Assessment of myocardial viability in a porcine model of chronic coronary artery stenosis with dual dose dobutamine magnetic resonance imaging

In a non-surgical porcine coronary stenosis model resulting in chronic left ventricle dysfunction, we aimed in this study to evaluate the potential of magnetic resonance imaging (MRI) to distinguish dysfunctional but viable from necrotic myocardium by using multiple levels of dobutamine inotropic stimulation during a cine MRI protocol (F.P. van Rugge et al. Circulation 1994; 90: 127–138). We compared our results with histopathology. We were able to demonstrate a biphasic effect at increasing doses of dobutamine in a subgroup of animals with a high-grade coronary stenosis, while in another subgroup the coronary stenosis produced a chronic myocardial infarction, in which no functional recovery could be obtained. In this experimental protocol, dual dose dobutamine MRI proved to be an accurate and reproducible technique to perform viability studies in chronic obstructive coronary artery disease. It permits distinguishing chronic ischemic, but viable myocardium from infarcted tissue. The detection of chronically underperfused but potentially salvageable myocardium is of significant clinical importance since it may aid in determining which patients are eligible for revascularization.     

心肌梗死模型家猪存活心肌的磁共振延迟成像评价

背景:心脏磁共振延迟成像被认为是极有前景的无创性判断心肌存活状态的影像检查手段。目前常用的对比剂Gd-DTPA存在过高或过低评价存活心肌和不可逆性梗死心肌,而坏死亲和性对比剂ECIII-600可以准确地反映坏死心肌的面积。目的:对比冠脉内注射坏死亲和性对比剂在猪再灌注急性心肌梗死存活心肌诊断中的应用价值。方法:三四个月龄普通家猪12头,建立急性再灌注心肌梗死动物模型,分别冠脉内注射0.1mmol/kgGd-DTPA或0.005mmol/kgECIII-600。胸导R波触发心电门控,T1加权FAST序列,短轴面延迟强化扫描成像。扫描结束后沿短轴面将心脏切成6mm断面行氯化三苯基四氮唑染色和光镜检查。比较相应层面的MRI延迟强化区和氯化三苯基四氮唑染色所示梗死区的关系。结果与结论:注射Gd-DTPA的延迟成像10min时强化区面积与氯化三苯基四氮唑染色相比过高估计梗死心肌面积约21%,30min时强化区面积与氯化三苯基四氮唑染色结果一致,之后则过低估计坏死心肌的面积;注射ECIII-600的延迟磁共振成像在坏死区显示强烈而持续的对比增强,强化区面积与氯化三苯基四氮唑染色所示心肌梗死面积一致。说明ECIII-600增强磁共振延迟成像可以准确反映急性心肌梗死面积。Gd-DTPA评价心肌梗死面积不稳定,观察时间窗短,心脏磁共振成像应在对比剂注射后1h以内完成。     

心肌梗死模型家猪存活心肌的磁共振延迟成像评价

背景：心脏磁共振延迟成像被认为是极有前景的无创性判断心肌存活状态的影像检查手段。目前常用的对比剂Gd-DTPA存在过高或过低评价存活心肌和不可逆性梗死心肌,而坏死亲和性对比剂ECIII-600可以准确地反映坏死心肌的面积。目的：对比冠脉内注射坏死亲和性对比剂在猪再灌注急性心肌梗死存活心肌诊断中的应用价值。方法：三四个月龄普通家猪12头,建立急性再灌注心肌梗死动物模型,分别冠脉内注射0.1mmol/kgGd-DTPA或0.005mmol/kgECIII-600。胸导R波触发心电门控,T1加权FAST序列,短轴面延迟强化扫描成像。扫描结束后沿短轴面将心脏切成6mm断面行氯化三苯基四氮唑染色和光镜检查。比较相应层面的MRI延迟强化区和氯化三苯基四氮唑染色所示梗死区的关系。结果与结论：注射Gd-DTPA的延迟成像10min时强化区面积与氯化三苯基四氮唑染色相比过高估计梗死心肌面积约21%,30min时强化区面积与氯化三苯基四氮唑染色结果一致,之后则过低估计坏死心肌的面积;注射ECIII-600的延迟磁共振成像在坏死区显示强烈而持续的对比增强,强化区面积与氯化三苯基四氮唑染色所示心肌梗死面积一致。说明ECIII-600增强磁共振延迟成像可以准确反映急性心肌梗死面积。Gd-DTPA评价心肌梗死面积不稳定,观察时间窗短,心脏磁共振成像应在对比剂注射后1h以内完成。     

