Diagnosis of acute myocardial infarction by indium-111 antimyosin antibodies and correlation with the traditional techniques for the evaluation of extent and localization

The current role of infarct avid imaging

Tc-99m pyrophosphate is the grandfather of infarct avid agents. Its value is its clinical availability and ease of use. However, its shortcomings are the delay of 2 to 3 days for reliable interpretation in nonreperfused myocardial infarction (MI) and the overarching bone activity. Antimyosin provides exquisite specificity for the detection of myocardial necrosis irrespective of the cause of the injury. Therefore, diagnosis of equivocal MI or confirmation of diffuse myocardial necrosis would benefit from the availability of In-111 labeled antimyosin Fab. The drawback of antimyosin, like that of Tc-99m pyrophosphate, is the delay, in this case because of the protracted blood clearance of the antibody protein macromolecules. Tc-99m glucaric acid, on the other hand, may fulfill the original role envisioned for antimyosin, which was to enable early, rapid diagnosis of acute MI. However, the window for the use of Tc-99m glucaric acid appears to be limited to within the first day of the acute event. Therefore, there is a potential use of both Tc-99m glucaric acid and In-111 antimyosin in tandem with Tc-99m glucaric acid, which would not only facilitate early detection and diagnosis of acute MI and diagnosis of equivocal MI, but also may permit stratification of the infarct age.

Cardiac myofibrillar proteins: biochemical markers to estimate myocardial injury

Ischaemic heart disease represents the most common of the serious health problems in the contemporary society and acute myocardial infarction (AMI) is the major cause of cardiovascular morbidity and death. The accurate localization and determination of the infarct size and the volume of myocardium at risk at the time of insult is crucial and vital for the choice of treatment. Initially the ischaemic cells are reversibly injured. However, if these changes are not reverted at the earliest, it results in the death of the myocyte. This irreversible myocyte necrosis travels transmurally towards epicardium in the form of a wavefront. A timely intervention during evolving infarct could reduce and delimit the infarct and preserve the left ventricular function. Enzyme analysis and electrocardiography (ECG) along with the clinical history of the patient is still considered to constitute a reliable triad in the diagnosis of myocardial infarction (MI). Efforts have been made to relate infarct size with the serum enzyme level changes without much success. In addition, a number of specialist techniques such as planar radioisotope imaging, single photon emission computed tomography (SPECT), positron emission tomography (PET), Echocardiography, Ventriculography and nuclear magnetic resonance (NMR) imaging have been devised to support diagnosis in the patients who show ambiguous symptoms and ECG findings. However most of these procedures are unavailable to the patients due to economic reasons while others have suffered due to non-availability of ideal radiopharmaceuticals. Major advances have been made in the methods based on immunological techniques to improve the detection and estimation of infarct. These methods are exclusively based upon the production and availability of specific antibodies against intracellular, cardiac specific components.

Indium-111 antimyosin scintigraphy before and after coronary bypass surgery: unexpected preoperative myocardial uptakes

The present study was designed to evaluate 111In-antimyosin scintigraphy in detecting pre- and post-operative myocardial infarction in patients undergoing coronary artery bypass surgery. Fab antimyosin scintigraphy has been shown to be sensitive and specific in detecting myocardial necrosis and to be potentially valuable in situations where other criteria are not reliable. In a previous study, postoperative antimyosin uptakes occurred in 82% of the studied patients. Sixteen consecutive patients with an indication of coronary artery surgery were assessed by preoperative coronary angiography, serial electrocardiograms, and myocardial scanning with 111Indium-labeled antimyosin antibodies performed before and after operation. In four patients, a recent myocardial infarction (1 to 3 months) was detected with an accurate localization when compared to the classic criteria of myocardial infarction. One more patient with a 21-year old myocardial infarction showed an intense uptake whereas there was no recent acute coronary event. Four other patients had an unexpected preoperative uptake, since there were no acute coronary events in their medical history. All preoperative scintigraphic uptakes were still present on the second scan performed postoperatively in these nine patients. Only one patient showed a new postoperative uptake when compared to the preoperative scan which was normal; this postoperative septal infarct was confirmed by a postoperative coronary angiography. Extracardiac uptakes (sternum and ribs) were frequently observed after operation and might hamper the interpretation of postoperative scintigrams. Unexpected preoperative uptakes may be related to non diagnosed small necrosis. A preoperative reference scan is required for an accurate interpretation of a postoperative 111In-antimyosin uptake. Moreover, extracardiac uptakes may limit the interpretation of perioperative cardiac damage.

