Left ventricular diastolic function compared with T2* cardiovascular magnetic resonance for early detection of myocardial iron overload in thalassemia major

PURPOSE: To compare left ventricular (LV) diastolic function with myocardial iron levels in beta thalassemia major (TM) patients, using cardiovascular magnetic resonance (CMR). MATERIALS AND METHODS: We studied 67 regularly transfused patients with TM and 22 controls matched for age, gender, and body surface area. The early peak filling rate (EPFR) and atrial peak filling rate (APFR) were determined from high-temporal-resolution ventricular volume-time curves. Myocardial iron estimation was achieved using myocardial T2* measurements. RESULTS: Myocardial iron loading was found in 46 TM patients (69%), in whom the EPFR correlated poorly with T2* (r = -0.20, P = 0.19). The APFR (r = 0.49, P < 0.001) and EPFR/APFR ratio (r = -0.62, P < 0.001) correlated better with T2*. The sensitivity of the diastolic parameters for detecting myocardial iron loading ranged from 4% (EPFR and APFR) to 17% (EPFR/APFR ratio). CONCLUSION: Myocardial iron overload results in diastolic myocardial dysfunction, but low sensitivity limits the use of a single estimation for early detection of iron overload, for which T2* has a superior categorical limit of normality.     

Measurement of left ventricular dimensions and function in patients with dilated cardiomyopathy

Studies on medical therapy in heart failure are focused on changes of left ventricular (LV) dimensions and function. These changes may be small, requiring a large study group. We measured LV parameters (LV volumes, LV ejection fraction (LV-EF), and left ventricular mass (LVM)) with two-dimensional echocardiography (2D-echo) and magnetic resonance imaging (MRI) in 50 patients. Based on the difference between the measurements, we determined the variance of the results and calculated the sample sizes needed to detect changes of baseline values. For the calculated and measured parameters we found significant differences between the two techniques: LV-EF and LVM were higher in 2D-echo, and LV dimensions were comparable. The sample size to detect relevant changes from baseline with MRI was significantly (P < 0.01) smaller than in 2D-echo. We conclude that MRI is superior in clinical studies on left ventricular dimensional and functional changes, since measurements are more reproducible and the required sample size is substantially smaller, thereby reducing costs.     

美托洛尔对难治性正常射血分数性急性左心衰患者心功能影响的临床研究

目的探讨高选择性β1-受体阻滞剂治疗射血分数正常的难治性急性左心室衰竭的可行性、安全性和有效性。方法①纳入50例发病在24h内,首次因端坐呼吸及呼吸困难突出者而诊断为急性左心衰竭,但超声检查射血分数（LVEF）≥45%;②经标准药物治疗无效或加重,NYHA分级达到Ⅳ级心功能的患者;③监测中心静脉压、血压、心率、血氧饱和度及血气分析、肺部罗音、呼吸次数、尿量,以及临床症状;④静脉推注美托洛尔5mg后,口服美托洛尔6.25～25mg,必要时4h重复给予美托洛尔12.5～25mg口服;④给药前后每4h测量中心静脉压1次;⑤治疗前床旁心脏彩超评价心功能变化;⑥停用正性肌力强心药物。结果①NYHA心功能改善≥1级者12例（24%）,改善2级者17例（34%）,改善3级者24例（48%）,无改善者3例（6%）,院内死亡2例（4%）;平均NYHA分级改善程度为2.24±0.89级,P〈0.01,有统计学意义;②在利尿、扩血管治疗基础上加用美托洛尔治疗后收缩压下降17.16±26.70mmHg,舒张压下降12.32±18.88mmHg,心率下降48.26±20.22次/min,中心静脉压（CVP）下降7.26±4.28cmH2O,P〈0.01,有统计学意义;③治疗后CVP为11.74±3.58cmH2O,与心功能改善程度的相关系数（r）=-0.389,P〈0.01;④美托洛尔的平均剂量为76.50±40.30mg/日,剂量与CVP下降程度相关（r=0.307,P=0.03）,与心率的下降显著相关（r=0.643,P=0.000）;⑤心率的下降程度与中心静脉压下降程度具有显著相关性（r=0.435,P=0.002）。结论传统方法治疗无效的射血分数正常心力衰竭患者,在接受利尿剂、扩血管药物治疗的基础上联合β受体阻滞剂美托洛尔可以显著降低血压、心率及中心静脉压水平,尤其通过降低心率使中心静脉压水平下降更有意义,从而改善心力衰竭的临床预后。     