Assessment of intramyocardial hemorrhage by T1-weighted cardiovascular magnetic resonance in reperfused acute myocardial infarction

Background

Intramyocardialhemorrhage (IMH) reflects severe reperfusion injury in acute myocardial infarction. Non-invasive detection of IMH by cardiovascular magnetic resonance (CMR) may serve as a surrogate marker to evaluate the effect of preventive measures to reduce reperfusion injury and hence provide additional prognostic information. We sought to investigate whether IMH could be detected by CMR exploiting the T1 shortening effect of methemoglobin in an experimental model of acute myocardial infarction. The results were compared to T2-weighthed short tau inversion recovery (T2-STIR), and T2*-weighted(T2*W) sequences.

Methods and results

IMH was induced in ten 40 kg pigs by 50-min balloon occlusion of the mid LAD followed by reperfusion. Between 4–9 days (average 4.8) post-injury, the left ventricular myocardium was assessed by T1-weigthed Inversion Recovery(T1W-IR), T2-STIR, and T2*Wsequences. All CMR images were matched to histopathology and compared with the area of IMH. The difference between the size of the IMH area detected on T1W-IR images and pathology was −1.6 ± 11.3% (limits of agreement, -24%–21%), for the T2*W images the difference was −0.1 ± 18.3% (limitsof agreement, -36.8%–36.6%), and for T2-STIR the difference was 8.0 ± 15.5% (limits of agreement, -23%–39%). By T1W IR the diagnostic sensitivity of IMH was 90% and specificity 70%, for T2*W imaging the sensitivity was 70% and specificity 50%, and for T2-STIR sensitivity for imaging IMH was 50% and specificity 60%.

Conclusion

T1-weigthednon-contrast enhanced CMR detects IMH with high sensitivity and specificity and may become a diagnostic tool for detection of IMH in patients with myocardial infarction.     

心脏电机械标测与核素心肌显像评估急性心肌梗死患者存活心肌的比较

目的:比较心脏电机械标测系统(electromechanicalmapping,NOGA)、TM核素心肌显像和超声心动图在评估急性心肌梗死患者存活心肌状况的作用。方法:选择2003-01/04南京医科大学附属南京第一医院心内科住院并符合纳入标准的急性心肌梗死患者5例,均为男性,平均年龄(56±3)岁。急诊经皮冠状动脉腔内成形术后第7天分别进行NOGATM系统、心脏超声及核素心肌显像测定。结果:NOGA系统测定出梗死区域的单极电压(unipolarvoltagepoten-TMtials,UVP)犤(5.8±2)mV犦显著低于非梗死区域的心肌犤(11.9±3)mV,P<0.01犦,同时测得梗死区域心肌的内膜下心肌短缩率(linearlocalshortening,LLS)犤(0.7±0.2)%犦明显小于非梗死区域心肌犤(11.2±4)%,P<0.01犦。特征性曲线分析NOGATM判断心肌存活状态的UVP界定值为8.0mV敏感性及特异性均为88%。()结论:LLS与心脏超声相关性良好,当UVP≥8.0mV时提示心肌处于存活状态。     

Gender differences in contrast-enhanced magnetic resonance imaging after acute myocardial infarction

