The treadmill exercise score revisited: coronary arteriographic and thallium perfusion correlates

Improved Performance of PET Myocardial Perfusion Imaging Compared to SPECT in the Evaluation of Suspected CAD

PURPOSE OF REVIEW

Myocardial perfusion imaging (MPI) with single photon emission computed tomography (SPECT) has played a central role in the non-invasive evaluation of patients with obstructive coronary artery disease (CAD) for decades. In this review, we discuss the key differences and advantages of positron emission tomography (PET) MPI over SPECT MPI as it relates to the diagnosis, prognosis, as well as clinical decision-making in patients with suspected CAD.

RECENT FINDINGS

Stress-induced perfusion abnormalities on SPECT help estimate presence, extent, and location of ischemia and flow-limiting obstructive CAD, help with risk stratification, and serve as a gatekeeper to identify patients who will benefit from downstream revascularization versus medical management. Some of the major limitations of SPECT include soft-tissue attenuation artifacts, underestimation of ischemia due to reliance on relative perfusion assessment, and longer protocols with higher radiation dose when performed with traditional equipment. PET MPI addresses most of these limitations and offers better quality images, higher diagnostic accuracy along with shorter protocols and lower radiation dose to the patient. A special advantage of PET scanning lies in the ability to quantify absolute myocardial blood flow and assess true extent of epicardial involvement along with identifying non-obstructive phenotypes of CAD such as diffuse atherosclerosis and microvascular dysfunction. In addition, stress acquisition at/near peak stress with PET allows us to measure left ventricular ejection fraction reserve and myocardial blood flow reserve, which help with identifying patients at a higher risk of future cardiac events and optimally select candidates for revascularization. The several technical advantages of PET MPI position as a superior method to diagnose obstructive and non-obstructive phenotypes of ischemic heart disease affecting the entirety of the coronary circulation offer incremental value for risk stratification and guide post-test management strategy for patients with suspected CAD.

Outcome of patients with high-risk Duke treadmill score and normal myocardial perfusion imaging on spect

BACKGROUND

Annual mortality rate can range from <1% for patients with normal myocardial perfusion by SPECT to >5% based on a high-risk Duke treadmill score (DTS). Information on the prognosis of patients with the combination of HRDTS and normal SPECT is limited and is the purpose of this study.

METHODS

Data from a large nuclear cardiology registry (n = 17,972 patients) were reviewed. A total of 340 had HRDTS (score ≤ -11) while undergoing SPECT. Combined cardiovascular mortality and non-fatal myocardial infarction (MI) and cardiovascular mortality alone were available in 310 patients at a mean follow-up of 4.01 ± 1.5 years.

RESULTS

The majority of the patients had abnormal SPECT (n = 270, 71%). The abnormal SPECT patients compared to the normal were older (65.6 vs 62.8 years of age; P = .025), more likely to have abnormal left ventricular ejection fraction (26.1% vs 0%; P < .0001), known coronary artery disease (CAD, 35.9% vs 7.8%; P < .0001) and lower DTS (-14.5 vs -13.2; P = .0006), Kaplan-Meier survival analysis demonstrated a significantly lower cardiovascular mortality (5.4% vs 0%, P = .02) and combined outcome of MI and cardiovascular mortality (15% vs 4.4%, P = .009) in patients with normal versus abnormal SPECT.

CONCLUSIONS

High-risk DTS is associated with abnormal perfusion SPECT in most patients, but nearly one-third of the patients had normal perfusion. Patients with a normal SPECT had a lower cardiovascular event rates.

An update on exercise stress testing

Exercise stress testing is the most commonly used noninvasive method to evaluate for coronary artery disease in men and women. Although emphasis has been placed on the diagnostic value of ST-segment depression, the exercise stress test provides other valuable diagnostic and prognostic data, beyond ST-segment depression. The value of these variables, which include exercise capacity, chronotropic response, heart rate recovery, blood pressure response, and the Duke Treadmill Score, are reviewed in this article. In addition, the gender differences seen with these exercise testing variables are reviewed. In this modern era of exercise stress testing, making use of all the information from a stress test and creating a comprehensive stress testing report are recommended in the evaluation of patients with suspected coronary artery disease who undergo exercise stress testing.

A simple score for predicting coronary artery disease in patients with chest pain

BACKGROUND

We have previously derived a chest pain score by comparing those with and without coronary artery disease on angiography, which was subsequently validated in patients attending coronary angiography.

AIM

To test the predictive validity of the score prospectively in a more varied out-patient population, and to determine whether it had predictive validity in addition to exercise testing.