射血分数保留的心力衰竭左心室舒张功能的影像学评价

射血分数保留的心力衰竭发病率在逐年上升。准确测量左室舒张功能有利于对该病的临床评价。目前可采用超声心动图、心脏MRI(CMRI)及其他多种检查方法评价左室舒张功能,并对舒张功能的病生理机制、舒张功能障碍分级有提示作用。其中CMRI技术的作用日益突出,包括舒张期容积-时间曲线、二尖瓣血流与肺静脉血流成像、心肌标记及其他CMRI技术。     

Preferential patterns of myocardial iron overload by multislice multiecho T*2 CMR in thalassemia major patients

T*₂ multislice multiecho cardiac MR allows quantification of the segmental distribution of myocardial iron overload. This study aimed to determine if there were preferential patterns of myocardial iron overload in thalassemia major. Five hundred twenty‐three thalassemia major patients underwent cardiac MR. Three short‐axis views of the left ventricle were acquired and analyzed using a 16‐segment standardized model. The T*₂ value on each segment was calculated, as well as the global value. Four main circumferential regions (anterior, septal, inferior, and lateral) were defined. Significant segmental variability was found in the 229 patients with significant myocardial iron overload (global T*₂ <26 ms), subsequently divided into two groups: severe (global T*₂ <10 ms) and mild to moderate (global T*₂ between 10 and 26 ms) myocardial iron overload. A preferential pattern of iron store in anterior and inferior regions was detected in both groups. This pattern was preserved among the slices. The pattern could not be explained by additive susceptibility artifacts, negligible in heavily iron‐loaded patients. A significantly higher T*₂ value in the basal slice was found in patients with severe iron overload. In conclusion, a segmental T*₂ cardiac MR approach could identify early iron deposit, useful for tailoring chelation therapy and preventing myocardial dysfunction in the clinical setting. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Reproducibility of MRI measurements of right ventricular size and function in patients with normal and dilated ventricles

PURPOSE: To determine the inter- and intraobserver reproducibility of cardiac magnetic resonance (CMR)-derived measurements of right ventricular (RV) mass, volume, and function in patients with normal and dilated ventricles. MATERIALS AND METHODS: CMR studies of 60 patients in three groups were studied: a normal RV group (N = 20) and two groups with RV dilation-atrial septal defect (ASD) (N = 20) and repaired tetralogy of Fallot (TOF) (N = 20). Two independent observers analyzed each study on two separate occasions. Inter- and intraobserver reproducibility of biventricular mass, volume, ejection fraction (EF), and stroke volume (SV) measurements were calculated. RESULTS: High intraclass correlation coefficients (ICC) were found for interobserver (ICC = 0.94-0.99) and intraobserver (ICC = 0.96-0.99) comparisons of RV and left ventricular (LV) mass, volume, and SV measurements. RV and LV EF measurements were less reproducible (ICC = 0.79-0.87). RV mass measurements were significantly less correlated than the respective LV measurements. Small but statistically significant differences in correlation were noted in RV measurements across groups. CONCLUSION: Except for RV mass, inter- and intraobserver reproducibility of RV size and function measurements is high and generally comparable to that in the LV in patients with both normal and dilated RV.     

Evaluation of left ventricle diastolic dysfunction in ischemic heart disease by CMR: Correlation with echocardiography and myocardial scarring

Objective

To detect the value of cardiac MR imaging in assessment of left ventricle diastolic function in patients with ischemic heart disease compared to echocardiography and to correlate the degree of dysfunction to the extent of myocardial scarring.

