Peripheral arterial responses to treadmill exercise among healthy subjects and atherosclerotic patients.

UNLABELLED: BACKGROUND-Peripheral cutaneous vascular beds, such as the fingertips, contain a high concentration of arteriovenous anastomoses, richly innervated by a-adrenergic nerve fibers, to control heat regulation. Nevertheless, for a variety of technical reasons, finger blood flow responses to exercise have not been well studied in health and disease. Hence, we compared finger pulse-wave amplitude (PWA) responses to exercise among 50 normal volunteers and 57 patients with atherosclerotic coronary artery disease (CAD) using a robust, modified form of volume plethysmography. METHODS AND RESULTS: PWA was quantified for each minute of exercise as a ratio relative to baseline. Exercise PWA responses were compared with clinical, hemodynamic, ECG, and myocardial single photon emission computed tomography parameters. Among normal subjects, 38 (76%) manifested vasodilation throughout exercise and 12 (24%) manifested initial vasodilation followed by vasoconstriction at high heart rate thresholds. None manifested vasoconstriction throughout exercise. By contrast, 20 CAD patients (35%) manifested progressive vasoconstriction from the onset of exercise, and 10 others (18%) manifested vasoconstriction at low heart rate thresholds (P < 0.001 versus normals) after initial vasodilation with exercise. Patients exhibiting vasodilation versus vasoconstriction during exercise had similar clinical and exercise profiles, except for a greater use of ACE inhibitors and a greater level of achieved metabolic equivalents among the former (P<0.05 for both). CONCLUSIONS: Half of our CAD patients manifested diminution in PWA that was consistent with peripheral arterial vasoconstriction during the early phases of treadmill exercise. Such paradoxical vasoconstrictive responses were not observed in normal subjects and, therefore, they may represent generalized vascular pathology secondary to atherosclerosis.

Intensity of antianginal therapy in patients referred for coronary angiography: a comparison of fee-for-service and health maintenance organization therapeutic strategies.

BACKGROUND: No formal criteria have been developed to guide medical therapy for angina prior to revascularization, and no comparisons have been made between health maintenance organization (HMO) and fee-for-service (FFS) hospitals with respect to angina treatment. HYPOTHESIS: Using a literature-based measure of medical intensity, we tested the hypothesis that there is no difference in anginal medical therapeutic intensity between HMO and FFS systems. METHODS: For each antianginal drug, we developed a model from which an intensity score between 0 and 100 could be calculated. Average and maximal daily doses of drug were fit to a sigmoid curve such that they represented scores of 50 and 99, respectively. Overall intensity scores were obtained by weighted and unweighted averaging of three scores from nitrates, calcium-channel blockers, and beta blockers. This model was applied to 199 patients undergoing angiography at an FFS and an HMO hospital. RESULTS: HMO patients were taking more classes of antianginal drug (1.9 vs. 1.0, p < 0.001). Overall unweighted (17.7 vs. 11.7, p = 0.02) and weighted (27.3 vs. 16.9, p = 0.003) intensity scores for both HMO and FFS patients were low. HMO intensity scores for the use of beta blockers were greater than FFS scores (19.2 vs. 9.6, p = 0.002). The intensity scores for the use of nitrates and calcium blockers were similar. CONCLUSIONS: Models for the measurement of anginal medical therapy intensity can provide important information regarding medical therapy prior to revascularization. The overall intensity of medical therapy was low in both health care systems. These findings have important implications for patient management, guideline development, and national healthcare policy.

Incremental prognostic value of myocardial perfusion single photon emission computed tomography for the prediction of cardiac death: differential stratification for risk of cardiac death and myocardial infarction.

