Prognostic importance of silent myocardial ischemia detected by intravenous dipyridamole thallium myocardial imaging in asymptomatic patients with coronary artery disease

A Cohort Study of Myocardial Perfusion Imaging in Veteran Patients Without Symptoms: Contributing Factors and Results of Testing

Myocardial perfusion imaging (MPI) is commonly used to detect ischemia. Concerns about silent ischemia may encourage orders for MPI in asymptomatic patients. Factors contributing to this practice are poorly described and the clinical utility is questionable.We conducted a single center retrospective cohort investigation on Veterans who underwent MPI between December 2010 and July 2011. We gathered data on symptoms, baseline characteristics, results of MPI, and cardiovascular events within 1 year. MPI were categorized using 2009 appropriate use criteria (AUC).Of 592 patients, 127 (21.5%) had no symptoms at the time of MPI. Comparing symptomatic and asymptomatic patients, no differences were observed in baseline characteristics except abnormal ECG, more common in asymptomatic patients (n = 86, 67.7% vs. n = 232, 49.9% for symptomatic patients, P < 0.0001). Asymptomatic MPI were more commonly inappropriate (n = 26, 21.5% vs. n = 31, 6.7% for appropriate/uncertain, P < 0.0001). Detection of ischemia between patients with and without symptoms was not different (P = 0.86); however, among asymptomatic MPI that also demonstrated ischemia, none were inappropriate (n = 10 appropriate, n = 7 uncertain). In multivariate regression, 2 factors were associated with asymptomatic status, abnormal ECG (odds ratio [OR] 2.29, 95% confidence interval [CI] 1.5-3.49) and age over the median (OR 0.63, 95% CI: 0.41-0.95).A substantial portion of MPI tests are ordered for patients without symptoms. When compared to symptomatic patients, MPI for asymptomatic patient were more commonly inappropriate; however, the prevalence of ischemia was similar. MPI may be clinically relevant in some asymptomatic patients and decisions to test should be based on the AUC.

Right-sided chest leads in exercise testing for detection of coronary restenosis

BACKGROUND

The incorporation of right-sided chest leads (V(3)R through V(5)R) into standard exercise testing has been reported to improve its diagnostic utility.

HYPOTHESIS

The purpose of this study was to evaluate any improvement in the ability of exercise testing in detecting restenosis, using additional V(3)R through V(5)R leads, in asymptomatic patients undergoing percutaneous coronary intervention (PCI) in the right coronary artery (RCA) or/and left circumflex (LCX).

METHODS

We studied 172 consecutive patients (54 +/- 7 years old, 106 males) undergoing PCI in RCA or/and LCX. A treadmill test had been performed before PCI. Six months later, all patients underwent a second treadmill test and arteriography in order to detect silent ischemia due to restenosis. Recordings during exercise were obtained with the standard 12-leads plus V(3)R through V(5)R.

RESULTS

Out of 172 patients, 106 had stenosis in RCA, 35 in LCX, and 31 in both vessels while 6 months later, restenosis was detected in 8 (for RCA), 3 (for LCX), and 3 (for both vessels) patients respectively. Sensitivity, specificity, positive prognostic value, negative prognostic value, and accuracy of exercise testing performed post PCI were ameliorated using V(3)R through V(5)R (79% vs 57%, 97% vs 80%, 69% vs 21%, 98% vs 95%, and 95% vs 78% respectively, P < .05 for all except negative prognostic value). Maximal exercise-induced ST-segment deviation (in mm) was not changed post PCI in 12 leads (1.4 +/- 0.2 vs 1.5 +/- 0.2, P = NS) while it was decreased in V(3)R through V(5)R (0.2 +/- 0.2 vs 1.2 +/- 0.3, P < .01).

CONCLUSIONS

The addition of V(3)R through V(5)R improves the diagnostic ability of standard exercise testing in detecting silent ischemia due to restenosis in patients undergoing PCI in RCA or/and LCX.

The Prognostic Value of Vasodilator Myocardial Perfusion Imaging in Octogenarians

The ability of single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) to stratify risk in octogenarians is poorly defined. The authors identified 439 octogenarians who underwent vasodilator SPECT MPI between 1994 and 2000. Over a mean 2.5 years of follow-up, moderate and large stress defects were associated with increased crude mortality (normal: 24.5%, small defect: 21.9%, moderate or large stress defect: 41.4%, p for trend < 0.001). The degree of defect reversibility was also strongly associated with increased mortality (normal: 24.5%, no reversibility: 22.0%, small reversible defect: 36.5%, moderate or large reversible defect: 50.0%, p for trend < 0.001). In multivariable analysis, stress defects were the strongest predictor of mortality (hazard ratio, 2.39; 95% confidence interval, 1.56-3.65). The mortality of octogenarians with moderate or large perfusion defects is nearly double that of patients with normal or mildly abnormal MPI. Appropriately selected octogenarians with abnormal vasodilator SPECT imaging may benefit from more aggressive management of their cardiac disease.

Exercise stress testing before and after successful multivessel percutaneous transluminal coronary angioplasty

Controversy exists regarding the diagnostic accuracy, optimal technique, and timing of exercise testing after percutaneous coronary intervention. The objectives of the present study were to analyze variables and the power of exercise testing to predict restenosis or a new lesion, 6 months after the procedure. Eight-four coronary multi-artery diseased patients with preserved ventricular function were studied (66 males, mean age of all patients: 59 +/- 10 years). All underwent coronary angiography and exercise testing with the Bruce protocol, before and 6 months after percutaneous coronary intervention. The following parameters were measured: heart rate, blood pressure, rate-pressure product (heart rate x systolic blood pressure), presence of angina, maximal ST-segment depression, and exercise duration. On average, 2.33 lesions/patient were treated and restenosis or progression of disease occurred in 46 (55%) patients. Significant increases in systolic blood pressure (P = 0.022), rate-pressure product (P = 0.045) and exercise duration (P = 0.003) were detected after the procedure. Twenty-seven (32%) patients presented angina during the exercise test before the procedure and 16 (19%) after the procedure. The exercise test for the detection of restenosis or new lesion presented 61% sensitivity, 63% specificity, 62% accuracy, and 67 and 57% positive and negative predictive values, respectively. In patients without restenosis, the exercise duration after percutaneous coronary intervention was significantly longer (460 +/- 154 vs 381 +/- 145 s, P = 0.008). Only the exercise duration permitted us to identify patients with and without restenosis or a new lesion.

