Specificity of localization of myosin-specific antibody fragments in experimental myocardial infarction. Histologic, histochemical, autoradiographic and scintigraphic studies

Clinical Utilization of Multimodality Imaging for Myocarditis and Cardiac Sarcoidosis

Myocarditis is defined as inflammation of the myocardium according to clinical, histological, biochemical, immunohistochemical, or imaging findings. Inflammation can be categorized histologically by cell type or pattern, and many causes have been implicated, including infectious, most commonly viral, systemic autoimmune diseases, vaccine-associated processes, environmental factors, toxins, and hypersensitivity to drugs. Sarcoid myocarditis is increasingly recognized as an important cause of cardiomyopathy and has important diagnostic, prognostic, and therapeutic implications in patients with systemic sarcoidosis. The clinical presentation of myocarditis may include an asymptomatic, subacute, acute, fulminant, or chronic course and may have focal or diffuse involvement of the myocardium depending on the cause and time point of the disease. For most causes of myocarditis except sarcoidosis, myocardial biopsy is the gold standard but is limited due to risk, cost, availability, and variable sensitivity. Diagnostic criteria have been established for both myocarditis and cardiac sarcoidosis and include clinical and imaging findings particularly the use of cardiac magnetic resonance and positron emission tomography. Beyond diagnosis, imaging findings may also provide prognostic value. This case-based review focuses on the current state of multimodality imaging for the diagnosis and management of myocarditis and cardiac sarcoidosis, highlighting multimodality imaging approaches with practical clinical vignettes, with a discussion of knowledge gaps and future directions.

Liposomes for cardiovascular targeting

Liposome-based pharmaceuticals used within the cardiovascular system are reviewed in this article. The delivery of diagnostic and therapeutic agents by plain liposomes and liposomes with surface-attached targeting antibodies or polyethylene glycol to prolong their circulation time and accumulation at vascular injuries, ischemic zones or sites of thrombi are also discussed. An overview of the advantages and disadvantages of liposome-mediated in vitro, ex vivo and in vivo targeting is presented, including discussion of the targeting of liposomes to pathological sites on the blood vessel wall and a description of liposomes that can be internalized by endothelial cells. Diagnostic liposomes used to target myocardial infarction and the relative importance of liposome size, targetability of immunoliposomes and prolonged circulation time on the efficiency of sealing hypoxia-induced plasma membrane damage to cardiocytes are discussed as a promising approach for therapy. The progress in the use of targeted liposomal plasmids for the transfection of hypoxic cardiomyocytes and myocardium is presented. Stent-mediated liposomal-based drug delivery is also reviewed briefly.

Targeting the internal epitope of prostate-specific membrane antigen with 89Zr-7E11 immuno-PET

The potential of the positron-emitting (89)Zr has been recently investigated for the design of radioimmunoconjugates for immuno-PET. In this study, we report the preparation and in vivo evaluation of (89)Zr-desferrioxamine B (DFO)-7E11, a novel (89)Zr-labeled monoclonal antibody (mAb) construct for targeted imaging of prostate-specific membrane antigen (PSMA), a prototypical cell surface marker highly overexpressed in prostate cancer. The ability of (89)Zr-DFO-7E11 to delineate tumor response to therapy was also investigated, because it binds to the intracellular epitope of PSMA, which becomes available only on membrane disruption in dead or dying cells.

METHODS

7E11 as a marker of dying cells was studied by flow cytometry and microscopy of cells after antiandrogen-, radio-, and chemotherapy in LNCaP and PC3 PSMA-positive cells. The in vivo behavior of (89)Zr-DFO-7E11 was characterized in mice bearing subcutaneous LNCaP (PSMA-positive) tumors by biodistribution studies and immuno-PET. The potential of assessing tumor response was evaluated in vivo after radiotherapy.

RESULTS

In vitro studies correlated 7E11 binding with markers of apoptosis (7-amino-actinomycin-D and caspase-3). In vivo biodistribution experiments revealed high, target-specific uptake of (89)Zr-DFO-7E11 in LNCaP tumors after 24 h (20.35 ± 7.50 percentage injected dose per gram [%ID/g]), 48 h (22.82 ± 3.58 %ID/g), 96 h (36.94 ± 6.27 %ID/g), and 120 h (25.23 ± 4.82 %ID/g). Excellent image contrast was observed with immuno-PET. 7E11 uptake was statistically increased in irradiated versus control tumor as measured by immuno-PET and biodistribution studies. Binding specificity was assessed by effective blocking studies at 48 h.

CONCLUSION

These findings suggest that (89)Zr-DFO-7E11 displays high tumor-to-background tissue contrast in immuno-PET and can be used as a tool to monitor and quantify, with high specificity, tumor response in PSMA-positive prostate cancer.

Radionuclide noninvasive evaluation of heart failure beyond left ventricular function assessment

The management of patients with heart failure (HF) is challenging and requires the integration of clinical skills and accurate ancillary tests for the correct diagnosis and estimation of individual prognosis. Although the basic characterization of patients with HF is supported primarily by echocardiographic assessment of the left ventricular function, other noninvasive imaging procedures are being developed, including those involved in the processes of myocardial perfusion, metabolism, cellular injury, intersticial dysregulation, and neurohormonal receptor function. Nuclear techniques for molecular imaging of the myocardium may provide valuable insights into the pathophysiology, severity, management (medical/mechanical/surgical), response to treatment, and prognosis of HF patients. This will permit individualized management decisions and hopefully facilitate better clinical outcomes for patients with HF.

The La autoantigen is a malignancy-associated cell death target that is induced by DNA-damaging drugs

PURPOSE

To evaluate the La autoantigen as a target for specific monoclonal antibody (mAb) binding in dead cancer cells after use of DNA-damaging chemotherapy.

EXPERIMENTAL DESIGN

In vitro studies of La-specific 3B9 mAb binding to malignant and normal primary cells with and without cytotoxic drug treatment were done using immunoblotting and flow cytometry. Chromatin-binding studies and immunofluorescence detection of gammaH2AX as a marker of DNA double-stranded breaks together with 3B9 binding assays were done to measure DNA damage responses. Incorporation of a transglutaminase 2 (TG2) substrate and TG2 inhibition were studied to measure protein cross-linking in dead cells.