A human monoclonal antibody obtained from EBV-transformed B cells with specificity for myosin

We describe the preparation of a stable human lymphoblastoid cell line obtained during ex vivo studies in which peripheral blood lymphocytes of a Glanzmann's thrombasthenia patient were transformed with Epstein-Barr virus. Somatic hybrids secreted an IgM monoclonal antibody (B7) that reacted with the myosin heavy chain of human platelets by immunoblotting. Flow cytometry showed that B7 barely recognized unstimulated intact platelets, but bound abundantly after permeabilization of fixed cells with Triton X-100. The reactivity of the antibody on thin sections of human myocardium and aorta was studied by immunohistochemistry. B7 specifically stained myosin of myocytes, but there was no labelling of aortic smooth muscle cells. The epitope was conserved in cardiac or skeletal myosin prepared from pig or rabbit. Measurement of the dissociation constant in a competitive ELISA showed that B7 bound with high affinity (10(-8) M). Purified Fab fragments retained their ability to bind to myosin, suggesting that B7 may be useful in the imaging of myocardial necrosis after myocardial infarction, myocarditis, cardiac drug toxicosis or graft rejection. This work also shows that EBV transformation of B cells may uncover naturally occurring autoantibodies which under normal circumstances are inhibited by the immune surveillance system.

Technetium-99m antimyosin antibody (3-48) myocardial imaging: human biodistribution, safety and clinical results in detection of acute myocardial infarction

Technetium-99m antimyosin (99mTc-AM) antibody imaging may have significant advantages over indium-111 antimyosin in clinical practice. The purpose of this study was to determine the human biodistribution, the safety profile and the sensitivity of 99mTc-AM (3-48) imaging in the detection of both Q-wave and non-Q-wave myocardial infarction (MI). Biodistribution and safety parameters were mainly determined in 12 normal healthy volunteers while 40 patients with proven MI (22 Q-wave, 18 non-Q-wave) were injected with 99mTc-AM (20-25 mCi) between 5 h and 7 days after the onset of acute chest pain. Three standard planar views were performed at 6 h and at 24 h post injection. Both sets of images were completed in 33 patients while two patients were imaged only at 6 h, three patients only at 18 h and one at 18 and 24 h. One patient was not imaged. Vital signs and ECG were recorded and blood samples for haematology, biochemistry and human antimurine antibodies (HAMA) and urinalysis were obtained in all volunteers and patients. No serious adverse reactions or side-effects attributable to 99mTc-AM have been reported. No volunteers or patients developed allergic reactions or significant increases in HAMA titres. Reading of 99mTc-AM imaging was performed by two blinded experienced observers. The sensitivity of 99mTc-AM in the detection of MI was 100% (21/21) for Q-wave and 83.3% (15/18) for non-Q-wave infarctions. The overall sensitivity was 92.3% (36/39). The three false-negative cases were inferoposterior MI. A certain degree of uptake focalization was seen in 26 out of 35 (74.2%) at 6 h. At 24 h, two patients (5.8%) did not show 99mTc-AM uptake while 22 (64.7%) showed intense focal uptake, seven (20.6%) moderate uptake and 3 (8.9%) slight uptake. It is concluded that 99mTc-AM (3-48) imaging is safe and shows high sensitivity in the detection of both Q-wave and non-Q-wave MI even with early imaging (6 h post injection). These promising results warrant further clinical investigation.

Antibody imaging in the evaluation of cardiovascular diseases

Antimyosin antibody was originally developed for in vivo detection of acute myocardial infarction. However, its utility has expanded to include diagnosis of various cardiovascular diseases in which myocyte necrosis constitutes an obligatory component of the disease. Thus antimyosin has also been used clinically for noninvasive diagnosis of acute myocarditis, heart transplant rejection, drug-induced cardiotoxicity, and other cardiomyopathies. This first-generation monoclonal antibody, antimyosin, has opened the way for the second-generation monoclonal antibodies such as antifibrin and antiplatelet for in vivo diagnostic use in the detection of deep venous thrombosis and pulmonary embolism and antiatherosclerotic lesion-specific antibody for diagnosis of metabolically active lesions. Whether the third generation of antibodies will include ultrasmall antigen-binding units or negative charge-modified antibodies must await future studies.

