Measurement of infarct size and percentage myocardium infarcted in a dog preparation with single photon-emission computed tomography, thallium-201, and indium 111-monoclonal antimyosin Fab

Critical Appraisal of the Current Role of Myocardial Perfusion Imaging in the Management of Acute Chest Pain

This paper describes the evolution of nuclear cardiology techniques in the setting of acute coronary syndromes. Since the 1970s, the contribution of nuclear cardiology has been fundamental in delineating the physiopathology and diagnosis of acute myocardial infarction, when electrocardiogram (ECG) did not provide the diagnosis and when cardiac enzyme assessments were at a very early stage. In this clinical situation, at that time the role of pyrophosphate scintigraphy and antimyosin antibodies was important in ensuring diagnostic precision. However, these methods showed limitations and were abandoned in the late 80s and early 90s when therapeutic applications such as thrombolytic therapy, and primary-and rescue-percutaneous coronary intervention (PCI) were introduced. Beginning in the mid-80s, the introduction and widespread use of perfusion tracers such as 99mTc labelled compounds and technological advances such as SPECT, allowed to assess the efficacy of thrombolysis and early revascularization, as well as to assess in depth myocardial salvage. Currently, perfusion SPECT, especially using fast imaging techniques and dedicated cardiac SPECT with solid-state detectors, allows a quick confirmation or exclusion of acute coronary syndromes, particularly in low-to-intermediate likelihood of coronary artery disease (CAD), especially when there are absolute or relative contraindications to the use of coronary computed tomographic angiography (CCTA).

99mTc/123I Dual-Radionuclide Correction for Self-Scatter, Down-Scatter, and Tailing Effect for a CZT SPECT with Varying Tracer Distributions

SPECT systems distinguish radionuclides by using multiple energy windows. For CZT detectors, the energy spectrum has a low energy tail leading to additional crosstalk between the radionuclides. Previous work developed models to correct the scatter and crosstalk for CZT-based dedicated cardiac systems with similar 99mTc/123I tracer distributions. These models estimate the primary and scatter components by solving a set of equations employing the MLEM approach. A penalty term is applied to ensure convergence. The present work estimates the penalty term for any 99mTc/123I activity level. An iterative approach incorporating Monte Carlo into the iterative image reconstruction loops was developed to estimate the penalty terms. We used SIMIND and XCAT phantoms in this study. Distribution of tracers in the myocardial tissue and blood pool were varied to simulate a dynamic acquisition. Evaluations of the estimated and the real penalty terms were performed using simulations and large animal data. The myocardium to blood pool ratio was calculated using ROIs in the myocardial tissue and the blood pool for quantitative analysis. All corrected images yielded a good agreement with the gold standard images. In conclusion, we developed a CZT crosstalk correction method for quantitative imaging of 99mTc/123I activity levels by dynamically estimating the penalty terms.

Rational chemical design of the next generation of molecular imaging probes based on physics and biology: mixing modalities, colors and signals

In recent years, numerous in vivo molecular imaging probes have been developed. As a consequence, much has been published on the design and synthesis of molecular imaging probes focusing on each modality, each type of material, or each target disease. More recently, second generation molecular imaging probes with unique, multi-functional, or multiplexed characteristics have been designed. This critical review focuses on (i) molecular imaging using combinations of modalities and signals that employ the full range of the electromagnetic spectra, (ii) optimized chemical design of molecular imaging probes for in vivo kinetics based on biology and physiology across a range of physical sizes, (iii) practical examples of second generation molecular imaging probes designed to extract complementary data from targets using multiple modalities, color, and comprehensive signals (277 references).

Multiplexed imaging in cancer diagnosis: applications and future advances

The development of imaging technologies that have sufficient specificity and sensitivity to enable early, accurate detection of cancer and response to therapy has long been a goal in oncology. Various radiological techniques have been used for diagnosis and surveillance of disease recurrence and imaging has revolutionised oncology. However, despite the widespread use of technologies, the ability of currently available imaging methods to facilitate early detection, precise characterisation, and accurate localisation of malignant disease could be improved. The simultaneous use of two or more techniques, contrast reagents, signalling methods, or the coupling of agent and tissue properties to achieve so-called multiplexed imaging is a promising approach. In this review, we provide a broad overview of current and emerging multiplexed, imaging technologies.

