MRI与正电子发射计算机体层、单光子发射计算机体层显像检测活性心肌的对比研究

目的评估各种影像学方法检测心肌活性的价值。方法建立慢性心肌缺血模型猪10只，按照美国心脏病协会推荐的方法将左心室分为16节段，分别于制作模型前和后1～2个月进行MR多技术联合应用扫描及正电子发射计算机体层显像(PET)、^201铊单光子发射计算机体层显像(^201Tl SPECT)检查，判断心肌缺血区和坏死区的大小，并与病理结果对照，了解各种方法的敏感性、特异性。结果7只动物顺利完成所有检查，共计112个节段。静息时MR电影扫描共有10个(8.93％)节段运动丧失，4个(3．57％)节段运动轻度减弱，2个(1.78％)节段运动明显减弱；负荷后MR电影扫描共有10个(8.93％)节段运动丧失；心肌灌注扫描见34个(30．36％)节段缺血，心肌活性扫描见12个(10.71％)节段坏死；PET检查见17个(15．18％)节段为梗死心肌；SPECT检查见9个(8.04％)节段为梗死心肌；氯化三苯基四氮唑(TTC)染色见14个(12．50％)节段为无红染的苍白色梗死区。PET检出的坏死节段多于MR心肌活性扫描(X^2=5，P=0．0253，Kappa=0．8028)和电影扫描(X^2=7，P=0．0082，Kappa=0.7079)，并有统计学意义；亦多于TTC染色显示的坏死节段，但无统计学意义(X^2=3，P=0．0833，Kappa=0．8879)；SPECT检出的坏死节段较TTC染色显示的节段少，并有统计学意义(X^2=5，P=0.0253，Kappa=0．7590)；MR电影检出的坏死节段较TTC染色显示的节段稍少，并有统计学意义(X^2=4，P=0．0455，Kappa=0、8100)；MR心肌活性扫描检出的坏死节段和TTC染色显示的坏死节段相比无统计学意义(X^2=2，P=0、1573，Kappa=0．9130)。以TTC染色结果为金标准，MR电影、MR心肌活性扫描、PET和SPECT检出无活性心肌的敏感性、特异性分别为71．43％、100．00％；85.71％、100．00％；100．00％、96．94％；64.29％、100．00％。结论MR心脏检查可结合形态、功能及灌注多种方法检测活性心肌，清晰显示心肌梗死的位置、程度，并可对左室室壁运动进行直观显示，且价格相对PET便宜；PET检查高估心肌坏死范围，且不能判断心肌梗死是透壁梗死还是心内膜下梗死；MRI和PET、病理结果均有较高一致性。     

MR多技术扫描检测活性心肌及其和心肌声学造影对比的临床研究

目的 评价MR多技术扫描和心肌声学造影（MCE）在检测心肌灌注、判断心肌存活中的作用。资料与方法 应用MR多技术扫描对36例冠心病患者进行检查,并将结果与冠状动脉造影、MCE结果对照。结果 共有81支冠状动脉狭窄≥70％,狭窄的冠状动脉供血区域为334个（57．99％）节段。MR心肌灌注扫描见268个（46．53％）节段呈缺血改变,MR心肌活性扫描见83个（14．4l％）节段心肌梗死。以冠状动脉造影结果为标准,MR心肌灌注扫描的敏感性为80．2％,特异性为100％,总符合率为88．5％,Kappa值为0．773。定性MCE检查共有202个（35．07％）节段呈缺血改变。以冠状动脉造影结果为标准,定性MCE的敏感性为60．5％,特异性为100％,总符合率为77．1％,Kappa值为0．563。MR心肌灌注扫描所发现的缺血节段比狭窄冠状动脉的供血节段少但无统计学意义（P=0．468）,MCE所发现的缺血节段比狭窄冠状动脉的供血节段少（P=0．000）;MR心肌灌注扫描检出缺血节段比MCE检出的多（P=0．000）。结论 MR多技术扫描可清晰显示心肌缺血或梗死的位置、程度,可重复性好,与冠状动脉造影结果的一致性较高。MCE为临床提供了元创、可重复地准确测定心肌缺血的新方法,但其评价方法具有一定主观性且低估心肌缺血的范围,检查者的经验和检查方法在一定程度上影响其准确性。     