Besides different risk profiles for cardiovascular events in men and women, several studies reported gender differences in mortality after acute myocardial infarction (AMI). As infarct size has been shown to correlate with mortality, it is widely accepted as surrogate marker for clinical outcome. Currently, cardiovascular imaging studies covering the issue of gender differences are rare. As magnetic resonance scar characterization parameters are emerging as additional prognostic factors after acute myocardial infarction, we sought to evaluate gender differences in CMR infarct characteristics in patients after acute myocardial infarction. We prospectively analyzed patients (n = 448) with AMI and primary angioplasty, who underwent contrast enhanced cardiac magnetic resonance (CMR) imaging on a 1.5 T scanner in median 5 [Galatius-Jensen et al. in BMJ 313(7050):137–140, (1996), Burns et al. in J Am Coll Cardiol 39(1):30–36, (2002)] days after the acute event. CMR scar size was measured 15 min after gadolinium injection. In addition presence and extent of microvascular obstruction (MVO) was assessed. A matched pair analysis was performed in order to exclude confounding by gender related co-morbidities and gender differences in established clinical risk factors. Matching process according to clinical risk defined by GRACE score resulted in 93 mixed gender couples. Women were significantly older than men (64.4 ± 11.9 vs. 60.5 ± 12.3, p = 0.03) and presented with a significantly better ejection fraction before angioplasty (48.9 ± 8.4 vs. 46.2 ± 8.9, p = 0.04). Infarct size did not differ significantly between women and men (13.5 ± 10.7 vs. 15.1 ± 11.8, p = 0.32). Size of MVO was significantly smaller in women than in men (0.48 ± 1.3 vs. 1.2 ± 3.0, p = 0.03). Comparing scar characterization between women and men with similar risk profiles revealed no gender differences in scar size. Size of MVO, however, was significantly smaller in women and might reflect better cardioprotective mechanisms in women. Whether these changes have prognostic implications has to be tested on a larger patient population.     

磁共振扩散张量成像定量分析猪心肌梗死早期离体心肌结构变化

目的 利用磁共振扩散张量成像(DT-MRI)研究急性心肌梗死(AMI)后离体心肌纤维束结构的改变。方法 制作实验用中华小型猪AMI模型并进行离体心脏DT-MRI。纤维束示踪技术(FT)显示梗死与正常心肌纤维结构,定量分析梗死与正常心肌ADC、 FA、心肌纤维束长度和数量。采用配对样本t检验及Wilcoxon检验进行统计学分析。结果 FT显示正常心肌纤维走行规则,排列整齐,梗死心肌纤维结构松散,纤维长短不一。与正常心机相比,梗死心肌ADC值增加,FA值减小,心肌纤维束长度缩短,纤维数目稍减少。结论 AMI后8 h即可在DT-MR图像上显示水分子扩散特性及心肌纤维结构的改变。     

Susceptibility-weighted cardiovascular magnetic resonance in comparison to T2 and T2 star imaging for detection of intramyocardial hemorrhage following acute myocardial infarction at 3 Tesla

Background

Intramyocardial hemorrhage (IMH) identified by cardiovascular magnetic resonance (CMR) is an established prognostic marker following acute myocardial infarction (AMI). Detection of IMH by T2-weighted or T2 star CMR can be limited by long breath hold times and sensitivity to artefacts, especially at 3T. We compared the image quality and diagnostic ability of susceptibility-weighted magnetic resonance imaging (SW MRI) with T2-weighted and T2 star CMR to detect IMH at 3T.

Methods

Forty-nine patients (42 males; mean age 58 years, range 35–76) underwent 3T cardiovascular magnetic resonance (CMR) 2 days following re-perfused AMI. T2-weighted, T2 star and SW MRI images were obtained. Signal and contrast measurements were compared between the three methods and diagnostic accuracy of SW MRI was assessed against T2w images by 2 independent, blinded observers. Image quality was rated on a 4-point scale from 1 (unusable) to 4 (excellent).

