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L J Shaw

Publications and source records attributed to L J Shaw.

At least 19 recordsLinked to original sources
PubMed2000

Noninvasive strategies for the estimation of cardiac risk in stable chest pain patients. The Economics of Noninvasive Diagnosis (END) Study Group.

Effective allocation of medical resources in stable chest pain patients requires the accurate diagnosis of coronary artery disease and the stratification of future cardiac risk. We studied the relative predictive value for cardiac death of 3 commonly applied noninvasive strategies, clinical assessment, stress electrocardiography, and myocardial perfusion tomography, in a large, multicenter population of stable angina patients. The multicenter observational series comprised 7 community and academic medical centers and 8,411 stable chest pain patients. All patients underwent pretest clinical screening followed by stress (exercise 84% or pharmacologic 16%) electrocardiography and myocardial perfusion tomography. Risk-adjusted multivariable Cox proportional hazards models were developed to predict cardiac death. Kaplan-Meier rates of time to cardiac catheterization were also computed. Cardiac mortality was 3% during the 2.5 +/- 1.5 years of follow-up. The number of infarcted vascular territories and pretest clinical risk factors were strong predictors of cardiac mortality, whereas the number of ischemic vascular territories gained increasing importance when determining post-test resource use requirements (i.e., the decision to perform cardiac catheterization). Exertional ST-segment depression in a population with a high frequency of electrocardiographic abnormalities at rest was not a significant differentiator of cardiac death risk. Stable chest pain patients are accurately identified as being at high risk for near-term cardiac events by both physicians' screening clinical evaluation and by the results of stress myocardial perfusion imaging. Disease management strategies for stable chest pain patients aimed at risk reduction should incorporate knowledge of relevant end points in treatment and guideline development.

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PubMed2000

Contrast echocardiography: current and future applications.

Recent updates in the field of echocardiography have resulted in improvements in image quality, especially in those patients whose ultrasonographic (ultrasound) evaluation was previously suboptimal. Intravenous contrast agents are now available in the United States and Europe for the indication of left ventricular opacification and enhanced endocardial border delineation. The use of contrast enables acquisition of ultrasound images of improved quality. The technique is especially useful in obese patients and those with lung disease. Patients in these categories comprise approximately 10% to 20% of routine echocardiographic examinations. Stress echocardiography examinations can be even more challenging, as the image acquisition time factor is critically important for accurate detection of coronary disease. Improvements in image quality with intravenous contrast agents can facilitate image acquisition and enhance delineation of regional wall motion abnormalities at the peak level of exercise. Recent phase III clinical trial data on the use of Optison and several other agents (currently under evaluation) have revealed that for approximately half of patients, image quality substantively improves, which enables the examination to be salvaged and/or increases diagnostic accuracy. For the "difficult-to-image" patient, this added information results in (1) enhanced laboratory efficiency, (2) a reduction in downstream testing, and (3) possible improvements in patient outcome. In addition, substantial research efforts are underway to use ultrasound contrast agents for assessment of myocardial perfusion. The detection of myocardial perfusion during echocardiographic examinations will permit the simultaneous assessment of global and regional myocardial structure, function, and perfusion-all of the indicators necessary to enable the optimal noninvasive assessment of coronary artery disease. Despite the added benefit in improved efficacy of testing, few data exist regarding the long-term effectiveness of these agents. Currently under evaluation are the clinical and economic outcome implications of intravenous contrast agent use for daily clinical decision making in a variety of patient subsets. Until these data are known, this document offers a preliminary synthesis of available evidence on the value of intravenous contrast agents for use in rest and stress echocardiography. At present, it is the position of this guideline committee that intravenous contrast agents demonstrate substantial value in the difficult-to-image patient with comorbid conditions limiting an ultrasound evaluation of the heart. For such patients, the use of intravenous contrast agents should be encouraged as a means to provide added diagnostic information and to streamline early detection and treatment of underlying cardiac pathophysiology. As with all new technology, this document will require updates and revisions as additional data become available.

Contrast Media↗
PubMed2000

Economic aspects of transesophageal echocardiography and atrial fibrillation.

