Enhanced detection of ischemic but viable myocardium by QT interval dispersion on treadmill exercise electrocardiograms of patients with healed anterior wall myocardial infarcts

BACKGROUND: The presence of ischemic but viable myocardium in infarcted areas is an important indication for coronary revascularization, but is often difficult to detect with the use of treadmill exercise electrocardiography (ECG). HYPOTHESIS: QT interval dispersion (QTd) is a sensitive method for detecting myocardial ischemia and may improve the accuracy of treadmill exercise ECG testing for detecting ischemic but viable myocardium in infarcted areas. METHODS: Forty-five patients with Q-wave anterior wall myocardial infarctions who underwent treadmill exercise ECG, exercise reinjection thallium-201 (201Tl) scintigraphy, radionuclide angiocardiography, and coronary angiography 1 month after infarction were enrolled in this study. The presence of viable myocardium in the infarct area was determined by exercise reinjection 201Tl scintigraphy. Patients who had no redistribution in the infarct area after reinjection were included in Group 1, and those with redistribution were included in Group 2. RESULTS: QTd immediately after exercise, and the difference between QTd before and immediately after exercise, were significantly greater in Group 2 than in Group 1. The sensitivity, specificity, and accuracy of conventional ST-segment depression criteria for detecting viable myocardium in the infarct area were 48, 64, and 56%, respectively. The measurement of QTd immediately after exercise (abnormal: > or = 70 ms; normal: < 70 ms) improved the sensitivity, specificity, and accuracy to 78, 82, and 80%, respectively. CONCLUSIONS: This novel diagnostic method using QTd-based criteria significantly improves the clinical usefulness of treadmill exercise ECG testing for detecting ischemic but viable myocardium in infarct areas in patients with healed Q-wave anterior wall myocardial infarctions.     

多普勒组织成像检测冠心病患者梗死心肌的研究

目的　测算比较正常室壁心肌和梗死心肌的运动速度 ,评估多普勒组织成像 (DTI)对冠心病梗死心肌的诊断价值。方法　心肌梗死患者 4 6例 ,分成前壁梗死组 2 9例和下壁梗死组 17例 ,健康人 4 8例作对照 ;在心尖左室长轴切面 (alax)上测得室壁节段厚度 ;于心尖四腔心切面(ap4cv)、心尖二腔心切面 (ap2cv)、胸骨旁左室长轴切面(pslax)和alax应用DTI ,按左室壁 16节段 ,测量各室壁节段心肌运动曲线的速度指标 :收缩期峰值运动速度 (Sm) ;舒张早期峰值运动速度 (Em) :收缩期峰值速度梯度 (PVGs) :舒张早期峰值速度梯度 (PVGe) :收缩期跨壁速度梯度 (MVGs) :舒张早期跨壁速度梯度 (MVGe) ,并分别作组间和组内比较。结果　 (1)心梗患者内膜下心肌绝大多数节段性的室壁运动速度降低 ,与对照组存在显著差异 (P <0 0 1或 <0 0 5 ) :(2 )前壁梗死患者前间隔峰值速度梯度 (PVG)与跨壁速度梯度、(MVG)降低 ,中间段明显降低 (P <0 0 1或 <0 0 5 ) ,后壁基底段的MVGs 显著升高 (P <0 0 5 ) ;前间隔PVG、MVG明显小于后壁 (P <0 0或 <0 0 5 ) ;(3)下壁梗死患者各室壁节段舒张早期峰值速度梯度 (PVGe)除后壁基底段外均降低 ;同水平节段内膜下心肌峰值运动速度 (Sm、Em)趋于一致。结论　梗死心肌运动速度明显低于正常     

Detection of viable myocardium by transvenous myocardial contrast echocardiography using harmonic power Doppler: canine model of acute coronary occlusion and reperfusion

