Dipyridamole thallium imaging may not be a reliable screening test for coronary artery disease in patients undergoing vascular surgery

Dipyridamole thallium imaging has been proposed for cardiac risk stratification in patients undergoing peripheral vascular surgery. The purpose of this study was to define the benefit of this investigation in routine preoperative evaluation of these patients. The outcome of 86 patients undergoing vascular surgery procedures was examined in light of preoperative clinical assessment and dipyridamole SPECT thallium imaging (DST). Fifty-one patients (59%) were considered at high risk on clinical grounds, and 22 patients (26%) had perfusion defects. Ten patients suffered a perioperative coronary event, including unstable angina, myocardial infarction, or cardiac death. Seven of the patients with such events were among the 51 clinically high-risk subjects (14%). Three perioperative events occurred in the group of 19 patients with positive DST images who underwent surgery (16%), but the DST test failed to identify 7 patients who suffered coronary events. The frequency of abnormal thallium imaging was similar to the prevalence of angiographically significant coronary disease reported previously at this center, but considerably less than the rate of abnormal thallium imaging in past studies of vascular surgery patients. The application of the test to a low to moderate risk population is probably responsible for its lower predictive accuracy for coronary events. DST is not an ideal routine noninvasive technique for risk stratification in patients undergoing vascular surgery.     

Enhanced prognostic stratification of patients with left ventricular hypertrophy with the use of single-photon emission computed tomography

BACKGROUND: Patients with left ventricular hypertrophy (LVH) are at increased risk of future cardiovascular events. Little is known about risk stratification of these patients with the use of myocardial perfusion imaging. This study sought to assess the prognostic stratification of patients with LVH by using myocardial perfusion single-photon emission computed tomography (SPECT). METHODS AND RESULTS: We studied 633 consecutive patients with electrocardiographic evidence of LVH who underwent dual isotope myocardial perfusion SPECT (rest thallium 201/stress technetium 99m sestamibi) and were followed up for a mean period of 22 +/- 7 months. During the follow-up period, 67 events (35 cardiac deaths and 32 nonfatal myocardial infarctions) occurred (6% annual event rate). The results of the perfusion scan significantly risk-stratified the population; patients with normal scans had a low rate of nonfatal myocardial infarction and cardiac death (<1% per year of follow-up). The rates of cardiac events increased significantly as a function of the scan result: 4.9% in patients with mildly abnormal scans and 10. 3% in moderately to severely abnormal scans. Cox proportional hazards analysis demonstrated that after adjusting for pretest likelihood of coronary artery disease (the most predictive clinical variable; chi(2) = 15.5, P <.001), summed stress score (the most predictive nuclear variable; chi(2) = 18, P <.0001) added significant incremental prognostic information (global chi(2) increased from 15.5 to 36; P <.001). CONCLUSIONS: In patients with LVH with an overall high cardiac event rate, SPECT provided enhanced stratification by adding significant incremental prognostic information over clinical and historic variables.     

Prognostic value of myocardial perfusion imaging in predicting outcome after renal transplantation

Cardiovascular disease is a significant cause of morbidity and mortality after renal transplantation. Pretransplant screening in a subset of these patients for occult coronary artery disease (CAD) may improve outcome. The objective of this study was to examine the outcome of 600 patients after renal transplantation for end-stage renal disease. Prospective outcome data were collected on 600 consecutive patients who had renal transplantation between 1996 and 1998 at our institution at 42 +/- 12 months after surgery. Stress single-photon emission computed tomographic (SPECT) myocardial perfusion imaging was performed in 174 patients before surgery, 136 (78%) of whom had diabetes mellitus. There were a total of 59 events: 17 cardiac deaths, 14 nonfatal myocardial infarctions, and 28 noncardiac deaths. There were 12 cardiac events and 11 noncardiac deaths among those who had SPECT myocardial perfusion imaging. In a multivariate analysis that included important risk factors, age (p = 0.03 and 0.003, respectively) and diabetes (p = 0.02 and 0.005, respectively) were the predictors of total events and cardiac events in patients who did not undergo stress SPECT perfusion imaging. In the subgroup who had stress perfusion imaging, an abnormal perfusion SPECT study was the only predictor of cardiac events (p = 0.006). The 42-month cardiac event-free survival rate was 97% in patients with normal SPECT images and 85% in patients with abnormal SPECT images (RR 5.04, 95% confidence interval 1.4 to 17.6, p = 0.006). Thus, there is a 2.8% event rate per year after renal transplantation, and approximately 50% of these events are noncardiac. In high-risk patients (most of whom had diabetes) with preoperative stress perfusion imaging, those with normal images had significantly lower cardiac events than those with abnormal images. These results have important implications in patient screening and postoperative management.     