RESULTS

La was overexpressed in human cancer cell lines with respect to normal primary cells. Within 3 h of the DNA-damaging stimulus, La became chromatin bound when it colocalized with gammaH2AX. Later, after the stimulus produced cell death, La-specific 3B9 mAb bound specifically and preferentially in the cytoplasm of dead cancer cells. Moreover, 3B9 binding to dead cancer cells increased with increasing DNA damage. Both La and 3B9 became cross-linked in dead cancer cells via TG2 activity.

CONCLUSION

La autoantigen represents a promising cancer cell death target to determine chemotherapy response because its expression was selectively induced in dead cancer cells after DNA-damaging chemotherapy.

In vivo targeting of dead tumor cells in a murine tumor model using a monoclonal antibody specific for the La autoantigen

PURPOSE

To investigate the potential of the La-specific monoclonal antibody (mAb) 3B9 as an in vivo tumor-targeting agent.

EXPERIMENTAL DESIGN

The murine EL4 lymphoma cell line was used for in vitro studies and the EL4 model in which apoptosis was induced with cyclophosphamide and etoposide was used for in vivo studies. In vitro studies compared 3B9 binding in the EL4 cell with that in its counterpart primary cell type of the thymocyte. For in vivo studies, 3B9 was intrinsically or extrinsically labeled with carbon-14 or 1,4,7,10-tetra-azacylododecane-N,N',N'',N''''-tetraacetic acid-indium-111, respectively, and biodistribution of the radiotracers was investigated in EL4 tumor-bearing mice, which were treated or not with chemotherapy.

RESULTS

La-specific 3B9 mAb bound EL4 cells rather than thymocytes, and binding was detergent resistant. 3B9 binding to dead EL4 cells in vitro was specific, rapid, and saturable. Significantly, more 3B9 bound dead EL4 tumor explant cells after host mice were treated with chemotherapy, which suggested that DNA damage induced 3B9 binding. Tumor binding of 3B9 in vivo was antigen specific and increased significantly after chemotherapy. Tumor accumulation of 3B9 peaked at approximately 50% of the injected dose per gram of tumor 72 h after chemotherapy and correlated with increased tumor cell death. Tumor/organ ratios of 3B9 biodistribution, which included the tumor/blood ratio, exceeded unity 48 or more hours after chemotherapy.

CONCLUSIONS

La-specific mAb selectively targeted dead tumor cells in vivo, and targeting was augmented by cytotoxic chemotherapy. This novel cell death radioligand may be useful both for radioimmunoscintigraphy and radioimmunotherapy.

Noninvasive imaging in myocarditis

Increased recognition of the role of inflammation in acute and chronic dilated cardiomyopathy has revived an interest in noninvasive imaging for detection of myocarditis. Diagnostic strategies that are based on molecular imaging promise to further advance our understanding and improve diagnostic precision. This article reviews the strengths and limitations of common clinical tests used for the diagnosis of myocarditis, with a focus on the emerging role of cardiovascular magnetic resonance imaging. Novel imaging modalities that are currently in preclinical development are discussed with recommendations for future clinical research.

Recent approaches to intracellular delivery of drugs and DNA and organelle targeting

Intracellular delivery of various drugs, including DNA, and drug carriers can sharply increase the efficiency of various treatment protocols. However, the receptor-mediated endocytosis of drugs, drug carriers, and DNA results in their lysosomal delivery and significant degradation. The problem can be solved and therapy efficacy still further increased if the approaches for direct intracytoplasmic delivery that bypass the endocytic pathway are developed. This is especially important for many anticancer drugs (proapoptotic drugs whose primary action site is the mitochondrial membrane) and gene therapy (nuclear or mitochondrial genomes should be targeted). This review considers several current approaches for intracellular drug delivery: the use of pH-sensitive liposomes, the use of cell-penetrating proteins and peptides, and the use of immunoliposomes targeting intracellular antigens. Among intracellular targets, nuclei (gene therapy), mitochondria (proapoptotic cancer therapy and targeting of the mitochondrial genome), and lysosomes (lysosomal targeting of enzymes for the therapy of the lysosomal storage diseases) are considered. Examples of successful intracellular and organelle-specific delivery of biologically active molecules, including DNA, are presented; unanswered questions, challenges, and future trends are also discussed.

ATP-loaded immunoliposomes specific for cardiac myosin provide improved protection of the mechanical functions of myocardium from global ischemia in an isolated rat heart model

Earlier demonstrated cardio-protection by ATP-loaded liposomes (ATP-L) was further improved by attachment of cardiac myosin-specific monoclonal 2G4 antibody onto the surface of ATP-L. ATP-IL were infused for 1 min duration before starting the global ischemia for 25 min followed by reperfusion for 30 min in an isolated rat heart. The left ventricular developed pressure at the end of reperfusion in ATP-IL group significantly recovered to above 80% of the baseline compared to ca 25% in the Kreb's-Henseleit (KH) buffer, ca 60% in the IL, and ca 70% in the ATP-L treated groups. At the end of the reperfusion, left ventricular end diastolic pressure significantly reduced to 15 +/- 2 mmHg in ATP-IL group compared to 59 +/- 6 mmHg in the KH buffer, 31 +/- 4 mmHg in the IL and 23 +/- 3 mmHg in the ATP-L controls. The extent of preservation depended on the amount of the antibody present on the surface of the ATP-IL.

Value of radionuclide studies in cardiac transplantation

Effective noninvasive evaluation of acute and chronic allograft rejection remains an important challenge in patients with cardiac transplantation. Radionuclide studies have demonstrated utility because of their ease of use, giving relevant information about the pathophysiology of the transplanted heart, along with valuable diagnostic and prognostic indicators. This article focuses on reviewing the pathophysiological changes of the transplanted heart and implications for radionuclide studies.

First preclinical evaluation of mono-[123I]iodohypericin as a necrosis-avid tracer agent

PURPOSE

We have labelled hypericin, a polyphenolic polycyclic quinone found in St. John's wort (Hypericum perforatum), with( 123)I and evaluated mono-[(123)I]iodohypericin (MIH) as a potential necrosis-avid diagnostic tracer agent.

METHODS

MIH was prepared by an electrophilic radioiodination method. The new tracer agent was evaluated in animal models of liver infarction in the rat and heart infarction in the rabbit using single-photon emission computed tomography (SPECT), triphenyltetrazolium chloride (TTC) histochemical staining, serial sectional autoradiography and microscopy, and radioactivity counting techniques.

