Previous studies on delayed enhanced MRI for the detection of cardiac sarcoidosis.
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Cardiomyopathies↗
Biomedical subjects
Eiji Tadamura
Publications and source records attributed to Eiji Tadamura.
Comparison of myocardial blood flow induced by adenosine triphosphate and dipyridamole in patients with coronary artery disease.
Myocardial perfusion imaging with adenosine triphosphate (ATP) has been used increasingly to diagnose coronary artery disease (CAD) and assess risk for this disease. This study compared absolute myocardial blood flow (MBF) and myocardial flow reserve index (MFR) with ATP and dipyridamole (DIP) in patients with CAD. MBF was quantified by 15O-H2O PET in 21 patients with CAD (17 male, 4 female), aged 55 to 81 years. MBF was measured at rest, during intravenous injection of ATP (0.16 mg/kg/min), and again after DIP infusion (0.56 mg/kg). Regions of interest were drawn in nonischemic and ischemic segments based on findings from thallium-201 (201T1) scintigraphy and coronary angiography (CAG). Absolute MBF values and indexes of MFR were calculated in nonischemic and ischemic segments. Intravenous injection of ATP and DIP significantly increased MBF in nonischemic (2.4 +/- 0.9 and 2.1 +/- 0.8 ml/g/min, respectively; p < 0.01, for both) and in ischemic segments (1.3 +/- 0.4 and 1.5 +/- 0.4 ml/g/min, respectively; p < 0.01, for both). There was a significant difference in MBF values between ATP and DIP in nonischemic segments (p < 0.05), which was not observed in ischemic segments. In nonischemic segments, ATP produced higher MFR than DIP (2.1 +/- 0.8 and 1.8 +/- 0.7, respectively; p < 0.05), while no significant difference was observed in ischemic segments (1.5 +/- 0.6 and 1.7 +/- 0.3, respectively). ATP produced a greater hyperemia than DIP between the ischemic and nonischemic myocardium in patients with CAD. ATP is as effective as DIP for the diagnosis of CAD.
Adenosine Triphosphate↗
Cardiac functional analysis with multi-detector row CT and segmental reconstruction algorithm: comparison with echocardiography, SPECT, and MR imaging.
PURPOSE: To evaluate accuracy of cardiac functional analysis with multi-detector row computed tomography (CT) and segmental reconstruction algorithm over a range of heart rates. MATERIALS AND METHODS: Institutional review board approval was obtained. Informed consent was not required. Multi-detector row CT (500-msec rotation time, 8 x 1-mm detector collimation) and magnetic resonance (MR) imaging were performed in 50 patients (28 men, 22 women; age range, 46-84 years; mean age, 67 years). Two-dimensional echocardiography was performed in 41 patients, and electrocardiographically (ECG)-gated single photon emission computed tomography (SPECT) was performed in 27. End-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), and left ventricular (LV) mass were estimated with multi-detector row CT and compared with values estimated with MR imaging, which served as the reference standard. Additionally, EF values estimated with multi-detector row CT, echocardiography, and SPECT were compared with those estimated with MR imaging. Systemic error and degree of agreement of global functional parameters measured with MR imaging and other modalities were assessed. In a second analysis, linear regression analysis was added. RESULTS: EF estimated with multi-detector row CT agreed and correlated well with EF estimated with MR imaging (bias +/- standard deviation, -1.2% +/- 4.6; r = 0.96). Agreement and correlation were similar for EDV (-0.35 mL +/- 15.2; r = 0.97), ESV (1.1 mL +/- 8.6; r = 0.99), and LV mass (2.5 mL +/- 15.0; r = 0.96). Standard deviation of EF difference between multi-detector row CT and MR imaging was significantly less than that between echocardiography and MR imaging (P < .001) or that between SPECT and MR imaging (P < .001). CONCLUSION: Various LV functional parameters were measured with multi-detector row CT with a segmental approach, and measurements correlated and agreed with those obtained with MR imaging. Moreover, functional analysis with multi-detector row CT was more accurate than that with two-dimensional echocardiography or ECG-gated SPECT.
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Effectiveness of delayed enhanced MRI for identification of cardiac sarcoidosis: comparison with radionuclide imaging.
