Positron emission tomography--usefulness in assessing myocardial viability.

Positron emission tomography (PET) using N-13 ammonia and F-18 fluorodeoxyglucose (FDG) has been used to evaluate myocardial viability in comparison with thallium-201 single photon emission computed tomography (SPECT), and left ventricular wall motion in comparison with contrast ventriculography. Forty patients with anterior myocardial infarction underwent stress and delayed resting perfusion imaging using Tl-201 SPECT and ammonia PET, a glucose metabolism study using FDG PET, and wall motion assessment with left ventriculography. Out of a total of 600 segments of left ventricular imaging, SPECT demonstrated 197 fixed perfusion defects, 99 with redistribution on delayed imaging and 304 normal segments. Of 197 segments with fixed defects, 24 (12%) were normal and 71 (36%) ischemic according to PET criteria. Nineteen of 28 with infarction and all of 12 with non-Q wave infarction showed a viable myocardium. Left ventricular wall motion was significantly better in patients with normal PET findings compared with those with ischemia or scar on PET. Post-PTCA PET revealed improved ammonia PET in 6 of 11 patients but reduced FDG uptake was noted only in 3. These data suggests that Tl-201 SPECT significantly underestimates myocardial viability and that PET imaging is a promising tool for assessing the presence of salvaged myocardium.     

Metabolic imaging using F18-fluorodeoxyglucose to assess myocardial viability

Over the past 10 years, F18-fluorodeoxyglucose (FDG) imaging with positron emission tomography (PET) has emerged as an important technique in the delineation of myocardial viability. Using this technique it has become possible to predict recovery of ventricular function after revascularization in patients with chronic coronary artery disease. Data from long-term (although retrospective) follow-up studies have demonstrated that patients with viable myocardium on FDG PET who do not undergo revascularization are prone to cardiac events, including cardiac death and non-fatal infarction. The same studies have pointed out that patients with viable tissue on FDG PET, who do undergo revascularization, improve substantially in symptoms related to congestive heart failure. To allow FDG imaging in centers without PET equipment, recent studies have evaluated the use of FDG imaging with single photon emission computed tomography (SPECT) and 511 keV collimators. Preliminary data using this alternative approach are promising, but need further confirmation. In this review the experience with FDG imaging (using either PET or SPECT) in the assessment of tissue viability in patients with coronary artery disease will be discussed.     

99Tcm-MIBI 心肌灌注显像及18F-FDG PET心肌代谢显像探测左心室室壁瘤心肌存活性的临床价值

目的 评估99锝m-甲氧基异腈(99Tcm-MIBI)单光子发射计算机断层(SPECT)心肌灌注显像及18F-脱氧葡萄糖(FDG)正电子发射断层(PET)心肌代谢显像探测左心室室壁瘤(室壁瘤)心肌存活性的临床价值.方法 46例确诊为室壁瘤合并左心功能不全[左心射血分数(LVEF)36%±7%],行99Tcm-MIBI SPECT+18F-FDG PET显像,并接受血运重建术的患者,随访(80±27)个月.根据室壁瘤是否有存活心肌[灌注-代谢不匹配分(MMS)≥2.0分]以及是否行室壁瘤切除术,将患者分为4个小组:室擘瘤无存活心肌(A组):血运重建术为Al组(n=8),血运重建术+瘤切除术为A2组(n=15);窒壁瘤有存活心肌(B组):血运重建术为B1组(n=10),血运重建术+瘤切除术为B2组(n=13).结果 A1、A2、B1、B2 4个组心脏事件发生率分别为25%(2/8),40%(6/15).20%(2/10)和31%(4/13)(P＞0.05).除A1组外,其他各组的术后左心功能均得到明显改善(P＜0.05).多因素logistic回归分析筛选出与术后LVEF改善相关的独立影响因素,为左心室的MMS(OR=2.34,95% CI 1.08～5.06,P＜0.05),非室壁瘤部位的心肌灌注分(OR=0.24.95% CI 0.07～0.85,P＜0.05)和远端血管病变(OR=0.008,95% CI 0.001～0.560.P＜0.05).结论 室壁瘤接受血运重建术的患者,长期预后良好.室壁瘤部位有存活心肌的患者,单纯的血运重建术也可以明显改善左心功能,且与心肌存活的量相关.     

