Left ventricular perfusion and performance from a single radiopharmaceutical and one camera.

To test the hypothesis that a small field of view portable multicrystal scintillation camera can perform stress/rest combined LV function by first-pass and perfusion studies using 99mTc-teboroxime, 26 patients with positive stress thallium studies within 2 wk and 8 healthy volunteers were studied. A 241Am point source marker over the sternum was used for motion correction. Dynamic dual-isotope (99mTc/241Am) acquisition was performed following injection of 15.6 +/- 2.3 mCi of 99mTc-teboroxime at peak treadmill exercise. Two minutes later (blood-pool clearance), while still standing on the flat treadmill, 3-4 40-sec planar images were acquired. One hour later patients were reinjected with 22.7 +/- 3.4 mCi of 99mTc-teboroxime while standing in front of the camera and the same dynamic/static acquisition protocol repeated. The planar images were interpolated from a 20 x 20 matrix to a 160 x 160 matrix, a sharpening filter and an interpolative background subtraction algorithm applied. The scans were divided into segments, each scored as normal, reversible and fixed. The agreement with thallium imaging for identifying an abnormal scan was 24/26 (92%) and for identifying abnormal vascular territories was 43/52, (83%). Fourteen patients had exercise LVEF less than 50% and all had either prior myocardial infarction, myocardial infarction plus ischemia or LAD ischemia. Diagnostic planar perfusion images and exercise LVEF can be acquired in less than 4 min using 99mTc-teboroxime and a portable multicrystal scintillation camera.

Imaging of cardiac transplantation rejection in primates using two new antimyosin agents.

Indium-111-labeled monoclonal antimyosin Fab has been used to image myocardial infarction, myocarditis and cardiac transplant rejection with localization in myocytes that have suffered irreversible loss of cell membrane integrity. Technical factors potentially limiting clinical usefulness of 111In antimyosin include dosimetry (72 hr half-life of 111In), slow blood clearance of antibody proteins delaying optimal imaging to 24 to 48 hr postinjection and nontarget organ uptake. Therefore, two new antimyosin imaging agents experimentally shown to potentially improve dosimetry, shorten time from injection to imaging or decrease nonspecific cell binding were evaluated in a primate cardiac transplant model. The two agents evaluated were polylysine 111In-antimyosin (0.023 mg Fab modified with a 3.3 kd polymer of polylysine and labeled with 111In) and 99mTc-antimyosin (0.5 mg Fab' antimyosin labeled using the RP-1 ligand technique). A total of eight baboons were studied: three with heterotopic (cervical) xenographs, three with orthotopic allographs and two control animals. Each animal was injected first with 12-23 mCi of 99mTc-RP-1 antimyosin and 5-16 hr after completion of imaging, was injected with 0.72-1.88 mCi of 111In-polylysine antimyosin (PIs) and reimaged 12-48 hr later. The imaging results were compared to the histology of the animals. Biexponential curves were fit to the blood sample data and rate constants were determined and expressed as T1/2 values. There were no significant differences between the two agents in either the early fast components or the late slow components. On planar imaging, there was blood-pool activity at 10-12 hr postinjection of both agents, but by 16-24 hr postinjection, blood pool was negligible on the 111In-PIs scans. Both agents were concentrated in the rejected cardiac tissue. The slow blood-pool clearance combined with the 6 hr half-life of 99mTc-RP-1 AMA make this agent less promising for detection of diffuse myocardial uptake than 111In Fab modified with polylysine.

Diagnosis of right ventricular acute myocardial infarction by dual isotope thallium-201 and indium-111 antimyosin SPECT imaging.

To assess the diagnostic value of indium-111 antimyosin for detecting right ventricular (RV) wall acute infarction, 30 patients with electrocardiographic-documented left ventricular inferior (posterior) wall acute myocardial infarction underwent simultaneous dual isotope indium-111 antimyosin and thallium-201 single-photon emission computed tomography (SPECT) within 2 days of admission. RV necrosis was defined as uptake of indium-111 antimyosin anterior and to the right of septal thallium uptake. Twenty-nine of the 30 patients (97%) had indium-111 antimyosin uptake in the inferior, posterior or lateral walls of the left ventricle and 14 of 30 (47%) had additional RV antimyosin uptake. Three different patterns of RV uptake of indium-111 antimyosin were observed: crescent-shaped, focal and apical. Twenty-seven patients underwent gated blood pool scanning before hospital discharge. Twelve of the 14 patients with RV antimyosin uptake had gated blood pool scintigraphy and 7 of 12 had RV dysfunction; 5 had normal RV function. Except for 1 patient who had questionable RV antimyosin uptake and had RV dysfunction, no patient without RV antimyosin uptake had RV dysfunction. In summary, right and left ventricular necrosis can be detected on tomographic images of indium-111 antimyosin uptake in patients with inferior infarctions when simultaneous uptake of a perfusion tracer, thallium-201, is imaged and used as an aid to reconstruction and anatomic localization.

Thallium-201 lung uptake and peak treadmill exercise first-pass ejection fraction.

Increased thallium-201 lung uptake immediately after exercise has been shown (1) to be a marker for extensive coronary artery disease, (2) to correlate with low rest and exercise left ventricular ejection fraction by supine gated blood pool scintigraphy, and (3) to be a powerful independent predictor of future cardiac events. Exercise left ventricular ejection fraction measured during upright exercise by the first-pass technique has also been shown to be a powerful independent prognostic variable. Combined perfusion and exercise left ventricular ejection fraction can be acquired by using the technetium 99m-based myocardial perfusion agents and offers an alternative protocol to stress/redistribution thallium imaging. It is therefore clinically important to understand the relation between exercise lung heart thallium uptake and exercise left ventricular ejection fraction. Accordingly, both these measurements were acquired in 38 patients with documented coronary artery disease who underwent two treadmill exercise studies. Parameters obtained from the first-pass study that are known to affect lung thallium uptake were correlated with exercise lung/heart thallium ratios; lung/heart ratios were used in a model to predict exercise left ventricular ejection fraction values. Exercise left ventricular ejection fraction and peak filling rate showed significant negative correlations with thallium lung/heart ratio, but the first-pass variables examined were not independently predictive of thallium lung uptake. The chance of finding an abnormal thallium lung/heart ratio at exercise LVEF of 40% is only 52%, whereas the chance of finding an abnormal ratio at exercise LVEF of 30% is 74%.(ABSTRACT TRUNCATED AT 250 WORDS)