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.     

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)     

Effect of patient obesity on the accuracy of thallium-201 myocardial perfusion imaging

The effects of patient habitus (e.g., breast attenuation in women and diaphragmatic attenuation in men) have long been recognized as factors that reduce the accuracy of myocardial perfusion imaging. Although it has long been assumed that patient obesity effects accuracy, this has never been formally evaluated. We studied the effects of patient obesity, defined as a body mass index (BMI) > or = 30, on 607 patients who underwent exercise thallium-201 single-photon emission computed tomography (SPECT). Because the effects of obesity are most likely mediated through increased photon attenuation and scatter, we also evaluated the effects of other markers of patient size: body surface area (BSA) and patient weight. Accuracy was determined by performing quantitative analysis and measuring the area under the receiver operating characteristic curve (AUC). Obesity was associated with significantly lower accuracy (AUC 0.86 +/- 0.03 vs 0.92 +/- 0.02, p <0.05) despite similar estimates of maximal coronary blood flow (as estimated by heart rate and rate-pressure product at peak exercise) and severity of coronary disease. There were no significant differences attributable to either patient weight or BSA. Weight and BSA correlated significantly with left ventricular chamber size whereas BMI did not. We conclude that the accuracy of quantitative SPECT thallium-201 is significantly reduced by patient obesity and that although BSA and weight are also associated with increased attenuation, they have no effect on accuracy, which is most likely due to the compensating effects of increased chamber size.     

Spontaneous changes in thallium-201 myocardial perfusion imaging after myocardial infarction

To examine regional myocardial perfusion after myocardial infarction, 26 patients underwent exercise electrocardiographic testing with thallium-201 myocardial perfusion imaging 3 weeks and 3 months after infarction. At 3 weeks, 9 of 26 patients (35%) had myocardial ischemia by exercise electrocardiographic testing, whereas 18 of 26 (69%) had ischemia by thallium-201 imaging. The thallium-201 scintigrams were scored by dividing each image, in 3 views, into 5 segments, using a 5-point scoring scheme. The exercise thallium-201 score was 44.3 ± 1.2 and increased to 47.3 ± 1.2 in the redistribution study (p < 0.001). Three months after infarction, although there was a significantly greater rate-pressure product which would predict a larger ischemic defect and a decrease in the stress thallium-201 score, the stress score was improved (48.3 ± 1.1, p < 0.001). The redistribution score was similar, that is, 48.9 ± 1.0. The improvement in thallium-201 myocardial perfusion was associated with a loss of stress-induced ischemia in 8 patients (30%). These results indicate that spontaneous improvements in thallium-201 myocardial perfusion imaging may occur after myocardial infarction.     

Prognostic value of thallium-201 perfusion defects in idiopathic dilated cardiomyopathy

To assess the prognostic significance of thallium-201 perfusion defects in patients with idiopathic dilated cardiomyopathy (IDC), 43 patients underwent thallium scintigraphy in addition to clinical, echocardiographic, angiographic and hemodynamic evaluation. Eleven patients had no significant thallium perfusion abnormality, 19 had multiple small defects and 13 had a large defect. During 3.2 +/- 2.2 years, 14 patients had disease-related mortality. The patients who died had a higher incidence of ventricular tachycardia (71 vs 31%; p less than 0.02), increased cardiothoracic ratio (60 +/- 6 vs 54 +/- 6; p = 0.005), decreased fractional shortening (11 +/- 6 vs 15 +/- 5; p less than 0.05), increased pulmonary wedge pressure (15 +/- 7 vs 10 +/- 6 mm Hg; p = 0.05), increased left ventricular end-diastolic pressure (21 +/- 8 vs 14 +/- 6 mm Hg; p = 0.02) and abnormal thallium perfusion defects (13 of 14 vs 16 of 26; p less than 0.05) compared with survivors. Age, gender, left ventricular end-systolic and end-diastolic dimensions, cardiac index and ejection fraction were not statistically different in the survivors versus the patients who died. Kaplan-Meier survival estimates at 1, 3 and 5 years were 100% in patients without significant perfusion abnormality; 89, 77 and 64%, respectively, in patients with multiple small defects; and 84, 76 and 30%, respectively, in patients with a large defect (p less than 0.025 by log rank test).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of beta adrenergic blockade on thallium-201 myocardial perfusion imaging.

