Scintigraphic quantification of myocardial necrosis in patients after intravenous injection of myosin-specific antibody

Imaging doxorubicin and polymer-drug conjugates of doxorubicin-induced cardiotoxicity with bispecific anti-myosin-anti-DTPA antibody and Tc-99m-labeled polymers

BACKGROUND

Radiolabeled anti-myosin imaging is well-established for imaging doxorubicin-induced cardiotoxicity. However, to enable imaging of drug-induced cardiotoxicity in small experimental animals, pretargeting with bispecific anti-myosin-anti-DTPA-Fab-Fab' and targeting with high-specific radioactivity Tc-99m-DTPA-succinylated-polylysine (DSPL) was developed.

METHODS

Mice were injected biweekly with 10 mg/kg Dox or its equivalent as D-Dox-PGA. Tc-99m-DSPL myocardial activity after pretargeting with bsAb-Fab-Fab' was determined after gamma imaging performed at day 7 for Dox-treated mice and day 39 for all others.

RESULTS

Mice treated with 10 mg/kg Dox lost 10% total body weight in 1 week and 20% after a second dose. Pretargeted mice treated with 30 mg/kg cumulative D-Dox-PGA dose showed no loss of body weight for the duration of the study. Cardiotoxicity was confirmed by gamma imaging and scintillation counting (1.9 ± 0.25 [mean% ID/g ± SD]) after 1 dose of Dox. Mice injected with 3 × 10 mg/kg Dox equivalent as D-Dox-PGA (0.4 ± 0.04, P < .01) and untreated 2 control groups (0.20 ± 0.05 and 0.19 ± 0.04, P < .01) showed significantly lower myocardial anti-myosin radioactivity relative to the 10 mg/kg Dox group.

CONCLUSION

Pretargeting with bsAb-Fab-Fab' and targeting with Tc-99m labeled high-specific activity polymers enabled early visualization of doxorubicin induce cardiotoxicity in mice. Tolerated dose of D-Dox-PGA was greater than to 30 mg/kg Dox-equivalent dose with minimal cardiotoxicity.

Molecular Imaging in Ischemic Heart Disease

Purpose of Review

The purpose of this paper is to review current and new modalities to image key biological processes in ischemic heart disease and after myocardial infarction non-invasively.

Recent Findings

New imaging targets have been developed to detect and quantify myocardial damage after ischemia. Although positron emission tomography (PET) has been leading the development of new probes in the past, continuous improvements of magnetic resonance imaging (MRI) together with the development of new novel MRI contrast agents opens new research avenues including the combination of both PET and MRI to obtain anatomic, functional, and molecular information simultaneously, which is not possible from a single imaging session.

Summary

This review summarizes the state of art of non-invasive molecular imaging of the myocardium during ischemia and after myocardial infarction using PET and MRI. We also describe the different contrast agents that have been developed to image the different phases of cardiac healing and the biological processes associated with each of those phases. Importantly, here we focus on imaging of inflammation as it is the key biological process that orchestrates clearance of dead cells, tissue remodeling, cardiac repair, and future outcome. We also focus on clinical translation of some of the novel contrast agents that have been tested in patients and discuss the need for larger, multi-center patient studies to fully validate the applicability of new imaging probes.

Evaluation of Radioiodinated 1,4-Naphthoquinones as Necrosis Avid Agents for Rapid Myocardium Necrosis Imaging

PURPOSE

Identifying necrotic myocardium in ischemic regions is of great importance for risk stratification and clinical decision-making. However, rapid noninvasive imaging of necrotic myocardium is still challenging. This study sought to evaluate the potential of 1,4-naphthoquinones to rapidly visualize necrotic myocardium and the possible mechanisms of necrosis avidity.

PROCEDURES

Six 1,4-naphthoquinones were radiolabeled with iodine-131 and the necrosis avidity was estimated in mouse models with muscular necrosis by gamma counting and autoradiography. The necrotic myocardium imaging property and biodistribution of [¹³¹I]naphthazarin (6) were determined in rat models with re-perfused myocardial infarction. A possible mechanism of necrosis avidity was explored by in vitro DNA-binding and in vivo blocking experiments.

