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Biomedical subjects

W D Weaver

Publications and source records attributed to W D Weaver.

At least 19 recordsLinked to original sources
PubMed1992

Influence of coronary bypass surgery on subsequent outcome of patients resuscitated from out of hospital cardiac arrest.

The effect of coronary bypass surgery on recurrent cardiac arrest was estimated in 265 patients resuscitated from out of hospital cardiac arrest between 1970 and 1988. From this cohort, 85 patients (32%) underwent coronary bypass surgery after recovery from cardiac arrest and 180 patients (68%) were treated medically. A multivariate Cox analysis was used to estimate the effect of coronary bypass surgery on subsequent survival after adjusting for effects of age, prior cardiac history, ejection fraction, year of the event, history of angina, antiarrhythmic drug use and whether the arrest was related to acute myocardial infarction. The use of coronary bypass surgery had a significant effect in reducing the incidence of subsequent cardiac arrest during follow-up study (risk ratio [RR] 0.48, 95% confidence interval [CI] 0.24 to 0.97, p less than 0.04). There was also a trend consistent with a reduction in total cardiac mortality (RR 0.65, 95% CI 0.39 to 1.10, p = 0.10). These findings suggest that coronary bypass surgery may reduce the incidence of sudden death in suitable patients resuscitated from an episode of ventricular fibrillation.

Cohort Studies↗
PubMed1992

The dilemma of sensitivity versus specificity in computer-interpreted acute myocardial infarction.

The use of thrombolytic therapy and out-of-hospital electrocardiogram (ECG) acquisition capability has put even greater importance on the diagnostic accuracy of computerized ECG interpretation programs. Such programs must have extremely high specificity to minimize the possibility of clinicians treating inappropriate patients; thereby needlessly subjecting the patients to the risk of potentially life-threatening complications of the medication. At the same time, studies have shown that both prehospital personnel and emergency department (ED) physicians are aided by automated ECG interpretation programs with high sensitivity. These programs assist the attending personnel in rapidly identifying patients with suspected acute coronary thrombosis, which might otherwise have been undetected or not diagnosed until more obvious ECG abnormalities were present. In previous studies, clinically correlated databases have been used to develop and test sensitivity and specificity of the acute infarction detection algorithm in the Marquette 12SL ECG interpretation program. One program revision resulted in a marked increase in sensitivity (21-53%) without loss of specificity (99.5% to 99%). More recent studies have shown the sensitivity of the interpretation program to be influenced greatly by infarct location with sensitivity lower in anterior than inferior injury. Further refinement of the acute infarction interpretation criteria along with the methodology and data used are presented. Increased sensitivity without appreciable loss of specificity has been possible for detection of both acute inferior and anterior infarction; however, different methods were used for each location. Consideration of reciprocal or concomitant repolarization changes are found to be more useful for inferior than anterior injury. Methodological approaches are presented as they relate to the compromise between sensitivity and specificity.

Algorithms↗
PubMed1992

Effect of early feed restriction on growth, feed conversion, and mortality in broiler chickens.

Two floor pen and two battery experiments were conducted to determine the effects of early feed restriction on the performance of commercial broilers. Feed restriction was induced in all experiments by providing chicks with 40 kcal of ME per bird per day, commencing at 4 days of age. Male chicks were feed-restricted for 7 (Experiments 1 and 2) or 6 days (Experiments 3 and 4), whereas broiler females were restricted for 5 days (Experiment 1). Ad libitum feeding was resumed after the restriction periods, and continued through the conclusion of the experiments at 49 (Experiments 1 and 2) or 28 (Experiments 3 and 4) days of age. Broilers provided ad libitum access to feed for the entire experimental period served as the controls in each study. Broilers subjected to an early feed restriction had significantly (p less than or equal to .05) lower mean body weights than controls for all ages measured in the four experiments. However, feed conversion ratios for restricted broilers were significantly lower at 28 (Experiments 1 through 4) and 49 (Experiments 1 and 2) days of age than for birds consuming feed ad libitum. Through regression analyses, it was estimated that male broilers in Experiments 1 and 2 would require approximately 2 additional days to obtain body weights similar to those observed in control broilers and would still maintain a lower feed conversion ratio at this older age. In Experiments 1 and 2, weekly body weight gains for restricted broilers were significantly lower than for controls from 0 through 28 days of age. However, restricted broilers (7 days) in Experiment 2 had significantly higher rates of gain from 29 to 49 days of age than unrestricted controls. Total pen body weights for restricted and ad libitum groups were similar at 49 days of age in Experiments 1 and 2, which reflected the significant difference in mortality observed between the two groups.