Visualization of myocardial infarction six hours after injection of 111 In-antimyosin antibodies using an image subtraction technique

111 In-antimyosin antibodies are capable of visualizing acute myocardial infarction (MI). Because of slow blood clearance, images are usually recorded 24 or 48 h postinjection. This pilot study was aimed at validating a blood pool subtraction technique, which makes it possible to visualize MI 6 h postinjection. Twenty-five patients with proven MI (16 anterior, 9 inferior) were imaged 10 minutes, 6 and 24 h after an injection of 110 MBq 111 In-labelled antimyosin antibodies, with a mean delay of two weeks after infarction. Three planar views were obtained each time. Using software which performs geometric registration, grey level normalization and subtraction of images, the blood pool image (obtained 10 minutes postinjection) was subtracted from the 6 hour image. The resulting image was the blood pool corrected 6 h image. The 24 h images and the blood pool corrected 6 h images were interpreted blindly and the number of correct, incorrect and indeterminate MI localizations were tabulated. The number of correct localizations was 19/25 for the standard 24 h images and 22/25 for the blood pool corrected 6 h images. With this blood pool subtraction method it was possible to visualize MI 6 h postinjection. Theoretically, this method could be applied six hours after myocardial infarction.

Simultaneous assessment of left ventricular perfusion and function with technetium-99m sestamibi after coronary artery bypass grafting

This study examined the left ventricular perfusion and EF by using simultaneous SPECT and first-pass radionuclide angiography with technetium 99m sestamibi in 95 patients after uncomplicated coronary artery bypass grafting. The patients were divided into those with normal EF and no previous myocardial infarction before surgery (group 1, n = 57), and those with abnormal EF or infarction (group 2, n = 38). The SPECT images were normal in 37 patients in group 1 and in 6 patients in group 2 (p < 0.0001). The patients with normal SPECT images had a higher EF after surgery than those with abnormal images (65% +/- 10% vs 50% +/- 14%, p < 0.0001) and was higher in group 1 than in group 2 (64% +/- 8% vs 46% +/- 16%, p < 0.0001). There was a significant correlation between the EF and the extent of perfusion abnormality (r = -0.44, p < 0.0001). The patients with normal SPECT images could not be separated from those with abnormal images based on peak CK, CK-MB, and the electrocardiographic changes. Of the 69 patients with postoperative EF > or = 50%, the perfusion pattern was normal in 41 and abnormal in 28; of the 26 patients with EF < 50%, 24 had abnormal SPECT (p < 0.003). There was no significant change in mean EF after surgery (55% +/- 14% before vs 56% +/- 15% after). Thus simultaneous assessment of left ventricular perfusion and function after coronary artery bypass grafting showed that an abnormal perfusion pattern may exist despite a normal EF. These patients could not be predicted by enzymes or electrocardiographic changes.

99mTc-antimyosin antibody imaging for the detection of acute myocardial infarction in human beings

111In-antimyosin imaging is a highly sensitive and specific technique for the detection of myocardial necrosis. Two new methods of labeling antimyosin with 99mTc have been developed, and were compared with the standard 111In-antimyosin imaging technique in 29 patients with acute myocardial infarction. Fourteen patients (group I) received directly labeled 99mTc-antimyosin, and 15 (group II) were given RP-1 conjugated 99mTc-antimyosin. 99mTc-antimyosin imaging was performed at 6, 12, and 24 hours, and 111In-antimyosin imaging was done at 24 and 48 hours following injection. The images were interpreted by three blinded observers. In group I, 99mTc-antimyosin uptake could be detected in 3, 6, and 12 cases at 6, 12, and 24 hours, respectively, compared with only 8 cases at 24 hours with 111In-antimyosin. At 48 hours all patients showed 111In-antimyosin uptake. In group II, 99mTc-antimyosin uptake could be detected in 2, 3, and 6 cases at 6, 12, and 24 hours, respectively, compared with 8 and 12 cases at 24 and 48 hours, respectively, with 111In-antimyosin. Gated blood pool studies could be obtained in all patients following 99mTc-antimyosin injection and could be used to identify regional wall motion abnormalities. The plasma half-lives of 99mTc-antimyosin in group I and group II were 2.67 +/- 0.3 hours and 4.23 +/- 0.3 hours, respectively, and the plasma half-life of 111In-antimyosin was 6.3 +/- 0.4 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

What factors determine indium-111 antimyosin monoclonal antibody uptake in patients with myocardial infarction?

