Single dose myocardial perfusion imaging with thallium-201: application in patients with nondiagnostic electrocardiographic stress tests.

The rote of the single dose technique of myocardial perfusion imaging with thallium-201 in evaluating patients with suspected coronary artery disease was studied in 128 patients undergoing diagnostic coronary arteriography. Significant coronary disease (70 percent or more luminal stenosis) was present in 95 patients. Exercise scans were compared with 4 hour redistribution scans for the presence of new defects with exercise. Myocardial perfusion imaging was significantly more sensitive (85 versus 64 percent, P < 0.01) and more accurate (84 versus 71 percent, P < 0.05) than stress electrocardiography in detecting coronary disease.The patients were classified into two groups: group I,89 patients with diagnostically adequate stress electrocardiograms (that is, positive for ischemia or negative at 85 percent or more predicted maximal heart rate), and group II, 39 patients with nondiagnostic stress electrocardiograms (that is, uninterpretable because of intraventricular conduction disturbance or inadequate because of absence of ischemic S-T depression but failure to achieve 85 percent of predicted maximal heart rate). The sensitivity (87 percent), specificity (85 percent) and accuracy (87 percent) of myocardial perfusion imaging in detecting coronary disease in group I were not significantly different from the results of stress electrocardiography alone (88 percent sensitivity, 85 percent specificity and 88 percent accuracy). in group II scintigraphy was 81 percent sensitive, 69 percent specific and 77 percent accurate in detecting coronary disease; these results were not significantly different from those in group I.These data indicate that myocardial perfusion imaging with thallium-201 is more sensitive and more accurate than stress electrocardiography in detecting coronary artery disease but offers no advantage for this purpose in patients with diagnostically adequate stress electrocardiograms.     

Merits of stress thallium-201 myocardial perfusion imaging in patients with inconclusive exercise electrocardiograms: Correlation with coronary arteriograms

Stress thallium-201 myocardial perfusion images were obtained in 65 patients with an inconclusive exercise electrocardiogram. All 65 patients underwent coronary angiographic studies. The exercise electrocardiogram was judged inconclusive in 35 patients (54 percent) because submaximal exercise had been performed and in 30 patients (46 percent) who manifested ST-T segment abnormalities at rest. Exercise thallium-201 myocardial perfusion images were abnormal in 20 patients and normal in 45. Nineteen (95 percent) of the 20 patients with abnormal exercise images had severe disease of one or more major coronary arteries. Thirty-seven (82 percent) of the 45 patients with normal exercise images had no significant coronary artery disease; the remaining 8 patients had coronary artery disease. Therefore, 19 of 27 patients with coronary artery disease had abnormal exercise images (sensitivity 70 percent), and 37 of 38 patients without coronary artery disease had normal exercise images (specificity 97 percent). Thallium-201 imaging predicted the correct diagnosis in 56 patients (86 percent). Thus, exercise myocardial imaging with thallium-201 appears to be a useful diagnostic aid in patients with an inconclusive exercise electrocardiogram.     

Spectrum of exercise thallium-201 myocardial perfusion imaging in patients with chest pain and normal coronary angiograms.

Twenty-seven consecutive patients with chest pain and no significant obstructive coronary lesions on arteriography were studied with thallium-201 myocardial imaging during exercise and at rest. Fifteen of the patients had typical and 12 atypical angina pectoris. All underwent treadmill exercise electrocardiographic testing; the results were abnormal in 10 patients (37 percent), normal in 14 (52 percent) and uninterpretable in 3 (11 percent). The exercise and resting thallium-201 myocardial images were normal in 23 patients (85 percent); the results of exercise testing were normal in 12 of these patients, abnormal in 8 and uninterpretable in 3. Four patients had a perfusion defect on exercise thallium-201 myocardial imaging; the defect filled in by 4 hours in two patients but persisted in the other two. In contrast, when thallium-201 myocardial imaging was performed in 28 consecutive patients with angiographic coronary artery disease, only 5 patients (16 percent) had normal exercise and resting thallium-201 myocardial images. Therefore, thallium-201 myocardial imaging offers a more effective means of identifying patients with chest pain and no obstructive coronary artery disease than the clinical history or the exercise electrocardiographic test, or both. However, 15 percent of these patients will have abnormal exercise thallium-201 myocardial images because of factors that have not yet been identified.     

