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Biomedical subjects

Lisa M Schwartz

Publications and source records attributed to Lisa M Schwartz.

At least 19 recordsLinked to original sources
PubMed2006

The value of both ST-segment and QRS complex changes during acute coronary occlusion for prediction of reperfusion-induced myocardial salvage in a canine model.

BACKGROUND: Analysis of ST-segment elevation for assessment of patients with suspected acute coronary occlusion is in widespread use for diagnostic and prognostic purposes. In this study, changes in the QRS complex also were analyzed to determine if these changes that are seldom used clinically can provide additional prognostic information. An acute coronary occlusion canine model, in which direct measurements of myocardial salvage were made, was used to assess whether ST-segment and QRS complex changes during coronary occlusion yielded independent estimates of the amount of salvage provided by reperfusion with arterial blood. METHODS AND RESULTS: Continuous electrocardiographic recordings were obtained from 14 study dogs undergoing a 90-minute period of coronary artery occlusion in which the severity of the ischemia during the occlusion was estimated at 10 and 45 minutes by microsphere injections. After 3 hours of reperfusion, the myocardium at risk and postmortem infarct size was measured. Myocardial salvage correlated inversely with both ST-segment elevation (r = -0.85; P < .0001), and QRS complex prolongation (r = -0.72; P = .003). When dogs were paired so that they had equal amounts of ST elevation but differed with respect to the presence of QRS prolongation, less myocardial salvage was found in those with QRS prolongation. The independent value of QRS prolongation was supported further by the observation that presence of QRS prolongation resulted in a loss of the highly significant correlation between ST elevation and salvage (r = -0.60; P = .2). CONCLUSIONS: High magnitudes of ST elevation are correlated significantly with less myocardial salvage. Moreover, for a given magnitude of ST elevation, the presence of concurrent QRS prolongation is associated with even less myocardial salvage.

Animals↗
PubMed2006

Ratio measures in leading medical journals: structured review of accessibility of underlying absolute risks.

OBJECTIVE: To examine the accessibility of absolute risk in articles reporting ratio measures in leading medical journals. DESIGN: Structured review of abstracts presenting ratio measures. SETTING: Articles published between 1 June 2003 and 1 May 2004 in Annals of Internal Medicine, BMJ, Journal of the American Medical Association, Journal of the National Cancer Institute, Lancet, and New England Journal of Medicine. PARTICIPANTS: 222 articles based on study designs in which absolute risks were directly calculable (61 randomised trials, 161 cohort studies). MAIN OUTCOME MEASURE: Accessibility of the absolute risks underlying the first ratio measure in the abstract. RESULTS: 68% of articles (150/222) failed to report the underlying absolute risks for the first ratio measure in the abstract (range 55-81% across the journals). Among these articles, about half did report the underlying absolute risks elsewhere in the article (text, table, or figure) but half did not report them anywhere. Absolute risks were more likely to be reported in the abstract for randomised trials compared with cohort studies (62% v 21%; relative risk 3.0, 95% confidence interval 2.1 to 4.2) and for studies reporting crude compared with adjusted ratio measures (62% v 21%; relative risk 3.0, 2.1 to 4.3). CONCLUSION: Absolute risks are often not easily accessible in articles reporting ratio measures and sometimes are missing altogether-this lack of accessibility can easily exaggerate readers' perceptions of benefit or harm.

Chi-Square Distribution↗
PubMed2006

GENTEX, a general multiscale model for in vivo tissue exchanges and intraorgan metabolism.

Endothelial cells lining myocardial capillaries not only impede transport of blood solutes to the contractile cells, but also take up and release substrates, competing with myocytes. Solutes permeating this barrier exhibit concentration gradients along the capillary. This paper introduces a generic model, GENTEX, to characterize blood-tissue exchanges. GENTEX is a whole organ model of the vascular network providing intraorgan flow heterogeneity and accounts for substrate transmembrane transport, binding and metabolism in erythrocytes, plasma, endothelial cells, interstitial space and cardiomyocytes. The model is tested here for the analysis of multiple tracer indicator dilution data on purine nucleoside metabolism in the isolated Krebs-Henseleit-perfused non-working hearts. It has been also used for analysing NMR contrast data for regional myocardial flows and for positron emission tomographic studies of cardiac receptor kinetics. The facilitating transporters, binding sites and enzymatic reactions are nonlinear elements and allow competition between substrates and a reaction sequence of up to five substrate-product reactions in a metabolic network. Strategies for application start with experiment designs incorporating inert reference tracers. For the estimation of endothelial and sarcolemmal permeability-surface area products and metabolism of the substrates and products, model solutions were optimized to fit the data from pairs of tracer injections (of either inosine or adenosine, plus the reference tracers) injected under the same circumstances a few minutes later. The results provide a self-consistent description of nucleoside metabolism in a beating well-perfused rabbit heart, and illustrate the power of the model to fit multiple datasets simultaneously.

