Diagnostic Value of 123I-Betamethyl-p-Iodophenyl-Pentadecanoic Acid (BMIPP) Single Photon Emission Computed Tomography (SPECT) in Patients With Chest Pain-Comparison With Rest-Stress 99mTc-Tetrofosmin SPECT and Coronary Angiography-

Diagnostic Performance of CMR, SPECT, and PET Imaging for the Identification of Coronary Artery Disease: A Meta-Analysis

Background: Myocardial perfusion imaging modalities, such as cardiac magnetic resonance (CMR), single-photon emission computed tomography (SPECT), and positron emission tomography (PET), are well-established non-invasive diagnostic methods to detect hemodynamically significant coronary artery disease (CAD). The aim of this meta-analysis is to compare CMR, SPECT, and PET in the diagnosis of CAD and to provide evidence for further research and clinical decision-making.

Methods: PubMed, Web of Science, EMBASE, and Cochrane Library were searched. Studies that used CMR, SPECT, and/or PET for the diagnosis of CAD were included. Pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio with their respective 95% confidence interval, and the area under the summary receiver operating characteristic (SROC) curve were calculated.

Results: A total of 203 articles were identified for inclusion in this meta-analysis. The pooled sensitivity values of CMR, SPECT, and PET were 0.86, 0.83, and 0.85, respectively. Their respective overall specificity values were 0.83, 0.77, and 0.86. Results in subgroup analysis of the performance of SPECT with ²⁰¹Tl showed the highest pooled sensitivity [0.85 (0.82, 0.88)] and specificity [0.80 (0.75, 0.83)]. ^99mTc-tetrofosmin had the lowest sensitivity [0.76 (0.67, 0.82)]. In the subgroup analysis of PET tracers, results indicated that ¹³N had the lowest pooled sensitivity [0.83 (0.74, 0.89)], and the specificity was the highest [0.91 (0.81, 0.96)].

Conclusion: Our meta-analysis indicates that CMR and PET present better diagnostic performance for the detection of CAD as compared with SPECT.

Recent advances in metabolic imaging

Abnormalities in myocardial substrate metabolism play a central role in the manifestations of most forms of cardiac disease such as ischemic heart disease, heart failure, hypertensive heart disease, and the cardiomyopathy due to either obesity or diabetes mellitus. Their importance is exemplified by both the development of numerous imaging tools designed to detect the specific metabolic perturbations or signatures related to these different diseases, and the vigorous efforts in drug discovery/development targeting various aspects of myocardial metabolism. Since the prior review in 2005, we have gained new insights into how perturbations in myocardial metabolism contribute to various forms of cardiac disease. For example, the application of advanced molecular biologic techniques and the development of elegant genetic models have highlighted the pleiotropic actions of cellular metabolism on energy transfer, signal transduction, cardiac growth, gene expression, and viability. In parallel, there have been significant advances in instrumentation, radiopharmaceutical design, and small animal imaging, which now permit a near completion of the translational pathway linking in-vitro measurements of metabolism with the human condition. In this review, most of the key advances in metabolic imaging will be described, their contribution to cardiovascular research highlighted, and potential new clinical applications proposed.

Ischaemic memory imaging using metabolic radiopharmaceuticals: overview of clinical settings and ongoing investigations

"Ischaemic memory" is defined as a prolonged functional and/or biochemical alteration remaining after a particular episode of severe myocardial ischaemia. The biochemical alteration has been reported as metabolic stunning. Metabolic imaging has been used to detect the footprint left by previous ischaemic episodes evident due to delayed recovery of myocardial metabolism (persistent dominant glucose utilization with suppression of fatty acid oxidation). β-Methyl-p-[(123)I]iodophenylpentadecanoic acid (BMIPP) is a single-photon emission computed tomography (SPECT) radiotracer widely used for metabolic imaging in clinical settings in Japan. In patients with suspected coronary artery disease but no previous myocardial infarction, BMIPP has shown acceptable diagnostic accuracy. In particular, BMIPP plays an important role in the identification of prior ischaemic insult in patients arriving at emergency departments with acute chest pain syndrome. Recent data also show the usefulness of (123)I-BMIPP SPECT for predicting cardiovascular events in patients undergoing haemodialysis. Similarly, SPECT or PET imaging with (18)F-FDG injected during peak exercise or after exercise under fasting conditions shows an increase in FDG uptake in postischaemic areas. This article will overview the roles of ischaemic memory imaging both under established indications and in ongoing investigations.