RESULTS

Using in vivo SPECT imaging, hepatic and cardiac infarctions were persistently visualised as well-defined hot spots over 48 h. Preferential uptake of the tracer agent in necrotic tissue was confirmed by perfect match of images from post-mortem TTC staining, autoradiography (ARX) and histology. Radioactivity concentration in infarcted tissues was over 10 times (liver; 3.51% ID/g in necrotic tissue vs 0.38% ID/g in normal tissue at 60 h p.i.) and over 6 times (myocardium; 0.36% ID/g in necrotic tissue vs 0.054% ID/g in normal tissue; ratios up to 18 for selected parts on ARX images) higher than in normal tissues.

CONCLUSION

The results suggest that hypericin derivatives may serve as powerful necrosis-avid diagnostic agents for assessment of tissue viability.

Site-specific conjugation of HIV-1 tat peptides to IgG: a potential route to construct radioimmunoconjugates for targeting intracellular and nuclear epitopes in cancer

PURPOSE

Our objective was to study the cellular and nuclear uptake of (123)I-mouse IgG ((123)I-mIgG) linked to peptides [GRKKRRQRRRPPQGYGC] harbouring the membrane-translocating and nuclear import sequences of HIV-1 tat protein.

METHODS

Carbohydrates on mIgG were oxidized by NaIO(4), then reacted with a 40-fold excess of peptides. Displacement of binding of anti-mouse IgG (Fab specific; alpha-mFab) to (123)I-mIgG by tat-mIgG or mIgG was compared. Internalization and nuclear translocation of (123)I-tat-mIgG in MDA-MB-468, MDA-MB-231 or MCF-7 breast cancer cells were measured. The immunoreactivity of imported tat-mIgG was evaluated by measuring binding of (123)I-alpha-mFab to cell lysate and by displacement of binding of (123)I-mIgG to alpha-mFab by cell lysate. Biodistribution and nuclear uptake of (123)I-tat-mIgG, (123)I-mIgG and (123)I-tat were compared in mice bearing s.c. MDA-MB-468 tumours.

RESULTS

There was a 15-fold decrease in affinity of alpha-mFab for tat-mIgG compared with mIgG. Internalized radioactivity imported into the nucleus for (123)I-tat-mIgG in MDA-MB-468, MDA-MB-231 and MCF-7 cells was 61.5+/-0.6%, 60.3+/-3.6% and 64.7+/-1.0%, respectively. The binding of (123)I-alpha-mFab to lysate from MDA-MB-468 cells importing tat-mIgG was 17-fold higher than that for cells not exposed to tat-mIgG. Imported tat-mIgG competed with tat-mIgG for displacement of binding of (123)I-mIgG to alpha-mFab. Conjugation of mIgG to tat peptides did not change tissue distribution. Nuclear localization for (123)I-tat-mIgG in MDA-MB-468 tumours was 28.1+/-5.6%, and for liver, spleen and kidneys it was 41.7+/-2.7%, 13.8+/-0.8% and 36.9+/-3.3%, respectively.

CONCLUSION

(123)I-tat-mIgG radioimunoconjugates suggest a route to the design of radiopharmaceuticals exploiting intracellular and nuclear epitopes.

Indium-111 monoclonal antimyosin cardiac scintigraphy in suspected acute myocarditis: evolution and diagnostic impact

BACKGROUND

This study examined the evolution of the heart to lung (H/L) ratio of monoclonal antimyosin antibody (MAA) uptake in patients with suspected acute myocarditis (AM) and its time-dependent diagnostic value in conjunction with echocardiographic findings.

METHODS

The study included 20 patients with a short history (<4 months) of heart failure symptoms and normal coronary arteries. All patients underwent cardiac antimyosin scintigraphy, echocardiography, right-heart catheterization and endomyocardial biopsy. Patients who survived beyond 1 year were reevaluated with a cardiac antimyosin scintigraphy and an echocardiographic study.

RESULTS

Endomyocardial biopsy in 8/20 patients revealed findings compatible with the diagnosis of idiopathic dilated cardiomyopathy (group I) and in the remaining 12/20 was diagnostic of AM (group II). At baseline evaluation of the antimyosin H/L ratio uptake was similar in groups I and II, at 1.95+/-0.19 and 2.16+/-0.51, respectively (P=0.222), while the left ventricular end diastolic diameter (LVEDd) was significantly higher in group I (68+/-12 mm) than in group II (56+/-11 mm, P=0.041). In these patients an initial positive MAA scintigraphy (H/L ratio>1.55) associated with an LVEDd<or=62 mm was diagnostic of AM with a sensitivity of 67%, a specificity of 63% and a positive predictive value of 65%. Upon restudy, the H/L ratio of MAA uptake was significantly decreased in both groups, reaching almost identical levels. No difference was found in the LVEDd between the two groups. The positivity of cardiac antimyosin scintigraphy in conjunction with an LVEDd<or=62 mm had a sensitivity of 45% and a specificity of 88% for the diagnosis of myocarditis.

CONCLUSIONS

In patients with suspected AM a positive antimyosin scintigraphy accompanied by a non-dilated left ventricle is highly suggestive of AM, both at the early phase and 1 year after disease onset.

Non-invasive in vivo imaging of myocardial apoptosis and necrosis

Myocardial necrosis plays an important role in the pathogenesis of various cardiovascular disorders and can result from different myocardial insults. Its non-invasive identification and localisation therefore may help in the diagnosis of these disorders, as well as in prognosis and assessment of treatment response. Apoptosis, or programmed cell death, is important in the spectrum of myocardial damage since it is gradually becoming more apparent that cell death may begin as apoptosis and not as necrosis. First attempts to directly visualise the area of myocardial necrosis were based on recognition of myocardial infarction with "hot spot imaging agents" in patients with chest pain. Since then, the study of myocardial necrosis with gamma imaging agents has gone beyond the detection of myocardial infarction, and attempts have been made to diagnose other cardiovascular disorders associated with cardiac cell death such as heart transplant rejection, myocarditis, cardiotoxicity and cardiomyopathies. Traditionally, two hot spot imaging agents have been used for the detection of myocardial necrosis, (99m)Tc-pyrophosphate and (111)In-antimyosin. In addition, preliminary studies have demonstrated promising results with (99m)Tc-glucarate. Recently, (99m)Tc-annexin V has been successfully used for non-invasive gamma imaging of apoptosis after acute myocardial infarction, acute myocardial ischaemia, acute cardiac allograft rejection and malignant intracardiac tumours. This review article focusses on the characteristics of these different myocardial necrotic and apoptotic markers and compares their role in the assessment of myocardial damage.