RESULTS

The radiochemical purities of the six radiotracers were greater than 95 %. The uptakes in necrotic muscles of all six radiotracers were higher than those in viable muscles, and [¹³¹I]naphthazarin (6) showed the highest necrotic-to-viable ratio and necrosis-to-blood ratio at all tested time points. The necrotic myocardium could be clearly visualized by single-photon emission computed tomography/x-ray computed tomography (SPECT/CT) using [¹³¹I]naphthazarin (6) as early as 3 h post-injection. Post-mortem biodistribution showed the uptake of [¹³¹I]naphthazarin (6) in necrotic myocardium was 11.67-fold higher than that in viable myocardium. Absorption spectra and emission spectra suggested naphthazarin (6) could bind to DNA through intercalation. The uptake of [¹³¹I]naphthazarin (6) in necrotic muscle could be significantly blocked by excessive ethidium bromide (a typical DNA intercalator) and cold naphthazarin (6) with 63.49 and 71.96 % decline at 3 h post-injection in vivo, respectively.

CONCLUSIONS

1,4-Naphthoquinones retained necrosis avidity and [¹³¹I]naphthazarin (6) rapidly visualized necrotic myocardium. The necrosis avidity mechanism of [¹³¹I]naphthazarin (6) may be attributed to its binding with exposed DNA in necrotic tissues.

Experimental evaluation of radioiodinated sennoside B as a necrosis-avid tracer agent

Necrosis-avid agents are a class of compounds that selectively accumulate in the necrotic tissues after systemic administration, which can be used for in vivo necrosis imaging and targeted therapies. In order to search for a necrosis-avid tracer agent with improved drugability, we labelled iodine-131 on sennoside B (SB) as a naturally occurring median dianthrone compound. The necrosis targetability and clearance properties of (131)I-SB were evaluated in model rats with liver and muscle necrosis. On SPECT/CT images, a "hot spot" in the infarcted liver lobe and necrotic muscle was persistently observed at 24 h and 72 h post-injection (p.i.). Gamma counting of the tissues of interest revealed a radioactivity ratio of necrotic to viable liver at 4.6 and 3.4 and of necrotic to viable muscle at 7.0 and 8.8 at 24 h and 72 h p.i., respectively. The good match of autoradiographs and fluoromicroscopic images with corresponding histochemical staining suggested preferential uptake of (131)I-SB in necrotic tissue. Pharmacokinetic study revealed that (131)I-SB has an elimination half-life of 8.6 h. This study indicates that (131)I-SB shows not only prominent necrosis avidity but also favourable pharmacokinetics, which may serve as a potential necrosis-avid diagnostic agent for assessment of tissue viability.

Molecular MRI of acute necrosis with a novel DNA-binding gadolinium chelate: kinetics of cell death and clearance in infarcted myocardium

BACKGROUND

Current techniques to image cell death in the myocardium are largely nonspecific. We report the use of a novel DNA-binding gadolinium chelate (Gd-TO) to specifically detect the exposed DNA in acutely necrotic (ruptured) cells in vivo.

METHODS AND RESULTS

In vivo MRI was performed in 20 mice with myocardial infarction (MI). The mice were injected with Gd-TO or Gd-DTPA at varying time points after MI. MRI was performed 2 hours after probe injection, to avoid nonspecific signal from the late gadolinium enhancement effect. Cell rupture (Gd-TO uptake) was present within 2 hours of infarction but peaked 9 to 18 hours after the onset of injury. A significant increase in the longitudinal relaxation rate (R(1)) in the infarct was seen in mice injected with Gd-TO within 48 hours of MI, but not in those injected more than 72 hours after MI (R(1)=1.24±0.08 and 0.92±0.03 s(-1), respectively, P<0.001). Gd-DTPA, unlike Gd-TO, washed completely out of acute infarcts within 2 hours of injection (P<0.001). The binding of Gd-TO to exposed DNA in acute infarcts was confirmed with fluorescence microscopy.

CONCLUSIONS

Gd-TO specifically binds to acutely necrotic cells and can be used to image the mechanism and chronicity of cell death in injured myocardium. Cell rupture in acute MI begins early but peaks many hours after the onset of injury. The ruptured cells are efficiently cleared by the immune system and are no longer present in the myocardium 72 hours after injury.

Imaging of apoptosis in the heart with nanoparticle technology

Apoptosis plays an important role in the loss of cardiomyocytes in both ischemic injury and heart failure. Pioneering work with single photon emission computed tomography imaging of (99)Tc-annexin showed that cell death in the heart could be imaged in vivo. Over the last 5 years a significant amount of experience with annexin-labeled magnetic nanoparticles, principally AnxCLIO-Cy5.5, has also been gained. Here, we review the experience with AnxCLIO-Cy5.5 in the heart and compare this experience to that of earlier studies with (99)Tc-annexin. The imaging of apoptosis with AnxCLIO-Cy5.5 provides valuable insights not only into molecular imaging in the heart but, more broadly, into the use of nanoparticle technology for molecular imaging in general.