STUDY OBJECTIVE: To assess whether myocardial contrast echocardiography (MCE) using harmonic power Doppler (HPD) in conjunction with the transvenous contrast agent SHU 563A would be useful in detecting stunned but viable myocardium. DESIGN: Acute coronary occlusion (2 to 3 h) followed by 1 h of reperfusion was created in 10 dogs in an open-chest model. Measurements and results: Continuous harmonic B-mode for wall motion analysis and ECG triggered HPD for assessment of myocardial perfusion was employed during coronary occlusion and after reperfusion. Postmortem 2,3,5-triphenyltetrazolium chloride (TTC) staining was performed to verify infarction. Extent of wall motion abnormality (WMA), perfusion defect size, and anatomic infarct size (myocardial infarction [MI]) were analyzed in a 5-segment model. All 10 dogs showed WMA in 23 of 50 segments during coronary occlusion. In eight dogs, HPD detected perfusion defects in 18 of 50 segments. The concordance rate between WMA and perfusion defect was 86%. Mean linearized power (MLP) in segments with WMA was significantly lower compared to normal segments (60.7 +/- 38.9 vs 110.5 +/- 108.8, p < 0.05). After reperfusion, the extent of WMA was larger than the area of perfusion defect (percentage of left ventricular slice area): 30 +/- 13% vs 9 +/- 8%, p < 0.01. Eventual infarct size was 6 +/- 7%. WMAs were seen in 18 of 50 segments. TTC confirmed MI in 7 of 18 segments. MLP in segments with WMA but no MI was significantly higher compared to segments with WMA and MI (84.5 +/- 67.3 vs 13.2 +/- 9.6, p < 0.01). Thus, the extent of WMA after reperfusion was greater than the size of perfusion defect and eventual MI, indicating the presence of stunned but viable myocardium. CONCLUSION: MCE using HPD and the contrast agent SHU 563A can demonstrate the efficacy of reperfusion, identify necrotic regions, and aid in the recognition of stunned but viable myocardium. This approach could be useful clinically in patients with acute MI undergoing reperfusion therapy.     

Early quantification of experimental myocardial infarction with technetium-99m glucoheptonate: scintigraphic and anatomic studies.

Recent advances in understanding of the pathophysiology of myocardial necrosis indicate the need for a noninvasive method that will allow detection and quantification of infarcts in the first few hours after the onset of infarction. Myocardial infarct scintigraphy using technetium-99m glucoheptonate is capable of detecting infarction in dogs and man within 4 to 6 hours of onset. Studies were performed in 45 dogs with acute myocardial infarction: 28 with with an anterior infarct, 5 with an inferior infarct, 6 with an anterior infarct studied after infusion of mannitol and 6 with ligation of the left anterior descending coronary coronary artery and reperfusion of the ischemic area. The dogs were given 20 m Ci of technetium-99m glucoheptonate 1 hour after coronary occlusion, subjected to imaging 5 to 9 hours later and then killed. The experiments revealed that (1) scintigraphic infarct size correlated with infarct weight for anterior (r = 0.85) and inferior (r = 0.88) infarcts; (2) technetium-99m glucoheptonate also concentrated in a rim of myocardium around the infarct that probably represented the ischemic zone; and (3) technetium-99m glucoheptonate uptake by infarcted myocardium could be greatly increased with mannitol and reperfusion.     

直接经皮冠状动脉腔内成形术中冠状动脉内心电图判定存活心肌的价值

目的 应用99mTc-MIBI心肌断层显像(SPECT)评价冠状动脉内心电图(IC-ECG)判定急性心肌梗死(AMI)存活心肌的价值。方法 56例急性前壁心肌梗死患者，接受了直接经皮冠状动脉腔内成形术(PTCA)，梗死相关动脉前降支(LAD)达到TIMI3级血流后IC-ECG自PTCA导引导丝尾端引出作为参照基线，在进一步球囊扩张时IC-ECG ST段再次抬高大于0．2mV时认为具有判定梗死相关部位有存活心肌的意义。测定并比较急性期及恢复期左心室梗死相关区域节段性缩短率(LVSS)与射血分数(LVEF)，梗死区域存活心肌通过恢复早期静息与硝酸甘油介入两次99mTc-MIBI SPECT量化判定。结果 4l例病人(A组)行直接PTCA时IC-ECG ST段明显抬高，15例(B组)未出现相应变化，A组INSS、INEF。在恢复期均显著大于B组，两次99mTc-MIBISPECT显示，硝酸甘油介入后显像A组梗死缺损区面积明显减少，核素放射性计数百分比亦明显增加，B组则无明显改变，说明A组梗死区域有较多存活心肌，与IC-ECT ST段抬高意义一致。结论 直接PTCA过程中可通过球囊扩张时IC-ECG ST段抬高变化初步判定梗死相关区域的心肌活性。     