F-18-fluorodeoxyglucose positron emission tomography imaging-assisted management of patients with severe left ventricular dysfunction and suspected coronary disease: a randomized, controlled trial (PARR-2).

OBJECTIVES: We conducted a randomized trial to assess the effectiveness of F-18-fluorodeoxyglucose (FDG) positron emission tomography (PET)-assisted management in patients with severe ventricular dysfunction and suspected coronary disease. BACKGROUND: Such patients may benefit from revascularization, but have significant perioperative morbidity and mortality. F-18-fluorodeoxyglucose PET can detect viable myocardium that might recover after revascularization. METHODS: Included were patients with severe left ventricular (LV) dysfunction and suspected coronary disease being considered for revascularization, heart failure, or transplantation work-ups or in whom PET was considered potentially useful. Patients were stratified according to recent angiography or not, then randomized to management assisted by FDG PET (n = 218) or standard care (n = 212). The primary outcome was the composite of cardiac death, myocardial infarction, or recurrent hospital stay for cardiac cause, within 1 year. RESULTS: At 1 year, the cumulative proportion of patients who had experienced the composite event was 30% (PET arm) versus 36% (standard arm) (relative risk 0.82, 95% confidence interval [CI] 0.59 to 1.14; p = 0.16). The hazard ratio (HR) for the composite outcome, PET versus standard care, was 0.78 (95% CI 0.58 to 1.1; p = 0.15); for patients that adhered to PET recommendations for revascularization, revascularization work-up, or neither, HR = 0.62 (95% CI 0.42 to 0.93; p = 0.019); in those without recent angiography, for cardiac death, HR = 0.4 (95% CI 0.17 to 0.96; p = 0.035). CONCLUSIONS: This study did not demonstrate a significant reduction in cardiac events in patients with LV dysfunction and suspected coronary disease for FDG PET-assisted management versus standard care. In those who adhered to PET recommendations and in patients without recent angiography, significant benefits were observed. The utility of FDG PET is best realized in this subpopulation and when adherence to recommendations can be achieved.     

Relationship of extent of revascularization with angina at one year in the Bypass Angioplasty Revascularization Investigation (BARI)

OBJECTIVES: To determine the relative degree of revascularization obtained with bypass surgery versus angioplasty in a randomized trial of patients with multivessel disease requiring revascularization (Bypass Angioplasty Revascularization Investigation [BARI]), one-year catheterization was performed in 15% of patients. BACKGROUND: Complete revascularization has been correlated with improved outcome after coronary artery bypass grafting (CABG) but not with percutaneous transluminal coronary angioplasty (PTCA). Relative degrees of revascularization after PTCA and surgery have not been previously compared and correlated with symptoms. METHODS: Consecutive patients at four BARI centers consented to recatheterization one year after revascularization. Myocardial jeopardy index (MJI), the percentage of myocardium jeopardized by > or =50% stenoses, was compared and correlated with angina status. RESULTS: Angiography was completed in 270 of 362 consecutive patients (75%) after initial CABG (n = 135) or PTCA (n = 135). Coronary artery bypass grafting patients had 3+/-0.9 distal anastomoses and PTCA patients had 2.4+/-1.1 lesions attempted at initial revascularization. At one year, 20.5% of CABG patients had > or =1 totally occluded graft and 86.9% of vein graft, and 91.6% of internal mammary artery distal anastomotic sites had <50% stenosis. One year jeopardy index in surgery patients was 14.1+/-11%, 46.6+/-20.3% improved from baseline. Initial PTCA was successful in 86.9% of lesions and repeat revascularization was performed in 48.4% of PTCA patients by one year. Myocardial jeopardy index one year after PTCA was 25.5+/-22.8%, an improvement of 33.8+/-26.1% (p<0.01 for greater improvement with CABG than PTCA). At one year, 29.6% of PTCA patients had angina versus 11.9% of surgery patients, p = 0.004. One-year myocardial jeopardy was predictive of angina (odds ratio 1.28 for the presence of angina per every 10% increment in myocardial jeopardy, p = 0.002). Randomization to PTCA rather than CABG also predicted angina (odds ratio 2.19, p = 0.03). CONCLUSIONS: In this one-year angiographic substudy of BARI, CABG provided more complete revascularization than PTCA, and CABG likewise improved angina to a greater extent than PTCA.     