Results

Of 49 patients, IMH was detected in 20 (41%) by SW MRI, 21 (43%) by T2-weighted and 17 (34%) by T2 star imaging (p = ns). Compared to T2-weighted imaging, SW MRI had sensitivity of 93% and specificity of 86%. SW MRI had similar inter-observer reliability to T2-weighted imaging (κ = 0.90 and κ = 0.88 respectively); both had higher reliability than T2 star (κ = 0.53). Breath hold times were shorter for SW MRI (4 seconds vs. 16 seconds) with improved image quality rating (3.8 ± 0.4, 3.3 ± 1.0, 2.8 ± 1.1 respectively; p < 0.01).

Conclusions

SW MRI is an accurate and reproducible way to detect IMH at 3T. The technique offers considerably shorter breath hold times than T2-weighted and T2 star imaging, and higher image quality scores.     

Three-dimensional regional strain analysis in porcine myocardial infarction: a 3T magnetic resonance tagging study

Background

Previous studies of mechanical strain anomalies in myocardial infarction (MI) have been largely limited to analysis of one-dimensional (1D) and two-dimensional (2D) strain parameters. Advances in cardiovascular magnetic resonance (CMR) methods now permit a complete three-dimensional (3D) interrogation of myocardial regional strain. The aim of this study was to investigate the incremental value of CMR-based 3D strain and to test the hypothesis that 3D strain is superior to 1D or 2D strain analysis in the assessment of viability using a porcine model of infarction.

Methods

Infarction was induced surgically in 20 farm pigs. Cine, late gadolinium enhancement, and CMR tagging images were acquired at 11 days before (baseline), and 11 days (early) and 1 month (late) after induction of infarct. Harmonic phase analysis was performed to measure circumferential, longitudinal, and radial strains in myocardial segments, which were defined based on the transmurality of delayed enhancement. Univariate, bivariate, and multivariate logistic regression models of strain parameters were created and analyzed to compare the overall diagnostic accuracy of 3D strain analysis with 1D and 2D analyses in identifying the infarct and its adjacent regions from healthy myocardium.

Results

3D strain differed significantly in infarct, adjacent, and remote segments (p < 0.05) at early and late post-MI. In univariate, bivariate, and multivariate analyses, circumferential, longitudinal, and radial strains were significant factors (p < 0.001) in differentiation of infarct and adjacent segments from baseline values. In identification of adjacent segments, receiver operating characteristic analysis using the 3D strain multivariate model demonstrated a significant improvement (p < 0.01) in overall diagnostic accuracy in comparison with 2D (circumferential and radial) and 1D (circumferential) models (3D: 96%, 2D: 81%, and 1D: 71%). A similar trend was observed in identification of infarct segments.

Conclusions

Cumulative 3D strain information accurately identifies infarcts and their neighboring regions from healthy myocardium. The 3D interrogation of myocardial contractility provides incremental diagnostic accuracy in delineating the dysfunctional and nonviable myocardium in comparison with 1D or 2D quantification of strain. The infarct neighboring regions are the major beneficiaries of the 3D assessment of regional strain.     

Noncontact mapping of ventricular tachycardia in a closed-chest animal model of chronic myocardial infarction

Treatment of ventricular tachyarrhythmias in the setting of chronic myocardial infarction requires accurate characterization of the arrhythmia substrate. New mapping technologies have been developed that facilitate identification and ablation of critical areas even in rapid, hemodynamically unstable ventricular tachycardia. A noncontact mapping system was used to analyze induced ventricular tachycardia in a closed-chest sheep model of chronic myocardial infarction. Twelve sheep were studied 96 +/- 10 days after experimental myocardial infarction. During programmed stimulation, 15 different ventricular tachycardias were induced in nine animals. Induced ventricular tachycardia had a mean cycle length of 190 +/- 30 ms. In 12 ventricular tachycardias, earliest endocardial activity was recorded from virtual electrodes, preceding the surface QRS onset by 30 +/- 7 ms. Noncontact mapping identified diastolic activity in ten ventricular tachycardias. Diastolic potentials were recorded over a variable zone, spanning more than 30 mm. Timing of diastolic potentials varied from early to late diastole and could be traced back to the endocardial exit site. Entrainment with overdrive pacing was attempted in nine ventricular tachycardias, with concealed entrainment observed in seven. Abnormal endocardium in the area of chronic myocardial infarction identified by unipolar peak voltage mapping was confirmed by magnetic resonance imaging. These data suggest that induced ventricular tachycardia in the late phase of myocardial infarction in the sheep model is due to macroreentry involving the infarct borderzone. The combination of this animal model with noncontact mapping technology will allow testing of new strategies to cure and prevent ventricular tachycardia in the setting of chronic myocardial infarction.     

