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Leaves of plants have the ability to accumulate the long-lived fission product (99)Tc. In the present work, an attempt was made to separate and characterize technetium species formed in maize grown on soil contaminated with Tc(VII)O(4)(-) solution. Data obtained from selective extraction, a Phosphorimager and liquid scintillation were employed.
In post-closure radiological safety assessments of repositories for solid radioactive wastes, transfers of radionuclides to animal products are typically characterised using Transfer Factors (TFs), defined as the ratio of the concentration of the radionuclide in the animal product of interest to the rate of intake in diet. Such transfer factors can be measured directly in experimental studies, but they can also be estimated by use of biokinetic models for uptake and retention of radionuclides in animals. Based on a review of the literature, biokinetic models have been developed for the uptake and retention of iodine, technetium, selenium and uranium. These biokinetic models allow TF values to be estimated for different types of animals and for different animal lifetimes. For each radionuclide considered, reference values and ranges of TF values are estimated. These are summarised in Table 1.
Natural products are widely used as food or food additives or medicines for humans. We are trying to develop a model to assess the possible toxic properties of natural products, such as Fucus vesiculosus, utilized in popular medicine. Red blood cells (RBC) labeled with technetium-99m (99mTc) are used in various procedures in nuclear medicine. This labeling procedure depends on a reducing agent, and stannous chloride is used. There is evidence that this labeling may be altered by drugs. We have investigated the possibility that F. vesiculosus extract is capable of altering the labeling of blood elements with 99mTc. Blood was incubated with F. vesiculosus extract and stannous chloride solution and Tc-99m added. Blood was centrifuged and plasma (P) and blood cells (BC) were isolated. Samples of P or BC were also precipitated, centrifuged and insoluble (IF) and soluble (SF) were separated. The percentages of radioativity (%ATI) in BC, IF-P and IF-BC were calculated. Histological preparations of the RBC treated with F. vesiculosus revealed that this extract is capable of promoting important modifications on the shape of the RBC. The%ATI decreased on BC from 93.6+/-2.3 to 29.0+/-2.7, on IF-P from 77.6+/-1.2 to 7.5+/-1.0 and on IF-BC from 80.0+/-3.4 to 12.6+/-4.8. Once the RBC labeling procedure with 99mTc depends on the presence of stannous (+2) ions, the substances present in the F. vesiculosus extract should increase the valence of these ions to stannic (+4). This would decrease the%ATI on blood elements and indicate the presence of oxidant agents in the F. vesiculosus extract.
In vitro studies have shown that technetium-99m methoxyisobutylisonitrile (Tc-99m MIBI) is a transport substrate for the P-glycoprotein (Pgp) pump. Therefore, Tc-99m MIBI uptake of tumors can be used to predict chemotherapy response in lung cancers. However, whether lung resistance-related protein (LRP) expression affects tumor accumulation and efflux of Tc-99m MIBI in lung cancers is not known. Our aim was to use Tc-99m MIBI uptake of tumors to predict Taxol based chemotherapy response of advanced non-small cell lung cancer (NSCLC) and to compare Pgp or LRP expression. Before chemotherapy with Taxol, 30 patients with stage IIIb or IV NSCLC were enrolled in this study. Chemotherapy response was evaluated in the third month after completion of treatment by clinical and radiological methods. No significant differences were found for other prognostic factors (age, sex, body weight loss, performance status, tumor cell type, and tumor stage) between the 15 patients with good response and the other 15 patients with poor response. Early chest single photon emission computed tomography (SPECT) was performed 10 min after intravenous injection of Tc-99m MIBI. Early tumor-to-normal lung (T/L) uptake ratios were calculated quantitatively on Tc-99m MIBI chest SPECT images. Immunohistochemical analyses were performed on multiple nonconsecutive sections of the biopsy specimens to determine Pgp and LRP expressions. The T/L uptake ratios on early Tc-99m MIBI chest SPECT images of 15 patients with good response were significantly higher than those of the other 15 patients with poor response. Significantly higher T/L uptake ratios were found in patients with negative than positive Pgp expression (p<0.05). However, no significant differences of T/L uptake ratios were found between patients with negative and positive LRP expressions (p>0.05). We concluded that Tc-99m MIBI chest SPECT could accurately predict Taxol base chemotherapy response of patients with advanced NSCLC. In addition, The Tc-99m MIBI tumor uptake was related to Pgp but not LPR expression in NSCLC.