急性心肌梗塞MR灌注成像和SPECT对照研究

目的 探讨MR灌注成像和SPECT检测存活心肌的价值.方法 对30例临床诊断为急性心肌梗塞的患者(共计510个心肌节段),进行MR心肌灌注扫描检查,包括MR心肌灌注首过时相及MR心肌灌注延迟扫描.将MR扫描结果与单光子发射计算机体层显像(SPECT)结果进行对照,所有病例均行X线冠状动脉造影检查证实.结果 MR心肌灌注首过时相扫描发现198个节段呈低灌注缺血改变,312个节段灌注正常;MR心肌灌注延迟扫描发现56个节段造影剂潴留呈梗死改变,454个节段为活性心肌.X线冠状动脉造影检查显示49支冠状动脉主干或其主要分支狭窄.SPECT检出的梗死节段比MR心肌灌注扫描检出的节段少,二者的差异具有统计学意义.结论 MR心肌灌注扫描对存活心肌的诊断、预后评估具有重要意义.     

磁共振多技术联合应用检测存活心肌的实验研究

目的　评估磁共振多技术联合应用检测心肌存活的价值。材料与方法　选择慢性心肌缺血模型猪 2 0只 ,分别于制作模型前、后 1～ 2个月行磁共振多技术联合应用扫描 (形态、电影扫描、心肌灌注和心肌活性扫描 ) ,判断心肌缺血区和坏死区的大小 ,并与病理结果对照了解其准确性。结果　MRI检查发现 2 0只猪中有 3只形态扫描见左室侧壁变薄 ;负荷电影扫描见 11(11/2 0 )只猪左心室收缩功能正常 ,有 9(9/2 0 )只静息时左室节段不同程度运动减弱 (n =7)或丧失 (n =2 )。多巴酚丁胺负荷电影扫描检测到 7只猪左室节段功能改善 ,但有 2只猪无明显改善。心肌灌注扫描有 13只猪共 4 7.8个节段缺血 ,心肌活性扫描有 8只猪共 2 3.6个节段坏死 ,病理检查发现共有 7只猪 2 3个节段坏死。与MRI延迟强化区所显示的梗死区一致 ,差异无统计学意义 (t=0 .0 4 5 ,P >0 .0 5 )。结论　磁共振多技术联合应用可有效检出缺血、坏死心肌 ,并准确判断其程度和范围     

缺血心肌动物模型PET和SPECT显像及组织学对比研究

目的评估^201TI SPECT及^18F-脱氧葡萄糖（FDG）PET显像对模型猪心肌活力的鉴别。方法健康家猪12头，其中10头于冠状动脉左旋支起始处放置Ameriod环，饲养28d形成慢性心肌缺血动物模型（另2头作正常对照），行^201TI SPECT心肌灌注显像和^18F—FDG PET心肌代谢显像并与HE染色病理学改变进行比较。结果81个心肌节段中，^18F—FDG心肌显像示心肌有活力的节段为73个（90．1％），明显高于^201TI心肌显像所示的62个（76．5％），差异有显著性（P〈0．05）。HE染色结果示有心肌活力的节段为74个（91．3％），与^18F—FDG心肌显像所示结果差异无显著性（P〉0．05）。结论^18F—FDGPET心肌显像检测心肌活力的准确性明显高于^201TI SPECT心肌显像。     