Coronary endothelial dysfunction and myocardial cell damage in chronic stable idiopathic dilated cardiomyopathy

Impairment of endothelium-dependent vasodilatation in response to acetylcholine reflects an abnormal endothelial function. Labelled indium-111 monoclonal antimyosin antibodies enable detection of myocardial cell damage. We analysed whether endothelial dysfunction correlates with myocardial antimyosin uptake in a selected group of patients with idiopathic dilated cardiomyopathy.

METHODS

Twenty-two consecutive patients with chronic stable idiopathic dilated cardiomyopathy (18 males and four females) were included. The duration of heart failure symptoms was 46+/-34 months. At inclusion, the functional class of New York Heart Association was 2.1+/-0.7. Endothelial function was evaluated using intracoronary graded concentrations of acetylcholine. Vasomotor responses of the left anterior descending coronary artery were measured by quantitative coronary analysis. Myocardial uptake of antimyosin antibodies was quantified by means of a heart-to-lung ratio (HLR).

RESULTS

Eighteen patients showed endothelial dysfunction (82%) and the remaining four patients showed a normal endothelial function. There were no statistically significant differences between patients with and without endothelial dysfunction in relation to clinical, echocardiographic and hemodynamic parameters. In addition, these variables did not correlate with the magnitude of the vasomotor response to acetylcholine. Eighteen patients (82%) showed abnormal antimyosin uptake; 15 of them (83%) showed endothelial dysfunction. The global mean HLR of antimyosin uptake was 1.73+/-0.24. The coronary vasomotor response to acetylcholine correlated with the intensity of uptake of antimyosin antibodies (r=-0.45, P<0.04).

CONCLUSIONS

Coronary endothelial dysfunction and myocardial antimyosin uptake was found in a high percentage of patients with chronic stable idiopathic dilated cardiomyopathy. The abnormal vasomotor response seems to be related to the degree of myocardial damage.

Drug targeting

The main problems currently associated with systemic drug administration are: even biodistribution of pharmaceuticals throughout the body; the lack of drug specific affinity toward a pathological site; the necessity of a large total dose of a drug to achieve high local concentration; non-specific toxicity and other adverse side-effects due to high drug doses. Drug targeting, i.e. predominant drug accumulation in the target zone independently on the method and route of drug administration, may resolve many of these problems. Currently, the principal schemes of drug targeting include direct application of a drug into the affected zone, passive drug targeting (spontaneous drug accumulation in the areas with leaky vasculature, or Enhanced Permeability and Retention-EPR-effect), 'physical' targeting (based on abnormal pH value and/or temperature in the pathological zone), magnetic targeting (or targeting of a drug immobilized on paramagnetic materials under the action of an external magnetic field), and targeting using a specific 'vector' molecules (ligands having an increased affinity toward the area of interest). The last approach provides the widest opportunities. Such pharmaceutical carriers as soluble polymers, microcapsules, microparticles, cells, cell ghosts, liposomes, and micelles have been successfully used for targeted drug delivery in vivo. Though the direct conjugation of a drug molecule with a targeted moiety is also possible (immunotoxin), the use of microreservoir-type systems provides clear advantages, such as high loading capacity, possibility to control size and permeability of drug carrier systems and use relatively small number of vector molecules to deliver substantial quantities of a drug to the target. The practical use of the listed systems and approaches for the delivery of therapeutic and diagnostic agents will be considered.

[The clinical practice guidelines of the Sociedad Española de Cardiología on cardiomyopathies and myocarditis]

Myocardial diseases are a extraordinarily heterogeneous group of processes that only have in common the fact that they involve heart muscle and that they cause a wide spectrum of myocardial dysfunction. The approach of the management and treatment of the cardiomyopathies is a continuous matter of discussion because the vast majority of alternatives in this field have not been based on the best scientific possible evidence and, since except for the case of heart failure associated with dilated cardiomyopathy. The majority of different options have not been studied by means of large (or even small) randomized trials. Nevertheless, this chapter has tried to provide the reader with different approaches on how to deal with important clinical problems in dilated, hypertrophic and restrictive cardiomyopathies, and in myocarditis as well. For this, we have utilized the most relevant information found coupled with our best clinical judgment, although we admit that many of the clinical recommendations can be controversial.

Indium-111 monoclonal antimyosin cardiac scintigraphy in men with idiopathic dilated cardiomyopathy

This study examined the prognostic value and the evolution of the heart-to-lung ratio of monoclonal antimyosin antibody (MAA) uptake in patients with a diagnosis of idiopathic dilated cardiomyopathy (IDC). Uptake of indium-111-labeled MAA occurs when the myocytes become irreversibly damaged. The study included 29 men with IDC followed up for 3 years. The diagnosis was verified by endomyocardial biopsy in all patients. Patients who survived beyond 1 year were restudied. Baseline heart-to-lung ratio of MAA was 1.74+/-0.22. Multivariate Cox regression analysis revealed that MAA and New York Heart Association class were independent predictors of late mortality, with a hazard ratio of 4.4 (95% confidence interval 1.1 to 17.9, p = 0.036) and 7.5 (95% confidence interval 2.0 to 28.4, p = 0.003), respectively, when heart-to-lung ratio of MAA uptake was > 1.74 and New York Heart Association class was >11. When these patients were divided into those with chronic IDC (group I [n = 19]) and those with subacute IDC (group II [n = 10]), baseline heart-to-lung ratio was 1.7+/-0.2 and 1.86+/-0.25, respectively (p = NS). In the surviving patients, on restudy, the heart-to-lung ratio of MAA uptake was unchanged in group I (1.64+/-0.20, p = NS), but had decreased to the level of group I (1.66+/-0.21 [p = 0.008]) in group II. Thus, men with IDC and a high heart-to-lung ratio of MAA uptake have a worse long-term prognosis than patients with a lower ratio. The heart-to-lung ratio of MAA decreases comparably over time in subacute IDC and remains stable in chronic IDC.