BACKGROUND: The incremental prognostic value of stress single photon emission computed tomography (SPECT) for the prediction of cardiac death as an individual end point and the implications for risk stratification are undefined. METHODS AND RESULTS: We identified 5183 consecutive patients who underwent stress/rest SPECT and were followed up for the occurrence of cardiac death or myocardial infarction. Over a mean follow up of 642+/-226 days, 119 cardiac deaths and 158 myocardial infarctions occurred (3.0% cardiac death rate, 2.3% myocardial infarction rate). Patients with normal scans were at low risk (< or =0.5%/y), and rates of both outcomes increased significantly with worsening scan abnormalities. Patients who underwent exercise stress and had mildly abnormal scans had low rates of cardiac death but higher rates of myocardial infarction (0.7%/y versus 2.6%/y; P<.05). After adjustment for prescan information, scan results provided incremental prognostic value toward the prediction of cardiac death. The identification of patients at intermediate risk of nonfatal myocardial infarction and low risk for cardiac death by SPECT may result in significant cost savings when applied to a clinical testing strategy. CONCLUSIONS: Myocardial perfusion SPECT yields incremental prognostic information toward the identification of cardiac death. Patients with mildly abnormal scans after exercise stress are at low risk for cardiac death but intermediate risk for nonfatal myocardial infarction and thus may benefit from a noninvasive strategy and may not require invasive management.

Incremental prognostic value of adenosine stress myocardial perfusion single-photon emission computed tomography and impact on subsequent management in patients with or suspected of having myocardial ischemia.

We examined 1,159 consecutive patients who underwent adenosine stress dual isotope single-photon emission computed tomography (SPECT) and had follow-up performed at a mean of 27.5 +/- 9.1 months (94% complete) for hard events (cardiac death and myocardial infarction) and referral to cardiac catheterization after nuclear testing. During follow-up, 120 hard events occurred (11.0% hard event rate; 72 cardiac deaths [6.7% cardiac death rate] and 57 myocardial infarctions [5.3% myocardial infarction rate]). Cox proportional hazards analysis revealed that nuclear testing added incremental value after adjusting for clinical and historical variables (global chi-square increased 13 to 98 for cardiac death as the end point, global chi-square increased 19 to 105 for hard events as the end point; p <0.0001 for both). Kaplan-Meier analysis demonstrated that after clinical risk stratification of the patient population, the results of nuclear testing were further able to significantly stratify both low- and intermediate- to high-risk patients. Patients with both normal and mildly abnormal scans were at low risk of cardiac death (<1% cardiac death per year of follow-up) and the risk of events increased significantly with worsening scan result. Multivariable analysis revealed that the only predictor of referral to catheterization was the extent and severity of reversible defect present on the scan. Referral rates to early catheterization were very low in patients with normal scans and increased significantly as a function of worsening scan results. In patients who underwent myocardial perfusion SPECT using adenosine stress, the results of nuclear testing yielded incremental prognostic information and clinically relevant risk stratification. Referring physicians predominantly utilized nuclear information when referring patients to catheterization after nuclear testing and do so at rates comparable with those after exercise SPECT despite the higher risk of events in patients undergoing pharmacologic stress.

Effective risk stratification using exercise myocardial perfusion SPECT in women: gender-related differences in prognostic nuclear testing.

OBJECTIVES: This study was designed to evaluate the incremental prognostic value over clinical and exercise variables of rest thallium-201/exercise technetium-99m sestamibi single-photon emission computed tomography (SPECT) in women compared with men and to determine whether this test can be used to effectively risk stratify patients of both genders. BACKGROUND: To minimize the previously described gender-related bias in the evaluation of coronary artery disease in women, there is a need to identify a noninvasive testing strategy that is able to accurately and effectively risk stratify women. METHODS: We identified 4,136 consecutive patients (2,742 men, 1,394 women) who underwent dual-isotope SPECT. The incremental value of nuclear testing was determined using both a stepwise Cox proportional hazards model and Kaplan-Meier survival analysis. Receiver operating characteristic curve analysis was performed to determine test discrimination for high risk patients in men and women. RESULTS: The patient population was followed up for 20 +/- 5 months for events (cardiac death or nonfatal myocardial infarction). During this time, 63 myocardial infarctions and 32 cardiac deaths occurred in the men, and 31 myocardial infarctions and 14 cardiac deaths occurred in the women. Nuclear testing significantly stratified both men and women irrespective of their rest electrocardiogram. Cox proportional hazards analysis revealed that nuclear testing added incremental prognostic value in both men and women after inclusion of the most predictive clinical exercise variables (overall chi-square 89 in men vs. 120 in women, p < 0.005). Kaplan-Meier survival analysis demonstrated that nuclear testing further stratified men and women with both intermediate to high and low prescan likelihoods of coronary artery disease (p < 0.005 for all). Receiver operating characteristic curve analysis demonstrated superior discrimination for the nuclear scan results in identifying high risk women than men (area under the curve: 0.84 +/- 0.03 vs 0.71 +/- 0.03 in men, p < 0005). The odds ratio comparing event rates in patients with women than in men, suggesting superior stratification using nuclear testing in women. CONCLUSIONS: Dual-isotope myocardial perfusion imaging yields incremental prognostic value in both men and women. This modality identifies low risk women and men equally well but relatively high risk women more accurately than relatively high risk men and, thus, is able to stratify women more effectively than men.