Medium- to long-term prognostic impact of dipyridamole thallum-201 myocardial single-photon emission computed tomography in elderly patients

Dipyridamole thallium-201 single-photon emission computed tomography (SPECT) has not been extensively evaluated for risk stratification and the medium- to long-term prognostic value in elderly cardiac patients who are unable to exercise. The present study group comprised 210 consecutive patients aged at least 70 years with known or suspected coronary artery disease (CAD). The SPECT findings were classified as a reversible, fixed, or combined (reversible and fixed) defect. Of the 210 patients, 201 (77+/-5 years, 85 male) were successfully followed for 49+/-26 months. Thirteen (7%) patients had cardiac events: cardiac death (n=10), non-fatal myocardial infarction (n=1), or coronary artery bypass grafting (n=2). Cardiac events occurred in 3 of 112 patients with normal SPECT and in 10 of 89 patients with an abnormal scan (0.7% /year vs 2.8% /year, p=0.01). Stepwise Cox regression analysis revealed that the significant predictors of cardiac events were combined defects (relative risk 7.3) and the number of defect areas (relative risk 4.4). The predictive value of dipyridamole thallium-201 SPECT is maintained over 4 years in mixed populations of elderly CAD patients who are unable to exercise.

Comparison of late outcome in patients with versus without angina pectoris having reversible perfusion abnormalities during dobutamine stress technetium-99m sestamibi single-photon emission computed tomography

The aim of this study was to assess the prognostic significance of reversible perfusion abnormalities in patients without angina during dobutamine stress technetium-99m sestamibi single-photon emission computed tomography (SPECT). The study comprised 224 patients (age 60 +/- 11 years, 144 men) with completely or partially reversible perfusion abnormalities during dobutamine stress sestamibi SPECT. Follow-up end points were hard cardiac events (cardiac death and nonfatal myocardial infarction). Angina occurred in 93 patients (42%) during the dobutamine stress test (symptomatic ischemia group). The 131 patients without dobutamine-induced angina represented the silent ischemia group. There was no significant difference between patients with and without angina with regard to summed stress perfusion score (5.3 +/- 2.5 vs 5.2 +/- 2.2, p = 0.9) or summed ischemic score (3.1 +/- 1.7 vs 3.2 +/- 1.4, p = 0.7). During a median follow-up of 7.2 years, cardiac death occurred in 14 patients (15%) with and in 21 patients (16%) without angina. Nonfatal myocardial infarction occurred in 8 patients (9%) with and in 13 patients (10%) without angina. In a multivariate analysis model of clinical and perfusion data, independent predictors of cardiac events were age (hazard ratio 1.02, confidence intervals [CI] 1.01 to 1.05 per year increment), diabetes mellitus (hazard ratio 1.9, CI 1.2 to 3.4), and ischemic perfusion score (hazard ratio 2.1, CI 1.3 to 3.8). Patients with silent ischemia defined as reversible perfusion abnormalities without associated angina during dobutamine stress sestamibi SPECT imaging had similar incidences of ischemia and similar cardiac event rates compared with patients with symptomatic ischemia. Therefore, the absence of angina in association with reversible perfusion abnormalities should not be interpreted as a sign of a more benign prognosis.

Prognostic value of exercise cardiac tomography performed late after percutaneous coronary intervention in symptomatic and symptom-free patients

The long-term prognostic value of single-photon emission computed tomography (SPECT) performed late after percutaneous coronary intervention (PCI) has not been extensively evaluated. Moreover, the role of myocardial ischemia at SPECT in symptom-free patients after PCI is not clear. This study was designed to determine the long-term prognostic value of SPECT in predicting cardiac events after PCI in symptomatic and symptom-free patients. Exercise technetium-99m sestamibi SPECT was performed in 206 patients between 12 and 18 months after PCI. All patients were followed for a mean period of 37 +/- 16 months. Cardiac death, nonfatal myocardial infarction, and late revascularization procedures were considered to be events. Myocardial ischemia at SPECT was detectable in 44 patients. During follow-up, 24 patients experienced events (cardiac death in 4 patients, myocardial infarction in 10, and late revascularization in 10). At univariate analysis, the summed stress score (p <0.05) and summed difference score (p <0.001) were significant predictors of cardiac events. Event-free survival curves showed a higher event rate in patients with than without ischemia (p <0.001). The occurrence of cardiac events was higher in the presence of ischemia at SPECT in symptomatic and symptom-free patients (both p <0.001). The results of this study demonstrate that the extent and severity of myocardial ischemia at exercise SPECT performed between 12 and 18 months after PCI predicts cardiac events during long-term follow-up in symptomatic and symptom-free patients.

The usefulness of dipyridamole thallium-201 single photon emission computed tomography for predicting perioperative cardiac events in patients undergoing non-cardiac vascular surgery

The aim of this study was to evaluate the usefulness of dipyridamole Tl-201 myocardium single photon emission computed tomography (201Tl-SPECT) for predicting perioperative cardiac events in patients with arteriosclerosis obliterans (ASO) and abdominal aortic aneurysm (AAA) undergoing non-cardiac vascular surgery.

METHODS

Preoperative dipyridamole 201Tl-SPECT imaging in association with clinical risk assessment was performed in 224 consecutive patients (97 ASO and 127 AAA).

RESULTS

The patients were classified into three groups, including low-risk (n = 173, 77%), intermediate-risk (n = 39, 18%), and high-risk (n = 12, 5%) groups according to the clinical risk stratification. The prevalence of reversible Tl-201 defect was significantly higher in the high-risk group than that in the low-risk group (83% vs. 14%, p < 0.001). In 180 patients who underwent vascular surgery, 9 patients (5.0%) had perioperative cardiac events, including heart failure (n = 1), unstable angina (n = 2), and other cardiac events such as arrhythmias (n = 6). The clinical variables including the clinical risk stratification did not significantly correlate with the perioperative cardiac events. In contrast, the reversible defect on 201Tl-SPECT was the only variable to predict perioperative cardiac events by a stepwise logistic regression analysis (odds ratio 7.0, 95% confidence interval 1.7-28.0, p = 0.007). It was also a significant predictor of perioperative cardiac events in a subgroup of low risk patients (odds ratio 11.6, 95% confidence interval 2.3-57.4, p = 0.004). The sensitivity and specificity of the reversible defect for predicting perioperative cardiac events were 55.6% and 84.8% in all operated patients, and 57.1% and 89.7% in low risk patients, respectively.

CONCLUSIONS

The preoperative dipyridamole 201Tl-SPECT was useful for predicting perioperative cardiac events in patients with vascular diseases, even in patients identified as having a low risk based on the clinical risk assessment.

Technetium-99m-labeled myocardial perfusion agents: Are they better than thallium-201?