We are trying to develop a model to assess properties of products utilized in popular medicine. Maytenus ilicifolia is used in herbal medicine. Red blood cells (RBC) labeled with technetium-99m (99mTc) are employed in nuclear medicine. This labeling procedure depends on a reducing agent and stannous chloride is used. There is evidence that this labeling may be altered by drugs. We have investigated the possibility of M. ilicifolia extract being capable to alter the labeling of blood elements with 99mTc. Blood was incubated with M. ilicifolia extract. Stannous chloride solution and Tc-99m were added. Blood was centrifuged and plasma (P) and blood cells (C) were isolated. Samples of P or C were also precipitated, centrifuged and insoluble (IF) and soluble (SF) were separated. The percentages of radioactivity (%ATI) in C, IF-P and IF-C was calculated. The %ATI decreased on C from 93.6+/-2.3 to 29.0+/-2.7, on IF-P from 77.6+/-1.2 to 7.5+/-1.0 and on IF-C from 80.0+/-3.4 to 12.6+/-4.8. Once in RBC labeling procedure with 99mTc depends on the presence of stannous (+2) ions, the substances of the M. ilicifolia extract could increase the valence these ions to stannic (+4). This fact would decrease the %ATI on blood elements and indicate the presence of oxidant agents in the M. ilicifolia extract.
99mTc-TRODAT-1 (technetium(V)-oxo-2-[[2-[[[3-(4-chlorophenyl)-8-methyl-8-azabicyclo[3.2.1]oct-2-yl]methyl](2-mercaptoethyl)amino]ethyl]]amino]-ethanethiolato(3-)) and 99mTc-TRODAT-M, the 4-methylphenyl derivative of 99mTc-TRODAT-1, are at this moment being evaluated in clinical trials as imaging agents for the central nervous dopamine transporter system. Both compounds are formed as a mixture of two major diastereomers. As the tracer concentration in preparations for clinical investigations is very low (30-150 pmol/ml), identification of these 99mTc-complexes was, up to now, carried out indirectly using X-ray diffraction analysis of the corresponding rhenium complexes which can be synthesized in gram amounts. In this study, we developed a convenient and practical reversed phase HPLC-method for purification and isolation of the respective diastereomers of 99mTc-TRODAT-1 and three of its derivatives using mixtures of solvents which are compatible with biological studies, i.e. aqueous buffers and ethanol. Furthermore, direct identity confirmation of the 99mTc-complexes using radio-LC-MS was successfully elaborated.
OBJECTIVES: We sought to determine whether right ventricular (RV) perfusion imaging with technetium-99m (Tc-99m) sestamibi or tetrofosmin single-photon emission computed tomography has diagnostic benefit for RV-originated ventricular tachyarrhythmias (RVT). BACKGROUND: Identification of RV abnormalities is clinically important to establish RVT etiology. METHODS: Forty-seven patients with RVT (23 with idiopathic and 24 with organic RVT due to arrhythmogenic RV or dilated cardiomyopathy, cardiac sarcoidosis or myocarditis) were compared to 25 control subjects. Right ventricular uptake score, as assessed by modified tomographic imaging, and regional RV count relative to peak left ventricular (LV) count (RV/LV count ratio) were compared with RV regional and global function. RESULTS: Regional RV uptake score correlated well with the RV/LV count ratio, and segmental abnormality was more frequently (p = 0.001) detected in the organic RVT group (22 [92%] of 24 patients) than in the idiopathic RVT group (4 [17%] of 23 patients) or the control group (8 [32%] of 25 patients). The total RV score (8.4+/-3.8) in the organic RVT group was significantly lower than that in the idiopathic RVT group (15.6+/-1.6) or the control group (15.1+/-1.8). The total RV score correlated with RV EF (r = 0.702, p<0.001). A total RV score <12 differentiated the organic RVT group from the other two groups, with a sensitivity of 79% and a specificity of 100%. The asynergic RV regions had a significantly lower RV/LV count ratio and RV score as compared with the nonasynergic regions and were identified by RV assessment, with a sensitivity of 76.1% and a specificity of 76.6%. CONCLUSIONS: Right ventricular perfusion tomography using a Tc-99m-labeled tracer is clinically useful for the noninvasive detection of RV myocardial damage in patients with RVT and for differentiating organic from idiopathic RVT.