Animals↗
PubMed2006

Media reporting on research presented at scientific meetings: more caution needed.

OBJECTIVE: To examine media stories on research presented at scientific meetings to see if they reported basic study facts and cautions, and whether they were clear about the preliminary stage of the research. DESIGN AND SETTING: Three physicians with clinical epidemiology training analysed front-page newspaper stories (n = 32), other newspaper stories (n = 142), and television/radio stories (n = 13) identified in LexisNexis and ProQuest searches for research reports from five scientific meetings in 2002-2003 (American Heart Association, 14th Annual International AIDS Conference, American Society of Clinical Oncology, Society for Neuroscience, and the Radiological Society of North America). MAIN OUTCOME MEASURES: Media reporting of basic study facts (size, design, quantification of results); cautions about study designs with intrinsic limitations (animal/laboratory studies, studies with < 30 people, uncontrolled studies, controlled but not randomised studies) or downsides (adverse effects in intervention studies); warnings about the preliminary stage of the research presented at scientific meetings. RESULTS: 34% of the 187 stories did not mention study size, 18% did not mention study design (another 35% were so ambiguous that expert readers had to guess the design), and 40% did not quantify the main result. Only 6% of news stories about animal studies mentioned their limited relevance to human health; 21% of stories about small studies noted problems with the precision of the finding; 10% of stories about uncontrolled studies noted it was not possible to know if the outcome really related to the exposure; and 19% of stories about controlled but not randomised studies raised the possibility of confounding. Only 29% of the 142 news stories on intervention studies noted the possibility of any potential downside. Twelve stories mentioned a corresponding "in press" medical journal article; two of the remaining 175 noted that findings were unpublished, might not have undergone peer review, or might change. CONCLUSIONS: News stories about scientific meeting research presentations often omit basic study facts and cautions. Consequently, the public may be misled about the validity and relevance of the science presented.

Congresses as Topic↗
PubMed2005

Ischemic postconditioning during reperfusion activates Akt and ERK without protecting against lethal myocardial ischemia-reperfusion injury in pigs.

Transient episodes of ischemic preconditioning (PC) render myocardium protected against subsequent lethal injury after ischemia and reperfusion. Recent studies indicate that application of short, repetitive ischemia only during the onset of reperfusion after the lethal ischemic event may obtain equivalent protection. We assessed whether such ischemic postconditioning (Postcon) is cardioprotective in pigs by limiting lethal injury. Pentobarbital sodium-anesthetized, open-chest pigs underwent 30 min of complete occlusion of the left anterior descending coronary artery and 3-h reflow. PC was elicited by two cycles of 5-min occlusion plus 10-min reperfusion before the 30-min occlusion period. Postcon was elicited by three cycles of 30-s reperfusion, followed by 30-s reocclusion, after the 30-min occlusion period and before the 3-h reflow. Infarct size (%area-at-risk using triphenyltetrazolium chloride macrochemistry; means +/- SE) after 30 min of ischemia was 26.5 +/- 5.2% (n = 7 hearts/treatment group). PC markedly limited myocardial infarct size (2.8 +/- 1.2%, n = 7 hearts/treatment group, P < 0.05 vs. controls). However, Postcon had no effect on infarct size (37.8 +/- 5.1%, n = 7 hearts/treatment group). Within the subendocardium, Postcon increased phosphorylation of Akt (74 +/- 12%) and ERK1/2 (56 +/- 10%) compared with control hearts subjected only to 30-min occlusion and 15-min reperfusion (P < or = 0.05), and these changes were not different from the response triggered by PC (n = 5 hearts/treatment group). Phosphorylation of downstream p70S6K was also equivalent in PC and Postcon groups. These data do not support the hypothesis that application of 30-s cycles of repetitive ischemia during reperfusion exerts a protective effect on pig hearts subjected to lethal ischemia, but this is not due to a failure to phosphorylate ERK and Akt during early reperfusion.

Animals↗
PubMed2005

How do elderly patients decide where to go for major surgery? Telephone interview survey.