Currently, thallium-201 (201Tl)- and technetium-99m (99mTc)-labeled tracers are used interchangeably for the detection of coronary artery disease, the assessment of myocardial viability, and risk stratification. This article reviews some of the potential advantages and disadvantages of the 99mTc-labeled tracers relative to 201Tl. The basic myocardial kinetic properties and biodistribution of the commonly used 99mTc-labeled perfusion tracers are compared with those of 201Tl. The clinical value of the 99mTc-labeled perfusion tracers is then compared with that of 201Tl imaging. With regard to imaging physics and radiation safety, the 99mTc-labeled tracers are superior to 201Tl. Cost and tracer availability also may favor 99mTc-labeled perfusion tracers rather than 201Tl imaging. However, the most widely used 99mTc-labeled perfusion tracers currently approved for clinical use-99mTc-sestamibi and 99mTc-tetrofosmin-do not track myocardial flow as well as 201Tl does. This shortcoming of 99mTc-labeled perfusion tracers may reduce the sensitivity of these agents in detecting subcritical coronary artery disease. The most notable new perfusion agent is 99mTc-labeled bis(N-ethoxy, N-ethyl dithiocarbamato) nitrido technetium(v), which is considered to be the 99mTc-labeled equivalent of 201Tl. However, 99mTc-labeled bis(N-ethoxy, N-ethyl dithiocarbamato) nitrido technetium(v) is a neutral compound with kinetic properties that are very different from those of 201Tl. Myocardial perfusion imaging is often conducted in conjunction with exercise or with different pharmacologic stressors, both of which augment regional flow heterogeneity. Each of these stressors has unique effects on the coronary vasculature and influences the behavior of the radiolabeled perfusion agents. The substantial differences in myocardial uptake, clearance kinetics, and biodistribution between each of the 99mTc-labeled perfusion tracers and 201Tl should be considered in the clinical application of perfusion imaging. The myocardial retention of all of the agents is affected by myocardial viability. However, 201Tl demonstrates greater differential clearance from normal and ischemic regions (redistribution), making 201Tl a better agent for assessment of viability, particularly in patients with extremely low flow. In contrast, agents that do not redistribute, such as 99mTc-tetrofosmin, might be better for acute assessment of "risk areas" or of chest pain. Each of the available perfusion tracers has unique advantages and disadvantages that must be considered to ensure its optimal application.

Stress nuclear myocardial perfusion imaging versus stress echocardiography: prognostic comparisons

The use of noninvasive stress cardiac imaging for stratifying risk in patients with known or suspected coronary artery disease is growing as a tool for identification of the subgroup most likely to benefit from the expense and risk of more invasive procedures, including cardiac catheterization and coronary revascularization. In this setting, it is especially important that a test be able to identify patients with sufficiently low risk that clinicians are comfortable in deferring such interventions, especially in those with other markers of increased risk. Previous data have shown that cardiac risk is most closely related to the presence and extent of jeopardized viable myocardium on noninvasive stress cardiac imaging. Although stress echocardiography may have comparable ability to detect coronary artery disease, current data suggest that stress echocardiography detects significantly less jeopardized viable myocardium than stress nuclear myocardial perfusion imaging and consequently fewer patients at risk for cardiac events. Stress nuclear myocardial perfusion imaging may therefore have important advantages for risk stratification and the direction of future care of patients with known or suspected coronary artery disease.

Detection of coronary restenosis by exercise electrocardiography thallium-201 perfusion imaging and coronary angiography in asymptomatic patients after percutaneous transluminal coronary angioplasty

Noninvasive detection of restenosis in patients remaining asymptomatic after percutaneous transluminal coronary angioplasty (PTCA) remains a major clinical problem. The value of exercise electrocardiography (ECG) and exercise-redistribution thallium-201 single-photon emission computed tomography (SPECT) in detecting restenosis in such patients remains uncertain. Discordances between these tests and coronary angiography is a common situation. We studied 179 consecutive patients remaining asymptomatic after successful PTCA (208 vessels), who underwent 6 +/- 2 months of exercise ECG, SPECT, and coronary angiography. We sought to assess the diagnostic value of the noninvasive tests compared with coronary angiography, and identify the determinants of discordances between the tests. Restenosis (diameter stenosis >50%) was detected in 39% of patients and in 37% of vessels. The overall sensitivity, specificity, and accuracy for exercise ECG and SPECT in detecting restenosis in individual vessels were, respectively, 53% versus 63% (p = 0.06), 59% versus 77% (p = 0.0001), and 57% versus 72% (p = 0. 0001). On multivariate analysis, positive exercise ECG was associated with higher heart rate response (p = 0.02), incomplete revascularization (p = 0.004), and angiographic restenosis (p = 0. 03), whereas positive SPECT was associated with incomplete revascularization (p = 0.02), infarct-related artery PTCA (p = 0.01), and angiographic restenosis (p = 0.0001). Accuracies of the 2 tests were not significantly different in patients with incomplete revascularization or PTCA of an infarct-related vessel. Overall, SPECT is more accurate than exercise ECG in detecting asymptomatic restenosis. Nevertheless, incomplete revascularization and PTCA of an infarct-related artery could cause reversible perfusion defects regardless of restenosis, reducing the diagnostic value of SPECT in such patients.

[Nuclear cardiology: technical bases and clinical applications]

Although the role of nuclear cardiology is currently well consolidated, the addition of new radiotracers and modern techniques makes it necessary to continuously update the requirements, equipment and clinical applications of these isotopic tests. The characteristics of the radioisotopic drugs and examinations presently used are explained in the first part of this text. In the second, the indications of them in diagnostic and prognostic evaluation of the different coronary diseases are presented.

Diagnostic and Prognostic Use of Stress Echocardiography and Radionuclide Scintigraphy

Stress echocardiography and radionuclide scintigraphy are effective diagnostic and prognostic techniques in patients with known or suspected coronary artery disease (CAD), myocardial infarction (MI), chronic left ventricular dysfunction (LVD), and those undergoing noncardiac surgery. Both are sensitive and specific for the detection and extent of CAD. Negative tests confer a high negative predictive value for cardiac events irrespective of clinical risk. Positive studies confer a high positive predictive value for ischemic events in patients with intermediate to high clinical risk. Both provide incremental diagnostic and prognostic information relative to clinical, resting echocardiographic, and angiographic data. Meta-analysis studies have shown that the diagnostic and prognostic information provided by stress echocardiography is comparable with radionuclide scintigraphic stress tests. Stress echocardiography may be more specific for the detection and extent of CAD, whereas radionuclide scintigraphy may be more sensitive for single-vessel disease. Sensitivities are similar for the detection and extent of disease in patients with multivessel CAD.