小剂量多巴酚丁胺超声心动图试验和双核素心肌显像检测急性心肌梗死后患者存活心肌比较

目的比较小剂量多巴酚丁胺超声心动图试验（LDDE）和^99mTc-甲氧基异丁腈（MIBI）／^18F-脱氧葡萄糖（FDG）双核素同时采集法（DISA）单光子发射型断层显像（SPECT）对急性心肌梗死早期存活心肌检出的准确性。方法对44例急性心肌梗死患者于发病后5～10天内行LDDE和DISA—SPECT,所有患者在LDDE和DISA检查后接受经皮冠状动脉介入术。两种方法均采用16节段半定量法分析图像。心肌梗死后3个月随访二维超声,以局部室壁运动改善作为心肌存活标准,比较两种方法检测存活心肌的敏感性和特异性。结果LDDE检出存活心肌的敏感性、特异性、诊断准确性、阳性预测值和阴性预测值分别为77％、82％、79％、82％和77％。DISA检出存活心肌的敏感性、特异性、诊断准确性、阳性预测值和阴性预测值分别为85％、62％、74％、71％和79％。LDDE和DISA两者对运动异常节段检出存活心肌的一致性为70％。对于运动减低节段,LDDE和DISA对存活心肌检出率差异无统计学意义（74．1％比77．6％,P〉0．05）;对于无运动节段,LDDE对存活心肌检出率低于DISA（29％比53％,P〈0．01）。结论对急性心肌梗死后的患者,DISA检出存活心肌的敏感性高于LDDE,而特异性低于LDDE,联合应用起互补作用,提高检测存活心肌的能力。     

Hyperaemic microvascular resistance is not increased in viable myocardium after chronic myocardial infarction.

AIMS: The present study compared microvascular resistance (MR) of viable myocardium in infarct areas with those in reference areas in patients with chronic myocardial infarction (MI). METHODS AND RESULTS: In 27 patients, MR (ratio distal coronary pressure and flow) of reference and viable infarct areas was calculated at baseline and during hyperaemia. H2 15O positron emission tomography (PET) was used to provide myocardial blood flow measurements. In infarct regions, H2 15O PET solely measures flow in viable myocardium, excluding flow in scar tissue. Distal coronary pressure was measured with a pressure wire in the infarct-related and reference artery. The average time between PET study and infarction was 3.3+/-4.4 years. Mean hyperaemic distal coronary pressure was significantly lower in the infarct-related artery. MR varied considerably between patients and was significantly higher in infarct areas at baseline (135+/-38 vs. 118+/-29 mmHg mL min/mL; P<0.05), but not during hyperaemia (39+/-18 vs. 35+/-11 mmHg mL min/mL). The correlation between MR in infarct and reference areas was significant. CONCLUSION: To determine MR, distal coronary pressure measurements should be used. Hyperaemic MR in viable myocardium within the infarcted area is not higher when compared with the reference area. This supports the application of the established fractional flow reserve cut-off value in the setting of chronic MI.     

硝酸甘油介入~(99m)锝─甲氧基异丁基异腈心肌灌注显像识别存活心肌及对急性心肌梗塞血运重建术疗效评价

目的：探讨硝酸甘油（ＮＴＧ）介入９９ｍ锝—甲氧基异丁基异腈（９９ｍＴＣ－ＭＩＢＩ）心肌灌注显像评价存活心肌、指导经皮冠状动脉腔内成形术（ＰＴＣＡ）,把握适应证及判定ＰＴＣＡ疗效的应用价值。 方法：对２３例行ＰＴＣＡ的急性心肌梗塞患者进行术前静息９９ｍＴＣ－ＭＩＢＩ心肌灌注显像、ＮＴＧ介入９９ｍＴＣ－ＭＩＢＩ心肌灌注显像和术后１周、２个月静息９９ｍＴＣ－ＭＩＢＩ心肌灌注显像,采用４点积分法半定量分析９９ｍＴＣ－ＭＩＢＩ的摄取。根据放射性异常程度不同将受累心肌节段分为心肌存活节段,部分心肌存活节段、心肌无存活节段。 结果：ＮＴＧ介入９９ｍＴｃ－ＭＩＢＩ心肌灌注显像评价存活心肌的阳性预测值、阴性预测值和准确度,它们分别为８５．０％、８８．５％和８４．９％。ＰＴＣＡ后心肌存活节段和部分心肌存活节段放射性异常积分明显降低,心肌无存活节段未见显著变化。 结论：ＮＴＧ介入９９ｍＴｃ－ＭＩＢＩ心肌灌注显像能显著提高存活心肌的检出率,对急性心肌梗塞血运重建术的疗效判定及指导临床适应证的选择具有较高的应用价值。     

