Technetium-99m Sestamibi Single-photon Emission Research Articles

Use of a New Myocardial Centroid for Measurement of Regional Myocardial Dysfunction by Electron Beam Computed Tomography

The study compared the performance of conventional endocardial and epicardial centroid algorithms with the new "myocardial" centroid algorithm in patients with anterior myocardial infarction. "Floating" endocardial or epicardial centroid algorithms, commonly used in tomographic imaging methods to assess regional motion, may misrepresent left ventricular regional myocardial function in the presence of markedly asymmetric left ventricular contraction. A new centroid algorithm based on regional myocardial mass distribution was tested in 29 patients with a first anterior myocardial infarction and was compared with conventional centroid algorithms. Direct comparisons in 60 equal sectors at one midventricular level per patient were performed between electron beam computed tomography and technetium-99m sestamibi single-photon emission computed tomography. The thresholds of regional myocardial function used to define infarction were varied for regional ejection fraction from 20% to 40% and for regional wall thickening from 0 to 4 mm. Regression and Bland-Altman analysis were used to compare infarct size by regional myocardial function with infarct size by sestamibi single-photon emission computed tomography. The new myocardial centroid showed the least shift toward infarcted myocardium from diastole to systole and had the highest amplitudes of the measurement curves for regional ejection fraction and regional wall thickening. The optimal regional myocardial function thresholds for each centroid algorithm for regional ejection fraction were endocardial, 30% (R = 0.62; mean difference to sestamibi, -0.5% +/- 22.1% tomographic infarct size points); epicardial, 30% (R = 0.79; mean difference, 2.2% +/- 13.1% tomographic infarct size points); and new myocardial, 25% (R = 0.88; mean difference, -0.6% +/- 9.5% tomographic infarct size points). The optimal thresholds for regional wall thickening were endocardial, 1 mm (R = 0.70; mean difference, -2.2% +/- 14.3% tomographic infarct size points); epicardial, 1 mm (R = 0.78; mean difference, -4.6% +/- 12.7% tomographic infarct size points); and new myocardial, 2 mm (R = 0.71; mean difference, 2.1% +/- 14.1% tomographic infarct size points). The best agreement (R = 0.88) between electron beam computed tomography infarct size and sestamibi single-photon emission computed tomography infarct size was achieved with regional ejection fraction and the new myocardial centroid algorithm. In asymmetrically contracting left ventricles, the new myocardial centroid algorithm is superior to conventional methods for tomographic analysis of regional myocardial function.

Gated SPECT after myocardial infarction: new techniques/old principles

Gated technetium-99m sestamibi single-photon emission computed tomographic (SPECT) imaging has grown rapidly over the past few years, and is now widely used for the assessment of both regional and global left ventricular function. This technique has been well validated.1,2 The incremental value of ejection fraction (EF) measurements that it provides has been clearly demonstrated in patients with chronic chest pain and suspected coronary artery disease.3 This issue of the journal contains one of the first studies of the clinical use of this technique early after myocardial infarction.4 This single-center study has several limitations. The number of patients is small (124), the number of hard events is also small (10 deaths and 10 myocardial infarctions), and many of the potentially eligible patients were not included because they underwent early revascularization after stress-gated SPECT sestamibi imaging. Because of the small number of events, the authors analyzed the combination of deaths and nonfatal myocardial infarctions. Most previous outcome studies have focused exclusively on mortality.5–8 The pathophysiology of nonfatal myocardial infarction may be considerably different.9 Despite these limitations, Kroll et al4 demonstrate that a history of prior myocardial infarction, low exercise capacity, and an EF <40% by gated SPECT imaging are all independent predictors of hard events during the 18.9 months after myocardial infarction. These novel results for this new technique reinforce several “old” established principles.