Age Factors↗
PubMed1992

Gender differences in the treatment and outcome of acute myocardial infarction. Results from the Myocardial Infarction Triage and Intervention Registry.

BACKGROUND: The objective of this study was to compare treatment and outcome of acute myocardial infarction in women and men. METHODS: In this survey, patient hospital records were reviewed, and information about patient characteristics, treatments, and hospital events was entered in the Myocardial Infarction Triage and Intervention Registry. Between January 1988 and June 1990, a total of 4891 consecutive patients, including 1659 women, were hospitalized for acute myocardial infarction in 19 hospitals in the Seattle (Wash) metropolitan area. In-hospital thrombolytic therapy, coronary angiography, angioplasty, and bypass surgery were examined, as were in-hospital complications and death. RESULTS: Women were older and more often had histories previous hypertension and previous congestive heart failure. Thrombolytic therapy was used less often in women, although information about eligibility for treatment was not available to determine if this difference was due to treatment bias or differences in eligibility. Both coronary angiography and coronary angioplasty were used less frequently in women. However, of patients who had coronary angiography, equal proportions of women and men received angioplasty and/or coronary bypass surgery. Hospital mortality was 16% for women and 11% for men, although this difference was diminished by age adjustment. Mortality was higher in women undergoing bypass surgery, but this difference, too, was less apparent after age adjustment. CONCLUSIONS: Despite high levels of risk factors and mortality, coronary angiography and angioplasty were used less often in women, although among those who underwent coronary angiography, there were no gender differences in the use of angioplasty or bypass surgery. Clearly, more needs to be known about decision making for coronary angiography, as this process seems to differ for women and men with acute myocardial infarction.

Aged↗
PubMed1992

Community-based interventions for sudden cardiac death. Impact, limitations, and changes.

Since 1970, Seattle Fire Department paramedics have treated 5,120 victims of out-of-hospital ventricular fibrillation (VF). During the past decade, there was an impressive decline in the annual incidence of VF, probably reflecting a general reduction in age-adjusted mortality attributed to coronary heart disease. Since 1975, annual survival rates to hospital discharge fluctuated between 24% and 33%, averaging 28.9%. In spite of continuing efforts to improve basic and advanced life support, survival rates have not risen concomitantly. Since the early 1970s, average ages of victims have increased from 63.4 to 66.1 years (p less than 0.0001). Additionally, in survivors of VF arrest, habitual cigarette smoking has become much less frequent (48% versus 31%, p less than 0.0001). Longevity of VF survivors has improved in recent years, with 1- and 5-year survival rates increasing from 74% and 44%, respectively, for those resuscitated during 1970-1975 to 83% and 57%, respectively, for those resuscitated during 1982-1987 (p less than 0.0001). It is likely that medical or surgical therapy and improved hygienic measures have contributed to the better outcomes. The vast majority of resuscitated victims have not had symptomatic ventricular arrhythmias before VF. Accordingly, current efforts to control such arrhythmias will not have an important impact on the community incidence of sudden cardiac death. Successful strategies for further containment will likely be those that address the problem of coronary atherogenesis, although medical and surgical therapies may also have a role. Additionally, it is timely to evaluate the widespread use of automated defibrillators by persons other than emergency medical technicians or paramedics.

Community Health Services↗
PubMed1991

An antiarrhythmic drug experience in 941 patients resuscitated from an initial cardiac arrest between 1970 and 1985.

Survival rates and antiarrhythmic drug use were determined in 941 consecutive patients resuscitated from prehospital cardiac arrest due to ventricular fibrillation between March 7, 1970, and March 6, 1985. Of these patients, 18.7% were treated for at least a portion of the period with quinidine, 17.5% with procainamide, and 39.4% received no antiarrhythmic agent. Beta blockers were prescribed for 28.3% of the patients. Unadjusted comparisons of survival estimates showed dramatically lower survival rates for patients who received antiarrhythmic drugs independent of beta-blocker therapy and significantly improved survival for patients receiving beta-blocker therapy independent of antiarrhythmic use. Patients for whom antiarrhythmic therapy was prescribed also had more adverse baseline risk factors, whereas patients taking beta blockers had fewer such risk factors. After adjustment for these baseline risk factors, the use of antiarrhythmics was weakly (p less than 0.09) associated with worsened survival; 2-year survival for procainamide-treated patients was 30% and quinidine-treated patients 55% (p = 0.003). Beta-blocker therapy was associated with improved (p less than 0.001) survival. Thus, although neither procainamide nor quinidine appear to have had a benefit on mortality, the effect of procainamide appears to be significantly worse than that of quinidine. The use of antiarrhythmic drug therapy in patients resuscitated from prehospital ventricular fibrillation should be regarded as not only unproved, but potentially hazardous, and should probably be restricted to testing in randomized clinical trials.