Cardiovascular disease is the leading cause of complications and death in the United States, affecting nearly 60 million Americans in 1998 and costing an estimated $274.2 billion. A major contributor to the costs of cardiovascular disease is atrial fibrillation (AF). AF is the most common sustained arrhythmia and affects > 2.2 million people and approximately 5% of all persons over the age of 60. Transesophageal echocardiography (TEE) with short-term anticoagulation has been proposed as a viable strategy to guide patients with AF. Here, we (1) review the current environmental context for a TEE-guided approach, (2) summarize the existing literature on the economic aspects of TEE, and (3) outline an economic framework for an economic analysis of TEE investigation or any major clinical therapy. We conclude that more powerful analytical tools are evolving to analyze the important economic, clinical, and social aspects of a patient's medical encounter.

Atrial Fibrillation↗
PubMed2000

Defining quality health care with outcomes assessment while achieving economic value.

The effectiveness of a procedure is increasingly guided by the evaluation of patient outcomes. Outcomes data is used to develop clinical pathways of care and to define appropriate resource-use levels without sacrificing quality of care. Integration of the economic implications of medical services into an outcome-based guideline allows for the development of disease-management strategies. In cardiovascular medicine, risk reduction is associated with high cost due to the "pay-back" of new technologies and therapies. A major challenge is to define a balance between "high tech" care and cost. This paper devises an outpatient evidence-based guideline using clinical and economic outcomes data for the diagnosis of coronary disease.

Cardiovascular Diseases↗
PubMed2000

Clinical and economic outcomes assessment in nuclear cardiology.

The future of nuclear medicine procedures, as understood within our current economic climate, depends upon its ability to provide relevant clinical information at similar or lower comparative costs. With an ever-increasing emphasis on cost containment, outcome assessment forms the basis of preserving the quality of patient care. Today, outcomes assessment encompasses a wide array of subjects including clinical, economic, and humanistic (i.e., quality of life) outcomes. For nuclear cardiology, evidence-based medicine would require a threshold level of evidence in order to justify the added cost of any test in a patient's work-up. This evidence would include large multicenter, observational series as well as randomized trial data in sufficiently large and diverse patient populations. The new movement in evidence-based medicine is also being applied to the introduction of new technologies, in particular when comparative modalities exist. In the past 5 years, we have seen a dramatic shift in the quality of outcomes data published in nuclear cardiology. This includes the use of statistically rigorous risk-adjusted techniques as well as large populations (i.e., > 500 patients) representing multiple diverse medical care settings. This has been the direct result of the development of multiple outcomes databases that have now amassed thousands of patients worth of data. One of the benefits of examining outcomes in large patient datasets is the ability to assess individual endpoints (e.g., cardiac death) as compared with smaller datasets that often assess combined endpoints (e.g., death, myocardial infarction, or unstable angina). New technologies for the diagnosis of coronary artery disease have contributed to the rising costs of care. In the United States and in Europe, costs of care have risen dramatically, consuming an ever-increasing amount of available resources. The overuse of diagnostic angiography often leads to unnecessary revascularization that does not lead to improvement in outcome. Thus, the potential exists that stress SPECT imaging, a highly effective diagnostic tool, could effect substantial change in reducing inappropriate use of an invasive procedure resulting in cost effective cardiac care. A synthesis of current economic evidence in gated SPECT imaging will be presented. In conclusion, a current state of the evidence review is presented on the clinical and economic data using nuclear cardiology imaging.

Angiography↗
PubMed2000

Hospital resource consumption in patients with diabetes and multivessel coronary disease undergoing revascularization.

OBJECTIVE: To identify factors responsible for the variation in real hospital costs and length of stay for patients with diabetes undergoing coronary angioplasty or coronary bypass surgery. STUDY DESIGN: Retrospective study of patients with diabetes and coronary artery disease treated at a single hospital. PATIENTS AND METHODS: The study population included 1809 patients with diabetes and multivessel (2-vessel or 3-vessel) coronary artery disease who underwent an initial coronary angioplasty or coronary bypass surgery between 1988 and 1996. After accounting for the extent and severity of the patient's coronary artery disease, a sequential model was used to assess if diabetic characteristics were independently associated with higher hospital resource utilization during revascularization. RESULTS: Multivariate regression results indicated that for patients with diabetes who underwent coronary angioplasty, a baseline creatinine level of > or = 2.0 mg/dL was associated with significantly higher hospital costs and longer length of stay. For patients with diabetes who underwent a coronary bypass surgery only, a baseline creatinine level of > or = 2.5 mg/dL was associated with higher hospital costs and longer hospital length of stay. CONCLUSIONS: After controlling for coronary risk factors, selected diabetes-specific characteristics are associated with higher hospital resource utilization. Risk adjustments in hospital reimbursement may be needed to assure that patients with diabetes who have cardiovascular disease have access to revascularization procedures.

