Superiority of quantitative exercise thallium-201 variables in determining long-term prognosis in ambulatory patients with chest pain: a comparison with cardiac catheterization

The purpose of this study was to determine the prognostic utility of quantitative exercise thallium-201 imaging and compare it with that of cardiac catheterization in ambulatory patients. Accordingly, long-term (4 to 9 years) follow-up was obtained in 293 patients who underwent both tests for the evaluation of chest pain: 89 had undergone coronary artery bypass graft surgery within 3 months of testing and were excluded from analysis, 119 experienced no cardiac events and 91 had an event (death in 20, nonfatal myocardial infarction in 21 and coronary artery bypass operations performed greater than 3 months after cardiac catheterization in 50). When all variables were analyzed using Cox regression analysis, the quantitatively assessed lung/heart ratio of thallium-201 activity was the most important predictor of a future cardiac event (chi 2 = 40.21). Other significant predictors were the number of diseased vessels (chi 2 = 17.11), patient gender (chi 2 = 9.43) and change in heart rate from rest to exercise (chi 2 = 4.19). Whereas the number of diseased vessels was an important independent predictor of cardiac events, it did not add significantly to the overall ability of the exercise thallium-201 test to predict events. Furthermore, information obtained from thallium-201 imaging alone was marginally superior to that obtained from cardiac catheterization alone (p = 0.04) and significantly superior to that obtained from exercise testing alone (p = 0.02) in determining the occurrence of events. In addition, unlike the exercise thallium-201 test, which could predict the occurrence of all categories of events, catheterization data were not able to predict the occurrence of nonfatal myocardial infarction. The exclusion of bypass surgery and previous myocardial infarction did not alter the results. In conclusion, data from this study demonstrate that exercise thallium-201 imaging may be superior to data from both exercise testing alone and cardiac catheterization data alone for predicting future events in ambulatory patients who have undergone both exercise thallium-201 imaging and catheterization for the evaluation of chest pain.     

Prognostic value of thallium-201 myocardial perfusion imaging in patients with unstable angina who respond to medical treatment

Although the prognostic value of thallium-201 imaging is well established, its ability to risk stratify patients who present with unstable angina is unclear. Fifty-two consecutive patients admitted with unstable angina who responded to medical treatment and underwent stress thallium-201 imaging within 1 week of discharge were studied. Patients were followed up for 39 +/- 11 months. Cardiac events included cardiac death (n = 3), nonfatal myocardial infarction (n = 4) and admission for unstable angina or revascularization (n = 17). The ability of thallium-201 data (redistribution, fixed defects, normal) to predict cardiac events was compared with clinical data (age, gender, prior myocardial infarction, anginal syndrome, rest and stress electrocardiogram) and cardiac catheterization data using logistic regression. Thallium-201 redistribution was the only significant predictor of cardiac death or nonfatal myocardial infarction (p less than 0.05). The number of myocardial segments with thallium-201 redistribution (p less than 0.0005) and a history of prior myocardial infarction (p less than 0.05) were the only significant predictors of all cardiac events. Cardiac death or nonfatal myocardial infarction occurred more frequently in patients with thallium-201 redistribution (6 [26%] of 23) than in those without redistribution (1 [3%] of 29, p less than 0.05). Similarly, total cardiac events developed more frequently in patients with thallium-201 redistribution (p less than 0.001). Stress thallium-201 imaging has important prognostic value in patients admitted with unstable angina who respond to medical therapy and can identify subgroups at high versus low risk for future cardiac events.     