Scintigraphy and immunohistology of antimyosin-Fab during graft rejection

Up to now, the cellular localization pattern of monoclonal antimyosin antibodies (AMA) during acute rejection has not been described. Focused on this the authors made immunohistochemical and scintigraphic studies (AMS) with AMA in an animal transplantation model. Heterotopic cervical heart transplantation was performed in 12 mongrel dogs. Immunosuppression consisted of triple drug therapy. As standard the grafts were examined by daily transmural biopsies and routine histology. Dependent on the daily biopsy results, 0.5 mg of indium 111 ((111)In)-labeled AMA-Fab was injected. Subsequently every 2 hours transmural biopsy cylinders were taken out of the right ventricle and examined in indirect peroxidase staining technique. Forty-eight hours after AMA injection, scintigraphy in single photon emission computed tomography (SPECT) technique (AMS) was carried out and the heart-to-lung ratio (H/L-ratio) was calculated. The immunohistochemical maximum of AMA accumulation could be found 20 to 72 hours after AMA injection. This means that a scintigraphic examination should be done earlier than 20 hours and later than 3 days after injection. Dependent on the grades of bioptic rejection diagnosis a specific morphologic AMA localization was seen (grade I+II intercellular and slightly intracellular detection of AMA, grade III strongly intracellular and in particular perinuclear accumulation of the antibody, p<0.01). Moreover, the authors found a good correlation between scintigraphic H/L-ratio results and the corresponding histologic findings (grade I: H/L = 2.1 +/- 0.2; grade II: H/L = 3.1 +/- 0.2; grade III: H/L = 3.5 +/- 0.3; n = 19; p<0.02). The recently described positive AMS scans even in cases of mild rejection seem to be subject to an intercellular AMA localization. This typical AMA morphology during mild rejection favors the theory of the pore-forming protein allowing the efflux of myosin fragments as effector mechanism of cytotoxic lymphocytes in the early phase of acute rejection. The immunohistochemical AMA examination could explain the present discrepancy between positive AMS results of an intracellular protein in cases of mild or moderate acute rejection when visible cellular damage in the corresponding routine histology is absent.

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.

Myocardial damage assessed by indium-111-antimyosin: correlation with persistent enteroviral ribonucleic acid in dilated cardiomyopathy

The persistence of enteroviral ribonucleic acid (RNA) in the myocardium has been implicated as a pathogenetic factor in idiopathic dilated cardiomyopathy. Enteroviral persistence may lead to myocardial cell membrane damage, resulting in increased uptake of antimyosin antibodies. To further evaluate this hypothesis, a direct comparison of myocardial antimyosin uptake with the presence of enteroviral RNA was performed in ten patients (one female, nine male; 53+/-8 years) with chronic dilated cardiomyopathy. Planar antimyosin images were obtained 48 h after the injection of indium-111-labelled antimyosin Fab. Using a region of interest technique, the heart to lung uptake ratio (HLR) was calculated as a semiquantitative parameter of myocardial tracer uptake. Cardiac catheterization was performed to assess left ventricular function and to obtain myocardial biopsy samples. In the biopsy samples, gene amplification by polymerase chain reaction (PCR) was used to specifically detect enteroviral RNA. In the ten patients, the left ventricular ejection fraction was 39%+/-11% and the end-diastolic volume 131+/-46 ml/m2. The HLR was 1.72+/-0.21 and showed no correlation with functional parameters. In two patients with a positive PCR consistent with persisting enteroviral RNA, the HLR was not higher than that in eight patients with a negative PCR (1.46+/-0. 18 vs 1.78+/-0.18, respectively). These results suggest that increased uptake of 111In-antimyosin in chronic idiopathic dilated cardiomyopathy cannot be explained by pure persistence of enteroviral RNA. Other pathogenetic factors such as myocardial autoantibodies or microvascular spasm may be responsible for myocyte membrane damage detected by antimyosin.

Avidity of technetium 99m glucarate for the necrotic myocardium: in vivo and in vitro assessment

BACKGROUND

Similar to other 99mTc-based infarct-avid agents, 99mTc-glucarate localizes in myocardial infarcts. Whether severely ischemic viable myocytes sequester 99mTc-glucarate is uncertain. To assess the infarct specificity, in vitro and in vivo studies were performed.

METHODS AND RESULTS

H9C2 embryonic rat cardiocytes cultured under normoxia (N) or hypoxia (H) for 24 hours in 7.5 muCi 99mTc-glucarate were compared with necrotic cardiocytes. Mean H/N ratio (3.0 +/- 0.004, mean +/- SD) was significantly less than that of the necrotic/N ratio (39.9 +/- 6.5, p < 0.01). Reperfused myocardial infarction (MI) in 4 dogs confirmed by 201Tl (0.5 to 1.0 mCi) scintigraphy were imaged serially with simultaneously injected mixture of 99mTc-glucarate and 111In-antimyosin Fab. Infarcts were detected scintigraphically within 4 to 10 minutes with 99mTc-glucarate. 111In-antimyosin required more than 1 hour. Myocardial distribution at 5 hours showed a direct correlation between 99mTc-glucarate and 111In-antimyosin uptake (r = 0.99, p < 0.0001). Both 99mTc-glucarate (r = -0.777, p < 0.0001) and 111In-antimyosin (r = -0.775, p < 0.0001) were inversely related to 201Tl distribution.

CONCLUSIONS

The near perfect correlation between 99mTc-glucarate and 111In-antimyosin uptake (r = 0.99) in reperfused canine MI and the insignificant glucarate uptake by viable cardiocytes in vitro attest to the avidity of 99mTc-glucarate for the necrotic myocardium and favor its use as a specific early marker of myocyte necrosis in acute MI.

Antimyosin antibodies in cardiac rejection

The antimyosin antibody is often applied to find out scintigraphically whether myocarditis, myocardial infarction, or (recently) cardiac rejection is present. In the past, a lot of experimental work and clinical studies were done to determine its position, especially for the noninvasive detection of cardiac transplant rejection. Efforts are focused on comparing its diagnostic benefit with that of endomyocardial biopsy. The feasibility of rejection grading and diagnostic reliability are essential parts of this discussion. On the basis of large prospective clinical studies and the information from several experimental animal trials, some important findings can be assumed. Antimyosin scintigraphy after the application of indium 111-labeled antimyosin antibodies is a reliable tool to detect or exclude noninvasively cardiac rejection in adults and children. A distinction among three rejection intensities is possible, as confirmed by immunohistologic examinations. Antimyosin scintigraphy is an important noninvasive method for detecting cardiac rejection, with considerable advantages compared with endomyocardial biopsy.

Spectrum of alcohol-induced myocardial damage detected by indium-111-labeled monoclonal antimyosin antibodies

OBJECTIVES

We sought to determine the prevalence, intensity and evolving changes of myocardial damage detected by myocardial uptake of antimyosin antibodies in patients with alcohol-induced dilated cardiomyopathy, alcohol addicts attending a detoxification unit and healthy subjects with short-term alcohol consumption.

