Positron emission tomography detects evidence of viability in rest technetium-99m sestamibi defects

Objectives. The purpose of this study was to determine the relative value of single-photon emission computed tomographic (SPECT) imaging at rest using technetium-99m methoxyisobutyl isonitrile (technetium-99m sestamibi) with positron emission tomography for detection of viable myocardium.Background. Recent studies comparing positron emission tomography and thallium-201 reinjection with rest technetium-99m sestamibi imaging have suggested that the latter technique underestimates myocardial viability.Methods. Twenty patients with a previous myocardial infarction underwent rest technetium-99m sestamibi imaging and positron emission tomography using fluorine (F)-18 deoxyglucose and nitrogen (N)-13 ammonia. In each patient, circumferential profile analysis was used to determine technetium-99m sestamibi, F-18 deoxyglucose and N-13 ammonia activity (expressed as percent of peak activity) in nine cardiac segments and in the perfusion defect defined by the area having technetium-99m sestamibi activity <60%. Technetium-99m sestamibi defects were graded as moderate (50% to 59% of peak activity) and severe (<50% of peak activity). Estimates of perfusion defect size were compared between technetium-99m sestamibi and N-13 ammonia.Results. Sixteen (53%) of 30 segments with moderate defects and 16 (47%) of 34 segments with severe defects had ≥60% F-18 deoxyglocose activity considered indicative of viability. Fluorine-18 deoxyglucose evidence of viability was still present in 50% of segments with technetium-99m sestamibi activity <40%. There was no significant difference in the mean (± SD) technetium-99m sestamibi activity in segments with viable (40 ± 7%) and nonviable segments (49 ± 7%, p = 0.84). Of the 18 patients who had adequate F-18 deoxyglucose studies, the area of the technetium-99m sestamibi defect was viable in 5 (28%). In 16 patients (80%), perfusion defect size determined by technetium-99m sestamibi exceeded that measured by N-13 ammonia. The difference in defect size between technetium-99m sestamibi and N-13 ammonia was significantly greater in patients with viable (21 ± 9%) versus nonviable segments (7 ± 9%, p = 0.007).Conclusions. Moderate and severe rest technetium-99m sestamibi defects frequently have metabolic evidence of viability. Technetium-99m sestamibi SPECT yields larger perfusion defects than does N-13 ammonia positron emission tomography when the same threshold values are used.     

Gated technetium-99m sestamibi for simultaneous assessment of stress myocardial perfusion,postexercise regional ventricular function and myocardial viability: Correlation with echocardiography and rest thallium-201 scintigraphy

Objectives. This study compares technetium-99m sestamibi (sestamibi) electrocardiographic (ECG) gated single-photon emission computed tomography (gated SPECT) and echocardiography for the evaluation of myocardial function and assesses the feasibility of single-injection, single-acquisition stress perfusion/rest function technetium-99m sestamibi-gated SPECT as an alternative to conventional stress/rest imaging for assessment of myocardial perfusion and viability.Background. Simultaneous assessment of stress perfusion and rest function is possible with gated SPECT acquisition of stress-injected technetium-99m sestamibi.Methods. Rest thallium-201 SPECT followed by stress sestamibigated SPECT (acquired 0.5 to 1 h after sestamibi injection) was performed in 58 patients. Echocardiography was performed immediately after or before gated SPECT in 43 of the patients. All studies were analyzed by semiquantitative visual scoring. Sestamibi-gated SPECT studies were read for stress perfusion and rest wall motion and thickening. Reversibility on sestamibi-gated SPECT was defined as the presence of a definite stress defect with normal or mildly impaired wall motion or thickening on gated SPECT.Results. There was high segmental score agreement between gated SPECT and echocardiography for wall motion (91%, kappa = 0.68, p < 0.001) and thickening (90%, kappa = 0.62, p < 0.001). Correlation for global wall motion (r = 0.9S, p < 0.001) and thickening (r = 0.96, p < 0.001) scores between the two modalities was excellent. In 32 patients without previous myocardial infarction, there was excellent agreement for reversibility between stress sestamibi-gated SPECT and rest thallium-201/stress sestamibi (98%, kappa = 0.93, p < 0.01). However, in 26 patients with previous infarction, discordance between the two approaches was frequent, with 26% (20 of 78) of nonreversible defects by stress sestamibi-gated SPECT being reversible by rest thallium-201/stress sestamibi and 21% (23 of 112) of reversible defects by stress sestamibi-gated SPECT being nonreversible by rest thallium-201/stress sestamibi.Conclusions. Gated SPECT of stress-injected sestamibi correlates well with echocardiographic assessment of regional function and thus adds information to perfusion SPECT. In patients without previous myocardial infarction, a single-injection stress perfusion/rest function approach using sestamibi-gated SPECT can substitute for conventional stress/rest myocardial perfusion imaging, adding a rest perfusion study only if there are nonreversible defects or consideration of attenuation artifacts. In patients with previous myocardial infarction, the gated SPECT approach does not replace the need for a rest perfusion study.     