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PubMed1999

Prognostic value of thallium-201 single-photon emission computed tomography for patients with multivessel coronary artery disease after revascularization (the Emory Angioplasty versus Surgery Trial [EAST]).

The aim of this study was to investigate the relation between reversible thallium single-photon emission computed tomography (SPECT) myocardial perfusion defects at 1-year after revascularization and quantitative indexes in Emory Angioplasty versus Surgery Trial (EAST) and outcomes 3 years after revascularization in 336 patients. EAST was a randomized controlled trial assessing cardiac outcomes for angioplasty versus bypass surgery for patients with multivessel coronary artery disease. During this prospective trial, a substudy included the evaluation of the prognostic value of reversible defects on quantitative thallium SPECT. At 1-year after revascularization, 336 patients underwent SPECT thallium-201 stress myocardial perfusion and 3-hour delayed imaging. Subsequent events, percutaneous transluminal coronary angioplasty, coronary artery bypass graft surgery, myocardial infarction, and death, were recorded at 3 years. A stress-induced reversible thallium-201 defect was defined using a quantitative index of a reversibility score >30% and severity score >500. Reversible defects were observed more frequently in the percutaneous transluminal coronary angioplasty than in the coronary artery bypass graft surgery treatment groups (46% vs 27%, p <0.001). A total of 123 patients had stress-induced, reversible thallium defects and more events than patients with other perfusion results (freedom from all events was 81.3% vs 94% [p <0.001], and freedom from myocardial infarction and death 88.3% vs 95.5% [p = 0.031]). Quantitative thallium SPECT at 1 year after revascularization risk stratifies patients as to their likelihood of major cardiac outcomes.

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PubMed1999

Early dipyridamole (99m)Tc-sestamibi single photon emission computed tomographic imaging 2 to 4 days after acute myocardial infarction predicts in-hospital and postdischarge cardiac events: comparison with submaximal exercise imaging.

BACKGROUND: Because of its brief hemodynamic effects and minor effect on determinants of myocardial oxygen demand, vasodilator stress myocardial perfusion imaging (MPI) can be applied very early after acute myocardial infarction (AMI) for risk stratification, allowing management decisions to be made earlier and thus potentially shortening hospitalization stays, reducing costs, and preventing early cardiac events. This multicenter randomized trial compared the prognostic value of early dipyridamole MPI and standard predischarge submaximal exercise MPI in patients who presented with AMI. METHODS AND RESULTS: Patients who presented with their first AMI (n=451) were randomized in a 3:1 ratio to undergo either both an early (day 2 to 4) dipyridamole (99m)Tc-sestamibi MPI study and a predischarge (day 6 to 12) submaximal exercise (99m)Tc-sestamibi MPI study or only the predischarge study. Multivariate predictors of in-hospital cardiac events included nuclear imaging summed stress and summed reversibility scores and peak creatine kinase. For postdischarge cardiac events, multivariate predictors in patients undergoing dipyridamole MPI included only the summed stress, reversibility, and rest imaging scores and anterior MI. For a given summed stress score, the interaction of reversibility score further improved the predictive value. Dipyridamole MPI showed better risk stratification than submaximal exercise MPI. CONCLUSIONS: Dipyridamole MPI very early after MI predicts early and late cardiac events, with superior prognostic value compared with submaximal exercise imaging. The extent and severity of the stress defect and reversibility of the defect were the most important predictors of cardiac death and recurrent MI. This technique can allow management decisions to be made earlier with regard to AMI patients and could have important economic impact if applied widely.

Dipyridamole↗
PubMed1999

The role of nuclear cardiology in clinical decision making.

This review suggests that the field of nuclear cardiology is alive, well, and thriving, providing relevant information that aids in everyday clinical decision making for nuclear medicine and referring physicians alike. Despite the competition from other modalities, the clinically appropriate applications of nuclear cardiology techniques are likely to increase. The foundation of this optimism is based on the vast amount of data documenting cost-effective clinical applications for diagnosis, risk stratification, and assessing therapy in both chronic and acute coronary artery disease (CAD), the powerful objective quantitative analysis of perfusion and function provided by the technique, and the increasing general availability of the approach.

Algorithms↗
PubMed1999

Incremental prognostic value of myocardial perfusion single photon emission computed tomography in patients with diabetes mellitus.