Evaluating microvascular obstruction after acute myocardial infarction using cardiac magnetic resonance imaging and 201-thallium and 99m-technetium pyrophosphate scintigraphy

BACKGROUND

Few studies have compared the ability of cardiac magnetic resonance (CMR) with that of scintigraphy using 201-thallium (201-Tl) and 99m-technetium pyrophosphate (99m-Tc PYP) to evaluate microvascular obstructions (MOs). In the present study the relationship between the scintigraphic and CMR characteristics of MOs after acute myocardial infarction (MI) was examined.

METHODS AND RESULTS

The 14 patients (age 69±8 years, 11 males) underwent 201-Tl/99m-Tc PYP SPECT 7±3 days, initial CMR 16±12 days, and follow-up CMR 193±20 days after a reperfused first acute MI. Each image was analyzed using a 17-segment model. Segmental extent of delayed enhancement (DE), wall motion (WM) and degree of 201-Tl uptake were scored in 238 segments. Of 91 MI segments, MO was recognized in 22 (25%) segments on CMR. WM was significantly better in proportion to 201-Tl uptake (P=0.01) in MO segments. All 8 MO segments with WM improvement at follow-up had 99m-Tc PYP uptake, although only 3 (21%) of 14 MO segments that did not show WM improvement at follow-up had 99m-Tc PYP uptake (P=0.001).

CONCLUSIONS

99m-Tc PYP and 201-Tl scintigraphy have the potential to predict WM status and improvement of the MO region after reperfused acute MI.

Design of targeted cardiovascular molecular imaging probes

Molecular imaging relies on the development of sensitive and specific probes coupled with imaging hardware and software to provide information about the molecular status of a disease and its response to therapy, which are important aspects of disease management. As genomic and proteomic information from a variety of cardiovascular diseases becomes available, new cellular and molecular targets will provide an imaging readout of fundamental disease processes. A review of the development and application of several cardiovascular probes is presented here. Strategies for labeling cells with superparamagnetic iron oxide nanoparticles enable monitoring of the delivery of stem cell therapies. Small molecules and biologics (e.g., proteins and antibodies) with high affinity and specificity for cell surface receptors or cellular proteins as well as enzyme substrates or inhibitors may be labeled with single-photon-emitting or positron-emitting isotopes for nuclear molecular imaging applications. Labeling of bispecific antibodies with single-photon-emitting isotopes coupled with a pretargeting strategy may be used to enhance signal accumulation in small lesions. Emerging nanomaterials will provide platforms that have various sizes and structures and that may be used to develop multimeric, multimodal molecular imaging agents to probe one or more targets simultaneously. These platforms may be chemically manipulated to afford molecules with specific targeting and clearance properties. These examples of molecular imaging probes are characteristic of the multidisciplinary nature of the extraction of advanced biochemical information that will enhance diagnostic evaluation and drug development and predict clinical outcomes, fulfilling the promise of personalized medicine and improved patient care.

Advances in radionuclide molecular imaging in myocardial biology

Molecular imaging is a new and evolving field that employs a targeted approach to noninvasively assess biologic processes in vivo. By assessing key elements in specific cellular processes prior to irreversible end-organ damage, molecular tools will allow for earlier detection and intervention, improving management and outcomes associated with cardiovascular diseases. The goal of those working to expand this field is not just to provide diagnostic and prognostic information, but rather to guide an individual's pharmacological, cell-based, or genetic therapeutic regimen. This article will review molecular imaging tools in the context of our current understanding of biological processes of the myocardium, including angiogenesis, ventricular remodeling, inflammation, and apoptosis. The focus will be on radiotracer-based molecular imaging modalities with an emphasis on clinical application. Though this field is still in its infancy and may not be fully ready for widespread use, molecular imaging of myocardial biology has begun to show promise of clinical utility in acute and chronic ischemia, acute myocardial infarction, congestive heart failure, as well as in more global inflammatory and immune-mediated responses in the heart-like myocarditis and allogeneic cardiac transplant rejection. With continued research and development, molecular imaging promises to be an important tool for the optimization of cardiovascular care.