Comparison of electrocardiographic-gated technetium-99m sestamibi single-photon emission computed tomographic imaging and rest-redistribution thallium-201 in the prediction of myocardial viability

Although the combined assessment of perfusion and function using rest electrocardiographic (ECG)-gated technetium-99m (Tc-99m) sestamibi single-photon emission computed tomographic (SPECT) imaging has been shown to improve sensitivity and accuracy over perfusion alone in the prediction of myocardial viability, no data are available comparing this technique with rest-redistribution thallium-201. Thirty patients with coronary artery disease and left ventricular dysfunction (ejection fraction < or = 40%) underwent rest-redistribution thallium-201 and rest ECG-gated Tc-99m sestamibi SPECT imaging before revascularization and rest ECG-gated Tc-99m sestamibi SPECT imaging at 1 or 6 weeks after revascularization. All thallium-201 and Tc-99m sestamibi images were interpreted by a consensus agreement of 3 experienced readers without knowledge of patient identity or time of imaging with Tc-99m sestamibi (before or after revascularization) using a 17-segment model. Concordance between techniques for the prediction of viability was 89% (kappa 0.556 +/- 0.109). With rest-redistribution thallium-201, sensitivity, specificity, positive predictive value, negative predictive value, and predictive accuracy were 95%, 59%, 88%, 78%, and 86%, respectively. With rest ECG-gated Tc-99m sestamibi SPECT imaging, sensitivity, specificity, positive predictive value, negative predictive value, and predictive accuracy were 96%, 55%, 87%, 80%, and 86%, respectively (p = NS vs rest-redistribution thallium-201). Although both techniques are comparable for detecting viable myocardium, rest ECG-gated Tc-99m sestamibi SPECT imaging allows direct assessment of both myocardial perfusion and ventricular function, which may be clinically useful in patients who require assessment of myocardial viability.     

Technetium-99m sestamibi tomography in patients with spontaneous chest pain: correlations with clinical, electrocardiographic and angiographic findings.

The sensitivity and specificity of technetium-99m hexakis-2-methoxy-2-isobutyl-isonitrile (sestamibi) single-photon emission computed tomographic (SPECT) imaging for the diagnosis of coronary artery disease were studied in 45 patients admitted to the hospital for clinical suspicion of unstable angina. Only patients without prior myocardial infarction were included and all patients had technetium-99m sestamibi injection and a 12-lead electrocardiogram (ECG) during and less than or equal to 4 h after an episode of chest pain. Coronary angiography performed in all patients during hospitalization showed significant coronary artery disease (greater than or equal to 50% luminal diameter reduction) in 26 of the 45 patients. The SPECT studies obtained after injection of technetium-99m sestamibi during an episode of spontaneous chest pain showed a sensitivity of 96% for the detection of coronary artery disease; the 12-lead ECG obtained at the time of the injection had a sensitivity of 35%. With the patient in the pain-free state, respective sensitivity values were 65% and 38%. Specificity for the radionuclide study was 79% during pain and 84% in the pain-free state; for the ECG, it was 74% both during and between episodes of pain. The site of the perfusion defect corresponded to the most severe coronary artery lesion in 88% of patients. The severity of the perfusion defect correlated with the extent of coronary artery disease: the defect score was 5.3 +/- 3.3 with one-vessel disease, 4.9 +/- 2.8 with two-vessel disease and 10.5 +/- 5.0 with three-vessel disease (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of technetium-99m sestamibi and thallium-201 retention characteristics in canine myocardium.