Prognostic value of dobutamine stress technetium-99m-sestamibi single-photon emission computed tomography myocardial perfusion imaging: stratification of a high-risk population.

OBJECTIVES: This work was undertaken to define the intrinsic cardiac risk of the patient population referred for dobutamine stress perfusion imaging and to determine whether dobutamine technetium-99m ((99m)Tc)-sestamibi single-photon emission computed tomography (SPECT) imaging is capable of risk stratification in this population. BACKGROUND: In animal models, dobutamine attenuates the myocardial uptake of (99m)Tc-sestamibi resulting in underestimation of coronary stenoses. Therefore, we hypothesized that the prognostic value of dobutamine stress (99m)Tc-sestamibi SPECT myocardial perfusion imaging might be impaired, owing to reduced detection of coronary stenoses. METHODS: We reviewed the clinical outcome of 308 patients (166 women, 142 men) who underwent dobutamine stress SPECT (99m)Tc-sestamibi imaging at our institution from September 1992 through December 1996. RESULTS: During an average follow-up of 1.9 +/- 1.1 years, there were 33 hard cardiac events (18 myocardial infarctions [MI] and 15 cardiac deaths) corresponding to an annual cardiac event rate of 5.8%/year, which is significantly higher than the event rate for patients referred for exercise SPECT imaging at our institution (2.2%/year). Event rates were higher after an abnormal dobutamine (99m)Tc-sestamibi SPECT study (10.0%/year) than after a normal study (2.3%/year) (p < 0.01), even after adjusting for clinical variables. In the subgroup (n = 29) with dobutamine-induced ST-segment depression and abnormal SPECT imaging, the prognosis was poor, with annual cardiac death and nonfatal MI rates of 7.9% and 13.2%, respectively. CONCLUSIONS: Patients referred for dobutamine perfusion imaging are a high-risk population, and dobutamine stress (99m)Tc-sestamibi SPECT imaging is capable of risk stratification in these patients.     

Prognostic value of thallium-201 single-photon emission computed tomographic myocardial perfusion imaging according to extent of myocardial defect: Study in 1,926 patients with foilow-up at 33 months

Objectives. This study was designed to assess the prognostic value of thallium-201 single-photon emission computed tomographic (thallium SPECT) perfusion imaging in patients evaluated for stable angina pectoris and to examine the relation, if any, between the preface and extent of myocardial defect and future fatal or nonfatal cardiovascular events (revascularization, secondary myocardial infarction).Background. Compared with planar scintigraphy, thallium SPECT enables better evaluation of the extent of mayocardial perfusion defect. However, its prognostic value has not yet been studied in a large population of patients.Methods. Between 1987 and 1989 we studied 3,193 patients. After exclusion of patients with unstable angina, myocardial infarction during the previous month or earlier revascularization, 1,926 patients were followed up for 33 ± 10 (mean ± SD) months after stress thallium SPECT imaging (performed after exercise in 1,121 patients or during dipyridamole infusion in 805 patients). Thallium SPECT imaging of the left ventricle was divided into six segments.Results. After normal thallium SPECT imaging (715 patients), the annual total and cardiovascular mortality rates were, respectively, 0.42%/year and 0.10%/year and were significantly higher after abnormal thallium SPECT imaging (respectively, 2.1%, relative risk 5, p = 0.012; 1.5%, relative risk 15, p < 0.0001 [log-rank test]). There was a significant relation between the number of abnormal segments and cardiovascular mortality during follow-up (p < 0.02) or the occurrence of nonfatal events (p < 0.001). The extent of defect on the initial scan provided the best SPECT variable for long-term prognosis. Thallium SPECT imaging provided additive prognostic information compared with other clinical variables (gender, previous myocardial infarction) and exercise electrocardiogram.Conclusions. In patients with stable angina, normal thallium SPECT imaging indicates a low risk patient, and the extent of myocardial defect is an important prognostic predictive factor.     

