The occurrence of false-positive technetium-99m sestamibi bull's eye defects in different reference databases

Myocardial perfusion single-photon emission tomographic (SPET) imaging has been shown to be sensitive in the detection of coronary artery disease (CAD), whereas its specificity has been suboptimal. The aim of the present study was to study the frequency of abnormal bull's eye perfusion defects in a large age-stratified group of healthy subjects undergoing myocardial SPET assessed by comparison with two existing commercially available reference databases. One hundred and twenty-eight healthy volunteers (76 males and 52 females) with a less than 5% likelihood of CAD underwent rest and exercise technetium-99m sestamibi SPET. The false-positive response rate, defined as a significant reversible defect, was 12% when compared to the CEqual database and 29% when compared to the Cedars-Sinai database. With the CEqual program, rest defects occurred in 12% of the subjects. Defects occurred more often in women than in men, but the difference did not attain statistical significance. Significant defects were most frequent in the inferior wall and in women in the anterior wall as well. The distribution of defects was independent of age. Our results suggest that the specificity of^99mTc-sestamibi myocardial SPET using commercially available reference files is suboptimal. The risk of obtaining a falsepositive test result in subjects undergoing^99mTc-sestamibi myocardial SPET with a very low likelihood of CAD was higher than anticipated. With both reference files false-positive test results were most frequently observed in the inferior wall. Our data suggest that commercial reference files for myocardial SPET need to be optimised, and should be used with caution. The use of attenuation correction may prove to be a major step forward.     

Technetium-99m sestamibi imaging to predict left ventricular ejection fraction outcome after revascularisation in patients with chronic coronary artery disease and left ventricular dysfunction: comparison between baseline and nitrate-enhanced imaging

Acceptance of technetium-99m sestamibi as a tracer of myocardial viability is growing, particularly when nitrate-enhanced imaging is used. However, few data are available on the ability of ^99mTc-sestamibi to predict the evolution of global left ventricular ejection fraction (EF). The aim of this study was to examine the ability of resting and nitrate ^99mTc-sestamibi single-photon emission tomography (SPET) to predict EF changes after revascularisation in patients who have chronic coronary artery disease with left ventricular dysfunction. Using baseline resting and nitrate ^99mTc-sestamibi SPET, we studied 61 patients scheduled for revascularisation because of left ventricular dysfunction. EF was estimated using two-dimensional echocardiography before and after the intervention. A post-revascularisation improvement of ̓ EF units was defined as significant. Using a 13-segment model, ^99mTc-sestamibi activity was quantified and the nitrate-induced activity changes calculated. Three different criteria for detecting viability (defined as post-revascularisation reversible dysfunction) in asynergic segments were compared: (1) resting ^99mTc-sestamibi activity ₨%; (2) nitrate ^99mTc-sestamibi activity ₭%; and (3) nitrate-induced increase >+10% or nitrate-induced increase h+10% and nitrate activity ₭%. EF increased significantly in 32 patients. The number of viable asynergic segments was significantly higher in these patients than in the remaining 29 subjects, and the difference was greater (P<0.0002) using definition (3) than using either baseline (P<0.002) or nitrate activity (P<0.0005). There was a significant relationship between EF changes and number of viable asynergic segments: Spearman R=0.38, P<0.005 using baseline; Spearman R=0.39, P<0.002 using nitrate activity; and Spearman R=0.55, P<0.000005 using definition (3). According to receiver operating characteristic (ROC) curve analysis, this last criterion achieved the best results (81% sensitivity, 69% specificity and 75% accuracy), with an area under the ROC curve of 0.838; this area was significantly larger than when using either baseline (0.744, P<0.02) or nitrate activity (0.747, P<0.005). ^99mTc-sestamibi SPET appears able to predict the evolution of global left ventricular EF after revascularisation, thereby confirming the value of ^99mTc-sestamibi as a tracer of myocardial viability. The combination of baseline resting and nitrate imaging seems to significantly improve the diagnostic accuracy of ^99mTc-sestamibi SPET for this particular purpose.     