Adenosine Thallium-201 Tomography in Evaluation of Graft Patency Late After Coronary Artery Bypass Graft Surgery

Objectives. We sought to ascertain the utility of adenosine thallium-201 tomography for assessing graft stenoses late after coronary artery bypass graft surgery.Background. Although pharmacologic perfusion imaging has been increasingly used in the assessment of patients with coronary artery disease, the value of this stress modality for detecting coronary artery bypass graft stenosis late after surgery is unknown.Methods. We studied 109 patients who underwent both adenosine thallium-201 tomography and coronary angiography at 6.7 ± 4.8 (mean ± SD) years after coronary artery bypass graft surgery. Adenosine thallium-201 tomography was assessed quantitatively by computer-generated polar maps of the myocardial thallium-201 activity.Results. On coronary angiography, significant graft stenoses were present in 68 patients, 65 of whom had a corresponding perfusion defect as shown by thallium-201 tomography (sensitivity 96%). Significant stenoses were present in 107 (37.8%) of 283 grafts. The overall specificity by quantitative tomography was 61%. Seventy percent of the apparently false positive perfusion defects could be explained on the basis of unbypassed native disease or by the presence of fixed defects in patients with previous myocardial infarction.Conclusions. Thus, results of adenosine thallium-201 tomography are nearly always abnormal in patients with late coronary graft stenosis. Most of the false positive defects appear to be due to either unbypassed native disease or a previous myocardial infarction.(J Am Coll Cardiol 1997;29:1290–5)     

Thallium-201 myocardial perfusion imaging in aortic valve stenosis

The clinical utility of thallium-201 myocardial perfusion imaging in aortic valve stenosis was evaluated at rest and after exercise in three groups of patients: (1) 20 normal subjects, (2) 11 patients with aortic valve stenosis and coronary artery disease (70 percent or greater narrowing of luminal diameter), 11 patients with aortic valve stenosis without coronary artery disease (30 percent or less narrowing). Seven of the latter 22 patients also had postoperative imaging studies. None of the normal subjects had perfusion abnormalities either at rest or after maximal exercise. Three patients with aortic stenosis and coronary artery disease and one with aortic stenosis alone had focal perfusion defects present at rest suggesting prior myocardial infarction. Five patients with aortic stenosis and coronary artery disease manifested new focal perfusion defects and also a pattern of widespread left ventricular wall “thinning” in the postexercise thallium image suggesting diffuse subendocardial ischemia; three had wall “thinning” alone, and two no change in resting focal defects. Five patients with aortic stenosis without coronary artery disease also manifested focal perfusion defects and wall thinning; one had wall thinning alone, and one a new focal defect alone. Two patients had new resting focal defects after surgery, suggesting perioperative damage, and four patients no longer had either the focal or the diffuse pattern of exercise ischemia seen preoperatively.

Thallium-201 imaging is of value in assessing the results of surgery in aortic stenosis. However, the technique does not allow adequate separation of patients with aortic stenosis and coronary artery disease from those with aortic stenosis alone because (1) angiographically significant coronary artery disease may not always produce focal ischemia before diffuse subendocardial ischemia develops, and (2) angiographically insignificant coronary artery disease may become functionally critical in the presence of aortic stenosis and produce focal ischemia.     

Predicting the extent and location of coronary artery disease during the early postinfarction period by quantitative thallium-201 scintigraphy

