Evaluation Of Myocardial Viability Research Articles

Label-free Evaluation of Myocardial Infarct in Surgically Excised Ventricular Myocardium by Raman Spectroscopy

Understanding the viability of the ischemic myocardial tissue is a critical issue in determining the appropriate surgical procedure for patients with chronic heart failure after myocardial infarction (MI). Conventional MI evaluation methods are; however, preoperatively performed and/or give an indirect information of myocardial viability such as shape, color, and blood flow. In this study, we realize the evaluation of MI in patients undergoing cardiac surgery by Raman spectroscopy under label-free conditions, which is based on intrinsic molecular constituents related to myocardial viability. We identify key signatures of Raman spectra for the evaluation of myocardial viability by evaluating the infarct border zone myocardium that were excised from five patients under surgical ventricular restoration. We also obtain a prediction model to differentiate the infarcted myocardium from the non-infarcted myocardium by applying partial least squares regression-discriminant analysis (PLS-DA) to the Raman spectra. Our prediction model enables identification of the infarcted tissues and the non-infarcted tissues with sensitivities of 99.98% and 99.92%, respectively. Furthermore, the prediction model of the Raman images of the infarct border zone enabled us to visualize boundaries between these distinct regions. Our novel application of Raman spectroscopy to the human heart would be a useful means for the detection of myocardial viability during surgery.

P5627Utility of longitudinal peak systolic strain by speckle tracking for the evaluation of myocardial viability and severity after acute coronary syndrome

P5627Utility of longitudinal peak systolic strain by speckle tracking for the evaluation of myocardial viability and severity after acute coronary syndrome

Regional Myocardial Perfusion Disturbance in Experimental Chronic Chagas Cardiomyopathy.

Altered myocardial perfusion is a common finding in chronic Chagas cardiomyopathy (CCC), but its underlying histologic changes have not been elucidated. We investigated the occurrence of myocardial perfusion defects (MPDs) and the correlated regional changes to histology in an experimental model of CCC in hamsters. Methods: Female Syrian hamsters (n = 34) were infected with 3.5 × 104 to 105 trypomastigote forms of Trypanosoma cruzi, Y strain, and 6-10 mo afterward underwent in vivo imaging including resting 99mTc-sestamibi SPECT, segmental and global left ventricular function assessment using 2-dimensional echocardiography, and 18F-FDG PET for evaluation of myocardial viability. Histologic analysis included quantification of fibrosis, inflammatory infiltration, and the diameter and density of myocardial microcirculation. Results: MPDs were present in 17 (50%) of the infected animals. Histologic analysis revealed no transmural scar in segments with an MPD, and normal or mildly reduced 18F-FDG uptake, indicating viable myocardium. Infected animals with an MPD, in comparison to infected animals without an MPD and control animals, showed a lower left ventricular ejection fraction (P = 0.012), a higher wall motion score index (P = 0.004), and a higher extent of inflammatory infiltration (P = 0.018) but a similar extent of fibrosis (P = 0.15) and similar microvascular diameter and density (P > 0.05). Segments with an MPD (n = 65), as compared with normally perfused regions in the same animal (n = 156), showed a higher wall motion score index (P = 0.005) but a similar extent of inflammatory infiltration, a similar extent of fibrosis, and a similar microvascular diameter and density. Conclusion: Resting MPDs are frequent in experimental CCC and are associated with myocardial inflammation but do not designate scar tissue, corresponding to regions with metabolically viable myocardium.

Role of Cardiac Magnetic Resonance Imaging in the Assessment of Myocardial Viability in Patients with Coronary Artery Disease

