药物负荷试验核素心肌断层显像识别存活心肌

目的探讨药物多巴酚丁胺、硝酸异山梨酯负荷试验核素锝[^99mTc]甲氧异丁异腈（technetium [^99mTc] methoxy isobutyl isonitrile,^99mTc-MIBI）心肌断层显像识别存活心肌的价值。方法对48例陈旧性心肌梗死伴左心室收缩功能受损患者进行静息心肌^99mTc-MIBI心肌断层显像和多巴酚丁胺、硝酸异山梨酯负荷试验^99mTc-MIBI心肌断层显像,用半定量的方法将^99mTc-MIBI摄取进行评分,区分存活心肌和非存活心肌。结果^99mTc-MIBI显像判定,经皮冠状动脉介入术前存活心肌节段有279个．非存活心肌节段235个;经多巴酚丁胺加硝酸异山梨酯负荷后,心肌显像改善：轻度稀疏节段9个、中度稀疏节段24个、严重稀疏或缺损节段10个,共计43个节段显像改善,评分减少1分以上,存活心肌节段313个,非存活心肌节段201个。两组差异有统计学意义（P〈0．05）。经皮冠状动脉介入术后6个月,随访多巴酚丁胺加硝酸异山梨酯负荷后,心肌显像改善的32个节段发现,静息^99mTc-MIBI显像改善,另有8个受损节段正常化。多巴酚丁胺加硝酸异山梨酯负荷后心肌显像无变化的389个节段在经皮冠状动脉介入术后346个节段无变化。多巴酚丁胺加硝酸异山梨酯负荷心肌显像检测存活心肌的阳性预测值93％,阴性预测值89％。结论多巴酚丁胺加硝酸异山梨酯负荷后心肌显像对存活心肌的识别能够提高存活心肌的检出率。其阳性预测值和阴性预测值较好。     

小剂量多巴酚丁胺负荷下超声斑点追踪技术与磁共振延迟增强显像技术评价陈旧性心肌梗死存活性研究

目的:比较磁共振延迟增强显像(DE-MRI)技术与小剂量多巴酚丁胺负荷斑点追踪超声(LDDS-STE)技术评价陈旧性心肌梗死患者存活心肌方面的敏感性和特异性。方法:选取30例本院住院陈旧性心肌梗死患者为研究对象。上述患者接受经皮冠状动脉介入治疗(PCI)术前进行心脏核磁共振检查及超声心动图检查,LDDS-STE方法分析静息和负荷条件下左心室室壁运动异常节段短轴径向应变(RS)及应变率(RSr),术后1,3,6个月复查超声心动图,观察室壁运动反常节段运动是否改善或恢复,以室壁运动分数改善作为判断存活心肌的金标准。结果:30例患者共获得510个左心室可分析节段,超声心动图判定室壁运动异常节段201个。与金标准比较,静息状态下左心室径向应变(RS_(rest))预测陈旧性心肌梗死患者存活心肌受试者工作特征(ROC)曲线下面积为0.636,敏感性为60.0%,特异性为60.5%;小剂量多巴酚丁胺负荷条件下左心室径向应变(RS_(LDDS))预测存活心肌ROC曲线下面积0.806,敏感性和特异性分别为79.1%及82.7%。静息状态下左心室径向应变率(RSr_(rest))预测陈旧性心肌梗死患者存活心肌敏感性为60.0%,特异性为60.5%,ROC曲线下面积0.646;小剂量多巴酚丁胺负荷条件下左心室径向应变率(RSr_(LDDS))预测存活心肌敏感性和特异性较静息状态下明显提高,分别为80.0%及83.7%,ROC曲线下面积0.808。DE-MRI技术预测存活心肌的敏感性和特异性分别为90.8%和87.1%,准确性89.5%,ROC曲线下面积为0.901。结论:DE-MRI与LDDS-STE方法均能准确识别梗死后存活心肌,但DE-MRI方法检测存活心肌的价值稍高于LDDS-STE,且准确率及重复性高,耗时短,为临床预测陈旧性心肌梗死患者PCI术的疗效及治疗策略的选择提供重要依据。     