Assessment of left ventricular wall thickness in healed myocardial infarction by magnetic resonance imaging

The ability of magnetic resonance imaging (MRI) to detect and localize healed myocardial infarction (MI) was assessed. Seventeen consecutive patients with healed MI assessed by biplane contrast ventriculography underwent MRI using oblique imaging planes. Seven normal subjects underwent MRI as controls. In each patient, ventriculography identified regional wall motion abnormalities. MRI, performed with a 0.15-Tesla resistive magnet and oblique imaging planes relating to the left ventricle, detected zones of regional wall thinning conforming to the wall motion abnormalities localized by ventriculography in 16 patients. In these patients, adjacent areas of intact myocardium were identified in areas shown by ventriculography to be normal. The left ventricular wall thickness at the site of MI was significantly less than adjacent noninfarcted myocardium (p less than 0.001) and normal hearts (p less than 10(-6)). The ratio of the thickness of the infarct to adjacent normal wall averaged 0.40 (range 0.22 to 0.62). MRI could differentiate healed MI from adjacent noninfarcted myocardium and normal hearts.     

Intracoronary electrocardiogram for early detection of myocardial viability during coronary angioplasty in acute myocardial infarction.

PURPOSE: The clinical value of the intracoronary electrocardiogram (ECG) for detecting myocardial viability in acute myocardial infarction was evaluated by thallium-201 scintigraphy and left ventriculogram at the chronic stage. METHODS: Intracoronary ECGs, recorded from the tip of a guidewire during emergency coronary angioplasty, were obtained in 65 patients with reperfused anterior myocardial infarction. Further ST segment elevation of greater than 0.2 mV detected during the balloon inflation was taken as significant. The left ventricular segmental shortening was measured from left ventriculograms recorded at acute and chronic stages. The infarct area was defined as viable when a thallium uptake of more than 50% was detected on thallium-201 myocardial scintigraphy at the chronic stage. RESULTS: During emergency coronary angioplasty, significant ST segment elevation was noted in 45 patients (Group A); however, the ST segment was not significantly elevated in the other 20 patients (Group B). The infarct area of 42 patients in Group A and three patients in Group B was viable on scintigraphy. Improvement left ventricular wall motion of the infarct area was observed in 39 of the 42 patients in Group A and the three patients in Group B. Therefore, intracoronary ECG can predict reversible dysfunction with excellent sensitivity (92.9%) and specificity (73.9%). CONCLUSIONS: The myocardium within an infarct area can be regarded as viable when a further ST segment elevation occurs on intracoronary ECG during emergency coronary angioplasty. It is useful, therefore, to monitor the intracoronary ECG during coronary angioplasty balloon inflation to assess the myocardial viability of the infarct area.     

The value of myocardial contrast echocardiography compared with SPECT in detecting myocardial perfusion abnormalities in patients with anterior acute myocardial infarction

BACKGROUND: Microvasculature damage after myocardial infarction (MI), known as "no-reflow" phenomenon, may occur in some patients with acute MI in spite of invasive treatment and opened infarct-related coronary artery. There are several non-invasive and invasive methods used for the coronary flow assessment at the tissue level. AIM: To compare the value of intravenous contrast echocardiography (MCE) in detecting myocardial perfusion defects in patients with acute MI with (99m)Tc MIBI SPECT study. METHODS: Sixteen patients (11 males, 5 females, mean age 55.4+/-10.2 years) underwent primary coronary angioplasty or facilitated angioplasty (with reduced dose of a fibrinolytic drug and glycoprotein IIb/IIIa inhibitor) (PCI) for acute anterior MI. TIMI grade flow, TIMI Myocardial Perfusion Grade (TMPG), corrected TIMI frame count (cTFC), wall motion score index (WMSI) and segmental perfusion by myocardial contrast echocardiography (MCE) were estimated in real time before and immediately after PCI. MCE was repeated on the third day after PCI. All patients underwent (99m)Tc MIBI SPECT study (SPECT) while at rest on the third day after PCI. The area at risk was defined as the number of segments with no perfusion before angioplasty. Reflow was defined as an increase in contrast score in the same segments after angioplasty. RESULTS: Baseline MCE showed 95 segments with perfusion defects. Immediately after PCI, 77 segments were found with perfusion defect; in 10 patients improvement of myocardial perfusion was observed whereas in 6 patients perfusion defect remained unchanged. On the third day further improvement was observed in 8 patients. The number of segments with perfusion defect decreased to 53. SPECT detected perfusion defect in 54 segments. The agreement between MCE and SPECT for detecting perfusion abnormality was 98% (kappa 0.94). CONCLUSIONS: MCE is a safe technique for detecting myocardial perfusion in patients with acute MI. MCE proves that both primary and facilitated angioplasty improve myocardial perfusion in two thirds of patients with acute MI. Serial MCE allows identification of patients with both early and late improvement of myocardial perfusion. There is a very strong correlation between MCE and SPECT in the assessment of perfusion defects.     