特发性扩张型心肌病合并甲状腺功能减退加重心肌损伤的影像学评价

目的通过^99Tcm-MIBI心肌灌注SPECT／^18F—FDG心肌代谢PET显像和心脏MRI延迟增强成像（cMRI—LGE）,探讨特发性扩张型心肌病（IDC）合并甲状腺功能减退（简称甲减）与心肌损伤的关系。方法2010年10月至2012年12月诊断为IDC的连续病例63例[男42例,女21例,平均年龄（52±11）岁]入选,患者均进行血浆TT3、TT4、FT3、FT4和TSH全自动化学发光免疫法测定、^99Tcm-MIBI心肌灌注SPECT／^18F—FDG心肌代谢PET显像和cMRI—LGE。利用标准17节段模型进行心肌节段分析,灌注／代谢图像分成4种类型：正常灌注／代谢、灌注／代谢不匹配、灌注／代谢轻中度匹配、灌注／代谢完全匹配;cMRI-LGE图像分为无延迟强化、壁间强化和透壁强化。通过x^2检验进行分组数据的比较。结果根据所测血浆激素水平,患者被分成甲状腺功能（简称甲功）正常组（53例）和甲减组（10例）。甲功正常组正常灌注／代谢的心肌节段数所占的比例明显高于甲减组：71.8％（647／901）和57．6％（98／170）,x^2=13．50,P〈0．001;而灌注／代谢不匹配的心肌节段比例则低于甲减组：17．8％（160／901）和31．2％（53／170）x^2=16．20,P〈0．001。甲功正常组cMRI—LGE无延迟强化的心肌节段比例明显高于甲减组,分别为88．0％（793／901）和69．4％（118／170）,x^2=35．70,P〈0．001;但壁间强化的心肌节段比例则低于甲减组,分别为4．8％（43／901）和24．1％（41／170）,x^2=74．70,P〈0．001。结论^99Tc^m-MIBI心肌灌注SPECT／^18F—FDG心肌代谢PET显像和cMRI—LGE证实甲减能够加重IDC患者的心肌损伤。SPECT／PET可以检测出更多的慢性缺血／存活心肌,而cMRI-LGE可以检测出更多的心肌纤维化病变,两者结合能提供更全面的心肌损伤信息。     

硝酸甘油介入99Tcm-tetrofosmin SPECT与18F-FDG PET显像评估心肌活力比较

目的 比较硝酸甘油介入^99Tc^m-tetrofosmin SPECT心肌血流灌注显像与^18F-FDG PET心肌代谢显像评估心肌活力的价值。方法 既往有心肌梗死史伴左心功能不全经冠状动脉造影确诊为冠心病的患者36例，行二日法静息和硝酸甘油介入^99Tc^m-tetrofosmin SPECT显像，并在1周内再行^18F-FDG PET心肌代谢显像及静息超声心动图检查。将左心室分成13个节段，分析超声心动图室壁运动，并分析相同节段^99Tc^m-tetrofosmin与^18F-FDG的相对摄取比值，以^18Tc^m-tetrofosmin摄取比值55％，^18F—FDG摄取比值50％为判断心肌活力有无的阈值。以k统计比较3种方法的一致性。结果 超声心动图示131个节段呈无运动或反向运动。^99Tc^m-tetrofosmin静息显像示其中78个节段（60％）心肌有活力，53个节段（40％）无活力。该53个节段中14个（26％）在硝酸甘油介入后可见再填充，余39个节段无改变。在^18F—FDGPET显像中，硝酸甘油介入显像再填充节段的心肌放射性摄取明显增高。再填充节段与无填充节段比较，心肌FDG摄取分别为（76±15）％和（58±17）％，差异有统计学意义（P〈0．01）。硝酸甘油介入显像中，92个心肌节段（70％）有活力，39个无活力。tetrofosmin静息显像评估心肌活力与FDG PET显像比较，k值为0．35，而硝酸甘油介入^99Tc^m-tetrofosmin SPECT与^18F—FDGPET显像结果比较，k值为0．53。结论 硝酸甘油介入^99Tc^m-tetrofosmin SPECT显像可提高对心肌活力的检测能力，与^18F—FDG PET心肌代谢显像有很好的一致性。     