OBJECTIVES. The aim of this study was to compare the myocardial retention of technetium-99m (Tc-99m) sestamibi and thallium-201 over a wide range of blood flow at different time points after tracer injection. BACKGROUND. Technetium-99m sestamibi has been proposed as a new perfusion tracer with better physical characteristics than those of thallium-201 for scintigraphic imaging. However, no studies have simultaneously compared the ability of both tracers to assess myocardial blood flow during pharmacologic vasodilation. METHODS. The myocardial retention of Tc-99m sestamibi and thallium-201 were compared over a wide range of blood flow induced by regional coronary occlusion and dipyridamole infusion in an open chest dog model. Myocardial retention of both tracers was determined by in vitro tissue counting at 2, 5, and 20 min after tracer injection and was correlated with microsphere-determined blood flow. RESULTS: Thallium-201 demonstrated greater absolute tissue retention than did Tc-99m sestamibi. At 2 min after tracer injection, there was an almost linear relation between the retention of both tracers and myocardial blood flow over a wide flow range. However, this relation was not maintained over time. At 20 min after injection, the retention of both tracers underestimated myocardial blood flow at higher flow rates. At 2, 5 and 20 min after injection, increments of relative tracer retention between the different levels of flow were always greater for thallium-201 than for Tc-99m sestamibi. CONCLUSIONS. Thallium-201 displays more suitable physiologic characteristics as a flow tracer and may allow better differentiation of myocardial regions with different levels of coronary flow reserve. For both tracers, early cardiac imaging may minimize underestimation of blood flow at higher flow rates.     

Use of technetium-99m sestamibi to determine the size of the myocardial area perfused by a coronary artery

The value of the new radionuclide tracer, technetium-99m (Tc-99m) sestamibi, to demonstrate myocardial perfusion in areas supplied by specific coronary arteries was evaluated in patients injected with the agent during cardiac catheterization. Tc-99m sestamibi differs from thallium-201 in its physical characteristics (photon energy 140 keV), half-life (6 hours) and lack of significant redistribution, allowing its administration during an episode of chest pain or ischemia occurring outside the nuclear medicine laboratory with later imaging to visualize the distribution. In 13 patients Tc-99m sestamibi was administered intravenously during balloon-occlusion angioplasty. In 11 of 13 patients, defects of the single photon emission computed tomography images corresponded to the area made ischemic during angioplasty. In the remaining 2 patients, abundant collateral flow was present and no defects were seen. In a second study, 15 patients had Tc-99m sestamibi selectively injected into a coronary artery during angiography. Later imaging identified the area supplied by the artery injected. Tc-99m sestamibi imaging can detect perfusion defects associated with short episodes of ischemia, and the area supplied by the different coronary arteries.     