BACKGROUND

Evidence of alcohol-induced myocardial damage may be provided by myocardial uptake of indium-111-labeled monoclonal antimyosin antibodies. The spectrum of such damage in patients who are heavy drinkers (> 100 g for > 10 years), with or without cardiomyopathy, and the impact of short-term alcohol ingestion on antimyosin antibody uptake have not been adequately explored.

METHODS

One hundred twenty antimyosin studies were performed in 56 patients with dilated cardiomyopathy (group I), 15 alcohol addicts attending a detoxification unit (group II) and 6 volunteers for short-term alcohol ingestion (group III). Estimation of antibody uptake was calculated through a heart/lung ratio (HLR) (normal < 1.55).

RESULTS

The 56 patients in group I (54 men, 2 women; mean [+/-SD] age 46 +/- 11 years) had consumed 123 +/- 60 g/day of alcohol for 21 +/- 9 years, for a cumulative intake of 914 +/- 478 kg. Mean duration of symptoms was 46 +/- 49 months. Mean left ventricular end-diastolic diameter was 71 +/- 10 mm, and mean ejection fraction was 28 +/- 12%. No differences in New York Heart Association functional class, ventricular size or ejection fraction were noted between 28 active and 28 past consumers, except for the prevalence and intensity of antibody uptake (75% vs. 32%, p < 0.001) and HLR (1.75 +/- 0.26 vs. 1.49 +/- 0.17, p = 0.0001). In 19 patients in the active group restudied after alcohol withdrawal, antibody uptake decreased (from 1.76 +/- 0.17 to 1.55 +/- 0.19, p < 0.001), and ejection fraction improved (from 30 +/- 12% to 43 +/- 16%, (p < 0.001). No changes occurred in the 15 past consumers restudied. The 15 male patients in group II (mean age 36 +/- 4 years) had consumed 156 +/- 59 g/day for 17 +/- 5 years, for a cumulative alcohol intake of 978 +/- 537 kg, an amount similar to that in patients in group I, but antimyosin antibody uptake was detected in only 3 (20%) of 15 patients. None of six group III subjects developed antibody uptake after short-term ethanol ingestion. Despite the small sample size, the power to detect clinically relevant differences in most variables that did not reach statistical significance was amply sufficient.

CONCLUSIONS

In alcohol-induced dilated cardiomyopathy, alcohol withdrawal is associated with the reduction or disappearance of myocardial damage and improvement of function. The difference in prevalence of antimyosin antibody uptake in patients with and without cardiac disease who consume similar amounts of alcohol suggests the presence of those with different myocardial susceptibilities to alcohol. Short-term ethanol ingestion in healthy subjects does not induce detectable uptake of antimyosin antibodies.

Poly(ethylene glycol)-coated anti-cardiac myosin immunoliposomes: factors influencing targeted accumulation in the infarcted myocardium

Biodistribution and infarct accumulation of different liposome preparations in rabbits with experimental myocardial infarction have been investigated. The influence of such parameters as liposome size, and presence or absence of poly(ethylene glycol) (PEG) and infarct-specific antimyosin antibody (AM) on liposome behavior in vivo was studied. All three variables were shown to affect liposome biodistribution, liposome size being the least significant variable. Statistical analysis of the data obtained demonstrated that of all variables, PEG coating expresses the strongest influence on the liposome blood clearance, significantly (P=0.0001) increasing the mean level of blood radioactivity under all circumstances. Infarct accumulation depended upon the presence of both PEG (P=0.0013) and AM (P=0.005). The infarct-to-normal ratio was affected by the presence of AM (P=0.0002), but the extent of the effect depended also on the presence of PEG (P=0.01). Two differing mechanisms can be seen in infarct accumulation of PEG-liposomes (slow accumulation via the impaired filtration) and AM-liposomes (specific binding of immunoliposomes with the exposed antigen). Both mechanisms are supplementary in case of liposomes carrying PEG and AM at the same time. An optimization strategy is suggested for using liposomes as carriers for diagnostic (a high target-to-nontarget ratio is required) and therapeutic (a high absolute accumulation in the target is required) agents.

Natural evolution of antimyosin scan and cardiac function in patients with acute myocarditis

Indium-111 monoclonal antimyosin antibody imaging is a convenient method to diagnose acute myocarditis. The present study examined the natural evolution of a positive antimyosin scan in 10 patients with acute myocarditis, in relation to left ventricular ejection fraction. All patients underwent myosin-specific monoclonal antibody imaging and radionuclide ventriculography; in all patients endomyocardial biopsy was performed. Repeat assessment of left ventricular function and antimyosin uptake was performed 1, 2 and 6 months later. A heart-to-lung ratio was used to quantify antimyosin uptake. Heart-to-lung ratio in patients with myocarditis was 2.12 +/- 0.31, significantly higher than that observed in eight controls (1.35 +/- 0.08, P < 0.001). During follow-up 2.2 repeat scans per patient were performed. Heart-to-lung ratio normalized (< 1.6) within 1 month in four patients, within 2 months in one patient and within 6 months in two patients; three patients continued to have a positive antimyosin uptake at 6 months, suggesting ongoing myocardial necrosis. At the end of follow-up, ejection fraction improved by > 5% in four patients; normalization or persistence of tracer uptake could not predict an improvement of ejection fraction. It is concluded that antimyosin scintigraphy is useful for diagnosing myocarditis in its subacute or chronic stage during which unknown or immune mechanisms may be in operation. An improvement in left ventricular function cannot be predicted on the basis of persistence or not of tracer uptake.

Plug and seal: prevention of hypoxic cardiocyte death by sealing membrane lesions with antimyosin-liposomes

The hallmark of cell death is the development of cell membrane lesions. Such lesions in the myocardium are usually associated with acute myocardial infarction. Minimizing myocardial necrosis by thrombolytic reperfusion therapy constitutes the only major treatment to date. We envisioned a method to seal these membrane lesions using immunoliposomes as a novel adjunctive approach. An antigen to intracellular cytoskeletal myosin in hypoxic embryonic cardiocytes is used as an anchoring site, and a specific antibody on immunoliposomes as the anchor to plug and to seal the membrane lesions. H9C2 cells were used because they are cardiocytes and are propagated in tissue culture and their viability may be assessed by various methods. Viability assessed by [3H]thymidine uptake in hypoxic cardiocyte cultures (n = 6 each) treated with antimyosin-immunoliposomes (3.26 +/- 0.483 x 10(6) c.p.m.) was similar to that of normoxic cells (3.68 +/- 0.328 x 10(6) c.p.m.), but was greater than those of untreated hypoxic cells (0.115 +/- 0.155 x 10(6) c.p.m.) or hypoxic cells treated with plain liposomes (1.140 +/- 0.577 x 10(6) c.p.m.). These results were reconfirmed by trypan blue exclusion and by fluorescent, confocal and transmission electron microscopy. They indicated that cell death in hypoxic cardiocytes can be prevented by targeted cell membrane sealing. This concept of cell salvage should be applicable in the prevention of cell death in different biological systems.