The ability of quantitative thallium-201 scintigraphy to predict the extent and location of coronary artery disease before hospital discharge after acute myocardial infarction was evaluated in 52 patients. All patients underwent coronary angiography and serial thallium-201 imaging either at rest (10 patients) or after submaximal exercise stress (42 patients; target heart rate 120 beats/min). Two or three vessel disease was designated if abnormal thallium-201 uptake or washout patterns, or both, were seen in two or three vascular segments, respectively. Of 156 vessels analyzed in the 52 patients, 91 stenoses of 70 percent or greater were found by angiography. Seventy-four (81 percent) of these were predicted by scintigraphy. The specificity of scintigraphy for identifying vessel stenoses was 92 percent. Sensitivity for detecting and localizing stenoses supplying an infarct zone was 96 percent compared with 62 percent for stenoses supplying myocardium remote from the acute infarct. Perfusion abnormalities were more frequently seen in the distribution of vessels with severe (90 percent or greater) stenoses than in those with moderate (70 to 90 percent) stenoses (87 versus 53 percent, p <0.01). Scintigraphy detected a greater proportion of left anterior descending and right coronary arterial stenoses than circumflex stenoses (91 and 87 versus 63 percent, respectively, p <0.006).In the 42 patients who underwent submaximal exercise testing, multivariate analysis of 23 clinical and laboratory variables identified multiple thallium-201 defects as the best predictor of multivessel disease. The predictive accuracy of exercise-induced S-T segment depression was only 45 percent compared with 88 percent (p <0.05) for thallium-201 scintigraphy. Thus, 2 weeks after myocardial infarction, exercise thallium-201 scintigraphy is useful for predicting the extent and location of coronary artery disease, particularly stenoses in the left anterior descending and right coronary arteries. Moreover, thallium-201 imaging at rest is reliable in assessing the extent of coronary disease in hospitalized patients who cannot undergo exercise testing because of unstable angina, uncompensated heart failure, poorly controlled arrhythmias or physical limitations.     

Exercise thallium-201 myocardial scintigraphy in women: Correlation with coronary arteriography

Results of exercise thallium-201 myocardial perfusion images, obtained in 60 women suspected of having coronary artery disease, were correlated with coronary angiographic findings. Thirty-two patients had no significant coronary artery disease; 28 patients had severe coronary artery disease defined as 70 percent or greater diameter narrowing of one vessel (14 patients) or multiple vessels (14 patients). The exercise electrocardiogram was positive in 17 patients (9 with and 8 without coronary artery disease), negative in 16 patients (3 with and 13 without coronary artery disease) and inconclusive in 27 patients (16 with and 11 without coronary artery disease). The exercise thallium-201 scintigram showed exercise-induced defects (reversible ischemia) in 21 patients with coronary artery disease, a fixed defect in 1 patient with single vessel disease and previous transmural infarction, but was normal in the remaining 6 patients, who had single vessel disease. The exercise thallium-201 scintigram in subjects with no coronary artery disease was normal in 28, showed an exercise-induced defect in 1 subject and a fixed defect in the remaining 3 subjects. These fixed defects involved the anterolateral segment in the anterior projection and are thought to be due to attenuation of activity by the overlying breasts. Thus, the sensitivity of the exercise electrocardiogram was 32 percent and the specificity 41 percent. In contrast, the sensitivity of exercise thallium-201 scintigraphy was 75 percent and the specificity 97 percent if only exercise-induced defects were considered abnormal and 79 and 88 percent, respectively, if all fixed defects were considered abnormal.It is concluded that exercise thallium scintigraphy is useful in women suspected of having coronary artery disease. Attenuation of activity by breasts may affect the specificity but not the sensitivity. The exercise electrocardiogram is neither sensitive nor specific in this group.     

Idiopathic hypertrophic subaortic stenosis: evaluation of anginal symptoms with thallium-201 myocardial imaging.

The evaluation of angina pectoris in patients with idiopathic hypertrophic subaortic stenosis is difficult in those in the age group prone to coronary artery disease. Ten patients with angina pectoris, normal coronary angiograms and idiopathic hypertrophic subaortic stenosis were studied with thallium-201 myocardial imaging performed in conjunction with submaximal treadmill exercise testing. The resting electrocardiogram demonstrated left ventricular hypertrophy with S-T segment abnormalities in seven patients, thereby vitiating the further increase in S-T segment abnormalities that developed in these patients during exercise or in the postexercise period. Of the three patients with a normal resting electrocardiogram, one had significant exercise-induced S-T segment depression. Thallium-201 myocardial imaging revealed no significant perfusion defects in 9 of the 10 patients (90 percent). In one patient with severe left ventricular hypertrophy significant perfusion defects developed after exercise that were not present at rest. Stress thallium-201 myocardial perfusion imaging is a useful noninvasive technique that assists in ruling out the presence of significant coronary artery disease in patients with idiopathic hypertrophic subaortic stenosis.     