^201Tl与^13N—NH3、^18F—PDG PET心肌显像判断存活心肌的对比研究

目的 比较再注射^201Tl心肌显像与联合应用^13N-NH3及^18F-脱氧葡萄糖（FDG）心肌PET显像判断存活心肌的临床价值。方法 20例心肌梗死患者，行^201Tl SPECT负荷、再分布、再注射显像及^13N-NH3`^18F-FDG PET心肌显像。将左室分成9个节段，以视觉评价法对放射性分布进行4级评分。获得^201Tl SPECT再分布、再注射像及^18F-FDG PET显像的局部心肌摄取率（％ID）。结果 PET判定为存活心肌的48个节段中，45个节段（93．8％）^201Tl再注射像也判定为存活心肌。在^201Tl再分布像示放射性分布严重低下的24个节段，^201Tl再注射像与PET显像判定存活心肌的一致率为87．5％，其中37．5％为存活心肌节段，50％为地存活心肌节段。2种显像方法的％ID无明显差异，且呈显著正相关（r=0.722)。结论 再注射^201Tl心肌显像判断存活心肌的准确性与PET心肌显像相似，有较大的临床应用价值。     

低剂量增强多层螺旋CT对陈旧性心肌梗死心肌活性的评价

目的 前瞻性评价低剂量增强多层螺旋CT(MSCT)显示陈旧性心肌梗死心肌活性的可行性和可靠性,并与MR心肌灌注和心肌活性成像进行对照研究.方法 对32例临床明确诊断为陈旧性心肌梗死的患者行前瞻性首过和延迟增强64层MSCT及MR心肌灌注成像,在短轴面上将左心室分为16个心肌段进行分析,所有患者的MSCT和MR影像资料被双盲分析,确定早期心肌灌注缺损区和晚期延迟增强区的大小及范围.采用一致性检验的Kappa检验,评价两种方法对显示心肌活性的一致性.结果 32例患者,首过灌注期MSCT提示灌注缺损为41个节段,无灌注缺损为471个节段;首过灌沣期MRI提示灌注缺损为47个节段,无灌注缺损为465个节段,两种方法一致性Kappa值为0.650,符合率为94.5%(484/512).延迟期MSCT显示延迟增强为135个节段,其中非透壁性梗死为50个节段,透壁性梗死为85个节段,未出现延迟增强为377个节段;延迟期MRI显示延迟增强为120个节段,其中非透壁性梗死为56个节段,透壁性梗死为64个节段,未出现延迟增强为392个节段,两种方法一致性Kappa值为0.609,符合率为80.7%(413/512).结论 低剂量增强螺旋MSCT与MRI对心肌活性的评价有较好的相关性,MSCT对陈旧性心肌梗死的存活心肌和非存活心肌的检测是呵行和可靠的,减少不必要的X线辐射剂量是该研究的重要方面.     

坏死亲和性对比剂MRI显示梗死心肌及病理对照研究

目的：通过冠状动脉注射坏死组织亲和性非卟啉类顺磁性对比剂（ECⅢ-60）后MR延时影像与病理对照的方法明确其强化区与梗死心肌的关系，并与静脉注射非特异性对比剂钆喷替酸葡甲胺（Gd－DTPA）比较，以期为MRI准确评价心肌活性提供可靠的病理依据。方法：经导管采用闭胸法成功建立8只猪的急性心肌梗死再灌注模型。经静脉以0．2mmol／kg快速团注Gd-DTPA后行心电激发的心脏MR短轴面T1WI，延时扫描至局部Gd-DTPA完全消失。然后再以0．0025mmol／kg经冠状动脉导管缓慢注入ECⅢ-60后短轴面T1WI，延时成像至5h。比较分析ECⅢ-60增强MRI延时强化区和金标准病理所示梗死区的关系；并和Gd－DTPA增强MRI的对比增强效果（CR）与范围（RIS）进行比较。结果：ECⅢ-60增强MRI可见梗死区的信号较正常对照区明显升高（CR〉3．0）并持续超过5h，其强化区相对面积[占同层面左室面积的百分率为（11．84±3．63）％]与TTC染色心肌梗死面积[（11．78±3．64）％]一致（t=2．251，P〉0．05），两者呈正相关，其决定系数为r=0．999。Gd-DTPA也能产生CR〉3．0的强化效果，但对梗死区的对比度在2h内逐步消失。结论：坏死亲和性对比剂增强MRI能持续准确地反映心肌梗死，能成为冠状动脉介入术后心肌活力评估的有潜在价值的方法。     

Magnetic resonance imaging in determination of myocardial ischemia and viability: comparison with positron emission tomography and single-photon emission computed tomography in a porcine model

Background: In patients with chronic left ventricular dysfunction, the size of the viable cardiac muscle is correlated with the prognosis and the outcome of myocardial revascularization.

