Quantification of myocardial salvage by myocardial perfusion SPECT and cardiac magnetic resonance — reference standards for ECG development

In order to determine the cardioprotective efficacy of acute reperfusion therapy, assessed as myocardial salvage, in patients with acute coronary occlusion, the final myocardial infarct (MI) size needs to be related to the amount of ischemic myocardium during coronary occlusion, referred to as the myocardium at risk (MaR). There are currently several imaging approaches available for quantification of both MI size and MaR in vivo of which some have been validated both in pre-clinical and clinical settings. These methods often involve the use of either myocardial perfusion SPECT or cardiac magnetic resonance (CMR). These imaging methods could potentially be used to further develop and validate ECG methods for determination of MI size and MaR. Therefore, the aim of the present review is to give an overview of myocardial perfusion SPECT and CMR methods available for assessment of myocardial salvage by determination of MI size and MaR.     

Fragmented QRS complexes are not hallmarks of myocardial injury as detected by cardiac magnetic resonance imaging in patients with acute myocardial infarction

Background

Q waves on a 12-lead electrocardiography (ECG) are considered to be classic hallmarks of prior myocardial infarction. However, one study suggested that the fragmented QRS complex (fQRS) on ECG is a highly sensitive and specific marker of myocardial scarring on a nuclear stress test. The study aimed to investigate the diagnostic accuracy of fragmented QRS complexes compared with Q waves for myocardial injury detected by delayed contrast-enhanced cardiovascular magnetic resonance imaging (DE-CMRI) in subjects with acute myocardial infarction.

Methods

Electrocardiograms of 190 subjects with myocardial infarction who underwent DE-CMR were analyzed. fQRS was defined by the presence of an additional R wave (R″), or notching of the S wave, or more than one R′ in two contiguous leads.

Results

Delayed enhancement was observed in 180 (94.7%) patients. Transmural enhancement was noted in 78 (43.3%) and subendocardial enhancement in 102 (56.7%) patients. The sensitivity and specificity of Q waved and fQRS for diagnosing delayed enhancement were 59.4% vs. 66.7% and 90.0% vs. 40.0%. The area under the receiver–operator characteristics curve of delayed enhancement was 0.75 for Q waves and 0.53 for fQRS (p = 0.04). The areas under the ROC curves of the transmurality of delayed enhancement were 0.44 for fQRS and 0.58 for Q waves (p = 0.73).

Conclusions

fQRS has poor accuracy for the detection of myocardial injury compared with Q waves. fQRS and Q waves are not valuable tools for the diagnosis transmural irreversible myocardial injury in acute myocardial infarction.     

Sequelae of acute myocardial infarction regarding cardiac structure and function and their prognostic significance as assessed by magnetic resonance imaging.

AIMS: Because of its high spatial resolution and tissue contrast, magnetic resonance imaging (MRI) was used to assess cardiac structure and function in a large population of patients with acute myocardial infarction (AMI). METHODS AND RESULTS: One hundred and ten patients were studied by MRI 6.1 +/- 2.2 days after AMI. Infarct size (IS), persistent microvascular obstruction (PMO), left and right ventricular (LV/RV) volumes, and functions were measured. The same MRI measurements were repeated in 89 patients after a mean follow-up period of 225 +/- 92 days. IS was 11.9 +/- 7.3% of total LV muscle mass. PMO was detected in 51/110 (46.4%) patients and comprised 15.6 +/- 8.5% of IS and 2.8 +/- 2.3% of LV muscle mass. Papillary muscle infarct was seen in 26%, RV infarction in 16%, pericarditis in 40%, and pericardial effusion in 66% of the patients. During follow-up, there were 16 major adverse cardiac events (MACE) including seven deaths. IS, PMO, and amount of transmural infarction were predictive for LV adverse remodelling defined as > 20% increase in LV end-diastolic volume. Multivariable analysis revealed LV end-diastolic volume, LV ejection fraction, and PMO as significant predictors for the occurrence of MACE. CONCLUSION: MRI is a highly sensitive and reliable tool to detect morphologic and functional sequelae of AMI providing baseline MRI parameters with relevant predictive power for LV adverse remodelling and occurrence of MACE.     