Anti-Arrhythmia Agents↗
PubMed1991

Accuracy of computer-interpreted electrocardiography in selecting patients for thrombolytic therapy. MITI Project Investigators.

A prehospital computer-interpreted electrocardiogram (ECG) was obtained in 1,189 patients with chest pain of suspected cardiac origin during an ongoing trial of prehospital thrombolytic therapy in acute myocardial infarction. Electrocardiograms were performed by paramedics 1.5 +/- 1.2 h after the onset of symptoms. Of 391 patients with evidence of acute myocardial infarction, 202 (52%) were identified as having ST segment elevation (acute injury) by the computer-interpreted ECG compared with 259 (66%) by an electrocardiographer (p less than 0.001). Of 798 patients with chest pain but no infarction, 785 (98%) were appropriately excluded by computer compared with 757 (95%) by an electrocardiographer (p less than 0.001). The positive predictive value of the computer- and physician-interpreted ECG was, respectively, 94% and 86% and the negative predictive value was 81% and 85%. Prehospital screening of possible candidates for thrombolytic therapy with the aid of a computerized ECG is feasible, highly specific and with further enhancement can speed the care of all patients with acute myocardial infarction.

Algorithms↗
PubMed1991

Effect of age on use of thrombolytic therapy and mortality in acute myocardial infarction. The MITI Project Group.

The findings in 3,256 consecutive patients hospitalized for acute myocardial infarction were tabulated to assess the history, treatments and outcome in the elderly; 1,848 patients (56%) were greater than 65 years of age, including 28% who were aged greater than or equal to 75 years. The incidence of prior angina, hypertension and heart failure (only 3% of patients less than 55 years of age had a history of heart failure compared with 24% greater than or equal to 75 years old) was found to increase with age. Twenty-nine percent of patients less than 75 years of age were treated with a systemic thrombolytic drug compared with only 5% of patients older than 75 years. Mortality rates increased strikingly with advanced age (less than 2% in patients less than or equal to 55, 4.6% in those 55 to 64, 12.3% in those 65 to 74 and 17.8% in those greater than or equal to 75 years). Both the incidence of complicating illness and a nondiagnostic electrocardiogram (ECG) increased with age. In a multivariate analysis of outcome in older patients (greater than or equal to 65 years), adverse events were related to both prior history of heart failure (odds ratio 3.9) and increasing age (odds ratio 1.4 per each decade of age). Outcome was not improved by treatment with thrombolytic drugs, but these agents were prescribed to only 12% of patients greater than 65 years of age, thereby reducing the power for detecting such an effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1991

The effect of different levels of relative humidity and air movement on litter conditions, ammonia levels, growth, and carcass quality for broiler chickens.

An experiment using 4,800 commercial broiler males (Ross x Ross) was conducted in 12 climatic chambers. Three levels of relative humidity (RH) (45, 40, to 80, and 75%) and two levels of internal air circulation (7.7 to 9.9 and 17.8 to 24.5 cm/s), with each level replicated and, therefore, forming a 3 x 2 x 2 factorial arrangement of treatments, arrangement of treatments, were imposed as the main effects. Broilers were group weighed and feed efficiencies calculated at 14, 28, and 42 days of age. Percentage dry matter of the litter and a subjective evaluation of general litter conditions (moisture and caking) were scored weekly, with the percentage nitrogen and total quality of litter produced in each chamber measured at the conclusion of the study. Ammonia levels were measured in each chamber every second day. A sample of birds (36) from each chamber was processed at 42 days and scored for litter spots and ammonia burns on the breast and for the incidence and severity of twisted legs, crooked toes, and infected and calloused hocks and foot pads. Mean body weight was significantly greater (32 g) at 42 days of age in birds exposed to 45% RH compared with the two higher regimens of RH. Both the incidence and severity of ammonia burns on the breast and infected foot pads were significantly higher with 75 versus 45% RH. Increases in RH significantly increased caking and litter moisture and reduced the percentage of dry matter and the percentage of nitrogen found in the litter. Ammonia levels were more variable but generally increased with increases in RH. The two levels of air movement within the chambers produced less influence on the environment than RH, although the scores for both litter moisture and caking were significantly lower with increased levels of internal air circulation.

