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.     

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.     

Prevalence and correlates of increased lung/heart ratio of thallium-201 during dipyridamole stress imaging for suspected coronary artery disease

There is little information concerning the prevalence and clinical correlates of increased pulmonary thallium-201 uptake during dipyridamole thallium-201 stress imaging. Accordingly, the clinical characteristics and quantitative thallium-201 findings were correlated with quantitative lung/heart thallium-201 ratio in 87 patients undergoing dipyridamole thallium-201 stress testing. Nineteen patients (22%) had an elevated ratio (greater than 0.51). These patients were more likely to have had an infarction, to be taking beta blockers, and have a lower rate-pressure product after dipyridamole administration than those with a normal ratio (p less than 0.03). An elevated ratio was associated with a greater likelihood of initial, redistribution and persistent defects, as well as left ventricular cavity dilatation on thallium-201 imaging (p less than 0.05). In addition, the number of myocardial segments demonstrating initial, redistribution and persistent defects was also greater in patients with increased ratios (p less than 0.03). Multivariate analysis demonstrated that the presence of redistribution and left ventricular cavity dilatation were the most significant correlates of lung/heart thallium-201 ratio. It is concluded that the prevalence of increased lung/heart thallium-201 ratio with dipyridamole thallium-201 stress imaging is similar to that seen with exercise stress imaging. As with exercise thallium-201 imaging, increased pulmonary thallium-201 uptake may be a marker of functionally more significant coronary artery disease.     

Electrocardiographically and symptomatically silent myocardial ischemia during exercise testing

Certain patients with coronary artery disease (CAD) may have neither ST depression nor chest pain during exercise despite the presence of myocardial ischemia. The frequency and characteristics of such electrocardiographically and symptomatically silent ischemia were studied in 171 patients with both angiographically documented CAD and scintigraphically documented ischemia. Fifty-six (33%) of 171 patients had neither ST depression nor chest pain (Group N), and 115 (67%) had ST depression and/or chest pain (Group P). The two groups were similar with respect to age, gender, the prevalence of prior infarction, and peak systolic blood pressure. Group N patients, however, had a higher mean peak heart rate and rate-pressure product, less severe scintigraphic ischemia, a lower lung thallium-201 uptake, and a smaller number of diseased vessels. Stepwise discriminant analysis showed a history of effort angina, lung thallium-201 uptake, and scintigraphic severity of ischemia to be significant discriminators between Groups N and P. In conclusion, electrocardiographically and symptomatically silent ischemia may be common during exercise in patients with CAD, and less severe ischemia may be one of important determinants.     

The effect of beta blockade on single photon emission computed tomographic (SPECT) thallium-201 images in patients with coronary disease

We evaluated the effect of beta blockers on thallium-201 (Tl-201) single photon emission computed tomographic (SPECT) imaging in 12 patients with coronary disease using an automated computer algorithm. Maximal exercise heart rate and blood pressure were reduced and exercise time was increased with beta blockers. Estimated stress defect size decreased from 47 +/- 36.3 gm during placebo treatment to 32 +/- 27.1 gm during beta blocker therapy (-32%; p less than 0.01). The placebo treatment redistribution defect was estimated to be 28 +/- 29.8 gm. It fell to 15 +/- 23.3 gm with beta blockade (-46%; p less than 0.005). All patients had a stress Tl-201 defect during placebo treatment and eight had redistribution defects consistent with residual scar. During beta blocker therapy, 2 of 12 patients had normal stress-redistribution studies and only five patients had redistribution defects. Beta blockade can reduce exercise and redistribution Tl-201 SPECT defect size significantly while simultaneously increasing exercise time and reducing angina. Beta blockers may unmask or may eliminate evidence of redistribution. Tl-201 SPECT imaging may be useful in defining the reduction in ischemia produced by cardiac drugs.     