OBJECTIVE: The purpose of this study was to evaluate the usefulness of delayed enhanced MRI for detecting cardiac sarcoidosis and to clarify the relationship between the findings of MRI and those of radionuclide imaging. CONCLUSION: Delayed enhanced MRI is considered a useful method for the early identification of cardiac sarcoidosis. Delayed hyperenhancement is frequently associated with a reduction of regional wall motion and thallium-201 perfusion defects.
Cardiomyopathies↗
Myocardial metabolism of 123I-BMIPP under low-dose dobutamine infusion: implications for clinical SPECT imaging of ischemic heart disease.
PURPOSE: 123I-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (123I-BMIPP) is a fatty acid analog for single-photon emission computed tomography (SPECT) imaging that is mainly stored in the triglyceride pool. Low-dose dobutamine infusion has been reported to improve BMIPP uptake in the stunned myocardium, but the mechanism underlying this effect remains unclear. The purpose of this study was therefore to investigate the myocardial metabolism of 123I-BMIPP in the stunned myocardium under low-dose dobutamine infusion, and to elucidate the mechanism by which dobutamine improves BMIPP uptake. METHODS: Using open-chest dogs, stunned myocardium was induced by occlusion of the left anterior descending artery (LAD) for 30 min, with subsequent reperfusion (ischemia group, n=6). After direct injection of BMIPP into the LAD, myocardial extraction and retention were examined and metabolites evaluated (using high-performance liquid chromatography) during dobutamine infusion. The results in the ischemia group were compared with findings obtained in a control group under dobutamine infusion (n=6). RESULTS: Dobutamine infusion significantly increased both the rapid extraction (within 30 s) of BMIPP into the myocardium (control vs ischemia group: 48+/-19% vs 66+/-14%, p<0.05) and its subsequent retention (73+/-13% vs 85+/-8%, p<0.05). The metabolites from the myocardium consisted of back diffusion of nonmetabolized BMIPP, the alpha-oxidation metabolite, intermediate metabolites, and the full-oxidation metabolite. Among these metabolites, the full-oxidation metabolite decreased significantly (from 34.0+/-20.0% to 15.8+/-9.3%, p<0.05) in the stunned regions, though back diffusion of nonmetabolized BMIPP increased (from 51.3+/-21.9% to 71.3+/-10.1%, p<0.05). CONCLUSION: These results indicate that increased uptake of BMIPP in stunned myocardium is mainly due to decreased beta-oxidation in tissue and increased shunt retention of BMIPP in the triglyceride pool, and thereby provide further insight into the pathophysiology of stunned myocardium.
Animals↗
Effect of caffeine intake on myocardial hyperemic flow induced by adenosine triphosphate and dipyridamole.
UNLABELLED: The aims of this study were (a). to compare absolute myocardial blood flow (MBF) during adenosine triphosphate (ATP) infusion with that after dipyridamole administration without caffeine intake and (b). to evaluate the effect of caffeine intake on the hyperemic flow induced by these coronary vasodilator agents. METHODS: MBF was quantified with (15)O-labeled water and PET at rest, during ATP infusion (0.16 mg/kg/min for 9 min), and after dipyridamole administration (0.56 mg/kg over 4 min) after a 24-h abstinence from caffeine (baseline evaluation) in 10 healthy volunteers. Within 2 wk, the same PET studies were repeated after caffeine intake to evaluate the effect of caffeine on the hyperemic flow induced by these pharmacologic agents (caffeine study). Myocardial flow reserve (MFR), defined as the ratio of hyperemic to resting blood flow, was also evaluated. RESULTS: Resting MBF in baseline and caffeine studies did not differ significantly (0.79 +/- 0.29 vs. 0.75 +/- 0.31 mL/min/g, P = 0.88). Without caffeine intake, MBF during ATP infusion was significantly higher than that after dipyridamole administration (3.70 +/- 0.67 vs. 3.00 +/- 0.79 mL/min/g, P = 0.003), whereas there was no significant difference in MFR between ATP and dipyridamole stress (5.15 +/- 1.64 vs. 4.11 +/- 1.44, P = 0.07). After caffeine intake, the hyperemic flows induced by ATP and dipyridamole were not significantly different (1.68 +/- 0.37 vs. 1.52 +/- 0.40 mL/min/g, P = 0.50). MFR estimated by ATP and dipyridamole also did not differ significantly in the caffeine studies (2.44 +/- 0.88 vs. 2.25 +/- 0.94, P = 0.73). MBF during ATP infusion and after dipyridamole administration were significantly lower in the caffeine studies than that in the baseline evaluation (1.68 +/- 0.37 vs. 3.70 +/- 0.67 mL/min/g, P < 0.0001, and 1.52 +/- 0.40 vs. 3.00 +/- 0.79 mL/min/g, P < 0.0001, respectively). CONCLUSION: This study demonstrates that ATP has the potential to induce greater hyperemia than dipyridamole, whereas hyperemic responses to ATP and dipyridamole are similarly attenuated after caffeine intake. These findings suggest that abstinence from caffeine before ATP stress testing may be needed.