Detection of coronary artery disease by dynamic planar and single photon emission tomographic imaging with technetium-99m teboroxime

To test the clinical significance of technetium-99m teboroxime regional myocardial clearance in the detection of coronary artery disease, 25 patients underwent dynamic planar or single-photon emission tomographic (SPET) myocardial imaging with ^99mTc-teboroxime after exercise and again 2 h later at rest. All patients underwent both thallium-201 exercise and redistribution SPET and coronary arteriography. The early phases of exercise ^99mTc-teboroxime myocardial clearance determined by dynamic planar imaging showed a significant difference between normal and post-stenotic myocardial regions (clearance rate constant k: 0.047±0.005 min' versus 0.034±0.003 min^–1, P <0.001). Reflecting this differential clearance between myocardial regions, an early redistribution-like phenomenon was observed in a significant number of myocaridal segments by comparing serially acquired post-exercise ^99mTc-teboroxime SPET images. These results indicated that the analysis of ^99mTc-teboroxime myocardial clearance was of potential use in the detection of coronary artery disease, yielding additional information to that provided by the tracer distribution analysis. Although the early redistribution-like phenomenon of ^99mTc-teboroxime could be the source of underestimation of ischaemia if acquisition of the initial post-exercise image were delayed, it could also prove useful in the early differentiation of ischaemia from scar because when the phenomenon was observed in delayed post-exercise images, the rest study could be omitted under some circumstances.     

Amplitude analysis of stress technetium-99m methoxy isobutylisonitrile images in coronary artery disease

To determine the role of rest and stress gated technetium-99m methoxyisobutylisonitrile (sestamibi), in the detection of coronary artery disease, routine Fourier analysis of these images was performed with the best septal left anterior oblique (LAO) position of 20 patients (17 men, 3 women; aged 40–75 years) who also underwent rest or redistribution/stress single photon emission tomography (SPET) (^99mTc-sestamibi and Thallium-201), gated blood pool imaging and coronary angiogram. There were 6 patients with single-vessel disease, 6 with two-vessel disease, 4 with three-vessel disease, 2 with coronary spasms, 1 with a patent graft and 1 with anginal episodes but a normal angiogram result. Three normal volunteers (2 women, 1 man; aged 24–26 years) also had rest and stress gated blood pool as well as rest and stress gated ^99mTc-sestamibi imaging. Rest and stress ^99mTc-ses-tamibi amplitude and phase images depicted regional myocardial wall shortening from the outer layer of the myocardium to the center of the left ventricle as follows a high amplitude halo of maximal negative count rate variaton; a circular thinner halo of negligible amplitude; a central region of maximal positive count rate variation, as the images evolved from end-diastole to end-systole. Similar patterns with regional differences represented abnormal myocardial wall shortening. (^99mTc-sestamibi and ²⁰¹T1 SPET) images were in agreement in 90% of the patients and 92% of myocardial regions. ²⁰¹T1 SPET detected 83% of angiographically proven lesions, as compared with 80% for ^99mTc-setamibi SPET and 80% for the amplitude images. The amplitude images demonstrated a larger number of other abnormalities not predicted on the angiogram, probably because they were able to detect regions with a potential for flow improvement and transient regional wall shortening abnormalities. Amplitude and phase analyses of gated rest and stress ^99mTc-ses-tamibi images are easy to perform and may become an important adjunct to (^99mTc-sestamibi SPET) images for a complete evaluation of both regional myocardial perfusion and regional contractile function using a single tracer. Offprint requests to: E.E. Camargo     

Comparison of technetium-99m sestamibi left ventricular wall motion and perfusion studies with thallium-201 perfusion imaging: in search of the combination of variables with the highest accuracy in predicting coronary artery disease

Measurements of myocardial perfusion and ventricular function are expected to provide additional information in the detection of coronary artery disease (CAD). The purpose of this study was threefold: (1) to determine to what extent technetium-99m sestamibi wall motion yields different information compared with^99mTc-sestamibi and thallium-201 perfusion; (2) to test which information unique to either study is of value in diagnosing CAD; and (3) to assess the combination of variables with the highest diagnostic accuracy. Perfusion and wall motion scores (at rest and during exercise) obtained from visual and quantitative planar²⁰¹T1 and^99mTc-sestamibi scintigraphy of 60 patients with suspected CAD were compared with the angiographic results by means of a polytomous logistic regression model and the diagnostic values were compared with one another. All univariate variables were significantly related to the probability of CAD and its extent. Comparative studies revealed a large degree of correlation between²⁰¹T1 stress and redistribution variables. The rest^99mTc-sestamibi and wall motion studies contained partially different information. Stepwise logistic regression analysis showed the strongest diagnostic power for the combination of²⁰¹Tl visual analysis of the stress images with quantitative redistribution images (sensitivity 93%, specificity 71%). The diagnostic power was similar for all combinations of visual and quantitative analyses of the exercise and redistribution images. The strongest diagnostic power of the^99mTc-sestamibi variables was the score of the diastolic stress image (sensitivity 91%, specificity 79%). Comparable sensitivity and specificity estimates were found when both optimal models were compared. Wall motion studies did not have additional diagnostic power. Although^99mTc-sestamibi wall motion studies, both at rest and during exercise, provide information in addition to the^99mTc-sestamibi or²⁰¹Tl myocardial perfusion variables, the information does not enhance the diagnostic power with regard to the prediction of CAD.     

