with the baseline mean pulmonary artery pressure. Continuous oxygen therapy can improve the hemodynamic abnormalities of patients with hypoxic chronic obstructive pulmonary disease. The hemodynamic response to this treatment is predictive of survival.

Aged↗
PubMed1985

In vivo hemodynamic comparison of porcine and pericardial valves.

The bovine pericardial valve and the SupraAnnular valve have been developed to improve the hemodynamic function of tissue valves. Hemodynamic performances of the standard Carpentier-Edwards porcine valve, the Carpentier-Edwards SupraAnnular valve, and the Carpentier-Edwards bovine pericardial valve were compared in the aortic position. One hundred patients undergoing aortic valve replacement were studied intraoperatively. Mean gradient across the valve decreased for standard and pericardial valves as valve size increased. At the same flow rate, the 23 mm pericardial valve had larger valve orifice areas, higher performance indices, and lower gradients than the 23 mm SupraAnnular valve. The SupraAnnular valve is hemodynamically superior to the standard Carpentier-Edwards porcine bioprosthesis. The Carpentier-Edwards pericardial valve, however, is less obstructive in the aortic position than either of the porcine valves.

Aortic Valve↗
PubMed1985

Hemodynamic performance of the Carpentier-Edwards pericardial valve in the aortic position in vivo.

The bovine pericardial valve was developed to improve the hemodynamic function of tissue valves. Eighty-one patients undergoing aortic valve replacement with the Carpentier-Edwards pericardial valve in the aortic position were studied intraoperatively. Mean gradient across the valve (mm Hg) decreased as valve size increased: size 19, 23.0 +/- 7.8; size 21, 19.7 +/- 6.6; size 23, 15.2 +/- 8.6; size 25, 13 +/- 4.0. Mean valve orifice area (cm2) increased as valve size increased: size 19, 1.1 +/- 0.4; size 21, 1.4 +/- 0.6; size 23, 2.0 +/- 0.7; size 25, 2.1 +/- 0.7. The mean transvalvular gradient, valve orifice area, and performance index increased as mean flow increased. The Carpentier-Edwards pericardial valve provides excellent hemodynamic performance that is acceptable even in size 19.

Animals↗
PubMed1984

Analysis of relative change and initial value in biological studies.

In analyzing longitudinal data, the relationship between initial value (x1) and change in response to a maneuver or over time is often of interest. This relationship is often determined by the Pearson correlation between x1 and subsequent change (x2 - x1), but a correlation will often be obtained by mathematical necessity even when x1 and x2 are uncorrelated. It has been suggested that use of relative change, or (x2 - x1)/x1, avoids these mathematical artifacts. By reference to early work by Pearson (Proc. R. Soc. London 60: 489-498, 1897) on an approximation to the correlation between ratios and by computer simulations, this paper shows that this solution is frequently not valid. An alternative approach to the analysis of the relationship between x1 and relative change is presented and is illustrated by a study of renal blood flow.

Antihypertensive Agents↗
PubMed1984

Studies of the antibacterial effect of the scandium complex of enterochelin.

The scandium complex of enterochelin is known to be assimilated and degraded by enterobacterial pathogens, liberating intracellular scandium. Macromolecular synthesis was inhibited in the order RNA, protein, DNA and phospholipid. Some component of heat-inactivated serum acts in concert with the complex inducing RNA degradation and killing. Both processes are inhibited by dinitrophenol. These biochemical changes resemble those found during complement mediated killing. An examination of the effect on synchronously growing cells suggests that the complex may exert its primary effect during the initiation of chromosome replication.

Anti-Bacterial Agents↗
PubMed1984

Weighted criteria for the diagnosis of systemic lupus erythematosus.

The preliminary American Rheumatism Association (ARA) criteria for classification of systemic lupus erythematosus (SLE) were evaluated for sensitivity and specificity in 87 patients with SLE and 73 without SLE from a rheumatology population. Using these data, Bayes' theorem was employed to weight the criteria so that a scoring system could be developed, allowing more accurate use of the criteria in diagnosis. Combinations of serologic test results were evaluated in a similar manner. Comparison of weighted scores with criteria counts showed greater sensitivity and specificity of the former whether the 1971 or modified 1982 ARA criteria were used. Weighted criteria may be more useful in clearly defining patient populations for studies of SLE.

Antibodies, Antinuclear↗
PubMed1984

Deep-vein thrombosis following total knee replacement. An analysis of six hundred and thirty-eight arthroplasties.