Limited usefulness of exercise testing and thallium scintigraphy in evaluation of ambulator patients several months after recovery from an acute coronary event: Implications for management of stable coronary heart disease

Objectives. This study evaluated the value of noninvasive testing to predict cardiac events in patients with stable coronary disease after hospital admission (and risk stratification) for an acute coronary event.Background. Exercise testing with thallium perfusion imaging identifies patients with obstructive coronary artery disease and has been used to stratify patients after myocardial infarction. Its usefulness for predicting cardiac events in patients with stable coronary disease after recovery from an acute coronary event was explored.Methods. Nine hundred thirty-six patients were enrolled 1 to 6 months after hospital admission for a coronary event Patients underwent exercise treadmill testing with planar thallium-201 scintigraphy and were followed up for an average of 23 months (range 6 to 43). End points were 1) unstable angina requiring hospital admission, nonfatal myocardial infarction or cardiac death; 2) nonfatal infarction or cardiac death; or 3) cardiac death alone.Results. Twelve patients died of cardiac causes (1.2%); 32 had a nonfatal myocardial infarction (3.4%); and 79 patients (8.4%) developed unstable angina in the first year. Exercise testing improved proportional hazards models constructed from clinical variables for all three end points (p < 0.05). The perfusion scan further improved models for the end points (nonfatal infarction or cardiac death and cardiac death alone, p < 0.05). However, the exercise test with or without thallium added little to the overall prediction of primary events (area under the receiver operating curve increased from 0.649 to 0,663), and only 2% to 13% of patients with abnormal results either had a nonfatal infarction or died.Conclusions. Thallium-201 scintigraphy and exercise testing variables identify patients at risk for subsequent cardiac events. However, the poor predictive performance of these tests in this group of patients with stable coronary disease severely limits their usefulness. These results suggest a limited role for exercise and thallium testing in predicting cardiac events in patients with known coronary 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.     

SPECT Imaging for Detecting Coronary Artery Disease and Determining Prognosis by Noninvasive Assessment of Myocardial Perfusion and Myocardial Viability

Basic knowledge of active and passive transport mechanisms for concentrating monovalent cations in myocardial cells led to the investigation of the application of radioisotopes of potassium, thallium, rubidium, and ammonia to the in vivo noninvasive assessment of regional myocardial perfusion and viability utilizing gamma camera or positron emission tomographic (PET) imaging technology. Subsequently, technetium-99m (Tc-99m)-labeled isonitriles (sestamibi and tetrofosmin), which bind to mitochondrial membranes, emerged as superior imaging agents with single photon emission tomography (SPECT) imaging. When any of these imaging agents are injected intravenously during either exercise or pharmacologic stress, myocardial defects in tracer uptake represent either abnormal regional flow reserve or myocardial scar reflecting of coronary artery disease (CAD). The major clinical indications for stress SPECT or PET myocardial perfusion imaging are for detection of CAD as the cause of chest pain and risk stratification for prognostication. Patients with normal stress myocardial perfusion scans have an excellent prognosis with <1.0% annual rate future annual death or nonfatal infarction. The greater the extent and severity of ischemic perfusion defects (defects seen on stress images but improve on resting images), the greater the subsequent death or infarction rate during follow-up. Rest imaging alone is performed for determination of myocardial viability in patients with CAD and severe left ventricular dysfunction. Myocardial segments showing >50% uptake compared to normal uptake have a better long-term outcome with revascularization than with medical therapy with enhanced left ventricular function and improved survival. Other applications of SPECT imaging include the evaluation of cardiac sympathetic function, assessment of myocardial metabolism in health and disease, and molecular imaging of coronary atherosclerosis and myocardial stem cell therapy.     