Reliability of myocardial salvage assessment by cardiac magnetic resonance imaging in acute reperfused myocardial infarction

Myocardial salvage assessed by cardiac magnetic resonance imaging (CMRI) holds promise as a surrogate endpoint in studies comparing different treatment strategies for ST-elevation myocardial infarction (STEMI). The aim of this study was to evaluate the reliability of salvaged myocardium measurements by CMRI. Twenty patients underwent CMRI on 2 consecutive days early after reperfused STEMI to assess the area at risk (AAR) on T2-weighted and final infarct size (IS) on delayed enhancement images. Myocardial salvage index (MSI) was calculated (AAR minus IS). Agreement between scans 1 and 2 for the AAR, IS and MSI were analyzed using Bland?CAltman analyses. Inter- and intraobserver reliability were assessed. Paired t testing revealed a trend for a significant difference for MSI between scans 1 and 2 (scan 1: 43.8?±?22.5; scan 2: 45.5?±?22.0; P?=?0.052). The average difference for AAR and IS between scan 1 and scan 2 was ?0.5 (upper limit of agreement 5.4% of left ventricular [LV] volume; lower limit of agreement ?6.4%LV) and 0.1%LV (upper limit of agreement 2.3%LV; lower limit of agreement ?2.1%LV). The corresponding calculated MSI measurements showed a mean bias of ?1.7 (upper limit of agreement 5.5; lower limit of agreement ?8.9). Coefficients of repeatability for interobserver variability were 3.6%LV for AAR, 2.4%LV for IS and 5.4 for MSI. Likewise, for intraobserver variability, coefficients of repeatability were 5.0%LV (AAR), 2.4%LV (IS) and 4.8 (MSI). Assessment of myocardial salvage by CMRI shows acceptable reliability. Further validation studies and trials showing the prognostic value of myocardial salvage by CMRI are needed before routine implementation as a surrogate endpoint in STEMI trials.     

Investigation of T2-weighted signal intensity of infarcted myocardium and its correlation with delayed enhancement magnetic resonance imaging in a porcine model with reperfused acute myocardial infarction

To assess the signal pattern in T2-weighted images (T2WI) and determine its relation to persistent microvascular obstruction (PMO) and intramyocardial hemorrhage in a porcine model with reperfused acute myocardial infarction. Left anterior descending artery was occluded (90 or 180 min) and reperfused (90 min). T2WI and delayed-enhanced magnetic resonance images (DE-MRI) were acquired. The T2WI signal pattern, T2WI contrast ratio, PMO, and intramyocardial hemorrhage were evaluated, and their interrelationships were analyzed. The infarct area on T2WI was recorded as a homogeneous high-intensity signal or as low- or iso-intensity signals. The contrast ratio of the T2WI in the cases with PMO was significantly lower than that in those without PMO (1.38 ± 0.25 vs. 1.89 ± 0.31, P < 0.05), and it showed significant inverse correlation with the extent of PMO observed in DE-MRI images (r =?0.8, P < 0.05). The extent of PMO correlated strongly with that of intramyocardial hemorrhage (r = 0.97, P < 0.05). The abnormal signal area in the T2WI was larger than the infarct area in the DE-MRI images (47.0 ± 9.9% vs. 37.8 ± 9.9%, P < 0.05) and the infarct area observed after TTC staining (47.0 ± 9.9% vs. 37.4 ± 8.4%, P < 0.05). We observed variable T2WI signal patterns for the infarcted myocardium. Lower T2WI contrast ratios significantly correlated with the extent of PMO in DE-MRI and intramyocardial hemorrhage in the gross specimen.     