Clinical relevance of exercise-induced ventricular arrhythmias in suspected coronary artery disease

Because there is controversy regarding the clinical relevance of exercise-induced ventricular arrhythmias, we analyzed their significance in 383 patients who had undergone both exercise thallium-201 stress-testing and cardiac catheterization. Two-hundred twenty-one patients (58%) had no exercise-induced ventricular arrhythmias while 162 (42%) did. There was no difference between patients with and without exercise-induced ventricular arrhythmias in terms of previous myocardial infarction (p = 0.61), incidence of fixed thallium-201 defects (0.06), number of diseased vessels (p = 0.09) and resting left ventricular ejection fraction (p = 0.06). In contrast, evidence of provocable ischemia (redistribution on thallium-201 and ST-segment depression on the electrocardiogram) were more likely (p less than 0.02) to be seen in patients with exercise-induced ventricular arrhythmias. Discriminant function analysis revealed that these 2 variables best separated patients with and without exercise-induced ventricular arrhythmias. In a 4- to 8-year follow-up, 89 patients had adverse cardiac events. Of these 89, there were 41 deaths, 9 nonfatal myocardial infarctions and 39 coronary revascularization procedures performed later than 3 months after catheterization. Patients with exercise-induced ventricular arrhythmias were more likely (p = 0.01) to have these events than those without these arrhythmias. Moreover, these arrhythmias provided independent prognostic information beyond that provided by the thallium-201 stress test and coronary angiography. We conclude that exercise-induced ventricular arrhythmias are associated with exercise-induced ischemia and provide prognostic information which adds marginally to that provided by other noninvasive and invasive parameters in ambulatory patients being evaluated for chest pain.     

Silent versus symptomatic ischemia during a thallium-201 exercise test

One hundred thirty-four patients with redistribution on a thallium-201 exercise test who did not experience angina (group 1) were compared with 134 patients also having redistribution who had angina during the test (group 2). The groups were matched by age, sex, and peak exercise heart rate. Although patients in both groups achieved an equivalent exercise level, patients in group 1 had less frequent (53 vs 71%, p < 0.005) and less severe (0.15 ± 0.13 vs 0.20 ± 0.13 mV, p < 0.005) ischemic ST-segment depression. Group 1 also had less ischemic thallium-201 images in terms of the number of redistributing defects, the severity of the worst redistributing defect, and an ischemic index composite of both extent and severity. Patients in group 1 were less likely to undergo early revascularization (12 vs 29%, p < 0.005), but in the remaining patients the occurrence of adverse cardiac events was similar (21% vs 29%, P = not significant). By multivariate analysis, only the ischemic index correlated with early revascularization in group 1 (p = 0.0017), whereas the percent maximal predicted heart rate correlated best in group 2 (p = 0.0003). In group 1 the ratio of lung/heart thallium-201 uptake correlated best with an outcome of nonfatal myocardial infarction or cardiac death (p = 0.0024); in group 2 the presence of fixed left ventricular dilatation did (p = 0.0022). Thus, patients with exercise-induced thallium-201 redistribution without angina have less ischemia than patients experiencing angina. They are also less likely to undergo early revascularization, but their prognosis is otherwise similar to patients with angina during the test.     

Usefulness of residual ischemic myocardium within prior infarct zone for identifying patients at high risk late after acute myocardial infarction

This study examines the prognostic implications of ischemia within the territory of a prior acute myocardial infarction (AMI) vs ischemia at a distance, which develops late after AMI. Sixty-one consecutive patients who underwent both exercise thallium-201 (TI-201) imaging and cardiac catheterization for evaluation of chest pain that developed after discharge from the hospital for AMI form the study group. Mean interval between infarction to the TI-201 study was 10 +/- 17 months. Initial and 2-hour delay TI-201 images were analyzed quantitatively to determine the presence and location (within vs outside the prior infarct zone) of TI-201 redistribution, a marker of ischemic viable myocardium. TI-201 imaging results were separated into 3 groups based on presence and location of TI-201 redistribution: no significant TI-201 redistribution was found in 16 patients; in 29, TI-201 redistribution was confined to the infarct zone; and in 16, TI-201 redistribution was outside the infarct zone. Stepwise multivariate logistic regression analysis was used to examine the comparative ability of TI-201 results and other patient variables to predict cardiac events. For total cardiac events (cardiac death, recurrent nonfatal AMI, unstable angina and coronary revascularization), both the presence of any TI-201 redistribution and multivessel angiographic coronary artery disease were significant predictors. However, when coronary revascularization was excluded as an endpoint, TI-201 redistribution limited to the prior infarct zone was the only significant predictor of cardiac events. All 8 cardiac events occurred in patients with T1-201 redistribution limited to the infart zone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ability of dipyridamole-thallium-201 imaging one to four days after acute myocardial infarction to predict in-hospital and late recurrent myocardial ischemic events