The intensity of indium-111 antimyosin monoclonal antibody uptake for visualization of myocardial infarction seems partially dependent on the state of the infarct related coronary artery. The aim of this study is to determine the factors which could account for the monoclonal antibody uptake variability. For this purpose, we investigated 27 patients (mean age 52.7 +/- 9.6 years) with a first proven myocardial infarction, by monoclonal antibody scintigraphy and coronary arteriography within the same period of time (7.12 +/- 6 days). The monoclonal antibody uptake was quantified by the heart/lung ratio on images recorded 24 h after injection. The infarct size was quantitatively estimated on wall motion analysis of twelve segments in 30 degree right anterior-oblique view with a radial method. The infarct related coronary artery state was assessed by the Thrombosis in Myocardial Infarction grade and the functional characteristics of collateral vessels by Rentrop's classification. These three variables as well as location of myocardial infarction, left ventricular ejection fraction, administration of a thrombolytic therapy, delay between myocardial infarction and monoclonal antibody scintigraphy were studied using non parametric test, or by linear regression method in order to determine whether these factors would influence the heart/lung ratio. None of these parameters except infarct size was related to heart/lung ratio. Consequently, monoclonal antibody uptake is only dependent on the extent of infarcted myocardium and the intensity of uptake cannot predict the patency of an infarct related coronary artery.

Cardiovascular applications: current status of immunoscintigraphy in the detection of myocardial necrosis using antimyosin (R11D10) and deep venous thrombosis using antifibrin (T2G1s)

The remarkable progress in immunologic techniques in the development of monoclonal antibodies offers the potential for powerful new tools for the detection of cardiovascular disorders, such as acute myocardial necrosis and acute deep venous thrombosis, in an accurate, safe, and noninvasive manner. Historically the use of monoclonal antibodies has been viewed as a tool dominated by the field of oncology. However, because of the relative ease of identifying and characterizing well-defined, unique antigens on necrotic cells, blood clots, and cellular components of the circulatory system, the chance for success in developing a clinically useful diagnostic product is significantly enhanced. In addition to being unique, these antigenic sites are also virtually universal in their expression by the targeted tissues or cells in the human population. Also, the epitope for these antibodies is less prone to "shedding" than many of the tumor markers present on the surface of malignant cells. This review describes the clinical experience with two immunoscintigraphic diagnostic agents specifically designed for the assessment of cardiovascular disorders resulting in the death of myocytes and the formation of acute blood clots indium-111 antimyosin-Fab-diethylenetriamine pentaacetic acid for the detection of myocardial necrosis and technetium-99m antifibrin Fab' (T2G1s) for the detection of acute venous thrombosis.

The use of antibodies in clinical cardiology

Monoclonal antibody technology has resulted in an entirely new class of agents, which have been applied to a variety of problems in cardiology and which hold great promise for future diagnostic, as well as therapeutic, applications. The four antibodies, which have been most widely used in clinical cardiology, are Digibind, OKT3, Myoscint, and 7E3. Each demonstrates the unique potential for the use of antibodies in clinical cardiology.

Quantification of antimyosin uptake and infarct size at various stages of myocardial infarction

We studied with quantitative techniques the clinical efficacy of indium-111 antimyosin at a later stage of myocardial infarction in 18 patients at various stages after infarction. Antimyosin accumulation was detected irrespective of infarct age and size and quantified as an infarct weight with a tomographic technique. Higher intensities in a planar image were observed in anterior Q wave infarct group (36 +/- 5 g) but not in inferior and non-Q wave anterior infarct groups because of the smaller infarct weights (8 +/- 3 g, 13 +/- 6 g, respectively). Infarct area calculated from thallium-201 tomography significantly correlated with left ventricular ejection fraction in both recent (less than 2 weeks) and older (2-week- to 6-month-old) infarct groups (r = -0.969, P less than 0.001; r = -0.860, P less than 0.001, respectively), whereas there was a significant negative correlation between infarct weight and left ventricular ejection fraction in the recent infarct group (r = -0.731, P less than 0.05) but not in the older infarct group. Thus, antimyosin tomography can detect myocardial necrosis with a high sensitivity regardless of infarct age, size, and location. However, the accumulation might be affected by infarct age and correspond to necrotic mass but not necessarily to infarct volume itself at a later stage probably because of the presence of necrosed and scarred tissues in infarcted myocardium.