Myocarditis in patients with clinical presentation of myocardial infarction and normal coronary angiograms

OBJECTIVES

The aim of this study was to assess the diagnosis of myocarditis in patients presenting with acute myocardial infarction (MI) and normal coronary angiograms.

BACKGROUND

Most often in these patients, the etiologic diagnosis remains unclear once they are found to have normal coronary arteries. The diagnosis of myocarditis mimicking MI is clinically relevant, because numerous arguments suggest a relation between myocarditis and dilated cardiomyopathy. Myocardial indium-111 (111In)-antimyosin antibody (AMA)/rest thallium-201 (201Tl) imaging allows noninvasive detection of myocarditis.

METHODS

Forty-five patients admitted to three intensive care units for suspicion of acute MI, with normal coronary angiograms, were investigated. Indium-111-AMA planar images and then a dual-isotope rest AMA/201Tl tomographic study were performed. Six-month echocardiographic follow-up was obtained in 80% of the patients with initial left ventricular (LV) wall motion abnormalities.

RESULTS

In eight patients, AMA and 201Tl scintigraphy were negative. In two patients, a matched 201Tl defect and focal AMA uptake suggested acute MI (due to prolonged vasospasm or spontaneously reperfused coronary occlusion). In 17 patients, diffuse AMA uptake over the whole LV suggested diffuse myocarditis. In 18 patients, focal AMA uptake with a normal 201Tl scan suggested diffuse but heterogeneous, or focal myocarditis. Complete functional recovery was observed in 81% of the patients with a pattern of myocarditis.

CONCLUSIONS

Among 45 patients presenting with acute MI and normal coronary angiograms, 38% had diffuse myocarditis and 40% had a scintigraphic pattern of heterogeneous or focal myocarditis. Short-term follow-up showed complete LV functional recovery in 81% of these patients.

Clinical characteristics of unexplained sudden cardiac death in Korea

In Western countries, sudden cardiac death (SCD) is closely related to coronary artery disease, but in Korea the clinical characteristics of SCD are not well determined. Over a 4-year period (June 1995 to May 1999), 186 cases of SCD, ranging in age from 16 to 75 years, were admitted to the Chonnam National University Hospital. In 82 (44.1%) of these, neither symptoms nor evidence of structural heart disease was found and so their clinical characteristics were investigated. There were 66 (80.5%) men and 16 (19.5%) women (male/female ratio = 4.1:1). The mean age was 50 +/- 14 years: 19 (23.2%) were in their 40s, 21 (25.6%) in their 50s, and 17 (20.7%) in their 60s. The time of circulatory collapse witnessed in 68 cases of SCD showed 2 peaks: between midnight and 03.00h (n=16, 23.5%) and between 09.00h and midday (n=15, 22.1%). Unexplained SCD occurred at home in 48 (64.9%) cases and on the street in 12 (16.2%); it occurred during normal daily routine activity in 23 (39.6%) and during sleep in 15 (25.9%). Thirty-three patients (40.2%) experienced various prodromal symptoms, including chest discomfort (n=13, 15.9%) and dyspnea (n=8, 9.8%). The electrocardiogram taken on arrival recorded asystole in 65 (79.3%) and ventricular fibrillation in 17 (20.7%). Idiopathic ventricular fibrillation was diagnosed in 14 (10 men, 4 women; 45 +/- 11 years) of 21 patients who recovered spontaneous circulation. Five (6.1%) patients were discharged alive, and an implantable cardioverter-defibrillator was implanted in 2. Unexplained SCD is common in Korea and develops predominantly in middle-aged males around midnight or in the late morning usually with no prodromal symptoms (59.8%). Idiopathic ventricular fibrillation is thought to be one of the important causes.