New molecular imaging targets to characterize myocardial biology

Molecular imaging represents a targeted approach to noninvasively assess biologic (both physiologic and pathologic) processes in vivo. Ideally the goal of molecular imaging is not just to provide diagnostic and prognostic information based on identification of the molecular events associated with a pathologic process but rather to guide individually tailored pharmacologic, cell-based, or genetic therapeutic regimens. This article reviews the recent advances in myocardial molecular imaging in the context of the cardiovascular processes of angiogenesis, apoptosis, inflammation, and ventricular remodeling. The focus is on radiotracer-based single photon emission computed tomography and positron emission tomography molecular imaging approaches.

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.

Molecular Imaging of Myocardial Injury: A Magnetofluorescent Approach

The role of molecular imaging in enhancing the understanding of myocardial injury and repair is rapidly expanding. Moreover, in recent years magnetic resonance and fluorescence-based approaches have been added to the molecular imaging armamentarium and have been used to image selected molecular and cellular targets in the myocardium. Apoptosis, necrosis, macrophage infiltration, myeloperoxidase activity, cathepsin activity, and type 1 collagen have all been imaged in vivo with a magnetofluorescent (MRI and/or fluorescence) approach. This review highlights the potential of these and other magnetofluorescent agents, with particular focus on their role in ischemic heart disease.

Targeted imaging of myocardial damage

Molecular imaging agents can be targeted to a specific receptor or protein on the cardiomyocyte surface, or to enzymes released into the interstitial space, such as cathepsins, matrix metalloproteinases and myeloperoxidase. Molecular imaging of the myocardium, however, requires the imaging agent to be small, sensitive (nanomolar levels or better), and able to gain access to the interstitial space. Several novel agents that fulfill these criteria have been used for targeted molecular imaging applications in the myocardium. Magnetic resonance, fluorescence, and single-photon emission CT have been used to image the molecular signals generated by these agents. The use of targeted imaging agents in the myocardium has the potential to provide valuable insights into the pathophysiology of myocardial injury and to facilitate the development of novel therapeutic strategies.

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.

Targeted ultrasound imaging using microbubbles

Targeted ultrasound imaging uses acoustically active contrast agents bearing a ligand on the surface that binds to a function-specific molecule. These ultrasound contrast agents are typically gas-filled microbubbles, nongaseous liposomes, or lipid-encapsulated perfluorocarbon emulsions. Binding of the contrast agent to the target results in persistent contrast enhancement during ultrasound imaging. This approach has been applied to the ultrasound imaging of pathophysiologic processes such as inflammation associated with ischemia reperfusion, heart transplant rejection, atherosclerotic plaque, thrombus, and apoptosis.

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.

Quantitative regional wall motion analysis with early contrast ventriculography for the assessment of myocardium at risk in acute myocardial infarction

BACKGROUND

Several techniques have been used to quantify the myocardium at risk, including measurement of regional ventricular function with contrast ventriculography and measurement of perfusion defect size with tomographic technetium-99m-sestamibi imaging. This study evaluates the correlation between these 2 techniques.

METHODS

Twenty-three patients with angiographically documented coronary occlusion and acute myocardial infarctions (10 anterior, 13 inferior) were studied. All patients had contrast left ventriculography at the time of their acute angiogram before any revascularization therapy. Regional wall motion parameters measured with the centerline method were the severity, circumferential extent, and global circumferential extent of hypokinesis and the mean standardized motion in predefined areas. Technetium-99m-sestamibi was injected before reperfusion therapy with measurement of the myocardium at risk using single photon emission computed tomography imaging.

RESULTS

The tomographic sestamibi-measured myocardium at risk was significantly greater for anterior infarctions compared with inferior infarctions (40% +/- 18% vs 14.0 +/- 8.5%, P =.0001). The only parameter of regional wall motion to show a significant difference by infarct location was global circumferential extent of hypokinesis (43% +/- 25% vs 22% +/- 15%, P =.02). The other parameters were not significantly different between anterior and inferior myocardial infarctions. For anterior infarctions, these parameters of regional wall motion correlated with myocardium at risk assessed with sestamibi: global circumferential extent of hypokinesis (r =.88, P <.01), circumferential extent of hypokinesis (r =.78, P <.01), mean standardized motion in predefined areas (r = -.74, P <.05), and severity of hypokinesis (r = -.70, P <.05). For inferior infarctions, there was no significant correlation between any of these parameters of regional wall motion and myocardium at risk assessed with sestamibi imaging.