Quantitative 111In antimyosin antibody imaging to predict the age of myocardial infarction

To establish whether quantitative 111In antimyosin uptake can be used to predict infarct age, we studied the heart-lung ratio in 107 images from 90 patients at various intervals following a Q-wave infarction. Imaging was performed 24 hours following 111In antimyosin injection. The HLR was measured as the ratio of the maximum counts in the infarcted myocardium to the adjacent lung background. The ratio ranged from 1.26 to 3.87, and declined with increasing infarct age. Infarcts were classified on the basis of age as type I (less than 3 days old), type II (less than 14 days), and type III (less than 90 days). True positive and false positive rates (TPR and FPR), and test-likelihood ratio calculations were performed for HLR thresholds ranging from 1 to 4, for the three infarct types. A FPR of 0% and likelihood ratio of infinity was obtained at a HLR threshold of 2.3 for type I infarcts (TPR 40.8%); at a HLR threshold of 2 for type II infarcts (TPR 50.6%), and a threshold of 1.8 for type III infarcts (TPR 52.6%). The likelihood of each infarct type can be estimated directly from the HLR for values below the above thresholds. These results show that quantitative 111In-antimyosin imaging may be used to predict infarct age.

Relation of technetium-99m pyrophosphate accumulation to time interval after onset of acute myocardial infarction as assessed by a tomographic acquisition technique

Technetium-99m pyrophosphate (Tc-99m PYP) myocardial scintigraphy was performed in 110 clinically stable patients with acute or healed acute myocardial infarction (AMI). Tomography was performed 12 hours to 7 days (group A), 7 to 30 days (Group B), 1 to 6 months (Group C) and after greater than 6 months (group D) after AMI. All 40 patients in group A, 9 of 31 in group B, 1 of 22 in group C, and no patient (0 of 17) in group D had a pathologic Tc-99m PYP tomogram. Relative Tc-99m PYP accumulation within the area of infarction was measured as infarct zone to blood pool ratio, which decreased significantly (p less than 0.001) from group A (1.54 +/- 0.39) to group B (0.89 +/- 0.24), group C (0.8 +/- 0.19) and group D (0.76 +/- 0.13). These data were confirmed by sequential scintigraphy in 17 patients. It is concluded that a persisting Tc-99m PYP uptake is rarely found greater than 1 month after AMI using tomographic imaging techniques in clinically stable patients with coronary artery disease. Positive results on Tc-99m PYP tomography are a reliable indicator of AMI. Thus, Tc-99m PYP tomography is not only a sensitive but also a specific imaging technique for AMI, which might be especially useful for diagnosis of reinfarction.

111In antimyosin antibody uptake is related to the age of myocardial infarction

The intensity of 111In antimyosin uptake is related to the type (Q wave or non-Q wave), size, and location of an acute myocardial infarction. To determine whether the uptake intensity is also related to the infarct age, and to establish the time frame during which 111In antimyosin uptake occurs postinfarction, we studied a quantitative measure of uptake intensity, the heart-lung (HL) ratio, in 90 consecutive patients at various intervals following a Q wave infarction. Imaging was performed 24 hours following 111In antimyosin injection. Uptake of antimyosin could be demonstrated up to 154 days postinfarction. The HL ratio was measured as the ratio of the maximum counts in the infarcted myocardium to the adjacent lung background, and was 1.93 +/- 0.51 (mean +/- SD) overall. The ratio declined exponentially with increasing age of infarct. Using nonlinear regression analysis, 47% of the total variance of the HL ratio could be attributed to age alone (p less than 0.001). Sequential antimyosin imaging was performed in nine patients, with the first study between 4 and 15 days, the second between 50 to 100 days, and the third between 125 to 270 days after the onset of chest pain. The HL ratios were (mean +/- SD) 1.77 +/- 0.25 for scans between 4 and 15 days, 1.54 +/- 0.12 for scans between 50 and 100 days (p less than 0.02), and 1.42 +/- 0.16 (p less than 0.05) for scans between 125 to 270 days, further establishing the progressive reduction in 111In antimyosin uptake with age of myocardial infarction.