Prediction of functional improvement of ischemic myocardium with (123I-BMIPP SPECT and 99mTc-tetrofosmin SPECT imaging: a study of patients with large acute myocardial infarction and receiving revascularization therapy.

BACKGROUND: (18)F-fluorodeoxyglucose (FDG) positron-emission tomography (PET) is assumed to be the most useful method of evaluating the viability of the myocardium, but its use is limited by the need for a cyclotron. In the present study, the ability of a combination of (99m)Tc-tetrofosmin (TF) and (123)I-beta-methyliodophenyl pentadecanoic acid (BMIPP) single-photon emission computed tomography (SPECT), a combination of (18)F-FDG PET and (123)I-BMIPP SPECT, and a combination of (18)F-FDG PET and (99m)Tc-TF SPECT were compared to predict functional improvement of ischemic myocardium after a large acute myocardial infarction (AMI). METHODS AND RESULTS: Ten patients with large AMI were studied by (99m)Tc-TF SPECT, (123)I-BMIPP SPECT and (18)F-FDG PET within 3 weeks. Six months later, (99m)Tc-TF imaging was performed. All patients underwent successful revascularization, and had no restenosis. Regional tracer uptake was scored using a 4-point scale in 20 segments of the SPECT and PET images. When the defect score of (123)I-BMIPP SPECT exceeded the defect score of (99m)Tc-TF SPECT or (18)F-FDG PET by 1 point or more, and when the defect score of (99m)Tc-TF SPECT exceeded the defect score of (18)F-FDG PET by 1 point or more, the segment was considered to show mismatching. When the defect score was the same in 2 tracers, the segment was considered to show matching. (99m)Tc-TF imaging at 3 weeks and 6 months used quantitative gated SPECT (QGS) to score wall motion using a 6-point scale (-1= dyskinesis, 0= akinesis, 1= severe hypokinesis, 2= moderate hypokinesis, 3= mild hypokinesis, and 4= normokinesis). The sensitivity of the combination of (123)I-BMIPP and (99m)Tc-TF imaging in predicting functional improvement was 61%, that of (18)F-FDG PET and (123)I-BMIPP SPECT was 94%, and that of (18)F-FDG PET and (99m)Tc-TF SPECT was 76%. The specificity of the combination of (123)I-BMIPP and (99m)Tc-TF imaging in predicting functional improvement was 83%, that of (18)F-FDG PET and (123)I-BMIPP SPECT was 40%, and that of (18)F-FDG PET and (99m)Tc-TF SPECT was 49%. The accuracy of the combination of (123)I-BMIPP and (99m)Tc-TF imaging in predicting functional improvement was 70%, that of (18)F-FDG PET and (123)I-BMIPP SPECT was 71%, and that of (18)F-FDG PET and (99m)Tc-TF SPECT was 63%. CONCLUSION: The combination of (123)I-BMIPP and (99m)Tc-TF imaging is a practical modality for predicting the functional improvement of ischemic myocardium after a large AMI.     

Prediction of functional recovery after revascularization in coronary artery disease using (18)F-FDG and (123)I-BMIPP SPECT