BACKGROUND: Previous studies have shown that myocardial perfusion single photon emission computed tomography (SPECT) provides incremental prognostic information in the general population, but the prognostic efficacy of nuclear testing in patients with diabetes mellitus is unclear. METHODS: We conducted a study with 1271 consecutively registered patients with diabetes and 5862 patients without diabetes with known or suspected coronary artery disease undergoing rest thallium 201/stress technetium 99m sestamibi dual-isotope myocardial perfusion SPECT with exercise or adenosine pharmacologic testing. Patients were followed up for at least 1 year. The successful follow-up rate was 92.4% for patients with diabetes and 94.0% for subjects without diabetes. The mean follow-up period was 23.7 +/- 7.7 months for the former group and 21.5 +/- 6.1 months for the latter. RESULTS: Over the follow-up period, patients with diabetes had significantly higher rates of hard events (cardiac death or nonfatal myocardial infarction) (4.3% per year versus 2.3% per year, P <.001) and higher total event rates (hard events and late revascularization) (9.0% per year versus 5.3% per year, P <. 001) compared with rates among patients without diabetes. Cox proportional hazards analysis revealed that nuclear testing added incremental value over clinical and historical variables among patients with diabetes (global chi(2) increased 46% for the exercise group [n = 619] and 88% for the adenosine group [n = 461]; both P <. 001). The event rates rose significantly as a function of summed stress score and summed difference score among both patients with diabetes and patients without diabetes (P <.001). The patients with diabetes with normal scans had relatively low hard event rates (1% to 2% per year), those with mildly abnormal scans had intermediate hard event rates (3% to 4% per year), and those with moderately to severely abnormal scans had relatively high hard event rates (>7% per year). CONCLUSIONS: The results of this study indicated that exercise and adenosine stress myocardial perfusion SPECT are valuable for risk stratification and management of patients with diabetes.

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PubMed1999

The noninvasive prediction of cardiac mortality in men and women with known or suspected coronary artery disease. Economics of Noninvasive Diagnosis (END) Study Group.

PURPOSE: The association between myocardial perfusion imaging defects and cardiac mortality in women is undefined. We examined whether myocardial perfusion imaging predicted cardiac mortality in men and women and compared this with other variables influencing prognosis. SUBJECTS AND METHODS: Six academic institutions with high-volume nuclear cardiology laboratories consecutively studied 5,009 men aged 62 +/- 12 years (mean ISD) and 3,402 women aged 66 +/- 11 years with symptomatic known or suspected coronary artery disease undergoing exercise (n = 7,486) or pharmacologic stress (n = 925) myocardial perfusion imaging. A pretest clinical risk index was calculated from age, history of myocardial infarction, diabetes, hypertension, and hypercholesterolemia. Myocardial perfusion images were analyzed for stress-induced defects or any defect in the territories of the three major coronary arteries. RESULTS: Stress-induced perfusion defects were seen in 39% of men and 25% of women (P = 0.0001). Extensive stress-induced or fixed defects (>2 vascular territories) were less common in women than men (10% vs 19%, and 4% vs 18%, both P = 0.0001). During a mean of 2.4 +/- 1.5 years of follow-up, 143 patients died of cardiac causes. The clinical risk index and number of territories with perfusion defects were associated with cardiac mortality in women and men. In women undergoing exercise myocardial perfusion imaging, the number of abnormal territories remained the strongest correlate of mortality after adjustment for exercise variables. CONCLUSIONS: The results of myocardial perfusion imaging are important, independent predictors of survival in both women and men.

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PubMed1999

The economic consequences of available diagnostic and prognostic strategies for the evaluation of stable angina patients: an observational assessment of the value of precatheterization ischemia. Economics of Noninvasive Diagnosis (END) Multicenter Study Group.