15-Year outcome after normal exercise 99mTc-sestamibi myocardial perfusion imaging: What is the duration of low risk after a normal scan?

Objective

The goal of this study was to evaluate the very long-term outcome after normal exercise ^99mTc-sestamibi myocardial perfusion single-photon emission computed tomography (SPECT). Exercise ^99mTc-sestamibi SPECT is widely used for risk stratification, but data on very long-term outcome after a normal test are scarce.

Methods

A consecutive group of 233 patients (122 men, mean age 54?±?12?years) with known or suspected coronary artery disease (CAD) underwent exercise ^99mTc-sestamibi SPECT and had normal myocardial perfusion at exercise and at rest. Follow-up endpoints were all-cause mortality, cardiac mortality, nonfatal myocardial infarction, and coronary revascularization. Predictors of outcome were identified by Cox proportional hazard regression models using clinical and exercise testing variables.

Results

During a mean follow-up of 15.5?±?4.9?years, 41 (18%) patients died, of which 13 were cardiac deaths. A total of 18 (8%) patients had a nonfatal myocardial infarction, and 47 (20%) had coronary revascularization. The annualized event rates for all-cause mortality, cardiac mortality, cardiac mortality/nonfatal infarction, and major adverse cardiac events were, respectively, 1.1%, 0.3%, 0.7%, and 1.8%. Multivariate analysis demonstrated that the variables age, male gender, diabetes, diastolic blood pressure at rest, rate pressure product at rest, peak exercise heart rate, and ST segment changes were independent predictors of major adverse cardiac events.

Conclusion

Patients with suspected or known CAD and normal exercise ^99mTc-sestamibi myocardial perfusion SPECT have a favorable 15-year prognosis. Follow-up should be closer in patients with known CAD, and/or having clinical and exercise parameters indicating higher risk status.     

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. Received 20 November 1998 and in revised form 19 February 1999     

Diagnostic efficacy of stress technetium 99m-labeled sestamibi myocardial perfusion single-photon emission computed tomography in detection of coronary artery disease among patients over age 80

Background

Because symptoms of myocardial ischemia in elderly patients are often atypical, accurate noninvasive assessment of the presence, extent, and severity of coronary artery disease (CAD) would be especially useful to avoid unnecessary catheterization or invasive intervention. This study assessed the safety and diagnostic efficacy of ^99mTc-labeled sestamibi (^99mTcsestamibi) exercise and pharmacologic myocardial perfusion single-photon emission computed tomography (SPECT) with adenosine or dipyridamole in patients age 80 years or older.

Methods and Results

Stress ^99mTc-sestamibi SPECT was performed in 75 consecutive patients who were 80 years old or older (range: 80 to 91 years) with suspected CAD and who underwent coronary angiography within 6 months of the nuclear study. Of these patients, 51 underwent a pharmacologic (adenosine=42; dipyridamole=9) stress study and 24 underwent an exercise treadmill study. A normalcy rate was derived from an additional 36 patients (ages 83±3 years) who had undergone stress ^99mTc-sestamibi SPECT and who had a relatively low likelihood (<20%) of CAD. No serious adverse events occurred during or after the exercise or the pharmacologic stress test. The overall sensitivity and specificity for detecting CAD with ≥70% stenosis was 95% (52/55) and 75% (15/20), whereas the corresponding results were 87% (55/63) and 83% (10/12) for detecting patients with ≥50% stenosis. The sensitivity and specificity for pharmacologic stress ^99mTc-sestamibi SPECT were 95% (35/37) and 71% (10/14) for detecting ≥70% stenosis, and 86% (37/43) and 75% (6/8) for detecting CAD with ≥50% stenosis. The sensitivity and specificity of treadmill testing were 94% (17/18) and 83% (5/6) in detecting CAD with stenosis ≥70% and 90% (18/20) and 100% (4/4) in detecting CAD with stenosis ≥50%. The normalcy rate among the low likelihood patients was 83% (30/36). The accuracy of stress sestamibi testing was similar for patients with or without angina.