STUDY OBJECTIVES: Clinical studies comparing fatty acid and glucose metabolism in relation to functional recovery of ischemic myocardium after coronary revascularization are scarce. This study evaluated the recovery of regional and global left ventricular function after coronary revascularization in relation to uptake patterns of beta-methyl-iodophenyl-pentadecanoic acid (BMIPP) and fluorodeoxyglucose (FDG) in patients with ischemic myocardial dysfunction. METHODS: Patients with ischemic regional wall motion abnormality underwent baseline viability imaging with (18)F-FDG, (123)I-BMIPP, and (99m)Tc- methoxyisobutylisonitrile, and the regions with evidence for maintained tissue viability were revascularized. Mismatch of uptake score between two different single-photon emission CT (SPECT) images in the same myocardial region was graded as low or high mismatch. Regional and global left ventricular functional changes after revascularization were analyzed in relation to mismatch severity and difference of total uptake score in each SPECT image pair. A total of 33 vessels in 30 patients related to the asynergic regions were revascularized, and a total of 100 myocardial segments perfused by the revascularized vessels were analyzed. RESULTS: Segments showing high metabolic mismatch (FDG/BMIPP) had lowest regional wall motion score at baseline, representing the most severely impaired ischemic myocardium, and had highest improvement in regional wall motion score after revascularization. Difference of total uptake score between FDG and BMIPP showed a significant positive correlation with difference of ejection fraction between pre- and postrevascularization (r = 0.774, p < 0.0001). CONCLUSIONS: Combined metabolic SPECT imaging with FDG and BMIPP has the potential to identify severely impaired ischemic myocardium leading to more efficient therapeutic management of patients with coronary artery disease.     

Attenuation-corrected 99mTc-tetrofosmin single-photon emission computed tomography in the detection of viable myocardium: comparison with positron emission tomography using 18F-fluorodeoxyglucose

Objectives. The purpose of this study was to assess the efficacy of attenuation-corrected (AC) technetium-99m (^99mTc)-tetrofosmin single-photon emission computed tomography (SPECT) in detecting viable myocardium compared to ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET).Background. The role of ^99mTc-labeled perfusion tracers in the assessment of myocardial viability remains controversial. Attenuation artifacts affect the diagnostic accuracy of SPECT images.Methods. Twenty-four patients with coronary artery disease (mean left ventricular ejection fraction 30%) underwent resting ^99mTc-tetrofosmin SPECT and FDG PET imaging. Both AC and non–attenuation-corrected (NC) SPECT images were generated.Results. Using a 50% threshold for viability by FDG PET, the percentage of concordant segments of viability between ^99mTc-tetrofosmin and FDG on the patient basis increased from 79.8% ± 14.0% (mean ± SD) on the NC images to 90.8% ± 10.6% on the AC images (p = 0.002). The percentage of ^99mTc-tetrofosmin defect segments within PET-viable segments, an estimate for the degree of underestimation of viability, decreased from 19.8% ± 15.2% on the NC images to 9.7% ± 12.6% on the AC images (p = 0.01). Similar results were obtained when a 60% threshold was used to define viability by FDG PET. When the anterior-lateral and inferior-septal regions were separately analyzed, the effect of attenuation correction was significant only in the inferior-septal region.Conclusions. The results indicate that AC ^99mTc-tetrofosmin SPECT improves the detection of viable myocardium mainly by decreasing the underestimation of viability particularly in the inferior-septal region, although some underestimation/overestimation of viability may still occur even with attenuation correction.     

心肌灌注显像对冠心病患者心脏不良事件预测价值的初步探讨

目的初步探讨心肌灌注显像可逆缺损与不可逆缺损对心脏不良事件的预测价值。方法追踪了５０例进行血运重建术治疗［冠状动脉旁路术（ＣＡＢＧ）或经皮冠状动脉腔内成形术（ＰＴＣＡ）］和７８例单纯药物治疗冠心病患者,并于术前或药物治疗前行冠状动脉造影、术后或药物治疗前进行了运动静息心肌灌注断层显像（ＳＰＥＣＴ）,随诊时间为６～１２０个月,平均（３６３±２２４）个月。结果１２８例患者ＳＰＥＣＴ示：可逆性缺损（心肌缺血）５２例,固定性缺损（心肌梗塞）２２例,正常５４例。随访期间发生心脏事件分别为３９例（７５％）、３例（１３６％）、４例（７４％）。单因素时序检验（Ｌｏｇｒａｎｋ）显示,可逆性缺损组与固定性缺损组、正常组对心脏事件的预测差异有显著性（Ｐ＜０００１）,固定性缺损（心肌梗塞）组与正常组差异无显著性。Ｃｏｘ回归分析表明：ＳＰＥＣＴ显像图上有可逆缺损（心肌缺血）是心脏事件的独立的预测因素（Ｐ＜０００１,风险比ＯＲ＝１５１,９５％的可信限ＣＩ为５２２～４２９０）。结论运动静息心肌灌注显像对心肌缺血、心肌梗塞后的心脏不良事件有较高的预测价值。     