Identification of severe and extensive coronary artery disease by postexercise regional wall motion abnormalities in Tc-99m sestamibi gated single-photon emission computed tomography

Postexercise wall motion abnormality (WMA) in patients with normal resting myocardial perfusion may represent prolonged postischemic stunning, and may be related to the presence of severe angiographic coronary artery disease (CAD). This study assesses the diagnostic value of postexercise WMA by technetium-99m (Tc-99m) sestamibi gated single-photon emission computed tomography (SPECT) in patients with normal resting perfusion. Ninety-nine patients underwent exercise gated Tc-99m sestamibi/resting thallium-201 SPECT and coronary angiography within 90 days of nuclear testing. All patients had normal perfusion at rest. Multivariate logistic regression analysis demonstrated an incremental value of wall motion and perfusion over perfusion data alone in identifying severe and extensive CAD. Sensitivity for identifying any severely stenosed coronary artery by WMA was significantly higher than by severe perfusion defect (78% vs 49%, p <0.0001). Overall specificities of severe perfusion defect and WMA were 91% and 85%, respectively (p = NS). Thus, postexercise WMA detected by gated Tc-99m sestamibi SPECT in patients with normal resting perfusion is a sensitive marker of severe and extensive CAD.     

Prognostic value of exercise stress myocardial perfusion imaging in patients with permanent pacemakers

One hundred eight patients with single- or dual-chamber pacemakers underwent exercise myocardial perfusion imaging with thallium-201 or technetium-99m sestamibi. A high-risk scan (a large fixed defect, a large reversible defect, or evidence of cardiomyopathy) identified patients at high risk for cardiac death on both a univariate and multivariate basis.     

Diagnostic testing of the emergency department patient with chest pain

In evaluating patients with nondiagnostic initial clinical or electrocardiogram (ECG) findings for acute cardiac ischemia, continuous 12-lead ECG monitoring increases the detection of diagnostic ECG findings, including ST-segment elevation, in patients awaiting hospital admission. Rest scanning with technitium-99m sestamibi is able to risk stratify low-moderate risk patients into lower and higher risk groups for cardiac events. Caveats include the reduced sensitivity of scanning of patients who are pain free and the need for follow-up exercise scans for patients free of perfusion defects at rest. Cardiac markers, particularly the troponins, show great promise for the detection of a larger part of the spectrum of acute coronary syndromes in the emergency department, including patients with minimal myocardial damage and higher risk for short-term death and nonfatal acute myocardial infarction. Accelerated diagnostic protocols using serial testing with cardiac markers, ECGs and then provocative testing over a 14-hour period, are feasible, safe, and cost-effective.     

Adenosine technetium-99m sestamibi myocardial perfusion SPECT in women: Diagnostic efficacy in detection of coronary artery disease

Objectives. This study sought to assess the diagnostic efficacy of adenosine technetium-99m (Tc-99m) sestamibi myocardial perfusion single-photon emission computed tomography (SPECT) in a consecutive series of female patients.Background. The utility of adenosine myocardial perfusion SPECT for the detection of coronary artery disease is not well defined in women because most studies have described a predominantly male population with a high prevalence of coronary artery disease.Methods. Of the 201 consecutive female patients in the study group who had undergone adenosine Tc-99m sestamibi myocardial perfusion SPECT, 130 had coronary angiography within 2 months of the nuclear test, and the other 71 had a low likelihood (<10%, mean [±SD] 5 ± 3%) of coronary artery disease. The SPECT protocol used separate acquisition of rest thallium-201 and adenosine Tc-99m sestamibi and was visually analyzed in 20 segments with a semiquantitative five-point scoring system (0 = normal; 4 = absent uptake).Results. The normaley rate in patients with a low likelihood of coronary artery disease was 93% (66 of 71). Among the catheterized group, the overall sensitivity, specificity and predictive accuracy of adenosine sestamibi SPECT for detecting coronary artery disease (⪰50% diameter stenosis) were 93% (87 of 94), 78% (28 of 36) and 88% (115 of 130), respectively. In the 103 patients without a prior myocardial infarction, the sensitivity, specificity and predictive accuracy were 91% (61 of 67), 78% (28 of 36) and 86% (89 of 103), respectively, for detecting ⪰50% diameter stenosis. Of particular interest, the sensitivity and specificity were as high in patients with nonanginal symptoms (93% and 69%, respectively) as in patients with angina (92% and 83%, respectively, p = NS). The sensitivity and specificity among patients with a relatively low (<25%), intermediate (between 25% and 75%) or high prescan likelihood of coronary artery disease (>75%) were similar: 82% and 82%, 93% and 73%, and 95% and 100%, respectively. The sensitivity and specificity for detecting individual diseased vessels (⪰50% diameter stenosis) were, respectively, 76% and 81% for the left anterior descending coronary artery, 44% and 90% for the left circumflex coronary artery and 75% and 77% for the right coronary artery.Conclusions. Adenosine Tc-99m sestamibi SPECT is an efficient protocol with high sensitivity and specificity for the detection of coronary artery disease in women irrespective of presenting symptoms or pretest likelihood of coronary artery disease and a high normaley rate. These findings are of particular clinical relevance because chest pain, anginal or otherwise, has been shown to be a frequent but a less specific marker for coronary artery disease among female patients.     