Copper-62-pyruvaldehyde bis(N4-methyl-thiosemicarbazone) PET imaging in the detection of coronary artery disease in humans

Background. Copper-62 (II)-pyruvaldehyde bis(N4-methyl-thiosemicarbazone) (PTSM) has been proposed for cardiac imaging with positron emission tomography (PET). This study evaluated the agreement between Cu-62-PTSM and coronary angiography in the detection of occlusive coronary artery disease. The normalcy rate for Cu-62-PTSM PET in a group of healthy volunteers was also assessed. Methods and Results. Forty-five subjects completed the study. Twenty-eight patients underwent stress technetium-99m sestamibi single photon emission computed tomography (SPECT) imaging and cardiac catheterization followed by Cu-62-PTSM rest/dipyridamole stress PET scans, and 17 volunteers underwent Cu-62-PTSM rest/dipyridamole stress PET scans. Cu-62-PTSM myocardial perfusion defects were identified in 100% of patients with 3-vessel disease (n = 8), 100% of patients with 2-vessel disease (n = 9), and 67% of patients with single-vessel disease (n = 6). When considering individual vessels, Cu-62-PTSM perfusion defects were seen in 72% of patients with occlusive disease in the left anterior descending artery territory, 67% in the left circumflex artery territory, and 60% in the right coronary artery territory, respectively. All 17 healthy volunteers had Cu-62-PTSM scans interpreted as normal, for a normalcy rate of 100%. Conclusions. Perfusion abnormalities are demonstrated by means of Cu-62-PTSM PET in 91% of patients with occlusive coronary artery disease seen at the time of cardiac catheterization, and it shows an excellent normalcy rate of 100%. (J Nucl Cardiol 2001;8:67-74.)

Impact of right ventricular involvement on mortality and morbidity in patients with inferior myocardial infarction

OBJECTIVESWe sought to evaluate the prognostic impact of right ventricular (RV) myocardial involvement in patients with inferior myocardial infarction (MI).BACKGROUNDThere is uncertainty regarding the risk of major complications in patients with inferior MI complicated by RV myocardial involvement. Whether these complications are related to RV myocardial involvement itself or simply to the extent of infarction involving the left ventricle (LV) is also unknown.METHODSWe examined the incidence of death and mechanical and electrical complications in patients with (n = 491) and without (n = 638) RV myocardial involvement and in patients with anterior MI (n = 971) in an analysis from the Collaborative Organization for RheothRx Evaluation (CORE) trial. Left ventricular infarct size was assessed by technetium-99m–sestamibi single-photon emission computed tomography and peak creatine kinase, and LV function was assessed by radionuclide angiography. We also performed a meta-analysis in which we pooled the results of our study with previous smaller studies addressing the same question.RESULTSSix-month mortality was 7.8% in inferior MI compared with 13.2% in anterior MI. Among patients with inferior MI, serious arrhythmias were significantly more common in patients with RV myocardial involvement who also had a trend toward higher mortality, pump failure and mechanical complications. However, this was not associated with a difference in LV infarct size or function. A meta-analysis of six studies (n = 1,198) confirmed that RV myocardial involvement was associated with an increased risk of death (odds ratio [OR] 3.2, 95% confidence interval [CI] 2.4 to 4.1), shock (OR 3.2, 95% CI 2.4 to 3.5), ventricular tachycardia or fibrillation (OR 2.7, 95% CI 2.1 to 3.5) and atrioventricular block (OR 3.4, 95% CI 2.7 to 4.2).CONCLUSIONSPatients with inferior MI who also have RV myocardial involvement are at increased risk of death, shock and arrhythmias. This increased risk is related to the presence of RV myocardial involvement itself rather than the extent of LV myocardial damage.

Shifting the open-artery hypothesis downstream: the quest for optimal reperfusion

Successful reperfusion after acute myocardial infarction (MI) has traditionally been considered to be restoration of epicardial patency, but increasing evidence suggests that disordered microvascular function and inadequate myocardial tissue perfusion are often present despite infarct vessel patency. Thus, optimal reperfusion is being redefined to include intact microvascular flow and restored myocardial perfusion, as well as sustained epicardial patency. Coronary angiography has been used as the gold standard to define failed reperfusion, according to the Thrombolysis In Myocardial Infarction (TIMI) flow grades. However, new angiographic techniques, including the corrected TIMI frame count and myocardial blush grade, have been used to show that epicardial TIMI flow grade 3 may be an incomplete measure of reperfusion success. Furthermore, evolving noninvasive diagnostic techniques, including measurement of infarct size with cardiac marker release patterns or technetium-99m–sestamibi single-photon emission computed tomographic imaging and analysis of ST segment resolution appear to be useful complements to angiography for the assessment of myocardial tissue reperfusion. Promising adjunctive therapies that target microvascular dysfunction, including platelet glycoprotein IIb/IIIa inhibitors, and agents designed to improve tissue perfusion and attenuate reperfusion injury are being evaluated to further improve clinical outcomes after acute MI. To accelerate development of these new reperfusion regimens, an integrated approach to phase II clinical trials that incorporates multiple efficacy variables, including angiography and noninvasive biomarkers of microvascular dysfunction, should be considered. Thus, as the reperfusion era moves into the next millennium, the open-artery hypothesis is expected to shift downstream and guide efforts to further improve myocardial salvage and clinical outcomes after acute MI.