OBJECTIVES: We sought to perform a direct comparison between perfusion scintigraphic results and intracoronary-derived hemodynamic variables (fractional flow reserve [FFR]; absolute and relative coronary flow velocity reserve [CFVR and rCFVR, respectively]) in patients with two-vessel disease. BACKGROUND: There is limited information on the diagnostic accuracy of intracoronary-derived variables (CFVR, FFR and rCFVR) in patients with multivessel disease. METHODS: Dipyridamole technetium-99m sestamibi (MIBI) single-photon emission computed tomography (SPECT) was performed in 127 patients. The presence of reversible perfusion defects in the region of interest was determined. Within one week, angiography was performed; CFVR, rCFVR and FFR were determined in 161 coronary lesions after intracoronary administration of adenosine. The predictive value for the presence of reversible perfusion defects on MIBI SPECT of CFVR, rCFVR and FFR was evaluated by the area under the curve (AUC) of the receiver operating characteristics curves. RESULTS: The mean percentage diameter stenosis was 57% (range 35% to 85%), as measured by quantitative coronary angiography. Using per-patient analysis, the AUCs for CFVR (0.70 +/- 0.052), rCFVR (0.72 +/- 0.051) and FFR (0.76 +/- 0.050) were not significantly different (p = NS). The percentages of agreement with the results of MIBI SPECT were 76%, 78% and 77% for CFVR, rCFVR and FFR, respectively. Per-lesion analysis, using all 161 measured lesions, yielded similar results. CONCLUSIONS: The diagnostic accuracy of three intracoronary-derived hemodynamic variables, as compared with the results of perfusion scintigraphy, is similar in patients with two-vessel coronary artery disease. Cut-offvalues of 2.0 for CFVR, 0.65 for rCFVR and 0.75 for FFR can be used for clinical decision-making in this patient cohort. Discordant results were obtained in 23% of the cases that require prospective evaluation for appropriate patient management.
OBJECTIVES: This work was undertaken to define the intrinsic cardiac risk of the patient population referred for dobutamine stress perfusion imaging and to determine whether dobutamine technetium-99m ((99m)Tc)-sestamibi single-photon emission computed tomography (SPECT) imaging is capable of risk stratification in this population. BACKGROUND: In animal models, dobutamine attenuates the myocardial uptake of (99m)Tc-sestamibi resulting in underestimation of coronary stenoses. Therefore, we hypothesized that the prognostic value of dobutamine stress (99m)Tc-sestamibi SPECT myocardial perfusion imaging might be impaired, owing to reduced detection of coronary stenoses. METHODS: We reviewed the clinical outcome of 308 patients (166 women, 142 men) who underwent dobutamine stress SPECT (99m)Tc-sestamibi imaging at our institution from September 1992 through December 1996. RESULTS: During an average follow-up of 1.9 +/- 1.1 years, there were 33 hard cardiac events (18 myocardial infarctions [MI] and 15 cardiac deaths) corresponding to an annual cardiac event rate of 5.8%/year, which is significantly higher than the event rate for patients referred for exercise SPECT imaging at our institution (2.2%/year). Event rates were higher after an abnormal dobutamine (99m)Tc-sestamibi SPECT study (10.0%/year) than after a normal study (2.3%/year) (p < 0.01), even after adjusting for clinical variables. In the subgroup (n = 29) with dobutamine-induced ST-segment depression and abnormal SPECT imaging, the prognosis was poor, with annual cardiac death and nonfatal MI rates of 7.9% and 13.2%, respectively. CONCLUSIONS: Patients referred for dobutamine perfusion imaging are a high-risk population, and dobutamine stress (99m)Tc-sestamibi SPECT imaging is capable of risk stratification in these patients.