Risk assessment using single-photon emission computed tomographic technetium-99m sestamibi imaging

Objectives. This review summarizes the results of single-photon emission computed tomographic (SPECT) technetium-99m (Tc-99m) tracer imaging in patients with stable symptoms, patients with acute coronary syndromes, patients undergoing major noncardiac surgery and patients with chest pain in the emergency department.Background. Previous studies have examined the prognostic value of stress thallium imaging in several subsets of patients with ischemic heart disease. At present, >50% of myocardial perfusion studies are performed with technetium-labeled tracers in the United States. Furthermore, there is a shift from diagnostic to the prognostic utility of stress testing. There are important differences between technetium-labeled tracers and thallium-201. It is therefore important to review the prognostic value of technetium-labeled tracers.Methods. We analyzed published reports in English on risk assessment using Tc-99m perfusion tracers.Results. The largest experience is in patients with stable symptoms, comprising >12,000 patients in 14 studies. In these patients, normal stress SPECT sestamibi images were associated with an average annual hard event rate of 0.6% (death or nonfatal myocardial infarction [MI]). In contrast, patients with abnormal images had a 12-fold higher event rate (7.4% annually). Both fixed and reversible defects are prognostically important, and quantitative analysis shows increased risk in relation to the severity of the abnormality. These results are similar to those obtained with thallium-201.Conclusions. Patients with stable chest pain syndromes and normal stress SPECT sestamibi images have a very low risk of death or nonfatal MI. It is highly unlikely that coronary revascularization can improve survival in such patients. Patients with abnormal images have an intermediate to high risk for future cardiac events, depending on the degree of the abnormality. Further prospective studies comparing aggressive medical therapy with coronary revascularization in these patients are warranted.     

Myocardial perfusion after aortic implantation for anomalous origin of the left coronary artery from the pulmonary artery

Postoperative myocardial perfusion and function were evaluated using thallium-201 myocardial imaging and technetium-99m cardiac pool imaging in five patients with an anomalous left coronary artery arising from the pulmonary artery. The patients underwent reimplantation of the left coronary artery at an age ranging from 10 months to 13 years. Postoperative electrocardiographic and radionuclide studies were performed both at rest and during stress 1 to 4 years after the operation. Electrocardiograms which were abnormal preoperatively returned to normal after surgery except that the T wave in lead aVL remained negative. Postoperatively, left ventricular ejection fraction measured by technetium-99m cardiac pool imaging was normal in all patients. Postoperative thallium-201 myocardial imaging, however, showed a perfusion defect with incomplete redistribution at the high-lateral or antero-lateral segment in all patients after a stress test. These data suggest that although myocardial ischaemic change decreases and global cardiac function improves after establishment of a dual coronary artery system, severe myocardial damage remains at the high-lateral or antero-lateral segment.     