Artifactual reverse distribution pattern in myocardial perfusion SPECT with technetium-99m sestamibi

Background. The reverse distribution pattern (RDP), in which resting perfusion imaging demonstrates a de novo or more marked regional defect than that present in stress images, is observed frequently in patients with a low likelihood of coronary artery disease. Methods and Results. To determine whether this scan pattern is artifactual and to investigate its causes, we retrospectively evaluated scans in 202 patients with a low likelihood of coronary artery disease (77 men and 125 women) undergoing single-day rest/stress technetium-99m sestamibi single photon emission computed tomography (SPECT). The presence and location of RDP was correlated with relevant body habitus parameters. RDP was observed in 15.3% of patients. The finding was significantly more frequent in patients who were obese (P < .02 in men,P < .03 in women), in men with abdominal protuberance (P < .05), and in women with prominent breast “shadows” observed on planar projection images (P < .008). RDP was most frequent in the right coronary artery territory in men and the left anterior descending coronary artery territory in women. It was demonstrated by means of a cardiac SPECT phantom experiment that soft tissue attenuation effects were most evident in low count density SPECT studies with localized soft tissue attenuation, accounting for the higher than clinical observation of RDP in obese patients undergoing low-dose rest/high-dose imaging. Conclusions. RDP is a frequently encountered artifact in obese patients undergoing rest/stress Tc-99m sestamibi SPECT, particularly in men with abdominal protuberance and in women with large, dense breasts. (J Nucl Cardiol 2000;7:633-8.)

Impact of an abbreviated adenosine protocol incorporating adjunctive treadmill exercise on adverse effects and image quality in patients undergoing stress myocardial perfusion imaging

Background. Limited data are available about the effects of adjunctive treadmill exercise on adverse effects and the image quality of adenosine perfusion imaging. This study compared the incidence of adverse effects and image quality between standard 6-minute adenosine perfusion imaging and a stress test incorporating a 4-minute adenosine infusion with low-level treadmill exercise. Methods and Results. Nineteen patients underwent both a 6-minute adenosine technetium-99m sestamibi single photon emission computed tomography (SPECT) imaging study and a 4-minute adenosine Tc-99m sestamibi SPECT study with 6 minutes of simultaneous low-level treadmill exercise. Symptoms were recorded at 1-minute intervals during the stress and recovery periods. Heart-to-liver and heart-to-lung count ratios were determined from anterior planar images. More adverse effects were experienced during the standard adenosine study than during the adenosine study with low-level exercise (2.7 ± 1.4 vs 1.4 ± 1.1,P = .0003). The duration adverse effects were experienced was longer during the standard 6-minute adenosine protocol (6.6 ± 2.1 minutes vs 3.2 ± 2.8 minutes,P < .0001). Additionally, the symptom-severity scores were higher with the standard adenosine study (15.5 ± 9.8 vs 4.5 ± 5.1, P < .0001). The heart-to-liver ratios were noted to be higher in the 4-minute adenosine protocol with low-level exercise (1.0 ± 0.3 vs 0.6 ± 0.2, P = .0003). Conclusions. In comparison with standard 6-minute adenosine perfusion imaging, a protocol incorporating a 4-minute adenosine infusion with low-level treadmill exercise results in a marked reduction in the quantity and severity of adverse effects and an improvement in image quality. (J Nucl Cardiol 2000;7:584-9.)