OBJECTIVE: To learn how patients in Medicare, the US medical insurance programme that covers elderly patients, made decisions about where to undergo major surgery and how they would make future decisions. DESIGN: National telephone interview study. SETTING: United States. PARTICIPANTS: 510 randomly selected Medicare beneficiaries who had undergone an elective, high risk procedure about 3 years earlier--abdominal aneurysm repair (n = 103), heart valve replacement surgery (n = 96), or resection of the bladder (n = 119), lung (n = 128), or stomach (n = 64) for cancer. Response rates were 48% among eligible survivors and 68% among those able to participate. RESULTS: Although all participants could choose where to have surgery, only 55% said there was an alternative hospital in their area where they could have gone. Overall, only 10% of respondents seriously considered going elsewhere for surgery. Few respondents (11%) looked for information to compare hospitals. Almost all respondents thought their hospital and surgeon had good reputations (94% and 88%, respectively), beliefs mostly determined by what their referring doctors said. When asked how much various factors would influence their advice to a friend about choosing where to go for major surgery, surgeon reputation was the most influential (78% said it would influence their advice "a lot"), followed by the hospital having "nationally recognised" surgeons (63%), and then various performance data (surgeon volume (58%), nurse:patient ratios (49%), number of operations carried out by the hospital (48%), and hospital operative mortality (45%)). Forty per cent said they would act on mortality data, indicating that they would switch from their initial choice of hospital to a different one if its mortality was a percentage point lower (that is, 3% v 4%). CONCLUSION: Some respondents claimed they would switch hospital for elective surgery on the basis of mortality data. Since most respondents relied on their referring physician's opinion to decide where to have surgery, surgical performance data ought to be accessible to referring physicians.

Aged↗
PubMed2005

Skin biopsy rates and incidence of melanoma: population based ecological study.

OBJECTIVES: To describe changes in skin biopsy rates and to determine their relation with changes in the incidence of melanoma. DESIGN: Population based ecological study. SETTING: Nine geographical areas of the United States. PARTICIPANTS: Participants of the Surveillance Epidemiology and End Results (SEER) programme aged 65 and older. MAIN OUTCOME MEASURES: For the period 1986 to 2001, annual skin biopsy rates for each surveillance area from Medicare claims and incidence rates for melanoma for the same population. RESULTS: Between 1986 and 2001 the average biopsy rate across the nine participating areas increased 2.5-fold among people aged 65 and older (2847 to 7222 per 100,000 population). Over the same period the average incidence of melanoma increased 2.4-fold (45 to 108 per 100,000 population). Assuming that the occurrence of true disease was constant, the extra number of melanoma cases that were diagnosed after carrying out 1000 additional biopsies was 12.6 (95% confidence interval 11.2 to 14.0). After controlling for a potential increase in the true occurrence of disease, 1000 additional biopsies were still associated with 6.9 (3.1 to 10.8) extra melanoma cases diagnosed. Stage specific analyses suggested that 1000 biopsies were associated with 4.4 (2.1 to 6.8) extra cases of in situ melanoma diagnosed and 2.3 (0.0 to 4.6) extra cases of local melanoma, but not with the incidence of advanced melanoma. Mortality from melanoma changed little during the period. CONCLUSION: The incidence of melanoma is associated with biopsy rates. That the extra cases diagnosed were confined to early stage cancer while mortality remained stable suggests overdiagnosis-the increased incidence being largely the result of increased diagnostic scrutiny and not an increase in the incidence of disease.

Aged↗
PubMed2005

Prostate-specific antigen levels in the United States: implications of various definitions for abnormal.

BACKGROUND: The finding that some men with a normal prostate-specific antigen (PSA) level (i.e., less than 4 ng/mL) nonetheless have microscopic evidence of prostate cancer has led to some suggestions that the threshold defining abnormal should be lowered to 2.5 ng/mL. We examined the effect of this lower threshold on the number of American men who would be labeled abnormal by a single PSA test. METHODS: We obtained PSA data on a nationally representative sample of American men 40 years of age and older with no history of prostate cancer and no current inflammation or infection of the prostate gland (n = 1308) from the 2001-2002 National Health and Nutrition Examination Survey. We obtained data on the 10-year risk of prostate cancer death in the pre-PSA era from DevCan, the National Cancer Institute's software to calculate the probability of dying of cancer. RESULTS: Based on NHANES data, approximately 1.5 million American men aged 40 to 69 years have a PSA level over 4.0 ng/mL. Lowering the threshold to 2.5 ng/mL would label an additional 1.8 million men as abnormal, if all men were screened. For men aged 70 years or older, the corresponding numbers are 1.5 and 1.2 million. The proportion of the population affected by different thresholds would vary with age. Among men in their 60s, for example, 17% have a PSA level over 2.5 ng/mL, 5.7% have a PSA level over 4.0 ng/mL, and 1.7% have a PSA level over 10.0 ng/mL. For context, only 0.9% of men in their 60s are expected to die from prostate cancer in the next 10 years. CONCLUSION: Lowering the PSA threshold to 2.5 ng/mL would double the number of men defined as abnormal, to up to 6 million. Until there is evidence that screening is effective, increasing the number of men recommended for prostate biopsy--and the number potentially diagnosed and treated unnecessarily--would be a mistake.