Clinical validity of longitudinal pre-ejectional myocardial velocity for identifying the transmural extent of viable myocardium: early after reperfusion of an infarct-related coronary artery.

BACKGROUND: Positive longitudinal pre-ejectional velocity (+PEVL) was recently reported to be a reliable index of myocardial recovery early after successful revascularization in myocardial infarction (MI); that is, it recognizes the transmural extent of viable myocardium. The applicability of PEVL in the real-world clinical setting for identifying the transmural extent of viable myocardium in reperfused recent MI was assessed. METHODS AND RESULTS: Using tissue Doppler imaging, the resting basal and mid myocardial PEVLs were determined within 3 days after revascularization in 41 consecutive patients with recent MI. Infarct thickness was semi-quantified using delayed gadolinium-enhanced magnetic resonance imaging (MRI) at baseline and at 6-month follow up to differentiate transmural from nontransmural MI. The proportion of segments showing the presence of +PEVL was not significantly changed as infarct thickness increased (p=0.2), with 66.2% having +PEVL even in segments involving >75% transmural infarction. Moreover, +PEVL was found in a large fraction of segments with akinesia (70.4%). Specificity and negative predictive value of +PEVL for assessing infarct nontransmurality were disappointingly low (32.0% and 26.9%, respectively). All of these results were not altered when the 6-month follow-up MRI was done. CONCLUSIONS: +PEVL cannot be regarded as a reliable marker for predicting the transmural extent of viable myocardium in recent MI.     

Quantification of regional contractile function after infarction: strain analysis superior to wall thickening analysis in discriminating infarct from remote myocardium.

OBJECTIVES: Using two-dimensional wall thickening (WT) (expressed as percentage) and strain analysis, regional contractile myocardial function was quantified and compared in 13 control subjects and 13 patients with a first myocardial infarction (MI). The findings in the patient group were related to global ventricular function and infarct size. BACKGROUND: In patients with coronary artery disease, regions with dysfunctional myocardium cannot be differentiated easily from regions with normal function by planar WT analysis. Physiologic factors, in combination with limitations of conventional imaging techniques, affect the calculation of WT. Quantitative assessment of contractile function by magnetic resonance (MR) tissue tagging and strain analysis may be less affected by these factors. METHODS: Two-dimensional regional WT and strain were calculated in three short-axis MR cine and tagged images, respectively. Left ventricular volumes and ejection fraction (EF) were obtained from a series of contiguous short-axis cine images. RESULTS: In patients with infarct-related ventricles, WT and strain analysis both revealed reduced myocardial function, as compared with control subjects (p < 0.005 and p < 0.001, respectively). However, WT analysis yielded no significant regional differences in function between infarct-related and remote myocardium (p = 0.064), whereas strain analysis did (p < 0.005). For detecting dysfunctional myocardium of electrocardiographically and angiographically defined infarct areas, WT analysis had a sensitivity of 69% and a specificity of 92%, whereas strain analysis demonstrated a sensitivity of 92% and a specificity of 99%. The EF correlated with WT (r = 0.76, p < 0.005) and strain (r = 0.89, p < 0.001). CONCLUSIONS: Two-dimensional strain analysis is more accurate than planar WT analysis in discriminating dysfunctional from functional myocardium, and it provides a strong correlation between regional myocardial and global ventricular function.     