DESIGN

Prospective clinical study.

METHODS

The score was applied to 405 out-patients with chest pain who subsequently underwent coronary angiography. Framingham risk analysis and exercise testing were performed in 155.

RESULTS

The score had a sensitivity of 91.4% and specificity of 28% for coronary artery disease, which was found in 31.8%, 51%, 63%, and 82% of those with scores of 0, 1, 2, and 3, respectively. Gender (p < 0.001), age (p < 0.001), and chest pain score (p = 0.009) independently predicted coronary artery disease on multivariate Poisson regression analysis. The chest pain score had additive predictive value with Framingham risk analysis and Duke's score.

DISCUSSION

This simple chest pain score can predict coronary anatomy with similar sensitivity to exercise testing, and can be used in conjunction with exercise testing and other measures. Further validation of the chest pain score in the primary care setting will be useful.

Exercise testing scores as an example of better decisions through science

INTRODUCTION

The application of common statistical techniques to clinical and exercise test data has the potential to become a useful tool for assisting in the diagnosis of coronary artery disease, assessing prognosis, and reducing the cost of evaluating patients with suspected coronary disease. Since general practitioners function as gatekeepers and decide which patients must be referred to the cardiologist, they need to optimally use the basic tools they have available (i.e., history, physical exam, and the exercise test).

METHODS

Review of the literature with a focus on the scientific techniques for aiding the decision-making process.

RESULTS

Scores derived from multivariable statistical techniques considering clinical and exercise data have demonstrated superior discriminating power when compared using receiver-operating-characteristic curves with the ST segment response. In addition, by stratifying patients as to probability of disease and prognosis, they provide a management strategy. While computers as part of information management systems can calculate complicated equations to provide scores, physicians are reluctant to trust them. Thus, these scores have been represented as nomograms or simple additive tables so physicians are comfortable with their application. Scores have also been compared with physician judgment and been found to estimate the presence of coronary disease and prognosis as well as expert cardiologists, and often better than nonspecialists.

CONCLUSION

Multivariate scores can empower the clinician to assure the cardiac patient with access to appropriate and cost-effective cardiological care.

Better decisions through science: exercise testing scores

Statistical tools can be used to create scores for assisting in the diagnosis of coronary artery disease and assessing prognosis. General practitioners and internists frequently function as gatekeepers, deciding which patients must be referred to the cardiologist. Therefore, they need to use the basic tools they have available (ie, history, physical examination and the exercise test) in an optimal fashion. Scores derived from multivariable statistical techniques considering clinical and exercise data have demonstrated superior discriminating power compared with diagnosis only using the ST segment response. In addition, by stratifying patients as to probability of disease and prognosis, they provide a more practical management strategy than a response of normal or abnormal. Although computers, as part of information management systems, can calculate complicated equations and derive these scores, physicians are reluctant to trust them. However, when represented as nomograms or simple additive discrete pieces of information, scores are more readily accepted. The scores have been compared with physician judgment and have been found to estimate the presence of coronary disease and prognosis as well as expert cardiologists and often better than nonspecialists. However, the discriminating power of specific variables from the medical history and exercise test remains unclear because of inadequate study design and differences in study populations. Should expired gases be substituted for estimated METs? Should ST/heart rate index be used instead of putting ST depression and heart rate separately into the models? Should right-sided chest leads and heart rate in recovery be considered? There is a need for further evaluation of these easily obtained variables to improve the accuracy of prediction algorithms, especially in women. The portability and reliability of scores must be ensured because access to specialized care must be safeguarded. Assessment of the clinical and exercise test data and application of the newer scores can empower the clinician to assure the cardiac patient access to appropriate and cost-effective cardiologic care.

Assessing patients with possible heart disease using scores

Multivariable analysis of clinical and exercise test data has the potential to become a useful tool for assisting in the diagnosis of coronary artery disease, assessing prognosis, and reducing the cost of evaluating patients with suspected coronary disease. Since general practitioners are functioning as gatekeepers and decide which patients must be referred to the cardiologist, they need to use the basic tools they have available (i.e. history, physical examination and the exercise test), in an optimal fashion. Scores derived from multivariable statistical techniques considering clinical and exercise data have demonstrated superior discriminating power compared with simple classification of the ST response. In addition, by stratifying patients as to probability of disease and prognosis, they provide a management strategy. While computers, as part of information management systems, can run complicated equations and derive these scores, physicians are reluctant to trust them. Thus, these scores have been represented as nomograms or simple additive tables so physicians are comfortable with their application. Their results have also been compared with physician judgment and found to estimate the presence of coronary disease and prognosis as well as expert cardiologists and often better than nonspecialists. However, the discriminating power of specific variables from the medical history and exercise test remains unclear because of inadequate study design and differences in study populations. Should expired gases be substituted for estimated metabolic equivalents (METs)? Should ST/heart rate (HR) index be used instead of putting these measurements separately into the models? Should right-sided chest leads and HR in recovery be considered? There is a need for further evaluation of these routinely obtained variables to improve the accuracy of prediction algorithms especially in women. The portability and reliability of these equations must be demonstrated since access to specialised care must be safe-guarded. Hopefully, sequential assessment of the clinical and exercise test data and application of the newer generation of multivariable equations can empower the clinician to assure the cardiac patient access to appropriate and cost-effective cardiological care.