The ability of dipyridamole-thallium-201 imaging to predict in-hospital and late cardiac events when performed very early (62 +/- 21 hours, range 23 to 102) after acute myocardial infarction (AMI) was tested in 50 patients. During hospitalization, 1 patient developed recurrent AMI and 8 patients developed recurrent angina after MI associated with ST-segment depression at 60 +/- 42 hours after the dipyridamole-thallium-201 imaging; of these, 6 required urgent coronary revascularization. No patient died in-hospital. There were no serious adverse effects during the dipyridamole protocol. Using stepwise multivariate logistic regression analysis, the best and only statistically significant predictor of in-hospital ischemic cardiac events was the presence of thallium-201 redistribution within the infarct zone (p = 0.0001). Of 20 patients with infarct zone thallium-201 redistribution, 9 (45%) developed in-hospital ischemic cardiac events compared to 0 of 30 patients without infarct zone thallium-201 redistribution (p less than 0.0001). During a follow-up 12 +/- 7 months after discharge, 3 additional patients with infarct zone thallium-201 redistribution developed recurrent AMI or unstable angina, whereas no patient without infarct zone thallium-201 redistribution developed ischemic cardiac events. These data suggest that dipyridamole-thallium-201 imaging performed very early after AMI may identify a subgroup of patients at high risk for in-hospital and late ischemic cardiac events. Such patients may benefit from early cardiac catheterization and revascularization. Patients without infarct zone thallium-201 redistribution appear to be at very low risk for in-hospital and late ischemic cardiac events and may be candidates for early discharge.     

Prognostic value of exercise thallium-201 imaging in patients presenting for evaluation of chest pain

Accurate prognostic information is important in determining optimal management of patients presenting for evaluation of chest pain. In this study, the ability of exercise thallium-201 myocardial imaging to predict future cardiac events (cardiovascular death or nonfatal myocardial infarction) was correlated with clinical, coronary and left ventricular angiographic and exercise electrocardiographic data in 139 consecutive, nonsurgically managed patients followed-up over a 3 to 5 year period (mean follow-up, 3.7 ± 0.9), using a logistic regression analysis. Among patients without prior myocardial infarction (100 of 139), the number of myocardial segments with transient thallium-201 defects was the only statistically significant predictor of future cardiac events when all patient variables were evaluated. Among patients with myocardial infarction before evaluation (39 of 139), angiographic ejection fraction was the only significant predictor of future cardiac events when all variables were considered. This study suggests an approach to evaluate the risk of future cardiac events in patients with possible ischemic heart disease.     

Additional prognostic value of exercise testing and thallium-201 scintigraphy in catheterized patients without previous myocardial infarction

To determine whether exercise testing and thallium scintigraphy provide additional prognostic information in symptomatic patients undergoing catheterization, we studied 432 consecutive male patients without a previous myocardial infarction by means of an exercise test, thallium scintigraphy and catheterization. The follow-up period was 46 +/- 24 months (from 12 to 96). Events were defined as death (27 patients), nonfatal myocardial infarction (occurring in 27 patients) or late (greater than 60 days after test) surgery or dilatation (needed in 45 patients). The 5 year survival rate was 89% and the event-free rate was 72%. History, noninvasive and invasive variables were submitted to a stepwise Cox regression analysis. By multivariate analysis, the significant variables related to death were the number of diseased vessels and exercise workload; the selected variables for all cardiac events were the number of diseased vessels; the score at thallium exercise testing and exercise workload. Among the subgroups of 337 coronary patients, the predictive variables for death were exercise workload and the number of diseased vessels. For all cardiac events, the selected variables were the number of diseased vessels, the score of defects during thallium exercise and exercise workload. Thus, in patients without a previous myocardial infarction, noninvasive variables do provide prognostic information which is not available either from the history or from catheterization.     