低剂量多巴酚丁胺超声心动图和心电图ST段抬高预测血管重建术后存活心肌

目的采用低剂量多巴酚丁胺超声心动图(LDDE)和负荷心电图ST段抬高评价梗塞心肌节段于血管重建术前后的存活心肌.方法心肌梗死患者35例,于术前行低剂量多巴酚丁胺超声心动图和负荷心电图检查,术后一个月重复基础超声心动图检查.采用16节段和4分法评估左室功能,在术前和术后随访时有1个或1个以上节段室壁运动评分≥1为功能改善.结果 35例心肌梗死患者, 术后有18例室壁运动改善.有14例患者在行低剂量多巴酚丁胺试验时出现ST段抬高,其中术后有11例室壁运动改善, ST段抬高预测术后室壁运动改善的敏感性和特异性分别为61%和82%.同样,在术前LDDE心肌收缩力储备阳性的16例患者中,术后有14例功能改善,则LDDE对术后室壁运动改善的敏感性和特异性分别为77%和88%.结合术前负荷试验ST段抬高和LDDE心肌收缩力储备阳性,对术后室壁运动改善的敏感性和特异性分别为61%和94%.结论负荷试验ST段抬高和LDDE均是检测存活心肌安全、易行及有价值的方法.     

小剂量多巴酚丁胺超声心动图评价急性心肌梗死存活心肌的研究

目的　探讨梗死相关血管重建后存活心肌的功能恢复与左室重塑进程和左室功能恢复的关系。方法　将心肌梗死区异常室壁运动节段中存活心肌的节段数做为量化存活心肌的指标。筛选 4 8例初次急性心肌梗死患者 ,心肌梗死后 (2 0± 12 )天成功的接受梗死相关血管的介入治疗术 ,术前 1～ 3天接受静息超声心动图和小剂量多巴酚丁胺负荷超声心动图检查 ,术后 (5 4± 1 6 )个月复查静息超声心动图。依小剂量多巴酚丁胺超声心动图负荷试验检测出的梗死相关的异常室壁节段中存活心肌的节段数 ,将 4 8例患者分为 :Ⅰ组 ,大量存活心肌 (存活心肌节段≥ 6段 ) 11例 ,Ⅱ组 ,少量存活心肌 (2段≤存活心肌节段≤ 5段 ) 2 9例 ,Ⅲ组 ,无存活心肌 (存活心肌节段 <2段 ) 8例。分别测定术前和术后静息状态下的左室舒张末容积、左室收缩末容积、左室射血分数和左室室壁节段运动积分指数。结果　重建血管术后 (5 4± 1 6 )个月随访发现梗死相关动脉血管重建后 ,梗死相关血管的异常室壁运动有不同程度的改善 ,Ⅰ组的左室收缩末容量由 (6 3± 8)ml降至 (4 7± 10 )ml(P <0 0 1) ;室壁运动积分指数由 1 4± 0 2降至 1 1± 0 1(P <0 0 1) ,左室射血分数由 (4 6± 9) %增至 (5 7± 10 ) % (P<0 0 1)。Ⅱ组的左室收缩末容量 (7     

小剂量多巴酚丁胺负荷心脏超声评价冠心病介入治疗疗效的临床研究

目的　探讨用小剂量多巴酚丁胺负荷超声心动图(ＤＳＥ)试验评价冠脉成形术后血管再狭窄情况。方法　选择 32例陈旧性心肌梗塞病人 ,行小剂量多巴酚丁胺负荷超声心动图试验测定心肌催活性及射血分数(ＥＦ)小剂量ＤＳＥ试验 ,后均行ＰＴＣＡ和 /或ＳＴＥＮＴ术 ,于术后3～ 6月行小剂量多巴酚丁胺负荷超声心动图试验 ,测定目标血管区心肌催活性及射血分数 (ＥＦ)。结果　以心肌催活性≥ 110 %及射血分数增加≥ 15 %为阳性衡量标准联合评价的准确性为 86 7%。结论　小剂量ＤＳＥ试验可以评价急性冠脉综合症行ＰＴＣＡ和 /或ＳＴＥＮＴ术后血管…     

小剂量多巴酚丁胺负荷超声心动图联合心肌多层纵向应变评估陈旧性心肌梗死患者存活心肌的价值

目的 探讨小剂量多巴酚丁胺负荷超声心动图(LDDSE)联合心肌分层纵向应变(LS)评估陈旧性心肌梗死(PMI)患者存活心肌的价值.方法 纳入2018年1月至2019年1月就诊于浙江省台州医院的PMI患者38例,于经皮冠状动脉介入治疗前静息状态和小剂量多巴酚丁胺负荷状态下行超声心动图和心肌节段多层LS检查,并在术后1、3...     