Perioperative and long-term prognostic value of intravenous dipyridamole thallium scintigraphy in patients with peripheral vascular disease

The prognostic value of long-term risk stratification of patients with peripheral vascular disease who undergo intravenous dipyridamole thallium scintigraphy has not been well studied. We screened 131 patients with peripheral vascular disease who underwent intravenous dipyridamole thallium testing to determine cardiac event rates over an average follow-up of 18 +/- 10 months. Of the 131 patients, 111 subsequently had peripheral vascular surgery. The patients with abnormal thallium scans after dipyridamole had a significantly higher risk of death or myocardial infarction, both in the perioperative phase (7% versus 0%; p less than 0.001) and at late follow-up (17% versus 6%; p less than 0.01). The risk of a cardiac event was two-fold greater when a reversible as compared to a fixed thallium defect was present. Multivariate analysis selected the number of thallium segments with perfusion defects, prior history of angina pectoris, and chest pain during dipyridamole testing as perioperative predictors of a cardiac event. A reversible thallium defect was the only predictor of death or nonfatal myocardial infarction during late follow-up. Thus intravenous dipyridamole thallium scintigraphy is a useful noninvasive test for risk stratification of patients before peripheral vascular surgery and provides prognostic information as to the risk of a cardiac event in the 2-year period after the test. A reversible thallium defect is associated with a significant increased risk and would indicate that coronary angiography should be considered and preoperative coronary revascularization.     

Noninvasive Coronary Risk Stratification of Elderly Patients

The prognostic value of stress thallium-201 myocardial perfusion imaging has not been defined in an elderly (at or above 70 years) population. To this end, we studied 468 consecutive elderly patients undergoing either Bruce protocol exercise stress (n equals 120) or intravenous dipyridamole stress (n equals 348) with quantitative planar thallium-201 imaging. These patients were followed for at least 2 years after testing to determine their rates of cardiac events (cardiac death, myocardial infarction, coronary revascularization). There were no stress-related complications in either subgroup. A 10% cardiac event rate (6 deaths and 6 myocardial infarctions) was observed in the exercise subgroup. Survival without cardiac events was associated with greater exercise duration (5.6?+/-2.4 vs 3.1?+/-2.4 min; P is less than 0.001) and peak exercise heart rate (131?+/-18 vs 120?+/-19 bpm; P is less than 0.05). Multivariate analysis identified the combination of peak exercise at or below Stage 1 and thallium-201 perfusion defects as significant predictors of cardiac events (relative risk equals 5.3 at 1 year). Sixty-four percent of elderly patients were successfully stratified into very low and high risk subgroups, with annual cardiac event rates of less than 1% and greater than 15%, respectively. The cardiac event rate in dipyridamole stress patients was 22% (24 myocardial infarction, 52 death, 42 revascularization). The cardiac event rate was significantly lower (5%) in 150 patients with a normal dipyridamole thallium-201 study (P is less than 0.001). Clinical univariate predictors of cardiac events were previous myocardial infarction, congestive heart failure symptoms, hypercholesterolemia and diabetes (all P equals 0.05). A fixed, reversible, or combined thallium defect pattern was correlated with cardiac death or myocardial infarction (P is less than 0.05). Multivariate analysis demonstrated that the presence of an abnormal dipyridamole thallium study was the single-best predictor of cardiac events (relative risk equals 7.2; P is less than 0.01) We conclude that exercise and dipyridamole thallium-201 myocardial imaging are powerful independent noninvasive techniques for prognostication in the elderly patient population, a group with the potential for advanced coronary artery disease and a high risk of cardiac events.     