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

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

Use of exercise thallium-201 imaging for risk stratification of elderly patients with coronary artery disease

Although coronary artery disease (CAD) may be asymptomatic, it is the most common cause of death in elderly patients in the U.S. This study examined the prognosis of 449 patients with a mean age of 65 years using exercise thallium-201 imaging. At a follow-up of 25 months, 45 patients underwent coronary artery revascularization, 8 died of cardiac causes and 10 had nonfatal acute myocardial infarctions (AMIs). Thus the total of patients with "hard" events was 18. The events included 12 of 276 patients with atypical or non-anginal symptoms versus 6 of 128 with typical angina (p = not significant); 7 of 51 patients (14%) with Q-wave AMI versus 11 of 353 (3%) without Q-wave AMI (p less than 0.001); 1 of 183 patients (1%) with normal versus 17 of 221 (8%) with abnormal exercise thallium-201 images (p less than 0.002); 10 of 76 patients (13%) with multi vessel thallium-201 abnormality vs 8 of 328 (2%) with no or 1-vessel thallium-201 abnormality (p less than 0.001) and 10 of 96 patients (10%) with greater than or equal to 3 abnormal segments by thallium-201 imaging (total segments = 9) versus 8 of 308 patients with no or less than 3 abnormal segments (p less than 0.001). The number of segments with thallium-201 defects was 1 +/- 2 patients without and 3 +/- 2 in patients with hard events (p less than 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)     

Prognostic significance of exercise thallium-201 testing in patients aged greater than or equal to 70 years with known or suspected coronary artery disease.

The prognostic value of exercise thallium-201 myocardial perfusion imaging has not been studied in an elderly (aged greater than or equal to 70 years) population. Retrospective analysis of 120 consecutive elderly patients undergoing Bruce protocol exercise stress with quantitative planar thallium-201 scintigraphy, followed clinically for a mean of 36 +/- 12 months after testing, revealed a 10% cardiac event rate (6 cardiac deaths from arrhythmia or congestive heart failure, and 5 fatal and 1 nonfatal myocardial infarction). There were no exercise stress-related complications. Survival without cardiac events was associated with greater exercise duration (5.6 +/- 2.4 vs 3.1 +/- 2.4 minutes; p less than 0.0007) and peak exercise heart rate (131 +/- 18 vs 120 +/- 19 beats/min; p less than 0.05). Univariate variables associated with higher cardiac event rates included: (1) peak exercise less than or equal to stage I (18 vs 6%; p = 0.04); (2) maximal ST-segment depression greater than or equal to 2 mm (27 vs 6%; p = 0.003); and (3) presence of a fixed or reversible thallium-201 perfusion defect (18 vs 2%; p = 0.004). Multivariate stepwise logistic regression analysis identified the combination of peak exercise less than or equal to stage I and any thallium-201 perfusion defect as the most powerful predictor of subsequent cardiac events (relative risk = 5.3 at 1 year). Thus, exercise thallium-201 scintigraphy in elderly patients is safe and provides important prognostic information.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prediction of cardiac events in patients with transient left ventricle dilation on stress myocardial perfusion SPECT images.