OBJECTIVES: We sought to determine the level of angiographic stenosis at which reversible regional wall motion abnormalities (RWMA) are present on exercise stress technetium-99m (Tc-99m)- gated single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI), and whether assessments of stress and rest RWMA add incremental diagnostic information. BACKGROUND: Stress and rest gated SPECT MPI enables the detection of post-exercise stunning. Although some studies have correlated RWMA to the severity of MPI defects, only one previous study correlated RWMA on gated MPI to angiographic findings. However, this correlation excluded patients with rest perfusion defects and did not involve gating of rest images. METHODS: One hundred patients undergoing angiography within six months of exercise stress Tc-99m (sestamibi)-gated SPECT MPI (in the absence of interim cardiac events or revascularization) were recruited. Images were acquired 15 to 30 min after stress and interpreted without knowledge of the Duke treadmill score, left ventricular ejection fraction and angiographic data. RESULTS: The sensitivity of reversible RWMA for angiographic stenoses >70% was 53%, with a specificity of 100%. The presence of reversible RWMA was able to stratify patients with angiographic stenoses of 50% to 79% and 80% to 99% with a high positive predictive value. A good correlation was noted between the presence of reversible RWMA and the coronary artery jeopardy score (R = 0.49, p < 0.0001). Multivariate analysis showed that the post-stress RWMA, Duke treadmill and reversible RWMA scores were significant predictors of angiographic severity. CONCLUSIONS: Post-stress and reversible RWMA, as shown by exercise stress Tc-99m-gated SPECT MPI, are significant predictors of angiographic disease and add incremental value to MPI for the assessment of angiographic severity.
Single photon emission computed tomography (SPECT) with technetium-99m hexakis 2-methoxyisobutyl isonitrile was investigated as a method to evaluate the results of intravenous thrombolytic treatment in 14 patients (11 men and 3 women) with acute myocardial infarction admitted to the coronary care unit within 4 h of the onset of symptoms. All patients received an injection of 740 MBq of the tracer before starting the thrombolytic therapy, and isonitrile tomography was performed 3 to 4 h later. The tomographic study was repeated 5 days after the acute event. The results of thrombolytic treatment were independently evaluated taking into account the clinical, electrocardiographic (ECG) and enzymatic data and the findings of left ventricular and coronary angiography. Furthermore, all patients were studied with two-dimensional echocardiography on admission, 5 days later and 1 month later. The site and extent of the perfusion defects on admission scintigraphy were consonant with the ECG and echocardiographic findings. A good correlation could be established between the 5 day scintigraphic estimate of infarct dimension and the enzymatic infarct size (r = 0.907, p less than 0.00002). The comparison between pre- and postthrombolytic treatment images enabled the identification of successful and unsuccessful reperfusion even in patients whose other noninvasive findings were inconclusive. Finally, the reduction in defect size predicted late functional improvement that was demonstrated by echocardiography performed 1 month later (r = 0.89, p less than 0.00005). The results of the study suggest the feasibility and the possible usefulness of isonitrile tomography in demonstrating the presence and size of myocardial damage and in assessing the extent of myocardial salvage after thrombolytic therapy in acute myocardial infarction.