AbstractBackground: The principal goal of the assessment of myocardial viability is to identify patients whose symptoms, exercise capacity, and long-term prognosis may improve after revascularization. Contrast enhanced cardiac MRI has devel-oped as a promising imaging modality for the assessment of myocardial viability which provides direct imaging of necrotic tissue with high contrast and high spatial resolution. Aim of the work was to assess role of cardiac MRI as a non-invasive tool in the evaluation of myocardial viability in patients with coronary artery disease.Aim of Study: To assess the role of cardiac MRI as a non-invasive tool in the evaluation of myocardial viability in patients with coronary artery disease.Material and Methods: The study included 25 patients diagnosed as having Coronary Artery Disease (CAD), (age range, 28-68 years ±11.29). All selected patients were subjected to cardiac MRI examination using 1.5-T MR system for studying myocardial function and viability. Comparison was made between echocardiography and cardiac MRI regarding segmental wall motion using the 17-segment model of the American Heart Association for assessment of myocardial function. Delayed-enhancement MRI was performed to deter-mine myocardial viability and scarring while black blood T2W sequence with fat suppression was done to detect cases with acute infarction. Microvascular occlusion was diagnosed using early Gadolinium enhancement sequence.Results: Good agreement between cardiac MRI and echocardiography regarding segmental wall motion with p-value of 0.065. Sensitivity and specificity of cardiac MRI for detecting SWMA were 93.6%, and 44.4% respectively. Myo-cardial viability was evaluated by cardiac MRI with the use of end-diastolic wall thickness, imaging of early and late enhancement after contrast administration. Late gadolinium enhancement allowed assessing state of myocardium and visualizing myocardial scar with its quantification. Two segments showed 1-25% transmural extent of myocardial wall infarction, while 120 segments showed 71-100% extent and 261 segments showed no enhancing scar.Conclusion: Cardiac MR imaging is an effective and reliable method for the evaluation of myocardial function as compared to echocardiography. Also it is effective and reliable method for the evaluation of myocardial viability being able to assess both the infarct size and trans-murality and accord-ingly helps to predict functional recovery after revasculariza-tion.

New Imaging-derived Biomarkers Based on Tridimensional CTA/MRI Hybrid Models for Complex Assessment of Myocardial Viability after Myocardial Infarction – the HYBRIDHEART Study

Abstract Hybrid imaging represents a combination of two different imaging techniques resulting in a single image that contains all the information provided by the two investigations. Hybrid imaging tends to improve the accuracy of the diagnosis in many diseases. Coronary computed tomography angiography (CCTA) has unquestionable abilities in highlighting coronary artery diseases (CAD). Cardiac magnetic resonance imaging (MRI) also has a powerful predictive role in assessing the functionality of the myocardial tissue. The aim of the study is to develop new imaging markers for a complex evaluation of myocardial viability (MV) after an acute myocardial infarction (AMI), using hybrid technology. Material and methods: This study will enroll 100 patients at one month after an AMI. CCTA, MRI, 3D echocardiography, and blood tests will be performed in all patients. All the acquisitions will be processed using a supercomputer, and MV and other parameters will be assessed on hybrid images. A secondary objective will be to correlate the level of inflammatory markers with the outcome of patients, left ventricular function, ischemic time, and the rate of major adverse cardiovascular events.

Central diastolic pressure exponential decay constant and subendocardial flow supply.

Central diastolic pressure exponential decay constant and subendocardial flow supply.

Cardiac Magnetic Resonance and Myocardial Viability: Why Is It so Important?

Abstract For a better assessment of ischemic heart diseases, myocardial viability should be quantified. Current studies underline the importance and the evolution of several techniques and methods used in the evaluation of myocardial viability. Taking into account these considerations, the aim of this manuscript was to present the recent points of view regarding myocardial viability and its clinical significance in patients with ischemic cardiomyopathies and left ventricular dysfunction. On the other hand, the manuscript points out the role of magnetic resonance imaging (MRI), one of the most useful noninvasive imaging techniques, in the assessment of myocardial viability. By comparing the advantages and disadvantages of cardiac MRI, its usefulness can be better appreciated by the clinician. In the following years, it is considered that MRI will be an indispensable imaging tool in the assessment of ischemic heart disease, guiding interventions for revascularization and long-term risk stratification in patients with stable angina or myocardial infarction.

Is cardiac magnetic resonance necessary for prediction of left ventricular remodeling in patients with reperfused ST-segment elevation myocardial infarction?