The effect of disease-prevalence adjustments on the accuracy of a logistic prediction model.

The accuracy of a logistic prediction model is degraded when it is transported to populations with outcome prevalences different from that of the population used to derive the model. The resultant errors can have major clinical implications. Accordingly, the authors developed a logistic prediction model with respect to the noninvasive diagnosis of coronary disease based on 1,824 patients who underwent exercise testing and coronary angiography, varied the prevalence of disease in various "test" populations by random sampling of the original "derivation" population, and determined the accuracy of the logistic prediction model before and after the application of a mathematical algorithm designed to adjust only for these differences in prevalence. The accuracy of each prediction model was quantified in terms of receiver operating characteristic (ROC) curve area (discrimination) and chi-square goodness-of-fit (calibration). As the prevalence of the test population diverged from the prevalence of the derivation population, discrimination improved (ROC-curve areas increased from 0.82 +/- 0.02 to 0.87 +/- 0.03; p < 0.05), and calibration deteriorated (chi-square goodness-of-fit statistics increased from 9 to 154; p < 0.05). Following adjustment of the logistic intercept for differences in prevalence, discrimination was unchanged and calibration improved (maximum chi-square goodness-of-fit fell from 154 to 16). When the adjusted algorithm was applied to three geographically remote populations with prevalences that differed from that of the derivation population, calibration improved 87%, while discrimination fell by 1%. Thus, prevalence differences produce statistically significant and potentially clinically important errors in the accuracy of logistic prediction models. These errors can potentially be mitigated by use of a relatively simple mathematical correction algorithm.

Statistical, epidemiological and fiscal issues in the evaluation of patients with coronary artery disease.

The application of myocardial perfusion scintigraphy to patient care in the era of health care cost containment is a difficult issue. The traditional diagnosis based approach to testing, although effective, is incompletely applied, as evidenced by the number of low likelihood of coronary artery disease patients referred for testing. A prognosis- or risk-based testing approach may be applied to both patients with or without known coronary artery disease by utilizing clinical and scan information to estimate the projected risk of adverse outcomes (cardiac death or myocardial infarction) and planning subsequent patient strategy based upon this estimate. Patients at high risk for these events are more likely to benefit from referral to catheterization while those patients at lower risk may benefit from medical therapy alone. Irrespective of the approach utilized to evaluate testing, consideration of patient population selection and its implications must be considered when reviewing the results of testing or published literature. Further, scrutiny of both the statistical methods used for evaluation of the value of testing and the economic implications of testing in particular patient subgroups are of importance.

Exercise myocardial perfusion SPECT in patients without known coronary artery disease: incremental prognostic value and use in risk stratification.