Ultrashort-lived iridium-191m (Ir-191m, physical half-life = 5.0 seconds) has been used in angiocardiography, primarily in pediatric patients. A theoretical obstacle to more widespread use of Ir-191m is the belief that its physical half-life is too short to permit evaluation of left ventricular function in adult patients. To evaluate its usefulness in adults, first pass ejection fractions of the left and right ventricles determined with use of Ir-191m and technetium-99m (Tc-99m) were compared in 33 adult patients. An osmium-191m----iridium-191m (Os-191----Ir-191m) generator was employed to deliver doses of 150 to 250 mCi (5.5 to 9.2 GBq) of Ir-191m for intravenous injection. The whole body radiation absorbed dose with Ir-191m was 15 to 25 mrad. High quality angiocardiograms were obtained with both Tc-99m and Ir-191m. Total counts per image for the right ventricle were 51,000 +/- 8,000 (mean +/- SD) for Ir-191m and 30,000 +/- 8,000 for Tc-99m. The left ventricular counts were comparable for both radiotracers (25,000 +/- 7,000 for Ir-191m and 25,000 +/- 8,000 for Tc-99m). Right ventricular ejection fractions were similar: 44 +/- 8% for Ir-191m and 47 +/- 9% for Tc-99m. The correlation coefficient was 0.93 with a standard deviation of the regression of 3.1% ejection fraction units. The left ventricular ejection fractions were also similar: 45 +/- 14% for Ir-191m and 46 +/- 13% for Tc-99m. The left ventricular ejection fraction correlation coefficient was 0.96 with a standard deviation of the regression of 3.7%.(ABSTRACT TRUNCATED AT 250 WORDS)
OBJECTIVES: This study aimed to define the optimal criteria for detecting viable myocardium with rest-redistribution thallium-201 (Tl-201) or baseline-nitrate technetium-99m (Tc-99m) sestamibi single-photon emission computed tomography (SPECT) using discriminant analysis and to compare the accuracy of the two tracers in predicting postrevascularization recovery. BACKGROUND: Rest-redistribution Tl-201 imaging is currently used for detection of myocardial viability, but the optimal variables for territory classification have not yet been defined. Although Tc-99m sestamibi is reportedly less effective than Tl-201, its reliability can be increased by injecting it during nitrate infusion. METHODS: In 35 patients with left ventricular (LV) dysfunction, tracer activity within asynergic coronary territories was quantified on rest and redistribution Tl-201 and baseline and nitrate Tc-99m sestamibi SPECT. Asynergic territory viability was evaluated on the basis of the postrevascularization functional outcome. RESULTS: Percent activity within asynergic territories was significantly influenced by their viability (p < 0.005) and the type of acquisition (p < 0.0001) but not by the tracer used. Discriminant analysis identified redistribution Tl-201 activity and nitrate-induced Tc-99m sestamibi activity change as the two most significant predictors of postrevascularization recovery. The discriminant function defined for Tl-201, including redistribution activity and reversibility, correctly classified 38 of 56 asynergic territories, whereas that for Tc-99m sestamibi, including nitrate-induced activity change and activity in nitrate images, correctly classified 43 territories. CONCLUSIONS: Redistribution activity is more important than reversibility when differentiating viable from nonviable territories using rest-redistribution Tl-201. In Tc-99m sestamibi SPECT, nitrate-induced activity changes are particularly useful in identifying myocardial viability. Baseline-nitrate Tc-99m sestamibi SPECT appears no less effective than rest-redistribution Tl-201 in predicting postrevascularization recovery.
OBJECTIVES: We developed an automatic quantitative algorithm for the measurement of regional myocardial wall motion and wall thickening from three-dimensional gated technetium-99m sestamibi myocardial perfusion single-photon emission computed tomographic images. BACKGROUND: The algorithm measures the motion of the three-dimensional endocardial surface using a modification of the centerline method, as well as wall thickening using both geometry (gaussian fit) and partial volume (counts). METHODS: The algorithm was tested using a "variable thickness" heart phantom, and the quantitative results were compared with visual segmental assessment of myocardial motion and thickening in 79 clinical patients with a wide range of ejection fractions (6% to 87%). RESULTS: Phantom measurements of simulated motion and thickening were accurate regardless of the camera used (dual or triple detector), the angular span of reconstructed data (180 degrees or 360 degrees), the amount of motion (3 or 6 mm) or the amount of thickening (33%, 50% or 100%). Quantitative measurements of segmental motion and thickening in the patients were correlated with visual scores (r = 0.668, exact agreement 72.6%, kappa 0.433 and r = 0.550, exact agreement 74.7%, kappa 0.408, respectively). Significant inverse linear relations exist between the global (summed) visual motion score and the average quantitative motion, and between the global (summed) visual thickening score and the average quantitative thickening. Automatic quantitative ejection fraction measurements correlated extremely well with average quantitative motion (r = 0.929) and thickening (r = 0.959). CONCLUSIONS: Our algorithm is accurate and may be the first automatic technique for the quantitative three-dimensional assessment of regional ventricular function in cardiology.