Simultaneous technetium-99m/thallium-201 SPECT imaging with model-based compensation for cross-contaminating effects

Simultaneous acquisition of dual-isotope SPECT data offers a number of advantages over separately acquired data; however, simultaneous acquisition can result in cross-contamination between isotopes. In this work we propose and evaluate two frameworks for iterative model-based compensation of cross-contamination in dual-isotope SPECT. The methods were applied to cardiac imaging with technetium-99m-sestamibi and thallium-201, and they were compared with a subtraction-based compensation method using a cross-talk estimate obtained from an auxiliary energy window. Monte Carlo simulations were performed to carefully study aspects of bias and noise for the methods, and a torso phantom with cardiac insert was used to evaluate the performance of the methods for experimentally acquired data. The cross-talk compensation methods substantially improved lesion contrast and significantly reduced quantitative errors for simultaneously acquired data. Thallium image normalized mean square error (NMSE) was reduced from 0.522 without cross-talk compensation to as low as 0.052 with model-based cross-talk compensation. This is compared with a NMSE of 0.091 for the subtraction-based compensation method. The application of a preliminary model for cross-talk arising from lead fluorescence x-rays and collimator scatter gave promising results, and the future development of a more accurate model for collimator interactions would probably benefit simultaneous Tc/Tl imaging. Model-based compensation methods provide feasible cross-talk compensation in clinically acceptable times, and they may ultimately make simultaneous dual-isotope protocols an effective alternative for many imaging procedures.

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.

Indium-111 antimyosin monoclonal antibody Fab imaging in patients with cardiomyopathy

Six patients with cardiomyopathy were imaged following intravenous injection of an indium-111 labeled monoclonal antibody directed against the heavy chain of cardiac myosin. Two patients had hypertrophic non-obstructive cardiomyopathy (HNCM), two patients had dilated cardiomyopathy (DCM), and two patients had specific heart muscle disease. One of 2 patients with HNCM and one of 2 patients with DCM had a positive antimyosin scan. The 2 patients with specific heart muscle disease manifested persistent blood pool activity of the antibody, thereby precluding interpretation of the images. The present report demonstrates that antimyosin antibody imaging may provide evidence of myocardial injury, or necrosis in some patients with cardiomyopathy.

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.

Intraventricular conduction abnormalities in patients with clinically suspected myocarditis are associated with myocardial necrosis

Twenty-nine patients with suspected myocarditis, either with or without intraventricular conduction abnormalities, were investigated for degree of myocardial necrosis by antimyosin scintigraphy. Among those 29 patients, 16 had intraventricular conduction abnormalities. Antimyosin scans were analyzed for heart/lung ratios and semiquantitative visual uptake scores (0 to 4+ scale). Of the 16 patients with conduction abnormalities, 15 (94%) demonstrated visual antimyosin uptake versus 7 (54%) of 13 cases without conduction abnormalities (p < 0.03). In addition, the heart/lung ratios and uptake scores were significantly higher in the group with conduction abnormalities than in the group without (1.64 +/- 0.31 vs 1.39 +/- 0.20, p < 0.03; and 2.3 +/- 0.7 vs 1.4 +/- 0.7, p < 0.005; respectively). In conclusion, intraventricular conduction abnormalities in patients with suspected myocarditis were more strongly associated with active and more severe myocardial necrosis as judged by antimyosin imaging than patients with normal electrocardiograms.

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.

Assessment of acute myocardial infarction by nuclear imaging techniques

In recent years, nuclear cardiology techniques have been successfully applied in patients with acute myocardial infarction. These scintigraphic measurements have provided important diagnostic, therapeutic, and prognostic information based on the extent of myocardial damage and the functional reserve of the left ventricle. In particular, in the thrombolytic era, myocardial perfusion imaging and radionuclide angiography have been shown to be valuable methods for studying the effects of reperfusion on the extent of myocardial damage. Nuclear magnetic resonance imaging, preferably with contrast enhancement, is one of the newly developed nuclear imaging techniques that have probably the greatest potential in accurately delineating myocardial infarct size and in evaluating left ventricular function. Radionuclide procedures, on the other hand, employ more biologically oriented tracers and are therefore capable of monitoring biochemical changes in the course of acute myocardial infarction.