Comparison of baseline and low-dose dobutamine technetium-99m sestamibi scintigraphy with low-dose dobutamine echocardiography for predicting functional recovery after revascularization

Injection of sestamibi during low-dose dobutamine (LDD) infusion might improve tracer ability to detect viable myocardium. This study investigated the potential value of LDD technetium-99m sestamibi (sestamibi) single-photon emission computed tomography (SPECT) in predicting functional recovery after revascularization by comparing its results with those of sestamibi SPECT at rest and of LDD echocardiography. Before revascularization, 23 patients with chronic coronary artery disease and regional left ventricular dysfunction underwent sestamibi SPECT at rest and, on a separate day, LDD echocardiography and sestamibi SPECT with tracer injection during LDD infusion. Echocardiography at rest was repeated after revascularization. Semiquantitative sestamibi uptake results (grading from 0 = normal to 4 = absent) and wall motion (grading from 1 = normal to 4 = dyskinesia) were evaluated with a 16-segment model. The ventricular wall was divided into 3 vascular territories. At follow-up, 20 of 32 asynergic vascular territories showed functional recovery, whereas 12 showed no changes. For prediction of functional recovery, LDD SPECT achieved better accuracy than SPECT at rest (87% vs 65%, p <0.05); positive and negative predictive values of LDD SPECT were 90% and 83%, respectively, which was not significantly different from the related LDD echocardiographic values (84% and 69%). Thus, LDD sestamibi SPECT appears to be a promising method for detecting myocardial viability, which provides better accuracy than sestamibi SPECT at rest, and achieves predictive values comparable to those of LDD echocardiography.

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 disese and left ventricular dysfunction (ejection fraction ≤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% (κ 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.

Assessment of left ventricular function by ECG-gated myocardial perfusion scintigraphy with image inversion technique: Comparison with equilibrium radionuclide angiography

Background. Inversion of gated myocardial perfusion imaging has been proposed for the evaluation of left ventricular function. This study compared the results of inversion technique of gated left anterior oblique 45° images (G-LAO 45°) with those provided by equilibrium radionuclide angiography in the assessment of global left ventricular function in the same patients with suspected or known coronary artery disease. Methods and Results A total of 107 patients (85 men and 22 women, mean age 59 ± 9 years) with suspected or documented coronary artery disease were studied. Eighty-seven underwent a 2-day stress/rest technetium-99m sestamibi single photon emission computed tomography with acquisition of G-LAO 45° images on the day of rest, and 20 underwent thallium-201 stress/redistribution single photon emission computed tomography with G-LAO 45° image acquisition immediately after redistribution imaging. An excellent correlation ( P < .001) with no significant differences was found between left ventricular ejection fraction values provided by inversion G-LAO 45° and radionuclide angiography in 87 patients studied with Tc-99m sestamibi and 20 patients studied with Tl-201. The Bland-Altman analysis demonstrated the difference in absolute ejection fraction values obtained by inversion G-LAO 45° images and radionuclide angiography as <8%. The inversion G-LAO 45° left ventricular ejection fraction distinguishes the patients with myocardial infarction (ejection fraction = 43% ± 13%) and without myocardial infarction (ejection fraction = 60% ± 5%) ( P < .001). In patients with left ventricular ejection fraction <40%, inversion G-LAO 45° images provide evaluation of left ventricular function comparable with that obtained by RNA. Conclusions. Semiautomated myocardial perfusion gated inversion technique analyzed with a count-based method is useful in the evaluation of left ventricular function and provides similar results to those of radionuclide angiography.

Complications of exercise and pharmacologic stress tests: Differences in younger and elderly patients