Pharmacological stress testing

Pharmacological stress in conjunction with radionuclide myocardial perfusion imaging has become a widely used noninvasive method of assessing patients with known or suspected coronary artery disease. In the United States, over one third of perfusion imaging studies are performed with pharmacological stress. Pharmacological stress agents fall into two categories: coronary vasodilating agents such as dipyridamole and adenosine, and cardiac positive inotropic agents such as dobutamine and arbutamine. For both, in the presence of coronary artery disease (CAD), perfusion image abnormalities result from heterogeneity of coronary blood flow reserve. Vasodilating agents work directly on the coronary vessels to increase blood flow, whereas inotropic agents work indirectly by increasing myocardial work load, which then leads to an increase in coronary blood flow. Both classes of agents have high accuracies for diagnosing coronary artery disease, and they have excellent safety records with acceptably low occurrences of side effects. For dipyridamole planar thallium imaging, pooled analysis yields a sensitivity of 85% and a specificity of 87% for diagnosis of coronary disease, but there is a large variation in reported values depending on various factors, such as the extent of postcatheterization referral bias, the type of imaging (planar versus single photon emission computed tomography [SPECT]), the types of patients being studied (single versus multivessel disease, men versus women), and the imaging agent used (thallium versus one of the technetium-based agents). Diagnostic accuracies for adenosine are similar to those of dipyridamole, with reported overall sensitivities ranging from 83% to 97%, and specificities ranging from 38% to 94%. For dobutamine, pooled analyses yield a sensitivity of 82% and a specificity of 75%. There is some concern that dobutamine may interfere with uptake of technetium-99m sestamibi, lowering the sensitivity for detection of disease, and thus the vasdodilating agents are generally preferred. Pharmacological stress testing has high clinical use for risk stratifying patients with known or suspected CAD, in patients after myocardial infarction, and in patients needing noncardiac surgery. Vasodilating agents are particularly advantageous in assessing post-myocardial infarction patients, allowing testing as soon as 2 days after the event. Like patients undergoing exercise stress testing, patients with normal perfusion images by pharmacological stress have a <1% annual incidence of cardiac events. The likelihood of an event increases with the extent and severity of perfusion abnormalities. However, it is important to consider clinical variables when using perfusion imaging for risk stratification, particularly in the presurgery patients. As with exercise testing, adjunct markers such as ST segment depression during testing, lung uptake of radiotracer (if thallium is used), and ventricular cavity dilatation add additional prognostic information to that available from the perfusion images alone. The aim of current research is to find better agents that are easier to use and that have fewer side effects. MRE-0470 is an experimental vasodilating agent that is more receptor selective than adenosine and promises a lower incidence of hypotension. Arbutamine more closely simulates exercise than dobutamine, and it can be administered by a closed-loop computerized delivery device. Work is also underway to look at novel uses of pharmacological stress agents, such as acquiring gated SPECT images during dobutamine infusion to enhance detection of myocardial viability. With increasing use of noninvasive testing in elderly patients and in patients with comorbidities that preclude adequate exercise, pharmacological stress testing has become an indispensable tool for radionuclide myocardial perfusion imaging studies. A good understanding of pharmacological stress testing is essential for performing high-quality nuclear cardiology

Incremental prognostic value of adenosine myocardial perfusion single-photon emission computed tomography in women with suspected coronary artery disease

Adenosine myocardial perfusion single-photon emission computed tomography (SPECT) is now increasingly used for risk stratification of patients with known or suspected coronary artery disease. However, the incremental prognostic value of this test over clinical and historical information in a large series of women has not been examined. Thus, we studied 923 consecutive women who underwent adenosine technetium (Tc)-99m sestamibi myocardial perfusion SPECT and were followed-up for a mean period of 26+/-8 months. During the follow-up period, 77 hard events (46 cardiac deaths and 31 nonfatal myocardial infarctions) occurred. 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%/year of follow up). Patients with mildly abnormal scans had low cardiac death rates (0.9%/year of follow up); these rates increased as a function of scan abnormality (4.1% and 7.5% mortality per year of follow up in moderate and severely abnormal scans). Cox proportional hazards analysis demonstrated that after adjusting for prior myocardial infarction and diabetes mellitus (the most predictive individual clinical variables [global chi-square=22.5, p <0.001]), as well as heart rate at rest (the most predictive physiologic variable [chi-square=3.8; p=0.05]), the most predictive nuclear variable (summed stress score [chi-square=48.5; p <0.0001]) added significant incremental prognostic information (global chi-square increased from 22.5 to 56.2 [p <0.0001]). In conclusion, adenosine myocardial perfusion SPECT added significant incremental prognostic information to clinical and physiologic variables in women. Normal scans were associated with an excellent prognosis. In contrast, patients with moderately to severely abnormal scans were at a higher risk for future cardiac events.

The 24-hour Tl-201 image in dual isotope myocardial perfusion scintigraphy: clinical utility and prognostic significance

This study assessed the effect on clinical decision making and the possible prognostic significance of the 24-hour Tl-201 image in patients undergoing Tl-201-MIBI dual-isotope myocardial scintigraphy. The records of all patients who underwent 24-hour Tl-201 imaging as part of their myocardial perfusion study from 1994 to 1996 were reviewed. Follow-up evaluations were obtained from the referring physician or by direct patient contact. Fifty-six patients underwent a total of 57 studies; four patients were lost to follow-up. Of the 53 studies evaluated, 29 showed no change between the standard rest images and the 24-hour images; these patients were reported to have myocardial scar. Of these 29 patients, 25 were treated medically without further evaluation; 24 of these 25 patients remained stable. Four of the 29 patients had further evaluation; 2 patients had coronary artery bypass graft, 1 had a stent placed, and 1 remained stable. Twenty-four patients showed definite improvement or normalization of their study results by 24 hours; they were reported as ischemic. Of these 24 patients, 11 were treated medically without further evaluation; 9 remained stable, whereas 2 had adverse events. The remaining 13 patients required further evaluation; 4 remained stable, whereas 9 had adverse events (4 = increasing angina; 1 = stent; 1 = rotoblator; 2 = percutaneous transluminal coronary angioplasty; 1 = death). Twenty-four-hour imaging contributes to clinical decision making and may identify a subset of patients at risk for subsequent complications.

Thallium reinjection versus standard stress/delay redistribution imaging for prediction of cardiac events

OBJECTIVES

The purpose of this study was to compare thallium reinjection with standard stress/delay redistribution for the prediction of cardiac events.

BACKGROUND

Although thallium reinjection enhances the detection of viable myocardium, its contribution to prognosis over stress/delay redistribution in a general referral population has not been clearly evaluated.

METHODS

This retrospective analysis included 366 consecutive patients with coronary artery disease who underwent stress/delay redistribution imaging and thallium reinjection scintigraphy, with a mean follow-up of 33+/-12 months.

RESULTS

Cardiac events occurred in 48 patients (40 deaths, 8 myocardial infarctions). Of the 366 original patients, 159 demonstrated ischemia by stress/delay redistribution, 107 showed ischemia by reinjection only, and 100 showed infarction only. Cardiac events occurred in 20 patients (12.6%) with stress/delay redistribution, 13 patients (12%) with ischemia detected by thallium reinjection only and 15 patients (15%) with infarction only. The size of the reversible thallium defect by either stress/delay redistribution imaging or reinjection scintigraphy did not predict cardiac events. Independent predictors of cardiac events included left ventricular cavity size, the size of the abnormal perfusion defect and patient age.

CONCLUSIONS

Thallium reinjection does not contribute independent prognostic utility for cardiac events when compared with stress/delay redistribution. Left ventricular dilation and the size of the post-stress defect were predictors of cardiac events.

Evaluation of exercise thallium scintigraphy versus exercise electrocardiography in predicting survival outcomes and morbid cardiac events in patients with single- and double-vessel disease. Findings from the Angioplasty Compared to Medicine (ACME) Study

OBJECTIVES

We sought to evaluate the prognostic ability of cardiac exercise stress tests in predicting cardiac mortality and morbidity in a low risk group of patients with established coronary artery disease (CAD).