Role of F-18 FDG positron emission tomography (PET) in the assessment of myocardial viability

Positron emission tomography (PET) is a functional imaging technique with important clinical applications in cardiology, oncology, and neurology. In cardiac imaging, its role has been extensively evaluated in the noninvasive diagnosis of coronary artery disease and in the determination of prognosis. Additionally, cardiac PET with F-18 fluorodeoxyglucose (FDG) is very helpful in selection of patients with coronary artery disease and left ventricular dysfunction who would benefit from coronary artery revascularization. Cardiac PET is arguably considered by many as a gold standard in this particular application. F-18, unlike other positron emitters, has a reasonably long physical half-life, which permits its distribution through commercial radiopharmacies. This is further facilitated by increasing popularity of FDG PET in oncology, which makes cardiac FDG PET a practical option for hospitals and outpatient centers equipped with PET scanners. In addition, gamma camera single photon emission computed tomography (SPECT) systems, routinely used in nuclear medicine departments, can be equipped with coincidence circuit or high-energy 511 KeV collimators, providing a cost-effective means of FDG cardiac imaging. Myocardial utilization of glucose as a substrate is variable, depending, among other factors, on serum levels of glucose and insulin. Therefore, patient preparation is important in obtaining good-quality images and in turn allowing for accurate interpretation of myocardial viability. There are various protocols to choose from that provide diagnostic image quality in both diabetic and nondiabetic patients. Mismatch between blood flow and FDG metabolism, an indicator of viable, jeopardized myocardium, can predict postrevascularization improvement in left ventricular function, symptomatic relief, and long-term survival.     

Relation of change in wall motion and glucose metabolism after coronary artery bypass grafting--assessment with positron emission tomography

Regional myocardial glucose metabolism was assessed by positron emission tomography (PET) in stunned myocardium. PET perfusion and metabolic imaging using N-13 ammonia and F-18 deoxyglucose (FDG) was performed before and 5-7 weeks after coronary artery bypass grafting (CABG) in 23 patients with coronary artery disease. Of 22 asynergy segments showing increased FDG uptake preoperatively, the postoperative PET showed a decrease in FDG uptake in 16 segments (73%) and persistent uptake in 6 segments (27%). The improvement in asynergy was observed in all of the segments showing postoperative decrease in FDG uptake, while it was observed in only 50% of those with persistent FDG uptake (p less than 0.01). On the other hand, 4 of 5 segments showing a new FDG uptake postoperatively revealed deterioration of wall motion abnormality. These data suggest that an increase in exogenous glucose utilization may often persist in postischemic myocardium. Improvement in regional function seems to be associated with the improvement in metabolic abnormality after CABG.     

BMIPP imaging to assess functional outcome in patients with acute and chronic left ventricular dysfunction

Assessment of myocardial viability is an important clinical issue for patient management during the acute and chronic stages of myocardial infarction. BMIPP (15-(p-iodophenyl)-3-(R,S)-methyl pentadecanoic acid) is a free fatty acid analogue which is trapped in the myocardium, thus permitting for metabolic imaging with single photon emission computerized tomography (SPECT). Less BMIPP than flow tracers that may be observed in the areas of infarction, may reflect the metabolic shift from fatty acid to glucose utilization in ischaemic myocardium. In this sense, the combined imaging of BMIPP and a flow tracer with SPECT may provide similar and important information as fluoro-18 deoxyglucose (FDG) and positron emission tomography (PET) regarding the assessment of myocardial viability. The purpose of this article is to review the clinical impact of BMIPP in patients with acute and with chronic left ventricular dysfunction for the identification of jeopardized but viable myocardium and the prediction of the functional outcome.     

Assessment of reversible myocardial dysfunction in chronic ischaemic heart disease: comparison of contrast-enhanced cardiovascular magnetic resonance and a combined positron emission tomography-single photon emission computed tomography imaging protocol.