Exercise thallium-201 myocardial imaging in left main coronary artery disease: Sensitive but not specific

To determine the usefulness of thallium-201 scintigraphy for identifying left main coronary artery disease, the results of scintigraphy at rest and during exercise were compared in 24 patients with 50 percent or greater narrowing of the left main coronary artery and 80 patients with 50 percent or greater narrowing of one or more of the major coronary arteries but without left main coronary involvement. By segmental analysis of the scintigrams, perfusion defects were assigned to the left anterior descending, left circumflex or right coronary artery, singly or in combination, and the pattern of simultaneous left anterior descending and circumflex arterial defects was used to identify left main coronary artery disease. Of the 24 patients with left main coronary artery disease, 22 (92 percent) had abnormal exercise scintigrams. Despite this high sensitivity, the pattern of perfusion defects was not specific; the “left main pattern” was found in 3 patients (13 percent) with left main coronary artery disease but also in 3 (33 percent) of 9 patients with combined left anterior descending and left circumflex arterial disease, 4 (19 percent) of 21 patients with three vessel disease and 3 (6 percent) of 50 patients with one or two vessel disease but excluding the group with left anterior descending plus left circumflex arterial disease.The pattern of perfusion defects in the patients with left main coronary artery disease was determined by the location and severity of narrowings in the coronary arteries downstream from the left main arterial lesion. Concomitant lesions in other arteries were found in all patients with left main coronary disease (one vessel in 1 patient, two vessels in 7 patients and three vessels in 16). For this reason, it is unlikely that even with improvements in radiopharmaceutical agents and imaging techniques, myocardial perfusion scintigraphy will be sufficiently specific for definitive identification of left main coronary artery disease.     

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.     

Myocardial perfusion abnormalities in asymptomatic patients with systemic lupus erythematosus

Accelerated coronary artery disease and myocardial infarction in young patients with systemic lupus erythematosus is well documented; however, the prevalence of coronary involvement is unknown. Accordingly, 26 patients with systemic lupus were selected irrespective of previous cardiac history to undergo exercise thallium-201 cardiac scintigraphy. Segmental perfusion abnormalities were present in 10 of the 26 studies (38.5 percent). Five patients had reversible defects suggesting ischemia, four patients had persistent defects consistent with scar, and one patient had both reversible and persistent defects in two areas. There was no correlation between positive thallium results and duration of disease, amount of corticosteroid treatment, major organ system involvement or age. Only a history of pericarditis appeared to be associated with positive thallium-201 results (p less than 0.05). It is concluded that segmental myocardial perfusion abnormalities are common in patients with systemic lupus erythematosus. Whether this reflects large-vessel coronary disease or small-vessel abnormalities remains to be determined.     

Serial Exercise Thallium Myocardial Perfusion Scanning and Exercise Electrocardiography in the Diagnosis of Coronary Artery Disease*

Summary: Serial exercise thallium-201 myocardial perfusion scanning (exercise and 4-hour redistribution) was compared to rest and exercise electrocardiography (ECG) for the detection of coronary artery disease in 125 patients with known or suspected coronary artery disease. All patients underwent coronary arteriography and 108 were found to have significant coronary artery lesions. The serial exercise thallium scan was significantly more sensitive than rest and exercise ECG in detecting coronary artery disease (94% v. 83% P <0.01). The sensitivity of a reversible thallium perfusion scan abnormality and a positive exercise ECG for detecting exercise induced myocardial ischaemia in coronary artery disease was similar (69% v. 63%). The exercise thallium scan complemented the exercise EGG, and the sensitivity of the combined test was significantly greater than the exercise ECG alone (84% v. 63% P<0.001). The specificity for coronary artery disease of the exercise ECG was 65% and that of the exercise thallium-201 myocardial perfusion scan was 82% (P = NS). Thallium-201 myocardial perfusion scanning complements the rest and exercise ECG in the non-invasive detection of coronary artery disease.     

Quantitative thallium-201 single-photon emission computed tomography during maximal pharmacologic coronary vasodilation with adenosine for assessing coronary artery disease

The diagnostic value of maximal pharmacologic coronary vasodilation with intravenously administered adenosine in conjunction with thallium-201 single-photon emission computed tomography (SPECT) for detection of coronary artery disease was investigated in 101 consecutive patients who had concomitant coronary arteriography. Tomographic images were assessed visually and from computer-quantified polar maps of the thallium-201 distribution. Significant coronary artery disease, defined as greater than 50% luminal diameter stenosis, was present in 70 patients. The sensitivity for detecting patients with coronary artery disease using quantitative analysis was 87% in the total group, 82% in patients without myocardial infarction and 96% in those with prior myocardial infarction; the specificity was 90%. The sensitivity for diagnosing coronary artery disease in patients without infarction with single-, double-and triple-vessel disease was 76%, 86% and 90%, respectively. All individual stenoses were identified in 68% of patients with double-vessel disease and in 65% of those with triple-vessel disease. The extent of the perfusion defects, as quantified by polar maps, was directly related to the extent of coronary artery disease. In conclusion, quantitative thallium-201 SPECT during adenosine infusion has high sensitivity and specificity for diagnosing the presence of coronary artery disease, localizing the anatomic site of coronary stenosis and identifying the majority of affected vascular regions in patients with multivessel involvement.     