硝酸甘油介入99 mTc-MIBI心肌断层显像对存活心肌的评价

为评价硝酸甘油（NTG）介入99m锝-甲氧基异丁基异脯（99mTc－MIBI）心肌显像估测存活心肌的价值，对24例心肌梗死病人不同日行两种方案的99mTc－MIBI心肌显像：一种在静息状态进行，另一种在舌下含服NTG0．6mg后进行。8例经皮腔内冠状动脉成形术（PTCA）的病人术后2～4周随访了99mTc－MIBI静息显像。结果显示，99mTc－MIBI静息显像有118个心肌节段摄取正常，98个摄取异常（16个节段摄取减低，82个摄取严重减低），在98个摄取异常的节段中，NTG介入99mTc－MIBI显像有39个（39．80％）节段摄取增加。8例行PTCA的病人，NTG介入99mTC－MIBI显像证实为可逆性缺损的心肌节没有84．21％在PTCA后心肌灌注改善（存活心肌），而为NTG介入99mTc－MIBI显像证实为不可逆性缺损的心肌节段有88．24％在PTCA后心肌灌注无改善。NTG介入99mTc－MIBI显像预测存活心肌的准确性为86．11％。表明，NTG介入99mTc－MIBI心肌显像可提高缺血但存活心肌的检出率。     

Measurement of myocardial infarction fraction using single photon emission computed tomography

Although infarct size correlates generally with prognosis after acute myocardial infarction, an absolute measure of infarct size may have differing prognostic significance depending on absolute left ventricular mass. To test the hypothesis that single photon emission computed tomography can accurately measure myocardial infarct size as a percent of total left ventricular mass ("infarction fraction"), thallium-201 and technetium-99m pyrophosphate tomograms were acquired in 21 dogs 24 to 48 hours after fixed occlusion of the left anterior descending or circumflex coronary artery. Pathologic infarct weight was measured as the myocardial mass that showed no staining with triphenyltetrazolium chloride. Scintigraphic infarct mass by technetium-99m pyrophosphate was calculated from the total number of left ventricular volume elements (voxels) demonstrating technetium-99m pyrophosphate uptake X voxel dimension [( 0.476 cm]3) X specific gravity of myocardium (1.05 g/cm3). Scintigraphic left ventricular mass was calculated in a similar fashion using an overlay of the thallium-201 and technetium-99m pyrophosphate scans. The "infarction fraction" was calculated as: infarction fraction = infarct mass/left ventricular mass. There was good correlation between single photon emission computed tomography and pathologic measurements of infarct mass (technetium-99m pyrophosphate mass = 1.01 X pathologic infarct mass + 0.96; r = 0.98), left ventricular mass (single photon emission computed tomographic left ventricular mass = 0.60 X pathologic left ventricular mass + 37.4; r = 0.86) and "infarction fraction" (single photon emission computed tomographic infarction fraction = 1.09 X pathologic infarction fraction - 1.7; r = 0.94).(ABSTRACT TRUNCATED AT 250 WORDS)     

Scintigraphic assessment of sympathetic innervation after transmural versus nontransmural myocardial infarction

To evaluate the feasibility of detecting denervated myocardium in the infarcted canine heart, the distribution of sympathetic nerve endings using I-123 metaiodobenzylguanidine (MIBG) was compared with the distribution of perfusion using thallium-201, with the aid of color-coded computer functional map in 16 dogs. Twelve dogs underwent myocardial infarction by injection of vinyl latex into the left anterior descending coronary artery (transmural myocardial infarction, n = 6), or ligation of the left anterior descending coronary artery (nontransmural myocardial infarction, n = 6). Four dogs served as sham-operated controls. Image patterns were compared with tissue norepinephrine content and with histofluorescence microscopic findings in biopsy specimens. Hearts with transmural infarction showed zones of absent MIBG and thallium, indicating scar. Adjacent and distal regions showed reduced MIBG but normal thallium uptake, indicating viable but denervated myocardium. Denervation distal to infarction was confirmed by reduced norepinephrine content and absence of nerve fluorescence. Nontransmural myocardial infarction showed zones of wall thinning with decreased thallium uptake and a greater reduction or absence of MIBG localized to the region of the infarct, with minimal extension of denervation beyond the infarct. Norepinephrine content was significantly reduced in the infarct zone, and nerve fluorescence was absent. These findings suggest that 1) MIBG imaging can detect viable and perfused but denervated myocardium after infarction; and 2) as opposed to the distal denervation produced by transmural infarction, nontransmural infarction may lead to regional ischemic damage of sympathetic nerves, but may spare subepicardial nerve trunks that course through the region of infarction to provide a source of innervation to distal areas of myocardium.     

