Quantification of late gadolinium enhanced CMR in viability assessment in chronic ischemic heart disease: a comparison to functional outcome

Impact of late gadolinium enhancement image acquisition resolution on neural network based automatic scar segmentation

BACKGROUND

Automatic myocardial scar segmentation from late gadolinium enhancement (LGE) images using neural networks promises an alternative to time-consuming and observer-dependent semi-automatic approaches. However, alterations in data acquisition, reconstruction as well as post-processing may compromise network performance. The objective of the present work was to systematically assess network performance degradation due to a mismatch of point-spread function between training and testing data.

METHODS

Thirty-six high-resolution (0.7×0.7×2.0 mm3) LGE k-space datasets were acquired post-mortem in porcine models of myocardial infarction. The in-plane point-spread function and hence in-plane resolution Δx was retrospectively degraded using k-space lowpass filtering, while field-of-view and matrix size were kept constant. Manual segmentation of the left ventricle (LV) and healthy remote myocardium was performed to quantify location and area (% of myocardium) of scar by thresholding (≥ SD5 above remote). Three standard U-Nets were trained on training resolutions Δxtrain = 0.7, 1.2 and 1.7 mm to predict endo- and epicardial borders of LV myocardium and scar. The scar prediction of the three networks for varying test resolutions (Δxtest = 0.7 to 1.7 mm) was compared against the reference SD5 thresholding at 0.7 mm. Finally, a fourth network trained on a combination of resolutions (Δxtrain = 0.7 to 1.7 mm) was tested.

RESULTS

The prediction of relative scar areas showed the highest precision when the resolution of the test data was identical to or close to the resolution used during training. The median fractional scar errors and precisions (IQR) from networks trained and tested on the same resolution were 0.0 percentage points (p.p.) (1.24 - 1.45), and - 0.5 - 0.0 p.p. (2.00 - 3.25) for networks trained and tested on the most differing resolutions, respectively. Deploying the network trained on multiple resolutions resulted in reduced resolution dependency with median scar errors and IQRs of 0.0 p.p. (1.24 - 1.69) for all investigated test resolutions.

CONCLUSION

A mismatch of the imaging point-spread function between training and test data can lead to degradation of scar segmentation when using current U-Net architectures as demonstrated on LGE porcine myocardial infarction data. Training networks on multi-resolution data can alleviate the resolution dependency.

Zinc supplementation in patients with acute myocardial infarction

This single-centre prospective feasibility study (UMIN000030232) evaluated whether zinc supplementation was safe and effective for improving outcomes among patients with acute myocardial infarction (AMI). Within 24 h after successful primary percutaneous coronary intervention, consenting patients with AMI were randomly assigned 1:1 to receive conventional treatment (conventional treatment group) or conventional treatment plus zinc acetate supplementation (zinc supplementation group). The two groups were compared in terms of major adverse cardiovascular events (MACE), and scar size, which was evaluated using cardiac magnetic resonance imaging (CMR) at 4 weeks after discharge. A total of 56 patients underwent randomization (with 26 assigned to the zinc supplementation group and 27 to the conventional treatment group). The two groups had generally similar laboratory findings and clinical characteristics. The two groups also had similar lengths of hospital stay and rates of MACE. Forty of the 53 patients underwent CMR and it revealed that % core zone was numerically lower in the zinc supplementation group than in the conventional treatment group (9.3 ± 6.9% vs. 14.2 ± 9.1%, P = 0.07). This small single-centre study failed to detect a significant reduction in mid-term MACE after AMI among patients who received zinc supplementation.

Isotropic 3D compressed sensing (CS) based sequence is comparable to 2D-LGE in left ventricular scar quantification in different disease entities

The goal of this study was to evaluate a three-dimensional compressed sensing (3D-CS) LGE prototype sequence for the detection and quantification of myocardial fibrosis in patients with chronic myocardial infarction (CMI) and myocarditis (MYC) compared with a 2D-LGE standard. Patients with left-ventricular LGE due to CMI (n = 33) or MYC (n = 20) were prospectively recruited. 2D-LGE and 3D-CS images were acquired in random order at 1.5 Tesla. 3D-CS short axis (SAX) images were reconstructed corresponding to 2D SAX images. LGE was quantitatively assessed on patient and segment level using semi-automated threshold methods. Image quality (4-point scoring system), Contrast-ratio (CR) and acquisition times were compared. There was no significant difference between 2D and 3D sequences regarding global LGE (%) (CMI [2D-LGE: 11.4 ± 7.5; 3D-LGE: 11.5 ± 8.5; p = 0.99]; MYC [2D-LGE: 27.0 ± 15.7; 3D-LGE: 26.2 ± 13.1; p = 0.70]) and segmental LGE-extent (p = 0.63). 3D-CS identified papillary infarction in 5 cases which was not present in 2D images. 2D-LGE acquisition time was shorter (2D: median: 06:59 min [IQR: 05:51-08:18]; 3D: 14:48 min [12:45-16:57]). 3D-CS obtained better quality scores (2D: 2.06 ± 0.56 vs. 3D: 2.29 ± 0.61). CR did not differ (p = 0.63) between basal and apical regions in 3D-CS images but decreased significantly in 2D apical images (CR basal: 2D: 0.77 ± 0.11, 3D: 0.59 ± 0.10; CR apical: 2D: 0.64 ± 0.17, 3D: 0.53 ± 0.11). 3D-LGE shows high congruency with standard LGE and allows better identification of small lesions. However, the current 3D-CS LGE sequence did not provide PSIR reconstruction and acquisition time was longer.

Extracellular volume-guided late gadolinium enhancement analysis for non-ischemic cardiomyopathy: The Women's Interagency HIV Study

BACKGROUND

Quantification of non-ischemic myocardial scar remains a challenge due to the patchy diffuse nature of fibrosis. Extracellular volume (ECV) to guide late gadolinium enhancement (LGE) analysis may achieve a robust scar assessment.

METHODS

Three cohorts of 80 non-ischemic-training, 20 non-ischemic-validation, and 10 ischemic-validation were prospectively enrolled and underwent 3.0 Tesla cardiac MRI. An ECV cutoff to differentiate LGE scar from non-scar was identified in the training cohort from the receiver-operating characteristic curve analysis, by comparing the ECV value against the visually-determined presence/absence of the LGE scar at the highest signal intensity (SI) area of the mid-left ventricle (LV) LGE. Based on the ECV cutoff, an LGE semi-automatic threshold of n-times of standard-deviation (n-SD) above the remote-myocardium SI was optimized in the individual cases ensuring correspondence between LGE and ECV images. The inter-method agreement of scar amount in comparison with manual (for non-ischemic) or full-width half-maximum (FWHM, for ischemic) was assessed. Intra- and inter-observer reproducibility were investigated in a randomly chosen subset of 40 non-ischemic and 10 ischemic cases.