Conclusions

Our findings suggest that exercise or pharmacologic myocardial perfusion SPECT with ^99mTc-sestamibi is safe and diagnostically accurate for CAD detection in very elderly patients, irrespective of symptoms. Pharmacologic myocardial perfusion SPECT with adenosine or dipyridamole appears to be a valuable alternative to treadmill stress in very elderly patients incapable of performing adequate exercise.     

Comparison and histopathological correlation of three parathyroid imaging methods in a population with a high prevalence of concomitant thyroid diseases

The aim of this prospective study was to evaluate the diagnostic utility of a technetium-99m sestamibi dual-phase protocol enhanced by single-photon emission tomography (SPET) and semiquantitative analysis in comparison to established preoperative staging procedures in patients with primary hyperparathyroidism. Twenty-eight (50%) out of 56 patients had superimposed thyroid disease, and 12 patients had previously undergone neck surgery. Visual and semiquantitative analysis of planar^99mTc-sestamibi dual-phase imaging, SPET of the delayed phase, ultrasonography, and thallium-201 chloride-technetium-99m pertechnetate subtraction scintigraphy was further correlated with the histopathological examination of the surgical specimens.^99mTc-sestamibi dual-phase imaging achieved the highest sensitivity for side localization and precise localization compared with²⁰¹Tl-^99mTc subtraction scintigraphy and ultrasonography, but the differences reached statistical significance only in comparison to ultrasonography. Semiquantitative analysis did not enhance sensitivity. Adenoma detection by^99mTc-sestamibi dual-phase imaging was only correlated to serum calcium levels and osteocalcin, not to cell density or oxyphil cell count (SPET yielded additional information for the exact topographical localization of the parathyroid tumour in 22 (39%) patients with superimposed thyroid disease or previous neck surgery but did not enhance the overall detection rate.     

One-year prognosis of patients with normal planar or single-photon emission computed tomographic technetium 99m-labeled sestamibi exercise imaging

Background.

The favorable prognostic significance of normal²⁰¹Tl stress perfusion images, even in the presence of known coronary artery disease, has been well documented. Relatively few data are available with regard to the prognostic significance of normal planar and single-photon emission computed tomographic (SPECT) stress^99mTc-labeled sestamibi (^99mTc-sestamibi) images.

Methods and Results.

The prognostic significance of normal exercise^99mTc-sestamibi myocardial perfusion imaging was evaluated in 208 consecutive patients. All patients were referred for evaluation of chest pain syndrome. One hundred eight patients (52%) underwent SPECT imaging, 79 patients (38%) underwent planar imaging, and 21 patients (10%) underwent both planar and SPECT imaging. One hundred seventy-five patients (84%) had a normal or nondiagnostic exercise electrocardiogram, and 33 patients (16%) had a positive exercise electrocardiogram. Follow-up was 13.5 ±2 months and was complete in 99.5% of patients. No patient died of cardiac causes during follow-up. One patient (0.5%) had a nonfatal myocardial infarction and four patients (2%) had unstable angina necessitating revascularization. There was no difference in rate of cardiac events between men and women or whether SPECT or planar imaging was used. However, 33 patients with normal^99mTc-sestamibi imaging and a positive exercise electrocardiogram had a significantly higher cardiac event rate than had patients with negative exercise electrocardiograms (9% vs 1%,p < 0.025).

Conclusion

Patients with normal^99mTc-sestamibi exercise SPECT or planar imaging results and a normal or nondiagnostic exercise electrocardiogram have a favorable 1-year prognosis. Patients with normal^99mTc-sestamibi images and a positive stress electrocardiogram have a less favorable outcome.     