Air Movements↗
PubMed1990

Time delays in the diagnosis and treatment of acute myocardial infarction: a tale of eight cities. Report from the Pre-hospital Study Group and the Cincinnati Heart Project.

To establish the magnitude of prehospital and hospital delays in initiating thrombolytic therapy for acute myocardial infarction, the time from telephone 911 emergency medical system (EMS) activation to treatment and its components were analyzed from eight separate ongoing trials. This included estimates of ambulance response time, prehospital evaluation and treatment time, and time from admission to the hospital to initiation of thrombolytic therapy. The average time from EMS activation to patient arrival at the hospital was prospectively determined to be 46.1 +/- 8.2 minutes in 3715 patients from eight centers. The time from admission to the hospital to initiation of thrombolytic therapy was retrospectively determined to be 83.8 +/- 55.0 minutes in a separate group of 730 patients from six centers. Both the prehospital and hospital time delays were much longer than those perceived by paramedics and emergency department directors. Shorter hospital time delays were observed in patients in whom a prehospital ECG was obtained as part of a protocol-driven prehospital diagnostic strategy and a diagnosis of acute infarction made before arrival at the hospital (36.3 +/- 11.3 minutes in 13 patients). These results show that the magnitude of time required to evaluate, transport, and initiate thrombolytic therapy will preclude initiation of treatment to most patients within the first hour of symptoms. Implementation of a protocol-driven prehospital diagnostic strategy may be associated with a reduction in time to thrombolytic therapy.

Electrocardiography↗
PubMed1990

Neonatally-induced thermotolerance: physiological responses.

1. Broiler cockerels exposed to neonatal heat (35-37.8 degrees C for 24 hr) at 5 days of age experienced significantly lower mortality upon exposure to elevated temperatures (35-37.8 degrees C) at 43 days of age than did cockerels not given neonatal heat exposure. 2. No differences were found between neonatally stressed and neonatal control groups in water consumption, core and surface temperature, plasma T3 and T4, protein or glucose concentration when exposed to juvenile heat stress. 3. Heterophil to lymphocyte ratios were significantly lower in the neonatally stressed than in the neonatal control group when exposed to heat at 44 days of age. 4. The results indicate that lower mortality during periods of high environmental temperature in the neonatally stressed chicks may involve homeostatic mechanisms different from those utilized during acclimation to high environmental temperature.

Adaptation, Physiological↗
PubMed1990

Myocardial Infarction Triage and Intervention Project--phase I: patient characteristics and feasibility of prehospital initiation of thrombolytic therapy.

Prehospital initiation of thrombolytic therapy by paramedics, if both feasible and safe, could considerably reduce the time to treatment and possibly decrease the extent of myocardial necrosis in patients with acute coronary thrombosis. Preliminary to a trial of such a treatment strategy, paramedics evaluated the characteristics of 2,472 patients with chest pain of presumed cardiac origin; 677 (27%) had suitable clinical findings consistent with possible acute myocardial infarction and no apparent risk of complication for potential thrombolytic drug treatment. Electrocardiograms (ECGs) of 522 of the 677 patients were transmitted by cellular telephone to a base station physician; 107 (21%) of the tracings showed evidence of ST segment elevation. Of the total 2,472 patients, 453 developed evidence of acute myocardial infarction in the hospital; 163 (36%) of the 453 had met the strict prehospital screening history and examination criteria and 105 (23.9%) showed ST elevation on the ECG and, thus, would have been suitable candidates for prehospital thrombolytic treatment if it had been available. The average time from the onset of chest pain to prehospital diagnosis was 72 +/- 52 min (median 52); this was 73 +/- 44 min (median 62) earlier than the time when thrombolytic treatment was later started in the hospital. Paramedic selection of appropriate patients for potential prehospital initiation of thrombolytic treatment is feasible with use of a directed checklist and cellular-transmitted ECG and saves time. This strategy may reduce the extent and complications of infarction compared with results that can be achieved in a hospital setting.

Adult↗