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Biomedical subjects

L J Shaw

Publications and source records attributed to L J Shaw.

At least 55 records · Page 3Linked to original sources
PubMed1998

Influence of race on the prediction of cardiac events with stress technetium-99m sestamibi tomographic imaging in patients with stable angina pectoris.

The prognostic value of myocardial perfusion imaging in African-Americans is unknown. This study compared the prediction of cardiac events of stress technetium-99m (Tc-99m) sestamibi single-photon emission computed tomography (SPECT) imaging in symptomatic Caucasian and African-American patients. Prospectively collected stress Tc-99m sestamibi tomographic imaging data from 4 medical centers, with follow-up information in 1,086 Caucasian and African-American patients, were analyzed in a core statistical laboratory. Primary events of cardiac death and nonfatal myocardial infarction and secondary events of all-cause mortality were analyzed using Kaplan-Meier survival analysis and Cox proportional-hazards multivariable model. Normal images in both African-Americans and Caucasians were associated with a low-annual cardiac event rate, whereas abnormal images were significantly associated with a higher cardiac event rate. The highest predictor of cardiac events was multivessel abnormality in both races. Use of this technique could identify patients at high risk and potentially reduce the high-cardiac event rate in African-Americans by utilizing appropriate therapies.

Aged↗
PubMed1998

Comparative prognostic value of automatic quantitative analysis versus semiquantitative visual analysis of exercise myocardial perfusion single-photon emission computed tomography.

OBJECTIVES: The purpose of this study was to determine the prognostic value of automatic quantitative analysis in exercise dual-isotope myocardial perfusion single-photon emission computed tomography (SPECT) and to compare the prognostic value of quantitative analysis to semiquantitative visual SPECT analysis. BACKGROUND: Extent, severity and reversibility of exercise myocardial perfusion defects have been shown to correlate with prognosis. However, most studies examining the prognostic value of SPECT in chronic coronary artery disease (CAD) have been based on visual analysis by experts. METHODS: We studied 1,043 consecutive patients with known or suspected CAD who underwent rest Tl-201/exercise Tc-99m sestamibi dual-isotope myocardial perfusion SPECT and were followed up for at least 1 year (mean 20.0+/-3.7 months). After censoring 59 patients with early coronary artery bypass grafting or percutaneous transluminal coronary angioplasty, <60 days after nuclear testing, the final population consisted of 984 patients (36% women, mean age 63+/-12 years). RESULTS: During the follow-up period, 28 hard events (14 cardiac deaths, 14 nonfatal myocardial infarctions) occurred. Patients with higher defect extent (>10%), severity (>150) and reversibility (>5%) by quantitative SPECT defect analysis, as well as those with an abnormal scan (>2 abnormal segments, summed stress score >4 and summed difference score >2) by semiquantitative visual SPECT analysis, had a significantly higher hard event rate compared to patients with a normal scan (p < 0.001). With both visual and quantitative analyses, hard event rates of approximately 1% with normal scans and 5% with abnormal scans (p > 0.05) were observed over the 20-month follow-up period. A Cox proportional hazards regression model showed that chi-square increased similarly with the addition of quantitative defect extent and visual summed stress score variables after considering both clinical and exercise variables (improvement chi-square = 11 for both, p < 0.0007). There were no significant differences in the areas under receiver operating characteristic curves between quantitative and visual analysis (p > 0.70). Linear regression analysis also indicated that quantitative assessments correlated well with visual semiquantitative assessments. CONCLUSIONS: The findings of this study indicate that automatic quantitative analysis of exercise stress myocardial perfusion SPECT is similar to semiquantitative expert visual analysis for prognostic stratification. These findings may be of particular clinical importance in laboratories with less experienced visual interpreters.

Aged↗
PubMed1998

Prognosis by measurements of left ventricular function during exercise. Duke Noninvasive Research Working Group.