OBJECTIVES: The purpose of this study was to determine how frequently and for what reasons the addition of electrocardiographically gated technetium-99m (Tc-99m) sestamibi single-photon emission computed tomographic (SPECT) images add value to nongated SPECT perfusion images. BACKGROUND: Electrocardiographic gating of Tc-99m sestamibi SPECT images permits assessment of regional and global left ventricular function and may assist in differentiating attenuation artifacts from myocardial scar. METHODS: A total of 285 consecutive patients (143 women and 142 men; mean age 57.6 +/- 11.5 years) underwent gated SPECT Tc-99m sestamibi imaging (212 with exercise, 63 with dipyridamole and 10 with dobutamine). The conventional stress and rest tomograms were interpreted first by means of a 14-segment scoring system, and then the studies were reinterpreted while the gated images were viewed. RESULTS: In the total group of 285 patients, the number of "borderline" interpretations was reduced from 89 to 29. In the 137 patients with a < or = 10% pretest likelihood of coronary artery disease, the addition of gated images added significantly to the percentage of interpretations that were designated "normal" (74% [101 of 137] vs. 93% [127 of 137], p < 0.0001), due to a reduction in borderline normal and borderline abnormal readings. In 49 patients with a previous infarction or recent angiography with > or = 70% stenosis, or both, the addition of gated images changed the percentage of "abnormal" scan interpretations from 78% (38 of 49) to 92% (45 of 49). This result was not significant (p = 0.09, two-tailed), but the trend was toward a greater number of unequivocal abnormal interpretations in this subgroup. CONCLUSIONS: The addition of electrocardiographically gated Tc-99m sestamibi SPECT images to the reading of stress and rest perfusion images alone resulted in shifting the final scan interpretations to a more normal designation in patients with a low pretest likelihood of coronary artery disease, and to more abnormal defects consistent with coronary artery disease in patients with known coronary artery disease. The number of "borderline normal" and "borderline abnormal" interpretations are significantly reduced when gated SPECT images are interpreted simultaneously with stress and rest perfusion images.
OBJECTIVES: We sought to prospectively identify patients with stunning and hyperkinesia at hospital discharge on the basis of mismatches between left ventricular (LV) function and infarct size as assessed by technetium-99m (Tc-99m) sestamibi perfusion tomographic imaging. BACKGROUND: Mechanical indexes of LV function may not accurately reflect myocardial damage after acute myocardial infarction (MI) because of myocardial stunning and compensatory hyperkinesia in noninfarct-related territories. Myocardial perfusion techniques are unaffected by these variables. METHODS: Eighty-four patients with acute MI underwent hospital admission and discharge Tc-99m-sestamibi tomographic imaging. Global LV ejection fraction (LVEF) was measured at hospital discharge and 6 weeks later. The perfusion defect size was quantified and expressed as a percentage of the LV. The discharge perfusion defect, which is a measure of infarct size, was used to predict the 6-week LVEF for each patient based on a previously reported regression equation. Patients were classified into one of three groups depending on whether their LVEF at hospital discharge fell within, above or below one standard error (6.8 LVEF points) of the predicted 6-week LVEF. RESULTS: There were 48 patients classified as having a "match" between function and infarct size; these patients demonstrated no significant change in LVEF at 6 weeks. There were 21 patients (25%) classified as "mismatch stunned" who had discharge LVEFs lower than those predicted by infarct size. These patients demonstrated a significant improvement in mean LVEF at 6 weeks (mean [+/-SD] discharge LVEF 0.41 +/- 0.08, 6-week LVEF 0.47 +/- 0.10; p = 0.003). Fifteen patients (18%) were classified as "mismatch-hyperkinetic." The mean LVEF for these patients significantly declined at 6 weeks (discharge LVEF 0.64 +/- 0.06, 6-week LVEF 0.58 +/- 0.09; p = 0.002). There was a marked increase in LVEF within the infarct zone (8 +/- 15 LVEF points; p = 0.03) for patients predicted to have stunning and a marked decline in LVEF outside the infarct zone (9 +/- 15 LVEF points; p = 0.06) in patients predicted to have hyperkinesia. Both discharge LVEF (p < 0.0001) and group classification (p = 0.005) were independent predictors of LVEF 6 weeks later. CONCLUSIONS: Perfusion imaging with Tc-99m-sestamibi can identify post-MI patients at hospital discharge in whom LV function is discordant with the measured infarct size. Patients with stunning have late increases in LVEF; patients with hyperkinesia have late decreases. This methodology, performed at discharge, is predictive of late changes in LV function.