Purpose: To evaluate the diagnostic value of various imaging techniques in determination of myocardial ischemia and viability.

Material and Methods: A chronic myocardial ischemia animal model was established, in which 10 pigs underwent magnetic resonance imaging (MRI), positron emission tomography (PET), and single-photon emission computed tomography (²⁰¹Tl SPECT) before and 1-2 months after modeling. The size of myocardial ischemia and necrosis was judged, and the imaging manifestations were compared with pathologic findings.

Results: Seven of the 10 animals completed all examinations uneventfully. On dobutamine-stressed cine MRI, 10 (8.93%) segments were found to be akinetic. Perfusion was abnormal in 34 (30.35%) segments. Delayed hyperenhancement was observed in 12 (10.71%) segments. PET detected myocardial necrosis in 17 (15.18%) segments, and SPECT detected myocardial necrosis in nine (8.04%) segments. Histological examination with triphenyltetrazolium chloride (TTC) showed pale necrosis in 14 (12.50%) segments. The number of necrotic segments detected by PET was significantly greater than that by contrast-enhanced MRI (χ² = 5, P = 0.0253, kappa = 0.8028) and cine MRI (χ² = 7, P = 0.0082, kappa = 0.7079). It was also greater than that by TTC (χ² = 3, P = 0.0833, kappa = 0.8879), although the difference was statistically insignificant. The number of necrotic segments detected by SPECT was significantly smaller than that by TTC (χ² = 5, P = 0.0253, kappa = 0.7590), as was the number of necrotic segments detected by cine MRI (χ² = 4, P = 0.0455, kappa = 0.8100). There was no statistically significant difference in the detection of necrotic segments between contrast-enhanced MRI and TTC (χ² = 2, P = 0.1573, kappa = 0.9130).

Conclusion: Cardiac MRI can determine viable myocardium and clearly delineate the location and degree of myocardial necrosis. PET slightly overestimates the extent of the necrotic myocardium and is unable to distinguish transmural necrosis from subendocardial necrosis.     

Low-dose dobutamine electrocardiograph-gated myocardial SPECT for identifying viable myocardium: comparison with dobutamine stress echocardiography and PET.

The identification of severely dysfunctional but viable myocardium is of particular importance for the selection of patients with depressed left ventricular function who will benefit from coronary revascularization. Assessment of inotropic reserve with dobutamine has recently been used for this purpose. This study compared the accuracy of low-dose dobutamine stress gated myocardial SPECT (DS SPECT) with the accuracy of dobutamine stress echocardiography (DSE) and resting perfusion SPECT for the identification of viable myocardium in patients with previous myocardial infarction. METHODS: Resting and low-dose dobutamine (7.5 microg/kg/min) gated (99m)Tc-tetrofosmin SPECT and echocardiography and resting (18)F-FDG PET were prospectively studied in 23 patients with previous myocardial infarction and severely depressed regional function. Twenty-one of them were successfully studied with each technique. The left ventricular wall was divided into 14 segments to assess wall motion using a 5-point scale. PET viability was defined as FDG uptake >/= 50% of the maximum uptake in a region with normal wall motion. For DS SPECT and DSE studies, viable myocardium was defined as hypokinetic areas with > or = 1 point improvement in wall motion. For resting perfusion SPECT, viable myocardium was defined as hypokinetic areas with a relative uptake > or = 50% of the maximum uptake. RESULTS: Of a total of 294 segments, 55 had severe resting dyskinesis. Thirty-four segments were identified as viable on FDG PET, and 21 segments were identified as nonviable. Eleven segments were inadequately visualized with DSE, including 5 segments in the apex. Sensitivities (78% vs. 76%) and specificities (94% vs. 100%) were similar for DSE and DS SPECT, with a concordance of 86% (kappa = 0.72). DS SPECT and perfusion SPECT did not significantly differ with respect to sensitivities (76% vs. 85%, respectively). However, specificity was significantly higher for DS SPECT than for perfusion SPECT (100% vs. 52%, respectively, P < 0.05). CONCLUSION: This study indicated that DS SPECT correlates well with DSE in the assessment of viability. In addition, gated SPECT can evaluate regional wall motion, even in areas inadequately assessed by echocardiography. DS SPECT may also provide additional information for identifying viable myocardium, which is often overestimated by routine perfusion scans.     