Clinical role of indium-111 antimyosin imaging

Myocyte necrosis occurs in ischaemic, inflammatory and toxic heart diseases and can be detected by indium-111 antimyosin imaging. This allows a non-invasive evaluation of the site, extent and quantitation of the severity of myocardial necrosis. Simultaneous imaging of perfusion in patients with myocardial infarction allows the differentiation of necrosed and perfused areas and the varying degrees of mismatch and overlap, which has prognostic significance. 111In-antimyosin imaging is useful in the assessment of patients with unstable angina and in those for whom the diagnosis of infarction or unstable angina is not clear. In suspected myocarditis, a positive scan indicates the necessity for endomyocardial biopsy to confirm inflammation, whereas a negative scan makes the diagnosis of myocarditis unlikely. Antimyosin imaging is not useful as a marker of rejection in the 1 year post-transplant, but uptake after this period is associated with an increased rejection rate and is therefore an important tool in planning management strategies. Most patients on anthracycline treatment have demonstrable uptake, which is related to the cumulative dose and to the ejection fraction. Its role in this situation is as yet unclear. The use of new ligands and radioisotopes (99mTc) is likely to allow earlier imaging and produce improved quality.

Imaging of myocardial infarction in dogs and humans using monoclonal antibodies specific for human myosin heavy chains

The use of three different monoclonal antibodies specific for human ventricular myosin heavy chains in the visualization of the location and extent of necrosis in dogs with experimental acute myocardial infarction and in humans is described. Using a classic immunohistochemical method or ex vivo analysis of heart slices in dogs with acute myocardial infarction subjected to intravenous injection of unlabeled antimyosin antibodies or antimyosin antibodies labeled with indium-111, it was observed that all antibody fragments specifically reached the targeted necrotic zone less than 2 h after antibody injection and remained bound for up to 24 h. In a limited but significant number of cases (5 of the 12 humans and 11 of 43 dogs), it was possible to image the necrotic zone in vivo as early as 2 to 4 h after antibody injection. In other cases, individual blood clearance variations retarded or even prevented in vivo necrosis detection. Higher antimyosin fixation values were obtained in the necrotic zones in dogs with a rapid blood clearance relative to that of the other dogs. It is concluded that antimyosin antibodies always reached necrotic areas within 2 h. If blood clearance was rapid, in vivo imaging of the necrotic area was possible 2 to 6 h after necrosis, even in humans. In some cases, however, uncontrolled individual variations in the timing required for sufficient blood clearance hampered this rapid in vivo detection of myocardial necrosis.

Indium-111 myosin-specific antibodies and technetium-99m pyrophosphate in the detection of acute cardiac rejection of transplanted hearts: studies in a heterotopic rat heart model

111In-labelled myosin-specific antibodies were evaluated as an indicator of early changes in acute rejection in a rat heart heterotopic transplant model. Uptake of antibodies was measured in allograft and isograft hearts of animals undergoing different regimens of cyclosporine treatment and compared with the uptake of technetium-99m pyrophosphate. The data were correlated with histological estimation of the severity of myocyte necrosis and signs of early rejection (venous cuffing and endocardial inflammation, indicators of perivascular infiltrate and intermyocyte extension, respectively). Myocyte necrosis in transplanted hearts was reflected by increases in technetium-99m pyrophosphate accumulation (r = 0.88) but was poorly correlated with labelled antibody uptake (r = 0.58). There was no positive correlation between the degree of early cardiac rejection and uptake of either of the radiopharmaceuticals: accumulation of the labelled antibodies paradoxically declined with increased histological severity scores, whereas that of technetium-99m pyrophosphate remained unchanged. Cyclosporine treatment augmented the uptake of labelled antibodies in transplanted hearts. This may be due to alterations in plasma membrane permeability brought about by the drug, resulting in a rise in antibody binding to intracellular myosin.