As cardiac magnetic resonance imaging (CMR) has become widely used for evaluation of myocardial viability after acute myocardial infarction, the additional value of CMR parameters for prediction of left ventricle (LV) remodeling has been receiving interest. The aim of the study was to investigate the additional predictive value of CMR parameters for LV remodeling after successful reperfusion of ST-segment elevation myocardial infarction (STEMI) using multiple predictive models. LV remodeling was defined as ≥20% increase in end-diastolic volume at 6 month follow-up echocardiography. Using multiple stepwise regression analysis, conventional risk model was classified as following; model 1 (clinical factors), model 2 (model 1 + angiographic factors), model 3 (model 2 + echocardiographic factors) and CMR-added model; model 4 (model 3 + CMR factors). Among 262 enrolled patients, 25.1% showed LV remodeling. There were significant increments of c-statistics from the predictive model 1 to model 3 (AUC; 0.675 [0.60-0.75], 0.708 [0.64-0.78], 0.756 [0.69-0.82], respectively. all p < 0.05). However, model 4, which added the CMR variables, did not show any increase in predictive value compared with model 3 (AUC; 0.763 [0.70-0.83] versus 0.756 [0.69-0.82], p = 0.11). During the 28.2months of median follow up, the incidence of hospitalization for heart failure was significantly higher in the patients with LV remodeling (6.1% vs. 0.5%, p = 0.02). CMR parameters did not provide incremental predictive value above the assessment by conventional echocardiography-based risk model in patients with STEMI.

Novel 18F-Labeled 1-Hydroxyanthraquinone Derivatives for Necrotic Myocardium Imaging.

Rapid detection and precise evaluation of myocardial viability is necessary to aid in clinical decision making whether to recommend revascularization for patients with myocardial infarction (MI). Three novel 18F-labeled 1-hydroxyanthraquinone derivatives were synthesized, characterized, and evaluated as potential necrosis avid imaging agents for assessment of myocardial viability. Among these tracers, [18F]FA3OP emerged as the most promising compound with best stability and highest targetability. Clear PET images of [18F]FA3OP were obtained in rat model of myocardial infarction and reperfusion at 1 h after injection. In addition, the possible mechanisms of [18F]FA3OP for necrotic myocardium were discussed. The results showed [19F]FA3OP may bind DNA to achieve targetability to necrotic myocardium by intercalation. In summary, [18F]FA3OP was a more promising "hot spot imaging" tracer for rapid visualization of necrotic myocardium.

Abstract 11929: Simultaneous Assessment of Myocardial Viability With 18 F-fluorodeoxyglucose Uptake and Late Gadolinium Enhancement by PET/MRI

Introduction: Both 18 F-fluorodeoxyglucose (FDG) PET and late gadolinium enhancement on cardiac MRI (LGE-CMR) have been utilized for myocardial viability evaluation. However, the association between these 2 modalities has not been fully investigated. The aim of this study was to compare FDG PET and LGE-MRI findings simultaneously using an integrated PET/MRI. Methods: Twelve participants (age 68.8 ± 7.9 years old, 11 males, left ventricular ejection fraction 40.5 ± 15.0%) with old myocardial infarction were enrolled. Total 204 segments were analyzed according to the 17-segment model. FDG PET/MRI was performed for each participant under hyperinsulinaemic-euglycemic state. The FDG uptake was semiquantitatively measured as %uptake. The transmural extent of LGE-CMR was evaluated by a 5-point scoring system (0 = 0%, 1 = 1-25%, 2 = 26-50%, 3 = 51-75%, 4 = 76-100%). Left ventricular (LV) wall thickness at end-diastolic phase and LV wall thickening were also measured by CMR. Viable myocardium was defined as less than 50% of the transmural extent of LGE-CMR. Results: Relative FDG uptake and the transmural extent of LGE-CMR were significantly correlated (P &lt; 0.0001, Spearman ρ = -0.63). Relative FDG uptake was correlated with LV wall thickness (P = 0.003, ρ = 0.22) and LV wall thickening (P &lt; 0.0001, ρ = 0.59). Receiver operating characteristic analysis demonstrated that the best cut-off value of FDG uptake to predict myocardial viability was 63% (area under the curve 0.90). When the cut-off value set to 63%, sensitivity was 81.6%, specificity was 80.8%, and accuracy was 81.4%. Conclusions: Relative FDG uptake was comparable to the transmural extent of LGE-CMR in assessing myocardial viability. Simultaneous evaluation using the integrated PET/MRI is feasible and may provide novel insights into evaluation of the myocardial viability.

Incremental value of PET and MRI in the evaluation of cardiovascular abnormalities.