Patients and methods

We examined 40 patients with known coronary artery disease. Mean patient’s age was 48 ± 10. All patients were subjected to 2D echocardiography and CMR including transmitral flow and left atrial planimetry. The degree of diastolic dysfunction was detected and correlated with the echocardiographic results and the extent of myocardial scarring.

Results

On CMR, 35% of the cases had grade I diastolic dysfunction, 35% showed grade II, 15% had grade III while 15% showed normal diastolic function. CMR showed 94.12% sensitivity, 100% specificity and 95% accuracy. Excellent agreement with echocardiography was detected (Kappa coefficient 0.931). There was a significant correlation between the degree of diastolic dysfunction and the extent of myocardial scarring with Spearman’s correlation coefficient of 0.492 and p = 0.028.

Conclusion

CMR has comparative results to echocardiography in assessment of diastolic dysfunction. We found a significant correlation between the degree of diastolic dysfunction and the extent of myocardial scarring.     

One-stop measurement of iron deposition in the anterior pituitary, liver, and heart in thalassemia patients

PURPOSE: To assess the feasibility of one-stop evaluation of iron load of myocardium, liver, and anterior pituitary gland in thalassemia patients. MATERIALS AND METHODS: Fifty thalassemia major patients underwent a breath-hold magnetic resonance imaging (MRI) sequence for assessment of T2* for liver and myocardium, a short axis cine trueFISP sequence covering base to apex to assess the ejection fraction of left ventricle, and a turbo spin echo T2-weighted sequence for the anterior pituitary gland. The MRI parameters were correlated with serum growth hormone, insulin growth factor-1 (IGF-1), insulin growth factor binding protein-3 (IGFBP-3), and endocrine failure. RESULTS: Ferritin was found to be associated with T2* liver (P < 0.005), T2SI (signal intensity) pituitary (P = 0.001), and T2 pituitary/fat (P = 0.001), but not with T2* heart. There was significant correlation of T2SI pituitary with IGF-1 and IGFBP-3. T2* liver (P < 0.001), T2* heart (P < 0.001), pituitary SI (P < 0.001) and pituitary/fat SI (P = 0.002) were also found to be significantly correlated with a history of hypogonadism. T2* heart was also found to be significantly correlated with IGF-1. CONCLUSION: A quick MRI protocol for assessment of T2* liver, T2* heart, and T2SI pituitary is technically feasible. This might form an objective basis to monitor the response to different organs to chelation therapy.     

Myocardial T2* is not affected by ageing, myocardial fibrosis, or impaired left ventricular function

Purpose

To evaluate the influence of alterations in myocardial structure and function from increasing age, myocardial fibrosis, or impaired left ventricular function on myocardial T2*.

Materials and Methods

Myocardial T2* was measured in 126 subjects without cardiac iron loading, of whom 63 were normals of varying ages, 39 were patients with impaired left ventricular function from various nonsiderotic cardiac causes, and 24 were patients with chronic myocardial infarction affecting the interventricular septum (where myocardial T2* measurements are normally made).

Results

The median (Q1, Q3) of myocardial T2* in the normals was 36.3 ms (31.6, 45.4). There was no significant correlation between myocardial T2* and age (R² = 0.04; P = 0.11). In the patients with impaired left ventricular function, the median myocardial T2* was 35.5 ms (31, 42.2) (P = 0.34 versus normals). There was no significant correlation between ejection fraction and T2* in patients with left ventricular impairment (R² = 0.03; P = 0.33). In the patients with septal infarction, the median septal myocardial T2* was 35.4 ms (32.7, 43) (P = 0.81 vs normals).

Conclusion

There was no significant change in myocardial T2* associated with any alterations of myocardial structure and function occurring with increasing age, impairment of left ventricular function or septal fibrosis from chronic myocardial infarction. These results indicate that myocardial T2* measurements are robust to these potential confounding parameters. J. Magn. Reson. Imaging 2010;32:1095–1098. © 2010 Wiley‐Liss, Inc.     