Silent ischemia: evaluation by exercise and redistribution tomographic thallium-201 myocardial imaging

To compare the amount of myocardium jeopardized during silent ischemia and painful ischemia, 112 consecutive patients undergoing coronary arteriography with ischemia demonstrated by exercise and redistribution tomographic thallium-201 myocardial imaging (SPECT) were divided into two groups: 84 patients without anginal pain (silent ischemia) and 28 with pain (painful ischemia). The SPECT apical, mid and basal ventricular levels of the short-axis view and the apical portion of the long-axis view were divided into 20 segments. The results were 1) 7.4 +/- 4.7 ischemic segments in silent ischemia and 7.6 +/- 3.7 in painful ischemia (p = NS) with 4.7 +/- 3.6 segments in silent ischemia undergoing total redistribution compared with 5.4 +/- 3.4 in painful ischemia (p = NS); 2) no difference in the incidence of single, double or triple vessel disease between silent and painful ischemic groups; 3) similar anatomic distribution of ischemic segments between the two groups; 4) more positive exercise electrocardiographic (ECG) changes in painful ischemia (70%) than in silent ischemia (32%) (p less than 0.001) with equal amounts of ischemia associated with positive and negative exercise ECG findings. Conclusions: 1) Patients with silent and painful ischemia during exercise have similar amounts of ischemic myocardium demonstrated by tomographic thallium-201 imaging and similar extent of angiographically documented coronary artery disease despite the absence of pain and the lower incidence of positive exercise ECG findings in silent ischemia. 2) Positive and negative exercise ECG findings were associated with similar amounts of ischemic myocardium.     

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)     

Comparison of chest pain, electrocardiographic changes and thallium-201 scintigraphy during varying exercise intensities in men with stable angina pectoris

This study was performed to evaluate the presence of angina pectoris, electrocardiographic changes and reversible thallium-201 defects resulting from 2 different levels of exercise in 19 patients with known coronary artery disease and evidence of exercise-induced ischemia. The exercise protocols consisted of a symptom-limited incremental exercise test (Bruce protocol) followed within 3 to 14 days by a submaximal, steady-state exercise test performed at 70% of the maximal heart rate achieved during the Bruce protocol. The presence and time of onset of angina and electrocardiographic changes (greater than or equal to 0.1 mV ST-segment depression) as well as oxygen uptake, exercise duration and pressure-rate product were recorded. Thallium-201 (2.5 to 3.0 mCi) was injected during the last minute of exercise during both protocols, and the images were analyzed using both computer-assisted quantitation and visual interpretations. Incremental exercise resulted in anginal symptoms in 84% of patients, and electrocardiographic changes and reversible thallium-201 defects in all patients. In contrast, submaximal exercise produced anginal symptoms in only 26% (p less than 0.01) and electrocardiographic changes in only 47% (p less than 0.05), but resulted in thallium-201 defects in 89% of patients (p = not significant). The locations of the thallium-201 defects, when present, were not different between the 2 exercise protocols. These findings confirm the sequence of the ischemic cascade using 2 levels of exercise and demonstrate that the cascade theory is applicable during varying ischemic intensities in the same patient.     

Silent ischemia after coronary angioplasty: evaluation of restenosis and extent of ischemia in asymptomatic patients by tomographic thallium-201 exercise imaging and comparison with symptomatic patients

One hundred sixteen patients were evaluated to determine the ability of single photon emission computed tomographic (SPECT) thallium-201 exercise and redistribution imaging to detect silent ischemia secondary to restenosis in asymptomatic patients after single and multiple vessel percutaneous transluminal coronary angioplasty and the findings were compared with SPECT imaging detection of restenosis in symptomatic patients. The value of exercise electrocardiography (ECG) and the amount of ischemic myocardium in symptomatic and asymptomatic patients were determined. Forty-one patients were asymptomatic after angioplasty; 77% of these had chest pain before angioplasty. Seventy-five patients had chest pain after angioplasty; 99% of these had chest pain before angioplasty. Restenosis occurred in 61% of asymptomatic and 59% of symptomatic patients and in 46% of the vessels in both asymptomatic and symptomatic patients. Sensitivity, specificity and accuracy for detection of restenosis by SPECT in individual patients were 96%, 75% and 88% versus 91%, 77% and 85%, respectively, in the asymptomatic versus symptomatic groups (p = NS). Sensitivity, specificity and accuracy for restenosis detection in individual vessels were 90%, 89% and 89% versus 84%, 77% and 84%, respectively, in the asymptomatic and symptomatic groups (p = NS), with similar results for the three major arteries. Sensitivity and accuracy of exercise ECG were significantly less than those of SPECT imaging for the patients with silent (40% and 44%) and symptomatic (59% and 64%) ischemia (p less than 0.001). Restenosis of vessels in the patients with silent and symptomatic ischemia was associated with an equal amount and degree of severity of ischemic myocardium in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of the degree of effort on the sensitivity of the exercise thallium-201 stress test in symptomatic coronary artery disease