BACKGROUND: We evaluated the incremental prognostic value, the role in risk stratification, and the impact on patient management of myocardial perfusion single-photon emission computed tomography (SPECT) in a population of patients without prior myocardial infarction, catheterization, or revascularization. METHODS AND RESULTS: We examined 2200 consecutive patients who at the time of their dual-isotope SPECT had not undergone catheterization, coronary artery bypass surgery, or percutaneous transluminal coronary angioplasty and had no known history of previous myocardial infarction. Follow-up was performed at a mean of 566 +/- 142 days (97% complete) for hard events (cardiac death and myocardial infarction) and for referral to cardiac catheterization or revascularization within 60 days after nuclear testing. Examination of clinical, exercise, and nuclear models by use of pre-exercise tolerance test (ETT), post-ETT, and nuclear information using a stepwise Cox proportional hazards model and receiver-operating characteristic curve analysis revealed that nuclear testing added incremental prognostic value after inclusion of the most predictive clinical and exercise variables (global chi2 = 12 for clinical variables; 31 for clinical + exercise variables; 169 for nuclear variables; gain in chi2, P < .0001 for all; receiver-operating characteristic areas: 0.66 +/- 0.04 for clinical, 0.73 +/- 0.04 for clinical + exercise variables, 0.87 +/- 0.03 for nuclear variables, P = .03 for gain in area with exercise variables; P < .001 for increase with nuclear variables). Multiple logistic regression analysis revealed that scan information contributed 95% of the information regarding referral to catheterization with further additional information provided by presenting symptoms and exercise-induced ischemia. Referral rates to early catheterization and revascularization paralleled the hard event rates in all scan categories - very low referral rates in patients with normal scans and significant increases in referral rates as a function of worsening scan results. Even after stratification by clinical and exercise variables such as the Duke treadmill score, pre- and post-ETT likelihood of coronary artery disease, presenting symptoms, sex, and age, the nuclear scan results further risk-stratified the patient subgroups, thus demonstrating clinical incremental value. CONCLUSIONS: In a patient population with no evidence of previous coronary artery disease at overall low risk (1.8% hard event rate), myocardial perfusion SPECT adds incremental prognostic information and risk-stratifies patients even after clinical and exercise information is known. It appears that referring physicians use this test in an appropriate manner in selecting patients to be referred to catheterization or revascularization.

Gender-related differences in clinical management after exercise nuclear testing.

OBJECTIVES: This study sought to determine the rate of referral to cardiac catheterization in men and women early after nuclear testing as a function of the magnitude of myocardial ischemia by radionuclide perfusion imaging. BACKGROUND: Although many previous studies have suggested that gender-related differences are present in the clinical management of coronary artery disease, the presence of such a difference with respect to referral to catheterization after noninvasive testing is disputed. METHODS: We examined 3,211 consecutive patients (1,074 women, 2,137 men) who underwent exercise dual-isotope single-photon emission computed tomography and had follow-up evaluation performed at least 1 year after nuclear testing (mean [+/- SD] follow-up 19 +/- 5 months) for "hard" events (cardiac death and myocardial infarction) and referral to cardiac catheterization or revascularization within 60 days of nuclear testing. Multiple logistic regression analysis was performed to determine the best predictors of referral to catheterization as well as to examine whether gender itself added further information to this model. RESULTS: Although men were referred to catheterization more frequently than women (10.6% vs 7.1%, p < 0.001) early after exercise nuclear testing, there were no differences in the rate of referral to catheterization or revascularization after stratification by the amount of abnormally perfused myocardium detected by the nuclear scan. Both men and women with normal scan results were infrequently referred to subsequent catheterization. In the setting of severe ischemia, women were referred to catheterization more frequently than men. This higher rate appears to be clinically appropriate because women with severely abnormal scan results had a significantly higher event rate than men (17.5% vs. 6.3%, p < 0.0001). This greater risk in women than in men appeared to be underappreciated because the increased rate of hard events in women with severely abnormal scan results was out of proportion to the smaller increase in their rate of referral to cardiac catheterization. Although gender added information to the multivariate model most predictive of referral to catheterization models when nuclear variables were not included, when nuclear variables were considered, the addition of gender added no further significant information. This finding suggests that adjusting for differences in perfusion scan abnormalities by the use of nuclear testing eliminated the apparent gender-related referral bias. CONCLUSIONS: After controlling for differences in perfusion scan abnormalities, no gender-related referral bias to catheterization was present. In the setting of severe ischemia, women had a greater rate referral to catheterization than men. As a function of risk, both men and women were appropriately referred to catheterization at a low rate when the scan result was normal. However, because women with severe perfusion abnormalities had a greater rate of cardiac death and myocardial infarction then men, women in this high risk subgroup were underreferred to catheterization relative to men. This finding points to the need to better identify women at high cardiac risk.

