Comparison of baseline-nitrate technetium-99m sestamibi with rest-redistribution thallium-201 tomography in detecting viable hibernating myocardium and predicting postrevascularization recovery.

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.

Sublingual isosorbide dinitrate to improve technetium-99m-teboroxime perfusion defect reversibility.

UNLABELLED: Previous studies demonstrate perfusion defect reversibility in 201Tl reinjection imaging performed after the administration of nitrates. This study tests whether the acute sublingual administration of isosorbide dinitrate (ISDN) could improve the capability of 99mTc-teboroxime to detect reversibility in exercise-induced perfusion defects. METHODS: Ten patients with previous myocardial infarction underwent exercise, redistribution and reinjection 201Tl imaging, 99mTc-teboroxime exercise and rest scans. Following the latter, 5 mg sublingual ISDN were given, 99mTc-teboroxime was reinjected and images collected. RESULTS: The total defect score/patient in the 201Tl images was 10.5 +/- 3.1 (mean +/- s.d.), decreasing to 7.4 +/- 2.7 after redistribution (p < 0.02) and to 4.8 +/- 2.1 after reinjection (p < 0.01 versus redistribution). The total defect score in 99mTc-teboroxime exercise images was 12.7 +/- 3.1 (p < 0.05 versus 201Tl exercise), decreasing to 7.3 +/- 3.3 at rest (p < 0.01 versus exercise, NS versus 201Tl redistribution) and to 5.6 +/- 2.6 in ISDN images (p < 0.02 versus rest, p < 0.05 versus 201Tl redistribution, NS versus reinjection). Of the 44 abnormal segments in 201Tl exercise images, the redistribution scan identified 26 defects as reversible and 18 as fixed. After reinjection, 37 defects appeared reversible and only seven fixed (p < 0.005 versus redistribution). Stress-rest 99mTc-teboroxime classified 33 segments as reversible and 11 as fixed (NS versus both 201Tl protocols). After ISDN, the uptake score increased in 19 segments. Therefore, 37 were classified as reversible and seven as fixed defects (p < 0.01 versus 201Tl redistribution, NS versus 201Tl reinjection). CONCLUSIONS: Sublingual ISDN before 99mTc-teboroxime rest injection seemed to improve the tracer capability of detecting reversibility in exercise-induced perfusion defects.

Left ventricular cavity-to-myocardium count ratio in technetium-99m-sestamibi SPECT in the detection of resting left ventricular dysfunction.

UNLABELLED: The aim of this study was to assess the value of the cavity-to-myocardium count ratio (C/M ratio) calculated in resting 99mTc-sestamibi SPECT images to identify patients with depressed left ventricular ejection fraction (LVEF). METHODS: In the 95 patients studied, the C/M ratio was calculated from the midventricular short-axis slice using regions of interest drawn in the center of the cavity and in the most active area of the ventricular wall; its value was compared with LVEF measured using two-dimensional echocardiography. RESULTS: The C/M ratio correlated with LVEF (r = 0.6, p < 0.000001) and was significantly lower in patients with abnormal LVEF than those with normal LVEF: 0.026 +/- 0.028 versus 0.125 +/- 0.093, p < 0.000001. In the entire patient population, a C/M ratio < 0.07 identified the patients with depressed LVEF with a 94% sensitivity, 71% specificity and 82% accuracy. CONCLUSION: The resting 99mTc-sestamibi C/M ratio is a useful parameter in identifying patients with depressed LVEF directly from the SPECT perfusion images.

Evaluation of 99Tcm-teboroxime scintigraphy for the differentiation of reversible from fixed defects: comparison with 201T1 redistribution and reinjection imaging.

The aim of this study was to compare 99Tcm-teboroxime and 201T1 myocardial studies with particular regard to the classification of perfusion defects as reversible or fixed. Twenty patients with a history of previous myocardial infarction and suspected effort ischaemia underwent exercise 201T1 scintigraphy with early (4 h) redistribution and reinjection scans, exercise and rest 99Tcm-teboroxime imaging and coronary angiography. Using a qualitative scoring of static planar images, the perfusion defects were classified as reversible or fixed. 201T1 and 99Tcm-teboroxime gave comparable results in the evaluation of the individual vessels (sensitivity 65%, specificity 80% and 85%, respectively). The stress-redistribution 201T1 sequence classified 45 defects as reversible and 28 as fixed, the stress-rest 99Tcm-teboroxime studies classified 47 as reversible and 26 as fixed (NS). The stress-reinjection 201T1 images, however, characterized 64 defects as reversible and nine as fixed (P < 0.005 versus 201T1 redistribution, P < 0.0005 versus 99Tcm-teboroxime rest). In conclusion, this study shows that rest 99Tcm-teboroxime and 201T1 redistribution give comparable results but that significantly more defects are classified as fixed by 99Tcm-teboroxime than by 201T1 if reinjection of the latter tracer is performed.

[Myocardial scintigraphy with Tc-99m-teboroxime: its feasibility and the evaluation of its diagnostic reliability. A comparison with thallium-201 and coronary angiography]. / Scintigrafia miocardica con Tc-99m-teboroxime: fattibilità e valutazione dell'affidabilità diagnostica. Confronto con il tallio-201 e l'angiografia coronarica.