The cardiovascular system is affected by a wide range of pathological processes, including neoplastic, inflammatory, ischemic, and congenital aetiology. Magnetic resonance imaging (MRI) and positron emission tomography (PET) are state-of-the-art imaging modalities used in the evaluation of these cardiovascular disorders. MRI has good spatial and temporal resolutions, tissue characterization and multi-planar imaging/reconstruction capabilities, which makes it useful in the evaluation of cardiac morphology, ventricular and valvar function, disease characterization, and evaluation of myocardial viability. FDG-PET provides valuable information on the metabolic activity of the cardiovascular diseases, including ischemia, inflammation, and neoplasm. MRI and FDG-PET can provide complementary information on the evaluation of several cardiovascular disorders. For example, in cardiac masses, FDG-PET provides the metabolic information for indeterminate cardiac masses. MRI can be used for localizing and characterizing abnormal hypermetabolic foci identified incidentally on PET scan and also for local staging. A recent advance in imaging technology has been the development of integrated PET/MRI systems that utilize the advantages of PET and MRI in a single examination. The goal of this manuscript is to provide a comprehensive review on the incremental value of PET and MRI in the evaluation of cardiovascular diseases.Main Messages• MRI has good spatial and temporal resolutions, tissue characterization, and multi-planar reconstruction• FDG-PET provides valuable information on the metabolic activity of cardiovascular disorders• PET and MRI provide complementary information on the evaluation of cardiovascular disordersElectronic supplementary materialThe online version of this article (doi:10.1007/s13244-016-0494-5) contains supplementary material, which is available to authorized users.

Utility and safety of three-dimensional contrast low-dose dobutamine echocardiography in the evaluation of myocardial viability early after an acute myocardial infarction.

IntroductionThe aim of the study was to determine the utility and safety of three-dimensional contrast low-dose dobutamine echocardiography (3DCLDDE) in the evaluation of myocardial viability early after ST-elevation myocardial infarction (STEMI).Material and methodsWe prospectively evaluated a group of 100 consecutive patients. Myocardial viability was assessed using dobutamine echocardiography in 76 patients with segmental wall motion abnormalities, including 37 patients evaluated using 3DCLDDE and 39 patients evaluated using a standard low-dose dobutamine echocardiography protocol (LDDE), alternately.ResultsSingle ventricular ectopic beats were observed during the test in 1 (2.5%, 1, p = 1) patient in the 3DCLDDE group, while pain (1, p = 1) dyspnea (1, p = 1), single ventricular beats (2, p = 1), and complex ventricular arrhythmia (2, p = 0.49) were noted in 4 (10%) patients in the LDDE group. Five-year survival was 89% in the 3DCLDDE group and 87% in the LDDE group.Conclusions3DCLDDE and LDDE are equally safe and useful in patients after STEMI.

The Correlation between Left and Right Ventricular Ejection Fractions in Patients with Ischemic Heart Disease, Documented by Cardiac Magnetic Resonance Imaging

Introduction: The correlation between right and left ventricular ejection fractions (RVEF and LVEF, respectively) has been studied in only a small number of patients with a marked decrease in RVEF and LVEF. The aim of the present study was to compare LVEF and RVEF in patients with ischemic heart disease. RVEF and LVEF were measured by Cardiovascular Magnetic Resonance (CMR) imaging. Materials and Methods: This observational study was done in Ghaem general hospital in 2014.  LVEF and RVEF were measured in a series of 33 patients with ischemic heart disease, undergoing CMR for the evaluation of myocardial viability. The correlation between RVEF and LVEF in patients with ischemic heart disease was studied, using Pearson product-moment correlation coefficient analysis.  This study was done in Ghaem general hospital in 2014 with simple sapling. Results: Right ventricular end diastolic volume (186.33±58.90) and left ventricular end diastolic volume (121.72±61.64) were significantly correlated (r=0.223, P=0.005). Moreover, there was a significant correlation between right ventricular end systolic volume (88.18±40.90) and left ventricular end systolic volume (140.96±35.33) (r=0.329, P=0.000). The most significant association was observed between RVEF and LVEF (r=0.913, P=0.000). Conclusion: Based on the findings, RVEF and LVEF were significantly correlated in patients with ischemic heart disease, although this association was not always present in all cardiac patients. The cause of this discrepancy is still unknown.