CONCLUSION

The assessment of regional ventricular function with contrast ventriculography correlates with the area of myocardium at risk measured with tomographic technetium-99m-sestamibi for anterior, but not for inferior, myocardial infarctions. Therefore, these parameters of regional wall motion are a poor measure of the efficacy of reperfusion therapies.

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.

Imaging cell injury and death

Although there has been much emphasis on detecting myocardial viability over the past decade, there is a growing interest in finding a marker for myocyte injury and death. There has been limited clinical utility for infarct-avid imaging with (99m)Technetium ((99m)Tc) pyrophosphate and (111)Indium antimyosin, but recent experience with (99m)Tc-labeled annexin V and contrast-enhanced magnetic resonance imaging has stimulated cell death detection. In the effort to image myocyte damage, it is crucial to understand the pathologic finding and cell signals that can be used as critical in vivo markers for the transition from viable to dead tissue. It may not be possible to capture an image at the precise moment when a myocyte dies, but we need to know the different processes that can occur. Specifically, it is important to understand that oncosis and apoptosis are two distinctly different methods of cell death, and both ultimately result in myocyte necrosis. As we approach the more complex problems of myocyte injury during inflammation, cardiomyopathy, ischemia, reperfusion, and transplant rejection, we realize that more specific markers of real-time tissue injury are needed. This review focuses on the pathophysiology of myocyte injury necrosis and repair as a method to guide newer developments in myocardial imaging.

High sensitivity of radiolabelled antimyosin scintigraphy in assessing anthracycline related early myocyte damage preceding cardiac dysfunction

In antimyosin scintigraphy was evaluated at various cumulative anthracycline dose levels in order to early identify patients with severe cardiac injury and increased long-term risk of cardiac dysfunction. Twenty-four patients receiving standard doses of 60-75 mg.m(-2) doxorubicin or 90-112.5 mg.m(-2) epirubicin were followed at baseline, low (two cycles), middle (four cycles), and high (six cycles) cumulative dose using (111)In antimyosin 48 h heart-to-lung ratio (HLR), left ventricle ejection fraction (LVEF) and peak filling rate (PFR). At a low cumulative dose only HLR was significantly increased (P=0.0001); at middle dose HLR (P<0.0001) and LVEF (P=0.0054), but not PFR, were significantly changed, and at high dose HLR (P<0.0001), LVEF (P=0.0001) and PFR (P=0.033) all changed significantly. Concerning individual results, HLR became abnormal in 18 patients (75%) at low, 22 (92%) at middle, and 24 (100%) at high cumulative dose whereas LVEF and PFR remained within normal limits in all patients. It is concluded that myocyte damage appears to precede left ventricle systolic and diastolic dysfunction in anthracycline treatment. (111)In antimyosin scintigraphy is very sensitive in detecting myocardial damage after cumulative dose levels even as low as 120-150 mg.m(-2) doxorubicin or 180-225 mg.m(-2) epirubicin.

The clinical value of nuclear medicine in the assessment of irradiation-induced and anthracycline-associated cardiac damage

Two groups of patients, those treated for Hodgkin's disease and breast cancer, are particularly at risk of developing late myocardial damage, since radiotherapy (RT) techniques for both patient groups may include (large) parts of the heart, and adjuvant systemic therapy is frequently administered to these patients, in particular anthracycline-containing chemotherapy. Available literature on the monitoring and prediction of RT-induced and anthracycline-associated cardiac damage using nuclear medicine techniques is presented. Based on relevant studies, the risk of overall cardiac disease post-RT and overt congestive heart failure during anthracycline-containing chemotherapy is probably low. Conventional nuclear medicine imaging, i.e. myocardial perfusion scintigraphy, may be of complementary use to echocardiographical evaluation for routine follow-up after RT with modern techniques, in a subgroup of patients with known cardiovascular risk factors. Left ventricle ejection fraction (LVEF) measurements, as assessed by radionuclide angiography for the monitoring of anthracycline-associated cardiac injury, are not very sensitive and early detection will probably be enhanced by combining LVEF measurements with other cardiac function parameters. Also, it may be expected that nuclear medicine techniques using molecular radioligands will constitute an essential future step in the evaluation of subclinical cardiac injury afforded by the combined effect of RT and cardiotoxic chemotherapy.

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.

Marked ventricular repolarization abnormalities in highly trained athletes' electrocardiograms: clinical and prognostic implications

OBJECTIVE

We sought to study the functional, clinical and prognostic implications of marked repolarization abnormalities (MRA) sometimes seen in athletes' electrocardiograms (ECGs).