Comparison of the sensitivity and specificity of exercise electrocardiography in biased and unbiased populations of men and women.

To assess for sex-related differences in posttest referral bias, we compared the accuracy of exercise electrocardiography in biased (coronary angiography only) and unbiased (all unselected) populations with possible coronary disease. A retrospective analysis of clinical and exercise test data from 4467 patients (788 who underwent angiography) was performed (2824 men and 1643 women). The accuracy of a positive exercise test result was assessed in the entire unbiased group with a method that used disease probability (derived with a logistic algorithm) rather than angiography results. We found that the sensitivity and specificity were significantly greater in men than in women with use of the biased or unbiased groups. When the results for the unbiased and biased groups were compared, the sensitivities for the unbiased group were significantly lower and the specificities were significantly higher than those of the biased group. These differences reflect the effects of posttest referral bias. The amounts that sensitivity decreased and specificity increased, however, was not different for men and women. Therefore, we conclude that the accuracy of exercise electrocardiography is lower in women than men irrespective of whether a biased or an unbiased group is used. However, these differences cannot be explained on the basis of sex-related differences in posttest referral bias.

Incremental value of prognostic testing in patients with known or suspected ischemic heart disease: a basis for optimal utilization of exercise technetium-99m sestamibi myocardial perfusion single-photon emission computed tomography.

OBJECTIVES: This study assessed the incremental prognostic implications of normal and equivocal exercise technetium-99m (Tc-99m) sestamibi single-photon emission computed tomography (SPECT) and sought to determine its incremental prognostic value, impact on patient management and cost implications. BACKGROUND: The prognostic implications of Tc-99m sestamibi SPECT are not well defined, and risk stratification using this test has not been explored. METHODS: We studied 1,702 patients referred for exercise Tc-99m sestamibi SPECT who were followed up for a mean (+/- SD) of 20 +/- 5 months. Patients with previous percutaneous transluminal coronary angioplasty or coronary artery bypass surgery were excluded. The SPECT studies were assessed using semiquantitative visual analysis. Cardiac death and myocardial infarction were considered "hard" events, and coronary angioplasty and bypass surgery > 60 days after testing were considered "soft" events. RESULTS: Of the 1,702 patients studied, 1,131 had normal or equivocal scan results. A total of 10 events occurred in this group (1 cardiac death and 1 myocardial infarction [0.2% hard events]; 4 coronary angioplasty and 4 bypass surgery procedures [0.7% soft events]). The rates of hard events and referral to catheterization after SPECT were similarly low in patients with a low (< 0.15), intermediate (0.15 to 0.85) and high (> 0.85) post-exercise treadmill test (ETT) likelihood of coronary artery disease. With respect to scan type, patients with normal, probably normal or equivocal scan results had similarly low hard event rates. In the 571 patients with abnormal scan results, there were 43 hard events (7.5%) and 42 soft events (7.4%) (p < 0.001 vs. 1,131 patients with normal scan results for both). When the complete spectrum of scan responses was considered, SPECT provided incremental prognostic value in all patient subgroups analyzed. However, the nuclear scan was cost-effective only in patients with interpretable exercise ECG responses and an intermediate to high post-ETT likelihood of coronary artery disease and in those with uninterpretable exercise ECG responses and an intermediate to high pre-ETT likelihood of coronary artery disease. CONCLUSIONS: Normal or equivocal exercise Tc-99m sestamibi study results are associated with a benign prognosis, even in patients with a high likelihood of coronary artery disease. Although incremental prognostic value is added by nuclear testing in all patient subgroups, a testing strategy incorporating nuclear testing proved to be cost-effective only in the groups with an intermediate to high likelihood of coronary artery disease before scanning.

Incremental value of exercise electrocardiography and thallium-201 testing in men and women for the presence and extent of coronary artery disease.