OBJECTIVE: The value of rest technetium-99m (Tc-99m) sestamibi scintigraphy under oral nitrate medication to predict myocardial viability was examined in patients with chronic infarcts. BACKGROUND: The value of rest Tc-99m sestamibi to predict viability in infarct regions has not been fully established because significant underestimation of viability, especially in the inferior myocardial wall, has been reported. METHODS: Forty patients with Q wave myocardial infarction underwent Tc-99m sestamibi single-photon emission computed tomography under nitrate medication before revascularization of the infarct-related artery. Wall motion was quantified from paired angiograms before and 4 months after revascularization. Tracer uptake was quantified in the central infarct region identified on the angiogram. RESULTS: The average Tc-99m sestamibi uptake in the central infarct region of patients with anterior infarcts and improvement of left ventricular function was significantly higher (68+/-12%, mean+/-SD) than in patients without improvement of function (40+/-14%, p < 0.02). The average Tc-99m sestamibi uptake in the central infarct region of patients with improvement of function and inferior infarcts was significantly lower (43+/-7%) than in patients with anterior infarcts (68+/-12%, p < 0.003), but was significantly higher than in patients with inferior infarction and no improvement of function (31+/-7%, p < 0.02). Using an infarct location adjusted optimal threshold (50% for anterior infarcts, 35% for inferior infarcts), Tc-99m sestamibi had a positive predictive value of 90% and a negative predictive value of 91% for improvement of left ventricular function. CONCLUSION: Quantitative rest Tc-99m sestamibi scintigraphy after oral nitrates reliably predicts improvement of left ventricular function after revascularization if infarct location adjusted thresholds are used.
OBJECTIVES: We sought to assess the feasibility and accuracy of myocardial contrast echocardiography (MCE) using standard imaging approaches for the detection of perfusion defects in patients who had a myocardial infarction (MI). BACKGROUND: Myocardial contrast echocardiography may be more versatile than perfusion scintigraphy for identifying the presence and extent of perfusion defects after MI. However, its reliability in routine practice is unclear. METHODS: Fundamental or harmonic MCE was performed with continuous or triggered imaging in 203 patients with a previous MI using bolus doses of a perfluorocarbon-filled contrast agent (NC100100). All patients underwent single-photon emission computed tomography (SPECT) after the injection of technetium-99m (Tc-99m) sestamibi at rest. Quantitative and semiquantitative SPECT, wall motion and digitized echocardiographic data were interpreted independently. The accuracy of MCE was assessed for detection of segments and patients with moderate and severe sestamibi-SPECT defects, as well as for detection of patients with extensive perfusion defects (>12% of left ventricle). RESULTS: In segments with diagnostic MCE, the segmental sensitivity ranged from 14% to 65%, and the specificity varied from 78% to 95%, depending on the dose of contrast agent. Using both segment- and patient-based analysis, the greatest accuracy and proportion of interpretable images were obtained using harmonic imaging in the triggered mode. For the detection of extensive defects, the sensitivity varied from 13% to 48%, with specificity from 63% to 100%. Harmonic imaging remained the most accurate approach. Time since MI and SPECT defect location and intensity were all determinants of the MCE response. The extent of defects on MCE was less than the extent of either abnormal wall motion or SPECT abnormalities. The combination of wall motion and MCE assessment gave the best balance of sensitivity (46% to 55%) and specificity (82% to 83%). CONCLUSIONS: Although MCE is specific, it has limited sensitivity for detection of moderate or severe perfusion defects, and it underestimates the extent of SPECT defects. The best results are obtained by integration with wall motion. More sophisticated methods of acquisition and interpretation are needed to enhance the feasibility of this technique in routine practice.