BACKGROUND

The clinical meaning of ECG MRA in athletes is unknown. No relationship has been drawn between either training intensity or any particular type of sport and MRA. Athletes are usually symptom free and do not show any decrease in their physical performance. It is as yet unclear whether MRA may have a negative effect on the performance of such athletes in competitive sports.

METHODS

We studied 26 athletes with MRA (negative T waves > or =2 mm in three or more ECG leads at rest). No athletes presented clinical symptoms of cardiac disease or decrease in their physical performance. Clinical and physical examinations, ECG at rest, exercise test and echocardiographic and antimyosin studies were performed in all athletes. Rest/exercise myocardial perfusion single-photon emission computed tomography studies were performed in 17 athletes. The follow-up ranged from 4 to 20 years (mean 6.7 years).

RESULTS

Four athletes were excluded due to hypertrophic cardiomyopathy. Echocardiographic studies showed right and left normal ventricular dimensions for highly conditioned athletes. In the exercise test, heart rate was 166 +/- 12.4 beats/min, and exercise tolerance was 15.2 +/- 2.7 metabolic equivalents of the task. All athletes had ECG at rest simulating myocardial ischemia or "pseudoischemia" with a tendency to normalize during exercise. Myocardial perfusion studies were normal in the studied athletes. Antimyosin studies showed mild and diffuse myocardial radiotracer uptake in 15 athletes (68%). No adverse clinical events were observed in the follow-up.

CONCLUSIONS

These results suggest that MRA have no clinical or pathological implications in athletes and should, therefore, not preclude physical training or participation in sporting events.

[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.

Cardiological applications of nuclear medicine

Cardiovascular mortality is falling in most industrialised nations. Primarily responsible for this encouraging trend are preventive measures such as risk-factor modification but improved medical and surgical management have helped too. Clinical decision making in the patient with coronary heart disease demands techniques that not only describe coronary anatomy but also provide functional indices for early detection and to monitor the severity and extent of disease. Nuclear medicine methods can characterise non-invasively myocardial function, perfusion, and metabolism. Novel radiopharmaceuticals, improvements in imaging equipment, and extensive validation have contributed to the growing clinical acceptance of these techniques and to their cost-effective integration in the workup of patients with cardiovascular disease.

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.

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.

Indium-111-antimyosin scintigraphy in the early detection of heart damage after anthracycline therapy in children

PURPOSE

To determine the value of indium-111-antimyosin ((111)In-AM) scintigraphy in the early detection of myocardial damage in children treated with doxorubicin.

PATIENTS AND METHODS

Twelve planar scintigrams were made of eight patients (seven children and one young adult; mean age, 12 years). Three scans were obtained before doxorubicin therapy in three patients, and nine scans were obtained during doxorubicin therapy in seven patients. The heart-to-lung ratio (HLR) was calculated. Left ventricular function was assessed by echocardiography before and during therapy by measuring the fractional shortening (FS).

RESULTS

The HLR of the three baseline scans was below 1.5, within the normal range for adults. Six of the seven patients whose scans were obtained during chemotherapy had abnormal HLR values (> 1.5). One patient had severe myocyte damage and showed an early increase in the HLR (2.3) after a cumulative doxorubicin dose of 150 mg/m(2). The FS measured by echocardiography was normal throughout therapy, and the final cumulative dose of doxorubicin was 450 mg/m(2). This patient developed fatal clinical heart failure 3 months after completion of chemotherapy. In one patient, who was pretreated with the cardioprotective agent dexrazoxane, the HLR remained within normal limits during therapy.

CONCLUSION

(111)In-AM scintigraphy seems to be suitable to detect early myocardial damage after a cumulative doxorubicin dose of 150 mg/m(2 )in children and may be useful for identifying children who are at increased risk of developing cardiac sequelae.

Quantitative autoradiography using a radioimager based on a multiwire proportional chamber

Determination of the biodistribution of radiopharmaceuticals is an important issue for the evaluation of their performance in diagnosis and therapy. In this study, we evaluated a digital radioimager (RI) based on a multiwire proportional chamber for quantitative autoradiography (AR). The RI allows direct detection of electronic emissions of gamma emitters. Its qualitative and quantitative performances were tested on 99mTc and (111)In labelled sections and compared with conventional film AR. Linearity of count rate versus activity was verified over a 104 range of activity. As compared with film AR, a substantial improvement of the detection limit was obtained even for acquisition periods up to 20 times less than film exposure times. We provided the basis for quantitative analysis with tissue equivalent paste standards: the 99mTc and (111)In RI counting efficiencies were respectively 1.19% and 2.35%. We illustrated the respective values of RI and film AR in two rat studies: 99mTc-DMSA in kidney and dual-isotope 99mTc-MIBI and (111)In-antimyosin in heart. Calculated activity concentrations on sections of rat organs confirmed good correlation to gamma counting (deviation less than 12%). We suggest RI as a convenient technique for fast localization of single or dual-isotope tracers and determination of activity distribution.