Comparison of the predischarge exercise thallium-201 perfusion defect after myocardial infarction with myocardium at risk measured during acute infarction with technetium-99m sestamibi imaging

Background Exercise thallium-201 imaging provides a noninvasive estimate of the amount of myocardium presumed to be at risk of infarcting should a complete occlusion of the coronary stenosis occur. The relationship between the size of the exercise thallium perfusion defect and the extent of myocardium supplied by a diseased coronary artery has not been established. This study evaluates that presumed correlation. Methods Patients were injected intravenously with technetium-99m sestamibi during acute myocardial infarction before thrombolysis or conventional therapy to quantify the myocardium at risk. Twenty-six patients who underwent risk-area assessment subsequently underwent clinically driven, predischarge, submaximal exercise imaging with thallium-201. The exercise testing was performed on day 7 ± 2 days. A conventional polar map display was used to quantify the perfusion defect. Results The myocardium at risk determined by technetium-99m sestamibi at the time of infarction was 30% ± 20% of the left ventricle. The mean exercise thallium-201 defect was 34% ± 22% of the left ventricle. The exercise defect tended to be slightly larger than the myocardium at risk (4% ± 10% of the left ventricle, P = .05). There was a close correlation between the 2 measurements (r = 0.89, SE = 9.4, P < .0001). Conclusions This study shows a close correlation between the myocardium “at risk” assessed acutely by technetium-99m sestamibi and the “presumed at-risk area” determined by thallium-201 imaging on predischarge exercise testing. This finding supports the concept that the size of the exercise thallium defect caused by coronary stenosis indicates the likely size of a myocardial infarction resulting from occlusion of that stenosis. (Am Heart J 2003;145:357-63.)     

Usefulness of technetium-99m sestamibi myocardial perfusion SPECT in detection of cardiovascular involvement in patients with systemic lupus erythematosus or systemic sclerosis

The main purpose of the study was to evaluate the utility of technetium-99m sestamibi myocardial perfusion single-photon emission computed tomography (Tc-99m sestamibi SPECT) in detection of cardiac involvement in systemic lupus erythematosus (SLE) or systemic sclerosis (SS) patients. Fifty SLE or SS female patients with cardiac symptom/sign such as chest discomfort and/or dyspnea and/or occasionally palpitation and 50 SLE or SS female patients without any cardiac symptom/sign were investigated using Tc-99m sestamibi SPECT during rest and stress after dipyridamole infusion. Twenty-five age- and sex-matched healthy females were also included as controls in this study. The results of Tc-99m sestamibi SPECT were classified into four types including normal, persistent perfusion defect (PD), reversible perfusion defect (RD), and reverse perfusion defect (RR). The results of Tc-99m sestamibi SPECT in the 25 healthy females were normal. Perfusion abnormalities were detected in 44/50 (88%) symptomatic SLE or SS patients. However, myocardial perfusion abnormalities were only detected in 19/50 (38%) asymptomatic SLE or SS patients (P value<0.05 by a chi2 test). However, for risk factor of coronary artery disease and abnormal resting EKG, the incidences were not significant between symptomatic and asymptomatic patients (P values >0.05 by a chi2 test). Tc-99m sestamibi SPECT is a useful noninvasive imaging modality to detect cardiac involvement in symptomatic or asymptomatic SLE or SS patients.     

Serial quantitative planar technetium-99m isonitrile imaging in acute myocardial infarction: efficacy for noninvasive assessment of thrombolytic therapy