Comparison of contrast-enhanced MRI with (18)F-FDG PET/201Tl SPECT in dysfunctional myocardium: relation to early functional outcome after surgical revascularization in chronic ischemic heart disease.

Revascularization of viable myocardial segments has been shown to improve left ventricular (LV) function and long-term prognosis; however, the surgical risk is comparatively higher in patients with a low ejection fraction (EF). We compared contrast-enhanced MRI with (18)F-FDG PET/(201)Tl SPECT for myocardial viability and prediction of early functional outcome in patients with chronic coronary artery disease (CAD). METHODS: Forty-one patients with chronic CAD and LV dysfunction (mean age +/- SD, 66 +/- 10 y; 32 men; mean EF +/- SD, 38% +/- 13%) referred for (18)F-FDG PET, (201)Tl-SPECT and MRI within 2 wk were included. Twenty-nine subjects underwent coronary artery bypass grafting (CABG), and LV function was reassessed by MRI before discharge (17 +/- 7 d after surgery). Two were excluded from outcome analysis (1 death due to sepsis; 1 perioperative myocardial infarction). The extent of viable myocardium by (18)F-FDG PET/(201)Tl SPECT was defined by the metabolism-perfusion mismatch or ischemia, in comparison with the extent of delayed enhancement (DE) on MRI in a 17-segment model. Segmental functional recovery was defined as improvement in the wall motion score of > or =1 on a 4-point scale. EF and LV volume change were used as global functional outcome. RESULTS: Three hundred ninety-four dysfunctional segments were compared, and the extent of DE on MRI correlated negatively with the viability on (18)F-FDG PET. Of 252 dysfunctional segments that were successfully revascularized, the sensitivity, specificity, positive predictive value, and negative predictive value of PET/SPECT were 60.2%, 98.7%, 76.6%, and 96.7% and of MRI were 92.2%, 44.9%, 72.4%, and 78.6% using the cutoff value of 50% DE on MRI, without significant differences in overall accuracies. In 18 subjects who underwent isolated CABG, improvement of EF (> or =5%) and reverse LV remodeling (> or =10% LV size reduction) was best predicted by the no DE on MRI, and patients with substantial nonviable myocardium on (18)F-FDG/SPECT predicted a poor early functional outcome (all P < 0.001). CONCLUSION: Accurate prediction of early functional outcome by PET/SPECT and contrast-enhanced MRI is possible.     

Attenuation-corrected 99mTc-MIBI SPECT in overweight patients with chronic ischaemic dysfunction: a comparison to NH3 PET and implications for the diagnosis of myocardial viability

OBJECTIVE: We determined the value of attenuation correction (AC) of myocardial perfusion estimation with (99m)Tc-MIBI SPECT in overweight patients by comparison of uncorrected (filtered back-projection (FBP) and corrected (an iterative algorithm with a measured attenuation coefficients map (FL-AC)) (99m)Tc-MIBI relative uptake to perfusion data obtained in the same patients with NH3 PET. In addition, the impact of attenuation correction for the assessment of myocardial viability with (99m)Tc-MIBI SPECT was determined using FDG PET as the reference method. METHODS: Thirty consecutive overweight patients (BMI=28+/-4) with left ventricular dysfunction underwent a resting (99m)Tc-MIBI SPECT and a PET study (NH3 and FDG). (99m)Tc-MIBI SPECT scans were reconstructed without attenuation correction (FBP) and with attenuation correction (FL-AC). The left ventricle was divided into 16 segments, in which the relative uptake was quantified using circumferential profiles. A relative uptake > or = 60% was considered consistent with viable myocardium for FDG and MIBI. RESULTS: The absolute difference between (99m)Tc-MIBI SPECT and NH3 PET uptakes was less pronounced in the inferior (12+/-10% vs. 17+/-12%, P<0.001), anteroseptal (12+/-11% vs. 16+/-12%, P=0.009) and septal (15+/-12% vs. 18+/-14%, P=0.003) regions (FL-AC vs. FBP, respectively). The sensitivity of MIBI for diagnosing myocardial viability increased from 83 to 100% (P=0.034), without loss in specificity. CONCLUSION: Attenuation correction improves myocardial perfusion estimation by (99m)Tc-MIBI SPECT in the inferior, anteroseptal and septal regions and increases its sensitivity for the diagnosis of myocardial viability.     