UNLABELLED: This study was performed to determine whether gated equilibrium radionuclide angiogram measurements of left ventricular function during rest and exercise add independent information to clinical and catheterization data in predicting cardiac death. METHODS AND RESULTS: The study population consisted of 863 consecutive patients undergoing exercise gated equilibrium radionuclide angiography within 90 days of cardiac catheterization with data prospectively entered into the Duke Cardiovascular Database. All patients were symptomatic, medically treated, with significant coronary artery disease and had undergone follow-up for < or = 6 yr. A univariable and multivariable Cox regression analysis was utilized to evaluate the independent power in predicting 147 (17.0%) cardiac deaths. This risk-adjusted analysis revealed that only rest and exercise ejection fraction as well as maximum workload contained independent prognostic information; the nuclear variables contributed 63% of the total information within the model. A multivariable model including exercise ejection fraction and clinical history variables provided slightly more prognostic information than the combination of cardiac catheterization and clinical data. CONCLUSION: Multigated equilibrium radionuclide angiography is a key predictor of cardiac death when compared to clinical and cardiac catheterization data in patients with symptomatic, medically treated coronary artery disease. Thus, long-term outcome for patients may be determined by utilizing this noninvasive tool even when clinical and cardiac catheterization data are also available.

Cardiac Catheterization↗
PubMed1997

Cost effectiveness of inpatient initiation of antiarrhythmic therapy for supraventricular tachycardias.

This study assessed the cost effectiveness of inpatient antiarrhythmic therapy initiation for supraventricular tachycardias using a metaanalysis of proarrhythmic risk and a decision analysis that compared inpatient to outpatient therapy initiation. A MEDLINE search of trials of antiarrhythmic therapy for supraventricular tachycardias was performed, and episodes of cardiac arrest, sudden or unexplained death, syncope, and sustained or unstable ventricular arrhythmias were recorded. A weighted average event rate, by sample size, was calculated and applied to a clinical decision model of therapy initiation in which patients were either hospitalized for 72 hours or treated as outpatients. Fifty-seven drug trials involving 2,822 patients met study criteria. Based on a 72-hour weighted average event rate of 0.63% (95% confidence interval, 0.2% to 1.2%), inpatient therapy initiation cost $19,231 per year of life saved for a 60-year-old patient with a normal life expectancy. Hospitalization remained cost effective when event rates and life expectancies were varied to model hypothetical clinical scenarios. For example, cost-effectiveness ratios for a 40-year-old without structural heart disease and a 60-year-old with structural heart disease were $37,510 and $33,310, respectively, per year of life saved. Thus, a 72-hour hospitalization for antiarrhythmic therapy initiation is cost effective for most patients with supraventricular tachycardias.

Anti-Arrhythmia Agents↗
PubMed1997

Usefulness of serial radionuclide angiography in predicting cardiac death after coronary artery bypass grafting and comparison with clinical and cardiac catheterization data.

This investigation assesses the prognostic value of radionuclide measurements of cardiac function in patients undergoing coronary artery bypass grafting (CABG). Radionuclide angiograms during exercise and at rest were obtained in 182 patients before (< or = 30 days), early (< or = 3 months), and late (< or = 3 years) after CABG. Cox proportional hazard regression analysis was used to identify independent predictors of 44 cardiac deaths that occurred a median 12 years after bypass. Although the exercise ejection fractions before and early after CABG were significantly related to subsequent cardiac death (chi-square = 10.84, p = 0.001, and chi-square = 7.4, p = 0.006, respectively), the late postoperative exercise ejection fraction was the strongest predictor (chi-square = 13.9, p = 0.0002), contributing above and beyond clinical and catheterization data. These data document the validity of the exercise ejection fraction as an important predictor of cardiac death after CABG and suggest the potential clinical application of serial measurements of the exercise ejection fraction as an important noninvasive adjunct to postoperative evaluation of these patients.

Cardiac Catheterization↗
PubMed1997

Risk stratification after myocardial infarction.