RESULTS

The non-ischemic groups were all female with the HIV positive rate of 73.8% (training) and 80% (validation). The ischemic group was all male with reduced LV function. An ECV cutoff of 31.5% achieved optimum performance (sensitivity: 90%, specificity: 86.7% in training; sensitivity: 100%, specificity: 81.8% in validation dataset). The identified n-SD threshold varied widely (range 3 SD-18 SD), and was independent of scar amount (β = -0.01, p = 0.92). In the non-ischemic cohorts, results suggested that the manual LGE assessment overestimated scar (%) in comparison to ECV-guided analysis [training: 4.5 (3.2-6.4) vs. 0.92 (0.1-2.1); validation: 2.5 (1.2-3.7) vs. 0.2 (0-1.6); P < 0.01 for both]. Intra- and inter-observer analyses of global scar (%) showed higher reproducibility in ECV-guided than manual analysis with CCC = 0.94 and 0.78 versus CCC = 0.86 and 0.73, respectively (P < 0.01 for all). In ischemic validation, the ECV-guided LGE analysis showed a comparable scar amount and reproducibility with the FWHM.

CONCLUSIONS

ECV-guided LGE analysis is a robust scar quantification method for a non-ischemic cohort. Trial registration ClinicalTrials.gov; NCT00000797, retrospectively-registered 2 November 1999; NCT02501811, registered 15 July 2015.

Improvement of late gadolinium enhancement image quality using a deep learning-based reconstruction algorithm and its influence on myocardial scar quantification

OBJECTIVES

The aim of this study was to assess the effect of a deep learning (DL)-based reconstruction algorithm on late gadolinium enhancement (LGE) image quality and to evaluate its influence on scar quantification.

METHODS

Sixty patients (46 ± 17 years, 50% male) with suspected or known cardiomyopathy underwent CMR. Short-axis LGE images were reconstructed using the conventional reconstruction and a DL network (DLRecon) with tunable noise reduction (NR) levels from 0 to 100%. Image quality of standard LGE images and DLRecon images with 75% NR was scored using a 5-point scale (poor to excellent). In 30 patients with LGE, scar size was quantified using thresholding techniques with different standard deviations (SD) above remote myocardium, and using full width at half maximum (FWHM) technique in images with varying NR levels.

RESULTS

DLRecon images were of higher quality than standard LGE images (subjective quality score 3.3 ± 0.5 vs. 3.6 ± 0.7, p < 0.001). Scar size increased with increasing NR levels using the SD methods. With 100% NR level, scar size increased 36%, 87%, and 138% using 2SD, 4SD, and 6SD quantification method, respectively, compared to standard LGE images (all p values < 0.001). However, with the FWHM method, no differences in scar size were found (p = 0.06).

CONCLUSIONS

LGE image quality improved significantly using a DL-based reconstruction algorithm. However, this algorithm has an important impact on scar quantification depending on which quantification technique is used. The FWHM method is preferred because of its independency of NR. Clinicians should be aware of this impact on scar quantification, as DL-based reconstruction algorithms are being used.

KEY POINTS

• The image quality based on (subjective) visual assessment and image sharpness of late gadolinium enhancement images improved significantly using a deep learning-based reconstruction algorithm that aims to reconstruct high signal-to-noise images using a denoising technique. • Special care should be taken when scar size is quantified using thresholding techniques with different standard deviations above remote myocardium because of the large impact of these advanced image enhancement algorithms. • The full width at half maximum method is recommended to quantify scar size when deep learning algorithms based on noise reduction are used, as this method is the least sensitive to the level of noise and showed the best agreement with visual late gadolinium enhancement assessment.

Quantification of late gadolinium enhancement cardiovascular MRI in patients with coronary artery chronic total occlusion

AIM

To determine the most accurate and reproducible semi-automated greyscale thresholding technique for quantifying late gadolinium enhancement (LGE) in cardiovascular magnetic resonance imaging (CMRI), by using positron-emission tomography (PET) as the reference standard in patients with coronary artery chronic total occlusion (CTO).

MATERIALS AND METHODS

LGE in CMRI, single-photon-emission computed tomography (SPECT), and PET were performed within 1 week in each of 63 patients with known CTO. The presence and quantity of LGE were determined with greyscale thresholds of 2, 4, 5, 6, and 8 standard deviations (SDs) above the mean signal intensity for normal remote myocardium and full width at half maximum (FWHM). The infarcted myocardium was delineated by PET.

RESULTS

Sixty-three patients and 1,008 segments were analysed. Based on patient analysis, with PET as the reference standard, the 5 SD method yielded the strongest correlation (r=0.85, p<0.0001) compared with the 2 SDs (r=0.42), 4 SDs (r=0.73), 6 SDs (r=0.81), 8 SDs (r=0.71), and FWHM (r=0.69; p<0.001 for all comparisons). The 5 SDs threshold quantification showed high interobserver and intra-observer agreement (intraclass correlation coefficient [ICC]=0.90, p<0.0001; ICC=0.93, p<0.0001, respectively).

CONCLUSIONS

Semi-automated LGE CMRI greyscale thresholding with 5 SDs above the mean signal intensity for normal remote myocardium yields the strongest correlation to the extent of LGE identified using PET and is highly reproducible in patients with CTO.

Oxygen-sensitive T2* magnetic resonance imaging to correlate heart function and ischemic etiology of post-hospitalized chronic heart failure patients

PURPOSE

Myocardial oxygenation imaging is a field-of-interest but its clinical utility largely unexplored. We aimed to investigate the myocardial oxygenation status via T2* imaging and compared with the left ventricular ejection fraction (LVEF) in chronic heart failure (HF) patients after hospitalization. Also, we sought to compare the differences in myocardial oxygenation status among patients with ischemic HF, non-ischemic HF and controls.

METHODS

We prospectively enrolled 60 participants, comprising 20 HF patients with LVEF ≥ 50 % as the improved ejection fraction (HFIEF) group, 20 H F patients with ejection fraction <50 % as the reduced ejection fraction (HFREF) group, and 20 controls. Patients were also dichotomized into ischemic and non-ischemic subgroups. T2* values were compared across the study groups, and correlated with LVEF, myocardial scar distribution and quantity.