BACKGROUND

Although previous studies have demonstrated the superior value of stress nuclear cardiac scintigraphy in the prognosis of patients with CAD, none of these studies have focused on patients with a proven angiographic low risk profile (i.e., single- and double-vessel CAD).

METHODS

Three hundred twenty-eight patients with documented single- and double-vessel disease were treated by random assignment to percutaneous transluminal coronary angioplasty or medical therapy in the Angioplasty Compared to Medicine (ACME) trial. Six months after randomization, maximal symptom-limited exercise tests were performed with electrocardiography (n = 300) and thallium scintigraphy (n = 270). Patients were followed up for a minimum of 5 years thereafter.

RESULTS

A reversible thallium perfusion deficit documented after 6 months of either therapy was associated with an adverse mortality outcome (18% mortality rate with a reversible thallium perfusion defect and 8% mortality rate with no reversible thallium perfusion deficit, p = 0.02). Moreover, an important mortality gradient was demonstrated in relation to the number of reperfusing defects (0 = 7%, 1 to 2 = 15%, >3 = 20%, p = 0.04). Exercise electrocardiography did not predict this mortality outcome.

CONCLUSIONS

A reversible thallium perfusion deficit demonstrated 6 months after medical therapy or coronary angioplasty is a valuable prognostic marker in patients with angiographically documented single- and double-vessel disease and is superior to exercise electrocardiography in this regard.

[Isotopic ventriculography in healthy young volunteers. Their response to different types of stress]

BACKGROUND

Due to the increasing use of pharmacologic stress tests and the lack of comparative studies on ventricular function, this study was designed to establish the average limits in ventricular function with different kinds of stress, and to compare the response among them.

METHODS

A randomized, open, controlled phase II clinical trial in 4 parallel groups was designed. Forty healthy male volunteers between 18 and 25 years were randomized into 4 groups of 10 individuals each: physical exercise (group 1), dobutamine (group 2), adenosine triphosphate (ATP) (group 3) and dipyridamole (group 4). Each volunteer underwent equilibrium radionuclide angiography, at rest and during stress.

RESULTS

The global and regional ejection fraction increased significantly with the 4 kinds of stress. The maximal increase was reached with dobutamine and the minimal with dipyridamole. Physical exercise induced an increase in global ejection of 13 +/- 5%; dobutamine 16 +/- 6%; ATP 9 +/- 3% and dipyridamole 4 +/- 3%.

CONCLUSIONS

The global and regional ejection fraction increases significantly more with dobutamine than with the other stress tests. Dipyridamole elicits the minimal increase.

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.

Prognostic importance of scintigraphic left ventricular cavity dilation during intravenous dipyridamole technetium-99m sestamibi myocardial tomographic imaging in predicting coronary events

Left ventricular (LV) cavity dilation during stress myocardial perfusion imaging has been associated with multivessel disease, and may be an independent prognostic marker in addition to perfusion defects. The present study examines the predictive value for future cardiac events of transient or fixed LV dilation during dipyridamole technetium-99m (Tc-99m) sestamibi single-photon emission computed tomography (SPECT) imaging. The study included 512 consecutive patients who underwent SPECT imaging with Tc-99m sestamibi after dipyridamole infusion. Transient LV dilation was seen in 70 patients (14%) and 74 had fixed cavity dilation (14%); cavity size was normal in 368 patients (72%). Each perfusion scan was classified as normal or abnormal, and if abnormal, defects were categorized as transient or fixed, and as small, medium, or large (depending upon the number of abnormal vascular territories). Events during a mean follow-up of 12.8 +/- 6.8 months were tabulated by direct review of hospital charts and death certificates. The cardiac event rate (cardiac death or nonfatal infarction) was 1.9% in patients with normal cavity size, 11.4% with transient LV dilation, and 13.5% with fixed LV dilation (p < 0.01). Compared with patients with normal cavity size, those with transient LV dilation were more likely to sustain a myocardial infarction (p < 0.01) and those with fixed dilation more frequently suffered cardiac death (p < 0.01) and hospitalization for heart failure (p < 0.01). The group with the highest risk had both a large perfusion defect and cavity dilation. By Cox proportional hazard regression analysis, both transient and fixed LV dilation were strong independent predictors of cardiac events. Transient or fixed LV dilation are commonly seen during dipyridamole Tc-99m sestamibi SPECT imaging (14% incidence for each) and are useful predictors of cardiac events.

Prediction of late cardiac events by dipyridamole thallium scintigraphy in patients with intermittent claudication and occult coronary artery disease

Concomitant coronary artery disease often occurs in patients with peripheral vascular disease, but it may be asymptomatic. Despite being asymptomatic, cardiovascular events are the main source of morbidity and mortality in this group of patients. Dipyridamole thallium scintigraphy has been shown to be of prognostic value in patients with peripheral vascular disease and symptomatic coronary artery disease, but its effect on the long-term outcome in the asymptomatic group of patients is less defined. Eighty-four consecutive patients with peripheral vascular disease and no symptoms of coronary artery disease were therefore evaluated by clinical assessment, dipyridamole thallium imaging, radionuclide ventriculography, and cardiac catheterization and followed for a mean of 66 months. Abnormal perfusion patterns were found on thallium scintigraphy in 48 patients (57%); fixed, mixed, and reversible defects were present in 14 (17%), 11 (13%), and 23 (27%) patients, respectively. Significant coronary artery disease was present in 52 patients (69%) and mean left ventricular ejection fraction was 44%. During the follow-up period, 23 patients had a cardiac event (nonfatal myocardial infarction or cardiac death). Univariate analysis of 15 clinical, scintigraphic, radionuclide, and angiographic variables revealed that age, angiographic extent of coronary artery disease, and an abnormal thallium scan were significant predictors of subsequent cardiac events. Multivariate stepwise logistic regression analyses selected fixed and mixed thallium defects and diffuse coronary artery disease as the only significant independent predictors of outcome. Thus, the present study shows the value of dipyridamole thallium scintigraphy as a valuable prognostic indicator for long-term event-free survival in a cohort of patients with peripheral vascular disease and no history or symptoms of coronary artery disease.

Stress echocardiography in elderly patients with coronary artery disease: applicability, safety and prognostic value of dobutamine and adenosine echocardiography in elderly patients

OBJECTIVES

Our aim was to determine the applicability, safety and prognostic value of adenosine and dobutamine stress echocardiography in patients > or = 70 years old.

BACKGROUND

These tests are sometimes mandatory because of difficulties and inaccuracies in interpreting traditional electrocardiographic stress tests. Furthermore, if these tests could be used to avoid coronary arteriography and cardiac catheterization, they would become essential in the care of the elderly, whose numbers are increasing.