Technetium-99m isonitrile is a new myocardial perfusion imaging agent that accumulates according to the distribution of myocardial blood flow. However, unlike thallium-201, it does not redistribute over time. This imaging agent was used with serial quantitative planar imaging to assess the initial risk area of infarction, its change over time and the relation to infarct-related artery patency in 30 patients with a first acute myocardial infarction. Twenty-three of 30 patients were treated with recombinant tissue-type plasminogen activator (rt-PA) within 4 h after the onset of chest pain. Seven patients were treated in the conventional manner without thrombolytic therapy. Technetium-99m isonitrile was injected before or at the initiation of thrombolytic therapy, and imaging was performed several hours later. These initial images demonstrated the area at risk. Repeat imaging was performed 18 to 48 h later and at 6 to 14 days after the onset of myocardial infarction to visualize the ultimate extent of infarction. The initial area at risk varied greatly (range defect integral 2 to 61) both in patients treated with rt-PA and in those who received conventional treatment. For the total group, the initial imaging defect decreased in size in 20 patients and was unchanged or larger in 10 patients. Patients with a patent infarct-related artery had a significantly greater decrease in defect size than did patients with persistent coronary occlusion (-51 +/- 38% versus -1 +/- 26%, p = 0.0001). All patients with a decrease in defect size greater than 30% had a patent infarct-related artery. In 12 patients who also had predischarge quantitative exercise thallium-201 imaging, good agreement existed between the extent and severity of myocardial perfusion defect on the last technetium-99m isonitrile study before discharge and that noted on delayed thallium-201 imaging. It is concluded that serial planar technetium-99m isonitrile myocardial imaging in patients with acute myocardial infarction undergoing thrombolytic therapy offers a new quantitative noninvasive approach for assessment of the initial risk zone as well as the success of reperfusion.     

Myocardial perfusion imaging with technetium-99m sestamibi SPECT in the evaluation of coronary artery disease

Technetium-99m (Tc-99m) sestamibi is a new myocardial perfusion imaging agent that offers significant advantages over thallium-201 (Tl-201) for myocardial perfusion imaging. The results of the current clinical trials using acquisition and processing parameters similar to those for Tl-201 and a separate (2-day) injection protocol suggest that Tc-99m sestamibi and Tl-201 single photon emission computed tomography (SPECT) provide similar information with respect to detection of myocardial perfusion defects, assessment of the pattern of defect reversibility, overall detection of coronary artery disease (CAD) and detection of disease in individual coronary arteries. Tc-99m sestamibi SPECT appears to be superior to Tc-99m sestamibi planar imaging because the former provides a higher defect contrast and is more accurate for detection of disease in individual coronary arteries. Research is currently under way addressing optimization of acquisition and processing of Tc-99m sestamibi studies and development of quantitative algorithms for detection and localization of CAD and sizing of transmural and nontransmural myocardial perfusion defects. It is expected that with the implementation of the final results of these new developments, further significant improvement in image quality will be attained, which in turn will further increase the confidence in image interpretation. Development of algorithms for analysis of end-diastolic myocardial images may allow better evaluation of small and nontransmural myocardial defects. Furthermore, gated studies may provide valuable information with respect to regional myocardial wall motion and wall thickening. With the implementation of algorithms for attenuation and scatter correction, the overall specificity of Tc-99m sestamibi SPECT should improve significantly because of a substantial decrease in the occurrence of attenuation-related image artifacts.(ABSTRACT TRUNCATED AT 250 WORDS)     

Clinical correlation between increased lung to heart ratio of technetium-99m sestamibi and multivessel coronary artery disease

BACKGROUND: An increased lung to heart ratio (LHR) on thallium-201 (Tl-201) stress myocardial perfusion imaging (MPI) is a predictor of adverse cardiac events and identifies people with extensive coronary artery disease (CAD). The implications of increased LHR in patients undergoing stress technetium-99m (tc-99m) sestamibi are developing. Our aim is to evaluate the relationship between increased LHR and extent of CAD in patients undergoing tc-99m sestamibi MPI. METHODS: We reviewed the records and images of 530 consecutive subjects who underwent exercise or adenosine tc-99 m sestamibi MPI. One hundred thirty-two had transient or partially reversible myocardial perfusion defects and 79 (exercise=34, adenosine=45, male=43, female=36, mean age=61 years) of these underwent coronary angiography (study population). The average LHR of these 79 subjects was compared to 79 patients (control population) with normal scans (exercise=50, adenosine=29, male=34, female=45, mean age=60 years). RESULTS: The mean LHR (+/-SE) in subjects with normal scans was 0.30+/-0.01. The mean LHR for those with abnormal scans and single vessel CAD who underwent exercise was 0.32+/-0.01 and pharmacological stress was 0.31+/-0.01. There was no statistically significant difference between the LHR of those with a normal scan and those with single vessel disease and an abnormal scan. However, there was a statistically significant association between the elevated LHR and multi-vessel CAD. The mean LHR for subjects with multi-vessel CAD with exercise was 0.39+/-0.01 (p=0.000) and for adenosine was 0.39+/-0.02 (p=0.000). CONCLUSION: An elevated LHR in patients undergoing exercise or pharmacological tc-99m MPI correlates with multi-vessel CAD.     