Independent contribution of myocardial perfusion defects to exercise capacity and heart rate recovery for prediction of all-cause mortality in patients with known or suspected coronary heart disease

OBJECTIVES: The goal of this study was to determine the value of thallium201 single photon emission computed tomography (SPECT) imaging for prediction of all-cause mortality when considered along with functional capacity and heart rate recovery. BACKGROUND: Myocardial perfusion defects identified by thallium201 SPECT imaging are predictive of cardiac events. Functional capacity and heart rate recovery are exercise measures that also have prognostic implications. METHODS: We followed 7,163 consecutive adults referred for symptom-limited exercise thallium SPECT (mean age 60 +/- 10, 25% women) for 6.7 years. Using information theory, we identified a probable best model relating nuclear findings to outcome to calculate a prognostic nuclear score. RESULTS: There were 855 deaths. Intermediate- and high-risk prognostic nuclear scores were noted in 28% and 10% of patients. Compared with those with low-risk scans, patients with an intermediate-risk score were at increased risk for death (14% vs. 9%, hazard ratio: 1.67, 95% confidence interval [CI]: 1.44 to 1.95, p < 0.0001), while those with high-risk scores were at greater risk (24%, hazard ratio: 2.98, 95% CI: 2.49 to 3.56, p < 0.0001). In multivariable analyses that adjusted for clinical characteristics, functional capacity and heart rate recovery, an intermediate-risk nuclear score remained predictive of death (adjusted hazard ratio: 1.50, 95% CI: 1.28 to 1.76, p < 0.0001), as did a high-risk score (adjusted hazard ratio: 2.76, 95% CI: 2.13 to 2.56, p < 0.0001). Impaired functional capacity and decreased heart rate recovery provided additional prognostic information. CONCLUSIONS: Myocardial perfusion defects detected by thallium SPECT imaging are independently predictive of long-term all-cause death, even after accounting for exercise capacity, heart rate recovery and other potential confounders.     

Role of exercise thallium-201 myocardial perfusion scintigraphy in predicting prognosis in suspected coronary artery disease

While exercise thallium imaging has improved sensitivity and specificity for detection of coronary artery disease (CAD), its predictive value for morbid cardiac events is unclear. Of 532 consecutive patients who underwent exercise thallium imaging, follow-up was complete in 515 (97%) after an average of 36 months (range 31 to 48). Two hundred six patients had an abnormal exercise thallium response and 309 had a normal response. Twenty morbid cardiac events occurred (13 deaths and 7 acute myocardial infarctions [AMI]). Of the 13 patients who died, 12 had abnormal thallium results. Overall, 5.8% of the patients with abnormal thallium results died, in contrast to 0.3% of patients with normal results. Of the 7 patients who had a nonfatal AMI, 3 had abnormal exercise thallium results. Moreover, similar proportions of patients (1.4% and 1.3%) with normal and abnormal exercise thallium results had nonfatal AMI. Presence or absence of pathologic Q waves and inclusion of exercise electrocardiographic results did not significantly alter the results. Thus, although a normal exercise thallium response significantly reduces the likelihood of cardiovascular death, its predictive value for nonfatal AMI is limited. Moreover, the relatively low event rate for patients with a positive exercise thallium response further limits its prognostic value.     

Quantitative gated single-photon emission computed tomography with (99m)Tc sestamibi predicts major cardiac events in elderly patients with known or suspected coronary artery disease: the QGS-Prognostic Value in the Elderly (Q-PROVE) Study.