METHODS

We performed coronary arteriography and dobutamine and adenosine stress echocardiographic tests in 120 patients (72 men) > or = 70 years old who entered the hospital because of chest pain and had known or suspected coronary artery disease. The stress tests were performed on separate days, within 2 weeks of coronary arteriography. Both the arteriograms and the echocardiograms were analyzed by two experts who had no knowledge of the patients' other data or the other interpreter's report. Tests were judged to have positive or negative results, and the patients were followed up for the development of cardiac events. Univariate and multivariate analyses and other statistical modalities were applied for comparisons.

RESULTS

Documented coronary artery disease was found in 89 patients. During the 14 +/- 7 of follow-up, cardiac events developed in 50 patients, including 3 (7.9%) of 38 patients with negative dobutamine and 12 (20.7%) of 58 patients with negative adenosine test results. Demonstration of any abnormality on stress echocardiography was an independent factor for cardiac events, both for dobutamine (relative risk 7.3) and for adenosine (relative risk 3.0). Both cessation of dobutamine or adenosine tests and diagnosis of disease in two or more coronary vessels were also independent predictors. ST segment depression > or = 1mm was related to future events only with the dobutamine test.

CONCLUSIONS

These echocardiographic stress tests proved safe and well tolerated. They successfully stratified this cohort of elderly patients with coronary artery disease to low or high risk subgroups for subsequent cardiac events.

Prediction of in-hospital cardiac events using dipyridamole-thallium scintigraphy performed very early after acute myocardial infarction

BACKGROUND AND HYPOTHESIS

Ischemic complications occur frequently during hospitalization after acute myocardial infarction. Dipyridamole-thallium scintigraphy performed early after admission can detect residual ischemia, may have additional prognostic value and be useful in the management of these patients.

METHODS

Dipyridamole infusion and 201thallium imaging were performed on the third day of infarction in 114 consecutive patients. Coronary angiography was performed before hospital discharge in 90% of patients and exercise testing was performed at the time of discharge in patients without contraindications.

RESULTS

Side effects occurred in 28 patients, but they were mild and transient or rapidly reversed with intravenous aminophylline. During hospitalization, three patients died and four had a nonfatal reinfarction. Patients with these major cardiac events had previously shown a higher prevalence of reversible perfusion defects during testing (71 vs. 31%, p < 0.05). In addition, 19 patients had early recurrent ischemia requiring early in-hospital revascularization. Overall, cardiac events defined as death, reinfarction, or early myocardial revascularization occurred in 22 patients. Of the patients with these events, 68% had thallium redistribution on initial myocardial scanning compared with 25% of patients without events (p = 0.0001). Patients with cardiac events also showed a higher number of myocardial segments with reversible perfusion defects (1.8 +/- 2.2 vs. 0.6 +/- 1.3, p = 0.001). Logistic regression analysis revealed that among all the other clinical, scintigraphic, and angiographic variables, the presence of thallium redistribution on the dipyridamole-thallium scan was the only independent predictor of cardiac events, increasing the risk by sixfold. Furthermore, during a 1-year follow-up, 14 other patients had ischemic events. Of these, 64% had previously shown thallium redistribution during early dipyridamole testing compared with 19% of patients without cardiac events (p < 0.001).

CONCLUSIONS

Intravenous dipyridamole-thallium-scintigraphy performed very early after myocardial infarction is safe and useful to predict in-hospital ischemic events.

Prognostic value of high dose dipyridamole echocardiography in patients with chronic coronary artery disease and preserved left ventricular function

OBJECTIVES

The prognostic value of dipyridamole echocardiography was assessed in patients with chronic coronary artery disease and preserved left ventricular function.

BACKGROUND

Few data are available on the prognostic value of dipyridamole echocardiography in patients with a low risk of cardiac events.

METHODS

Two hundred sixty-eight consecutive patients with stable, proven or suspected coronary artery disease and ejection fraction > or = 0.40 underwent high dose (up to 0.84 mg/kg body weight) dipyridamole echocardiography. In 204 patients definite exercise electrocardiographic (ECG) results were also available.

RESULTS

During a mean (+/- SD) follow-up period of 16 +/- 8 months (range 6 to 36), 33 spontaneous events occurred: 15 "hard" events (cardiac death [n = 6], myocardial infarction [n = 9]) and 18 "soft" events (unstable angina). Events occurred more frequently in patients with positive findings on dipyridamole echocardiography (59% vs. 3%, p < 0.001; hard events 24% vs. 2%, p < 0.01). A positive response at the low dose (up to 0.56 mg/kg) identified patients with a high incidence of hard events (7 of 16 patients, sensitivity 50%, specificity 96%). In patients with an exercise ECG, a comparable sensitivity for cardiac events was found (89% vs. 93%, p = NS), but dipyridamole echocardiography was more specific (91% vs. 61%, p < 0.01). A positive response on the low work load exercise ECG (< 8 min) and a positive response to low dose dipyridamole echocardiography had similar accuracy (82% vs. 90%, p = NS). Cox analysis identified dipyridamole echocardiography as the best predictor of cardiac events (odds ratio [OR] 20.9, 95% confidence interval [CI] 10.8 to 37.9); the highest risk of hard events was found in patients with a positive response to low dose dipyridamole echocardiography (OR 25.4, 95% CI 12.2 to 54.1).

CONCLUSIONS

In patients with chronic coronary artery disease and a low incidence of cardiac events, dipyridamole echocardiography was effective in prognostic stratification, and positive low work load exercise ECG results were a reliable predictor of subsequent events. Consequently, dipyridamole echocardiography should be considered a complementary tool in the presence of high work load positivity or ambiguous exercise ECG results.

Stress imaging. Current clinical options for the diagnosis, localization, and evaluation of coronary artery disease

As technology advances, new methods evolve. In this article, the methods of stress testing and related imaging in coronary disease are addressed, and dynamic and pharmacologic stress, direct and indirect methods, are defined and evaluated. The stress imaging methods related to the modalities of scintigraphy and ultrasound are reviewed and their advantages and disadvantages assessed in view of scientific and economic factors.

Prognostic significance of ST-segment depression during adenosine perfusion imaging

To determine the significance of ST-segment depression during adenosine perfusion imaging for predicting future cardiac events, 188 patients with interpretable electrocardiograms were assessed 1 to 3 years (mean 21.5 +/- 6.6 months) after adenosine testing. At least 1 mm of ST-segment depression was observed in 32 (17%) patients, with > or = 2 mm of ST-segment depression in 10 (5.3%). Thirty-seven cardiac events occurred during the study period: 2 cardiac deaths, 5 nonfatal myocardial infarctions, 6 admissions for unstable angina, and 24 revascularizations. Univariate predictors of events were a history of congestive heart failure, previous non-Q-wave myocardial infarction, previous coronary angioplasty, use of antianginal medication, ST-segment depression during adenosine infusion (particularly > or = 2 mm), any reversible perfusion defect, transient left ventricular cavity dilation, and the severity of perfusion defects. Multivariate analysis identified > or = 2 mm ST-segment depression as the most significant predictor of cardiac events (relative risk [RR] = 6.5; p = 0.0001). Other independent predictors of events were left ventricular dilation (RR = 3.8; p = 0.002), previous coronary angioplasty (RR = 3.3; p = 0.001), a history of non-Q-wave myocardial infarction (RR = 2.3; p = 0.01), and the presence of any reversible defect (RR = 2.0; p = 0.05). We conclude that ST-segment depression occurs uncommonly during adenosine infusion, but the presence of > or = 2 mm of ST-segment depression is an independent predictor of future cardiac events and provides information in addition to that obtained from clinical variables and the results of adenosine perfusion imaging.