The sensitivity of ST-segment depression on the electrocardiogram during exercise is influenced by the level of effort. Whether such is the case with thallium-201 imaging (initial defect or redistribution) has not been established. Accordingly, the prevalence of these parameters was evaluated in 288 patients (age 59 +/- 10 years, 88% men) with coronary artery disease who underwent both exercise thallium-201 imaging and coronary angiography within 3 months of each other: 159 had a prior myocardial infarction, 72 had 1-vessel, and 216 had multivessel disease. The degree of effort was evaluated by 3 criteria: (1) percentage of maximal predicted heart rate (less than or equal to 65, greater than 65 to 85, greater than 85%); (2) workload during exercise (less than or equal to 4, greater than 4 to 8, greater than 8 METs); and (3) duration of exercise (less than or equal to 3, greater than 3 to 6, greater than 6 minutes). The prevalence of defects on initial images was higher than both redistribution on delayed images and ST-segment depression on the electrocardiogram (p less than 0.01). The overall prevalence of initial defects remained the same for all levels of effort and was not influenced by the presence or absence of a prior infarction. However, it decreased in patients with 1-vessel disease who exercised to higher workloads. The prevalence of redistribution on delayed thallium-201 images was higher than that of ST-segment depression on the electrocardiogram (p less than 0.01), except at higher levels of effort where they were similar.(ABSTRACT TRUNCATED AT 250 WORDS)     

Acute hemodynamic changes during intravenous dipyridamole thallium imaging early after infarction

In order to determine the safety and hemodynamic effects of intravenous dipyridamole infusion for thallium-201 scinitigraphy in patients with acute ischemic syndromes, 10 patients with recent uncomplicated myocardial infarction (7 +/- 2 days pre-test) had central pressures and cardiac output values measured serially in a coronary care unit during and after the administration of dipyridamole (0.56 mg/kg over 4 minutes) and following aminophylline reversal (50 to 150 mg intravenously) of dipyridamole effect. Cardiac medications were not discontinued. Double product did not change significantly (8522 +/- 1811 versus 9044 +/- 1701; p = NS). Serious ischemic events did not occur, although 20% of patients had noncardiac side effects and 30% developed greater than or equal to 1 mm ST segment depression with associated angina in one-third of these cases. The peripheral blood pressure and heart rate response did not predict the occurrence of myocardial ischemia. Dipyridamole significantly reduced systemic vascular resistance (1218 +/- 302 to 739 +/- 166 dyne/sec-1/cm-5; p less than 0.05) and increased cardiac index (3.1 +/- 0.7 to 4.7 +/- 1.0 L/min/m2; p less than 0.05) within approximately 10 minutes, in association with a significant increase in pulmonary capillary wedge pressure (13 +/- 5 to 17 +/- 6 mm Hg; p less than 0.05). Three patients developed silent new "V" waves in their pulmonary capillary wedge pressure tracing, associated with anterior thallium redistribution. All three patients with newly elevated wedge pressures (greater than 15 mm Hg) had both thallium-201 redistribution and multivessel coronary disease.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prevalence of ischemia by quantitative thallium-201 scintigraphy in patients with ventricular tachycardia or fibrillation inducible by programmed stimulation

The prevalence of exercise-induced ischemia was determined by thallium-201 (TI-201) scintigraphic criteria in patients with ventricular tachycardia (VT) or ventricular fibrillation (VF) inducible by programmed electrical stimulation. Thirty-eight patients (age 57 +/- 19 years), of whom 87% had angiographic coronary artery disease, underwent quantitative TI-201 exercise scintigraphy within 14 days of invasive electrophysiologic testing. The mean rest ejection fraction was 38 +/- 9%. Eighty percent of patients had 1 or more regions with akinetic or dyskinetic wall motion. Thallium-201 scan segments were scored as normal or containing redistribution defects or mild or severe persistent defects. Only 4 patients (10%) had only redistribution defects and 9 (24%) had both redistribution defects and persistent defects; 32 of 38 patients (84%) had 1 or more persistent defects, of which 26 had at least 1 severe, persistent defect (more than 50% reduction in TI-201 activity). Patients with and without exercise-induced VT had a similar prevalence of redistribution. Redistribution defect prevalence was similar in patients with polymorphic VT (3 of 13) and monomorphic VT (10 of 25) during programmed electrical stimulation (difference not significant). Thus, patients with VT or VF induced by programmed ventricular stimulation have extensive TI-201 scintigraphic abnormalities on exercise scintigrams, predominantly those suggesting scar, with associated severe regional wall motion abnormalities at rest. The scintigraphic prevalence of exercise-induced ischemia is low and TI-201 redistribution and exercise ST depression are observed with equal frequency in patients with and those without VT induced during exercise.     