Background. Age characteristics of patients undergoing various types of stress tests are important because of differences in clinical background and exercise performance between the young and elderly. Adverse effects of pharmacologic agents are known to be more common in the elderly, who are less able to perform vigorous exercise stress testing. We investigated the clinical background, performance characteristics, and complication rate of various stress tests in younger (≤75 years old) and elderly (>75 years old) patient populations. Methods. A total of 3412 patients (2796 younger, 616 elderly) underwent 5 types of stress tests with (1) technetium-99m sestamibi (MIBI) single photon emission computed tomography: symptom-limited exercise (Ex, 1598 younger, 173 elderly), (2) dipyridamole infusion (0.14 mg/kg/min, 4 minutes) without exercise (D, 260 younger, 114 elderly), (3) with exercise (DEx, 339 younger, 112 elderly), (4) adenosine infusion (0.14 mg/kg/min, 5 minutes) without exercise (A, 253 younger, 101 elderly), and (5) with exercise (AEx, 346 younger, 116 elderly). Results. Sixty-seven percent of patients in the younger population were able to achieve 85% of the maximum predicted heart rate, whereas 54% of the elderly reached this level of exercise. No patient had life-threatening complications. In both the younger and elderly groups, chest discomfort, feelings of impending syncope, flushing, and fall in blood pressure occurred less frequently in DEx than D and in AEx than A. Sinus bradycardia occurred less frequently in AEx than A in the younger (1.2% vs 4.3%, P < .05) and elderly groups (0.9% vs 6.9%, P < .05). Atrioventricular block was less frequent in AEx than A in the younger group (3.2% vs 7.9%, P < .05) but not so in the elderly group (13.0% vs 17.8%, not significant). The frequency of ischemic electrocardiographic changes in DEx and AEx was very similar to that of Ex in both the younger and elderly groups, although ischemic electrocardiographic changes in D and A are known to be less frequent. Conclusion. Of the elderly group who were judged to be fit to exercise to 85% of maximum predicted heart rate, nearly half failed to reach this level. In contrast, the younger patients were able to achieve this level in 67% of tests. Supplementation with modest exercise reduced most of the pharmacologically related adverse effects. The elderly group was not protected from atrioventricular block as effectively as the younger group by additional exercise in the adenosine stress test. Ischemic electrocardiographic changes in the pharmacologic stress test were as frequent as in the exercise stress test when modest supplementary exercise was added to the pharmacologic protocol. There were no deaths, myocardial infarction, or other major complications. These observations suggest that exercise and pharmacologic stress tests are safe in the elderly, including those patients more than 75 years old.

Impact of limited treadmill exercise on adenosine Tc-99m sestamibi single-photon emission computed tomographic myocardial perfusion imaging in coronary artery disease

Limited exercise combined with dipyridamole increases myocardial perfusion defect severity compared with dipyridamole alone. The impact of limited exercise combined with adenosine on myocardial perfusion defect severity is unknown. This study compares myocardial perfusion defect severity with adenosine alone and adenosine combined with limited exercise. Thirty-two patients with coronary artery disease underwent on separate days and in randomized order technetium-99m sestamibi (25 to 30 mCi) single-photon emission computed tomographic imaging at rest, after adenosine (140 μg/kg/min × 6 minutes), and after adenosine (140 μg/kg/min × 4 minutes) during 6 minutes of modified Bruce treadmill exercise (adenosine-exercise). Radiopharmaceutical was injected at 3 and 5 minutes during adenosine and adenosine-exercise, respectively. Images were interpreted by a consensus agreement of 3 nuclear cardiologists without knowledge of patient identity, stress protocol, or clinical data using a 17-segment model and 5-point scoring system. A summed stress score (SSS), summed rest score (SRS), and summed difference (SSS-SRS) score (SDS) were calculated for each image. Peak stress heart rate and rate-pressure product were higher for adenosine-exercise than adenosine (102 ± 19 vs 81 ± 11 beats/min and 13,972 ± 4,265 vs 10,623 ± 2,131, respectively; both p <0.001). Sensitivity for detection of ≥50% coronary stenosis was 75% and 72% for adenosine-exercise and adenosine, respectively (p = NS). There were no differences in SSS and SDS between adenosine-exercise and adenosine (8.2 ± 5.9 vs 8.1 ± 6.3 and 4.9 ± 4.1 vs 5.2 ± 4.6, respectively; both p = NS). Thus, in patients with coronary artery disease, limited treadmill exercise combined with adenosine does not increase myocardial perfusion defect severity compared with standard adenosine technetium-99m sestamibi single-photon emission computed tomographic myocardial perfusion imaging.

Technetium-99m sestamibi single-photon emission tomography detects subclinical myocardial perfusion abnormalities in patients with systemic lupus erythematosus.

In patients with systemic lupus erythematosus, involvement of the cardiovascular system is the third leading cause of death. However, although autopsy studies have demonstrated a high incidence of abnormalities in both the myocardium and coronary vessels, clinical manifestations have been reported in only a small percentage of cases. The aim of this study was to evaluate myocardial perfusion in asymptomatic lupus patients using technetium-99m sestamibi single-photon emission tomography (SPET). Twenty-eight patients without overt cardiac involvement and risk factors were studied with 99mTc-sestamibi SPET at rest and after dipyridamole infusion. Perfusion abnormalities were detected in 18 cases: six had persistent defects, three had reversible defects, seven had both persistent and reversible defects, and two showed rest defects which normalized on dipyridamole images ("reverse redistribution pattern"). Coronary angiography was performed in eight patients with positive 99mTc-sestamibi SPET, and showed normal epicardial vessels in all the cases. These results indicate that 99mTc-sestamibi SPET reveals a high prevalence (18 out of 28 patients in this study, i.e. 64%) of myocardial perfusion abnormalities in asymptomatic lupus patients, probably due to the primary immunological damage of this autoimmune disease. In conclusion, rest/dipyridamole 99mTc-sestamibi SPET can be a useful non-invasive method to identify subclinical myocardial involvement in systemic lupus erythematosus, and patients potentially at risk of later cardiac events.