Long-term risk stratification with dipyridamole imaging

This study was undertaken to assess the reliability of clinical parameters and dipyridamole-thallium 201 images for predicting the occurrence of future cardiac events (nonfatal myocardial infarction or cardiac death). Dipyridamole myocardial perfusion imaging is routinely performed in patients who have possible or known coronary disease and a low exercise tolerance. A total of 753 patients underwent clinical assessment and semiquantitative dipyridamole-201TI imaging and were followed up as outpatients. Patients who underwent coronary revascularization during the follow-up period were excluded from the study because the decision to intervene would have been based at least in part on the test itself. There were 82 cardiac events and 54 noncardiac deaths, and 11 patients were lost to follow-up after a mean follow-up of 15 months. With use of a quantitative index reflecting the amount of jeopardized myocardium, patients could be stratified by dipyridamole imaging into subsets with coronary morbidity and mortality rates ranging from 1% to 89%, (p = 0.0001). When clinical and scintigraphic variables were subjected to backward stepwise logistic regression analysis, the significant predictors of cardiac events were the jeopardized myocardium index by scintigraphy (p < 0.0001), left ventricular hypertrophy on the electrocardiogram (p = 0.0009), and transient dipyridamole-induced left ventricular cavitary dilatation (p = 0.0073). Quantitative dipyridamole-201TI imaging appears to be a powerful predictor of future cardiac events in patients with coronary disease and a low exercise tolerance and is a potentially useful contributor to risk-profile assessment and to the treatment of these patients.

Preoperative clinical assessment and dipyridamole thallium-201 scintigraphy for prediction and prevention of cardiac events in patients having major noncardiovascular surgery and known or suspected coronary artery disease

The aim of this study was to assess the relative prognostic use of clinical risk stratification and intravenous dipyridamole thallium-201 scintigraphy in patients with an intermediate to high prevalence of coronary artery disease (CAD) who have undergone major noncardiovascular surgery, and to assess the effects of medical therapy or coronary revascularization based on the result of this clinical scintigraphic screening on perioperative cardiac morbidity and mortality. Patients (n = 161) with an intermediate to high likelihood of CAD had clinical assessment and intravenous dipyridamole planar thallium-201 testing which was analyzed semiquantitatively. Cardiac events were cardiac death (n = 9), nonfatal myocardial infarction (n = 6), acute pulmonary edema (n = 6), and unstable angina (n = 4). Multiple (> or = 2) clinical risk variables predicted any cardiac event (p = 0.04). Presence of multiple (> or = 2) abnormal thallium-201 segments was the only independent predictor of cardiac death or nonfatal myocardial infarction (p < 0.001), and was the most powerful multivariate predictor of any cardiac event (p < 0.002). Patients with an abnormal dipyridamole thallium-201 scan had a higher risk of perioperative cardiac death, myocardial infarction (18% vs 2%; p < 0.001), or any perioperative cardiac event (27% vs 6%; p < 0.001) when compared with those with a normal scan. Preoperative changes in anti-ischemic therapy or coronary revascularization in 36 of 72 patients with abnormal dipyridamole thallium-201 studies reduced perioperative death or myocardial infarction from 31% to 6% (p < 0.01), and all cardiac events from 47% to 8% (p < 0.001) compared with those in patients without intervention.(ABSTRACT TRUNCATED AT 250 WORDS)

Truly silent ischemia and the relationship of chest pain and ST segment changes to the amount of ischemic myocardium: evaluation by supine bicycle stress echocardiography

OBJECTIVES

The objectives of this study were 1) to determine the relationship between the amount of exercise-induced ischemic myocardium and the presence or absence of chest pain and ST segment depression, and 2) to define the incidence and characteristics of "truly silent ischemia," that is, ischemia that is not manifested by symptoms or electrocardiographic (ECG) findings.

BACKGROUND

There are no prior data relating ischemia to chest pain and ST depression. Thallium-201 imaging studies have evaluated perfusion but not ischemia. In contrast, supine bicycle stress echocardiography demonstrates exercise-induced ischemic dysfunction.

METHODS

Supine bicycle stress echocardiography and arteriography were performed in 130 patients and the severity and geographic extent of ischemic myocardium were compared in three groups. On exercise, Group I patients had both chest pain and ST segment depression (symptomatic ischemia), Group II patients ST depression without chest pain (asymptomatic ischemia) and Group III patients had neither chest pain nor ST depression (truly silent ischemia).

RESULTS

There were no differences among groups in arteriographic characteristics. The incidence of "truly silent ischemia" was 43%. The number of abnormally contracting ischemic segments, average score per segment and sum of scores were virtually identical in Groups I and II and significantly greater than in Group III for the patients (p < 0.01 to < 0.0001), for the vessels as a group (p < 0.01 to < 0.0001) and for the left anterior descending (p < 0.01 to < 0.0001) and right (p < 0.05) coronary arteries. By multivariate analysis, positive findings on the stress ECG was the single most significant variable in relation to the amount of ischemia (p < 0.001); exercise chest pain had no significant relationship.

CONCLUSIONS

Exercise-induced ST segment depression is the single most significant variable in relation to the amount of ischemic myocardium; exercise-induced chest pain is not related to the amount of ischemia. Patients with "truly silent ischemia" constitute almost 50% of patients with coronary artery disease and have less ischemia than do patients with ECG indications of ischemia, with or without chest pain.

Pretreatment with theophylline does not affect adenosine-induced thallium-201 myocardial imaging

This study was designed to evaluate the effects of intravenous theophylline given before intravenous adenosine for thallium-201 imaging. Sixteen patients with known reversible thallium-201 defects were randomized to a double-blind crossover study of a 45-minute infusion of placebo or theophylline (given as the ethylenediamine salt, aminophylline, mean concentration 16.1 mg/L) before adenosine thallium-201 imaging. Adenosine was infused for 6 minutes at a rate of 140 micrograms/kg/min. Thallium-201 (2.5 to 3.0 mCi) was administered after 3 minutes of infusion. Blood pressure, heart rate, symptoms, and the electrocardiogram were monitored continuously. Planar thallium-201 imaging was obtained in three standard views and was interpreted using blinded segmental analysis and computerized quantitation. Systolic and diastolic blood pressure at baseline and during adenosine administration were similar following treatment with theophylline and placebo. The increase in heart rate observed during adenosine infusion was significantly reduced by theophylline pretreatment. Adenosine-induced symptoms (both cardiac and noncardiac) as well as ischemic electrocardiographic changes were significantly reduced after theophylline infusion (p < 0.05). In one patient, Mobitz type II heart block seen during adenosine infusion following placebo was absent with theophylline pretreatment. The size of adenosine-induced thallium-201 defects was unchanged by theophylline infusion using either segmental analysis (8 +/- 4 vs 9 +/- 5) or a computerized score (47 +/- 27 vs 45 +/- 21). Despite reduction in both symptoms and ischemic electrocardiographic changes, theophylline does not alter thallium-201 imaging following intravenous adenosine infusion.