[Angiographic correlates of the high-risk criteria for conventional exercise testing and the Duke treadmill score]

OBJECTIVE

To compare the sensitivity, the specificity, the positive and negative predictive value and the predictive accuracy of the Duke Treadmill Score, the Spanish Society of Cardiology (SEC) and American College of Cardiology/American Heart Association (ACC/AHA) high-risk criteria for exercise testing in the detection of left main disease, three vessel disease and two vessel disease involving the proximal left anterior descending artery.

PATIENTS AND METHOD

A cohort of 199 patients (age 75 years) consecutively admitted to hospital for unstable angina was studied. All patients underwent an exercise stress test and coronariography.

RESULTS

The SEC high-risk Criteria showed a sensitivity of 69.2% and a specificity of 49.0%. The ACC/AHA high-risk Criteria demonstrated a sensitivity of 98.1% and a specificity of 23.8% and the Duke Treadmill Score presented a sensitivity of 30.8% and a specificity of 90.5%. In patients with moderate risk in the Duke Treadmill Score we found a sensitivity of 62.9% and a specificity of 39.8% for the SEC high-risk criteria, while the ACC/AHA high-risk Criteria presented a sensitivity of 100.0% and a specificity of 5.8%.

CONCLUSIONS

The ACC/AHA high-risk Criteria showed a higher sensitivity while the Duke Treadmill Score presented a higher specificity for the detection of left main disease, three vessel disease and two vessel disease involving the proximal left anterior descending artery. The ACC/AHA and SEC high-risk Criteria were found to be very useful in the group of patients with moderate risk in the Duke Treadmill Score.

Long-term outcome of patients with intermediate-risk exercise electrocardiograms who do not have myocardial perfusion defects on radionuclide imaging

BACKGROUND

The appropriate management of patients with intermediate-risk Duke treadmill scores is not established. The purpose of this study was to determine the long-term risk of subsequent cardiovascular events in patients with an intermediate-risk treadmill score who do not have myocardial perfusion defects on radionuclide imaging.

METHODS AND RESULTS

The existing databases of the nuclear cardiology laboratories of 4 academic institutions were searched retrospectively. A total of 4649 patients were identified who had intermediate-risk Duke treadmill scores (-10 to 4), normal or near-normal exercise single photon-emission computed tomographic myocardial perfusion images using either thallium-201 or technetium-99m sestamibi, and no previous coronary revascularization. Follow-up was 95% complete. Cardiovascular survival was 99.8% at 1 year, 99.0% at 5 years, and 98.5% at 7 years. Cardiac survival free of myocardial infarction was similarly high at 96.6% at 7 years. Cardiac survival free of myocardial infarction or revascularization was 87.1% at 7 years. Near-normal scans and cardiac enlargement were independent predictors of time to cardiac death. Seven-year cardiac survival was still high at 97.0% in the 357 patients with near-normal scans and normal cardiac size and somewhat lower, at 89.0%, in the 167 patients with cardiac enlargement.

CONCLUSIONS

Patients with an intermediate-risk treadmill score but with normal or near-normal exercise myocardial perfusion images and normal cardiac sizes are at low risk for subsequent cardiac death and can be safely managed medically until their symptoms warrant revascularization. The appropriate management of patients with cardiac enlargement will remain a matter of clinical judgment.

Impact of stress single-photon emission computed tomography perfusion imaging on downstream resource utilization

This study shows that in patients with intermediate pretest probability of coronary artery disease stress single-photon emission computed tomography perfusion imaging decreases the rate of coronary angiography and coronary revascularization and is economically a superior strategy to routine coronary angiography.

The treadmill test--where to stop and what does it mean?