OBJECTIVES: The study aim was to determine observational differences in costs of care by the coronary disease diagnostic test modality. BACKGROUND: A number of diagnostic strategies are available with few data to compare the cost implications of the initial test choice. METHODS: We prospectively enrolled 11,372 consecutive stable angina patients who were referred for stress myocardial perfusion tomography or cardiac catheterization. Stress imaging patients were matched by their pretest clinical risk of coronary disease to a series of patients referred to cardiac catheterization. Composite 3-year costs of care were compared for two patients management strategies: 1) direct cardiac catheterization (aggressive) and 2) initial stress myocardial perfusion tomography and selective catheterization of high risk patients (conservative). Analysis of variance techniques were used to compare costs, adjusting for treatment propensity and pretest risk. RESULTS: Observational comparisons of aggressive as compared with conservative testing strategies reveal that costs of care were higher for direct cardiac catheterization in all clinical risk subsets (range: $2,878 to $4,579), as compared with stress myocardial perfusion imaging plus selective catheterization (range: $2,387 to $3,010, p < 0.0001). Coronary revascularization rates were higher for low, intermediate and high risk direct catheterization patients as compared with the initial stress perfusion imaging cohort (13% to 50%, p < 0.0001); cardiac death or myocardial infarction rates were similar (p > 0.20). CONCLUSIONS: Observational assessments reveal that stable chest pain patients who undergo a more aggressive diagnostic strategy have higher diagnostic costs and greater rates of intervention and follow-up costs. Cost differences may reflect a diminished necessity for resource consumption for patients with normal test results.

Angina Pectoris↗
PubMed1999

Development and characterization of a lux-modified 2,4-dichlorophenol-degrading Burkholderia sp. RASC.

lux-marked biosensors for assessing the toxicity and bioremediation potential of polluted environments may complement traditional chemical techniques. luxCDABE genes were introduced into the chromosome of the 2,4-dichlorophenol (2,4-DCP)-mineralizing bacterium, Burkholderia sp. RASC c2, by biparental mating using the Tn4431 system. Experiments revealed that light output was constitutive and related to cell biomass concentration during exponential growth. The transposon insertion was stable and did not interrupt 2,4-DCP-degradative genes, and expression of luxCDABE did not constitute a metabolic burden to the cell. A bioluminescence response was detectable at sublethal 2,4-DCP concentrations: at < 10.26 microg ml(-1), bioluminescence was stimulated (e.g. 218% of control), but at concentrations >60 microg ml(-1) it declined to < 1%. Investigating the effect of [14C]-2,4-DCP concentration on the evolution of 14CO2 revealed that, for initial concentrations of 2.5-25 microg ml(-1), approximately equals 55% of the added 14C was mineralized after 24 h compared with <1% at 50 and 100 microg ml(-1). Inhibition of 2,4-DCP mineralization between 25 and 50 microg ml(-1) corresponded well to the EC50 value (33.83 microg ml(-1)) obtained from bioluminescence inhibition studies. lux-marked RASC c2 may therefore be used as a functionally (i.e. 2,4-DCP degrader) and environmentally relevant biosensor of toxicity and biodegradation inhibition.

2,4-Dinitrophenol↗
PubMed1999

Using an outcomes-based approach to identify candidates for risk stratification after exercise treadmill testing.

OBJECTIVE: To develop a hierarchical approach to cardiac risk stratification after treadmill testing. PATIENTS: Clinical and treadmill test data were used to identify a patient population that may be candidates for further risk stratification with stress tomographic myocardial perfusion imaging. A prospective series of 3, 620 medically treated patients (42% female, mean age 63 years) with a 2.5% mortality was identified (follow-up 2.5 +/- SD 1.5 years). MEASUREMENTS AND MAIN RESULTS: A Cox proportional hazards model was used to estimate a patient's likelihood of cardiac death. Kaplan-Meier survival curves were used to estimate time to cardiac death by nuclear test results. Annual rates of cardiac death were 0. 4% (n = 921), 1% (n = 2,498), and 1% (n = 201) for patients with low, intermediate, and high Duke treadmill scores (DTS). For patients with an intermediate DTS, multivariate estimators of cardiac death included the number of ischemic vascular territories (relative risk per defect 1.4, p =.01), the number of infarcted vascular territories (relative risk per defect 2.4, p =.00001), and the DTS (relative risk per unit 0.97, p =.00001), following adjustment for a patient's pretest risk of coronary disease. For patients with an intermediate DTS, the presence of no, one or two, and three vascular territories with defects was associated with annual rates of cardiac death of 0.5%, 1.4%, and 2.5%, respectively (p <.0001). Kaplan-Meier survival curves exhibited a statistically worsening survival for patients with defects by 1 year after treadmill exercise. CONCLUSIONS: For symptomatic patients with an intermediate treadmill test score, the exercise myocardial perfusion scan may be used to stratify their risk of cardiac death over 3 years of follow-up. Patient management may be efficiently guided by further outcome assessment, with an exercise nuclear scan for patients whose treadmill test score is intermediate.

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