Early Indium-111 antimyosin scintigraphy for assessment of regional wall motion asynergy on discharge after myocardial infarction

To assess the relation between early Indium-111 monoclonal antimyosin antibody scintigraphy and degree of regional asynergy on discharge, 38 patients with a first acute myocardial infarct were studied (18 anterior, 20 inferoposterior infarctions). In 21 patients thrombolytic therapy was administered. On the first day of myocardial infarction, 80 MBq Indium-111 Antimyosin was injected. Planar images, anterior, lateral and left anterior oblique, were made 24 hours later. Localized myocardial uptake was present in 37/38 patients, and was evaluated for Count Density Index (count density of infarct zone/left lung count density) in the left anterior oblique images, which displayed the infarct zone well. Regional asynergy on discharge was evaluated by cross-sectional echocardiography and defined mild (hypokinesia) or severe (akinesia or dyskinesia). Count density index was significantly lower in 15 patients with mild asynergy, compared with 22 patients with severe asynergy (1.61 +/- 0.25 vs. 2.42 +/- 0.40, p less than 0.001). This difference was present in both patient groups treated with or without thrombolysis. We conclude that early count density index, reflecting the amount of local necrosis, is highly correlated to the ultimate degree of wall motion impairment.

Pharmacokinetics of indium-111-labeled antimyosin monoclonal antibody in murine experimental viral myocarditis

The pharmacokinetics of indium-111-labeled antimyosin monoclonal antibody Fab were investigated with use of murine experimental viral myocarditis as a model. The biodistribution of indium-111-labeled antimyosin antibody Fab on days 3, 5, 7, 14, 21 and 28 after encephalomyocarditis virus inoculation demonstrated that myocardial uptake increased significantly on days 5, 7 and 14 (maximum on day 7) in infected versus uninfected mice (p less than 0.001). In vivo kinetics in infected mice on day 7 demonstrated that the heart to blood ratio reached a maximum 48 h after the intravenous administration of indium-111-labeled antimyosin Fab, which was considered to be the optimal time for scintigraphy. The scintigraphic images obtained with indium-111-labeled antimyosin Fab demonstrated positive uptake in the cardiac lesion in infected mice. The pathologic study demonstrated that myocardial uptake correlated well with pathologic grades of myocardial necrosis. High performance liquid chromatography revealed the presence of an antigen-antibody complex in the circulation of infected mice after the injection of indium-111-labeled antimyosin Fab. This antigen bound to indium-111-labeled antimyosin Fab in the circulation might be whole myosin and this complex may decrease myocardial uptake and increase liver uptake. It is concluded that indium-111-labeled antimyosin monoclonal antibody Fab accumulates selectively in damaged heart tissue in mice with acute myocarditis and that indium-111-labeled antimyosin Fab scintigraphy may be a useful method for the visualization of acute myocarditis.

Persistent uptake of indium-111-antimyosin monoclonal antibody in patients with myocardial infarction

Indium-111(111In)-antimyosin scintigraphy was investigated in 27 patients with myocardial infarction. 111In-antimyosin Fab was administered intravenously, and planar and single photon emission computed tomographic images were obtained 48 hours later. Uptake of 111In-antimyosin was present in 9 of 10 patients (90%) studied within 6 days of infarction. During the second week positive scans were seen in 16 of 16 patients (100%) including 13 (81%) who had normal creatine kinase levels. The mechanism of persistent positive antimyosin images in the subacute stage of myocardial infarction remains to be clarified. 111In-antimyosin scintigraphy may be useful as a noninvasive method for the detection of myocardial injury late and early after a suspected acute myocardial infarction.

Systemic pattern of free radical generation during coronary bypass surgery

Diffuse impairment of ventricular function after cardiac surgery may be related to the generation during reperfusion of the myocardium of free radicals derived from oxygen. Fifteen patients undergoing elective coronary bypass surgery were studied by previously described assays for peroxidised lipids and for isomerised lipids which were used as indices of free radical activity. Serial blood samples were obtained from systemic arterial, mixed venous, and coronary sinus catheters before, during, and after the ischaemic period. The patients underwent coronary artery surgery on cardiopulmonary bypass with a membrane oxygenator, relative hypothermia 30-34 degrees C, and intermittent cross-clamping of the aorta. During the ischaemic periods there were no significant changes in the indices of free radical activity. During the reperfusion phase there was a significant increase in free radical indices in arterial and mixed venous blood. A small rise in free radical indices in coronary venous blood was not statistically significant. These data indicate that free radical activity is increased in patients shortly after the cessation of cardiopulmonary bypass. The pattern of distribution between the different sampling sites suggests that much of the observed increase in isomerised and peroxidised lipids originates from tissues other than the myocardium.