BACKGROUND: The purpose of this study was to investigate cardiac events in patients with transient left ventricle (LV) dilation on stress myocardial perfusion single-photon emission computed tomography images (MPI). METHODS AND RESULTS: Consecutive patients (n=53, 31 males, mean age 71 years) with transient LV dilation on thallium-201 stress MPI (treadmill: 21, pharmacologic: 32) were followed for 17 months. Follow-up time was censored at the occurrence of cardiac death, congestive heart failure, acute coronary syndrome, or revascularization. Images were scored and then the summed stress score (SSS), summed rest score, and summed difference score were calculated. Cardiac death occurred in 3 patients, hospitalization occurred in 8 patients, and revascularization occurred in 20 patients. The combined cardiac event rate was 59% (76% for exercise stress vs 47% for pharmacologic stress, p=0.034). Cox regression analysis demonstrated that a combination of higher SSS and slow washout rate was the best predictor of cardiac events (hazard ratio =3.3, p=0.029). CONCLUSIONS: A high cardiac event rate is associated with transient LV dilation on thallium-201 stress MPI. The event rate is particularly high for exercise stress MPI. Furthermore, a combination of the SSS and thallium-201 slow washout is the best predictor of cardiac events in patients with transient LV dilation.     

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.     

Prognostic value of thallium-201 exercise scintigraphy in low-risk patients after Q-wave myocardial infarction: comparison with exercise testing and catheterization.

In a prospective study of 100 consecutive patients discharged after a Q-wave myocardial infarction, the value of reversible ischemia on thallium-201 scintigraphy to assess the risk of cardiac events (death or reinfarction) during 4 years was compared with variables from exercise testing and cardiac catheterization. Patients with markedly impaired left ventricular function [ejection fraction (EF) < or = 0.30] were excluded. During follow-up there were 20 cardiac events (10 cardiac deaths and 10 reinfarctions). Thallium-201 scintigraphy was significantly better than all exercise test variables and better than an EF < 0.40, with good sensitivity and specificity (75 and 51%, respectively). Exercise-induced reversible ischemia on scintigraphy yielded the same information as the presence of multivessel disease. Exercise test variables were of limited value to assess prognosis. Thus, thallium-201 scintigraphy can be used as the only tool to predict future cardiac events in low-risk patients after a Q-wave myocardial infarction.     

Prognostic value of exercise thallium scintigraphy in patients with good exercise tolerance and a normal or abnormal exercise electrocardiogram and suspected or confirmed coronary artery disease.

Exercise thallium scintigraphy is widely used to assess prognosis in patients with suspected or proven coronary artery disease. The incremental prognostic value of this technique in patients who have good exercise tolerance has not been well studied. Two hundred ninety-nine patients with known or suspected coronary artery disease without prior myocardial infarction or revascularization procedure referred for exercise myocardial perfusion imaging and able to exercise to greater than or equal to stage III of the Bruce protocol were included. After a mean follow-up of 50 +/- 10 months, there were 15 cardiac events (5%). The incidence of cardiac events was 10 versus 3% (p less than 0.001) in patients with an abnormal versus normal thallium-201 scan, and 9 versus 3% (p = 0.03) for an abnormal versus normal exercise electrocardiogram. When the 185 patients with a normal exercise electrocardiogram were examined, the incidence of cardiac events was 3% (5 of 150) in patients with a normal scan versus 0% (0 of 35) in patients with an abnormal scan. In the 114 patients with an abnormal exercise electrocardiogram, an abnormal thallium-201 scan was predictive of cardiac events (18% [8 of 44] versus 3% [2 of 70]; p = 0.006). Stepwise logistic regression analysis selected an abnormal thallium-201 scan and abnormal exercise electrocardiogram, low peak exercise heart rate, and male gender as independent variables associated with a significant increased risk of cardiac events. Thus, in patients with known or suspected coronary artery disease and good exercise tolerance, the addition of thallium-201 imaging in patients with an abnormal exercise electrocardiogram provides useful prognostic information.(ABSTRACT TRUNCATED AT 250 WORDS)     

Increased lung uptake of thallium-201 during exercise myocardial imaging: Clinical,hemodynamic and angiographic implications in patients with coronary artery disease