Nine patients with stable angina (group 1) underwent maximal treadmill stress testing and thallium-201 (201T1) myocardial scintigraphy after intravenous propranolol hydrochloride, and after placebo. Though seven of the nine patients exercised longer after propranolol than after placebo, this difference did not reach statistical significance. Propranolol, however, significantly reduced the mean maximum rate pressure product. Comparison of the perfusion scans on and off propranolol showed that in 36 out of 90 of the myocardial segments recorded (nine patients, five segments scanned twice per patient), only one of the scans showed a defect. In 24 out of 36 of these the propranolol scan was negative, the defect appearing in the placebo scan. Defects present on both scans but differing significantly in size occurred in 22 out of 54 view pairs (nine patients, three views after exercise and three views after redistribution on propranolol and on placebo), and in 19 of these the smaller defect was seen in the propranolol scan. In one of the nine patients, the propranolol scan was normal (false negative), whereas defects corresponding to angiographically proven coronary artery lesions were seen on the placebo scan. Six patients (group 2) were maximally exercised after propranolol and then re-exercised to the same rate pressure product on placebo. Again 16 out of 60 of the segment pairs disagreed and in 10 of these the unmatched defect was present on the placebo scan. In 10 out of 14 discrepant view pairs, the smaller defect occurred on the propranolol scan. Thus in patients taking propranolol, negative results do not exclude coronary artery disease, and perfusion defects (if present) though accurately reflecting the presence of disease may underestimate its true extent.     

Clinical value of delayed thallium-201 myocardial imaging in suspected acute myocardial infarction.

Fifty patients with acute chest pain had thallium-201 myocardial imaging performed three to six days after emergency admission to hospital. The image was abnormal in 20 out of 22 patients with acute transmural myocardial infarcts but in only 1 of 5 with acute subendocardial infarcts. Indistinguishable scan abnormalities caused by old infarcts were seen in 7 patients, and caused by myocardial ischaemia in 1 patient. A single thallium-201 myocardial scan some days after the onset of symptoms appears to be of little value in the clinical assessment of patients with suspected acute myocardial infarction.     

Effect of beta adrenergic blockade on thallium-201 myocardial perfusion imaging

Nine patients with stable angina (group 1) underwent maximal treadmill stress testing and thallium-201 (201T1) myocardial scintigraphy after intravenous propranolol hydrochloride, and after placebo. Though seven of the nine patients exercised longer after propranolol than after placebo, this difference did not reach statistical significance. Propranolol, however, significantly reduced the mean maximum rate pressure product. Comparison of the perfusion scans on and off propranolol showed that in 36 out of 90 of the myocardial segments recorded (nine patients, five segments scanned twice per patient), only one of the scans showed a defect. In 24 out of 36 of these the propranolol scan was negative, the defect appearing in the placebo scan. Defects present on both scans but differing significantly in size occurred in 22 out of 54 view pairs (nine patients, three views after exercise and three views after redistribution on propranolol and on placebo), and in 19 of these the smaller defect was seen in the propranolol scan. In one of the nine patients, the propranolol scan was normal (false negative), whereas defects corresponding to angiographically proven coronary artery lesions were seen on the placebo scan. Six patients (group 2) were maximally exercised after propranolol and then re-exercised to the same rate pressure product on placebo. Again 16 out of 60 of the segment pairs disagreed and in 10 of these the unmatched defect was present on the placebo scan. In 10 out of 14 discrepant view pairs, the smaller defect occurred on the propranolol scan. Thus in patients taking propranolol, negative results do not exclude coronary artery disease, and perfusion defects (if present) though accurately reflecting the presence of disease may underestimate its true extent.     