Exercise-induced ST segment elevation 2 weeks after uncomplicated myocardial infarction: contributing factors and prognostic significance

To define the prevalence and clinical significance of exercise-induced ST segment elevation during predischarge treadmill testing after uncomplicated acute myocardial infarction confirmed by serum MB creatine kinase (CK) activity, 241 consecutive patients were prospectively investigated with quantitative exercise thallium-201 scintigraphy, rest radionuclide ventriculography and coronary angiography at 10 +/- 3 days. All patients received customary care, and in none was thrombolytic therapy or emergency coronary angioplasty employed. Eighty-two patients (34%) had exercise-induced ST segment elevation of greater than or equal to 1 mm above rest baseline. These patients were similar to the 159 patients without this finding with respect to history of prior infarction, the Norris coronary prognostic index, exercise duration, metabolic equivalents (METs) achieved and peak heart rate-blood pressure product. The frequency of inducible myocardial ischemia and extent of angiographic coronary disease was also comparable in the two groups. Findings associated with larger infarct size and transmural extent of infarction were more common in patients with exercise-induced ST segment elevation than in those without, including higher peak CK values (1,235 +/- 1,037 versus 942 +/- 915 mumol/min per liter, p less than 0.026), lower left ventricular ejection fraction (43 +/- 12 versus 51 +/- 10%, p less than 0.001), a higher prevalence of pathologic Q waves in greater than or equal to 2 contiguous infarct-related leads (80 versus 55%, p less than 0.001), more persistent thallium-201 defects (2.2 +/- 1.1 versus 1.4 +/- 1.1, p less than 0.001), abnormally increased lung uptake of thallium (33 versus 18%, p less than 0.01) and a greater number of akinetic or dyskinetic segments (3.2 +/- 2.5 versus 1.4 +/- 1.9, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Exercise-induced thallium-201 myocardial perfusion defects in angina pectoris without significant coronary artery stenosis

We performed exercise thallium-201 myocardial scintigraphy in 32 patients with angina pectoris to study the incidence of perfusion defects, who had no significant organic stenosis on coronary angiography. None of them had myocardial infarction or cardiomyopathy. Thallium-201 myocardial scintigraphy and 12-lead ECG recording were performed during supine bicycle ergometer exercise. Perfusion defects in thallium-201 scintigrams in SPECT images were assessed during visual analysis by two observers. In the coronary angiograms obtained during intravenous infusion of nitroglycerin, the luminal diameter of 75% stenosis or less in the AHA classification was regarded as an insignificant organic stenosis. Myocardial perfusion defects in the thallium-201 scintigrams were detected in eight (25%) of the 32 patients. Six of these eight patients had variant angina documented during spontaneous attacks with ST elevations in standard 12-lead ECGs. Perfusion defects were demonstrated at the inferior or inferoposterior regions in six patients, one of whom had concomitant anteroseptal defect. The defects were not always accompanied by chest pain. All but one patient demonstrating inferior or inferoposterior defects showed ST depression in leads II, III and aVF on their ECGs, corresponding to inferior wall ischemia. The exception was a case with right bundle branch block. Thus, 25% of the patients with angina pectoris, who had no evidence of significant organic stenosis on their coronary angiograms, exhibited exercise-induced perfusion defects in their thallium-201 scintigrams. Coronary spasms might have caused myocardial ischemia in these patients.     