Evaluation of Myocardial Viability with Delay-Enhanced Magnetic Resonance Imaging in the Ischemic Pig Models Compared with Histochemical and Pathological Analyses

Evaluation of Myocardial Viability with Delay-Enhanced Magnetic Resonance Imaging in the Ischemic Pig Models Compared with Histochemical and Pathological Analyses

Combination of contrast-enhanced cardiac MR and nuclear myocardial imaging in evaluation of myocardial viability in ischemic cardiomyopathy

Objective To explore the imaging characteristics and the complementarity of contrast- enhanced cardiac magnetic resonance CMR and nuclear myocardial perfusion/metabolic imaging in the evaluation of myocardial viability in patients with ischemic cardiomyopathy. Methods A total of 111 patients with diagnosed coronary artery disease and left ventricular dysfunction were retrospectively enrolled in this study. All patients underwent CMR and nuclear myocardial imaging within 1 month. Cine CMR was employed to evaluate cardiac function and wall motion. Contrast-enhanced CMR and myocardial perfusion/metabolic images were quantitatively assessed using a standard 17-segment and 5-score system. Dysfunctional segments were classified as viable or non- viable based on contrast- enhanced CMR and myocardial perfusion/metabolic imaging, respectively. No enhancement or sub-endocardial enhancement was defined as viable, while transmural enhancement was defined as non-viable. Severely matched perfusion/metabolism defects on nuclear imaging were assigned as non-viable while other patterns were considered as viable.Kappa index was calculated to evaluate the diagnostic concordance in assessing myocardial viability between contrast- enhanced CMR and myocardial perfusion/metabolic imaging. Results Among 1 887 segments in 111 patients, 80.3%(1 516/1 887) were dysfunctional. Of them, 63.3% (959/1 516) were viable and 36.7%(557/1 516) were non-viable on contrast-enhanced CMR, while 79.7%(1 208/1 516) were viable and 20.3% (308/1 516) were non-viable on nuclear myocardial imaging. The two modalities had a moderate concordance (Kappa=0.46, P<0.01). In segments with normal perfusion and metabolism, 73.9% (431/583) had various extent of enhancement but most of them(84.2%, 363/431) were subendocardial. On the other hand, 21.0% (117/557) segments with transmural enhancement had hibernating myocardium on nuclear imaging. Conclusions Contrast-enhanced CMR and nuclear myocardial imaging have a moderate concordance in the evaluation of myocardial viability in ischemic cardiomyopathy. Combination of the two modalities is expected to improve the diagnostic accuracy in assessing myocardial viability. Key words: Myocardium; Magnetic resonance imaging; Nuclear imaging; Myocardial ischemia

What do Polish interventional cardiologists know about indications and qualification for recanalisation of chronic total coronary artery occlusions?

Chronic total occlusions (CTO) are diagnosed in about 20% of patients with significant coronary artery disease. A disproportion between the high prevalence of CTOs and low rate of invasive treatment still exists. Technical difficulties, clinical uncertainties whether patients benefit from recanalisation, and a lack of knowledge of CTO may be responsible for this fact. To assess the knowledge of coronary arteries CTO among Polish interventional cardiologists. A self-designed questionnaire was used during two major Polish invasive cardiology workshops held in 2014. The study included 113 physicians, mostly cardiologists certified as independent operators. Average self-declared efficacy of CTO recanalisation was 63.5%. Most of the respondents agreed that the operator involved in the CTO recanalisation program should perform at least 30-50 procedures per year. Only 67% stated that before CTO revascularisation the evaluation of myocardial viability should be performed with dobutamine stress echocardiography as a preferred test. One third of the physicians agreed that CTO percutaneous coronary intervention (PCI) should not be performed directly after diagnostic angiography, and 51.5% believed that in patients with multi-vessel coronary artery disease PCI of CTO should be performed first. Multi-slice spiral computed tomography during the qualification and planning of the CTO revascularisation, in the opinion of 91% of the responders, should not be used before each procedure but could be useful in selected cases. Polish interventional cardiologists remains in compliance with current opinions about recanalisation of chronic coronary artery occlusions and the consensus of the EuroCTO Club, but there is still an unceasing need for further education and promotion of knowledge about CTOs.

Direct evaluation of myocardial viability and stem cell engraftment demonstrates salvage of the injured myocardium.