Monoclonal Fab antimyosin in cardiac imaging

Antimyosin is an Fab fragment of a murine monoclonal antibody directed against human heavy chain myosin. It is specific for myocyte necrosis. When linked via diethylenetriaminepentaacetic acid to indium-111, the agent has good imaging properties. With planar imaging, it has demonstrated high sensitivity and specificity for detecting and localizing acute myocardial infarction (MI). In addition, studies of dual isotope (indium-111 antimyosin/thallium-201) SPECT imaging at rest in the early in-hospital post-MI period appear to be predictive of further ischemic events. Antimyosin imaging also shows promise as a noninvasive tool to aid in the diagnosis and assessment of prognosis in cardiac transplant rejection and myocarditis. There is no evidence to date for allergic reactions to the murine protein.

Clinical role of indium-111 antimyosin imaging

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

Effect of infarct size measured from antimyosin single-photon emission computed tomographic scans on left ventricular remodeling

To evaluate the effect of infarct size on left ventricular volumes and geometric remodeling, 26 patients with a first acute Q wave myocardial infarction (anterior in 14, inferior in 12) had the infarct sized from single-photon emission computed tomographic (SPECT) imaging of indium-111 antimyosin. All patients underwent gated blood pool scintigraphy before hospital discharge for determination of ejection fraction and end-diastolic and end-systolic volume indexes. Infarct size was quantitated from indium-111 antimyosin uptake in coronal slices with use of a threshold technique for edge detection. Nineteen of 26 patients had additional simultaneous acquisitions of indium-111 and thallium-201 uptake and the infarct was expressed as a percent of the total left ventricle. Infarct size was larger (59 +/- 16 vs. 33 +/- 16 g), predischarge ejection fraction lower (35 +/- 5% vs. 60 +/- 9%) and end-systolic volume index higher (57 +/- 13 vs. 36 +/- 10 ml/m2) in the group with anterior infarction. Despite these differences, predischarge end-diastolic volume index was not significantly different between the group with anterior (88 +/- 17 ml/m2) versus inferior (89 +/- 14 ml/m2) infarction. There was a significant inverse correlation between percent infarct size and ejection fraction for patients with dual isotope imaging (r = -0.90) and a significant direct correlation between infarct size and end-systolic volume index (r = 0.79, p less than 0.01). Fourteen patients without subsequent myocardial infarction or coronary artery bypass grafting had a repeat gated blood pool study late (26 +/- 15 months) after infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of thallium-201 SPECT and planar imaging methods for quantification of experimental myocardial infarct size

To compare single photon emission computed tomography (SPECT) and planar thallium-201 (TI-201) myocardial perfusion imaging methods for quantification of left ventricular infarct size, 12 dogs with 6 to 8 hours of closed-chest coronary occlusion and 5 normal dogs were studied. After intravenous administration of TI-201, SPECT and three-view planar images were obtained. After the animals were put to death, hearts were sliced and stained with triphenyltetrazolium chloride (TTC) for planimetric determination of left ventricular infarct size. Infarct size on each SPECT slice and planar image was defined as the percentage of circumferential count profiles falling below the limits derived from normal dogs. Infarct size as a percentage of left ventricular mass was determined from SPECT and planar images before and after correcting for differences in myocardial slice mass from apex to base. The correlation coefficients, the concordance correlation coefficients (reflecting closeness to the line of identity), and the mean absolute deviations of the four methods versus TTC staining were 0.83, 0.77, and 5.1% (SPECT, no correction); 0.85, 0.84, and 3.7% (SPECT with correction); 0.81, 0.42, and 12.9% (planar, no correction); and 0.75, 0.49, and 10.4% (planar with correction). The regression lines did not differ from the line of identity for SPECT, whereas they differed significantly for planar imaging. Thus both SPECT and planar imaging are well suited for quantification of left ventricular infarct size. SPECT, however, appears to be superior to planar imaging, since its regression line more closely approximates the line of identity.