Investigation of T2-weighted signal intensity of infarcted myocardium and its correlation with delayed enhancement magnetic resonance imaging in a porcine model with reperfused acute myocardial infarction

To assess the signal pattern in T2-weighted images (T2WI) and determine its relation to persistent microvascular obstruction (PMO) and intramyocardial hemorrhage in a porcine model with reperfused acute myocardial infarction. Left anterior descending artery was occluded (90 or 180 min) and reperfused (90 min). T2WI and delayed-enhanced magnetic resonance images (DE-MRI) were acquired. The T2WI signal pattern, T2WI contrast ratio, PMO, and intramyocardial hemorrhage were evaluated, and their interrelationships were analyzed. The infarct area on T2WI was recorded as a homogeneous high-intensity signal or as low- or iso-intensity signals. The contrast ratio of the T2WI in the cases with PMO was significantly lower than that in those without PMO (1.38 ± 0.25 vs. 1.89 ± 0.31, P < 0.05), and it showed significant inverse correlation with the extent of PMO observed in DE-MRI images (r =−0.8, P < 0.05). The extent of PMO correlated strongly with that of intramyocardial hemorrhage (r = 0.97, P < 0.05). The abnormal signal area in the T2WI was larger than the infarct area in the DE-MRI images (47.0 ± 9.9% vs. 37.8 ± 9.9%, P < 0.05) and the infarct area observed after TTC staining (47.0 ± 9.9% vs. 37.4 ± 8.4%, P < 0.05). We observed variable T2WI signal patterns for the infarcted myocardium. Lower T2WI contrast ratios significantly correlated with the extent of PMO in DE-MRI and intramyocardial hemorrhage in the gross specimen.     

Depression and myocardial injury in ST-segment elevation myocardial infarction: A cardiac magnetic resonance imaging study

BACKGROUND Depression is common in patients with myocardial infarction and has been independently associated with adverse outcomes.However,the association between depression and myocardial injury on cardiac magnetic resonance(CMR)in patients with ST-segment elevation myocardial infarction(STEMI)has still not been assessed.AIM To assess the association between depression and myocardial injury on CMR in patients with STEMI.METHODS A total of 107 STEMI patients undergoing primary percutaneous coronary intervention(P-PCI)were analyzed in this prospectivecohort study.Each subject completed the Patient Health Questionnaire-9(PHQ-9)to assess the presence and severity of depressive symptoms.CMR was performed at a median of 3 d after PPCI for quantifying post-MI myocardial injury.Correlations between depression identified by the PHQ-9 and myocardial injury measured on CMR were assessed.RESULTS In this study,19 patients(17.8%)were diagnosed with major depression identified by the PHQ-9≥10.PHQ-9 was analyzed both as a continuous variable and dichotomous variable.After multivariable adjustment,the proportion of patients with large infarction size was significantly higher in the major depression group(PHQ-9≥10)(OR:4.840,95%CI:1.122–20.868,P=0.034).When the PHQ-9 was evaluated as a continuous variable,after multivariable adjustment,an increased PHQ-9 score was associated with an increased risk of large infarction size(OR:1.226,95%CI:1.073–1.401,P=0.003).CONCLUSION In patients with STEMI undergoing PCI,depression was independently associated with a large infarction size.     