BACKGROUND: Although electrocardiogram-gated single-photon emission computed tomography (SPECT) may be useful in risk stratification of elderly patients with coronary artery disease (CAD), few studies have prospectively evaluated its prognostic value in this patient population. METHODS AND RESULTS: A total of 175 patients aged 75 years or more with known or suspected CAD were prospectively evaluated by stress gated SPECT using a 20-segment model and an automatic functional analysis. Patients with acute coronary syndrome within the previous 3 months, and those who underwent coronary revascularization within 3 months after the SPECT study were excluded. Outcome assessment included prespecified cardiac events and noncardiac deaths. During a mean follow-up of 3.4 years, there were 18 cardiac events: 2 cardiac deaths, 1 nonfatal myocardial infarction, 3 coronary artery bypass grafting, 5 percutaneous coronary interventions, 1 unstable angina, 4 heart failures, and 2 malignant arrhythmias. Kaplan-Meier survival estimation indicated an event-free survival rate of 98.1% at 3 years in patients without myocardial ischemia, but 79.9% in those with ischemia as documented by gated SPECT (p=0.0001). Multivariate analysis using the Cox proportional hazard model demonstrated that stress-induced myocardial ischemia was the only independent predictor for subsequent cardiac events (p<0.01). CONCLUSIONS: Stress gated SPECT predicts cardiac events in patients aged 75 years or more with known or suspected CAD and may have a role in risk stratification of this patient population.     

Exercise thallium imaging in patients with diabetes mellitus. Prognostic implications

We used exercise thallium 201 imaging in 123 patients with diabetes mellitus (77 men and 46 women, aged 56 +/- 8 years), 75% of whom had angina pectoris (typical or atypical). During exercise testing, 18 patients (15%) had angina pectoris, 28 (23%) had ischemic ST changes, and 69 (56%) had abnormal thallium images. During follow-up (up to 36 months), there were 12 cardiac events; four patients died of cardiac causes and eight had nonfatal acute myocardial infarction. Univariate and multivariate survival analysis identified two independent predictors of cardiac events: the event rate was significantly less in patients with normal images and exercise heart rate over 120 beats per minute than in patients with abnormal images and exercise heart rate of 120 beats per minute or less (0% vs 22%). The patients with abnormal images or exercise heart rate of 120 beats per minute or less had an intermediate event rate (11.5%). Furthermore, two of the 54 patients with normal images and ten of 69 patients with abnormal images had subsequent cardiac events. Thus, exercise thallium imaging is useful in risk stratification in patients with diabetes mellitus.     

Dipyridamole cardiac imaging

Dipyridamole cardiac imaging is a useful alternative technique to exercise stress testing in the evaluation of patients with ischemic heart disease. Intravenous dipyridamole is still in the investigational phase, while oral dipyridamole is widely available. The hemodynamic effects of dipyridamole include an increase in coronary blood flow (due to coronary vasodilation) which is in excess of the increase in myocardial oxygen consumption and cardiac output. The disparity in the increase in coronary blood flow relative to the cardiac output results in an increase in myocardial thallium activity and an increase in the myocardial/background activity ratio. The quality of the thallium images is better or similar to that of exercise thallium images. The optimal dose of intravenous dipyridamole is 0.56 mg/kg, and of the oral dose it is 300 to 400 mg, although higher doses may be necessary in some patients. Analysis of the thallium images has been to a large extent based on visual inspection of the planar images. Delayed images are helpful to establish the nature of the perfusion abnormalities (transient or fixed). The process of redistribution is based on disparate rates of washout from the normal and abnormal zones. The sensitivity and specificity of dipyridamole thallium imaging, whether intravenous or oral, have been shown in a number of studies to be quite adequate and comparable to that achieved during exercise thallium imaging. Dipyridamole two-dimensional echocardiography has also been used in the detection of coronary artery disease; transient (new or worsening of preexisting) wall motion abnormalities have been found to be a specific marker of coronary artery disease. Transmural as well as regional coronary steal phenomena have been postulated as the mechanism for dipyridamole-induced regional wall motion abnormalities. Compared to exercise two-dimensional echocardiography, dipyridamole echocardiography provides high-quality studies and in higher proportions of patients. The results of dipyridamole thallium imaging have also been extremely important in identifying high-risk patients after acute myocardial infarction or patients with peripheral vascular disease undergoing elective vascular surgery; the presence of a dipyridamole-induced perfusion abnormality identifies patients at high risk for future cardiac events. Thus, dipyridamole cardiac imaging is helpful in the diagnosis of coronary artery disease and in risk stratification.     