Adenosine Triphosphate↗
The effect of nitroglycerin on myocardial blood flow in various segments characterized by rest-redistribution thallium SPECT.
UNLABELLED: The use of nitrates is reported to be effective in viability detection in scintigraphic perfusion imaging. The purpose of the study was to evaluate the effect of nitroglycerin (NTG) on myocardial blood flow (MBF) and coronary vascular resistance (CVR) in various segments characterized by rest-redistribution (201)Tl SPECT. METHODS: Twenty-three patients with coronary artery disease underwent rest-redistribution (201)Tl SPECT and (15)O-labeled water PET at rest and after NTG spray (0.3 mg). In addition, 11 healthy volunteers were also studied using PET. RESULTS: NTG did not change global MBF in the volunteers or in the patients. In segments with normal (201)Tl uptake and in those with a severe irreversible (201)Tl defect, NTG significantly reduced MBF without changing CVR. NTG reduced CVR in segments with a reversible (201)Tl defect (141 +/- 50 to 114 +/- 29 mm Hg/[mL/min/g], P = 0.004) and in those with a mild-to-moderate irreversible (201)Tl defect (165 +/- 64 to 149 +/- 60 mm Hg/[mL/min/g], P = 0.003), while maintaining MBF. CONCLUSION: NTG preferentially reduces CVR in the viable myocardium with ischemia. After NTG, tracer uptake in the ischemic myocardium will be relatively increased compared with that in the nonviable and nonischemic myocardium, leading to improvements in viability detection.
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[Cardiac imaging including nuclear medicine, MRI, and MDCT].
Nuclear cardiology has played a significant role in the diagnosis and risk stratification of patients with coronary artery disease. MRI and multidector-row CT (MDCT) has recently been introduced in the field of clinical cardiology. For the management of patients with suspected coronary artery disease, it is important to understand the advantages and disadvantages of various imaging modalities. This review discusses the current roles and problems of these imaging modalities.
Acute Disease↗
Composite arterial Y graft has less coronary flow reserve than independent grafts.
BACKGROUND: It is not known whether a composite Y graft of the left internal thoracic artery can provide sufficient blood flow to the whole left coronary system. The aim of this study was to compare regional myocardial blood flow (MBF) and coronary flow reserve after coronary artery bypass grafting using arterial composite Y graft or independent arterial grafts. METHODS: Positron emission tomography was performed at rest and after dipyridamole infusion using oxygen-15-labeled water 2 weeks after coronary artery bypass grafting. Regional MBF was calculated in seven segments of the left ventricle. Coronary flow reserve was defined as the ratio of MBF after dipyridamole infusion to MBF at rest. In the Y graft group (n = 22), a free arterial graft to obtuse marginal arteries was anastomosed to the proximal side of in situ left internal thoracic artery, which was anastomosed to the left anterior descending artery. In the independent graft group (n = 13), left anterior descending and obtuse marginal arteries were independently revascularized using in situ left internal thoracic artery and a free arterial graft. RESULTS: There was no difference between the groups in MBF at rest. Coronary flow reserve in the Y graft group was lower than that in the independent group in the anterobasal (1.43 +/- 0.07 versus 1.90 +/- 0.13, p = 0.038), apical (1.24 +/- 0.06 versus 1.64 +/- 0.12, p = 0.003), septal (1.34 +/- 0.05 versus 1.75 +/- 0.13, p = 0.023), and lateral regions (1.19 +/- 0.04 versus 1.66 +/- 0.09, p = 0.001). CONCLUSIONS: Although arterial composite Y graft improved MBF at rest, it was not as effective as independent grafts for improving coronary flow reserve soon after coronary artery bypass grafting.