Kinematic analysis of left ventricular deformation in myocardial infarction using magnetic resonance cardiac tagging

The Magnetic Resonance (MR) tagging technique provides detailed information about 2D motion in the plane of observation. Interpretation of this information as a reflection of the 3D motion of the entire cardiac wall is a major problem. In finite element models of the mechanics of the infarcted heart, an infarcted region causes motional asymmetry, extending far beyond the infarct boundary. Here we present a method to quantify such asymmetry inamplitude and orientation. For this purpose images of a short-axis cross-section of the ejecting left ventricle were acquired from 9 healthy volunteers and 5 patients with myocardial infarction. MR-tags were applied in a 5 mm grid at end-diastole. The tags were tracked by video-image analysis. Tag motion was fitted to a kinematic model of cardiac motion. For the volunteers and the patients the center of the cavity displaced by about the same amount(p=0.11) during the ejection phase: 3.8 ± 1.4 and 3.0 ± 0.9 mm (mean ± sd), respectively. Cross-sectional rotation and the decrease in cross-sectional area of the cavity were both greater in the volunteers than in the patients: 6.4 ± 1.5 vs. 3.0 ± 0.8 degrees (p<0.001), and 945 ± 71 vs. 700 ± 176 mm 2 (p=0.02), respectively. In the patients, asymmetry of wall motion, as expressed by a sine wave dependency of contraction around the circumference, was significantly enlarged (p=0.02). The proposed method of kinematic analysis can be used to assess cardiac deformation in humans. We expect that by analyzing images of more cross-sections simultaneously, the 3D location and the degree of infarction can be assessed efficiently.     

Pseudo Wellens T-waves in patients with suspected myocardial infarction: how cardiac magnetic resonance imaging can help the diagnosis

Wellens' syndrome is characterized by symmetrically inverted T-waves in the precordial leads suggestive of impending myocardial infarction due to a critical proximal left anterior descending (LAD) stenosis. We describe three unusual cases of patients with such electrocardiographic abnormality in which coronary angiography ruled out the presence of critical coronary stenosis and cardiac magnetic resonance imaging excluded the presence of acute or chronic myocardial infarction.     

Usefulness of cardiac magnetic resonance imaging for detecting acute myocardial infarction in patients with no significant electrocardiogram changes

A 73-year-old man presented with suspected acute myocardial infarction at the outpatient clinic. However, the clinical symptoms and the laboratory findings were not diagnostic. Only emergency cardiac magnetic resonance imaging (MRI) was helpful in making a definitive diagnosis of acute myocardial infarction. Cardiac MRI is a useful diagnostic tool for suspected acute coronary syndrome in emergency room settings when conventional modalities do not provide a definitive diagnosis.     

Investigation of cardiomyopathy using cardiac magnetic resonance imaging part 1: Common phenotypes

Cardiac magnetic resonance imaging(CMRI) has emerged as a useful tertiary imaging tool in the investigation of patients suspected of many different types of cardiomyopathies,CMRI sequences are now of a sufficiently robust quality to enable high spatial and temporal resolution image acquisition.This has led to CMRI becoming an effective non-invasive imaging gold standard for many cardiomyopathies.In this 2-part review,we outline the typical sequences used to image cardiomyopathy,and present the imaging spectrum of cardiomyopathy.Part 1 focuses on the current classification of cardiomyopathy,basic CMRI sequences used in evaluating cardiomyopathy and the imaging spectrum of common phenotypes.     