关于负荷超声心动图与负荷核素心肌灌注显像

<正> 因为双嘧达莫(潘生丁)可引起局部的灌注差异,而多巴酚丁胺导致节段性左心室室壁运动减低,所以灌注显像(目前指核素或正电子发射体层成像扫描,当然将来是超声心动图)最适应于双嘧达莫试验,而超声心动图(或MRI)可选择性应用于多巴酚丁胺试验。由于缺血并不一定产生局部的灌注差异,故双嘧达莫心肌灌注显像对冠心病患者的探查比多巴酚丁胺的室壁运动显像具更高的敏感性。多巴酚丁胺导致的节段性左心室室壁运动受损依赖其所诱发的缺血,故其室壁运动显像对于已确诊冠心病且输出量依赖缺血的患者更具有预后价值。因此,多巴酚丁胺负荷超声心动图与双嘧达莫核素心肌灌注扫     

慢性冠状动脉狭窄犬静息和负荷时室壁运动异常与心内膜下心肌血流储备的关系

目的 评价静息和多巴酚丁胺负荷时室壁增厚百分率(%WT)与心内膜下心肌血流(MBF)储备的关系.方法 以安放缩窄器的方法建立11只慢性多支冠状动脉狭窄闭胸犬.术后7～10 d,在静息和不同剂量多巴酚丁胺作用下以二维超声测定%WT.同时,在静息和峰值多巴酚丁胺时,以放射性微球测定心内膜下MBF和MBF储备.结果 静息状态下,40个室壁运动异常(RWMA)心肌节段与42个非RWMA间的心内膜下MBF无明显差异.然而,RWMA的心内膜下MBF储备明显低于非RWMA,且静息状态%WT与心内膜下MBF储备密切相关.所有心肌节段在20 μg·kg-1·min-1以下剂量的多巴酚丁胺作用时,%WT随剂量增加而增加;当大于该剂量后,%WT的变化受心内膜下MBF储备的影响,当储备能力异常时,则出现多巴酚丁胺的"双向反应".结论 在慢性冠状动脉狭窄中,静息和负荷时RWMA与心内膜下MBF储备有关.     

大剂量多巴酚丁胺核磁共振与超声心动图负荷试验在无创伤性诊断缺血性室壁运动异常中的对照研究

应用多巴酚丁胺超声心动图负荷试验被公认是分析室壁运动异常,确定心肌缺血的方法,相同的试验同样适用于超高速核磁共振成像技术。选择208例可疑冠心病进行研究,男147例,女61例,采用谐波成像的多巴酚丁胺超声心动图负荷试验及多巴酚丁胺核磁共振负荷试验均在心导管插入术前实施。核磁共振负荷试验图像在短暂屏气时获得。取短轴切面3个,四腔心,二腔心切面各一个。检查时病人处于静息状态。标准的多巴酚丁胺,阿托品试验期间,心率应达到次极量。节段性室壁运动的划分按16节段法。当冠状动脉内径狭窄大于或等于50%时可确诊冠心病。结果:本组研究…     

定量实时心肌声学造影结合小剂量多巴酚丁胺负荷试验在冠心病诊断中的应用价值

目的评价定量实时心肌声学造影结合小剂量多巴酚丁胺负荷试验在冠心病诊断中的价值;评价侧支循环对心肌灌注的影响。方法26例住院患者进行了常规超声心动图、基础状态下和小剂量多巴酚丁胺负荷状态下的心肌声学造影以及选择性冠状动脉造影。造影图像采用QLab软件对微泡再充盈曲线进行定量分析,求出各节段的A值、β值及其乘积A×β值。对各节段心肌灌注参数和其供血冠状动脉的狭窄程度进行统计学分析。结果基础状态下,β值和A×β值随着供血冠状动脉狭窄程度的增加而降低(P<0.01);在负荷状态下,A值、β值和A×β值随着供血冠状动脉狭窄程度的增加而降低(P<0.01),且其储备值呈现出相同的趋势(P<0.01);侧支循环的存在与否显著影响各节段的心肌灌注参数及其储备值,且在严重狭窄节段中尤为明显(P<0.01)。结论定量实时心肌声学造影结合小剂量多巴酚丁胺负荷试验可以作为一种敏感的手段用于冠心病临床诊断及其危险性评估。     

Head-to-head comparison between contrast-enhanced magnetic resonance imaging and dobutamine magnetic resonance imaging in men with ischemic cardiomyopathy