Antimyosin scintigraphy and immunohistologic analysis of endomyocardial biopsy in patients with clinically suspected myocarditis--evidence of myocardial cell damage and inflammation in the absence of histologic signs of myocarditis

OBJECTIVES

This study compares the results of antimyosin scintigraphy in patients with clinically suspected myocarditis with histologic and immunohistologic findings in the endomyocardial biopsy.

BACKGROUND

In patients with clinically suspected myocarditis, antimyosin scintigraphy often demonstrates myocardial cell damage but histologic evaluation of the endomyocardial biopsy often fails to show evidence of myocarditis. Recently developed immunohistologic techniques appear to be more sensitive for the detection of myocardial inflammation than histologic analysis alone. Studies comparing antimyosin scintigraphy and immunohistologic analysis of the endomyocardial biopsy in patients with clinically suspected myocarditis are not yet available.

METHODS

Sixty-five patients with clinically suspected myocarditis underwent antimyosin scintigraphy. Antimyosin antibody uptake was correlated with histologic and immunohistologic findings in the endomyocardial biopsy.

RESULTS

Antimyosin scintigraphy showed evidence of myocardial cell damage in 36 (55%) of the 65 patients and was negative in 29 (45%) patients. Histologic analysis of the endomyocardial biopsy revealed myocarditis in nine patients: six had a positive and three had a negative antimyosin scan, respectively. Thirty (83%) of 36 patients with evidence of myocardial cell damage on antimyosin scintigraphy were histologically negative for myocarditis. Immunohistologic analysis showed evidence of myocarditis in 31 (86%) of 36 patients with a positive antimyosin scan and also in 17 (59%) of 29 patients with a normal scan (p < 0.047).

CONCLUSIONS

Antimyosin scintigraphy often shows myocyte injury in patients with clinically suspected myocarditis. Histologic analysis of the endomyocardial biopsy alone is often negative, but additional immunohistologic analysis of the endomyocardial biopsy frequently provides evidence of myocardial inflammation in these patients. With immunohistologic analysis as the reference method, antimyosin scintigraphy has a high specificity but a lower sensitivity for the detection of myocarditis.

Ischemic and non-ischemic myocyte damage and antimyosin monoclonal imaging

Antimyosin monoclonal antibody is a specific marker of impaired sarcolemmal integrity resulting not only from ischemia but also from non-ischemic myocardial injury, such as infection, inflammatory, or immunologic reactions, and alcohol or drug intoxication. In addition, antimyosin accumulation has been demonstrated in some forms of cardiomyopathy with unknown as well as known etiologies. Antimyosin positivity appears to indicate precisely the extent of myocardial necrosis and to reflect cardiac dysfunction in an acute stage of active myocardial damage caused by ischemia and inflammation. However, the correlation is not necessarily good in the chronic stages of the disease or in idiopathic cardiomyopathic hearts; in other words, cardiac antimyosin uptake can be detected even in myocardial tissue with a normal histologic appearance independent of the presence of inflammatory responses, myocyte necrosis, or functional or morphologic deterioration. Thus, antimyosin is useful not only for detecting and quantifying acute myocardial necrosis but also for specifically identifying ongoing or latently progressing myocardial degeneration and sarcolemmal disruption, which will certainly lead to myocardial necrosis. These characteristics may contribute to the early detection of myocardial damage and lead to the investigation of pathophysiologic mechanisms. Further progress in immunologic and radiolabeling techniques is necessary for better specificity and less antigenicity against humans in antimyosin monoclonal antibody imaging.

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.

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.