Clinical application of indium-111 antimyosin antibody and thallium-201 dual nuclide single photon emission computed tomography in acute myocardial infarction

The significance of indium-111 antimyosin antibody and thallium-201 dual nuclide single photon emission computed tomography (SPECT) was evaluated in 7 patients with acute myocardial infarction (AMI) who underwent emergency coronary angiography with successful revascularization by intracoronary thrombolysis. Indium-111 antimyosin antibody and thallium-201 dual nuclide SPECT was performed 11 to 36 days after the onset of AMI. Antimyosin SPECT images delineated areas of myocardial necrosis in all 7 patients (100%), but planar images detected necrotic areas in only 4 of 7 patients (57%). Peak CPK-MBs of the 3 patients in which no necrotic area was detected by indium-111 planar image showed a tendency to be smaller. Indium-111 antimyosin antibody/thallium-201 overlap was observed in all patients. The area of overlap was at the center of necrosis in 4 patients (2 anterior infarction, 1 inferior infarction, 1 inferolateral infarction) and at the peripheral portion in 3 patients (all 3 had inferior infarction). Indium-111 antimyosin antibody and thallium-201 dual nuclide SPECT is useful in identifying the localization of myocardial infarction and the overlap of these tracers might reflect the presence of salvaged myocardium adjacent to the necrotic myocardium.

Comparison of indium-111 antimyosin antibody and technetium-99m pyrophosphate localization in reperfused and nonreperfused myocardial infarction

Recent imaging studies suggest that technetium-99m (Tc-99m) pyrophosphate yields a considerably larger estimate of myocardial infarct size than does indium-111 (In-111) monoclonal antimyosin antibody. To determine whether Tc-99m pyrophosphate may be taken up by reversibly injured myocytes, particularly in the setting of coronary reperfusion, the tissue localization of Tc-99m pyrophosphate and antimyosin antibody was compared in 11 dogs 24 to 68 h after anterior descending coronary artery occlusion (4 dogs with permanent occlusion, 7 with reperfusion). Technetium-99m pyrophosphate and In-111 antimyosin antibody content was determined in serial 2 to 3 mm wide endocardial and epicardial samples taken through the infarct zone in multiple short-axis left ventricular slices. The number of samples with increased In-111 antimyosin antibody (defined as greater than or equal to mean + 2 SD of normal) was not significantly different from that with increased Tc-99m pyrophosphate. This was true in both reperfused and nonreperfused infarcts. However, the intensity of uptake of Tc-99m pyrophosphate exceeded that of In-111 antimyosin antibody, particularly in the border zones of reperfused infarcts, and the area with moderate to marked increase in tracer uptake (greater than or equal to 2 times normal) was significantly larger with Tc-99m pyrophosphate than In-111 antimyosin antibody (p less than 0.001). A specific zone of abnormal Tc-99m pyrophosphate with normal In-111 antimyosin antibody content could not be identified. Histologic evidence of myocardial necrosis was found in virtually every sample with increased In-111 antimyosin antibody, Tc-99m pyrophosphate, or both.(ABSTRACT TRUNCATED AT 250 WORDS)

Radioimmunodetection of uterine leiomyosarcoma with 111In-labeled monoclonal antimyosin antibody Fab fragments

Radioimmunodetection of uterine leiomyosarcoma in a 64-year-old woman with a palpable local recurrence is described. Pathological abdominal, pelvic, and thoracic accumulation of monoclonal 111In-labeled antimyosin was observed. Afterward, these lesions were examined by whole-body X-ray computed tomography. With a double-tracer technique (pulmonary and hepatic/splenic subtractions) the lesions were delineated better and SPECT (radioisotope tomography) was used for more accurate localization of the abdominal and pelvic lesions. These findings indicate that antimyosin scintigraphy might be useful in staging and follow-up of uterine leiomyosarcoma.

Localization of In-111 antimyosin Fab and 99mTc-pyrophosphate in reperfusion myocardial infarction model

The myocardial uptake of In-111 antimyosin Fab and Tc-99m pyrophosphate was studied in dogs undergoing coronary artery occlusion for 90 minutes followed by reperfusion. The regional myocardial blood flow was determined by injecting Sc-46 labeled microsphere and was related to the relative concentrations of In-111 antimyosin and Tc-99m pyrophosphate. There was an inverse linear correlation between In-111 antimyosin Fab localization and the regional blood flow in both the subendocardial (r = 0.81) and subepicardial myocardium (r = -0.80). The greatest uptake of antimyosin was observed in areas of severe blood flow reduction (0-10% of normal). On the other hand, there was no correlation between the Tc-99m pyrophosphate uptake and the degree of blood flow reduction. Maximal subendocardial localization of Tc-99m degree of blood flow reduction. Maximal subendocardial localization of Tc-99m pyrophosphate was observed in areas where the blood flow was reduced to 31-50% of the normal. In the case of the subepicardium, the greatest uptake was localized to areas of 0 to 10% of the normal flow. In addition, there was significant myocardial uptake in regions where the blood flow was minimally reduced (greater than 81%). This study suggests that In-111 antimyosin Fab is a specific and quantitative tool in the evaluation of myocardial necrosis.