Value of pharmacologic stress myocardial perfusion imaging for preoperative risk stratification for aortic surgery.

BACKGROUND: Aortic surgery is an invasive, high-risk noncardiac procedure and the patients who require it have a high prevalence of coronary artery disease. Therefore, preoperative risk stratification for this subset is essential. METHODS AND RESULTS: To assess the perioperative risk for aortic surgery, pharmacologic stress single-photon emission computed tomography (SPECT) was performed in 302 patients: aortic dissection in 56, thoracic aortic aneurysm in 124, and abdominal aortic aneurysm in 122. Not only was the presence or absence of perfusion defects analyzed, but also the 20-segment model. Pharmacologic thallium SPECT revealed negative findings in 210 patients and positives in 92. Perioperative cardiac events occurred in 9 patients: 7 occurred in patients with positive SPECT, and in only 2 of those with negative SPECT (2/210 vs 7/92; p<0.05). Multivariate analysis using logistic regression model revealed that a summed stress score>or=14 was the most important factor to identify patients who subsequently had perioperative cardiac events. CONCLUSIONS: Pharmacologic stress SPECT has significant value in the risk stratification of patients before aortic surgery. In patients with positive SPECT, an aggressive approach to reduce the preoperative risk is necessary, whereas aortic surgery can be performed safely in patients with negative SPECT.     

Identification of severe coronary artery disease in patients with a single abnormal coronary territory on exercise thallium-201 imaging: the importance of clinical and exercise variables

OBJECTIVES: The aim of this study was to determine which clinical, exercise and thallium variables can aid in the identification of three-vessel or left main coronary artery disease (3VLMD) in patients with one abnormal coronary territory (either a reversible or fixed defect) on exercise thallium testing and to test the prognostic value of these variables. BACKGROUND: Although the sensitivity of detection of coronary artery disease by thallium-201 imaging is high, the actual detection of 3VLMD by thallium tomographic images alone is not optimal. METHODS: A multivariate model for prediction of 3VLMD was developed from several clinical, exercise and thallium-201 variables in a training population of 264 patients who had one abnormal coronary artery territory on exercise thallium testing and had undergone coronary angiography. Using this model, patients were stratified into risk groups for prediction of 3VLMD. A separate validation cohort of 474 consecutive patients who were treated initially with medical therapy and who had one abnormal coronary territory were divided into identical risk groupings by the variables derived from the training population, and they were followed for a median of 7.0 years to evaluate the prognostic value of this model. RESULTS: The prevalence of 3VLMD was 26% in the training population despite one abnormal thallium coronary territory. Four clinical and exercise variables--diabetes, hypertension, magnitude of ST segment depression, and exercise rate-pressure product-were found to be independent predictors of 3VLMD. In the training population, the prevalence of 3VLMD in low-, intermediate- and high-risk groups was 15%, 22% and 51%, respectively. When the multivariate model was applied to the validation population, the eight-year overall survival rates in the low-, intermediate- and high-risk groups were 89%, 73% and 75%, respectively (p < 0.001). CONCLUSIONS: A substantial proportion of patients with one abnormal thallium coronary territory have 3VLMD with subsequent divergent outcomes based upon risk stratification by clinical and exercise variables. Consequently, the finding of only a single abnormal coronary territory by thallium-201 perfusion imaging does not necessarily confer a benign prognosis in the absence of consideration of nonimaging variables.     