The prognostic value of a normal Tc-99m sestamibi SPECT study in suspected coronary artery disease

Background. Myocardial perfusion is widely used for risk stratification of patients with suspected or known coronary artery disease (CAD). Recent years have seen an increasing demand for screening of such patients. The value of a normal stress thallium-201 scanning is well established. The advent of technetium 99m-sestamibi single photon emission computed tomography (SPECT) has enhanced the profile of nuclear cardiology even further as a reliable test for screening. However, in spite of previous reports, there is paucity of large-scale data regarding the prognostic value of a normal Tc 99m-sestamibi scanning result. Methods. The aim of our study was to assess the incidence of cardiac death and non-fatal myocardial infarction in patients with an intermediate probability of coronary artery disease (CAD). A total of 473 patients with normal stress Tc-99m-sestamibi SPECT were monitored for 30 ± 16 (6 to 56) months to assess serious cardiac events. There were 272 men and 201 women, with a mean age of 56 ± 2 years, of whom 89% had symptoms suggestive of CAD, 65% had an abnormal exercise electrocardiography, 6% had known CAD, and 5% had a high risk of CAD. The average workload was 9.14 metabolic equivalents, peak exercise heart rate was 93% ± 13% of the age predicted target. Results. The annualized mortality rate was 0.2% (95% CI 0.02% to 0.7%) and no infarctions occurred in this group. Conclusions. A normal stress Tc-99m-sestamibi is highly predictive of a benign outcome, even in patients with intermediate probability of CAD.

Dipyridamole-dobutamine stress with Tc-99m sestamibi tomographic myocardial perfusion imaging

In 66 patients unable to exercise referred for pharmacologic stress single-photon emission computed tomographic myocardial perfusion imaging, a moderate dose of dobutamine was combined with intravenous dipyridamole and the results were compared with standard intravenous dipyridamole stress. The combined stress protocol resulted in increased defect size and reversibility with technetium-99m sestamibi single-photon emission computed tomographic myocardial perfusion imaging.

Risk stratification with pre–hospital discharge exercise technetium-99m sestamibi myocardial tomography in men after acute myocardial infarction

Background Exercise thallium-201 imaging early after acute myocardial infarction (MI) may provide information concerning risk of future cardiac events. The prognostic value of exercise technetium-99m sestamibi (MIBI) single-photon emission computed tomography in such patients has not been established. Methods and Results Submaximal exercise stress testing with MIBI tomography was done before hospital discharge in 134 consecutive men after acute MI. Patients were monitored for occurrence of late cardiac events (nonfatal MI or cardiac death). Coronary revascularization was done in 31 patients (23%) ≤3 months after testing. Nonfatal MI or cardiac death occurred in 30 (23%) of the overall group of 133 patients monitored (mean 35 ± 19 months) and in 25 (25%) of the 102 patients treated medically. A history of congestive heart failure, failure to reach 85% of age-predicted maximal heart rate, and an isolated fixed MIBI defect were associated with significantly increased risk ( p < 0.05) of a late cardiac event in both groups of patients. A reversible MIBI defect was not associated with increased risk. In a multivariable Cox proportional hazards model, only a history of congestive heart failure (relative risk 4.2, 95% confidence interval [CI] 1.7 to 10.4, p < 0.002) and an isolated fixed MIBI defect (relative risk 2.1, 95% CI 1.1 to 4.3, p < 0.05) were independent predictors of increased risk in the total group of 133 patients. In the 102 patients treated medically, only a history of congestive heart failure (relative risk 4.9, 95% CI 1.9 to 13.1) and achievement of 85% of age-predicted maximal heart rate (relative risk 0.13, 95% CI 0.02 to 0.9) were independent predictors of risk. Conclusions Early post-MI submaximal exercise testing with MIBI tomography provides limited prognostic information for late cardiac events. An isolated fixed MIBI defect is associated with increased risk but not as strongly as other variables, particularly a history of congestive heart failure. (Am Heart J 1998;136:87-93.)