Evaluation of myocardial infarction by radioisotope myocardial imaging with special reference on thallium-201 myocardial perfusion imaging

One hundred and three patients with myocardial infarctions were studied with 201-thallium chloride and/or 99m-technetium pyrophosphate myocardial imaging and were followed-up for an average of 23 months. There were 24 false negative cases with 201-thallium chloride, but no deaths or serious complications occurred during the follow-up period in these false negative cases. There were six patients with widened QRS complexes (more than 0.12 seconds) without bundle branch blocks and in three of them myocardial infarction was not identified by electrocardiography. However, there were large myocardial perfusion defects in the anterior-inferior wall of the left ventricle. All of this group of patients died suddenly during the follow-up period. The incidence of complications and mortality rose sharply in patients whose myocardial perfusion defects detected by thallium-201 were larger than 40% of the entire left ventricle. The myocardial infarction areas measured by 99m-technetium pyrophosphate were 28.5 +/- 9.8 cm2 in non-survivors and 16.5 +/- 1.7 cm2 in survivors. In addition, ten patients with acute myocardial infarction were studied by double scan methods with thallium-201; myocardial perfusion defect areas were reduced from 29 +/- 3% of the entire left ventricle to 19 +/- 4% by nitrate administration, indicating that there were reversibly ischemic areas in acute myocardial infarction which could be transiently reduced by nitrate. Thus, the study suggests the possibility of decreasing myocardial perfusion defects in the early phase of acute myocardial infarction, leading to a better long term prognosis for the patients.     

Exercise stress myocardial perfusion scintigraphy with thallium-201.

We performed exercise stress scintigraphy with thallium-201 in 88 patients including 31 patients of effort angina and nine patients of old myocardial infarction without angina. Sensitivity of exercise stress scintigraphy to detect effort angina was 77%, whereas sensitivity of exercise stress ECG was only 44.5%. The combination of stress scintigraphy with stress ECG enhanced sensitivity up to 87%. Exercise stress scintigraphy was useful particularly in cases with one vessel disease and those who failed to achieve sufficient exercise stress. Besides exercise stress scintigraphy did not show false positive response, differing from exercise stress ECG. Myocardial imaging is a method which shows the balance between myocardial perfusion demand and supply.     

Prognostic significance of large perfusion defects on thallium-201 myocardial scintigraphy in dilated cardiomyopathy

To evaluate the prognostic significance of perfusion abnormalities, particularly large defects, in dilated cardiomyopathy (DCM), we performed thallium-201 myocardial scintigraphy and 24-hour ambulatory ECG monitoring in 27 patients. The abnormal scintigraphic patterns and the presence of ventricular tachycardia (VT) were correlated with causes of death during a follow-up period of 30.0 +/- 19.4 months. Eight patients had large defects (LD), 11 had multiple small defects (MSD), and eight had no defects (NL). The patients with LD had extensive ventricular akinesis in the region of the perfusion defect, significantly elevated LVEDP (LD 20.6 +/- 7.4 mmHg, MSD 15.5 +/- 7.6 mmHg, NL 10.3 +/- 2.3 mmHg: LD vs NL; p less than 0.01, MSD vs NL; p less than 0.05), and reduced ejection fraction (LD 23.9 +/- 9.1%, MSD 32.7 +/- 7.2%, NL 40.3 +/- 7.7%: LD vs MSD; p less than 0.05, MSD vs NL; p less than 0.01). VT was detected in 11 patients; among whom three had LD, six had MSD, and two had no defects. Among seven patients who died during follow-up (five of heart failure, one sudden death, and one non-cardiac death), five had LD and two had MSD. There were no deaths among patients without defects. Among 11 patients with VT, only one died suddenly. In conclusion, large scintigraphic defects correlated well with severe LV dysfunction, and this is an important variable in predicting outcomes in DCM.     