Silent myocardial ischemia

The documentation of abnormalities related to myocardial ischemia, whether symptomatic or silent, is of central importance. Whenever this information is available, it should be used in the overall assessment of the patient at risk for adverse outcome. The level of concern for treatment of CAD should be based on the risk implications associated with the ischemia-related abnormalities detected during objective testing rather than on the presence or absence of pain. The exercise stress test is still the single most useful test to begin the evaluation of a patient with an analyzable ST segment. In persons suspected of having CAD, the detection of ischemic-type ST-segment depression, at a low workload (e.g., < 120 beats/min or < 6.5 METS) of > 2 mm magnitude or persisting for more than 6 min implies high risk for adverse outcome. Asymptomatic ischemia during everyday activities, detected by Holter monitoring, in the high-risk patient, most probably adds additional risk beyond the risk of an abnormal stress test alone. Left ventricular imaging by two-dimensional echocardiography, RNA, angiogram, vest, etc, showing an ejection fraction > or = 40%, reversible wall motion abnormalities in multiple regions and redistribution defects or a failure to increase ejection fraction during exercise even if the patient remains asymptomatic, also imply high risk. The presence of any of these abnormal findings, regardless of symptoms, should therefore prompt as high a degree of concern as with ischemia-related signals associated with pain. Thus any therapy chosen should be directed toward elimination of transient ischemia, not just relief of symptoms that may or may not be ischemia related. If this course is chosen, the efficacy of the therapeutic regimen and possible progression of CAD should be assessed with follow-up testing for ischemia. We believe that risk factor modification and aspirin should be considered for most, if not all, patients in whom ischemia, silent or symptomatic, is suspected or detected. If symptoms or ischemia suggesting low risk is present, anti-ischemic medical therapy may be considered, but follow-up is advised. If a high-risk ischemic signal, even without symptoms, is detected, medical therapy should be used to attempt to modify the signal. If the ischemic signal suggesting high risk persists despite medical therapy, revascularization should be considered. Until additional data from large clinical trials are available, this approach appears to have the greatest likelihood of modifying the adverse outcome of CAD.

Angiographic and hemodynamic determinants of myocardial ischemia during adenosine thallium-201 scintigraphy in coronary artery disease

BACKGROUND

Myocardial ischemia attributed to coronary steal may occur in some patients receiving pharmacological coronary vasodilation. ECG ST-segment depression is a marker of myocardial ischemia in these patients, but the factors determining the presence or absence of ischemia are not well known.

METHODS AND RESULTS

To examine the angiographic, hemodynamic, and scintigraphic determinants of adenosine-induced ischemic ST-segment depression in patients with coronary artery disease, we studied 65 consecutive patients (45 men and 20 women; mean age, 65 +/- 12 years) who showed reversible perfusion defects during adenosine (140 micrograms.kg-1.min-1 for 6 minutes) 201Tl single-photon emission computed tomography. Patients with prior myocardial infarction were excluded. Ischemic ST depression occurred in one third of the whole cohort (22 of 65 patients). The presence of coronary collateral vessels (p = 0.001), systolic blood pressure at baseline (p = 0.006), and adenosine-induced anginal chest pain (p = 0.011) were the only significant independent predictors of ischemic ST-segment depression by stepwise logistic regression analysis. Rate-pressure product at baseline, systolic blood pressure, heart rate, rate-pressure product, increase in heart rate, and rate-pressure product during adenosine infusion and maximal percent stenosis were variables also significantly related to ischemic ST depression by univariate analysis but were not predictive after the three primary variables were included in the regression model. Perfusion defect size, number of diseased vessels, and age did not correlate with ST-segment depression.

CONCLUSIONS

The presence of collaterals, which may predispose to coronary collateral steal, is the most significant correlate of ischemic ST-segment depression during adenosine infusion. Systolic blood pressure at baseline, which may affect the myocardial oxygen supply/demand ratio and anginal chest pain induced by adenosine, are additional variables related to ischemic ST-segment depression during adenosine infusion.

Prognostic value of thallium-201 myocardial perfusion imaging in three primary patient populations

Knowledge of a patient's coronary anatomy alone is often insufficient to predict who will benefit from revascularization. Risk of cardiac events is related more to the presence of viable myocardium supplied by coronary arteries that are hemodynamically significant. Myocardial perfusion imaging with thallium-201 has been shown to reveal the presence and extent of jeopardized viable myocardium. In addition, thallium-201 imaging can demonstrate exercise-induced left ventricular dysfunction, manifested by increased thallium-201 myocardial imaging has important prognostic value in a wide spectrum of patients with coronary artery disease. The use of thallium-201 to predict cardiac events in patients with known or suspected coronary artery disease, in patients following myocardial infarction, and in patients undergoing noncardiac surgery is reviewed.

Determination of perioperative cardiac risk by adenosine thallium-201 myocardial imaging

To determine the predictive value of adenosine thallium-201 myocardial imaging for perioperative cardiac events, 60 consecutive patients referred for preoperative cardiac evaluation were studied before vascular (n = 25), orthopedic (n = 14), or general (n = 21) surgery. Tomographic (n = 52) and planar (n = 8) thallium-201 imaging was performed after adenosine infusion at a rate of 140 micrograms/kg/min for 6 minutes. Two blinded expert observers graded results of adenosine thallium-201 studies as normal (33%), fixed defect only (2%), reversible defect only (48%), and combined (fixed and reversible) defects (17%). After 6 +/- 3 months of follow-up, 81% proceeded to surgery and 43% underwent preoperative coronary angiography. Clinical variables that correlated with perioperative cardiac events were a history of diabetes mellitus (p = 0.05), left bundle branch block (p = 0.02), and left ventricular hypertrophy (p = 0.06) on the resting ECG. This clinically "high-risk" group had an event rate of 22% as compared with no cardiac events in patients in the "low-risk" group without these clinical characteristics (p = 0.005). Stepwise logistic regression analysis revealed that the presence of a combined (fixed and reversible) adenosine thallium-201 defect (p = 0.0007), three-vessel coronary artery disease (p = 0.001), and left bundle branch block (p = 0.02) was predictive of subsequent cardiac events with relative risk ratios of 4.9, 2.9, and 2.2, respectively. Therefore the presence of an adenosine thallium-201 perfusion defect is correlated with and predictive of an increased risk of perioperative cardiac events in patients referred for preoperative risk evaluation.