Technetium-99m-Sestamibi SPECT myocardial perfusion imaging in patients with complete left bundle branch block.

BACKGROUND: Diagnosis of coronary artery disease (CAD) in patients with left bundle branch block (LBBB) is considered a challenge in cardiology due to low accuracy of noninvasive methods such as basal and exercise stress test. Recently, myocardial perfusion imaging showed attainment of higher sensitivity and specificity. Scintigraphy with thallium-201 has been widely used in these patients. Few have used technetium-99m-Sestamibi and single photon emission computed tomography (SPECT). The aim of the study was to assess the diagnostic value of Tc-99m Sestamibi SPECT myocardial perfusion imaging in patients with complete LBBB. METHODS: We studied 57 consecutive patients with complete LBBB using Tc-99m-Sestamibi SPECT and treadmill or dipyridamole stress to evaluate CAD. Eighteen patients also underwent coronary angiography. Perfusion defects were classified as fixed or reversible. RESULTS: Prevalence of resting perfusion abnormalities in anterior, septal, and apical regions was 51, 56, and 19%, respectively. Sensitivity for detecting >50% left anterior descending artery (LAD) stenosis was 67 and 56% for anterior or septal defects, and 56% for specificity. Apical perfusion abnormality showed 21% sensitivity and 89% specificity. Among six patients with reversibility and who underwent coronary angiography, all had >50% LAD stenosis. CONCLUSIONS: With Tc-99m-MIBI SPECT imaging, prevalence of anteroseptal perfusion abnormalities was >50% in patients with LBBB. The test has moderate sensitivity and specificity for LAD disease. Absence of apical defect is specific for excluding LAD disease. Reversible changes in anteroseptal wall should be considered as an indicator of ischemia in this territory.

Artifactual 2-deoxy-2-[(18)F]fluoro-D-glucose localization surrounding metallic objects in a PET/CT scanner using CT-based attenuation correction.

PURPOSE: To communicate a clinically important artifact in positron emission tomography (PET) images using a PET/computerized tomography (CT) scanner with CT-based attenuation correction. PROCEDURE: A 65-year-old man with a maxillary sinus squamous cell carcinoma was injected with 2-deoxy-2-[(18)F]fluoro-D-glucose (FDG) and underwent a PET scan using a dual modality PET/CT scanner with CT-based attenuation correction. Immediately afterward, the patient had a second scan using a different PET scanner that used a high-energy transmission source for attenuation correction. RESULTS: The PET/CT scanner images demonstrated a focus of activity in the attenuation corrected PET images corresponding to a pacemaker in the left chest wall. No abnormal focus was noted in the nonattenuation corrected PET images. The patient had no signs or symptoms of inflammation at the site. A second scan using a PET scanner with a high-energy transmission source demonstrated no abnormal focus in the AC PET images. CONCLUSIONS: PET/CT scanners using CT-based attenuation methodology can overcorrect dense objects resulting in hot spot artifacts in AC PET images.

Prolonged ST segment depression after stress testing: does it really identify more severe disease?

BACKGROUND: It is generally perceived that the persistence of ST segment depression for more than 5 min after treadmill exercise testing (ETT) signifies a strongly positive test and predicts more severe ischemia and coronary artery disease. AIM: The aim of this study was to determine if prolonged ST segment changes (>5 min) after ETT identifies patients with more severe ischemia and thus severe coronary artery disease. METHODS: Twenty five patients (19 males, mean age 58+/-10 years) with >1 mm ST segment depression and recovery time 1 mm ST segment depression and recovery time >5 min (group 2) undergoing ETT and single photon emission computed tomography were prospectively enrolled. Summed stress and difference scores, stress and reversible extent % of perfusion abnormalities, and lung heart ratio was calculated. RESULTS: There was no significant difference in the mean summed stress score (9+/-9 versus 13+/-10, P=0.13), summed difference score (4+/-3 versus 6+/-5, P=0.13), stress extent % (14+/-16 versus 19+/-13, P=0.13), extent of reversibility % (7+/-9 versus 7+/-7, P=0.93), or lung heart ratio (0.48+/-0.07 versus 0.46+/-0.07, P=0.50) between the two groups. There was no significant difference in the incidence of severe ischemia (summed difference score >13) in the 2 groups (24% versus 40%, P=0.36). CONCLUSION: We conclude that utilizing the commonly used cutoff for prolonged ST segment depression: >5 min in recovery, does not identify patients with more severe ischemia or coronary artery disease and, therefore, at increased risk. Thus, it appears unnecessary to give special consideration to these patients by way of prolonged monitoring in recovery, or a more aggressive non-invasive ischemia imaging approach after the ETT.