Our goal was to assess the incremental value of exercise testing in men and women for the diagnosis and extent of coronary artery disease. With data from one center, incremental logistic algorithms were developed and evaluated in a separate set of 865 patients from four centers. Variables included were pretest (age, sex, symptoms, diabetes, smoking, and cholesterol concentration); exercise electrocardiogram (ECG) (ST-segment depression [millimeters], ST-segment slope, peak heart rate, and change in systolic blood pressure); and thallium-201 scintigram (defect presence, reversibility, and intensity of hypoperfusion). End points were coronary disease presence (50% diameter stenosis) and extent (multivessel disease). Accuracy and incremental value were assessed by receiver operating characteristic (ROC) curve analysis. Incremental ROC curve areas for disease presence were pretest 0.75 +/- 0.02, post-exercise ECG 0.82 +/- 0.01, and post-thallium scintigram 0.85 +/- 0.01 and for disease extent were pretest 0.71 +/- 0.02, post-exercise ECG 0.76 +/- 0.02, and post-thallium scintigram 0.78 +/- 0.02 (p < 0.005 for all increments). Incremental increases in accuracy were similar for men and women. We conclude that when multivariable algorithms derived from one center were applied to a separate group, there was a significant incremental increase in accuracy associated with exercise testing for the presence and extent of coronary disease. This increase in accuracy was similar for men and women.

Prior restraint: a Bayesian perspective on the optimization of technology utilization for diagnosis of coronary artery disease.

In conclusion, at least 1/3 of patients with suspected coronary artery disease are inappropriately referred for scintigraphic diagnostic testing from a Bayesian such as those described in this report, may be a powerful mechanism for encouraging more appropriate technology utilization while simultaneously controlling costs, and are thereby deserving of a formal prospective demonstration trial. However, since only half the patients currently being tested are referred for diagnostic purposes, analogous strategies must be developed with respect to prognostic and therapeutic evaluation.

For goodness' sake: expected therapeutic benefit as a basis for healthcare delivery.

The current debate on our healthcare system has focused primarily on the cost of care. Because of drastically rising costs and their burden on our economy, government and the private sector have developed many approaches to reduce these costs. Managed care, special contracting arrangements, and government fiat have all been used to stem the tide of rising costs--with variable success. We propose that the primary goal of healthcare is the provision of patient benefit, and we describe a model that calculates an expected benefit in terms of survival and quality of life. We have applied this model to a cohort of patients undergoing coronary angiography to determine the distributions of benefit. Furthermore, we describe a reimbursement strategy that relates the expected therapeutic benefit to the reimbursement received for that therapy--the greater the benefit, the greater the reimbursement. The future of our healthcare system lies in keeping the patient at the center of the debate on the delicate balance between optimal care and societal cost.

Incremental value of simultaneous assessment of myocardial function and perfusion with technetium-99m sestamibi for prediction of extent of coronary artery disease.

OBJECTIVES: This study assessed the incremental value of technetium-99m myocardial single-photon emission computed tomography (SPECT) and simultaneous first-pass radionuclide angiography, when added to treadmill exercise, for prediction of the extent of coronary artery disease. BACKGROUND: Technetium-99m count statistics permit the simultaneous assessment of myocardial perfusion and function. However, whether this characteristic improves prediction of the extent of coronary artery disease remains unknown. METHODS: We studied 70 consecutive patients who had coronary angiography within 6 months of the scintigraphic study. All patients underwent a symptom-limited treadmill exercise test. Treadmill data were summarized using a previously validated score. Left ventricular ejection fraction and regional wall motion were evaluated from a first-pass radionuclide angiogram acquired at peak treadmill exercise in the anterior view. Perfusion was assessed visually. Extent of angiographic disease was expressed as the presence or absence of multivessel disease (more than two coronary artery territories with > 50% stenosis) and as a score that reflects the location of severe (> 75%) stenosis. RESULTS: Stepwise addition of scintigraphic data (perfusion first, followed by function) to the treadmill score showed significant incremental value for prediction of the angiographic score at each step; exercise ejection fraction alone was the strongest independent predictor. Discriminant accuracy for detection of multivessel disease was also improved by the addition of perfusion information to the treadmill score and addition of regional wall motion analysis to both of them. In this case, ejection fraction failed to show independent value. CONCLUSIONS: The addition of simultaneously performed sestamibi perfusion SPECT and first-pass radionuclide angiography to the treadmill exercise test significantly improved prediction of the extent of coronary artery disease.