RESULTS

T2* values positively correlated with LVEF and were significantly lower in the HFREF group as compared with both HFIEF and controls (20.06 vs. 24.23; 20.06 vs. 26.32, respectively, both p < 0.05). Lower T2* values were observed in the HFREF group than the HFIEF group and the ischemic subgroup than the non-ischemic subgroup. No significant correlation existed between T2* value and the myocardial scar amounts in ischemic territory.

CONCLUSIONS

Oxygen-sensitive T2* measurements showed correlation with LVEF and ischemic etiology in chronic heart failure patients, while the ischemic HFREF patients appeared to be more vulnerable to myocardial oxygen reduction than other groups. T2* measurements may be clinically feasible in monitoring heart failure via myocardial oxygenation and lay the foundation for future studies in prediction heart failure recovery.

Comparison of myocardial fibrosis quantification methods by cardiovascular magnetic resonance imaging for risk stratification of patients with suspected myocarditis

BACKGROUND

Although the presence of late gadolinium enhancement (LGE) using cardiovascular magnetic resonance imaging (CMR) is a significant discriminator of events in patients with suspected myocarditis, no data are available on the optimal LGE quantification method.

METHODS

Six hundred seventy consecutive patients (48 ± 16 years, 59% male) with suspected myocarditis were enrolled between 2002 and 2015. We performed LGE quantitation using seven different signal intensity thresholding methods based either on 2, 3, 4, 5, 6, 7 standard deviations (SD) above remote myocardium or full width at half maximum (FWHM). In addition, a LGE visual presence score (LGE-VPS) (LGE present/absent in each segment) was assessed. For each of these methods, the strength of association of LGE results with major adverse cardiac events (MACE) was determined. Inter-and intra-rater variability using intraclass-correlation coefficient (ICC) was performed for all methods.

RESULTS

Ninety-eight (15%) patients experienced a MACE at a medium follow-up of 4.7 years. LGE quantification by FWHM, 2- and 3-SD demonstrated univariable association with MACE (hazard ratio [HR] 1.05, 95% confidence interval [CI]:1.02-1.08, p = 0.001; HR 1.02, 95%CI:1.00-1.04; p = 0.001; HR 1.02, 95%CI: 1.00-1.05, p = 0.035, respectively), whereas 4-SD through 7-SD methods did not reach significant association. LGE-VPS also demonstrated association with MACE (HR 1.09, 95%CI: 1.04-1.15, p < 0.001). In the multivariable model, FWHM, 2-SD methods, and LGE-VPS each demonstrated significant association with MACE adjusted to age, sex, BMI and LVEF (adjusted HR of 1.04, 1.02, and 1.07; p = 0.009, p = 0.035; and p = 0.005, respectively). In these, FWHM and LGE-VPS had the highest degrees of inter and intra-rater reproducibility based on their high ICC values.

CONCLUSIONS

FWHM is the optimal semi-automated quantification method in risk-stratifying patients with suspected myocarditis, demonstrating the strongest association with MACE and the highest technical consistency. Visual LGE scoring is a reliable alternative method and is associated with a comparable association with MACE and reproducibility in these patients.

TRIAL REGISTRATION NUMBER

NCT03470571 . Registered 13th March 2018. Retrospectively registered.

Cardiovascular magnetic resonance evidence of myocardial fibrosis and its clinical significance in adolescent and adult patients with Ebstein's anomaly

BACKGROUND

Myocardial fibrosis is a common pathophysiological process that is related to ventricular remodeling in congenital heart disease. However, the presence, characteristics, and clinical significance of myocardial fibrosis in Ebstein's anomaly have not been fully investigated. This study aimed to evaluate myocardial fibrosis using cardiovascular magnetic resonance (CMR) late gadolinium enhancement (LGE) and T1 mapping techniques, and to explore the significance of myocardial fibrosis in adolescent and adult patients with Ebstein's anomaly.

METHODS

Forty-four consecutive patients with unrepaired Ebstein's anomaly (34.0 ± 16.2 years; 18 males), and an equal number of age- and gender-matched controls, were included. A comprehensive CMR protocol consisted of cine, LGE, and T1 mapping by modified Look-Locker inversion recovery (MOLLI) sequences were performed. Ventricular functional parameters, native T1, extracellular volume (ECV), and LGE were analyzed. Associations between myocardial fibrosis and disease severity, ventricular function, and NYHA classification were analyzed.

RESULTS

LGE was found in 10 (22.7%) patients. Typical LGE in Ebstein's anomaly was located in the endocardium of the septum within the right ventricle (RV). The LV ECV of Ebstein's anomaly were significantly higher than those of the controls (30.0 ± 3.8% vs. 25.3 ± 2.3%, P < 0.001). An increased ECV was found to be independent of the existence of LGE. Positive LGE or higher ECV (≥30%) was associated with larger fRV volume, aRV volume, increased disease severity, and worse NYHA functional class. In addition, ECV was significantly correlated with the LV ejection fraction (P <  0.001).

CONCLUSIONS

Both focal and diffuse myocardial fibrosis were observed in adolescent and adult patients with Ebstein's anomaly. Increased diffuse fibrosis is associated with worse LV function, increased Ebstein's severity, and worse clinical status.

Defining myocardial fibrosis in haemodialysis patients with non-contrast cardiac magnetic resonance

Background

Extent of myocardial fibrosis (MF) determined using late gadolinium enhanced (LGE) predicts outcomes, but gadolinium is contraindicated in advanced renal disease. We assessed the ability of native T1-mapping to identify and quantify MF in aortic stenosis patients (AS) as a model for use in haemodialysis patients.

Methods

We compared the ability to identify areas of replacement-MF using native T1-mapping to LGE in 25 AS patients at 3 T. We assessed agreement between extent of MF defined by LGE full-width-half-maximum (FWHM) and the LGE 3-standard-deviations (3SD) in AS patients and nine T1 thresholding-techniques, with thresholds set 2-to-9 standard-deviations above normal-range (1083 ± 33 ms). A further technique was tested that set an individual T1-threshold for each patient (T11SD). The technique that agreed most strongly with FWHM or 3SD in AS patients was used to compare extent of MF between AS (n = 25) and haemodialysis patients (n = 25).