131碘-间位碘代苄胍心肌显像探测急性心肌梗死后心脏交感神经分布和活力的变化

目的通过心脏交感神经受体显像探测急性心肌梗死(AMI)后心脏交感神经的分布和活力。方法 AMI组12例,男性11例,女性1例,年龄42～68岁,平均年龄(48±9)岁。对照组6名,男性4名,女性2名,年龄40～66岁,平均年龄(47±6)岁,为健康受试者。AMI组在AMI后2周、3个月及6个月时均行~(131)碘-间位碘代苄胍(~(131I-MIBG)受体显像及~(99m)锝-甲氧基异丁基异腈(~(99m)Tc-MIBI)心肌灌注显像(MPI),对照组在1周内完成~(131)I-MIBG受体显像及~(99m)Tc-MIBI MPI。分析~(131)I-MIBG及~(99m)TC-MIBI显像相同部位心肌节段的放射性分布,并利用感兴趣区(ROI)技术测定心肌与纵隔放射性比值(H/M)及MIBG的洗脱率(WR)。结果 (1)AMI组~(131)I-MIBG显像的放射性稀疏-缺损节段数为32个,而~(99m)Tc-MIBI显像的仪为24个。(2)AMI组在AMI后2周、3个月及6个月和对照组的~(131)I-MIBG显像H/M比值为(1.45±0.20)、(1.65±0.16)、(1.70±0.17)和(2.70±0.32),WR为32%、19%、15%和9.5%。AMI组各时间点的H/M和WR与对照组比较差异均有统计学意义(均为P0.05);AMI组2周分别与3个月和6个月比较,差异均有统计学意义(均为P0.05)。结论 AMI后交感神经受损区域明显大于MPI所显示的受损区域。AMI后心肌交感神经受体下调,表现为MIBG摄取减低;体内交感神经紧张度增高,表现为MIBG滞留时间短、洗脱率高。AMI后3～6个月内交感神经有不同程度的恢复。     

磁共振延迟增强显像诊断心肌梗死的临床研究

目的 了解磁共振延迟增强(MR-DE)显像在心肌梗死诊断中的临床意义。方法 42例拟诊冠心病的患者,按临床分为心肌梗死、心肌缺血、正常3组,行MR-DE显像,其中25例行冠状动脉造影(CAG),并按冠脉狭窄程度分为狭窄<50％,50％～99％和100％3组。计算MR-DE检出心肌梗死的敏感性与特异性,并分别分析临床分组和CAG分组的MR-DE结果。结果 利用延迟增强判断心肌梗死,敏感性、特异性和诊断准确性分别为87.5％,94.1％和92.8％。出现延迟增强的比例,在临床分组中,分别为87.5％,8.7％和0％;在CAG分组中,分別为0％,50％和100％。结论 MR-DE显像对心肌梗死诊断有较高临床意义。     

视频密度阶差评价急性心肌梗死者急诊冠状动脉介入治疗前后心肌微灌注的临床研究

目的:结合校正的TIMI记帧计数(CTFC),探讨视频密度阶差(VDS)在评价急性心肌梗死者急诊冠状动脉介入治疗(PCI)前后心肌微灌注中的应用价值。方法:计算120例急性心肌梗死行急诊PCI患者PCI术前后的CTFC和VDS,并统计患者急诊PCI前后的TIMI分级、左室射血分数、住院期间的心脏不良事件。结果:急诊PCI术前后VDS为10.2±3.8、20.8±7.6,术后显著高于术前(P<0.05);PCI后CTFC显著低于术前[(30.3±8.6)∶(22.4±5.6),P<0.05]。急诊PCI后:VDS明显低于冠状动脉造影正常者(P<0.05),CTFC与冠状动脉造影正常者差异无统计学意义(P>0.05)。VDS是住院期间心脏不良事件发生的独立相关因素。VDS≤20者的住院期间心脏不良事件发生显著高于VDS>20者和CTFC≤30者(P<0.05)。结论:VDS评价急性心肌梗死行急诊PCI者的心肌微灌注时较CTFC敏感性更高,可作为急性心肌梗死患者住院期间心脏不良事件发生的一个独立的预测指标。     

The effect of intra-aortic balloon counterpulsation on left ventricular functional recovery early after acute myocardial infarction: a randomized experimental magnetic resonance imaging study.

AIMS: We sought to determine whether intra-aortic balloon pump (IABP) counterpulsation improves the recovery of left ventricular (LV) systolic function after reperfused acute myocardial infarction (AMI). METHODS AND RESULTS: Fourteen dogs underwent 90-min coronary artery occlusion followed by reperfusion. Seven animals were randomized to IABP counterpulsation immediately after reperfusion. Tagged, cine, and contrast-enhanced magnetic resonance imaging were used for regional and global LV functional assessment and MI characterization, respectively. Image acquisition was performed at 1 h, 6 h, and 24 h after reperfusion, during which the IABP device was paused. Animals randomized to IABP demonstrated an earlier improvement of LV ejection fraction when compared with controls (25+/-3 vs. 25+/-2% at 1 h, P=0.91; 36+/-3 vs. 26+/-2% at 6 h, P=0.015; and 38+/-3 vs. 35+/-1% at 24 h, P=0.34). Regional functional analyses revealed the same behaviour among non-infarcted risk regions, i.e., earlier circumferential systolic strain improvement in the IABP group than in controls (-5.4+/-0.4 vs. -5.3+/-0.5% at 1 h, P=0.86; -12.1+/-1.0 vs. -6.0+/-0.4% at 6 h, P<0.001; and -13.9+/-1.1% vs. -12.8+/-0.6% at 24 h, P=0.40). Importantly, however, the degree of LV functional recovery 24 h after reperfusion was similar whether IABP counterpulsation was used or not. CONCLUSION: IABP counterpulsation accelerates but does not significantly improve the recovery of LV systolic function after reperfused AMI.     