The mechanism of functional restoration by stem cell therapy remains poorly understood. Novel manganese-enhanced MRI and bioluminescence reporter gene imaging were applied to follow myocardial viability and cell engraftment, respectively. Human-placenta-derived amniotic mesenchymal stem cells (AMCs) demonstrate unique immunoregulatory and precardiac properties. In this study, the restorative effects of 3 AMC-derived subpopulations were examined in a murine myocardial injury model: (1) unselected AMCs, (2) ckit(+)AMCs, and (3) AMC-derived induced pluripotent stem cells (MiPSCs). To determine the differential restorative effects of the AMC-derived subpopulations in the murine myocardial injury model using multimodality imaging. SCID (severe combined immunodeficiency) mice underwent left anterior descending artery ligation and were divided into 4 treatment arms: (1) normal saline control (n=14), (2) unselected AMCs (n=10), (3) ckit(+)AMCs (n=13), and (4) MiPSCs (n=11). Cardiac MRI assessed myocardial viability and left ventricular function, whereas bioluminescence imaging assessed stem cell engraftment during a 4-week period. Immunohistological labeling and reverse transcriptase polymerase chain reaction of the explanted myocardium were performed. The unselected AMC and ckit(+)AMC-treated mice demonstrated transient left ventricular functional improvement. However, the MiPSCs exhibited a significantly greater increase in left ventricular function compared with all the other groups during the entire 4-week period. Left ventricular functional improvement correlated with increased myocardial viability and sustained stem cell engraftment. The MiPSC-treated animals lacked any evidence of de novo cardiac differentiation. The functional restoration seen in MiPSCs was characterized by increased myocardial viability and sustained engraftment without de novo cardiac differentiation, indicating salvage of the injured myocardium.

Immediate and remote results of endovascular treatment of patients with postinfarction cardiosclerosis

Two approaches in treatment of 131 patients with postinfarction cardiosclerosis are compared in the work. Tactics of "total" myocardial revascularization means restoration of coronary blood flow in all arteries with hemodynamically significant lesion while "selective" revascularization provides restoration of coronary blood flow only in those arteries which have a viable myocardium in their pool. It was concluded that restoration of coronary blood flow in patients after myocardial infarction permits to prevent postinfarction heart remodeling, development of heart failure thereby affecting on the prognosis. Evaluation of myocardial viability in the area of suggested surgery increases efficiency of revascularization, reduces number of implantable stents and decreases frequency of unfounded coronary interventions. Elimination of ischemia in the area of hibernation provides a rapid restoration of myocardial contractility in most of left ventricle segments with initially impaired kinetics. It was revealed that terms of contractility restoration of hibernating myocardium depend on duration of hibernation period up to revascularization.

Fusion of coronary angiography and stress echocardiography for myocardial viability evaluation.

Identification of viable myocardial tissue is important for patients with a low left ventricular ejection fraction, since revascularization is effective only if the affected region is viable. After cineangiographic identification of occluded coronary vessels, the myocardial viability is usually determined using cardiac MRI or SPECT. Alternatively, myocardial deformation imaging by echocardiography has been introduced that allows detection of viable myocardium directly within the catheterization laboratory. Multimodality fusion of coronary angiograms and echocardiograms was developed to match viable regions with areas affected by occluded vessels. Identification of corresponding myocardial regions in both coronary angiograms and ultrasound scans was performed using multimodality image fusion. Geometrically correct superposition of these images was done to allow direct identification of the involved myocardial regions. An electromagnetic tracking system was used as a common base for co-registration of the images. The system was tested using a phantom test device in a cardiac catheterization laboratory. A 2D projection error of 3.8±1.1 mm was achieved in trials using a cardiac phantom test object. Superimposition of the occluded coronary artery and the regional myocardial viability was achieved using automated multimodality fusion of coronary angiograms and stress echocardiograms with in vitro experiments. This system is promising for integrated single step angiography and angioplasty that may reduce procedure time, cost and length of hospitalization. Further testing in vivo is needed to verify and validate the system in a clinical setting.

Synthesis and biological evaluation of fatty acids conjugates bearing cyclopentadienyl-donors incorporated [99mTc/Re(CO)3]+ for myocardical imaging

Four 99mTc-labeled fatty acid analogs, 1b, 2b, 3b, 4b were synthesized by a double ligand transfer reaction and theirs potential were investigated. The radiochemical yield of the radiotracers was from 11.7% to 30.3% (no decay corrected). Those compounds were found to be chemically stable when incubated in SD rat serum for 3 h at 37 °C. The biodistribution studies in mice showed that high radioactivity accumulated of Tc-99m complexes were observed, followed by moderate clearance from the heart. The maximum heart/blood ratio was 5.7 at 15 min postinjection of 1b. Metabolite analysis showed 1b was not metabolized by β-oxidation in the heart. These results suggest that 1b may be a promising radiotracer for evaluation of myocardial viability.