Quantitative analysis of regional left ventricular function after myocardial infarction in the pig assessed with cine magnetic resonance imaging

To assess the accuracy of quantitative analysis of global and regional wall motion and wall thickening of the left ventricle with cine magnetic resonance (MR), images obtained in eight pigs before and after myocardial infarction were compared with those obtained using gadolinium diethylenetriaminepen-taacetic acid (Gd-DTPA)-enhanced multislice spin-echo MR imaging and determination of pathology. The region with abnormal wall motion and wall thickening, as determined with cine MR imaging, identified the same region of infarction as indicated by Gd-DTPA-enhanced spin-echo MR imaging and pathology. Within the infarcted region wall motion and wall thickening analyzed with the centerline method were significantly reduced. We conclude that the use of quantitative analysis of cine MR images accurately determines localization and extent of regional left ventricular dysfunction in the infarcted heart in vivo. This analysis using dedicated software including the centerline method allows sequential assessment of regional left ventricular function in normal and infarcted hearts.     

Monitoring left ventricular function in small animals

Small animals such as mice and rats are extensively used to investigate the mechanisms and treatment of human cardiac diseases in vivo. The monitoring of left ventricular function is a key factor in this research. The measurement should be rapid, reproducible, and repeatable and allow the detection of subtle differences in function. Currently, echocardiography is most widely used in cardiac research laboratories for measuring left ventricular dimensions and function in small animals. Although the technique is rapid, the reproducibility of the calculations of left ventricular volumes is limited in some circumstances as a result of assumptions that do not necessarily hold true, such as in the setting of dilated, failing ventricles.     

MR study of postnatal development of myocardial structure and left ventricular function

Purpose

To investigate postnatal development of left ventricular (LV) cardiac function and myocardium structure.

Materials and Methods

In vivo cardiac MR and ex vivo diffusion tensor imaging (DTI) were performed in normal Sprague‐Dawley rats at postnatal day 2, 4, 7, 14, 21, 28, and 56 (N = 6 per group).

Results

Morphologically, LV size increased with age. Functionally, stroke volume and cardiac output increased. Heart rate increased gradually and became stable after day 14. On average, ejection fraction increased within the first 4 days, decreased at day 7, gradually increased until day 21, and became stable afterward. Structurally, double‐helical myocardial structure was found as early as day 2. Myocardial fiber parameters, described by fractional anisotropy, mean apparent diffusion coefficient, and axial diffusivity, increased within the first 4 days. Then radial diffusivity increased until day 7 while other parameters decreased up to day 56.

Conclusion

Postnatal heart development was documented by MRI. DTI findings are in agreement with the two known stages of early postnatal growth: hyperplasia and hypertrophy. These results can serve as the baselines for study of postnatal heart developmental abnormalities. They also demonstrate the ability of DTI to reveal microstructural alterations in myocardium. J. Magn. Reson. Imaging 2009;30:47–53. © 2009 Wiley‐Liss, Inc.     

Interscanner reproducibility of cardiovascular magnetic resonance T2* measurements of tissue iron in thalassemia

PURPOSE: To assess interscanner reproducibility of tissue iron measurements in patients with thalassemia using gradient echo T2* measurements on two different MRI scanners. MATERIALS AND METHODS: Twenty-five patients with thalassemia major had liver and myocardial T2* assessment using a Picker Edge 1.5T Scanner and a Siemens Sonata 1.5T scanner, with similar gradient echo sequences. In a subset of 13 patients, two scans on the Siemens scanner were performed to assess interstudy reproducibility. RESULTS: There was a highly significant, linear correlation between T2* values obtained for both the heart (r = 0.95) and the liver (r = 0.99) between scanners. The mean difference, coefficient of variability, and 95% confidence intervals between scanners were 0.8 msec, 9.4% and -5.0 to 6.7 msec for the heart; and 0.9 msec, 7.9% and -2.0 to 3.9 msec for the liver. The interstudy mean difference and coefficient of variability on the Siemens scanner was 0.3 msec and 4.8% (r = 0.99) for the heart, and 0.04 msec and 1.9% (r = 0.99) for the liver. CONCLUSION: The T2* technique for measuring tissue iron is reproducible between the two manufacturers' scanners. This suggests that the widespread implementation of the technique is possible for clinical assessment of myocardial iron loading in thalassemia.     