铊^201单光子发射计算机断层心肌显像对隐匿性冠心病预后判断的价值

目的探讨心肌潘生丁负荷／再分布铊（T1）^201单光子发射计算机断层显像（single photon emission computed tomography，SPECT）法评价隐匿性冠心病预后的可行性。方法入选1998至2005年期间94例无任何症状但运动平板试验反复阳性的飞行人员，根据SPECT心肌显像结果分为检查结果阳性组及阴性组，阳性组中根据心肌缺血累及范围又分为单个节段受累亚组、2个节段受累亚组和2个以上节段受累亚组，平均随访4．5年，比较组间的主要心血管事件（major adverse cardiovascular events，MACE）发生率。结果随访过程中，阳性组与阴性组的MACE分别为30％与7％，差异具有统计学意义（P〈0．01）。2个以上节段受累亚组组MACE发生率（100％）明显高于单个节段受累亚组（24％）、2个节段受累亚组（22％）及阴性组（7％），P均〈0．05。结论潘生丁负荷心肌T1^201-SPECT显像有助于隐匿性冠心病预后判断，从而指导临床早期干预治疗。     

Evaluation of myocardial involvement in Duchenne's progressive muscular dystrophy with thallium-201 myocardial perfusion imaging

Myocardial involvement in progressive muscular dystrophy of the Duchenne type was evaluated in 19 patients using thallium-201 myocardial perfusion imaging. A qualitative analysis was performed from five projection images by three experienced physicians. Distinct perfusion defects were shown in 13 patients, especially in the LV posterolateral or posterior wall (11 patients). There was no significant relationship between the presence of perfusion defects and the skeletal muscle involvements or thoracic deformities assessed by transmission computed tomography. Extensive perfusion defects were shown in 2 patients who died of congestive heart failure 1 to 2 years after the scintigraphic study. Progression of the myocardial scintigraphic abnormalities were considered to be minimal in 7 of 9 patients who underwent two serial scintigraphic studies over 2 to 3 years. It was concluded that thallium myocardial perfusion imaging is a useful clinical technique to assess myocardial involvement in Duchenne's progressive muscular dystrophy.     

Prognostic value of normal stress myocardial perfusion imaging in Japanese population.

BACKGROUND: In Japan, Diagnosis Procedure Combination (DPC) of hospitalization health-care costs has been introduced since 2004, and its introduction has been recently expanded also to general hospitals. In such situations, the role of nuclear cardiology as a gatekeeper for the diagnosis of ischemic heart disease is increasingly important. Thus, the present study was designed to determine which clinical risk for hard events after normal single-photon emission computed tomography (SPECT) images, identify the predictors of increased risk in patients with normal SPECT images based on the J-ACCESS study. METHODS AND RESULTS: A total of 4,629 consecutively tested patients who underwent stress (99m)Tc-tetrofosmin SPECT at hospitals in Japan were included in the study. Based on SPECT image data, 1,862 participants had a summed stress score of or=49% in men, EF >or=55% in women), which is defined as selection criteria III (normal perfusion, ESV and EF). During the 3-year follow-up period, there was a total of 211 cardiac events (11.3%) in patients grouped in selection criteria I, 196 cardiac events (11.0%) in patients grouped in selection criteria II, and 189 cardiac events in patients grouped in selection criteria III (10.8%). The annual hard event rates were 0.81%, 0.67% and 0.63% in selection criteria I, II and III, respectively. Cox proportional hazard analysis showed that diabetes mellitus, age and hypertension were independent predictors of all cardiac events in all selection criteria. CONCLUSION: Normal stress myocardial perfusion imaging in the Japanese population is associated with a low cardiac event risk. The prognosis results of a normal SPECT scan would be useful for better patient management.     

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.     

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

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