In vivo imaging of chromogranin A-positive endocrine tumours by three-step monoclonal antibody targeting

The detection of chromogranins (Cg) by immunohistochemistry and serology represents a new in vitro diagnostic tool for endocrine tumours. We have recently reported on the feasibility of targeting chromogranin A (CgA) for in vivo detection of pituitary adenomas by immunoscintigraphy (ISG). The scintigraphic procedure, based on an anti-CgA monoclonal antibody and on the avidin-biotin three-step method (Cg-3S-ISG), was evaluated on a group of 29 consecutive patients with known or suspected endocrine tumours other than pituitary adenomas, i.e. medullary thyroid carcinoma, carcinoid, insulinoma and parathormone- or ACTH-producing tumours. Primary tumours (10) and recurrences (16) were visualised in 26 patients, whereas conventional imaging techniques (planar radiography, computerised tomography, magnetic resonance imaging and ultrasonography) failed to detect the tumour sites in ten of the same (Cg-3S-ISG-positive) patients. Therefore, these preliminary results indicate that Cg-3S-ISG, the first immunological method able to detect endocrine tumours in vivo, has a higher diagnostic accuracy than conventional imaging techniques (93.1% compared with 65.5%).

Myocardial indium-111 antimyosin uptake after uncomplicated coronary artery bypass surgery

The prevalence of myocardial damage after coronary artery bypass grafting is related to the criteria of its evaluation. Indium-111 monoclonal antimyosin antibody scintigraphy has been shown to be highly sensitive and specific for even small areas of myocardial necrosis or injury like those of myocarditis or transplant rejection. Our purpose was to evaluate, by using this method, myocardial damage after uncomplicated coronary artery bypass grafting. Uptake of this radio tracer was evaluated after coronary artery bypass grafting in 14 informed and consenting consecutive patients without previous myocardial infarction, with no post-surgical complications and a favorable postoperative course, following coronary artery bypass grafting for stable angina pectoris. Monoclonal antimyosin antibody indium-111 74 MBq (Myoscint Centocor) was injected on the third postoperative day; planar images in the anterior, left anterior oblique 45 degrees and 70 degrees projections were obtained 24 and 48 h later and analyzed for myocardial uptake. Indium-111 antimyosin uptake was present in 10 out of 14 patients (71.4%); it was diffuse in 6 and localized in 4. The ratio of the maximal counts in the myocardium to the counts in the adjacent lung background was measured and found elevated: 1.94 +/- 0.23, higher than the normal values reported in the literature. Indium-111 antimyosin uptake was clear in a group of patients after uncomplicated coronary artery bypass grafting. No correlation was observed between indium-111 antimyosin uptake or heart to lung ratio and creatine kinase, creatine kinase isoenzyme MB, glutamic oxalacetic transferase levels, duration of cardiopulmonary bypass or aortic cross-clamp time, while elevated serum beta myosin heavy chain fragments (IRMA Pasteur) were observed (1378 +/- 238 microU/l). This study suggests that some degree of myocardial damage, though silent, is common after coronary artery bypass grafting.

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.

Intercellular adhesion molecule-1 induction: a sensitive and quantitative marker for cardiac allograft rejection

OBJECTIVES

Rats with abdominal heterotopic heart transplants were studied to determine whether cardiac allograft rejection could be assessed by immunoscintigraphy targeting intercellular adhesion molecule-1 (ICAM-1), which was induced on allografted organ cells in association with rejection.

BACKGROUND

It is important to detect early rejection before development of myocyte necrosis. Although a variety of methods for the detection of cardiac rejection have been investigated, histologic inspection of biopsied samples is still used routinely for clinical diagnosis of rejection.

METHODS

DA rat (RT-1a) hearts were transplanted into PVG rats (RT-1c). Immunohistologic examination of the allografts demonstrated that ICAM-1 induction on vascular endothelial cells was observed as early as 4 days after transplantation in this combination. Thirty-nine allografted rats and seven isografted rats were studied. One day after injection of 100 microCi of 111Inlabeled anti-ICAM-1 monoclonal antibody (1A29), planar images were obtained.

RESULTS

Rejecting allografts showed increased radiotracer uptake and could be identified on the images as early as 5 days after transplantation. In contrast, nonrejecting cardiac allografts and isografts did not show specific uptake. Mildly rejecting allografts, with mononuclear cell infiltration but without significant myocyte necrosis, could be scintigraphically identified, and the level of radiotracer uptake reflected the histologic severity of rejection. Accumulation of 111In-labeled monoclonal antibody of isotype-matched irrelevant specificity was not detected in the rejecting allografts.

CONCLUSIONS

These data indicate that ICAM-1 induction can be assessed quantitatively by radioimmunoscintigraphy. Radioimmunoscitigraphy is a sensitive method for early detection and assessment of cardiac allograft rejection.