Stress-related variations in left ventricular function as assessed with gated myocardial perfusion SPECT

BACKGROUND: There is inconsistency in reported patient characteristics associated with differences in basal and poststress left ventricular function (delta ejection fraction [DeltaEF]) assessed by gated single photon emission computed tomography (SPECT). This inconsistency may therefore hamper adequate interpretation. In this study we first determined the reproducibility of serial gated SPECT-assessed left ventricular function. Second, we determined whether left ventricular ejection fraction (LVEF) assessed directly after stress reflects basal LVEF and, if not, what patient characteristics were associated with this discrepancy in LVEF. METHODS AND RESULTS: Serial reproducibility of technetium 99m tetrofosmin gated SPECT-assessed LVEF in 22 patients showed a mean difference between two sequential measurements at rest of 0.09% EF units, with a 95% limit of agreement (2 SDs) at 5.8% EF units. In 229 patients Tc-99m tetrofosmin gated SPECT was performed after stress and at rest. Independent predictors of DeltaEF were the presence of scintigraphically proven ischemia (standardized coefficient, -1.256; P =.003) and difference in heart rate at the time of acquisition (standardized coefficient, 0.121; P =.001). CONCLUSIONS: Gated SPECT-assessed LVEF at rest is reproducible under standard clinical conditions. However, LVEF assessed after stress does not represent LVEF at rest in patients with scintigraphically proven ischemia and in patients with increased heart rate after stress compared with heart rate at rest.     

组织多普勒成像技术评价冠心病心肌梗死后左室整体功能

 目的 应用超声心动图对冠心病心肌梗死患者进行检测,寻找与左室功能相关性良好的指标以利于临床评估.方法 对经临床及冠状动脉造影确诊的心肌梗死(1～6个月)患者68例行多普勒超声心动图检查.根据其二尖瓣口血流频谱形态将患者分为3组:左室松弛性减低组、假性正常化组、限制性充盈组;又根据心脏射血分数(ejection fraction,EF)值将患者分为两组:EF≥50％,EF＜ 50％,将各多普勒超声心动图参数在各组对比分析.结果 随着心脏舒张功能障碍的进展,运用组织多普勒技术(TDI)测得的二尖瓣环舒张早期峰值速度(Ea)及其与舒张晚期峰值速度(Aa)的比值Ea/Aa降低(P＜0.01),其差别尤其表现在对照组与左室松弛性减低组及其与假性正常化组之间(P＜0.01).在正常对照组、冠心病心肌梗死EF正常组及冠心病心肌梗死EF减低组TDI测得的二尖瓣环收缩期峰值速度Sa、Ea及Ea/Aa比值呈逐渐降低趋势(P＜0.01).而且Spearman相关分析表明:Ea值及Ea/Aa比值与左室舒张功能障碍分级相关性良好,Sa与EF值相关性良好.结论 冠心病心肌梗死患者出现左室舒张功能障碍常先于左室收缩功能障碍,TDI测得的Ea及Ea/Aa比值可用于鉴别左室舒张功能的假性正常化;TD1测得的Sa可作为评估冠心病心肌梗死患者左室收缩功能的重要参数.     

Impact of magnetic resonance imaging on cardiac mortality in thalassemia major

Purpose:

To evaluate whether the introduction of magnetic resonance imaging (MRI) in the management of thalassemia major (TM) patients has affected the risk of cardiac death.

Materials and Methods:

In all, 804 TM patients from two large reference units were included and the risk of dying of cardiac causes, before and after their first MRI, was assessed by a Cox proportional hazards model with time‐dependent covariates.

Results:

Adding information from MRI reduced the risk of cardiac death from 6.0 deaths/1000 patient‐years to 3.9 deaths/1000 patient‐years (P = 0.22). The risk of cardiac death before having an MRI study was 82% higher compared to the risk observed after the first MRI.

Conclusion:

MRI has become a vital component of ongoing management and seems to have a beneficial effect on cardiac mortality in TM. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.