Novel iodinated tracers, MIBG and BMIPP, for nuclear cardiology

With the rapid growth of molecular biology, in vivo imaging of such molecular process (i.e., molecular imaging) has been well developed. The molecular imaging has been focused on justifying advanced treatments and for assessing the treatment effects. Most of molecular imaging has been developed using PET camera and suitable PET radiopharmaceuticals. However, this technique cannot be widely available and we need alternative approach. ¹²³I-labeled compounds have been also suitable for molecular imaging using single-photon computed tomography (SPECT) ¹²³I-labeled meta-iodobenzylguanidine (MIBG) has been used for assessing severity of heart failure and prognosis. In addition, it has a potential role to predict fatal arrhythmia, particularly for those who had and are planned to receive implantable cardioverter-defibrillator treatment. ¹²³I-beta-methyl-iodophenylpentadecanoic acid (BMIPP) plays an important role for identifying ischemia at rest, based on the unique capability to represent persistent metabolic alteration after recovery of ischemia, so called ischemic memory. Since BMIPP abnormalities may represent severe ischemia or jeopardized myocardium, it may permit risk analysis in CAD patients, particularly for those with chronic kidney disease and/or hemodialysis patients. This review will discuss about recent development of these important iodinated compounds.

Assessment of acute myocardial infarction: current status and recommendations from the North American society for Cardiovascular Imaging and the European Society of Cardiac Radiology

There are a number of imaging tests that are used in the setting of acute myocardial infarction and acute coronary syndrome. Each has their strengths and limitations. Experts from the European Society of Cardiac Radiology and the North American Society for Cardiovascular Imaging together with other prominent imagers reviewed the literature. It is clear that there is a definite role for imaging in these patients. While comparative accuracy, convenience and cost have largely guided test decisions in the past, the introduction of newer tests is being held to a higher standard which compares patient outcomes. Multicenter randomized comparative effectiveness trials with outcome measures are required.

Delayed recovery of fatty acid metabolism after transient myocardial ischemia: a potential imaging target for "ischemic memory"

The myocardium preferentially oxidizes free fatty acids for energy production. However, the dependency of this metabolic pathway on oxygen makes this process vulnerable to ischemia. The energy requirements of the myocardium are subsequently met by the oxidation of carbohydrates, particularly glucose. Recovery of fatty acid metabolism lags behind restoration of perfusion, resulting in the phenomenon of metabolic stunning. This decrease of fatty acid utilization following ischemia can be imaged with fatty acid radiotracers, particularly beta-Methyl-p-(123)I-iodophenyl pentadecanoic acid (BMIPP), which demonstrates markedly limited metabolism via beta-oxidation, resulting in prolonged retention in the cardiomyocyte. Thus, in patients presenting with chest pain and no prior myocardial infarction, abnormal BMIPP uptake at rest reflects metabolic alteration caused by the preceding ischemia, also termed ischemic memory.

Diagnostic significance of positive I-123 BMIPP despite negative stress Tl-201 myocardial imaging in patients with suspected coronary artery disease

BACKGROUND

There is frequently discordance in the interpretation of myocardial single-photon emission computed tomography images using both rest iodine-123 15-(p-iodophenyl)-3-(R,S) methylpentadecanoic acid (BMIPP) and stress thallium-201 ((201)Tl); that is, negative BMIPP vs positive (201)Tl studies. However, little attention has been paid to reverse discordance (ie, positive BMIPP despite negative stress (201)Tl).

METHODS AND RESULTS

In the present study 105 consecutive patients with suspected coronary artery disease (CAD) who underwent both rest BMIPP and stress (201)Tl imaging were evaluated. No patient with previous myocardial infarction was included. Scintigraphic studies revealed that BMIPP was in concordance with (201)Tl in 71 patients: both were positive in 38 and negative in 33, whereas both were discordant in 20 and reverse discordant in 14. In patients with reverse discordance, the pattern of BMIPP abnormality was segmental in 8 and spotty in 6; the former was related to coronary territory. Based on the BMIPP findings and clinical symptoms, 7 patients with positive BMIPP despite negative (201)Tl underwent coronary angiography: 3-vessel CAD was found in 3 patients, 2-vessel CAD in 1, coronary spasm in 2, and insignificant lesions in 1. In the remaining 7 patients, no cardiac event was observed during 2-year follow-up.

CONCLUSIONS

In patients showing positive BMIPP despite negative (201)Tl, a segmental BMIPP perfusion abnormality indicates a high likelihood for CAD, despite normal stress (201)Tl imaging. Thus, adding BMIPP to (201)Tl imaging may help to better identify patients with significant CAD, including multivessel disease.

Dual-isotope myocardial SPECT in patients with redefined myocardial infarction

BACKGROUND

According to the redefinition of myocardial infarction (MI) by the ESC/ACC Committee, patients with unstable angina (UA) without significant elevation of creatine kinase (CK) but with elevation of troponin T should be diagnosed as MI.

METHODS

One hundred and forty-six consecutive patients formerly diagnosed as UA, with peak CK levels<twice upper normal level, who underwent myocardial Thallium-201 (Tl; perfusion tracer) and (123)I-15-iodophenyl 3-methyl pentadecanoic acid (BMIPP; metabolism tracer) dual isotope single-photon emission computed tomography (SPECT), were retrospectively reclassified into redefined MI and UA groups according to the redefinition (troponin T: rapid bedside assay positive or quantitative level >0.10 ng/ml). Dual SPECT findings were analyzed qualitatively and quantitatively in blinded manner.