Impaired myocardial fatty acid metabolism detected by123I-BMIPP in patients with unstable angina pectoris: Comparison with perfusion imaging by99mTc-sestamibi

The present study was undertaken to determine the potential diagnostic value of¹²³I-BMIPP scintigraphy for the detection of altered myocardial fatty acid metabolism in patients with unstable angina. Both myocardial metabolic imaging with¹²³I-BMIPP and perfusion imaging with^99mTcsestamibi were performed at rest in 28 patients with unstable angina in the pain-free state. The regional uptakes of¹²³I-BMIPP or^99mTc-sestamibi were scored semiquantitatively (0 = normal, 4 = no activity) and compared with the coronary arteriographic findings. Decreased uptakes of¹²³I-BMIPP were observed in 18 patients, and 11 patients had abnormal^99mTc-sestamibi images. Defect scores of¹²³I-BMIPP were larger than those of^99mTc-sestamibi (7.8 ± 2.1 vs. 5.2 + 1.9, p < 0.01). The sensitivity for the detection of patients with unstable angina was higher in¹²³I-BMIPP than in^99mTc-sestamibi (77% vs. 45%, p < 0.01). The site of the decreased¹²³I-BMIPP uptake corresponded to the most stenotic coronary artery lesion in all patients. Fatty acid metabolic imaging with¹²³I-BMIPP was more sensitive for detecting myocardial ischemia than perfusion imaging with^99mTc-sestamibi.¹²³I-BMIPP may be a clue to define the culprit lesion in unstable angina and be helpful to decide the best treatment and guide coronary angioplasty.     

Myocardial sestamibi single-photon emission tomography: Variations in reference values with gender, age and rest versus stress?

Reference data files support the evaluation of myocardial perfusion single-photon emission tomography (SPET). The aim of this study was to create a large reference data base for technetium-99m sestamibi SPET, age and gender matched to the general patient population. One hundred and twenty-eight healthy volunteers (76 males and 52 females) with a likelihood of coronary artery disease of less than 5% underwent rest and maximal exercise^99mTc-sestamibi SPET with a 2-day protocol and 180° elliptical rotation. The normalized activity values of^99mTc-sestamibi in the inferior wall differed significantly between men and women. Age variations were found for men in the anterior wall. Normalized activity values in all four walls were strikingly similar during rest and stress. Our results suggest that the use of reference files in^99mTc-sestamibi SPET requires a gender- and, for males, possibly an age-matched reference population. Different reference files at rest and during stress might not be necessary.     

Clinical evaluation of the 99mTc-CPI myocardial perfusion imaging

^99mTc-CPI myocardial perfusion scintigraphy including planar images in 35 patients and SPECT images in 16 patients has been studied. Scintigraphic data revealed that high quality ^99mTc-CPI myocardial perfusion images were obtained. The sensitivity and specificity of ^99mTc-CPI planar images in detecting CAD was 92% and 80% respectively. There was no significant difference in sensitivity for detecting CAD between planar and SPECT. However, the specificity of SPECT was much better than that of planar imaging.     

Improved diagnostic accuracy of planar imaging with technetium 99m-labeled tetrofosmin compared with thallium-201 for the detection of coronary artery disease

Background

Receiver operating characteristic (ROC) curve analysis provides detailed information about the performance of a diagnostic test.

Methods and Results

As part of a multicenter phase III trial, 160 patients with known or suspected coronary artery disease underwent planar stress-rest^99mTc-labeled tetrofosmin and stress-redistribution²⁰¹Tl imaging within 14 days of each other, to compare the diagnostic accuracy of these imaging modalities by ROC curve analysis. Coronary arteriography was used as the reference standard and greater than 70% stenosis was considered significant. ROC curve analysis showed improved detection of coronary artery disease with^99mTc-labeled tetrofosmin compared with²⁰¹Tl, with ROC curve areas of 0.765 versus 0.644, respectively (p=0.02).^99mTc-labeled tetrofosmin also better identified single-vessel disease in those without previous myocardial infarction (ROC curve areas of 0.684 vs 0.510 for^99mTc-labeled tetrofosmin and²⁰¹Tl, respectively;p=0.04) and enhanced the detection of multivessel disease in those with previous myocardial infarction (ROC curve areas of 0.764 vs 0.638, respectively;p=0.02).

Conclusions

Detailed assessment of diagnostic performance by ROC curve analysis shows that, for planar imaging,^99mTc-labeled tetrofosmin enhances the detection of coronary artery disease compared with²⁰¹Tl.     