PURPOSE: To review the literature on risk stratification after acute myocardial infarction in the reperfusion era and to propose an algorithm for early and continual risk assessment. DATA SOURCES: A MEDLINE search of the English-language literature on humans was done using the terms myocardial infarction, prospective studies, and prognosis. This search was supplemented by narrowed searches for subheadings (such as cardiogenic shock, thrombolytic therapy, and stress testing) and surveys of references cited in review articles and book chapters. STUDY SELECTION: Literature on prognosis and myocardial infarction published from 1981 to 1996 was considered. From the literature on stress testing methods, studies that enrolled patients before 1980, enrolled patients for indications other than myocardial infarction, tested patients more than 6 weeks after infarction, were missing outcome data, or had inadequate follow-up were excluded. DATA EXTRACTION: Because too few randomized trials were available to allow the cross-comparison of risk-stratification methods, the available observational data were synthesized and supplemented with clinical judgments to produce recommendations. DATA SYNTHESIS: Risk stratification must begin when acute myocardial infarction is diagnosed. High-risk patients (such as those with cardiogenic shock) and candidates for reperfusion therapy must be identified quickly if ideal emergency care is to be given. At specific points during hospitalization, specialized tests may be useful if they add incremental information to the results of clinical evaluations. High-risk patients who have complications after infarction or significant left ventricular dysfunction probably benefit from early angiography; patients without these conditions are at low risk for recurrent events and should have noninvasive stress testing for further risk stratification. CONCLUSIONS: Physicians should continually reappraise risk throughout hospitalization to optimize both patient outcomes and cost containment.

Algorithms↗
PubMed1997

Impact of contrast echocardiography on diagnostic algorithms: pharmacoeconomic implications.

The major goal of medicine in the era of managed care is to control escalating costs and to attain a high level of quality health care. Capitation has limited access to expensive and unnecessary testing, placing an emphasis on the prudent use of available technology. A vast armamentarium of available diagnostic screening tests are available within cardiology. Routine two-dimensional (2-D) echocardiography is a high-quality, low-cost test that provides enhanced portability and real-time test interpretation over other noninvasive test modalities. The echocardiogram may cost up to 50% less than competitive nuclear single-photon emission computed tomography (SPECT) imaging. However, on average 10% of routine and 33% of stress echocardiograms are suboptimal (disproportionately affecting obese patients and those with lung disease). Myocardial contrast echocardiography has been shown to provide enhanced endocardial border delineation and left ventricular opacification, to enhance Doppler signal, and to provide information on myocardial perfusion. In several recent phase II and III studies, the use of a contrast agent has been shown to improve the diagnostic accuracy of echocardiography substantially. Improvements in the diagnostic capabilities of echocardiography have been shown to (1) impact upon downstream repetitive testing in patients with an initially nondiagnostic echocardiogram, (2) potentially increase laboratory throughput, and (3) reduce the rate of false-positive and negative tests as a result of improved image quality. As clinical and cost-effectiveness parallel one another, the use of myocardial contrast echocardiography in selected patient cohorts will result in improved diagnostic accuracy and a cost-effective pattern of care.

Albumins↗
PubMed1997

Cost implications of selective preoperative risk screening in the care of candidates for peripheral vascular operations.

The preoperative identification that patients are at high risk for adverse postoperative outcomes is the first step toward preventing costly in-hospital complications. The economic implications of noninvasive screening strategies in the care of patients undergoing peripheral vascular operations must be clarified. A decision model was developed from the peer-reviewed literature on patients undergoing preoperative screening by means of dipyridamole myocardial perfusion imaging, dobutamine echocardiography, or cardiac catheterization before vascular operations (n = 23 studies). Routine versus selective screening strategies were compared for patients with an intermediate likelihood of having coronary artery disease on the basis of clinical history of coronary disease or typical symptoms. Median costs (1994 US dollars) of preoperative screening strategies were derived with two microcosting approaches: adjusted Medicare charges (top-down approach) and a bottom-up approach with Duke University Center direct cost estimate data. In-hospital cost was 11% higher for preoperative screening by means of routine cardiac catheterization ($27,760) than for routine pharmacologic stress imaging ($24,826, P = 0.001). The total cost of a do-nothing strategy, that is, no preoperative testing, was 5.9% less than that of routine preoperative pharmacologic stress imaging and 15.9% lower than that of cardiac catheterization (P = 0.001). Selective screening among patients with a history of coronary disease or typical angina resulted in further reduction of the cost of care to a level comparable with that of a do-nothing strategy (52.5% reduction in cost with pharmacologic stress imaging, P > 0.20). Use of noninvasive testing for preoperative risk stratification was cost effective for patients 60 to 80 years of age. Cost per life saved ranged from $33,338 to $21,790. However, coronary revascularization after an abnormal noninvasive test was cost effective only for patients older than 70 years. In this economic decision model, substantial cost savings were predicted when selective noninvasive stress imaging was added to preoperative screening for patients about to undergo vascular operations. With a selective screening approach, the economic impact of initial diagnostic testing may be minimized without compromising patient outcomes.