Correspondence of left ventricular ejection fraction determinations from two-dimensional echocardiography, radionuclide angiography and contrast cineangiography.

OBJECTIVES: This study assessed the agreement of left ventricular ejection fraction determinations from two-dimensional echocardiography, radionuclide angiography and contrast cineangiography. BACKGROUND: Previously published reports suggest that two-dimensional echocardiography, radionuclide angiography and contrast cineangiography are equally acceptable methods of assessing left ventricular ejection fraction on the basis of high coefficients of correlation. However, correlation of methods does not necessarily imply agreement. METHODS: In a prospective analysis, 25 consecutive subjects all had two-dimensional echocardiography and radionuclide angiography performed within 10 days of each other in the cardiology department of metropolitan community hospital. A retrospective computer search (Medline) revealed seven studies, using the coefficient of correlation (r), comparing two-dimensional echocardiographic left ventricular ejection fraction (n = 268) with radionuclide angiographic (n = 174) or contrast cineangiographic (n = 119) left ventricular ejection fractions. RESULTS: The eight individual studies (n = 293) comparing two-dimensional echocardiography with either radionuclide angiography or contrast cineangiography exhibited coefficients of correlation ranging from 0.78 to 0.93. Agreement analysis using the method of Bland and Altman was performed by averaging the results obtained from the two techniques and determining how disparate any single ejection fraction was (with 95% confidence limits) from the mean value. Agreement ranged from 23% to 42% around the mean ejection fraction. The average lack of agreement between the two methods for all studies involved was 17%, with an average r value of 0.86. CONCLUSIONS: Left ventricular ejection fraction determinations by means of two-dimensional echocardiography, radionuclide angiography and contrast cineangiography exhibit high correlation and only moderate agreement. High correlation does not always imply high agreement. These results suggest that, when validated by agreement analysis, multiple studies may not be necessary in appropriate clinical situations, potentially reducing costs.

Incremental prognostic value of exercise thallium-201 myocardial single-photon emission computed tomography late after coronary artery bypass surgery.

OBJECTIVES: This study assessed the incremental prognostic value of exercise thallium-201 myocardial perfusion single-photon emission computed tomography (SPECT) performed > or = 5 years after coronary artery bypass surgery. BACKGROUND: Thallium-201 scintigraphy has shown significant prognostic value in a variety of populations with suspected and known coronary artery disease. However, its value in patients with previous bypass surgery remains unknown. METHODS: We studied 294 patients who were prospectively followed up. Cox proportional hazards models for prediction of "hard" events (cardiac death and nonfatal infarctions) were constructed, with variables considered for inclusion in hierarchic order: clinical and exercise data first, followed by scintigraphic information. RESULTS: Mean (+/- SD) follow-up duration after scintigraphy was 31 +/- 11 months. There were 20 cardiac deaths and 21 nonfatal acute myocardial infarctions. Twenty-nine patients had late (> 60 days after thallium-201 SPECT) revascularization procedures or underwent repeat bypass surgery or percutaneous transluminal angioplasty. Shortness of breath and peak exercise heart rate were the most important clinical predictors of hard events. Two scintigraphic variables added significant prognostic information to the clinical model: the thallium-201 summed reversibility score (summation of segmental differences between stress and redistribution scores) and the presence of increased lung uptake of the radiotracer. The global chi-square statistic for this model was twice as high as that for the clinical/exercise model alone (49.7 vs. 24.2). When a second multivariate Cox model was built adding "soft" events (i.e., late revascularization procedures) as outcomes of interest, the summed reversibility score was selected as an independent scintigraphic predictor of events. The global chi-square statistic for this model was 50.7, three times as high as that for the clinical/exercise model alone. CONCLUSIONS: After evaluation of treadmill and exercise data, thallium-201 myocardial perfusion SPECT provided incremental prognostic information in patients late after bypass.