Results

Twenty-six areas of enhancement were identified on LGE images, with 25 corresponding areas of discretely increased native T1 signal identified on T1 maps. Global T1 was higher in haemodialysis than AS patients (1279 ms ± 5.8 vs 1143 ms ± 12.49, P < 0.01). No signal-threshold technique derived from standard-deviations above normal-range associated with FWHM or 3SD. T11SD correlated with FWHM in AS patients (r = 0.55) with moderate agreement (ICC = 0.64), (but not with 3SD). Extent of MF defined by T11SD was higher in haemodialysis vs AS patients (21.92% ± 1 vs 18.24% ± 1.4, P = 0.038), as was T1 in regions-of-interest defined as scar (1390 ± 8.7 vs 1276 ms ± 20.5, P < 0.01). There was no difference in the relative difference between remote myocardium and regions defined as scar, between groups (111.4 ms ± 7.6 vs 133.2 ms ± 17.5, P = 0.26).

Conclusions

Areas of MF are identifiable on native T1 maps, but absolute thresholds to define extent of MF could not be determined. Histological studies are needed to assess the ability of native-T1 signal-thresholding techniques to define extent of MF in haemodialysis patients.

Data is taken from the PRIMID-AS (NCT01658345) and CYCLE-HD studies (ISRCTN11299707).

Comparison of Magnetic Resonance Analysis of Myocardial Scarring With Biomarker Release Following S-T Elevation Myocardial Infarction

BACKGROUND

Late gadolinium enhancement (LGE) with cardiac magnetic resonance (CMR) is commonly assumed to represent myocardial fibrosis; however, comparative human histological data are limited, and there is no consensus on the most accurate method for LGE quantitation. We evaluated the relationship between CMR assessment of regional fibrosis and infarct size assessment using serial biomarkers after ST elevation acute myocardial infarction (STEMI).

METHODS

Ninety-three patients treated for STEMI (59±10 years, 86% male) underwent CMR 6 months after infarction. Infarct size was quantified by CMR-LGE using manual and range of semi-automated thresholds (range: 2-10 standard deviations [SD]) above reference myocardium and the full width-half maximum (FWHM) technique, and compared with the rise in serum biomarkers. The agreement between CMR and biomarker in the identification of large infarcts based on peak troponin (TnI) levels was also analysed.

RESULTS

Quantification methods had a strong influence on the infarct size assessment with CMR-LGE. Significant correlations were observed between LGE and biomarkers across all of the signal intensity thresholds. Whilst there was a wide variation with respect to the estimation of total LGE size (from 6.8±7.7 to 32.1±11.3 grams), the variation in the correlation with peak troponin level was much smaller (r-values ranging from 0.670 to 0.876). There was good agreement between CMR-LGE and biomarker assessment of infarct size; the best agreement between CMR-LGE and large infarction using a threshold of 8SD for peak TnI>50ng/mL (Cohen's kappa (κ)=0.722), and a threshold of 4SD for peak TnI >95ng/mL (κ=0.761).

CONCLUSIONS

The correlation between CMR-LGE quantification of infarct size and biomarker release following STEMI at a range of semi-automated thresholds was consistently strong, with good agreement between measures across a range of thresholds.

Ineffective and prolonged apical contraction is associated with chest pain and ischaemia in apical hypertrophic cardiomyopathy

OBJECTIVES

To investigate the hypothesis that persistence of apical contraction into diastole is linked to reduced myocardial perfusion and chest pain.

BACKGROUND

Apical hypertrophic cardiomyopathy (HCM) is defined by left ventricular (LV) hypertrophy predominantly of the apex. Hyperdynamic contractility resulting in obliteration of the apical cavity is often present. Apical HCM can lead to drug-refractory chest pain.

METHODS

We retrospectively studied 126 subjects; 76 with apical HCM and 50 controls (31 with asymmetrical septal hypertrophy (ASH) and 19 with non-cardiac chest pain and culprit free angiograms and structurally normal hearts). Perfusion cardiac magnetic resonance imaging (CMR) scans were assessed for myocardial perfusion reserve index (MPRi), late gadolinium enhancement (LGE), LV volumes (muscle and cavity) and regional contractile persistence (apex, mid and basal LV).

RESULTS

In apical HCM, apical MPRi was lower than in normal and ASH controls (p<0.05). In apical HCM, duration of contractile persistence was associated with lower MPRi (p<0.01) and chest pain (p<0.05). In multivariate regression, contractile persistence was independently associated with chest pain (p<0.01) and reduced MPRi (p<0.001).

CONCLUSION

In apical HCM, regional contractile persistence is associated with impaired myocardial perfusion and chest pain. As apical myocardium makes limited contributions to stroke volume, apical contractility is also largely ineffective. Interventions to reduce apical contraction and/or muscle mass are potential therapies for improving symptoms without reducing cardiac output.

A systematic comparison of cardiovascular magnetic resonance and high resolution histological fibrosis quantification in a chronic porcine infarct model

The noninvasive reference standard for myocardial fibrosis detection on cardiovascular magnetic resonance imaging (CMR) is late gadolinium enhancement (LGE). Currently there is no consensus on the preferred method for LGE quantification. Moreover myocardial wall thickening (WT) and strain are measures of regional deformation and function. The aim of this research was to systematically compare in vivo CMR parameters, such as LGE, WT and strain, with histological fibrosis quantification. Eight weeks after 90 min ischemia/reperfusion of the LAD artery, 16 pigs underwent in vivo Cine and LGE CMR. Histological sections from transverse heart slices were digitally analysed for fibrosis quantification. Mean fibrosis percentage of analysed sections was related to the different CMR techniques (using segmentation or feature tracking software) for each slice using a linear mixed model analysis. The full width at half maximum (FWHM) technique for quantification of LGE yielded the highest R2 of 60%. Cine derived myocardial WT explained 16-36% of the histological myocardial fibrosis. The peak circumferential and radial strain measured by feature tracking could explain 15 and 10% of the variance of myocardial fibrosis, respectively. The used method to systematically compare CMR image data with digital histological images is novel and feasible. Myocardial WT and strain were only modestly related with the amount of fibrosis. The fully automatic FWHM analysis technique is the preferred method to detect myocardial fibrosis.

Myocardial Infarct Size by CMR in Clinical Cardioprotection Studies: Insights From Randomized Controlled Trials

OBJECTIVES

The aim of this study was to review randomized controlled trials (RCTs) using cardiac magnetic resonance (CMR) to assess myocardial infarct (MI) size in reperfused patients with ST-segment elevation myocardial infarction (STEMI).

BACKGROUND

There is limited guidance on the use of CMR in clinical cardioprotection RCTs in patients with STEMI treated by primary percutaneous coronary intervention.

METHODS

All RCTs in which CMR was used to quantify MI size in patients with STEMI treated with primary percutaneous coronary intervention were identified and reviewed.