Decision Trees↗
PubMed1996

A metaanalysis of predischarge risk stratification after acute myocardial infarction with stress electrocardiographic, myocardial perfusion, and ventricular function imaging.

We assessed the relation of abnormal predischarge non-invasive test results to outcomes in postmyocardial infarction patients. We included series published from 1980 to 1995 containing only myocardial infarction patients, enrolling most patients after 1980, testing within 6 weeks of infarction, having follow-up rates > 80%, and having 2 x 2 frequency outcome rates for test results, that were the latest of multiple reports. Sensitivity, specificity, and predictive values were calculated for test results for 1-year outcomes (cardiac death, cardiac death or reinfarction). Univariable and summary odds were calculated for test results. Reports (n = 54) included a total of 19,874 patients and were primarily retrospective (76%) and small series (35% of reports included < 5 deaths). One-year mortality ranged from 2.5% for pharmacologic stress echocardiography to 9.3% for exercise radionuclide angiography. Positive predictive values for most noninvasive risk markers were < 0.10 for cardiac death and < 0.20 for death or reinfarction. Electrocardiographic, symptomatic, and scintigraphic risk markers of ischemia (ST-segment depression, angina, a reversible defect) were less sensitive (< or = 44%) for identifying morbid and fatal outcomes than markers of left ventricular dysfunction or heart failure (exercise duration, impaired systolic blood pressure response, and peak left ventricular ejection fraction). The positive predictive value of predischarge noninvasive testing is low. Markers of left ventricular dysfunction appear to be better predictors than markers of ischemia. Limitations of the literature-small samples and widely varying event rates-impede our ability to discern the accuracy of pre-discharge noninvasive testing. More rigorous, controlled trials are required to elucidate the relative value of these tests for risk stratification.

Diagnostic Imaging↗
PubMed1996

Meta-analysis of intravenous dipyridamole-thallium-201 imaging (1985 to 1994) and dobutamine echocardiography (1991 to 1994) for risk stratification before vascular surgery.

OBJECTIVES: This study evaluated the prognostic value of abnormal test results with pharmacologic stress with regard to perioperative and long-term outcomes in a large population of candidates for vascular surgery. BACKGROUND: Although numerous studies have demonstrated the prognostic value of dipyridamole-thallium-201 myocardial perfusion and dobutamine echocardiography in vascular surgery candidates, a synopsis of predictive estimates is difficult because of individual study variability in pretest clinical risk, sample size and study design. METHODS: A systematic review of published reports on preoperative pharmacologic stress risk stratification from the MEDLINE data base (1985 to 1994) identified 10 reports on dipyridamole-thallium-201 myocardial perfusion (1,994 patients) and 5 on dobutamine stress echocardiography (446 patients). Random effects models were used to calculate summary odds ratios and 95% confidence intervals. RESULTS: Summary odds ratios for death or myocardial infarction and secondary cardiac end points were greater for dobutamine echocardiographic dyssynergy (14- to 27-fold) than for dipyridamole-thallium-201 redistribution (4-fold); wider confidence intervals were noted with dobutamine echocardiography. Pretest coronary disease probability was correlated with the positive predictive value of a reversible thallium-201 defect (r=0.70), increasing sixfold from low to high risk patient subsets. Cardiac event rates were low in patients without a history of coronary artery disease (1% in 176 patients) compared with patients with coronary disease and a normal or fixed-defect pattern (4.8% in 83 patients) and one or more thallium-201 redistribution abnormality (18.6% in 97 patients, p=0.0001). CONCLUSIONS: Meta-analysis of 15 studies demonstrated that the prognostic value of noninvasive stress imaging abnormalities for perioperative ischemic events is comparable between available techniques but that the accuracy varies with coronary artery disease prevalence.

Adrenergic beta-Agonists↗
PubMed1996

Prognostic value of cardiopulmonary exercise testing using percent achieved of predicted peak oxygen uptake for patients with ischemic and dilated cardiomyopathy.