RESULTS

Forty-seven patients (32%) were redefined as MI and 99 patients (68%) were redefined as UA. On admission, there were small but statistically significant elevations in laboratory parameters such as white blood cell count, C-reactive protein, CK and CK-MB in the redefined MI group compared with the redefined UA group. The proportion of patients with perfusion and metabolic abnormalities was significantly higher in the redefined MI group (Tl defect 36% vs. 4%, odds ratio: 13.5, p<0.001; BMIPP defect 64% vs. 23%, odds ratio: 5.8, p<0.001). Semi-quantitative evaluation revealed that the total Tl and BMIPP scores were significantly higher in the redefined MI patients (p<0.001).

CONCLUSIONS

In the redefined MI patients, perfusion and metabolic abnormalities occurred frequently and more extensively. However, Tl/BMIPP dual SPECT had limited ability to detect minor myocardial infarcts classified as redefined MI. A more sensitive stratification combined with troponin T directed assignment should be established to incorporate the ongoing minor infarcts which could not be assessed by serial dual-scintigraphic evaluations.

Evaluation of Fatty Acid .BETA.-Oxidation in Patients With Prior Myocardial Infarction in Relation to Myocardial Blood Flow, Total Oxidative Metabolism, and Left Ventricular Wall Motion

BACKGROUND

Fatty acid metabolism in patients with myocardial infarction (MI) who undergo coronary reperfusion has not been fully elucidated and was investigated in the present study using positron emission tomography.

METHODS AND RESULTS

The clearance rate constant of 11C-acetate (acetate-Kmono) and that of 11C-palmitate (palmitate-Kmono) from the myocardium were calculated using a monoexponential equation in 14 patients with MI. A total of 155 regions of interest were classified based on coefficient of determination (R2) values of monoexponential curves for 11C-palmitate clearance: well fitted regions (R2>or=0.5) and poorly fitted regions (R2<0.5). Regional relative myocardial blood flow calculated from the initial distribution of 11C-acetate and left ventricular (LV) wall motion were also evaluated. Peak 11C-palmitate uptake (14,434+/-3,052 vs 12,016+/-3,088 counts/s, p<0.001) and percent clearance during acquisition (38.2+/-10.1 vs 23.6+/-11.4%, p<0.001) were significantly greater in the well fitted regions (n=111) than in the poorly fitted regions (n=44). Acetate-Kmono was significantly higher in the former than in the latter (0.0641+/-0.0099 vs 0.0476+/-0.0103 min-1, p<0.001). LV wall motion and regional relative blood flow were also significantly greater in the former regions. Palmitate-Kmono in the well fitted regions was significantly higher in normal LV wall motion areas than in hypokinesis areas (0.0363+/-0.0062 vs 0.0274+/-0.0057 min-1, p<0.001)

CONCLUSIONS

Maintenance of myocardial fatty acid beta-oxidation with better myocardial blood flow is substantial in the preservation of total myocardial oxidative metabolism and LV wall motion in patients with MI. The finding that the early-phase clearance of 11C-palmitate is fitted with a monoexponential curve may provide important information in the evaluation of myocardial fatty acid beta-oxidation.

Diagnostic Use of T2-Weighted Inversion-Recovery Magnetic Resonance Imaging in Acute Coronary Syndromes Compared With 99mTc-Pyrophosphate, 123I-BMIPP and 201TlCl Single Photon Emission Computed Tomography

BACKGROUND

The incidence of missed diagnoses of acute cardiac ischemia in the emergency department could be reduced by a new imaging modality. In the present study, the clinical significance of (99m)Tc-pyrophosphate (PYP), (123)I-beta-methyl-p-iodephenyl-pentadecanoic acid (BMIPP), (201)TlCl scintigraphy (imaging) and T2-weighted inversion-recovery magnetic resonance imaging (MRI) for the detection of culprit lesion in patients with acute coronary syndromes (ACS) was compared.

METHODS AND RESULTS

The study group comprised 18 patients with ACS: 12 patients with acute myocardial infarction (AMI) (11 males; mean age, 63+/-11 years) and 6 patients with unstable angina (UA) (3 males, mean age, 67+/-5 years). Of the 12 patients with AMI, 10 underwent (201)TlCl and PYP single photon emission computed tomography (SPECT) studies as a dual-energy acquisition ((201)TlCl/PYP) and 8 underwent (201)TlCl SPECT within 1 week of the BMIPP study. All 18 patients underwent BMIPP SPECT and MRI. The MRI pulse sequence was black blood turbo short-inversion-time inversion recovery (STIR) (breath-hold T2-weighted studies). The T2-weighted inversion-recovery MRI showed higher sensitivity and negative predictive value than PYP and (201)TlCl, and higher specificity and positive predictive value than BMIPP and (201)TlCl. The area under the receiver-operating characteristic curve for PYP, BMIPP, (201)TlCl and MRI was 0.787, 0.725, 0.731 and 0.878, respectively. The difference between the areas of MRI and BMIPP was significant (p<0.05).

CONCLUSION

Accurate detection of culprit lesion is improved by using MRI rather than BMIPP, particularly for patients with ACS.