Estimation of myocardial blood flow and myocardial flow reserve by <Superscript>99m</Superscript>Tc-sestamibi imaging: comparison with the results of [<Superscript>15</Superscript>O]H<Subscript>2</Subscript>O PET

We developed a noninvasive method to quantitatively estimate the myocardial blood flow (MBF) index and flow reserve (MFR) using dynamic and static data obtained with technetium-99m sestamibi, and compared the results with MBF and MFR measured by oxygen-15-labeled water ([(15)O]H(2)O) PET. Twenty patients with coronary artery disease (CAD) and nine normal subjects underwent both (99m)Tc-sestamibi and PET studies within 2 weeks. From the anterior view, dynamic data were acquired for 2 min immediately after the injection of (99m)Tc-sestamibi, and planar static images were also obtained after 5 min at rest and during ATP stress (0.16 mg kg(-1) min(-1) for 5 min) on another day. The area under the time-activity curve on the aortic arch (Aorta ACU), myocardial weight with the SPET image (M), and the myocardial count on the planar image for 1 min (C(m)) were obtained. The MBF index (MBFI) was calculated as follows: MBFI=Cm/Aorta ACU x 100M. MFR was measured by dividing the MBFI at ATP stress by MBFI at rest. The MBFI measured by (99m)Tc-sestamibi was significantly correlated with MBF obtained using [(15)O]H(2)O PET (MBFI=13.174+11.732 x MBF, r=0.821, P<0.001). Furthermore, MFR measured by (99m)Tc-sestamibi was well correlated with that obtained using [(15)O]H(2)O PET, with some underestimation (r=0.845, P<0.001). MFR using (99m)Tc-sestamibi in patients with CAD was significantly lower than that in normal subjects (CAD: 1.484+/-0.256 vs normal: 2.127+/-0.308, P<0.001). These data suggest that the MBFI and MFR can be measured with (99m)Tc-sestamibi. This may be useful for the quantitative assessment of CAD, especially in those patients with diffuse coronary disease.     

99mTc-tetrofosmin SPET in the detection of both primary breast cancer and axillary lymph node metastasis

The aim of this study was to evaluate the usefulness of ^99mTc-tetrofosmin single-photon emission tomography (SPET) in the detection of both primary breast cancer and axillary lymph node metastasis. We studied 192 consecutive patients in whom primary breast cancer was suspected on the basis of mammography and/or physical examination. After intravenous injection of 740 MBq ^99mTc-tetrofosmin, both planar and SPET scintimammography was performed in all patients using a rectangular dual-head gamma camera equipped with low-energy, high-resolution, parallel-hole collimators. In 175 patients with breast cancer at histology, the per-lesion overall sensitivity of SPET and planar imaging for the detection of breast cancer was 95.8% and 75.9% (P<0.0005), respectively. The sensitivity of SPET and planar imaging was, respectively, 96.5% and 79.5% in palpable (P<0.0005) and 90% and 45% in non-palpable lesions (P<0.01). With regard to lesion size, the sensitivity of SPET and planar imaging was, respectively, 90.5% and 45.2% in lesions ⢪ mm (P<0.0005), 95.3% and 81.4% in lesions of 11-20 mm (P<0.005), 100% and 84.6% in lesions of 21-30 mm (P<0.05) and 100% and 95.8% in lesions >30 mm (P>0.05). In the remaining 17 patients with benign mammary lesions at histology, per-lesion overall specificity of SPET and planar imaging was 76.2% and 85.7% (P>0.05), respectively. Neither SPET nor planar imaging showed false-positive results in non-palpable lesions or in those ⢪ mm. In 173 breast cancer patients submitted to axillary lymph node dissection (ALND), per-axilla overall sensitivity of SPET and planar imaging in the detection of axillary lymph node metastasis was 93% and 52.3% (P<0.0005), respectively. The sensitivity of SPET and planar imaging was, respectively, 100% and 82.6% in palpable nodes (P>0.05), 90.5% and 41.3% in non-palpable nodes (P<0.0005), 92.8% and 35.7% in the presence of Г nodes (P<0.0005) and 93.2% and 68.2% in the presence of >3 nodes (P<0.005). The specificity of SPET and planar imaging was 91% and 100% (P<0.05), respectively. ^99mTc-tetrofosmin SPET appears to be a reliable method for the detection of both primary BC and axillary lymph node metastasis, and its diagnostic accuracy exceeds that of ^99mTc-tetrofosmin planar scintimammography. The use of SPET is particularly important in the identification of small non-palpable primary carcinomas and metastatic axillae with Г non-palpable lymph nodes. More extensive use of SPET appears warranted in the management of breast cancer patients.     