OBJECTIVES: We tested the hypothesis that percent achieved of predicted peak oxygen uptake (predicted VO2max) improves the prognostic accuracy of identifying high risk ambulatory patients with congestive heart failure considered for heart transplantation compared with absolute peak oxygen uptake (VO2max) in 181 patients with ischemic or dilated cardiomyopathy. BACKGROUND: Peak oxygen uptake during exercise has been shown to be a useful prognostic measurement to risk stratify patients with heart failure. The prognostic value of percent predicted VO2max has not been assessed in these patients. METHODS: We retrospectively studied 181 ambulatory patients referred to the Saint Louis University Heart Failure Unit. Clinical, hemodynamic (137 patients) and coronary angiographic (145 patients) data were recorded, and all patients underwent symptom-limited cardiopulmonary exercise. RESULTS: During a mean follow-up period of 12 +/- 6 months, 26 patients died, and 18 were listed as Status 1 priority for heart transplantation. The actuarial 1- and 2-year survival of the 89 patients who achieved < or = 50% predicted VO2max was 74% and 43%, respectively, compared with 98% and 90% in the 92 who achieved > 50% predicted VO2max (p = 0.001). Multivariable analysis selected < or = 50% predicted VO2max as the most significant predictor of cardiac death (p = 0.007) and cardiac death or Status 1 priority (p = 0.0005). CONCLUSIONS: Percent achieved of predicted VO2max provides important information that can be used to risk stratify ambulatory patients with heart failure with ischemic or dilated etiology that exceeds that provided by measurement of VO2max alone. Patients who achieve > 50% predicted VO2max have an excellent short-term prognosis when treated medically, and heart transplantation can be safely deferred.

Cardiomyopathy, Dilated↗
PubMed1996

Periprocedural Doppler coronary blood flow predictors of myocardial perfusion abnormalities and cardiac events after successful coronary interventions.

Thirty-four consecutive patients had coronary flow velocity assessed under basal and hyperemic conditions in the proximal and distal coronary artery, followed by rest-stress technetium 99m sestamibi myocardial tomography within 3 months of successful coronary angioplasty. In spite of significant angiographic improvement, 29% of patients had a persistent reversible myocardial perfusion defect associated with a residual abnormality of the proximal-to-distal coronary average peak velocity ratio (p/d APV = 2.2 +/- 1.5 vs 1.1 +/- 0.6; p = 0.02). Patients with an abnormal p/d APV ratio (>1.7) had more numerous angioplasty-zone perfusion defects (4.2 +/- 3.3 vs 0.8 +/- 2.0; p = 0.005). Multivariable analysis of clinical, angiographic, coronary flow, and scintigraphic data demonstrated that the relative risk of cardiac events (n = 11) was greatest in patients with a reversible angioplasty-zone perfusion defect (relative risk, 5.5), poststenotic coronary flow reserve <2.0 (relative risk, 8.3) and p/d APV ratio >1.7 (relative risk, 6.2). Residual basal coronary flow-velocity abnormalities are significant physiologic correlates of stress-induced myocardial perfusion defects and are a prognostic covariable associated with future ischemic cardiac events.

Adult↗
PubMed1996

Prognostic value of noninvasive risk stratification in younger and older patients referred for evaluation of suspected coronary artery disease.