RESULTS

Sixty-two RCTs (10,570 patients, January 2006 to November 2016) were included. One-third did not report CMR vendor or scanner strength, the contrast agent and dose used, and the MI size quantification technique. Gadopentetate dimeglumine was most commonly used, followed by gadoterate meglumine and gadobutrol at 0.20 mmol/kg each, with late gadolinium enhancement acquired at 10 min; in most RCTs, MI size was quantified manually, followed by the 5 standard deviation threshold; dropout rates were 9% for acute CMR only and 16% for paired acute and follow-up scans. Weighted mean acute and chronic MI sizes (≤12 h, initial TIMI [Thrombolysis in Myocardial Infarction] flow grade 0 to 3) from the control arms were 21 ± 14% and 15 ± 11% of the left ventricle, respectively, and could be used for future sample-size calculations. Pre-selecting patients most likely to benefit from the cardioprotective therapy (≤6 h, initial TIMI flow grade 0 or 1) reduced sample size by one-third. Other suggested recommendations for standardizing CMR in future RCTs included gadobutrol at 0.15 mmol/kg with late gadolinium enhancement at 15 min, manual or 6-SD threshold for MI quantification, performing acute CMR at 3 to 5 days and follow-up CMR at 6 months, and adequate reporting of the acquisition and analysis of CMR.

CONCLUSIONS

There is significant heterogeneity in RCT design using CMR in patients with STEMI. The authors provide recommendations for standardizing the assessment of MI size using CMR in future clinical cardioprotection RCTs.

Myocardial Extracellular Volume Estimation by CMR Predicts Functional Recovery Following Acute MI

OBJECTIVES

In the setting of reperfused acute myocardial infarction (AMI), the authors sought to compare prediction of contractile recovery by infarct extracellular volume (ECV), as measured by T1-mapping cardiac magnetic resonance (CMR), with late gadolinium enhancement (LGE) transmural extent.

BACKGROUND

The transmural extent of myocardial infarction as assessed by LGE CMR is a strong predictor of functional recovery, but accuracy of the technique may be reduced in AMI. ECV mapping by CMR can provide a continuous measure associated with the severity of tissue damage within infarcted myocardium.

METHODS

Thirty-nine patients underwent acute (day 2) and convalescent (3 months) CMR scans following AMI. Cine imaging, tissue tagging, T2-weighted imaging, modified Look-Locker inversion T1 mapping natively and 15 min post-gadolinium-contrast administration, and LGE imaging were performed. The ability of acute infarct ECV and acute transmural extent of LGE to predict convalescent wall motion, ejection fraction (EF), and strain were compared per-segment and per-patient.

RESULTS

Per-segment, acute ECV and LGE transmural extent were associated with convalescent wall motion score (p < 0.01; p < 0.01, respectively). ECV had higher accuracy than LGE extent to predict improved wall motion (area under receiver-operating characteristics curve 0.77 vs. 0.66; p = 0.02). Infarct ECV ≤0.5 had sensitivity 81% and specificity 65% for prediction of improvement in segmental function; LGE transmural extent ≤0.5 had sensitivity 61% and specificity 71%. Per-patient, ECV and LGE correlated with convalescent wall motion score (r = 0.45; p < 0.01; r = 0.41; p = 0.02, respectively) and convalescent EF (p < 0.01; p = 0.04). ECV and LGE extent were not significantly correlated (r = 0.34; p = 0.07). In multivariable linear regression analysis, acute infarct ECV was independently associated with convalescent infarct strain and EF (p = 0.03; p = 0.04), whereas LGE was not (p = 0.29; p = 0.24).

CONCLUSIONS

Acute infarct ECV in reperfused AMI can complement LGE assessment as an additional predictor of regional and global LV functional recovery that is independent of transmural extent of infarction.

The clinical utility of new cardiac imaging modalities in Australasian clinical practice

Cardiac imaging is a rapidly evolving field, with improvements in the diagnostic capabilities of non-invasive cardiac assessment. We review the two main emerging technologies in cardiac imaging: computed tomography coronary angiography (CTCA) to evaluate chest symptoms and to exclude coronary artery disease; and cardiovascular magnetic resonance (CMR) for evaluating cardiac morphology, function and presence of scar. CTCA is an excellent "rule out" test, with a negative predictive value approaching 100%. Radiation exposure is no longer a concern for CTCA, with doses routinely < 5 mSv, and as low as < 1 mSv in selected patients. CTCA is useful for excluding coronary artery disease, investigating the anatomy of coronary anomalies or fistulae, and for the patency of coronary bypass grafts. CMR is the reference test for the accurate quantitation of left ventricular and right ventricular size and function. CMR has no ionising radiation, making it particularly suitable for patients with heart failure or congenital heart disease who require longitudinal follow-up. Evaluation of cardiomyopathies (hypertrophic, ischaemic, infiltrative, myocarditis, iron overload or idiopathic) is a unique strength of CMR. Stress perfusion CMR has a strong evidence base and improved spatial and temporal resolution compared with nuclear single-photon emission computed tomography.

Effect of inversion time on the precision of myocardial late gadolinium enhancement quantification evaluated with synthetic inversion recovery MR imaging

OBJECTIVES

To evaluate the influence of inversion time (TI) on the precision of myocardial late gadolinium enhancement (LGE) quantification using synthetic inversion recovery (IR) imaging in patients with myocardial infarction (MI).

METHODS

Fifty-three patients with suspected prior MI underwent 1.5-T cardiac MRI with conventional magnitude (MagIR) and phase-sensitive IR (PSIR) LGE imaging and T1 mapping at 15 min post-contrast. T1-based synthetic MagIR and PSIR images were calculated with a TI ranging from -100 to +150 ms at 5-ms intervals relative to the optimal TI (TI₀). LGE was quantified using a five standard deviation (5SD) and full width at half-maximum (FWHM) thresholds. Measurements were compared using one-way analysis of variance.

RESULTS

The MagIR_sy technique provided precise assessment of LGE area at TIs ≥ TI₀, while precision was decreased below TI₀. The LGE area showed significant differences at ≤ -25 ms compared to TI₀ using 5SD (P < 0.001) and at ≤ -65 ms using the FWHM approach (P < 0.001). LGE measurements did not show significant difference over the analysed TI range in the PSIR_sy images using either of the quantification methods.

CONCLUSIONS

T1 map-based PSIR_sy images provide precise quantification of MI independent of TI at the investigated time point post-contrast. MagIR_sy-based MI quantification is precise at TI₀ and at longer TIs while showing decreased precision at TI values below TI₀.