AIMS: The aim of the study was to compare, in patients with chronic ischaemic cardiomyopathy, contrast-enhanced cardiovascular magnetic resonance (ce-CMR) imaging and a combined (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET) and (99m)Tc-sestamibi single-photon emission computed tomography (SPECT) protocols for the prediction of functional recovery after revascularization, as assessed by cine CMR. METHODS AND RESULTS: Twenty-nine patients with ischaemic cardiomyopathy (ejection fraction 32 +/- 10%) were investigated with ce-CMR and PET/SPECT. For the assessment of global and regional functions, cine CMR was performed at baseline and at 6 months follow-up. For ce-CMR, the segmental extent of hyperenhancement (SEH) was quantitated, and for PET/SPECT, different viability categories were defined according to a validated quantitative protocol. Functional improvement was related to the SEH by ce-CMR, as well as to the viability categories by PET/SPECT. Sensitivity and specificity for the prediction of functional recovery at follow-up was 97 and 68% for ce-CMR and 87 and 76% for PET/SPECT. The positive predictive value was identical for both techniques (73%). However, ce-CMR achieved a higher negative predictive value (93 vs. 77%, respectively), indicating that ce-CMR may be superior to PET/SPECT for the identification of segments unlikely to recover function after revascularization. Both methods had a similar yield in the prediction of global functional improvement. CONCLUSION: ce-CMR is comparable with a PET/SPECT imaging protocol for the prediction of regional and global functional improvement after revascularization. However, ce-CMR may be superior to nuclear imaging for the identification of segments that are unlikely to recover function at follow-up.     

Late outcome of multivessel coronary artery disease after angioplasty or bypass surgery

Background. Results from randomized trials to determine optimal treatment for patients with multivessel coronary disease are not yet available. Thus, the early and late outcomes of 191 PTCA and 221 CABG patients done in 1985-86 were evaluated. Methods and Results. CABG patients selected had more coronary risk factors and more severe coronary artery disease compared to PTCA patients. Comparison of the initial outcome showed that clinical success without major cardiovascular events was similar (93.7% for PTCA vs. 90.0% for CABG; p=n.s.). Five year followup was obtained in 99.0% of PTCA patients and 94.4% of CABG patients. In the PTCA group, 89.8% were alive, 4.8% had sustained an MI, and repeat revascularization was required in 46.8%. In the CABG group, 87.1% were alive, 3.2% had had a MI, and 3.5% required repeat revascularization. Statistical comparison demonstrated no difference between the groups in survival or late cardiac events, but rate of repeat revascularization was significantly higher for PTCA patients (p less than 0.0001). Incompleteness of revascularization (p<0.01) was independently associated with an increased need for repeat revascularization in the PTCA group. In the CABG group, depressed left ventricular function (p less than 0.001) and female sex (p<0.01) were associated with lower survival rates. An analysis of cost per patient showed that the strategies were comparable. Conclusions. PTCA and CABG in multivessel disease patients have similar early results and comparable rates of survival and late cardiac events. Significantly more repeat revascularization is required in PTCA patients to maintain these results.(ABSTRACT TRUNCATED AT 250 WORDS)     

Myocardial viability in chronic ischemic heart disease: comparison of contrast-enhanced magnetic resonance imaging with (18)F-fluorodeoxyglucose positron emission tomography

OBJECTIVES: We sought to compare contrast-enhanced magnetic resonance imaging (ceMRI) with nuclear metabolic imaging for the assessment of myocardial viability in patients with chronic ischemic heart disease and left ventricular (LV) dysfunction. BACKGROUND: Contrast-enhanced MRI has been shown to identify scar tissue in ischemically damaged myocardium. METHODS: Twenty-six patients with chronic coronary artery disease and LV dysfunction (mean ejection fraction 31 +/- 11%) underwent (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET), technetium-99m tetrofosmin single-photon emission computed tomography (SPECT), and ceMRI. In a 17-segment model, the segmental extent of hyperenhancement (SEH) by ceMRI, defined as the relative amount of contrast-enhanced tissue per myocardial segment, was compared with segmental FDG and tetrofosmin uptake by PET and SPECT. RESULTS: In severely dysfunctional segments (n = 165), SEH was 9 +/- 14%, 33 +/- 25% (p < 0.05), and 80 +/- 23% (p < 0.05) in segments with normal metabolism/perfusion, metabolism/perfusion mismatch, and matched defects, respectively. Segmental glucose uptake by PET was inversely correlated to SEH (r = -0.86, p < 0.001). By receiver operator characteristic curve analysis, the area under the curve was 0.95 for the differentiation between viable and non-viable segments. At a cutoff value of 37%, SEH optimally differentiated viable from non-viable segments defined by PET. Using this threshold, the sensitivity and specificity of ceMRI to detect non-viable myocardium as defined by PET were 96% and 84%, respectively. CONCLUSIONS: Contrast-enhanced MRI allows assessment of myocardial viability with a high accuracy, compared with FDG-PET, in patients with chronic ischemic heart disease and LV dysfunction.     