Electromechanical properties of perfusion/metabolism mismatch: comparison of nonfluoroscopic electroanatomic mapping with 18F-FDG PET.

The aim of this study was to compare nonfluoroscopic electroanatomic mapping (NOGA), SPECT perfusion imaging, and PET metabolic imaging for assessment of myocardial viability. In particular, we sought to elucidate differences of electromechanical properties between the perfusion/metabolism mismatch as an indicator of a potentially reversible ischemic injury and the perfusion/metabolism match indicating irreversibly damaged myocardial tissue. METHODS: Twenty-one patients with coronary artery disease underwent NOGA mapping of endocardial unipolar voltage, cardiac 18F-FDG PET of glucose utilization, and resting 201Tl SPECT of myocardial perfusion. RESULTS: Electrical activity was 10.8 +/- 4.6 mV (mean +/- SD) in normal myocardium and was unchanged in hypoperfused segments with maintained glucose metabolism (perfusion/metabolism mismatch), 9.3 +/- 3.4 mV (P = not significant). In contrast, hypoperfused segments with a perfusion/metabolism match and nonviable segments showed significantly lower voltage (6.9 +/- 3.1 mV, P < 0.0001 and 4.1 +/- 1.1 mV, P < 0.0001 vs. normal). In hypoperfused segments, metabolic activity was more closely related to endocardial voltage than was myocardial perfusion (201Tl vs. voltage: r = 0.38, SEE = 3.2, P < 0.001; 18F-FDG PET vs. voltage: r = 0.6, SEE = 2.8, P < 0.0001). CONCLUSION: In hypoperfused myocardium, electrical activity by NOGA mapping is more closely related to PET metabolic activity than to SPECT myocardial perfusion. As NOGA mapping does not differentiate hypoperfused myocardium with enhanced glucose utilization from normal myocardium, results from NOGA mapping need to be correlated with results from perfusion imaging to identify hypoperfused, yet viable, myocardium and to stratify patients for revascularization procedures.     

Noninvasive assessment of myocardial viability in a small animal model: comparison of MRI, SPECT, and PET.

Acute myocardial infarction (AMI) research relies increasingly on small animal models and noninvasive imaging methods such as MRI, single-photon emission computed tomography (SPECT), and positron emission tomography (PET). However, a direct comparison among these techniques for characterization of perfusion, viability, and infarct size is lacking. Rats were studied within 18-24 hr post AMI by MRI (4.7 T) and subsequently (40-48 hr post AMI) by SPECT ((99)Tc-MIBI) and micro-PET ((18)FDG). A necrosis-specific MRI contrast agent was used to detect AMI, and a fast low angle shot (FLASH) sequence was used to acquire late enhancement and functional images contemporaneously. Infarcted regions showed late enhancement, whereas corresponding radionuclide images had reduced tracer uptake. MRI most accurately depicted AMI, showing the closest correlation and agreement with triphenyl tetrazolium chloride (TTC), followed by SPECT and PET. In some animals a mismatch of reduced uptake in normal myocardium and relatively increased (18)FDG uptake in the infarct border zone precluded conventional quantitative analysis. We performed the first quantitative comparison of MRI, PET, and SPECT for reperfused AMI imaging in a small animal model. MRI was superior to the other modalities, due to its greater spatial resolution and ability to detect necrotic myocardium directly. The observed (18)FDG mismatch likely represents variable metabolic conditions between stunned myocardium in the infarct border zone and normal myocardium and supports the use of a standardized glucose load or glucose clamp technique for PET imaging of reperfused AMI in small animals.     