Early detection of myocardial ischaemia in the emergency department by rest or exercise (99m)Tc tracer myocardial SPET in patients with chest pain and non-diagnostic ECG.

Chest pain (CP) represents a frequent reason for presentation at the emergency department (ED). A large proportion of patients have non-diagnostic ECG on presentation, and in many cases several hours have elapsed since onset of symptoms. Acute rest myocardial scintigraphy (rest SPET) has been shown to have a relevant role in the detection of patients at risk for coronary events, but its sensitivity and negative predictive value are optimal only within the first 3 h following onset of symptoms. In those with delayed presentation, exercise SPET alone, as a screening approach, appears more promising, but its feasibility and diagnostic role in the ED are still unresolved. A total of 231 consecutive patients with a recent-onset (<24 h) first episode of CP had a negative first-line work-up including ECG, troponins, creatine kinase-MB and echocardiography. These patients were considered at low risk for short-term coronary events. Patients were studied with rest SPET if they presented <3 h after onset of CP and exercise SPET if they presented after > or =3 h. The end-points of the study were detection of significant coronary artery disease (CAD) by angiography and major coronary events or cardiac death at 6 months. Eighty patients (35%) underwent rest SPET, while 151 (65%) underwent exercise SPET. Two of the 159 patients with negative SPET had evidence of critical CAD at 6-month follow-up (one patient in the rest SPET group and one in the exercise SPET group; P=NS). Of the 72 patients (31%) with a positive scan, 34 (15%) had documented CAD (16 patients in the rest SPET group and 18 in the exercise SPET group; P=NS). Sensitivity, specificity, accuracy and predictive value were not statistically different between the two groups. In conclusion, the accuracy of exercise SPET in patients with CP and delayed presentation to the ED is comparable to that of validated rest SPET in patients with early presentation. Owing to the high negative predictive value (99%), exercise SPET is especially valuable as a screening tool for the exclusion of CAD in low-risk patients and implementation of early discharge.     

The effect of collateral flow and myocardial viability on the distribution of technetium-99m sestamibi in a closed-chest model of coronary occlusion and reperfusion

Myocardial uptake of technetium-99m sestamibi at low coronary flow rates overestimates blood flow, but the relative impact of flow and viability on ^99mTc-sestamibi kinetics is unclear. The objective of this study was to determine the effect of myocardial viability and the degree of collateral blood flow on the uptake and retention of ^99mTc-sestamibi by examining three animal models of coronary occlusion and reperfusion, each reflecting a different state of viability and collateral blood flow. Three closed-chest animal models were studied: canine (high collateral flow, preserved viability), porcine (low collateral flow, absent viability) and porcine with slowly occlusive coronary stents producing infarction and enhanced collateral blood flow (high collateral flow, absent viability). There were seven dogs, seven pigs and six pigs, respectively, in each animal model. Animals from all three models were subjected to a 40-min total left anterior descending artery (LAD) occlusion followed by 2 h of reperfusion. ^99mTc-sestamibi and radiolabelled microspheres were injected during LAD occlusion 10 min prior to reperfusion. Animals were sacrificed after 2 h of reperfusion flow. Ex situ heart slice imaging to determine risk area was followed by viability staining to determine infarct size. Slices were subsequently sectioned into equally sized radial segments and placed in a gamma well counter. Risk area as determined by ex situ ^99mTc-sestamibi imaging was not significantly different by model. Pathological infarct size differed significantly by model [canine = 1%±1% of the left ventricle (LV); porcine = 13%±8% LV; porcine with stent = 14%±7% LV; P=0.002)]. Collateral blood flow by microspheres during occlusion tended to differ among models (overall P=0.08), with the canine and porcine with stent models having relatively high flow rates compared with the acute porcine model. ^99mTc-sestamibi activity correlated with microsphere blood flow in all three models, with r values for individual animals (n=20) ranging from 0.86 to 0.96 (all P<0.0001). There was a significant difference in the regression line intercepts (P<0.0001) and slopes (P<0.01) among the three models comparing ^99mTc-sestamibi uptake with myocardial blood flow. ^99mTc-sestamibi uptake overestimated blood flow to a greater extent in the canine model (high flow with viability) than in the porcine model (low flow, absent viability). Despite enhanced collateral flow, there was significantly less overestimation of flow in the porcine stent model (high flow, absent viability). In conclusion, at low flow rates ^99mTc-sestamibi activity overestimates myocardial blood flow. This effect is most pronounced in myocardium with significant collateral flow and preserved viability, consistent with over-extraction or redistribution of the tracer. The effect is markedly decreased in non-viable myocardium regardless of blood flow. Received: 18 October and in revised form 18 December 1999     