To determine the clinical significance of increased thallium-201 activity in the lung immediately after exercise stress, the thallium-201 scans in 227 patients undergoing cardiac catheterization were reviewed. Thallium lung activity on the Initial anterior view images were graded qualitatively as follows: 0 (none) in 175 patients (77 percent); 1+ (moderate—increased activity in the lungs but less intense than that in left ventricular myocardium) in 37 patients (16 percent); and 2+ (severe—activity equal to or greater in intensity than left ventricular myocardlal activity) in 15 patients (7 percent). Increased (1+ or 2+) lung activity was related to (1) a greater number of myocardial segmental thallium defects (probability [p] < 0.05); and (2) increased severity and extent of coronary artery disease (p < 0.05). In addition, 2+ lung thallium activity was associated with: (1) a greater prevalence of prior myocardial infarctions (p < 0.01); and (2) a lower angiographic ejection fraction at rest (p < 0.05). To determine the hemodynamic changes associated with increased lung uptake of thallium-201, supine stress thallium imaging was performed during cardiac catheterization in 12 additional patients. Of these, the five patients with increased lung activity on thallium scanning had a mean pulmonary capillary wedge pressure that increased with exercise from 12 ± 1 (mean ± 1 standard deviation) to 24 ± 3 mm Hg (p < 0.05); cardiac index did not increase with stress. In contrast, seven patients without increased lung thallium activity demonstrated an increase in mean cardiac index (p < 0.05) without an associated rise in pulmonary capillary wedge pressure (at rest = 10 ± 3 mm Hg; during stress = 12 ± 2 mm Hg). In conclusion, increased pulmonary uptake during exercise thallium-201 imaging suggests the development of exercise-induced left ventricular dysfunction. Evaluation of lung activity should be added to the routine interpretation of exercise thallium-201 myocardial imaging studies.     

Thallium-201 perfusion imaging with atrial pacing or dipyridamole stress testing for evaluation of cardiac risk prior to nonvascular surgery

Preoperative assessment of cardiac risk using thallium-201 scintigraphy and atrial pacing (n=42) or dipyridamole stress testing (n=35) was performed in 77 patients (mean age 65±7 years), who subsequently underwent elective nonvascular surgery. All patients were at low cardiac risk by clinical criteria; none could perform exercise stress testing due to physical limitations. ST depression consistent with ischemia occurred in 11 patients during atrial pacing and in 1 patient during dipyridamole stress testing (p<0.01). Nine patients had reversible perfusion defects with atrial pacing, and 10 patients with dipyridamole stress testing; fixed defects were present in 15 and 8 patients, respectively. Only one patient (fixed perfusion defect with atrial pacing, left main disease on coronary angiography) underwent preoperative coronary revascularization. Two patients subsequently had postoperative cardiac events. One patient (reversible perfusion defect with dipyridamole stress testing) experienced sudden death after a nonvascular procedure, while a second patient (normal thallium images with dipyridamole testing) had a nonfatal myocardial infarction. In patients having atrial pacing or dipyridamole stress testing, thallium-201 scans that are normal or show only a fixed perfusion defect confirm a low risk of cardiac complications following nonvascular surgery. The presence of a reversible perfusion defect does not preclude a postoperative course free of cardiac complications in patients at low cardiac risk by clinical criteria.     

Prognostic value of dipyridamole thallium-201 imaging in elderly patients.

The prognostic value of intravenous dipyridamole myocardial perfusion imaging has not been studied in a large series of elderly patients. Patients greater than or equal to 70 years of age with known or suspected coronary artery disease were evaluated to determine the predictive value of intravenous dipyridamole thallium-201 imaging for subsequent cardiac death or nonfatal myocardial infarction. Of the 348 patients, 207 were symptomatic and 141 were asymptomatic; 52% of the asymptomatic group had documented coronary artery disease. During 23 +/- 15 months of follow-up, there were 52 cardiac deaths, 24 nonfatal myocardial infarctions and 42 revascularization procedures (percutaneous transluminal coronary angioplasty in 20; coronary artery bypass surgery in 22). Clinical univariate predictors of a cardiac event included previous myocardial infarction, congestive heart failure symptoms, hypercholesterolemia and diabetes (all p less than 0.05). The presence of a fixed, reversible or combined thallium-201 defect was significantly associated with the occurrence of cardiac death or myocardial infarction during follow-up (p less than 0.05). Cardiac death or nonfatal myocardial infarction occurred in only 7 (5%) of 150 patients with a normal dipyridamole thallium-201 study (p less than 0.001). Stepwise logistic regression analysis of clinical and radionuclide variables revealed that an abnormal (reversible or fixed) dipyridamole thallium-201 study was the single best predictor of cardiac events (relative risk 7.2, p less than 0.001). As has been demonstrated in younger patients, previous myocardial infarction (relative risk 1.8, p less than 0.001) and symptoms of congestive heart failure at presentation (relative risk 1.6, p = 0.02) were also significant independent clinical predictors of cardiac death or myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Exercise thallium-201 scintigraphy in men with nondiagnostic exercise electrocardiograms. Prognostic implications