Contrast-enhanced magnetic resonance imaging (MRI) can predict functional recovery after revascularization. Segments with small, subendocardial scars have a large likelihood of recovery, and segments with transmural infarction have a small likelihood of recovery. Segments with an intermediate extent of infarction have an intermediate likelihood of recovery, and therefore, additional information is needed. Accordingly, the transmurality of infarction on contrast-enhanced MRI was compared with low-dose dobutamine MRI to further define viability in 48 patients. Regional contractile dysfunction was determined by cine MRI at rest (17-segment model), and contractile reserve was determined using low-dose dobutamine infusion. Contrast-enhanced MRI was performed to assess the extent of scar tissue. A total of 338 segments (41%) were dysfunctional, with 61% having contractile reserve. Most segments (approximately 75%) with small, subendocardial scars (hyperenhancement scores 1 or 2) had contractile reserve, whereas contractile reserve was not frequently (17%) observed in segments with transmural infarction (hyperenhancement score 4) (p <0.05). Of segments with an intermediate infarct transmurality (hyperenhancement score 3), contractile reserve was observed in 42%, whereas 58% did not have contractile reserve. In conclusion, the agreement between contrast-enhanced MRI and low-dose dobutamine MRI is large in the extremes (subendocardial scars and transmural scars), and contrast-enhanced MRI may be sufficient to assess the likelihood of the recovery of function after revascularization. However, 61% of segments with an intermediate extent of scar tissue on MRI have contractile reserve and 39% lack contractile reserve. In these segments, low-dose dobutamine MRI may be needed to optimally differentiate myocardium with large and small likelihoods of functional recovery after revascularization.     

Transmural contractile reserve after reperfused myocardial infarction in dogs

OBJECTIVES

The goal of this study was to characterize detailed transmural left ventricular (LV) function at rest and during dobutamine stimulation in subendocardial and transmural experimental infarcts.

BACKGROUND

The relation between segmental LV function and the transmural extent of myocardial necrosis is complex. However, its detailed understanding is crucial for the diagnosis of myocardial viability as assessed by inotropic stimulation.

METHODS

Short-axis tagged magnetic resonance images were acquired at five to seven levels encompassing the LV from base to apex in seven dogs 2 days after a 90-min closed-chest left anterior descending coronary occlusion, followed by reflow. Myocardial strains were measured transmurally in the entire LV by harmonic phase imaging at rest and 5 ig.kg⁻¹.min⁻¹ dobutamine. Risk regions were assessed by radioactive microspheres, and the transmural extent of the infarct was assessed by 2,3,5 triphenyltetrazolium chloride staining.

RESULTS

Circumferential shortening (Ecc), radial thickening (Err) and maximal shortening at rest were greater in segments with subendocardial versus transmural infarcts, both in subepicardium (−1.1 ± 1.0 vs. 2.5 ± 0.6% for Ecc, −0.5 ± 1.9 vs. −1.8 ± 1.0% for Err, p < 0.05) and subendocardium (−2.0 ± 1.4 vs. 2.8 ± 0.8%, 2.4 ± 1.7 vs. 0.0 ± 0.9%, respectively, p < 0.05). Under inotropic stimulation, risk regions retained maximal contractile reserve. Recruitable deformation was found in outer layers of subendocardial infarcts (p < 0.01 for Ecc and Err) but also in inner layers (p < 0.01). Conversely, no contractile reserve was observed in segments with transmural infarcts.

CONCLUSIONS

Under dobutamine challenge, recruitment of myofiber shortening and thickening was observed in inner layers of segments with subendocardial infarcts. These results may have important clinical implications for the detection of myocardial viability.     

Differentiation of subendocardial and transmural infarction using two-dimensional strain rate imaging to assess short-axis and long-axis myocardial function.