Detection of Coronary Vasospasm by Posthyperventilation Technetium-99m Sestamibi Single-Photon Emission Computed Tomography Imaging in Patients With Coronary Artery Disease

Forced hyperventilation is simple, safe to perform, and can be used as a provocative test for coronary vasospasm. This study assesses whether a vasospastic component of angina might be detected in patients with angiographically “nonobstructive” coronary artery disease by posthyperventilation technetium-99m (Tc-99m) sestamibi single-photon emission computed tomography (SPECT) cardiac imaging. Eleven patients with angiographically nonobstructive coronary artery disease underwent Tc-99m sestamibi SPECT imaging at rest and after forced hyperventilation. Vessel diameters were measured by quantitative angiography before and after forced hyperventilation, and posthyperventilation SPECT images were compared with dipyridamole Tc-99m sestamibi stress images. Forced hyperventilation resulted in a 15% reduction in coronary artery diameter in stenotic segments (p <0.01), and a 17% reduction in adjacent nonstenotic segments (p <0.001). Myocardial uptake of Tc-99m sestamibi in segments perfused by vessels with angiographically nonobstructive stenoses was reduced by 24% following forced hyperventilation (p <0.001) compared with only 4% following dipyridamole (p <0.02). These findings suggest that posthyperventilation Tc-99m sestamibi SPECT imaging in patients with angina pectoris and nonobstructive coronary artery disease may be useful in identifying a vasospastic component of angina.

The role of technetium-99m sestamibi single photon emission tomography in the follow-up of malignant melanoma and the detection of lymph node metastases.

In the follow-up of patients with malignant melanoma treated by surgical resection of the cutaneous tumour, it is important to achieve early detection of possible lymph node metastasis. In many cases, clinical examination alone will not be sufficient. In our study, single-photon emission tomography (SPET) with technetium-99m sestamibi (MIBI) was used in the assessment of 30 patients with previously resected malignant melanoma when the clinical examination raised the suspicion of lymph node metastasis. Using MIBI, 16 out of 17 lymph node metastases were detected and confirmed by histology. No false-positive results were obtained during this prospective study. It is concluded that MIBI scintigraphy may be useful in the early detection of lymph node metastases of malignant melanomas. If our preliminary results are confirmed, early detection of lymph node metastasis of previously resected malignant melanoma by 99mTc-MIBI scintigraphy may have a significant impact on the management of these patients.

Value of Gating of Technetium-99m Sestamibi Single-Photon Emission Computed Tomographic Imaging

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 ≤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 ≥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.

Effect of ST segment measurement point on performance of exercise ECG analysis

To evaluate the effect of ST-segment measurement point on diagnostic performance of the ST-segment/heart rate (ST/HR) hysteresis, the ST/HR index, and the end-exercise ST-segment depression in the detection of coronary artery disease, we analysed the exercise electrocardiograms of 347 patients using ST-segment depression measured at 0, 20, 40, 60 and 80 ms after the J-point. Of these patients, 127 had and 13 had no significant coronary artery disease according to angiography, 18 had no myocardial perfusion defect according to technetium-99m sestamibi single-photon emission computed tomography, and 189 were clinically `normal' having low likelihood of coronary artery disease. Comparison of areas under the receiver operating characteristic curves showed that the discriminative capacity of the above diagnostic variables improved systematically up to the ST-segment measurement point of 60 ms after the J-point. As compared to analysis at the J-point (0 ms), the areas based on the 60-ms point were 89 vs. 84% ( p=0.0001) for the ST/HR hysteresis, 83 vs. 76% ( p<0.0001) for the ST/HR index, and 76 vs. 61% ( p<0.0001) for the end-exercise ST depression. These findings suggest that the ST-segment measurement at 60 ms after the J-point is the most reasonable point of choice in terms of discriminative capacity of both the simple and the heart rate-adjusted indices of ST depression. Moreover, the ST/HR hysteresis had the best discriminative capacity independently of the ST-segment measurement point, the observation thus giving further support to clinical utility of this new method in the detection of coronary artery disease.