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.     

Quantification of myocardial infarction during coronary occlusion and myocardial salvage after reperfusion using cardiac imaging with technetium-99m hexakis 2-methoxyisobutyl isonitrile

Myocardial imaging with technetium-99m hexakis 2-methoxyisobutyl isonitrile was investigated as a means to assess myocardial infarct size during coronary occlusion and to quantify the extent of salvaged myocardium after coronary occlusion followed by reperfusion. Open chest dogs underwent either a permanent coronary artery occlusion (Group 1, n = 16) or a 2 h occlusion followed by reperfusion (Group 2, n = 15). Animals in both groups were killed 48 h after occlusion. During coronary occlusion, 23 of the 25 dogs that survived the coronary occlusions had abnormal myocardial scintigrams. The scintigraphic perfusion defect size correlated well with the pathologic infarct size (r = 0.85 and 0.95 by planar and tomographic imaging, respectively). The planar scintigraphic defect size, but not the tomographic defect size, overestimated the pathologic size. The planar scintigraphic defect size observed during coronary occlusion was markedly reduced 48 h after reperfusion (24.8 +/- 12.8% to 10.6 +/- 9.7% of the left ventricle, p less than 0.003). The uptake of technetium-99m hexakis 2-methoxyisobutyl isonitrile in the ischemic myocardium increased significantly 48 h after reperfusion (p less than 0.003) and correlated with the increase in regional myocardial blood flow, as assessed by radioactive microspheres (r = 0.83, p less than 0.01). Thus, myocardial imaging with technetium-99m hexakis 2-methoxyisobutyl isonitrile allows reliable demonstration of the presence of acute infarction, estimation of infarct size and quantification of the extent of salvaged myocardium after coronary reperfusion.     

再注射201铊心肌显像检测冬眠心肌的价值

目的探讨再注射２０１铊（Ｔｌ）心肌单光子发射计算机断层显像检测冬眠心肌的价值。方法对２２例冠心病心肌梗塞患者进行了运动再分布再注射２０１Ｔｌ心肌显像、心血池显像、冠状动脉（冠脉）造影及冠脉血运重建术，术后复查心血池及运动再分布２０１Ｔｌ心肌显像。结果１８个（４５％）在运动再分布影像上呈不可逆缺损节段在再注射影像上有再分布。再注射２０１Ｔｌ心肌显像预测冬眠心肌血运重建术后血流灌注与功能改善的阳性预测值为８８．９％和８３．３％，阴性预测值为７７．３％和８１８％，两者符合率为８４８％。术后患者运动耐量及左室射血分数改善。结论再注射２０１Ｔｌ心肌显像是检测冬眠心肌较可靠和实用的方法     

99mTc-MIBI心肌灌注断层显像在冠心病冠状动脉内支架置入术的应用

目的 :应用硝酸甘油 (NTG)介入 ,单光子发射计算机断层显像 (SPECT)检查估测冠状动脉 (冠脉 )介入治疗前后存活心肌的大小、范围。方法 :对 42例冠心病患者行静息及NTG介入SPECT心肌显像检查 ,应用阅片计分法、极坐标靶心图定量分析法估测心肌活力。以 19例接受经皮腔内冠脉成形术 (PTCA)加冠脉内支架置入 (Stent)术后静息显像结果为“金标准” ,评价NTG介入显像对心肌活力检测效果。结果 :静息显像及NTG介入SPECT显像其不规则感兴趣区内放射性稀疏缺损面积、放射性计数、放射性异常计分差异有显著性意义 (t分别为 7.5 43、4.6 0 8、6 .76 2 ,均 P <0 .0 0 1)。静息显像检测出存活心肌为 5 6 .3% ,NTG介入显像为 6 9.6 %。NTG介入显像估测存活心肌准确率为阅片计分法 80 .9% ,定量分析法 90 .5 %。结论 :NTG介入SPECT检查可提高存活心肌检出率 ,为冠脉内支架置入术治疗提供客观依据