OBJECTIVES: This study sought to differentiate the transmural extent of infarction (TME) by assessment of the short-axis and long-axis function of the left ventricle (LV) using 2-dimensional (2D) strain. BACKGROUND: The differentiation of subendocardial infarction from transmural infarction has significant prognostic and clinical implications. METHODS: Contrast-enhanced magnetic resonance imaging (CE-MRI) and dobutamine stress echocardiography (DBE) were performed in 80 patients (age 63 +/- 10 years) with chronic ischemic LV dysfunction. Myocardial function was assessed in the short axis at the midventricular level using peak strain rate (SR) and strain (S) in circumferential and radial dimensions, and was assessed in the long axis using longitudinal SR and S. Wall motion analysis was performed during DBE to assess for contractile reserve. RESULTS: Transmural infarct segments had lower circumferential S (-10.7 +/- 6.3) and SR (-1.0 +/- 0.4) than subendocardial infarcts (S: -15.4 +/- 7.0, p < 0.0001; SR: -1.4 +/- 0.8, p = 0.02) and normal myocardium (S: p < 0.0001; SR: p < 0.0001). Transmural and subendocardial infarct segments had similar radial S and SR. Subendocardial infarct segments showed significant reduction of longitudinal S (-13.2 +/- 5.6) and SR (-0.91 +/- 0.45) compared with normal myocardium (S: -17.8 +/- 5.4, p < 0.0001; SR: -1.1 +/- 0.41, p < 0.0001), but there were no significant differences between subendocardial and transmural infarct segments (p = 0.09). Wall motion analysis by DBE could not identify subendocardial infarction on CE-MRI (TME 1% to 50%: DBE scar 38%, DBE viable 38%, DBE ischemic 24%, p = NS). CONCLUSIONS: The combined assessment of long-axis and short-axis function using 2D strain may be used to identify TME.     

Which parameters on magnetic resonance imaging determine Q waves on the electrocardiogram?

Studies have demonstrated that patients with Q-wave infarctions on the electrocardiogram (ECG) frequently have nontransmural scar formation, whereas non-Q-wave infarctions may have transmural scars. The precise pathophysiologic substrate that underlies Q waves remains unclear. Magnetic resonance imaging (MRI) is the preferred technique to evaluate patients who have infarction because information can be obtained on function, contractile reserve (viability), and scar tissue. Consecutive patients (n = 69) who had coronary artery disease and a history of myocardial infarction underwent MRI; the protocol included MRI at rest, small-dose dobutamine MRI, and contrast-enhanced MRI. Parameters included left ventricular ejection fraction, left ventricular volumes, end-diastolic wall thickness and contractile reserve in the infarct region, transmurality and spatial extent of scar tissue, total scar score, and quantified percent left ventricular scar tissue. MRI data were related to the presence/absence of Q waves on the ECG. Q waves were present in 39 patients (57%). Univariate analysis identified transmurality, spatial extent, total scar score, and quantified percent scar tissue as predictors of Q waves. Multivariate analysis demonstrated that quantified percent scar tissue was the single best predictor of Q waves on the ECG. A cut-off value of 17% infarcted tissue of the left ventricle yielded a sensitivity and specificity of 90% to predict the presence/absence of Q waves. When quantified percent scar tissue was removed from the model, spatial extent of infarction was the best predictor. Thus, Q waves on the ECG correlate best with quantified percent scar tissue on contrast-enhanced MR images.     

Strain rate imaging differentiates transmural from non-transmural myocardial infarction: a validation study using delayed-enhancement magnetic resonance imaging

OBJECTIVES: The aim of this study was to determine if strain rate imaging (SRI) correlates with the transmural extent of myocardial infarction (MI) measured by contrast-enhanced magnetic resonance imaging (Ce-MRI). BACKGROUND: Identification of the transmural extent of myocardial necrosis and degree of non-viability after acute MI is clinically important. METHODS: Tissue Doppler echocardiography with SRI and Ce-MRI were performed in 47 consecutive patients with a first acute MI between days 2 and 6 and compared to 60 age-matched healthy volunteers. Peak myocardial velocities and peak myocardial deformation strain rates were measured. Location and size of the infarct zone was confirmed by Ce-MRI using the delayed enhancement technique with a 16-segment model. RESULTS: Contrast-enhanced MRI identified transmural infarction in 21 patients, non-transmural infarction in 15 (mean transmurality of infarct 72.3 +/- 10.6%), and another 11 patients with subendocardial infarction (<50% transmural extent of the left ventricular wall). Peak systolic strain rate (SRs) of the transmural infarction segments was significantly lower compared to normal myocardium or with non-transmural infarction segments (both p < 0.0005). A cutoff value of SRs >-0.59 s(-1) detected a transmural infarction with high sensitivity (90.9%) and high specificity (96.4%), and -0.98 s(-1) >SRs >-1.26 s(-1) distinguished subendocardial infarction from normal myocardium with a sensitivity of 81.3% and a specificity of 83.3%. CONCLUSIONS: Peak myocardial deformation by SRI can differentiate transmural from non-transmural MI, and it allows noninvasive determination of transmurality of the scar after MI and thereby the extent of non-viable myocardium.     