BACKGROUND: Tc-99m-teboroxime is a new tracer for myocardial perfusion scintigraphy. Its more remarkable features are the high myocardial extraction fraction, which is well correlated with the coronary blood flow, and the extremely rapid myocardial washout. This makes it necessary to complete the image collection shortly after the injection; on the other hand, repeated scans can be easily performed by renewed Tc-99m-teboroxime administrations. The aim of the present study was to test the feasibility of Tc-99m-teboroxime imaging and to evaluate its accuracy by comparing it with thallium-201 (TI-201) scintigraphy and coronary angiography. METHODS: The patient population included 16 male patients (mean age 57.8 +/- 6.3 years) affected by suspect effort angina and/or with signs of exercise-induced ischemia; 12 of them had history of previous myocardial infarction. They underwent effort TI-201 and Tc-99m-teboroxime myocardial scintigraphy within 48 hours; left heart catheterization and coronary angiography were performed within 5 days. Scintigraphic images were collected in 3 planar views; each projection was divided in 3 segments, with the apical one shared by all views, for a total of 7 segments/study. Tracer uptake was qualitatively assessed and graduated according to a scoring scheme (from 0 = normal through 4 = absent uptake). RESULTS: Tc-99m-teboroxime scans could be accomplished without major problems in all subjects. The image quality was comparable to TI-201 in 8 patients and poorer in the remaining 8. Coronary angiography showed 50% obstructions in 15 patients; of them 1 subject had a normal scintigraphic pattern with both TI-201 and Tc-99m-teboroxime. The presence of previous infarction was recognized by both tracers in the 12 patients with infarct history. The number of abnormal segments and the uptake score were not significantly different in the Tc-99m-teboroxime rest and in the TI-201 redistribution images (segments: 2.8 +/- 1.4 vs 2.8 +/- 1.6; score: 5.6 +/- 4.2 vs 6 +/- 4.5). The diagnosis of effort ischemia was made in 13 patients with Tc-99m-teboroxime and in 12 patients with TI-201. The number of abnormal segments in the exercise Tc-99m-teboroxime and TI-201 myocardial scintigraphy was not significantly different (3.3 +/- 1.3 vs 3.3 +/- 1.5); on the contrary the defect score was significantly higher with Tc-99m-teboroxime than with TI-201 (9.5 +/- 4.3 vs 8.4 +/- 4.6, p < 0.03). Therefore the ischemic score (exercise defect score minus rest defect score) of Tc-99m-teboroxime was significantly higher than that of TI-201 (3.9 +/- 2.8 vs 2.4 +/- 2.2, p < 0.02). The two tracers gave comparable results in terms of recognition of patients with one-vessel or multi-vessel coronary artery disease. CONCLUSIONS: Planar myocardial scintigraphy with Tc-99m-teboroxime can be performed without major problems. In terms of clinical reliability the results are comparable to those of TI-201 scans. On the other hand, taking into account the poor image quality of Tc-99m-teboroxime scintigraphy, it is still impossible to predict its future role in the radionuclide imaging of coronary artery disease.

Head-to-head comparison of exercise stress testing, pharmacologic stress echocardiography, and perfusion tomography as first-line examination for chest pain in patients without history of coronary artery disease.

BACKGROUND: To overcome the relatively low accuracy of exercise stress testing (EST) in detecting coronary artery disease (CAD), both echocardiography and perfusion scintigraphy have been evaluated in conjunction with pharmacologic stress, but there is still uncertainty of the relative value of these tests as possible first-line examinations for suspected CAD. This study evaluated the accuracy of EST, dipyridamole and dobutamine stress echocardiography (DIP-ECHO, DOB-ECHO), and dipyridamole and dobutamine technetium 99m sestamibi tomography (DIP-MIBI, DOB-MIBI) for the detection of CAD in patients evaluated for the first time because of chest pain. METHODS AND RESULTS: Sixty patients underwent EST, DIP-ECHO, DOB-ECHO, DIP-MIBI, and DOB-MIBI. Echocardiographic images were acquired simultaneously with sestamibi injections, and the scintigraphic images were collected 1 hour later. Coronary angiography was performed within 15 days. Out of 33 patients with significant (>70%) coronary stenoses, 19 (58%) were correctly identified by EST, 18 (55%) by DIP-ECHO, 20 (61%) by DOB-ECHO, 32 (97%) by DIP-MIBI, and 30 (91%) by DOB-MIBI (p < 0.005 for MIBI vs EST and ECHO). The specificity of EST was 67% (p < 0.05 vs ECHO and MIBI), 96%, 96%, 89%, and 81%, respectively. Of the 62 stenotic coronary arteries, 20 (32%) were correctly identified by DIP-ECHO, 24 (39%) by DOB-ECHO, 48 (77%) by DIP-MIBI, and 45 (73%) by DOB-MIBI. The sensitivity of the imaging techniques in predicting the presence of multivessel disease was 14% and 29% for DIP and DOB-ECHO compared with 48% and 57% for DIP and DOB-MIBI. CONCLUSIONS: Our results confirm the limited reliability of EST in detecting CAD and the good diagnostic value of DIP and DOB-MIBI. Conversely, the lower sensitivity and the poorer capability to recognize multivessel CAD do not support the role of either DIP or DOB-ECHO as first-line examination for suspected CAD.