Assessment of myocardial viability: comparison of echocardiography versus cardiac magnetic resonance imaging in the current era

Detecting viable myocardium, whether hibernating or stunned, is of clinical significance in patients with coronary artery disease and left ventricular dysfunction. Echocardiographic assessments of myocardial thickening and endocardial excursion during dobutamine infusion provide a highly specific marker for myocardial viability, but with relatively less sensitivity. The additional modalities of myocardial contrast echocardiography and tissue Doppler have recently been proposed to provide further, quantitative measures of myocardial viability assessment. Cardiac magnetic resonance (CMR) has become popular for the assessment of myocardial viability as it can assess cardiac function, volumes, myocardial scar, and perfusion with high-spatial resolution. Both 'delayed enhancement' CMR and dobutamine stress CMR have important roles in the assessment of patients with ischaemic cardiomyopathy. This article reviews the recent advances in both echocardiography and CMR for the clinical assessment of myocardial viability. It attempts to provide a pragmatic approach toward the patient-specific assessment of this important clinical problem.     

Regional myocardial perfusion reserve determined using myocardial perfusion magnetic resonance imaging showed a direct correlation with coronary flow velocity reserve by Doppler flow wire

Aims: Quantitative analysis of rest–stress myocardial perfusionmagnetic resonance imaging (MRI) can provide assessments ofregional myocardial perfusion reserve (MPR). The purpose ofthis study was to compare regional MPR determined by myocardialperfusion MRI with coronary flow reserve (CFR) by intracoronaryDoppler flow wire. Methods and results: Twenty patients with suspected coronary artery disease (CAD)were studied. Average peak velocity was measured by Dopplerflow wire in the resting state and during adenosine triphosphate(ATP) stress in 36 coronary arteries. CFR measurements for eachpatient were performed in the culprit and one non-culprit non-stenoticartery. First-pass, contrast-enhanced myocardial perfusion MRimages were obtained in the resting state and during ATP stresswithin the week before the Doppler wire procedure. Regionalmyocardial blood flow (MBF) was quantified in 16 myocardialsegments by analysing arterial input and myocardial output usinga Patlak plot method. MPR was calculated as stress MBF dividedby rest MBF. CFR measured by Doppler flow wire was comparedwith MPR in the myocardial segments corresponding to vesselterritories. The average MPR measured by perfusion MRI was 1.77± 0.62 for the culprit arteries and 3.45 ± 0.78for the non-culprit arteries, respectively (P < 0.001). Theaveraged CFR by Doppler flow wire was 1.72 ± 0.44 inthe culprit arteries and 3.14 ± 0.74 in the non-culpritarteries, respectively (P < 0.001). For both culprit andnon-culprit vessel groups, significant direct correlations wereobserved between MR assessments of MPR and Doppler assessmentsof CFR (culprit artery: R = 0.87, Non-culprit artery: R = 0.86)On Bland–Altman analysis, the mean differences betweenMPR determined by myocardial perfusion MRI and CFR measuredby Doppler wire were 0.05 in culprit arteries (95% limit ofagreement; –0.65 to 0.56) and 0.36 in non-culprit arteries(95% limit of agreement; –1.24 to 0.44). The sensitivityand specificity of MR measurement of MPR for predicting physiologicallysignificant reduction of Doppler CFR (<2) was 88% (95% CI61.7–98.5) and 90% (95% CI 68.3–98.8), respectively. Conclusion: The current results using Doppler flow wire as a reference methoddemonstrated that quantitative analysis of stress–restmyocardial perfusion MRI can provide a non-invasive assessmentof reduced MPR in patients with CAD.     