Comparison of contrast-enhanced MRI with iodine-123 BMIPP for detection of myocardial damage in hypertrophic cardiomyopathy

OBJECTIVE: The purpose of this study was to compare contrast-enhanced MRI with dual-radionuclide SPECT for the detection of myocardial damage associated with hypertrophic cardiomyopathy. SUBJECTS AND METHODS: Twenty-three patients with hypertrophic cardiomyopathy were examined. Delayed hyperenhancement of the damaged myocardium was observed using contrast-enhanced MRI, and regional wall thickness and left ventricular ejection fraction were measured using cine balanced steady-state free precession MRI. Dual-radionuclide SPECT using technetium-99m sestamibi and iodine-123 15-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (BMIPP) was performed at rest. In the abnormal myocardial segments, agreement between the contrast-enhanced MRI and 123I BMIPP SPECT was assessed. The relationships between the regional and global cardiac abnormalities and the delayed hyperenhancement on MRI and decreased uptake of 123I BMIPP were also evaluated. RESULTS: In 368 left ventricular segments, 57 segments showed delayed hyperenhancement on MRI, 43 segments showed decreased uptake of 123I BMIPP, and seven showed decreased uptake of (99m)Tc sestamibi. The delayed hyperenhancement and decreased uptake of 123I BMIPP were frequently observed in the interventricular septal wall (p < 0.0001); however, the agreement between the methods in detecting myocardial abnormalities was fair (kappa = 0.38). The abnormal septal walls were significantly thicker than those without apparent abnormalities (p = 0.031). There was an inverse correlation between the number of enhancing segments and the ejection fraction (r = -0.53). CONCLUSION: In hypertrophic cardiomyopathy, contrast-enhanced MRI was valuable for the detection of extensive myocardial damage.     

Tc-99m tetrofosmin tomography after nitrate administration in patients with ischemic left ventricular dysfunction: Relation to metabolic imaging by PET

BACKGROUND: In patients with ischemic left ventricular (LV) dysfunction, myocardial perfusion imaging after nitrate administration may improve the identification of dysfunctional but viable myocardium. This study was designed to assess the relationship between tetrofosmin uptake after nitrate administration and metabolic activity as assessed by positron emission tomography (PET) in patients with ischemic LV dysfunction. METHODS AND RESULTS: Thirty-six patients with chronic myocardial infarction and LV dysfunction (ejection fraction, 35% +/- 6%) underwent resting technetium 99m tetrofosmin single photon emission computed tomography (SPECT) imaging under control conditions (baseline) and after sublingual administration of 10 mg isosorbide dinitrate. Within 1 week, all patients underwent metabolic PET imaging with fluorine 18-fluorodeoxyglucose. Tetrofosmin uptake and metabolic activity were measured in 13 segments/patient. Regional LV function was assessed in corresponding segments by echocardiography. On baseline tetrofosmin imaging, 53 (40%) of the 131 akinetic or dyskinetic segments had reduced (<55% of peak activity) tracer uptake. Of these segments, 14 (26%) showed enhanced tetrofosmin uptake after nitrate administration (>/=10% vs baseline) and the remaining 38 (74%) did not change. The sensitivity and specificity of baseline tetrofosmin SPECT for detecting preserved metabolic activity were 69% and 86%, respectively. After nitrate administration, the sensitivity was higher (81%, P <.05 vs baseline) whereas the specificity was not different (86%, P = not significant). Concordance between tetrofosmin SPECT and PET in differentiating viable and necrotic myocardium was observed in 94 (72%) of the 131 akinetic or dyskinetic segments at baseline (kappa = 0.35) and in 108 segments (82%) after nitrate administration (kappa = 0.53). CONCLUSIONS: After nitrate administration, tetrofosmin uptake in dysfunctional segments correlated with metabolic activity as assessed by fluorodeoxyglucose PET imaging better than baseline. Thus tetrofosmin SPECT after nitrate administration may improve the identification of ischemic but still viable myocardium in patients with chronic ischemic LV dysfunction.