The prognostic utility of an exercise ECG test depends upon having an adequate workload to stress the cardiac system. A negative stress test, in which there are no adverse clinical or ECG findings, and in which an adequate workload is achieved, stratifies patients into a low-risk group. The 1997 American Heart Association guidelines imply that any index of workload--heart rate, rate-pressure product, or exercise duration in multiples of resting O2 consumption (METS)--could be used to indicate that adequate stress was achieved. However, while there is considerable evidence supporting the use of METS as a strong independent prognostic variable, there is less support for the use of rate-pressure product or heart rate. Indeed, there is evidence that a high heart rate at a low workload carries an adverse prognosis. Further research is needed to identify the number of METS achieved that would define an adequate workload. In the meantime, a review of the literature suggests that 7 to 10 METS is a reasonable ballpark figure of the minimum workload in patients with a negative stress test that would imply a favorable outcome.

Comparison of the prognostic value of qualitative versus quantitative stress tomographic perfusion imaging

This study compared qualitative assessment of exercise thallium imaging to quantitative assessment in predicting outcome in 713 patients with 78% prevalence of coronary artery disease by coronary angiography; during a mean follow-up of 52 months, there were 106 hard cardiac events (death or nonfatal myocardial infarction). The qualitative method provided important prognostic information; however, unlike the quantitative technique, less patients were assigned to either the low- or high-risk group and proportionally more patients into the intermediate-risk group, which may limit the clinical usefulness of the technique.

Prognostic value of myocardial perfusion imaging in patients with high exercise tolerance

BACKGROUND

Although high exercise tolerance is associated with an excellent prognosis, the significance of abnormal myocardial perfusion imaging (MPI) in patients with high exercise tolerance has not been established. This study retrospectively compares the utility of MPI and exercise ECG (EECG) in these patients.

METHODS AND RESULTS

Of 388 consecutive patients who underwent exercise MPI and reached at least Bruce stage IV, 157 (40.5%) had abnormal results and 231 (59.5%) had normal results. Follow-up was performed at 18+/-2.7 months. Adverse events, including revascularization, myocardial infarction, and cardiac death, occurred in 40 patients. Nineteen patients had revascularization related to the MPI results or the patient's condition at the time of MPI and were not included in further analysis. Seventeen patients (12.2%) with abnormal MPI and 4 (1.7%) with normal MPI had adverse cardiac events (P<0.001). Cox proportional-hazards regression analysis showed that MPI was an excellent predictor of cardiac events (global chi2=13.2; P<0.001; relative risk=8; 95% CI=3 to 23) but EECG had no predictive power (global chi2=0.05; P=0.8; relative risk=1; 95% CI=0.4 to 3.0). The addition of Duke's treadmill score risk categories did not improve the predictive power of EECG (global chi2=0.17). The predictive power of the combination of EECG (including Duke score categories) and MPI was no better than that of MPI alone (global chi2=13.5).

CONCLUSIONS

Unlike EECG, MPI is an excellent prognostic indicator for adverse cardiac events in patients with known or suspected CAD and high exercise tolerance.

Comparison of the polar maps method and the summed stress score for predicting outcome in medically treated patients with coronary artery disease

This study showed that quantitative analysis of SPECT perfusion images provide comparable prognostic information to summed stress score in medically treated patients with coronary artery disease.

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.

Use of a prognostic treadmill score in identifying diagnostic coronary disease subgroups

BACKGROUND

Exercise testing is useful in the assessment of symptomatic patients for diagnosis of significant or extensive coronary disease and to predict their future risk of cardiac events. The Duke treadmill score (DTS) is a composite index that was designed to provide survival estimates based on results from the exercise test, including ST-segment depression, chest pain, and exercise duration. However, its usefulness for providing diagnostic estimates has yet to be determined.

METHODS AND RESULTS

A logistic regression model was used to predict significant (>/=75% stenosis) and severe (3-vessel or left main) coronary artery disease, and a Cox regression analysis was used to predict cardiac survival. After adjustment for baseline clinical risk, the DTS was effectively diagnostic for significant (P<0.0001) and severe (P<0.0001) coronary artery disease. For low-risk patients (score >/=+5), 60% had no coronary stenosis >/=75% and 16% had single-vessel >/=75% stenosis. By comparison, 74% of high-risk patients (score <-11) had 3-vessel or left main coronary disease. Five-year mortality was 3%, 10%, and 35% for low-, moderate-, and high-risk DTS groups (P<0.0001).

CONCLUSIONS

The composite DTS provides accurate diagnostic and prognostic information for the evaluation of symptomatic patients evaluated for clinically suspected ischemic heart disease.