In vitro validation of a simple tomographic technique for estimation of percentage myocardium at risk using methoxyisobutyl isonitrile technetium 99m (sestamibi)

With the advent of technetium 99m-labeled myocardial blood flow agents, there is a need for a simple technique for quantitation of infarcted or jeopardized myocardium (IM). This study provides an in vitro validation of a simple technique based upon the analysis of three short-axis slices through the heart following emission computed tomography. All acquisitions were performed using a static cardiac phantom containing pertechnetate Tc 99m. Activity in the phantom was adjusted so that the count density and myocardial-to-background ratio were comparable to those observed in patients. Plastic insets (range of sizes = 4%-72% of myocardium) were used to simulate transmural infarctions. Eighteen studies were acquired, each over 180 degrees into a 64 x 64 matrix. Data were reconstructed using a Ramp Hanning filter with cut off at 0.7 times the Nyquist frequency. Short-axis slices of the myocardium were then generated, and representative apical (A), mid-ventricular (MV), and basal (B) slices were selected. For each slice, a circumferential profile was generated, and the average radius (R) was measured. The fraction (F) of the profile falling below a threshold value was considered to represent IM. Total IM was given by % IM = 100 x (RB FB + RMV FMV + 0.67 RA FA)/(RB + RMV + 0.67 RA), where the subscripts to R and F refer to the relevant short-axis slices. For a threshold set at 60% of peak, measured IM agreed closely with true IM (R2 = 0.98, measured IM = 1.01 x true IM - 1.35). Measurement of % IM was not distorted by variations in slice radius or in slice selection.(ABSTRACT TRUNCATED AT 250 WORDS)

Infarct sizing by scintigraphic techniques and nuclear magnetic resonance imaging

Assessment of myocardial infarct size is the cornerstone in the evaluation of interventions designed to salvage myocardium, such as thrombolytic therapy and urgent coronary angioplasty. Enzymatic methods have probably the highest accuracy but can only be used in the very early phase of infarction. The electrocardiogram allows a reasonable estimate of infarct size, but its confidence limits are wide, and in inferior wall infarction the estimates are unreliable. In recent years, radionuclide techniques have been successfully used to identify, localize and determine infarct size in the course of acute myocardial infarction. These scintigraphic measurements have provided important diagnostic, therapeutic and prognostic information based on the extent of myocardial damage. Nuclear magnetic resonance imaging, particularly with contrast enhancement, is one of the methods that have the greatest potential in accurately delineating myocardial infarct size. Nuclear medicine procedures, on the other hand, employ more biologically oriented tracers and offer promise in view of their ability to monitor biochemical alterations as an effect of therapy in the course of myocardial infarction.

The role of antimyosin antibodies in acute myocardial infarction

Antimyosin is an Fab fragment of a monoclonal antibody that binds with human myosin exposed in myocytes irreversibly damaged by an ischemic event. Labeled with 111In, the antibody is taken up into acutely necrotic tissue and can be imaged by planar or single photon emission computed tomography (SPECT) techniques. A large, multicenter clinical trial has demonstrated a high degree of both sensitivity for detecting infarction and specificity for excluding a recent ischemic event in patients admitted with chest pain syndrome. No allergic reactions to antibody injection have occurred, nor have there been documented significant increases in human antimouse antibody titers postinjection. Due to relatively slow blood clearance, the optimal imaging time is 24 to 48 hours post-injection. Between 13% and 21% of 24-hour scans are nondiagnostic due to persistent blood pool activity. In two thirds of these patients, 48-hour scans confirm negative tracer uptake. Moderate to intense cardiac uptake occurs in greater than 80% of scans. Faint tracer uptake, which occurs in a small minority of patients, is associated with inferoposterior infarct location and an occluded infarct vessel. Potential clinical uses include both diagnostic and prognostic areas. A negative scan in a patient with chest pain syndrome and no ECG changes rules out a recent significant ischemic event. The extent of antimyosin uptake (infarct size), measured semiquantitatively from planar scans or quantitatively from SPECT reconstructions, has been shown to correlate with future cardiac events. Relative patterns of distribution of indium-antimyosin and 201TI on simultaneous dual isotope SPECT reconstructions may identify patients with residual myocardium at further ischemic risk.