Implementation of myocardial perfusion imaging in the early triage of patients with suspected acute coronary syndromes

The risk of overlooking an underlying acute coronary syndrome remains an important challenge in patients complaining of chest pain but who have a non-diagnostic ECG (CP). Indeed, myocardial scintigraphy associated with exercise testing (exercise SPET) represents a valuable tool for excluding coronary artery disease (CAD) especially in patients with CP and delayed presentation to the emergency department. We sought to implement diagnoses of CAD in the early triage of CP patients by exercise gated SPET and compare diagnoses with outcomes. A total of 306 consecutive patients presenting with CP were found to be free of CAD at first line work-up including clinical evaluation, markers of myocardial injury and echocardiogram. These patients were studied initially with exercise SPET, and those with perfusion defects underwent angiography, while those with normal scans were discharged and followed up. Patients with positive scans (34%, n=105) had documented coronary stenoses in 43% (n=45); patients with negative scans (66%, n=201) had evidence of non-fatal coronary events at 6 months in 1.5% (n=3). When imaging was analysed with gating by the presence of transmural perfusion defects associated with wall motion abnormalities (n=86), only one patient, among 19 excluded, was recognized as having coronary stenosis by angiography (SPET vs gated SPET: negative predictive value 98.5% and 98%, respectively, P=NS; diagnostic accuracy 79% and 85%, respectively; P< or =0.03). Therefore, implementation of myocardial perfusion imaging in the early triage of patients with suspected acute coronary syndromes was effectively obtained by early exercise gated SPET, especially in patients with transmural myocardial perfusion defects associated with wall motion abnormalities.     

Dipyridamole and exercise SPET provide different estimates of myocardial ischaemic areas: role of the severity of coronary stenoses and of the increase in heart rate during exercise

In patients unable to perform a maximal exercise test, dipyridamole single-photon emission tomography (SPET) has a higher capacity than exercise SPET to detect coronary artery disease (CAD). However, in patients with myocardial ischaemia who are able to perform a maximal exercise test, it is not known whether these two tests may be equally used to assess the areas of myocardial ischaemia. This study was aimed at comparing the results provided by dipyridamole and exercise SPET in CAD patients with documented exercise myocardial ischaemia. Forty CAD patients who had undergone exercise thallium-201 SPET and who had myocardial ischaemia documented by an unequivocally positive exercise test underwent an additional ²⁰¹Tl SPET study after dipyridamole infusion and low-level (40 W) exercise. The extent of defects was compared between the two tests and predictors of discrepant results were sought among data from exercise testing and coronary angiography. The extent of SPET defects was equivalent between the two tests in only 11 patients (28%), larger defects being observed with exercise in 18 [average difference: 12%±5% of left ventricle (LV)] and with dipyridamole in 11 (average difference: 15%±11% of LV). The best independent predictors of discrepancies between the two tests were: (1) increase in heart rate at exercise SPET, with defects being smaller at exercise than after dipyridamole in none of the patients with an increase >60 bpm (0/14), but in 42% of the others (11/26; P=0.004); and (2) an ischaemic territory related to a <70% coronary stenosis, for which SPET defects were always induced at exercise (10/10) but in only 30% (3/10) with dipyridamole (P=0.0004). Exercise and dipyridamole SPET provide different estimates of myocardial ischaemic areas. Dipyridamole allows the unmasking of perfusion abnormalities in patients who have low increases in heart rate at exercise SPET. However, dipyridamole is also much less efficient at inducing perfusion abnormalities in the ischaemic areas supplied by coronary stenoses of intermediate severity at rest angiography. Received 20 January 2000 and in revised form 18 March 2000