Risk assessment using single-photon emission computed tomographic technetium-99m sestamibi imaging

Objectives. This review summarizes the results of single-photon emission computed tomographic (SPECT) technetium-99m (Tc-99m) tracer imaging in patients with stable symptoms, patients with acute coronary syndromes, patients undergoing major noncardiac surgery and patients with chest pain in the emergency department.Background. Previous studies have examined the prognostic value of stress thallium imaging in several subsets of patients with ischemic heart disease. At present, >50% of myocardial perfusion studies are performed with technetium-labeled tracers in the United States. Furthermore, there is a shift from diagnostic to the prognostic utility of stress testing. There are important differences between technetium-labeled tracers and thallium-201. It is therefore important to review the prognostic value of technetium-labeled tracers.Methods. We analyzed published reports in English on risk assessment using Tc-99m perfusion tracers.Results. The largest experience is in patients with stable symptoms, comprising >12,000 patients in 14 studies. In these patients, normal stress SPECT sestamibi images were associated with an average annual hard event rate of 0.6% (death or nonfatal myocardial infarction [MI]). In contrast, patients with abnormal images had a 12-fold higher event rate (7.4% annually). Both fixed and reversible defects are prognostically important, and quantitative analysis shows increased risk in relation to the severity of the abnormality. These results are similar to those obtained with thallium-201.Conclusions. Patients with stable chest pain syndromes and normal stress SPECT sestamibi images have a very low risk of death or nonfatal MI. It is highly unlikely that coronary revascularization can improve survival in such patients. Patients with abnormal images have an intermediate to high risk for future cardiac events, depending on the degree of the abnormality. Further prospective studies comparing aggressive medical therapy with coronary revascularization in these patients are warranted.     

Principal uses of myocardial perfusion scintigraphy in the management of patients with known or suspected coronary artery disease

The use of myocardial perfusion single photon emission computed tomography (SPECT) has undergone considerable expansion and evolution over the past 2 decades. Although myocardial perfusion imaging was first conceived as a noninvasive diagnostic tool for determining the presence or absence of coronary artery disease, its prognostic value is now well established. Thus, identification of patients at risk for future cardiac events has become a primary objective in the noninvasive evaluation of patients with chest pain syndromes and among patients with known coronary artery disease. In particular, the ability of myocardial perfusion SPECT to identify patients at low (< 1%), intermediate (1% to 5%) or high (> 5%) risk for future cardiac events is essential to patient management decisions. Moreover, previous studies have conclusively shown the incremental prognostic value of myocardial perfusion SPECT over clinical and treadmill exercise data in predicting future cardiac events. This report addresses the current role and new developments, with respect to the use of myocardial perfusion imaging, in determining patient risk for cardiac events and the cost-effective integration of such information into patient management decisions.     

Long-term prognostic value of preoperative dipyridamole thallium imaging and clinical indexes in patients with diabetes mellitus undergoing peripheral vascular surgery

The objective of this study is to assess the prognostic impact of preoperative dipyridamole thallium imaging and clinical variables on the long-term outcome of diabetic patients undergoing peripheral vascular surgery. Complete follow-up was obtained in 101 consecutive patients with diabetes mellitus undergoing routine dipyridamole thallium scintigraphy before vascular surgery (mean 4.2 +/- 3.2 years, range 1 month to 11 years). Low risk was defined by diabetes alone with a normal resting electrocardiogram. High risk was defined as a history of angina, myocardial infarction, congestive heart failure, or resting electrocardiogram abnormalities. There were 71 deaths in 98 patients discharged alive from the hospital (median survival 4.4 years). Age, the presence of resting electrocardiogram abnormalities, and an abnormal thallium scan were independent predictors of late death. After adjusting for age >70 years and thallium abnormalities, high-risk patients had a death rate 4.8 times (95% confidence interval 1.7 to 13.4, p <0.002) greater than low-risk patients. The presence of >2 reversible thallium defects was useful in further risk stratification of both low- and high-risk patients. Low-risk patients with >2 reversible defects had a median survival of 4.0 years compared with 9.4 years in those with < or =2 reversible defects (p <0.001). Similarly, high-risk patients with < or =2 reversible defects had an intermediate median survival rate of 4.7 years compared with 1.8 years in the group with >2 reversible defects (p <0.001). Therefore, advanced age and the presence of resting electrocardiographic or thallium abnormalities identifies a subset of diabetic patients with a poor long-term outcome after vascular surgery. Combined clinical and thallium variables may identify a population in whom intensive medical or surgical interventions may be warranted to reduce both perioperative and late cardiac events.