Accuracy of low load exercise-induced T wave normalization in predicting the presence of contractile reserve after an anterior myocardial infarction

Background and Methods. Exercise-induced T wave normalization occurring at a low (≤ 50 watt) workload in infarct-related electrocardiographic leads was studied in 30 consecutive patients with a recent transmural anterior acute myocardial infarction. Patients underwent both ergometric stress testing (within 30 days after the infarction) and low dose dobutamine echocardiography. The T wave normalization was considered significant when it occurred in at least two infarct-related leads. A significant contractile reserve was considered present in an infarcted region when 50% or more of the dyskinetic segments functionally improved on exercise during dobutamine infusion.Results. Eighteen patients showed exercise-induced T wave normalization (group 1), and 12 patients did not (group 2). Myocardial contractile reserve in the infarct area was detected in 16 patients of group 1 (88%) and in 3 patients (25%) of group 2 (p=0.004). The overall sensitivity, specificity, and diagnostic accuracy of T wave normalization, as it reflects contractile reserve in the infarct area, were 84%, 82%, and 83%, respectively.Conclusion. Low load exercise-induced T wave normalization in infarct-related leads appears to be an accurate marker of residual contractile reserve in the infarct area in patients with recent transmural acute anterior myocardial infarction.     

Contractile reserve and contrast uptake pattern by magnetic resonance imaging and functional recovery after reperfused myocardial infarction

OBJECTIVES: We hypothesized that contrast-enhanced and dobutamine tagged magnetic resonance imaging (MRI) could investigate microvascular integrity and contractile reserve of reperfused myocardial infarction (MI) in one examination. BACKGROUND: In reperfused MI, microvascular integrity and contractile reserve are important determinants of functional recovery. METHODS: Twenty-three patients with a reperfused first MI were studied. On day 3+/-1 after MI, patients underwent tagged MRI at baseline and during infusion of 5 and 10 microg/kg/min of dobutamine followed by contrast-enhanced MRI (first pass and delayed imaging) after a bolus infusion of gadolinium-diethylenetriaminepenta-acetic acid. Tagged MRI was performed 9+/-1 weeks later (follow-up). Eighty-four transmural regions with hyperenhancement on delayed contrast-enhanced images were defined as COMB (first pass hypoenhancement) or HYPER (normal first pass signal enhancement). Percent circumferential segment shortening was measured within the subendocardium and subepicardum of each region of HYPER or COMB at baseline, peak dobutamine and follow-up. RESULTS: Shortening improved in COMB regions from 4+/-1% at baseline to 10+/-1% at peak dobutamine and 10+/-1% at follow-up, respectively (p<0.0003 vs. baseline for both). The HYPER regions likewise improved from 10+/-1% at baseline to 16+/-1% and 17+/-1%, respectively (p<0.0004 vs. baseline for both). Function within COMB regions was less than that of HYPER at baseline, peak dobutamine and follow-up (p<0.0003 for all). CONCLUSIONS: Dobutamine magnetic resonance tagging and contrast enhanced MRI are complementary in assessing functional recovery after reperfused MI. Regions of delayed contrast hyperenhancement demonstrate both contractile reserve and late functional recovery. However, if these regions demonstrate first pass contrast hypoenhancement, they are associated with greater myocardial damage.     