Effect of nitroglycerin on coronary collateral function during exercise evaluated by quantitative analysis of thallium-201 single photon emission computed tomography

A noninfarcted, entirely collateral-dependent myocardial region provides an opportunity to assess the effect of nitroglycerin on coronary collateral function during exercise. Stress thallium-201 computed tomography was performed in seven patients with effort angina and no history of myocardial infarction, both before and after nitroglycerin (0.3 mg). All patients had single-vessel disease with total or subtotal (99% with delay) occlusion of proximal left anterior descending coronary artery and well-developed collaterals. The pressure-rate product, mean blood pressure, and heart rate at peak exercise did not differ before and after nitroglycerin. The size of the perfusion defect and the severity of ischemia during exercise estimated by quantitative analysis of thallium-201 single photon emission computed tomography were significantly less after nitroglycerin administration (extent score: 23 +/- 17 vs 7 +/- 9, p less than 0.01; severity score: 20 +/- 22 vs 3 +/- 4, p less than 0.05). The pressure-rate products at peak exercise did not differ before and after nitroglycerin, which suggested that the reduction in perfusion defect size was unlikely to be the result of decreased myocardial oxygen consumption. These results suggest that nitroglycerin improved coronary collateral function during exercise and thus prevented exercise-induced myocardial ischemia.     

Improved myocardial ischemia and left ventricular function during exercise after successful percutaneous transluminal coronary angioplasty

Percutaneous transluminal coronary angioplasty (PTCA) was performed in 42 patients with effort angina, 28 (67%) of them underwent successful angioplasty. Treadmill exercise testing, thallium-201 myocardial scintigraphy and radionuclide ventriculography were performed before and after PTCA for evaluation of the improvement of myocardial ischemia and left ventricular function at rest and during exercise. The average exercise duration by treadmill testing in 14 successful cases increased from 14 +/- 4 (mean +/- S.D.) to 16 +/- 2 minutes (p less than 0.05). Sixteen of 28 the patients were studied by thallium-201 myocardial scintigraphy. Before PTCA, regions of decreased thallium-201 uptake after exercise were observed in 12 of the 16 patients. After angioplasty, no distinct defects were recognizable in 9 of the 12 patients, and in the remaining three, a significant decrease in defects was recognized. Fifteen of the 28 patients were studied by radionuclide ventriculography. The mean ejection fraction was 61 +/- 5% at rest and 56 +/- 11% during exercise (N.S.) before PTCA. After angioplasty, the ejection fraction was unchanged at rest (61 +/- 5 to 62 +/- 4%), but increased significantly during exercise (62 +/- 4 to 74 +/- 4%, p less than 0.001). In conclusion, left ventricular function was improved by successful PTCA due to improvement of myocardial ischemia. The long term results require further study.     

Altered myocardial perfusion in patients with angina pectoris or silent ischemia during exercise as assessed by quantitative thallium-201 single-photon emission computed tomography

The extent of abnormally perfused myocardium was compared in patients with and without chest pain during treadmill exercise from a large, relatively low-risk consecutive patient population (n = 356) referred for quantitative thallium-201 single-photon emission computed tomography (SPECT). All patients had concurrent coronary angiography. Patients were excluded if they had prior coronary angioplasty or bypass surgery. Tomographic images were assessed visually and from computer-generated polar maps. Chest pain during exercise was as frequent in patients with normal coronary arteries (12%) as in those with significant (greater than 50% stenosis) coronary artery disease (CAD) (14%). In the 219 patients with significant CAD, silent ischemia was fivefold more common than symptomatic ischemia (83% versus 17%, p = 0.0001). However, there were no differences in the extent, severity, or distribution of coronary stenoses in patients with silent or symptomatic ischemia. Our major observation was that the extent of quantified SPECT perfusion defects was nearly identical in patients with (20.9 +/- 15.9%) and without (20.5 +/- 15.6%) exertional chest pain. The sensitivity for detecting the presence of CAD was significantly improved with quantitative SPECT compared with stress electrocardiography (87% versus 65%, p = 0.0001). Although scintigraphic and electrocardiographic evidence of exercise-induced ischemia were comparable in patients with chest pain (67% versus 73%, respectively; p = NS), SPECT was superior to stress electrocardiography for detecting silent myocardial ischemia (52% versus 35%, respectively; p = 0.01). The majority of patients in this study with CAD who developed ischemia during exercise testing were asymptomatic, although they exhibited an angiographic profile and extent of abnormally perfused myocardium similar to those of patients with symptomatic ischemia. The prognostic significance of quantified perfusion defects detected by SPECT remains to be assessed.     