急性心肌梗死急诊冠状动脉造影正常患者临床分析

目的 :对比观察急性心肌梗死 ( AMI)急诊冠状动脉 (冠脉 )造影正常和异常患者的临床表现。方法 :94例 AMI患者行即刻经皮腔内冠脉成形术 ( PTCA)或溶栓治疗 ,溶栓者于溶栓开始后 90 m in行冠脉造影 ,梗死相关动脉 ( IRA)再通且无冠脉病变者为冠脉正常组 ,再通且并冠脉病变者及 PTCA成功者为冠脉异常组。记录两组患者冠心病易患因素 ,观察 ST段抬高总和 90 m in回落程度 ,比较两组患者住院期心脏事件发生率 ,并于出院前行超声心动图检查。结果 :94例患者中冠脉正常组 2 1例 ,冠脉异常组 73例。前者较后者年龄轻 ,男性、吸烟等诱因多见 ,且造影时 TIMI 3级多见 ;ST段抬高总和 90 m in回落大 ( P <0 .0 5 ) ;住院期间心脏事件发生率明显降低 ( P<0 .0 5 ) ;出院前超声心动图显示左室射血分数较大 ( P<0 .0 5 )。结论 :AMI急诊冠脉造影正常患者相对年轻 ,吸烟等诱因多见 ,住院期心功能和临床预后较好     

Role of cardiac magnetic resonance imaging in troponinemia syndromes

Cardiac magnetic resonance imaging (MRI) is an evolving technology, proving to be a highly accurate tool for quantitative assessment. Most recently, it has been increasingly used in the diagnostic and prognostic evaluation of conditions involving an elevation in troponin or troponinemia. Although an elevation in troponin is a nonspecific marker of myocardial tissue damage, it is a frequently ordered investigation leaving many patients without a specific diagnosis. Fortunately, the advent of newer cardiac MRI protocols can provide additional information. In this review, we discuss several conditions associated with an elevation in troponin such as myocardial infarction, myocarditis, Takotsubo cardiomyopathy, coronavirus disease 2019 related cardiac dysfunction and athlete’s heart syndrome.     

Doppler Tissue Imaging positive preejection velocity wave is a sign of non-transmural necrosis: comparison with delayed-enhancement cardiac magnetic resonance.

AIMS: Our purpose was to test the hypothesis that Tissue Doppler Imaging (TDI)-derived positive preejection velocity (PPV) is associated with transmural extent of necrosis in delayed-enhancement cardio-magnetic resonance (DE-CMR) in patients with reperfused myocardial infarction (MI). METHODS AND RESULTS: Longitudinal myocardial velocities were recorded by TDI in 24 patients with MI reperfused with primary angioplasty, using an Acuson-Sequoia equipment. The same day a CMR study was performed, including cine images in short axis and long axis views and DE images in the same views using a 3D-T1-Turbo-field-echo sequence, 15 min after administration of gadodiamide. Transmural extent of hyperenhancement in each segment was compared to presence or absence of PPV wave. A total of 384 segments were evaluated. Normo-hypokinetic segments (100%) showed a PPV wave, whereas it was only present in 53% of akinetic-dyskinetic segments (p=0.0005). One hundred percent of the segments with absent-mild DE showed a PPV wave; this percentage was lower in segments with intermediate and transmural DE (63 and 10%, p=0.001). The presence of PPV wave in an akinetic segment ruled out transmural necrosis with 97% sensitivity and 90% specificity. CONCLUSIONS: The absence of PPV is strongly associated to transmural necrosis in MI and therefore to absence of viability.     

急性ST段抬高心肌梗死中心脏破裂的认识

目的：研究对急性ST段抬高心肌梗死中心脏破裂的认识。方法选择2010年10月-2011年12月,我院收治的急性ST段抬高心肌梗死患者150例,对患者的心脏破裂进行诊断,并根据诊断结果将150例患者分成12例心脏破裂组,138例无心脏破裂组。观察两组患者的性别,年龄,治疗使用的方法。结果在心脏破裂中,年龄、性别,治疗方法的不同对其均有影响（P〈0.05）。结论心脏破裂是急性ST段抬高心肌梗死中最严重的并发症,了解急性ST段抬高心肌梗死中出现心脏破裂的因素,为临床医生在治疗时提供有利依据,延长患者的生命。