Detection of microinfarction in patients with unstable angina: study by 111In-antimyosin imaging

To examine the incidence of a positive indium-111 antimyosin scintigraphy in patients with unstable angina, we prospectively examined 25 patients with unstable angina and 11 patients with stable angina. All patients were injected with 2 mCi of indium-111 on admission and planar scintigraphy was performed 48 h later. Symptoms and signs of ischemia indicating severity of ischemia were monitored during the period between injection and scanning. None of the patients developed a rise in cardiac enzymes suggesting myocardial necrosis. Seven (28%) of the 25 patients with unstable angina had positive antimyosin scanning; no stable patients had positive scanning. All seven patients with unstable angina and positive scanning had signs of severe ischemia (four patients had multiple episodes of > 2/day, three patients had prolonged episodes of > 15 min, three patients had ST depression in > 3 EKG leads) while only one of the eighteen unstable patients with negative scannings had signs of severe ischemia (P < 0.001). In conclusion, (1) a significant number of unstable angina patients present positive antimyosin scanning without an elevation of cardiac enzymes and (2) these patients usually present multiple or severe episodes of ischemia indicating that during these episodes, minor myocardial necrosis, undetected by enzymes, may occur.

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.

Scintigraphic detection of inflammatory heart disease

Inflammatory diseases of the heart encompass myocarditis, endocarditis and pericarditis. This paper discusses the diagnostic potential of scintigraphy in these entities. In myocarditis, indium-111 antimyosin Fab imaging can visualize active myocyte damage and thus contribute substantially to the diagnosis. Antimyosin uptake is also seen in a large subset of patients with dilated cardiomyopathy, indicating ongoing myocyte injury in these cases. In endocarditis, immunoscintigraphy using monoclonal technetium-99m-labelled antigranulocyte antibodies provides useful diagnostic information in patients with equivocal echocardiographic findings. Immunoscintigraphy seems to indicate the floridity of the inflammatory process in endocarditis and may be used to monitor antibiotic therapy. In pericarditis, the clinical value of scintigraphy has not been convincingly demonstrated.

Transcapillary exchange of indium 111-labeled anticardiac myosin Fab and thallium 201 in isolated reperfused rabbit hearts

BACKGROUND

The physiologic mechanisms of 111In-labeled anticardiac myosin antibody [111In]-AM) imaging are fairly well established. However, to better understand the transcapillary exchange characteristics of normal and reperfused myocardium, a standard first-pass, indicator-dilution analysis was undertaken in hearts subjected to global no-flow and low-flow ischemia.

METHODS AND RESULTS

The first-pass myocardial transport of 201Tl and [111In]-AM was evaluated in an in vitro rabbit model of no-flow ischemia/reperfusion with indicator-dilution analysis during normal and ischemic flows and whole-blood perfusate. The maximum extraction fraction (Emax) of 201Tl was dominated by flow rate as expected and averaged 0.75 (+/- 0.009) and 0.57 (+/- 0.008) during ischemic and normal flows, respectively (p < 0.01). Emax values for [111In]-AM, which were 0.02 or less in all hearts at control, increased to 0.06 or greater at moderate to longer perfusion times after 50 or more minutes of no-flow ischemia. Permeability surface area (in milliliters per minute per gram) tended to decline for 201Tl with longer reperfusion periods in both ischemic and normal flow groups and paralleled the changes observed for Emax for [111In]-AM.

CONCLUSIONS

These data demonstrate that the first-pass extraction of [111In]-AM is quite low in this model of acute coronary occlusion and reflow and enhanced only in severe ischemia-reperfusion treatment. Therefore in this model there appears to be no significant [111In]-AM uptake in either normal or mildly ischemic myocardium. Consequently, [111In]-AM uptake into myocardium must depend on tracer recirculation, as well as sarcolemmal cell wall disruption, to achieve specific and sufficient [111In]-AM uptake for localization of clinical imaging.

Investigation of tumor invasion with [111In]antimyosin

Accumulation of [111In]antimyosin in various types of tumors has been reported. In order to test the possibility that the destruction of muscle tissue by tumor invasion could induce high uptake of [111In]antimyosin, we investigated the distribution of [111In]antimyosin in tumor and muscle using autoradiography (ARG). High uptake of [111In]antimyosin was observed both in rabbit papilloma VX2 and rat hepatoma AH109A by scintigraphy and tissue distribution studies, and its concentration was found to be highest at the periphery and outer surface of the tumors using whole-body ARG. However, in micro- and macro-ARG, high grain density was observed in granulation tissue with macrophage infiltration between the tumor and muscle, not in the muscle tissue invaded by tumor cell. Significant non-specific accumulation of [111In]antimyosin in inflammatory tissue surrounding the tumor was suggested.

Antimyosin scintigraphy for detection of myocarditis. Scintigraphic follow-up

To examine the value of antimyosin-indium 111 imaging in relation to endomyocardial biopsy in patients with suspected myocarditis, as well as the natural evolution of abnormal findings on the antimyosin scan, 12 patients with suspected myocarditis underwent endomyocardial biopsy and antimyosin scan. The heart-to-lung ratio (H/L) was used to quantify the antimyosin scan. All 12 patients had abnormal results on the scan (H/L, 1.7 to 2.9; mean, 2.1 +/- 0.3); 8 of the 12 patients also had a diagnostic endomyocardial biopsy. In four patients with abnormal findings on antimyosin scan and normal findings on biopsy, the H/L ratio did not differ from eight patients with abnormal findings on antimyosin scan and a diagnostic biopsy; also, the ejection fraction did not differ between the two groups. One patient died, and 8 patients had a repeat antimyosin scan within 2 months after the initial study. The H/L ratio returned to normal in two out of three patients with normal results on biopsy and in three out of five patients with a diagnostic biopsy; the ejection fraction improved by 8 percent or more in one out of three patients with a nondiagnostic biopsy and in two out of five patients with a biopsy diagnostic for myocarditis. We conclude that the antimyosin scan is more frequently diagnostic than biopsy in suspected myocarditis. Patients with abnormal results on antimyosin scan and a nondiagnostic biopsy, as well as those with abnormal results on antimyosin scan and a diagnostic biopsy, tend to return to normal results on scan within 2 months and improve their ejection fraction.