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A Tc-99m-labeled long chain fatty acid derivative for myocardial imaging.
C-11- and I-123-labeled long chain fatty acid derivatives have been reported as useful radiopharmaceuticals for the estimation of myocardial fatty acid metabolism. We have reported that Tc-99m-labeled N-[[[(2-mercaptoethyl)amino]carbonyl]methyl]-N-(2-mercaptoethyl)-6-aminohexanoic acid ([(99m)Tc]MAMA-HA), a medium chain fatty acid derivative, is metabolized by beta-oxidation in the liver and that the MAMA ligand is useful for attaching to the omega-position of fatty acid derivatives as a chelating group for Tc-99m. On the basis of these findings, we focused on developing a Tc-99m-labeled long chain fatty acid derivative that reflected fatty acid metabolism in the myocardium. In this study, we synthesized a dodecanoic acid derivative, MAMA-DA, and a hexadecanoic acid derivative, MAMA-HDA, and performed radiolabeling and biodistribution studies. [(99m)Tc]MAMA-DA and [(99m)Tc]MAMA-HDA were prepared using a ligand-exchange reaction. Biodistribution studies were carried out in normal mice and rats. Then, a high initial uptake of Tc-99m was observed, followed by a rapid clearance from the heart. The maximum heart/blood ratio was 3.6 at 2 min postinjection of [(99m)Tc]MAMA-HDA. These kinetics were similar to those with postinjection of p-[(125)I]iodophenylpentadecanoic acid. Metabolite analysis showed [(99m)Tc]MAMA-HDA was metabolized by beta-oxidation in the body. In conclusion, [(99m)Tc]MAMA-HDA is a promising compound as a long chain fatty acid analogue for estimating beta-oxidation of fatty acid in the heart.
Animals↗
Quantitative fluorine 18 deoxyglucose uptake by myocardial positron emission tomography in rats.
BACKGROUND: In vivo quantitative assessment of positron emission tomography (PET) with 2-deoxy-2-[fluorine 18]fluorodeoxyglucose (FDG) for rat heart has not been explored because of the theoretical limitation of spatial resolution. Our objective was to assess whether FDG uptake measured by PET is correlated with tissue radioactivity of FDG in rat heart directly measured by an automated gamma counter. METHODS AND RESULTS: Ten Sprague-Dawley rats were used for echocardiographic assessment and FDG-PET. Rats were sacrificed immediately after PET scanning, and the radioactivity of FDG in 4 segmental tissue samples of the middle transverse section was measured. Quantitative PET values in a total of 40 regions of interest, in which partial volume effect was corrected based on the phantom study and wall thickness obtained by echocardiogram, were compared with radioactivity of the corresponding 40 tissue samples. Linear regression analysis revealed that tissue radioactivity of FDG was well correlated with the quantitative PET value (Y = 1.17X; r = 0.985, P <.0001). CONCLUSIONS: Quantitative FDG-PET for rat heart is a reliable approach for assessing glucose metabolism in vivo after correction is made for partial volume effect. These results can be used for various models of heart disease with repeated studies over the disease process in the same animal.
Animals↗
Primary cardiac lymphoma demonstrated by delayed contrast-enhanced magnetic resonance imaging.
Delayed contrast-enhanced magnetic resonance (MR) imaging that nullifies the signal of normal myocardium produces great differences in myocardial signal intensity between normal and infarcted myocardium. A case of primary cardiac lymphoma is presented in which delayed contrast-enhanced MR imaging clearly identified the localization and extension of a lymphoma infiltrating the myocardium.
Contrast Media↗
Demonstration of cardiac involvement of sarcoidosis by contrast-enhanced multislice computed tomography and delayed-enhanced magnetic resonance imaging.
Delayed-enhanced magnetic resonance (MR) imaging has recently been shown to be effective in detecting cardiac sarcoidosis. Two cases in which contrast-enhanced multislice computed tomography imaging clearly identified the localization and extension of cardiac sarcoidosis as delayed-enhanced MR imaging are presented.
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