Infarcted heart uptake and biodistribution of radiolabelled anti-myosin monoclonal antibody in rat and dog myocardial infarct models

A new mouse monoclonal antibody that recognizes alpha- and beta-heavy chains of human atrial and ventricular myosin and beta-heavy chain of human slow skeletal muscle myosin was obtained. The 125I- and 111In-labelled antibody, and its F(ab')2 and Fab fragments localize in isoproterenol induced infarcted rat heart, with the F(ab')2 fragment showing the highest uptake. Comparison with 99Tc-pyrophosphate uptake in infarcted dog heart, induced by selective obstruction of a coronary artery, suggest that the 111In-labelled F(ab')2 localizes specifically in infarcted myocardium only.

Dual isotope thallium and indium antimyosin SPECT imaging to identify acute infarct patients at further ischemic risk

Forty-two patients (28 men and 14 women) with acute myocardial infarction (35 Q, seven non-Q wave) were injected with 2.0 mCi indium 111-labeled antimyosin (AM) monoclonal antibody (111In AM) within 48 hours of the onset of chest pain. Forty-eight hours later (72-96 hours after onset of chest pain), patients were injected with 2.2 mCi thallium 201, and two sets of single-photon emission computed tomography (SPECT) images were obtained simultaneously using dual energy windows set for the 247 keV indium photopeak and the 70 keV thallium peak. Seventeen patients had repeat scans at 4 hours. 111In AM uptake and 201Tl defects were localized to one or more of 24 coronal and sagittal segments. Scans with only 201Tl defects and corresponding 111In AM uptake were classified as matches; scans with unmatched 201Tl defects in addition to matching regions corresponding to electrocardiographic infarct location were classified as mismatches; and scans with 201Tl and 111In AM uptake in the same segments were classified as overlap. Scan patterns were correlated with clinical evidence for residual ischemia occurring within 6 weeks of infarct and including infarct extension, recurrent angina, and positive predischarge low-level or 6-week symptom-limited stress tests and with coronary anatomy. Fourteen patients had only matching patterns (group 1), 23 had mismatches (group 2), and five had 201Tl-111In overlap as the predominant pattern. None of the patients in group 1 had previous myocardial infarction; in each, the matched area corresponded to the Q wave location on electrocardiogram, and none had further in-hospital ischemic events or positive stress tests.(ABSTRACT TRUNCATED AT 250 WORDS)

Predictive value of indium-111 antimyosin uptake for improvement of left ventricular wall motion after thrombolysis in acute myocardial infarction

In 21 patients treated with thrombolysis for acute myocardial infarction (AMI), the degree of myocardial uptake of indium-111 monoclonal antimyosin antibodies injected within 24 hours after onset of AMI was compared with the degree and extent of regional asynergy on admission and discharge, as assessed by 2-dimensional echocardiography. On the first day of AMI, 80 MBq of indium-111 antimyosin was injected and planar images were made 24 hours later. Indium-111 antimyosin uptake was evaluated for count density index (count density of infarct zone/left lung count density) in the left anterior oblique projection, in which the infarction zone was well displayed in all patients. Using 2-dimensional echocardiography, the left ventricle was divided into 13 segments and evaluated for regional asynergy, which was considered severe (akinesia or dyskinesia) or mild (hypokinesia). The extent of regional asynergy was measured by the number of asynergic segments. All 21 patients had severe regional asynergy on admission. Nine of 21 showed only mild regional asynergy on discharge and 12 of 21 had persistent severe regional asynergy in at least 1 segment. The count density index was significantly lower in patients with mild regional asynergy on discharge compared with patients with severe regional asynergy (1.63 +/- 0.27 vs 2.50 +/- 0.42, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)