KEY POINTS

• Synthetic IR imaging retrospectively generates LGE images at any theoretical TI • Synthetic IR imaging can simulate the effect of TI on LGE quantification • Fifteen minutes post-contrast MagIR _sy accurately quantifies infarcts from TI ₀ to TI ₀   + 150 ms • Fifteen minutes post-contrast PSIR _sy provides precise infarct size independent of TI • Synthetic IR imaging has further advantages in reducing operator dependence.

Scar characteristics derived from two- and three-dimensional reconstructions of cardiac contrast-enhanced magnetic resonance images: Relationship to ventricular tachycardia inducibility and ablation success

Background

The relationship between cardiac contrast-enhanced magnetic resonance imaging (CE-MRI)-derived scar characteristics and substrate for ventricular tachycardia (VT) in patients with structural heart disease (SHD) has not been fully investigated.

Methods

This study included 51 patients (mean age, 63.3±15.1 years) who underwent CE-MRI with SHD and VT induction testing before ablation. Late gadolinium-enhanced (LGE) regions on MRI slices were quantified by thresholding techniques. Signal intensities (SIs) 2–6 SDs above the mean SI of the remote left ventricular (LV) myocardium were considered as scar border zones, and SI>6 SDs, as scar zone, and the scar characteristics related to VT inducibility and successful ablation via endocardial approaches were evaluated.

Results

The proportion of the total CE-MRI-derived scar border zone in the inducible VT group was significantly greater than that in the non-inducible VT group (26.3±9.9% vs. 19.2±7.8%, respectively, P=0.0323). The LV endocardial scar zone to total LV myocardial scar zone ratio in patients whose ablation was successful was significantly greater than that in those whose ablation was unsuccessful (0.61±0.11 vs. 0.48±0.12, respectively, P=0.0042). Most successful ablation sites were located adjacent to CE-MRI-derived scar border zones.

Conclusions

By CE-MRI, we were able to characterize not only the scar, but also its location and heterogeneity, and those features seemed to be related to VT inducibility and successful ablation from an endocardial site.

Impact of microvascular obstruction on semiautomated techniques for quantifying acute and chronic myocardial infarction by cardiovascular magnetic resonance

Aims

The four most promising semiautomated techniques (5-SD, 6-SD, Otsu and the full width half maximum (FWHM)) were compared in paired acute and follow-up cardiovascular magnetic resonance (CMR), taking into account the impact of microvascular obstruction (MVO) and using automated extracellular volume fraction (ECV) maps for reference. Furthermore, their performances on the acute scan were compared against manual myocardial infarct (MI) size to predict adverse left ventricular (LV) remodelling (≥20% increase in end-diastolic volume).

Methods

40 patients with reperfused ST segment elevation myocardial infarction (STEMI) with a paired acute (4±2 days) and follow-up CMR scan (5±2 months) were recruited prospectively. All CMR analysis was performed on CVI42.

Results

Using manual MI size as the reference standard, 6-SD accurately quantified acute (24.9±14.0%LV, p=0.81, no bias) and chronic MI size (17.2±9.7%LV, p=0.88, no bias). The performance of FWHM for acute MI size was affected by the acquisition sequence used. Furthermore, FWHM underestimated chronic MI size in those with previous MVO due to the significantly higher ECV in the MI core on the follow-up scans previously occupied by MVO (82 (75–88)% vs 62 (51–68)%, p<0.001). 5-SD and Otsu were precise but overestimated acute and chronic MI size. All techniques were performed with high diagnostic accuracy and equally well to predict adverse LV remodelling.

Conclusions

6-SD was the most accurate for acute and chronic MI size and should be the preferred semiautomatic technique in randomised controlled trials. However, 5-SD, FWHM and Otsu could also be used when precise MI size quantification may be adequate (eg, observational studies).

Three-dimensional speckle tracking echocardiography and cardiac magnetic resonance for left ventricular chamber quantification and identification of myocardial transmural scar

Background

We compared three-dimensional speckle tracking echocardiography (3DSTE) and its strain to cardiac magnetic resonance (CMR) with delayed contrast enhancement for left ventricular (LV) chamber quantification and transmurality of myocardial scar. Furthermore, we examined the ability of 3DSTE strain to differentiate between ischaemic and non-ischaemic LV dysfunction.

Methods

In 80 consecutive patients with ischaemic and 40 patients with non-ischaemic LV dysfunction, the correlations between LV volumes and ejection fraction were measured using 3DSTE and CMR. Global and regional 3DSTE strains and total or percentage enhanced LV mass were evaluated.

Results

LV end-diastolic and end-systolic volumes and ejection fraction correlated well between 3DSTE and CMR (r: 0.83, 0.88 and 0.89, respectively). However, 3DSTE significantly underestimated volumes. Correlation for LV mass was modest (r = 0.59). All 3DSTE regional strain values except for radial strain were lower in segments with versus segments without transmural enhancement. However, strain parameters could not identify the transmurality of scar. No significant difference between ischaemic and non-ischaemic LV dysfunction was observed in either global or regional 3DSTE strain except for twist, which was lower in the non-ischaemic group (4.9 ± 3.3 vs. 6.4 ± 3.2°, p = 0.03).

Conclusion

3DSTE LV volumes are underestimated compared with CMR, while LV ejection fraction revealed excellent accuracy. Functional impairment by 3DSTE strain does not correlate well with scar localisation or extent by CMR. 3DSTE strain could not differentiate between ischaemic and non-ischaemic LV dysfunction. Future studies will need to clarify if 3DSTE strain and CMR delayed contrast enhancement can provide incremental value to the prediction of future cardiovascular events.

Late gadolinium enhancement does occur in Tako-tsubo cardiomyopathy - A quantitative cardiac magnetic resonance and speckle tracking strain study

Background

Late gadolinium enhancement (LGE) on cardiac magnetic resonance imaging (CMR) has been recommended to distinguish Tako-tsubo cardiomyopathy (TTC) from either acute myocardial infarction or myocarditis.

Method

44 consecutive patients with confirmed Mayo Clinic criteria for TTC underwent CMR imaging at 1.5 Tesla during the acute phase. 10 patients who had CMRI to exclude scar related ventricular tachycardia, and had negative studies, were used as negative controls. LGE was quantitated at two signal intensity thresholds (CircleCVi software) at > 2 and > 5 standard-deviations (SD) above reference myocardium, and compared to biomarkers.