Evaluation of patients with chest pain and nondiagnostic ECG using thallium-201 myocardial planar imaging and technetium-99m first-pass radionuclide angiography in the emergency department.

STUDY OBJECTIVE: The purpose of this study was to determine if thallium-201 myocardial planar imaging and technetium-99m first-pass radionuclide angiography, performed in the emergency department, could predict which patients with acute chest pain and nondiagnostic ECGs were more likely to have an acute myocardial infarction (AMI). DESIGN: Retrospective analysis. SETTING: Urban, county ED. TYPE OF PARTICIPANTS: Convenience sample of 47 patients with acute chest pain suggestive of myocardial ischemia and nondiagnostic ECG. INTERVENTIONS: Thallium-201 myocardial imaging and technetium-99m first-pass radionuclide angiography in the ED. MEASUREMENTS AND MAIN RESULTS: Four patients had an AMI (ie, CK-MB greater than or equal to 6% total CK). The combined scans had a sensitivity of 75%, (95% confidence interval [Cl], 19-99%), a specificity of 42% (95% CI, 27-58%), an accuracy of 45% (95% CI, 19-99%), a positive predictive value of 11% (95% CI, 2-29%), and a negative predictive value of 95% (95% CI, 75-100%) in predicting AMI. CONCLUSION: Thallium-201 myocardial planar imaging and technetium-99m first-pass radionuclide angiography performed in the ED do not appear to be useful in determining which patients with acute chest pain and nondiagnostic ECG are likely to have an AMI.     

Experimental studies of the physiologic properties of technetium-99m isonitriles

Recently, efforts have been directed at the development of technetium-99m (Tc-99m)-labeled isonitrile compounds for assessment of regional perfusion and viability after experimental myocardial infarction or ischemia. One of the most promising of these agents, Tc-99m sestamibi, has undergone rather extensive laboratory investigation. Like thallium-201 (Tl-201), the uptake of Tc-99m sestamibi in myocardial tissue is proportional to myocardial blood flow after intravenous injection. Similar to other diffusible indicators, Tc-99m sestamibi underestimates blood flow at high flow rates. In low flow regions, the myocardial uptake of this agent is higher relative to nonischemic uptake than is microsphere-determined blood flow. This is attributed to increased extraction at low flows. This first-pass myocardial extraction fraction for Tc-99m sestamibi is less than that for Tl-201. However, Tc-99m sestamibi has a higher parenchymal cell permeability and higher volume of distribution than T;-201. Tc-99m sestamibi shows minimal "delayed redistribution" after initial intravenous administration. Uptake of Tc-99m sestamibi is not altered by myocardial "stunning" or with ischemic dysfunction produced by sustained low coronary flow. The uptake of the isonitrile is still proportional to blood flow in these situations. In intact animal models, myocardial uptake of Tc-99m sestamibi during coronary occlusion delineates the in vivo area at risk. When Tc-99m sestamibi is administered after reperfusion following variable periods of preceding coronary occlusion, Tc-99m sestamibi uptake delineates the area of viable myocardium that is salvaged and not simply the degree of reflow. This suggests that serial Tc-99m sestamibi imaging might be useful in assessing the efficacy of coronary reperfusion after thrombolytic therapy.     

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

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