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.     

Discriminant function analysis using thallium-201 scintiscans and exercise stress test variables to predict the presence and extent of coronary artery disease

The ability to predict the presence and extent (number of affected vessels) of coronary artery disease objectively from an exercise treadmill test and thallium-201 myocardial perfusion scintiscans was evaluated using linear discriminant function analysis. Exercise and redistribution scans in the 30 ° left anterior oblique view were characterized by their two dimensional Fourier transforms. The analysis was performed in 141 persons, including 110 patients with coronary artery disease (70 percent or greater stenosis of luminal diameter) and 31 control subjects. There were 43 patients with single vessel and 67 patients with multivessel disease.

Input to the discriminant analysis included age, sex, 18 variables from the exercise treadmill test and 36 Fourier frequency coefficients from each scan (exercise and redistribution). Two analyses were performed. In the first, a discriminant function was constructed to detect the presence of coronary artery disease. Seven input variables were chosen: maximal exercise pressure-rate product, sex, anginal pain, change in S-T segment slope with exercise, two Fourier coefficients from the exercise scan and one Fourier coefficient from the redistribution scan. The function correctly classified 103 of 110 patients with coronary artery disease and 27 of 31 control subjects; the estimated sensitivity of the technique is 94 percent, with 87 percent specificity and an overall accuracy of 92 percent for the detection of coronary artery disease. The discriminant function was significantly more sensitive and accurate than qualitative scan interpretation (p < 0.05).

In the second analysis, two discriminant functions were developed to predict the extent of disease. In addition to the preceding variables, the duration of exercise, change in systolic blood pressure during the last two stages of exercise, and another Fourier coefficient from the exercise scan were chosen. Using two functions, the method detected the presence of coronary artery disease in 104 of 110 patients (95 percent sensitivity) and correctly classified 28 of 31 control subjects (90 percent specificity). Multivessel disease was correctly predicted in 53 of 67 patients (79 percent accuracy); another 11 patients with multivessel disease were predicted to have single vessel disease. Twenty-nine (67 percent) of 43 patients with single vessel disease were correctly classified; of the remaining 14 patients, 12 were predicted to have multivessel disease and 2 were judged to have normal vessels.

The data demonstrate that numerical functions derived from the exercise treadmill test variables and Fourier coefficients of thallium-201 scans can be used to detect the presence of coronary artery disease with 92 percent accuracy. The predictive accuracy for the number of diseased vessels was 78 percent (110 of 141 patients classified correctly).     

Quantitative thallium-201 single photon emission computed tomography after oral dipyridamole for assessing the presence, anatomic location and severity of coronary artery disease

The objective of this investigation was to determine whether analysis of thallium-201 images as detected by quantitative single photon emission computed tomography after a single high oral dose of dipyridamole (300 mg) would accurately detect the presence of coronary artery disease and the anatomic location of the individual stenosis. Analyses were performed on 100 patients who concomitantly underwent diagnostic coronary arteriography and myocardial imaging. Tomographic myocardial perfusion defects were quantified using computer-generated polar maps. Eighty-four patients had significant coronary artery disease defined as greater than 50% luminal diameter stenosis. The sensitivity for detecting patients with coronary disease was 92% overall, 89% in patients without previous myocardial infarction and 97% in those with prior infarction. The technique had a sensitivity of 80, 87 and 51% for localizing coronary artery stenosis of the left anterior descending, the right coronary and the left circumflex artery, respectively. The corresponding specificity was 84, 92 and 92%. Furthermore, the presence of severe (greater than or equal to 70%) multivessel disease was identified with a sensitivity of 79% and a specificity of 87%. In conclusion, quantitative thallium-201 single photon emission computed tomography after oral dipyridamole has high sensitivity and specificity for diagnosing the presence of coronary disease, ascertaining the location of stenosed vessels and identifying the presence of multivessel disease.     