硝酸甘油介入~(99m)Tc-甲氧基异丁基异腈心肌灌注断层显像评估存活心肌

目的　评估静息及硝酸甘油介入99mTc 甲氧基异丁基异腈 (99mTc MIBI)心肌灌注断层显像在存活心肌检测中的应用价值。方法　对心肌梗死 2 0例于血管重建术前分别行静态及硝酸甘油介入显像 ,血管重建术后 1个月重复静息心肌显像并进行对比分析。结果　 2 0例共有 1 4 4个异常灌注的心肌节段 ,硝酸甘油介入后有 72个心肌节段灌注改善 ,血管重建术后有 77个心肌节段灌注改善。硝酸甘油介入改善的 72个节段术后有 62个节段改善 ;而术前无改善的 72个节段术后只有 1 5个节段改善 ,硝酸甘油介入99mTc MIBI心肌灌注显像对存活心肌预测的阳性预测值为 86 .1 % ,阴性预测值为 79.2 % ,预测准确率为 82 .6%。结论　硝酸甘油介入99mTc MIBI心肌灌注断层显像是可供临床检测心肌存活的安全、有价值的方法     

Positron emission tomography and recovery following revascularization (PARR-1): the importance of scar and the development of a prediction rule for the degree of recovery of left ventricular function

OBJECTIVES: The aim of this study was to determine whether the extent of viability or scar is important in the amount of recovery of left ventricular (LV) function, and to develop a model for predicting recovery after revascularization that could be tested in a randomized trial. BACKGROUND: F-18-fluorodeoxyglucose (FDG) positron emission tomography (PET) is used to define viable myocardium in patients with coronary artery disease (CAD) and severe LV dysfunction and to guide revascularization decisions. Whether this approach improves clinical outcomes has not been tested in a randomized trial. Before doing so, an objective model for prediction of recovery is required. METHODS: A total of 82 patients with CAD and an ejection fraction (EF) < or =35% had FDG PET perfusion imaging before revascularization. Complete follow-up was available on 70 patients (86%). Patients had radionuclide angiograms at baseline and three months post-revascularization. RESULTS: Diabetes (p = 0.029), time to operation (p = 0.008), and scar score (p = 0.001) were significant independent predictors of the change in EF. Previous coronary artery bypass graft confounded the effect of age. There was a significant interaction between the perfusion tracer used and mismatch score (p = 0.02). The multivariable prediction model incorporating PET and clinical variables had a goodness of fit with p = 0.001. Across tertiles of scar scores (I, small: 0% to 16%; II, moderate: 16% to 27.5%; III, large: 27.5% to 47%), the changes in EFs were 9.0 +/- 1.9%, 3.7 +/- 1.6%, and 1.3 +/- 1.5% (p = 0.003: I vs. III), respectively. CONCLUSIONS: In patients with severe LV dysfunction, the amount of scar was a significant independent predictor of LV function recovery after revascularization. A combination of PET and clinical parameters predicts the degree of recovery. This model is being applied in a large randomized controlled trial to determine the effectiveness of therapy guided by FDG PET.     