Utility of stress single-photon emission computed tomography (SPECT) perfusion imaging in predicting outcome after coronary artery bypass grafting

Previous studies have examined the predictors of outcome in medically treated patients with coronary artery disease (CAD). There is limited information on predictors of outcome after coronary artery bypass grafting (CABG). This study examined the predictors of outcome of 255 patients with CAD, at a mean time of 5 years after CABG for angina pectoris. The 255 patients underwent coronary angiography and stress single-photon emission computed tomography (SPECT) myocardial perfusion imaging after CABG. During a mean follow-up of 41 +/- 28 months after stress testing, there were 34 hard events (24 cardiac deaths and 10 nonfatal myocardial infarctions). The hemodynamics during stress testing, and age and gender were not predictors of events. The SPECT variables of multivessel perfusion abnormality, perfusion deficit size, and increased lung thallium uptake were predictors of death and total events by uni- and multivariate survival analysis. There were 14 events in 45 patients (31%) with multivessel abnormality and increased lung thallium uptake, 14 events in 101 patients (14%) with either multivessel abnormality or increased lung uptake, and 6 events in 109 patients (6%) with neither of these 2 variables (p = 0.0001). The annual mortality and total event rates were 7.5% and 9.5% with both variables, 3.4% and 4.3% with either variable, and 0.6% and 1.7% with neither of the variables (p = 0.01). Thus, stress SPECT perfusion imaging is useful to stratify patients after CABG into low, intermediate, and high risk groups for future cardiac events.

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.

Comparison of thallium-201 single-photon emission computed tomography and electrocardiographic response during exercise in patients with normal rest electrocardiographic results

OBJECTIVES

This study compared the diagnostic accuracy of exercise thallium-201 single-photon emission computed tomography (SPECT) with the exercise electrocardiographic (ECG) response in patients with normal baseline ECG results.

BACKGROUND

Previous studies comparing exercise thallium imaging with exercise electrocardiography have included patients with abnormal rest ECG results that may have biased the results in favor of thallium imaging.

METHODS

Of 321 patients with a pretest likelihood of coronary artery disease of 70 +/- 29% (mean +/- SD) who underwent exercise stress testing and coronary angiography, 68 had no coronary artery disease; 94 had one-vessel disease; 79 had two-vessel disease; and 80 had three-vessel or left main coronary artery disease.

RESULTS

The diagnostic accuracy of SPECT was higher than that of the ECG response (79% vs. 49%, p < 0.0001). Patients with extensive (left main or three-vessel) coronary artery disease were older and had a lower work load, lower heart rate, greater ST segment depression and more extensive perfusion abnormalities than patients with no disease or one- or two-vessel disease. Multivariate discriminant analysis of exercise and thallium variables identified multivessel thallium abnormalities (F = 35), exercise heart rate (F = 18) and extent of ST segment depression (F = 6) as independent predictors of extensive disease. Of the 80 patients with left main or three-vessel disease, 37 (46%) had > or = 2-mm ST segment depression, 44 (55%) had multivessel SPECT abnormalities, and 61 (76%) had either > or = 2-mm ST depression or multivessel SPECT abnormalities (p = 0.0005 vs. the ECG response; p = 0.01 vs. SPECT).

CONCLUSIONS

In patients with an intermediate to high pretest probability of coronary artery disease and normal baseline ECG results, SPECT is superior to the ECG response in detecting coronary disease. Further, SPECT provides incremental power in identifying patients with extensive (left main or three-vessel) coronary disease.

Comparison of the treadmill exercise score and single-photon emission computed tomographic thallium imaging in risk assessment

BACKGROUND

This study compared the prognostic value of exercise single-photon emission computed tomographic (SPECT) thallium imaging with that of treadmill exercise score in medically treated patients with coronary artery disease (CAD).

METHODS AND RESULTS

The treadmill exercise score was derived from exercise duration, degree of ST segment depression, and the treadmill anginal index. There were 121 patients with no CAD and 316 patients with angiographically defined CAD (> or = 50% diameter stenosis of one or more vessels). During a mean follow-up of 29 months, there were 35 cardiac deaths or nonfatal myocardial infarctions. Multivariate Cox survival analysis showed the extent of thallium imaging abnormality and CAD to be independent predictors of prognosis. On the other hand, the treadmill exercise score was not a significant predictor even on univariate analysis. The results of thallium uptake were the strongest independent predictors of prognosis and in addition provided incremental prognostic power to coronary angiography (chi 2 = 29 for SPECT, 27 for coronary angiography, and 37 for both).

CONCLUSIONS

Thus exercise SPECT thallium imaging is significantly better than the treadmill exercise score in risk assessment. The size of the perfusion abnormality is an important predicator of prognosis.