Clinical assessment of myocardial perfusion with thallium-201

Assessment of myocardial perfusion and coronary blood flow in man can be performed reliably and successfully using thallium-201 imaging. The extent of exercise myocardial perfusion abnormalities reflects the functional significance of coronary artery stenosis. Accordingly, myocardial perfusion imaging is not only useful for the detection of coronary artery disease, but it also provides unique functional information which should be helpful in the management of patients with known coronary artery disease. The unfavorable physical properties of thallium-201 have limited to a certain extent full utilization of the clinical potential of the methodology. Now technetium-99m-labeled myocardial perfusion imaging agents promise to further enhance the clinical usefulness of myocardial perfusion imaging in patients.     

Dipyridamole thallium-201 myocardial scintigraphy in coronary diagnosis; a comparison of methods with thallium-201 myocardial scintigraphy after ergometer stress

Two scintigraphic methods, resting dipyridamole and exercise thallium-201 myocardial perfusion imaging, to detect and localize coronary artery stenosis were compared in 32 patients suffering from coronary artery disease. The sensitivity of detecting a greater than 50% coronary stenosis was 94% for exercise thallium-201 perfusion imaging and 88% for dipyridamole thallium-201 perfusion imaging. The overall sensitivity and specificity of localizing a greater than 50% coronary stenosis by the two methods were also not significantly different. The results of the two scintigraphic methods were independent of the severity of coronary artery disease. Dipyridamole thallium-201 myocardial perfusion imaging provides a useful and safe alternative test for detecting and localizing coronary artery stenosis in patients unable to perform maximal exercise.     

Localization of coronary artery disease with exercise electrocardiography: correlation with thallium-201 myocardial perfusion scanning

In 61 patients with single vessel coronary artery disease (70 percent or greater obstruction of luminal diameter in only one vessel) and no previous myocardial infarction, the sites of ischemic changes on 12 lead exercise electrocardiography and on thallium-201 myocardial perfusion scanning were related to the obstructed coronary artery. The site of exercise-induced S-T segment depression did not identify which coronary artery was obstructed. In the 37 patients with left anterior descending coronary artery disease S-T depression was most often seen in the inferior leads and leads V₄ to V₆, and in the 18 patients with right coronary artery disease and in the 6 patients with left circumflex artery disease S-T depression was most often seen in leads V₅ and V₆. Although S-T segment elevation was uncommon in most leads, it occurred in lead V₁ or aVL, or both, in 51 percent of the patients with left anterior descending coronary artery disease. A reversible anterior defect on exercise thallium scanning correlated with left anterior descending coronary artery disease (probability [p] < 0.0001) and a reversible inferior thallium defect correlated with right coronary or left circumflex artery disease (p < 0.0001).In patients with single vessel disease, the site of S-T segment depression does not identify the obstructed coronary artery; S-T segment elevation in lead V₁ or aVL, or both, identifies left anterior descending coronary artery disease; and the site of reversible perfusion defect on thallium scanning identifies the site of myocardial ischemia and the obstructed coronary artery.     

Thallium-201 myocardial scintigraphy in patients with Wolff-Parkinson-White syndrome

Wolff-Parkinson-White syndrome (WPW) is known to cause abnormal rest electrocardiogram and stress test. Thallium-201 myocardial scintigraphy has been particularly indicated for the noninvasive evaluation of coronary artery disease in these patients. The study group consisted of 11 WPW patients with abnormal ST-segment depression at rest electrocardiogram and/or stress test, with the absence of signs or symptoms of coronary artery disease. All the patients underwent exercise thallium-201 imaging associated with stress test by bicycle ergometer: 7 of them had ST-segment depression, but without other signs or symptoms of coronary artery disease. Transient and moderate myocardial perfusion defects were found in 5 of 11 patients. Perfusion defects in patients with WPW could derive from dyssynergy of ventricular activation, which could modify myocardial perfusion scintigraphy despite the absence of angiographic coronary stenosis. Previous reports and our data concluded that transient perfusion defects during exercise thallium-201 testing in WPW patients without cardiovascular disease may be observed. Thus, thallium-201 myocardial scintigraphy could present some limitations as a helpful adjunctive method for assessment of coronary artery disease in WPW patients.