实时、谐波和超谐波心肌超声造影技术检测急性心肌梗死面积准确性的对比研究

目的 对比实时、谐波和超谐波三种心肌超声造影技术评价心肌缺血的准确性.方法 10条常规开胸犬动物模型,在基础状态、结扎冠状动脉左前降支1 h后,分别应用实时、谐波和超谐波技术采集心肌超声造影图像,目测观察充盈缺损的范围,定量计算充盈缺损的面积,并与应用TTC染色测量的梗死心肌面积对比.结果 TTC染色显示心肌梗死面积百分率为(15.8±2.4)%,应用三种心肌超声造影模式计算的充盈缺损面积与解剖学梗死心肌面积高度相似,实时模式为(16.1±2.7)%,谐波模式为(15.5±2.9)%,超谐波模式为(15.5±3.0)%.三种心肌超声造影模式检测急性心肌梗死的敏感性、特异性及诊断准确性分别为:在实时模式为100%、88%、94%;在谐波模式为88%、100%、94%;在超谐波模式为100%、75%、88%.结论 三种心肌超声造影技术在诊断急性心肌缺血中均具有高度的准确性.     

MRI示踪技术在心梗干细胞移植治疗中的应用现状

干细胞移植是治疗心肌梗死的新策略,MRI既可以提供心血管详细解剖结构和功能信息,还能有效地示踪细胞,从而更好的监测和观察细胞移植的情况。目前常规的示踪方法是通过超顺磁性氧化铁颗粒直接标记细胞,这种示踪方式可以确定细胞移植的在体内的分布,然而其特异性较差,不能反映细胞的存活情况。而MRI报告基因成像在一定程度上避免了传统超顺磁性氧化铁直接标记细胞示踪法的劣势,可以验证细胞的存活,通过这种方法可以更深入的认识移植细胞的存活和分化情况。     

心肌梗死的心脏磁共振成像技术临床应用及其研究现状

心肌梗死是缺血性心肌病中最严重的类型,症状较典型,故诊断本病并不困难.准确评估患者梗死心肌的范围,以及区别可逆性和不可逆性心肌损伤,对临床进行危险分层及确定治疗方案至关重要.近年来,随着心脏磁共振技术的快速发展,其在心脏疾病特别是缺血性心脏病中的应用越来越受到重视,一些新的磁共振成像方法的开发和应用,为临床诊断和治疗提...     

The effect of microvascular obstruction and intramyocardial hemorrhage on contractile recovery in reperfused myocardial infarction: insights from cardiovascular magnetic resonance

Background

Following acute myocardial infarction (AMI), microvascular obstruction (MO) and intramyocardial hemorrhage (IMH) adversely affect left ventricular remodeling and prognosis independently of infarct size. Whether this is due to infarct zone remodeling, changes in remote myocardium or other factors is unknown. We investigated the role of MO and IMH in recovery of contractility in infarct and remote myocardium.

Methods

Thirty-nine patients underwent cardiovascular magnetic resonance (CMR) with T2-weighted and T2* imaging, late gadolinium enhancement (LGE) and myocardial tagging at 2, 7, 30 and 90 days following primary percutaneous coronary intervention for AMI. Circumferential strain in infarct and remote zones was stratified by presence of MO and IMH.

Results

Overall, infarct zone strain recovered with time (p < 0.001). In the presence of MO with IMH and without IMH, epicardial strain recovered (p = 0.03, p < 0.01 respectively), but mid-myocardial or endocardial strain did not (mid-myocardium: p = 0.05, p = 0.12; endocardium: p = 0.27, p = 0.05, respectively). By day 90, infarcts with MO had more attenuated strain in all myocardial layers compared to infarcts without MO (p < 0.01); those with IMH were attenuated further (p < 0.01). Remote myocardial strain was similar across groups at all time-points (p > 0.2). Infarct transmural extent did not correlate with strain (p > 0.05 at each time point). In multivariable logistic regression, MO and IMH were the only significant independent predictors of attenuated 90-day infarct zone strain (p = 0.004, p = 0.011, respectively).

Conclusions

Strain improves within the infarct zone overall following reperfusion with or without MO or IMH. Mid-myocardial and endocardial infarct contractility is diminished in the presence of MO, and further in the presence of IMH. MO and IMH are greater independent predictors of infarct zone contractile recovery than infarct volume or transmural extent.