Noninvasive monitoring of somatostatin receptor type 2 chimeric gene transfer.

UNLABELLED: Noninvasive monitoring of gene transfer will benefit basic research and patient care. Most gene-transfer imaging systems do not directly detect the gene of interest, and most do not exploit radiopharmaceuticals that have Food and Drug Administration approval for total-body use. (111)In-Octreotide is used clinically to locate tumors overexpressing primarily somatostatin receptor type 2 (SSTR2). We report the in vitro and in vivo detection of SSTR2 chimeric gene transfer with this radiopharmaceutical. METHODS: Full-length SSTR2A was ligated into a vector downstream of a 5' Igkappa leader sequence and the hemagglutinin A (HA) sequence. The vector plus insert was then introduced into HT1080 cells. Igkappa and HA domain functions were confirmed by immunologic methods. Receptor binding was studied in transfected cells incubated with (111)In-octreotide with and without somatostatin-28. Mice bearing tumors produced by transfected cells were injected with (111)In-octreotide for biodistribution and imaging studies. RESULTS: Cell-membrane localization by the amino-terminal Igkappa domain was confirmed by immunofluorescence. The HA domain was identified by enzyme-linked immunosorbent assay, immunofluorescence, and Western blotting analysis with anti-HA antibodies. (111)In-Octreotide detected the SSTR2 portion of the fusion protein in vitro (receptor-binding assay) and in vivo (biodistribution studies and gamma-camera imaging). In addition, in vitro studies using either the anti-HA antibody or (111)In-octreotide correlated with biodistribution and imaging studies when cell clones expressing different levels of the fusion protein were tested. This approach may be feasible clinically because we were able to discern chimeric gene transfer in tumor-bearing animals with (111)In-octreotide at doses similar to those already used in humans. CONCLUSION: With this method it may be possible to monitor transfer of a gene of interest directly and noninvasively.

Slow upsloping ST-segment depression during exercise: does it really signify a positive stress test?

BACKGROUND: Slow upsloping ST-segment depression during stress is thought to represent an ischemic response to exercise treadmill testing (ETT). AIM: We used modern single-photon emission computed tomography (SPECT) imaging protocols to determine the incidence of ischemia in patients with slow upsloping ST depression during exercise and whether this response signifies more or less severe coronary artery disease (CAD) and risk in comparison with rapid upsloping ST depression and particularly with horizontal or downsloping ST depression. METHODS: We enrolled 33 patients (group 1) with rapid upsloping ST depression (>1 mm extending <0.08 seconds beyond J point), 32 patients (group 2) with slow upsloping depression (>1.5 mm extending >0.08 seconds beyond J point), and 35 patients (group 3) with horizontal or downsloping depression (>1 mm at 0.08 seconds beyond J point). Summed stress score (SSS), summed difference score (SDS), stress extent percent (SE%) and reversible extent percent (RE%) of perfusion abnormalities, lung-heart ratio (LHR), and transient ischemic dilatation (TID) were calculated. RESULTS: The mean SSS, SDS, SE%, RE%, and LHR were similar between groups 1 and 2 but significantly higher in group 3. Incidence of ischemia was similar in groups 1 and 2 (39% and 25%) but significantly higher in group 3 (77%, P <.001). Evidence of TID was seen in none of the patients in groups 1, in 3% of patients in group 2, and in 23% of patients in group 3. CONCLUSIONS: Slow upsloping ST depression does not signify more severe ischemia, more extensive CAD, or more stress-induced backward left ventricular failure. Thus, it would be reasonable to consider patients with slow upsloping ST depression during exercise as having a very low likelihood of CAD, similar to patients with rapid upsloping ST depression.

Atlas of Myocardial Perfusion SPECT

It contains seventy teaching cases, presented with relevant clinical information such as case history, imaging/study data, and myocardial perfusion SPECT images. The "findings" section provides annotated images and text explanations of the images.