Measurement of acute Q-wave myocardial infarct size with single photon emission computed tomography imaging of indium-111 antimyosin

Myocardial infarct size was measured by single photon emission computed tomography (SPECT) following injection of indium-111 antimyosin in 27 patients (18 male and 9 female; mean age 57.4 +/- 10.5 years, range 37 to 75) who had acute transmural myocardial infarction (MI). These 27 patients represent 27 of 35 (77%) consecutive patients with acute Q-wave infarctions who were injected with indium-111 antimyosin. In the remaining 8 patients either tracer uptake was too faint or the scans were technically inadequate to permit infarct sizing from SPECT reconstructions. In the 27 patients studied, infarct location by electrocardiogram was anterior in 15 and inferoposterior in 12. Nine patients had a history of prior infarction. Each patient received 2 mCi of indium-111 antimyosin followed by SPECT imaging 48 hours later. Infarct mass was determined from coronal slices using a threshold value obtained from a human torso/cardiac phantom. Infarct size ranged from 11 to 87 g mean 48.5 +/- 24). Anterior infarcts were significantly (p less than 0.01) larger (60 +/- 20 g) than inferoposterior infarcts (34 +/- 21 g). For patients without prior MI, there were significant inverse correlations between infarct size and ejection fraction (r = 0.71, p less than 0.01) and wall motion score (r = 0.58, p less than 0.01) obtained from predischarge gated blood pool scans. Peak creatine kinase-MB correlated significantly with infarct size for patients without either reperfusion or right ventricular infarction (r = 0.66). Seven patients without prior infarcts had additional simultaneous indium-111/thallium-201 SPECT studies using dual energy windows.(ABSTRACT TRUNCATED AT 250 WORDS)

Uptake and release of two new Tc-99m labeled myocardial blood flow imaging agents in cultured cardiac cells

Two new neutral lipophilic 99mTc labeled molecules, chloro (methylboron (1-)-tris[1,2-cyclohexane-dionedioxime (1-)]-N,N',N'',N''',N'''',N''''') (SQ 30217) and Bis [1,2-cyclohexanedione dioximato (1-)-0]-[1,2-cyclohexane-dione dioximato (2-)-0] borato (2-N,N',N'',N''',N'''',N''''')-chloro Tc (SQ 32014), were studied in cultures of beating myocardial cells of newborn rats. The uptake and release kinetics, the effects of various pH levels of the medium, and the effects of three metabolic inhibitors, i.e., ouabain, cyanide and iodoacetate were assessed. Results show that T1/2 of uptake were less than 2 min with both tracers, and T1/2 of release were 12 and 13 min with SQ 32014 and SQ 30217, respectively. The intra/extracellular tracer concentrations was about 15 times higher with SQ 30217 than with SQ 32014. Intracellular concentration was decreased for both tracers at high pH levels, and was only moderately modified otherwise, including in the presence of the metabolic inhibitors. It is concluded that both tracers present very interesting properties for myocardial blood flow imaging, although a higher contrast should be expected with SQ 30217 than with SQ 32014.