Findings

Mean door-to-CMR time was 57 hours. 18 patients (41%) had LGE > 2 SD localized to the area of abnormal wall motion, representing 28.9 ± 11.2% LV mass. In 16 of these 18 patients (89%) LGE signal intensity was > 5 SD above normal myocardium, representing 12.1 ± 10% LV mass. LGE signal intensity was significantly greater in TTC than in matched controls (p < 0.05) but lower than in STEMI patients (p < 0.05). Mean troponin was significantly higher in LGE positive patients (2.5 ± 1.8 vs 4.4 ± 6.9, p = 0.001). Mean ejection fraction (EF) by CMR was 45% ± 8.7 in LGE-negative, and 40% ± 7.1 in LGE-positive patients (p = 0.37). Recovery of segmental function was confirmed at follow-up, mean EF was 59% in both groups.

Conclusion

LGE was present in 41% of cases of TTC, 89% of which had intense enhancement > 5 SD above normal myocardium. Presence of LGE was associated with worse myocardial injury in the acute setting, with no difference in recovery of function.

Myocardial infarct sizing by late gadolinium-enhanced MRI: Comparison of manual, full-width at half-maximum, and n-standard deviation methods

PURPOSE

To compare three widely used methods for myocardial infarct (MI) sizing on late gadolinium-enhanced (LGE) magnetic resonance (MR) images: manual delineation and two semiautomated techniques (full-width at half-maximum [FWHM] and n-standard deviation [SD]).

MATERIALS AND METHODS

3T phase-sensitive inversion-recovery (PSIR) LGE images of 114 patients after an acute MI (2-4 days and 6 months) were analyzed by two independent observers to determine both total and core infarct sizes (TIS/CIS). Manual delineation served as the reference for determination of optimal thresholds for semiautomated methods after thresholding at multiple values. Reproducibility and accuracy were expressed as overall bias ± 95% limits of agreement.

RESULTS

Mean infarct sizes by manual methods were 39.0%/24.4% for the acute MI group (TIS/CIS) and 29.7%/17.3% for the chronic MI group. The optimal thresholds (ie, providing the closest mean value to the manual method) were FWHM30% and 3SD for the TIS measurement and FWHM45% and 6SD for the CIS measurement (paired t-test; all P > 0.05). The best reproducibility was obtained using FWHM. For TIS measurement in the acute MI group, intra-/interobserver agreements, from Bland-Altman analysis, with FWHM30%, 3SD, and manual were -0.02 ± 7.74%/-0.74 ± 5.52%, 0.31 ± 9.78%/2.96 ± 16.62% and -2.12 ± 8.86%/0.18 ± 16.12, respectively; in the chronic MI group, the corresponding values were 0.23 ± 3.5%/-2.28 ± 15.06, -0.29 ± 10.46%/3.12 ± 13.06% and 1.68 ± 6.52%/-2.88 ± 9.62%, respectively. A similar trend for reproducibility was obtained for CIS measurement. However, semiautomated methods produced inconsistent results (variabilities of 24-46%) compared to manual delineation.

CONCLUSION

The FWHM technique was the most reproducible method for infarct sizing both in acute and chronic MI. However, both FWHM and n-SD methods showed limited accuracy compared to manual delineation. J. Magn. Reson. Imaging 2016;44:1206-1217.

In Vivo CT Direct Volume Rendering: A Three-Dimensional Anatomical Description of the Heart

BACKGROUND

Since cardiac anatomy continues to play an important role in the practice of medicine and in the development of medical devices, the study of the heart in three dimensions is particularly useful to understand its real structure, function and proper location in the body.

MATERIAL/METHODS

This study demonstrates a fine use of direct volume rendering, processing the data set images obtained by Computed Tomography (CT) of the heart of 5 subjects with age range between 18 and 42 years (2 male, 3 female), with no history of any overt cardiac disease. The cardiac structure in CT images was first extracted from the thorax by marking manually the regions of interest on the computer, and then it was stacked to create new volumetric data.

RESULTS

The use of a specific algorithm allowed us to observe with a good perception of depth the heart and the skeleton of the thorax at the same time. Besides, in all examined subjects, it was possible to depict its structure and its position within the body and to study the integrity of papillary muscles, the fibrous tissue of cardiac valve and chordae tendineae and the course of coronary arteries.

CONCLUSIONS

Our results demonstrated that one of the greatest advantages of algorithmic modifications of direct volume rendering parameters is that this method provides much necessary information in a single radiologic study. It implies a better accuracy in the study of the heart, being complementary to other diagnostic methods and facilitating the therapeutic plans.

Quantitative assessment of myocardial fibrosis in an age-related rat model by ex vivo late gadolinium enhancement magnetic resonance imaging with histopathological correlation

Late gadolinium enhanced (LGE) cardiac magnetic resonance (CMR) imaging can detect the presence of myocardial infarction from ischemic cardiomyopathies (ICM). However, it is more challenging to detect diffuse myocardial fibrosis from non-ischemic cardiomyopathy (NICM) with this technique due to more subtle and heterogeneous enhancement of the myocardium. This study investigates whether high-resolution LGE CMR can detect age-related myocardial fibrosis using quantitative texture analysis with histological validation. LGE CMR of twenty-four rat hearts (twelve 6-week-old and twelve 2-year-old) was performed using a 7T MRI scanner. Picrosirius red was used as the histopathology reference for collagen staining. Fibrosis in the myocardium was quantified with standard deviation (SD) threshold methods from the LGE CMR images and 3D contrast texture maps that were computed from gray level co-occurrence matrix of the CMR images. There was a significant increase of collagen fibers in the aged compared to the young rat histology slices (2.60±0.27 %LV vs. 1.24±0.29 %LV, p<0.01). Both LGE CMR and texture images showed a significant increase of myocardial fibrosis in the elderly compared to the young rats. Fibrosis in the LGE CMR images correlated strongly with histology with the 3 SD threshold (r=0.84, y=0.99x+0.00). Similarly, fibrosis in the contrast texture maps correlated with the histology using the 4 SD threshold (r=0.89, y=1.01x+0.00). High resolution ex-vivo LGE CMR can detect the presence of diffuse fibrosis that naturally developed in elderly rat hearts. Our results suggest that texture analysis may improve the assessment of myocardial fibrosis in LGE CMR images.

Influence of phase correction of late gadolinium enhancement images on scar signal quantification in patients with ischemic and non-ischemic cardiomyopathy

BACKGROUND

Myocardial fibrosis imaging using late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) has been validated as a quantitative predictive marker for response to medical, surgical, and device therapy. To date, all such studies have examined conventional, non-phase corrected magnitude images.  However, contemporary practice has rapdily adopted phase-corrected image reconstruction. We sought to investigate the existence of any systematic bias between threshold-based scar quantification performed on conventional magnitude inversion recovery (MIR) and matched phase sensitive inversion recovery (PSIR) images.