For this study on the incidence and prevention of deep-vein thrombosis, we examined the data on 517 patients with 638 total knee replacements. All of the patients had postoperative venograms and 475 had postoperative perfusion lung scans. We collected data on known risk factors, tourniquet time, knee deformity, postoperative rehabilitation, and methods of prophylaxis, and performed extensive statistical evaluation. Forty-nine patients inadvertently did not receive prophylaxis, and in forty-one (84 per cent) of them ipsilateral deep-vein thrombosis developed. The incidence of ipsilateral thrombosis was 57 per cent in the 468 patients who did receive some form of prophylaxis. Ipsilateral thrombosis in the popliteal veins or thigh was seen in 11 per cent of the patients with unilateral total knee replacement, and contralateral thrombosis was noted in 3 per cent. Bilateral total knee replacement was associated with a 58 per cent incidence of ipsilateral deep-vein thrombosis in the calf and a 14 per cent incidence in the thigh. Pulmonary embolism was diagnosed clinically in nine patients (1.7 per cent), but was suggested on perfusion lung scans in thirty-nine patients (7 per cent). Twelve patients (2.3 per cent) received formal anticoagulant therapy. In no patient was the pulmonary embolism fatal. No specific high-risk population was identified. While no one prophylactic regimen was proved to be more effective than another in our series, we think that prophylactic measures should be part of the management of patients undergoing total knee replacement.

Adult↗
PubMed1983

Fifteen year survival study of patients with obstructive coronary artery disease.

Survival rates were determined for a group of 598 patients in whom severe coronary disease was demonstrated by arteriography; initially they were treated medically and were followed-up for 15 years. Deaths due to noncoronary causes were uncommon (5% of total) in the first 5 year period but were frequent (36%) in the third period. Survival rates were 48%, 28%, 18%, and 9% for patients with single-, double-, triple-, and left main artery disease, respectively. Abnormalities documented by ventriculography were related to survival. In 386 patients who would have been candidates for bypass surgery, survival rates were 58%, 35%, 26%, and 11% for those with single-, double-, triple-, and left main artery disease, respectively. Cardiac survival curves for single-, double-, and triple-artery disease in candidates for surgery and curves constructed on the basis of 3% mortality per artery per year corresponded fairly closely. When an abnormal electrocardiogram (ECG) is considered as a single variable in multivariate analysis, 5 year survival rates of candidates for surgery were influenced by the following in order of importance: abnormal ECG, symptoms at least 5 years in duration, triple-artery disease, double-artery disease, and arteriosclerosis obliterans. A simple prognostic stratification was devised that used only ECGs and duration of symptoms for each subset based on the number of arteries affected.

Actuarial Analysis↗
PubMed1983

Analysis of test-retest variability in facial electroneurography.

Facial electroneurography is an objective electrophysiologic measurement of a muscle compound action potential used to assess prognosis for recovery from facial paralysis. In the present study, test precision is accompanied by a test-retest variability of 6.2%. The primary source of this variability is trigeminal nerve artifact, but submaximal nerve stimulation, changing skin resistance, and inherent nerve properties may also influence results. An ideal stimulus intensity that avoids patient discomfort and trigeminal nerve artifact but attains maximal nerve response is not possible in every patient.

Action Potentials↗
PubMed1982

Effects on labeling index as a predictor of response to chemotherapy in the 13762 adenocarcinoma.

A series of 24 experiments was carried out, in which treatment effect was determined in vivo on rats bearing measurable implants of 13762 adenocarcinoma treated with a variety of chemotherapeutic agents, alone or in combination. In 11 experiments, a reduction in mean tumor area was observed after treatment (response), while 13 showed no such effect (no response). For each experiment, cells from tumor-bearing animals were placed in suspension culture (10 experiments) or in two-layer soft-agar culture (14 experiments) after 24 h of exposure to drug-containing plasma or control plasma. Cells were harvested from cultures at 24-h intervals thereafter for determination of the thymidine labeling index in treated versus control populations. The sum of labeling indices in control plasma divided by that in treated plasma was determined to combine the available data over time (overall ratio). Critical values for this ratio were defined, which demonstrated significant depression of the labeling index. Significant labeling index depression occurred in nine of 11 experiments where response in vivo occurred, and in one of 13 in which no response was seen (P = 0.0004 by Fisher's exact test). When experiments carried out in soft agar culture or in suspension culture were examined separately, the association of labeling index depression in vitro and response in vivo remained statistically significant. In this model system, labeling index depression by drug-containing plasma is highly predictive of response to therapy.

Adenocarcinoma↗
PubMed1982

A case report of data monitoring experience: the nocturnal oxygen therapy trial.

The monitoring of accumulating data in a clinical trial is a challenging endeavor, yet one that must be undertaken to fulfill the ethical responsibility to the participating subject. This paper, using the Nocturnal Oxygen Therapy Trial as an example, discusses three issues often faced by data monitoring committees. These are (1) the multiplicity of outcomes, (2) decisions about extension of the patient recruitment period in order to achieve specified sample size goals, and (3) problems in monitoring survival data with a lag in the reporting of events. The decision process can be quite complex and existing statistical methodology can at best serve as a guide in this decision process.

Clinical Trials as Topic↗