Quantification of area and percentage of infarcted myocardium by single photon emission computed tomography with thallium-201: a comparison with serial serum CK-MB measurements

In order to quantify the size of the infarcted myocardium, two kinds of data processing techniques were applied to single photon emission computed tomography (SPECT) with thallium-201 and its clinical reliability was evaluated by comparing it with the infarct sizing procedure with the serial serum creatine kinase-MB measurements in 14 patients with acute myocardial infarction. After maximum-count circumferential profile analysis, short axis images were reformatted into an unfolded surface map and a bull's eye view map. The SPECT-determined infarct size was defined as the area or the percentage of hypoperfused myocardium of which the profile count was less than the mean minus 2SD derived from 8 normal subjects. The infarct area was calculated from the number of pixels with an abnormal count and expressed in an unfolded surface map. The percentage was calculated from the number of abnormal profile points and displayed in a bull's eye view map. A high linear correlation was observed between the enzymatically determined infarct size and the infarct area or the percentage (r = .947, r = .872, respectively), despite underestimations in 2 patients with accompanying right ventricular infarction and overestimations in 2 patients with prior anterior infarction. Moreover, a close negative correlation was found between the left ventricular ejection fraction and the infarct area or the percentage (r = .836, r = .821, respectively). Thus, the semiautomatic techniques for processing thallium-201 SPECT images might contribute to the quantitative estimation and display of infarcted myocardium and have high clinical reliability.

Antimyosin imaging in acute transmural myocardial infarctions: results of a multicenter clinical trial

Murine monoclonal antimyosin antibody has been shown experimentally to bind selectively to irreversibly damaged myocytes. To evaluate the safety and efficacy of monoclonal antimyosin for identifying acute transmural infarction, 50 patients with acute Q wave myocardial infarction were entered into a phase I/II multicenter trial involving three clinical sites. Indium-111 antimyosin was prepared from an instant kit formulation containing 0.5 mg of diethylene triamine pentaacetic acid (DTPA)-coupled Fab fragment (R11D10) and 1.2 to 2.4 mCi of indium-111. Average labeling efficiency was 92%. Antimyosin was injected 27 +/- 16 h after the onset of chest pain. Planar or tomographic imaging was performed 27 +/- 9 h after injection in all patients, and repeat imaging was done 24 h later in 39 patients. Of the 50 patients entered, 46 showed myocardial uptake of antimyosin (sensitivity 92%). Thirty-one of 39 planar scans performed at 24 h were diagnostic; 8 showed persistent blood pool activity that cleared by 48 h. Focal myocardial uptake of antimyosin corresponded to electrocardiographic infarct localization. No patient had an adverse reaction to antimyosin. In addition, 125 serum samples, including 21 collected greater than 42 days after injection, were tested for human antimouse antibodies, and all samples were assessed as having undetectable titers. Intensity of antimyosin uptake was correlated with infarct location and the presence or absence of collateral vessels. There was a significant correlation between faint uptake and inferoposterior infarct location. In 21 patients who had coronary angiography close to the time of antimyosin injection, there was a significant correlation between faint tracer uptake and closed infarct-related vessel with absent collateral flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Open-heart surgery in octogenarians

One hundred consecutive patients 80 years of age or older consented to and subsequently underwent open-heart operations at our institution between July 1976 and May 1987. Fifty of the patients had aortic valvular disease (28 with coexisting coronary artery disease), and 41 had isolated coronary artery disease. Eight patients had mitral valvular disease, and one had a dissecting aortic aneurysm. Ninety had Class IV disease that was functional, ischemic, or both. The most compelling indications for operation in 85 patients were unstable or postinfarction angina, syncope, acute pulmonary edema, or cardiogenic shock. Twenty-nine patients died soon after operation (within 90 days). New York Heart Association Class IV disease, previous myocardial infarction, cachexia, and emergency operation were preoperative variables associated with early death. Forty-three patients had no complications except for atrial arrhythmias and were discharged from the hospital a mean (+/- SD) of 11.5 +/- 3.7 days after operation. Low cardiac output, acute myocardial infarction, reoperation for bleeding, renal insufficiency, pneumonia, and prolonged endotracheal intubation were the most common serious postoperative complications. Twenty-eight patients who survived postoperative complications were discharged 24.9 +/- 19.6 days after operation. Seventeen patients died 2 to 104 months after discharge from the hospital. Actuarial calculation predicts the survival of 59 percent of patients at three years and 54 percent at five years. Of the 54 patients still alive at this writing, 53 have disease within New York Heart Association and Canadian Cardiovascular Society Classes I or II. For selected octogenarians with unmanageable cardiac symptoms, operation may be an effective therapeutic option.