OBJECTIVES: The purpose of this investigation is to explore the relationship of patient gender and age on coronary artery disease diagnostic evaluation and to assess the impact of noninvasive testing results on coronary revascularization rates and cardiac event-free survival. STUDY DESIGN: Retrospective observational cohort. PARTICIPANTS: From a series of 5322 consecutively tested patients from a Midwestern university tertiary medical center, a hospital cohort of 1345 patients with clinically suspected coronary artery disease was enrolled from 1988 through 1989. MEASUREMENTS AND RESULTS: Cardiac risk factor and symptom profiles were worse in women, whereas rates of positive test results were similar in both sexes. Multivariable-adjusted risk for follow-up diagnostic testing was 1.8 and 1.9 times greater, respectively, for men < or = and > 65 years of age than for women (P < .01). Younger women were 4.9 times (P = .001) more likely to experience a cardiac event than younger men, with no differences between younger and older women (relative risk = 1.1; P > .20). Overall cardiac event rates were 2.3, 7.4, 16.7, and 20.2% for young men, young women, older women, and older men, respectively. Initial screening was delayed 2 to 7 times longer for older and younger women compared with men (P < .001); the greatest delays were observed for younger women. Diagnostic follow-up and subsequent cost of total care from initial evaluation through 2 years of follow-up were higher for men than for women (P < .0001), with older women having the lowest rate of subsequent diagnostic and interventional follow-up. In the highest risk patients, subsequent utilization rates were 40 and 20% higher for younger and older men than for similarly aged women. In particular, diabetics were less likely to undergo follow-up diagnostic testing and revascularization (67% younger women). CONCLUSIONS: Age appears to significantly and differently influence decisions regarding noninvasive and invasive medical service utilization in men and women and may partially account for variable outcomes in this and previous gender-based comparisons.

Adult↗
PubMed1994

Gender differences in the noninvasive evaluation and management of patients with suspected coronary artery disease.

OBJECTIVE: To determine if gender-based differences exist in the post-test management and clinical outcome of patients with clinically suspected coronary artery disease who have stress electrocardiographic or myocardial perfusion imaging evaluation. DESIGN: Retrospective cohort study. SETTING: University medical center. PATIENTS: From a cohort of 3975 middle-aged patients referred for outpatient stress testing, 840 (47% women) were evaluated noninvasively for clinically suspected coronary artery disease. MEASUREMENTS: The rates of subsequent diagnostic procedures and the incidence of subsequent coronary revascularization, myocardial infarction, or cardiac death were determined for women and men. RESULTS: Pretest cardiac risk profiles were similar, except hypertension and hypercholesterolemia were more frequent in women. Atypical angina was more common in women than in men (57.5% compared with 44.5%, respectively; P < 0.001). Rates of initial test positivity (defined as exercise-induced horizontal or downsloping ST-segment depression > or = 1.0 mm or > or = 1 reversible thallium-201 defect) were similar in women and men. Compared with men, most women with an initial positive test result had no additional coronary artery disease evaluation (62.3% compared with 38.0%; P = 0.002). Coronary revascularization procedures were done more frequently in men (4.9% [22 of 449] compared with 2.0% [8 of 391]; P = 0.03). Cardiac death or myocardial infarction occurred more often in women during 2 years of follow-up (6.9% [27 of 391] compared with 2.4% [11 of 449]; P = 0.002). CONCLUSIONS: Women with suspected coronary artery disease have fewer additional diagnostic tests than men after an initial abnormal noninvasive stress test result, even though the incidence of typical angina, cardiac risk factors, and initial diagnostic test positivity rates are similar.

Adult↗
PubMed1993

Impact of treatment strategy on predischarge exercise test in the Thrombolysis in Myocardial Infarction (TIMI) II Trial.

Predischarge supine bicycle ergometry was used to assess persistent myocardial ischemia in postinfarction patients who received thrombolytic therapy and were randomized to an invasive versus conservative strategy in the Thrombolysis in Myocardial Infarction (TIMI) II trial. The frequency of ischemic responses in both strategies, and the 1-year prognostic importance of the different exercise test outcomes were examined. At 14 days, the percentage of patients with any adverse outcome (including death, presence of exercise-induced ST-segment depression, or inability to perform the exercise test) was 33.7% of 1,681 randomly assigned to the invasive strategy compared with 34.6% of 1,658 randomly assigned to the conservative strategy (p = 0.57). The 1-year mortality was greater in patients who did not perform the predischarge exercise test (7.7%) than in those who did (1.8%) (p < 0.001); the former were older, and a greater proportion were women, had a more frequent history of myocardial infarction, and more extensive coronary artery disease (p < 0.01 for each comparison). The 1-year mortality in patients with exercise-induced ST-segment depression or chest pain was only 1.4% (3 of 22) among those randomly assigned to the conservative strategy where coronary angiography and revascularization were recommended if the test result was abnormal (relative risk compared with those without ST-segment depression or chest pain 0.6; 99% confidence interval 0.1 to 2.9).(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