We studied the prognostic value of exercise thallium-201 imaging in 196 men with suspected or known coronary artery disease who had nondiagnostic exercise electrocardiograms. The perfusion images in each of three projections were divided into three segments; each segment was assessed for perfusion defects (fixed or reversible). There were 12 cardiac events at a mean follow-up of 15 months (range, one to 66 months). Of those, five patients died of cardiac causes and seven had nonfatal acute myocardial infarctions (MIs). Only the number of perfusion defects significantly predicted cardiac events; clinical presentation, history of MI, presence of Q-wave MI, exercise duration, and exercise heart rate and double product did not predict cardiac events or add to information provided by the number of defects. Furthermore, actuarial life-table analysis showed that patients with three or more perfusion defects had significantly worse prognoses than patients with fewer than three defects. Exercise thallium-201 imaging helps in risk stratification of men with nondiagnostic exercise electrocardiograms.     

Poststress redistribution of thallium-201 in patients with coronary artery disease, with and without prior myocardial infarction

To elucidate patterns of thallium-201 redistribution with and without myocardial infarction, to determine the value of thallium-201 redistribution scintigrams in identifying additional ischemic myocardium in the presence of prior myocardial infarction and to delineate the relation of collateral vessels to redistribution, thallium-201 myocardial perfusion scintigraphy was performed immediately after exercise and 4 to 6 hours after exercise in 46 patients with coronary artery disease and 12 normal control subjects. Scintigrams were interpreted in the conventional visual manner as well as with use of computer-processed myocardial perfusion ratios. Normal control subjects demonstrated uniform thallium-201 distribution with regional perfusion ratios approximating unity in both the early and delayed scintigrams.

Of 27 patients with prior myocardial infarction, 5 (19 percent) had complete redistribution on delayed imaging, 17 (62 percent) had partial redistribution and 5 (19 percent) had no redistribution. Of 25 regions corresponding to electrocardiographlc evidence of infarction, 8 (32 percent) had total, 8 (32 percent) had partial and 9 (36 percent) had no redistribution. Collateral vessels were absent or of poor quality in seven of eight infarct areas with no redistribution; three of four infarct regions with normal early thallium uptake were supplied by collateral vessels of good quality. Of 12 regions supplied with good collateral vessels, 9 had complete redistribution, 2 partial and 1 no redistribution. In contrast, only 2 of 21 hypoperfused zones without redistribution (10 percent) were supplied by good collateral vessels. Of 19 patients without prior myocardial infarction, 10 (53 percent) had complete redistribution, 6 (31 percent) had partial redistribution and 3 (16 percent) had no redistribution. Of the 34 abnormal areas in the immediate postexercise image, 22 (65 percent) showed total redistribution, 3 (9 percent) showed partial redistribution and 9 (26 percent) showed no redistribution.

Thus, considerable overlap in redistribution scintigrams occurs in patients with coronary artery disesase with and without prior infarction; a high incidence rate of transient stress-induced hypoperfusion occurs in both infarcted and noninfarcted myocardium. Further, good quality collateral vessels afford redistribution, even to some areas of prior infarction. These data indicate that because delayed postexercise redistribution imaging may not discriminate between myocardial scar and ischemia resting scintigrams may be needed in a substantial number of patients.