Reperfusion injury after myocardial infarction: the role of free radicals and the inflammatory response

Development of thrombolytic therapy as a treatment for myocardial infarction has focused attention on the events that occur upon reperfusion of ischemic myocardial tissue. Although it is well documented that salvage of the ischemic myocardium is dependent upon timely reperfusion, it is likely that the very events critical for survival may, in fact, lead to further tissue injury. A widely recognized source of reperfusion injury is the generation of oxygen-derived free radicals. These reactive oxygen species, which are formed within the first moments of reperfusion, are known to be cytotoxic to surrounding cells. In addition, strong support exists for the involvement of the inflammatory system in mediating tissue damage upon reperfusion. Coincident with the recruitment of neutrophils and activation of the complement system is an increase in the loss of viable cells. Although a number of mechanisms are likely to be involved in reperfusion injury, this discussion focuses on the roles that oxygen-derived free radicals and the inflammatory system play in mediating reperfusion injury.

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.

Active myocardial damage without attending inflammatory response in dilated cardiomyopathy

OBJECTIVES

This study aimed to compare indium-111 (111In)-monoclonal antimyosin antibody uptake in patients with dilated cardiomyopathy before heart transplantation with the histologic findings in the explanted hearts.

BACKGROUND

A high prevalence of 111In-monoclonal antimyosin antibody uptake has been described in patients with dilated cardiomyopathy, suggesting the presence of active, ongoing myocyte damage; however, no correlation between monoclonal antimyosin antibodies and histologic findings is available in these patients.

METHODS

A consecutive series of 21 patients with dilated cardiomyopathy awaiting heart transplantation were studied with monoclonal antimyosin antibodies before the operation, and the results were compared with the histologic analysis of the explanted hearts. The interval between monoclonal antimyosin antibody studies and transplantation was 1 to 90 days (mean 58 +/- 31).

RESULTS

Using a semiquantitative method (heart/lung ratio), monoclonal antimyosin antibody uptake was present in 15 (71%) of 21 patients, but active myocarditis in the explanted hearts was detected in only 7. In 11 patients, intense monoclonal antimyosin antibody uptake coexisting with absent myocyte damage or cellular infiltration of explanted hearts was noted. One patient who showed preoperative monoclonal antimyosin antibody uptake underwent transplantation 11 h later, and ex vivo diffuse myocardial antimyosin uptake was detected, but active myocarditis was seen only at cardiectomy in only a small area of the heart; the rest of the myocardium showed no signs of myocyte damage.

CONCLUSIONS

In dilated cardiomyopathy, monoclonal antimyosin antibody uptake cannot be equated with the presence of an inflammatory response detected in the myocardium of the explanted heart.

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.

New application of myocardial antimyosin scintigraphy: diagnosis of myocardial disease in polymyositis

Heart disease is a rare but important complication of polymyositis. Diagnosis of myocardial disease is usually based on non-specific clinical, electrocardiographic, and echocardiographic data. This paper reports a case of polymyositis with myocardial disease diagnosed by myocardial imaging with radiolabelled antibody to myosin, a specific marker of the necrotic myocardial fibre.

Blood flow-dependent uptake of indium-111 monoclonal antimyosin antibody in canine acute myocardial infarction

OBJECTIVES

The relation of myocardial blood flow and indium-111 (111In) antimyosin antibody uptake was studied by inducing myocardial infarction in 18 dogs, 8 with closed chest left anterior descending artery balloon occlusion for 3 h followed by reperfusion (group A) and 10 dogs with open chest left anterior descending artery ligation (without reperfusion, group B).

BACKGROUND

The relation of antimyosin uptake to myocardial injury has been documented. However, its relation to tracer delivery by myocardial blood flow has not been studied and has been assumed to be independent.

METHODS

Indium-111 antimyosin antibody, 2 mCi, was injected 20 min after reperfusion and 3 h after coronary artery ligation in groups A and B, respectively. Regional blood flows were determined by radiolabeled microspheres during occlusion and 24 h later in both groups. On day 2, dogs were killed after risk zone delineation with gentian violet. The heart was excised and stained with triphenyltetrazolium chloride solution and graded for increasing severity of tissue injury based on extent of staining. Microsphere activity and 111In antimyosin activity were measured in control tissue (grade 1), noninfarct tissue at risk (grade 2), mixed tissue (grade 3), infarct tissue (grade 4) and hemorrhagic infarct tissue (grade 5, present only in group A dogs). Count activity was normalized to that of the mean value in control tissue (grade 1) and expressed as a ratio of activity.

RESULTS

Indium-111 antimyosin activity was high in triphenyltetrazolium chloride grade 4 tissue in both groups but was attenuated in grade 4 tissue in group B dogs (10.6 +/- 5.1 vs. 5.0 +/- 4.5; p < 0.05 group A vs. group B), which had lower blood flow on day 2 (0.51 +/- 0.36 vs. 0.23 vs. 0.22; p < 0.01). Normalizing 111In antimyosin activity for blood flow on day 2 resulted in equivalent 111In antimyosin uptake for infarct tissue (32.6 +/- 21.6 vs. 36.6 +/- 29.8 for group A vs. group B; p = NS).

CONCLUSIONS

Thus, 111In antimyosin uptake is a specific marker of necrotic tissue with a high signal ratio in reperfused tissue. However, its uptake is dependent on residual blood flow in the infarct territory. Indium-111 antimyosin could potentially serve as a suitable tracer for infarct sizing if myocardial blood flow in the same region were factored simultaneously.

Indium-111-labelled antimyosin antibody imaging in a patient with cardiac sarcoidosis

The aetiology of cardiac dysfunction caused by sarcoid granulomatous inflammation may be difficult to clarify, and the potential of imaging methods is limited. We report on a patient who presented with acute biventricular decompensation. Pulmonary sarcoidosis was confirmed after hospitalization. Four weeks after the initiation of corticosteroid treatment, scintigraphy with indium-111-labelled antimyosin antibody Fab fragments (AMAB) revealed distinct activity accumulation in major parts of the left ventricular wall (heart-lung ratio: 1.6) 72 h following injection. There may be a role for AMAB scintigraphy in the early detection of cardiac sarcoidosis.