计算机辅助心肌造影负荷超声定量评价心肌灌注及局部收缩功能

目的 探讨计算机辅助心肌造影负荷超声(MCSE)定量评价心肌灌注和局部收缩功能的应用价值.方法 采用急性阻断再灌注左室支建立兔模型,根据阻断和再灌注时间分为两组:阻断30 min后再灌注60 min(Ⅰ组)和阻断120 min后再灌注60 min(Ⅱ组).分别在基础状态、阻断、再灌注和多巴酚丁胺负荷(5、10、15和20 μg·kg-1·min-1)行心肌造影超声心动图,造影图像经自制计算机辅助软件处理后,自动标出每个节段的标化造影剂密度(CI),根据标化CI值,彩色编码标记为:0～ -20像素(pix)黄色、-21～ -40 pix蓝色、-41～ -70 pix绿色以及＜-70 pix红色.分别计算出阻断时和再灌注后红色编码区面积,并与荧光微球染色和氯化三苯基四氮唑染色面积对照分析.同时测量各阶段危险心肌的收缩期室壁增厚率(WT).结果 (1)阻断时,危险心肌的WT降到零点或呈负值,CI明显低于基础状态,红色编码区面积与荧光染色危险心肌面积呈正相关(r=0.91,P＜0.01).(2)再灌注和多巴酚丁胺5μg·kg-1·min-1后,各组危险心肌的WT和标化CI仍减低.以标化CI-70 pix为截断值,识别梗死节段的敏感性为95%,特异性为87%.红色编码面积与氯化三苯基四氮唑染色梗死心肌面积呈正相关(r=0.89,P＜0.01).(3)随着多巴酚丁胺剂量的增加,Ⅰ组的标化CI恢复至基础状态,WT逐渐增加超过基础水平,但Ⅱ组仍保持较低水平.结论 计算机辅助心肌造影负荷超声可以定量评价心肌灌注和局部收缩功能,是识别顿抑和梗死心肌安全可行的方法.     

Impact of scar thickness on the assessment of viability using dobutamine echocardiography and thallium single-photon emission computed tomography: a comparison with contrast-enhanced magnetic resonance imaging

OBJECTIVES: We sought to determine whether the transmural extent of scar (TES) explains discordances between dobutamine echocardiography (DbE) and thallium single-photon emission computed tomography (Tl-SPECT) in the detection of viable myocardium (VM). BACKGROUND: Discrepancies between DbE and Tl-SPECT are often attributed to differences between contractile reserve and membrane integrity, but may also reflect a disproportionate influence of nontransmural scar on thickening at DbE. METHODS: Sixty patients (age 62 +/- 12 years; 10 women and 50 men) with postinfarction left ventricular dysfunction underwent standard rest-late redistribution Tl-SPECT and DbE. Viable myocardium was identified when dysfunctional segments showed Tl activity >60% on the late-redistribution image or by low-dose augmentation at DbE. Contrast-enhanced magnetic resonance imaging (ceMRI) was used to divide TES into five groups: 0%, <25%, 26% to 50%, 51% to 75%, and >75% of the wall thickness replaced by scar. RESULTS: As TES increased, both the mean Tl uptake and change in wall motion score decreased significantly (both p < 0.001). However, the presence of subendocardial scar was insufficient to prevent thickening; >50% of segments still showed contractile function with TES of 25% to 75%, although residual function was uncommon with TES >75%. The relationship of both tests to increasing TES was similar, but Tl-SPECT identified VM more frequently than DbE in all groups. Among segments without scar or with small amounts of scar (<25% TES), >50% were viable by SPECT. CONCLUSIONS: Both contractile reserve and perfusion are sensitive to the extent of scar. However, contractile reserve may be impaired in the face of no or minor scar, and thickening may still occur with extensive scar.     

Comparison of myocardial infarct size assessed with contrast-enhanced magnetic resonance imaging and left ventricular function and volumes to predict mortality in patients with healed myocardial infarction

Currently, left ventricular (LV) ejection fraction (EF) and/or LV volumes are the established predictors of mortality in patients with coronary artery disease (CAD) and severe LV dysfunction. With contrast-enhanced magnetic resonance imaging (MRI), precise delineation of infarct size is now possible. The relative merits of LVEF/LV volumes and infarct size to predict long-term outcome are unknown. The purpose of this study was to determine the predictive value of infarct size assessed with contrast-enhanced MRI relative to LVEF and LV volumes for long-term survival in patients with healed myocardial infarction. Cine MRI and contrast-enhanced MRI were performed in 231 patients with healed myocardial infarction. LVEF and LV volumes were measured and infarct size was derived from contrast-enhanced MRI. Nineteen patients (8.2%) died during a median follow-up of 1.7 years (interquartile range 1.1 to 2.9). Cox proportional hazards analysis revealed that infarct size defined as spatial extent (hazard ratio [HR] 1.3, 95% confidence interval [CI] 1.1 to 1.6, chi-square 6.7, p=0.010), transmurality (HR 1.5, 95% CI 1.1 to 1.9, chi-square 8.9, p=0.003), or total scar score (HR 6.2, 95% CI 1.7 to 23, chi-square 7.4, p=0.006) were stronger predictors of all-cause mortality than LVEF and LV volumes. In conclusion, infarct size on contrast-enhanced MRI may be superior to LVEF and LV volumes for predicting long-term mortality in patients with healed myocardial infarction.