The clinical significance of exercise-induced ST segment changes in patients with previous inferior myocardial infarction

To investigate the clinical significance of exercise-induced ST changes, we performed exercise body surface mapping (87 leads) in 52 patients (one-vessel disease [1 VD] n = 12, multivessel disease [MVD] n = 40) with previous inferior myocardial infarction (MI). ST isointegral maps were constructed and the locations of ST changes were compared with the findings of exercise thallium-201 (TI-201) myocardial scanning. Exercise-induced ST elevation was observed in 14 patients (27%) on the lower chest and on the back, corresponding to the infarcted area. Exercise-induced ST depression was observed more frequently in the MVD group (n = 30, 75%) than in the 1VD group (n = 2, 17%). Seventeen (77%) of 22 patients with ST depression had thallium-201 redistribution. There was a significant association between ST depression and TI-201 redistribution (chi2 = 13.1, p less than 0.001), but no association between ST depression and ST elevation. The body surface distribution of ST depression was shifted upward and rightward compared with its appearance in angina pectoris without MI. These findings suggest that exercise-induced ST depression reflects myocardial ischemia in patients with previous inferior MI.     

Effect of exercise level on the ability of thallium-201 tomographic imaging in detecting coronary artery disease: analysis of 461 patients

This study examined the effect of the level of exercise on the ability of thallium-201 imaging with single photon emission computed tomography (SPECT) to detect coronary artery disease. Patients in group 1 (n = 164) achieved adequate exercise end points, defined as positive exercise electrocardiograms or greater than or equal to 85% of maximal predicted heart rate. Patients in group 2 (n = 108) had submaximal exercise. The SPECT thallium-201 images showed perfusion defects in 74%, 88%, and 98%, respectively, of patients with one, two and three vessel coronary artery disease in group 1, compared with 52%, 84% and 79%, respectively, of such patients in group 2 (p less than 0.05). Perfusion defects showed partial or complete redistribution consistent with ischemia in 56%, 80% and 88%, respectively, of patients with one, two and three vessel coronary artery disease in group 1 compared with 35%, 58% and 56%, respectively, of such patients in group 2 (p = 0.08, less than 0.03 and less than 0.001, respectively). Of 58 patients with normal coronary angiograms or less than 50% diameter stenosis, 36 (62%) had normal SPECT images. In a separate group of 131 patients with less than 5% pretest probability of coronary artery disease, the specificity was 93%. The sensitivity of exercise SPECT imaging in group 1 was higher than that of ST segment depression (p less than 0.001). Thus, the level of exercise affects the results of SPECT thallium imaging in the localization and evaluation of the extent of coronary artery disease and the detection of ischemia.     

Clinical and prognostic significance of lung thallium uptake on rest imaging in acute myocardial infarction

Exercise-induced pulmonary uptake of thallium-201 in patients with ischemic heart disease is probably due to transient pulmonary edema and left ventricular failure induced by exercise. The significance of increased lung uptake of thallium-201 at rest after acute myocardial infarction (AMI) has not been described. Ninety-six patients admitted with chest pain for suspected AMI or unstable angina underwent thallium-201 imaging at rest. Using conventional diagnostic criteria, 62 had AMI, 12 had unstable angina and 22 had neither. Increased lung uptake of thallium-201 was present in 24 of the total 96 (25%) patients, 20 of the 62 (32%) patients with AMI and 4 of 34 (13%) patients with no evidence of infarction. In the AMI group, those with increased lung thallium-201 uptake had a higher mean +/- standard deviation segmental thallium-201 defect score (22 +/- 7 vs 12 +/- 8, p less than 0.0001), lower ejection fraction (35 +/- 14 vs 49 +/- 14%, p less than 0.002), higher peak creatine kinase levels (2,410 +/- 1,247 vs 1,496 +/- 1,228 IU/liter, p less than 0.01), higher wall motion abnormality score (25 +/- 13 vs 13 +/- 12, p less than 0.0001), increased incidence of clinical in-hospital heart failure (15 of 20 vs 7 of 42, p less than 0.0001) and higher short-term mortality (4 of 20 vs 1 of 42, p less than 0.02) compared to those without increased lung thallium-201 uptake.(ABSTRACT TRUNCATED AT 250 WORDS)