Adult↗
PubMed2005

Celebrity endorsements of cancer screening.

Celebrities often promote cancer screening by relating personal anecdotes about their own diagnosis or that of a loved one. We used data obtained from a random-digit dialing survey conducted in the United States from December 2001 through July 2002 to examine the extent to which adults of screening age without a history of cancer had seen or heard or been influenced by celebrity endorsements of screening mammography, prostate-specific antigen (PSA) testing, or sigmoidoscopy or colonoscopy. The survey response rate was 72% among those known to be eligible and 51% among potentially eligible people accounting for those who could not be contacted. A total of 360 women aged 40 years or older and 140 men aged 50 years or older participated in the survey. Most respondents reported they "had seen or heard a celebrity talk about" mammography (73% of women aged 40 years or older), PSA testing (63% of men aged 50 years or older), or sigmoidoscopy or colonoscopy (52% of adults aged 50 years or older). At least one-fourth of respondents who had seen or heard a celebrity endorsement said that the endorsement made them more likely to undergo mammography (25%), PSA testing (31%), or sigmoidoscopy or colonoscopy (37%).

Adult↗
PubMed2005

Advertising by academic medical centers.

BACKGROUND: Many academic medical centers have increased their use of advertising to attract patients. While the content of direct-to-consumer pharmaceutical advertisements (ads) has been studied, to our knowledge, advertising by academic medical centers has not. We aimed to characterize advertising by the nation's top academic medical centers. METHODS: We contacted all 17 medical centers named to the US News & World Report 2002 honor roll of "America's Best Hospitals" for a semistructured interview regarding their advertising practices. In addition, we obtained and systematically analyzed all non-research-related print ads placed by these institutions in their 5 most widely circulating local newspapers during 2002. RESULTS: Of the 17 institutions, 16 reported advertising to attract patients; 1 stated, "We're just word of mouth." While all 17 centers confirmed the presence of an institutional review board process for approving advertising to attract research subjects, none reported a comparable process for advertising to attract patients. We identified 127 unique non-research-related print ads for the 17 institutions during 2002 (mean, 7.5; range, 0-39). Three ads promoted community events with institution sponsorship, 2 announced genuine public services, and 122 were aimed at attracting patients. Of the latter group, 36 ads (29.5%) promoted the medical center as a whole, while 65 (53.3%) promoted specific clinical departments and 21 (17.2%) promoted single therapeutic interventions or diagnostic tests. The most commonly used marketing strategies included appealing to emotions (61.5%), highlighting institution prestige (60.7%), mentioning a symptom or disease (53.3%), and promoting introductory lectures or special offers likely to lead to further business (47.5%). Of the 21 ads for single interventions, most were for unproved (38.1%) or cosmetic (28.6%) procedures. While more than half of these ads presented benefits, none quantified their positive claims and just 1 mentioned potential harms. CONCLUSIONS: Advertising to attract patients is common among top academic medical centers but is not subjected to the oversight standard for clinical research. Many of the ads seemed to place the interests of the medical center before the interests of the patients.

Academic Medical Centers↗
PubMed2005

Screening for cervical cancer: will women accept less?

BACKGROUND: U.S. professional organizations increasingly agree that most women require Papanicolaou smear screening every 2 to 3 years rather than annually and that most elderly women may stop screening. We sought to describe the attitudes of women in the United States toward less intense screening, specifically, less frequent screening and eventual cessation of screening. METHODS: We conducted a random-digit-dialing telephone survey of women in 2002 (response rate of 75% among eligible women reached by telephone). A nationally representative sample of 360 women aged 40 years or older with no history of cancer was surveyed about their acceptance of less intense screening. RESULTS: Almost all women aged 40 years or older (99%) had had at least one Pap smear; most (59%) were screened annually. When women were asked to choose their preferred frequency for screening, 75% preferred screening at least annually (12% chose screening every 6 months). Less than half (43%) had heard of recommendations advocating less frequent screening. When advised of such recommendations, half of all women believed that they were based on cost. Sixty-nine percent said that they would try to continue being screened annually even if their doctors recommended less frequent screening and advised them of comparable benefits. Only 35% of women thought that there might come a time when they would stop getting Pap smears; of these, almost half would not stop until after age 80 years. The strongest predictor of reluctance to reduce the frequency of screening was a belief that cost was the basis of current screening frequency recommendations. CONCLUSION: Most women in the United States prefer annual Pap smears and are resistant to the idea of less intense screening. Concern that cost considerations rather than evidence form the basis of screening recommendations may partly explain women's reluctance to accept less intense screening.

Age Factors↗