Positron emission tomography using fluorine-18 deoxyglucose in evaluation of coronary artery bypass grafting

To assess the clinical value of positron emission tomography (PET) in the evaluation of coronary artery bypass grafting (CABG), PET perfusion and metabolic imaging using nitrogen-13 ammonia and fluorine-18 deoxyglucose (FDG) was performed before and 5 to 7 weeks after CABG in 22 patients with coronary artery disease. Postoperative improvement in hypoperfusion was observed more often in the metabolically active segments (62%) than in the inactive segments (27%) on the preoperative PET study (p less than 0.05). Similarly, the postoperative lessening of wall motion abnormality was observed more often in the metabolically active segments (78%) than in the inactive segments (22%) (p less than 0.001). Of 19 asynergic segments showing increased FDG uptake before operation, the postoperative PET revealed a decrease in FDG uptake in 13 (68%) and persistent uptake in 6 (32%). The improvement in asynergy was observed in all the segments that showed a postoperative decrease in FDG uptake, but in only 50% of those with persistent uptake (p less than 0.01). On the other hand, 4 of 5 segments showing a new FDG uptake after operation revealed further wall motion abnormality. Furthermore, the segments metabolically active before operation were more likely to have patent grafts (95%) than the metabolically inactive segments (70%) (p less than 0.05). Thus, preoperative metabolic imaging using PET appears to be useful for predicting the response to CABG. Improvement in metabolic derangement was associated with improvement in regional function after CABG.     

Comparison of sestamibi single-photon emission computed tomography with positron emission tomography for estimating left ventricular myocarclial viability

Technetium-99m methoxyisobutyl isonitrile (technetium-99m sestamibi [MIBI]) is distributed in the myocardium according to blood flow. Reports comparing stress rest sestamibi protocols with reinfection thallium or resting fluorodeoxyglucose (FDG), or both, in patients with coronary artery disease have shown appreciable discordance regarding myocardial viability in these settings. We performed this analysis with regard to regional comparisons within discordant segments and made comparisons in a subset of patients who underwent revascularization. Thirty-seven patients with coronary artery disease had single-photon emission computed tomography MIBI, N-13 ammonia/¹⁸FDG positron emission tomography (PET), and radionuclide ventriculography performed at rest. One hundred two segments were viable and 29 were nonviable by both MIBI and FDG. The concordance was 71%. In MIBI nonviable/ FDG viable segments, most of the discordance was in the inferior wall. In MIBI nonviable discordant segments, FDG accurately predicted an increase in percent regional ejection fraction (preoperative 36% [± 5 SE] to postoperative 48% [± 5.5 SE] [p < 0.0006]). MIBI underestimates myocardial viability as assessed by PET. Seventy-one percent of myocardial segments were concordant by both quantitative sestamibi single-photon emission computed tomography and FDG PET. Discordance in MIBI nonviable segments was predominantly in the inferior wall. PET can be helpful in detecting myocardial viability in patients suspected of having had MIBI nonviability in the inferior wall.     

Clinical outcome of patients with advanced coronary artery disease after viability studies with positron emission tomography.

OBJECTIVE. The aim of this study was to determine the prognostic significance of perfusion-metabolism imaging in patients undergoing positron emission tomography for myocardial viability assessment. BACKGROUND. Positron emission tomography using nitrogen-13 ammonia and 18fluorodeoxyglucose to assess myocardial blood flow and metabolism has been shown to predict improvement in wall motion after coronary artery revascularization. The prognostic implications of metabolic imaging in patients with advanced coronary artery disease have not been investigated. METHODS. Eighty-two patients with advanced coronary artery disease and impaired left ventricular function underwent positron emission tomographic imaging between August 1988 and March 1990 to assess myocardial viability before coronary artery revascularization. RESULTS. Forty patients underwent successful revascularization. Patients who exhibited evidence of metabolically compromised myocardium by positron emission tomography (decreased blood flow with preserved metabolism) who did not undergo subsequent revascularization were more likely to experience a myocardial infarction, death, cardiac arrest or late revascularization due to development of new symptoms than were the other patient groups (p less than 0.01). Concordantly decreased flow and metabolism in segments of previous infarction did not affect outcome in patients with or without subsequent revascularization. Those with a compromised myocardium who did undergo revascularization were more likely to experience an improvement in functional class than were patients with preoperative positron emission tomographic findings of concordant decrease in flow and metabolism. CONCLUSIONS. Positron emission tomographic myocardial viability imaging appears to identify patients at increased risk of having an adverse cardiac event or death. Patients with impaired left ventricular function and positron emission tomographic evidence for jeopardized myocardium appear to have the most benefit from a revascularization procedure.