METHODS

In 80 patients with confirmed ischemic (N = 40), or non-ischemic (n = 40) myocardial fibrosis, and also in a healthy control cohort (N = 40) without fibrosis, myocardial late enhancement was quantified using a Signal Threshold Versus Reference Myocardium technique (STRM) at ≥2, ≥3, and ≥5 SD threshold, and also using the Full Width at Half Maximal (FWHM) technique. This was performed on both MIR and PSIR images and values compared using linear regression and Bland-Altman analyses.

RESULTS

Linear regression analysis demonstrated excellent correlation for scar volumes between MIR and PSIR images at all three STRM signal thresholds for the ischemic (N = 40, r = 0.96, 0.95, 0.88 at 2, 3, and 5 SD, p < 0.0001 for all regressions), and non ischemic (N = 40, r = 0.86, 0.89, 0.90 at 2, 3, and 5 SD, p < 0.0001 for all regressions) cohorts. FWHM analysis demonstrated good correlation in the ischemic population (N = 40, r = 0.83, p < 0.0001). Bland-Altman analysis demonstrated a systematic bias with MIR images showing higher values than PSIR for ischemic (3.3 %, 3.9 % and 4.9 % at 2, 3, and 5 SD, respectively), and non-ischemic (9.7 %, 7.4 % and 4.1 % at ≥2, ≥3, and ≥5 SD thresholds, respectively) cohorts. Background myocardial signal measured in the control population demonstrated a similar bias of 4.4 %, 2.6 % and 0.7 % of the LV volume at 2, 3 and 5 SD thresholds, respectively. The bias observed using FWHM analysis was -6.9 %.

CONCLUSIONS

Scar quantification using phase corrected (PSIR) images achieves values highly correlated to those obtained on non-corrected (MIR) images. However, a systematic bias exists that appears exaggerated in non-ischemic cohorts. Such bias should be considered when comparing or translating knowledge between MIR- and PSIR-based imaging.

Mapping the future of cardiac MR imaging: case-based review of T1 and T2 mapping techniques

Cardiac magnetic resonance (MR) imaging has grown over the past several decades into a validated, noninvasive diagnostic imaging tool with a pivotal role in cardiac morphologic and functional assessment and tissue characterization. With traditional cardiac MR imaging sequences, assessment of various pathologic conditions ranging from ischemic and nonischemic cardiomyopathy to cardiac involvement in systemic diseases (eg, amyloidosis and sarcoidosis) is possible; however, these sequences are most useful in focal myocardial disease, and image interpretation relies on subjective qualitative analysis of signal intensity. Newer T1 and T2 myocardial mapping techniques offer a quantitative assessment of the myocardium (by using T1 and T2 relaxation times), which can be helpful in focal disease, and demonstrate special utility in the evaluation of diffuse myocardial disease (eg, edema and fibrosis). Altered T1 and T2 relaxation times in disease states can be compared with published ranges of normal relaxation times in healthy patients. In conjunction with traditional cardiac MR imaging sequences, T1 and T2 mapping can limit the interpatient and interstudy variability that are common with qualitative analysis and may provide clinical markers for long-term follow-up.

Quantification of infarct size and myocardium at risk: evaluation of different techniques and its implications

AIMS

The aim of this study was to evaluate seven methods for quantifying myocardial oedema [2 standard deviation (SD), 3 SD, 5 SD, full width at half maximum (FWHM), Otsu method, manual thresholding, and manual contouring] from T2-weighted short tau inversion recovery (T2w STIR) and also to reassess these same seven methods for quantifying acute infarct size following ST-segment myocardial infarction (STEMI). This study focuses on test-retest repeatability while assessing inter- and intraobserver variability. T2w STIR and late gadolinium enhancement (LGE) are the most widely used cardiovascular magnetic resonance (CMR) techniques to image oedema and infarction, respectively. However, no consensus exists on the best quantification method to be used to analyse these images. This has potential important implications in the research setting where both myocardial oedema and infarct size are increasingly used and measured as surrogate endpoints in clinical trials.

METHODS AND RESULTS

Forty patients day 2 following acute reperfused STEMI were scanned for myocardial oedema and infarction (LGE). All patients had a second CMR scan on the same day >6 h apart from the first one. Images were analysed offline by two independent observers using the semi-automated software. Both oedema and LGE were quantified using seven techniques (2 SD, 3 SD, 5 SD, Otsu, FWHM, manual threshold, and manual contouring). Interobserver, intraobserver and test-retest agreement and variability for both infarct size and oedema quantification were assessed. Infarct size and myocardial quantification vary depending on the quantification method used. Overall, manual contouring provided the lowest inter-, intraobserver, and interscan variability for both infarct size and oedema quantification. The FWHM method for infarct size quantification and the Otsu method for myocardial oedema quantification are acceptable alternatives.

CONCLUSIONS

This study determines that, in acute myocardial infarction (MI), manual contouring has the lowest overall variability for quantification of both myocardial oedema and MI when analysed by experienced observers.

Adipose-derived regenerative cells in patients with ischemic cardiomyopathy: The PRECISE Trial

AIMS

Adipose-derived regenerative cells (ADRCs) can be isolated from liposuction aspirates and prepared as fresh cells for immediate administration in cell therapy. We performed the first randomized, placebo-controlled, double-blind trial to examine the safety and feasibility of the transendocardial injections of ADRCs in no-option patients with ischemic cardiomyopathy.

METHODS AND RESULTS

Procedural, postoperative, and follow-up safety end points were monitored up to 36 months. After baseline measurements, efficacy was assessed by echocardiography and single-photon emission computed tomography (6, 12, and 18 months), metabolic equivalents and maximal oxygen consumption (MVO2) (6 and 18 months), and cardiac magnetic resonance imaging (6 months). We enrolled 21 ADRC-treated and 6 control patients. Liposuction was well tolerated, ADRCs were successfully prepared, and transendocardial injections were feasible in all patients. No malignant arrhythmias were seen. Adverse events were similar between groups. Metabolic equivalents and MVO2 values were preserved over time in ADRC-treated patients but declined significantly in the control group. The difference in the change in MVO2 from baseline to 6 and 18 months was significantly better in ADRC-treated patients compared with controls. The ADRC-treated patients showed significant improvements in total left ventricular mass by magnetic resonance imaging and wall motion score index. Single-photon emission computed tomography results suggested a reduction in inducible ischemia in ADRC-treated patients up to 18 months.

CONCLUSION

Isolation and transendocardial injection of autologous ADRCs in no-option patients were safe and feasible. Our results suggest that ADRCs may preserve ventricular function, myocardial perfusion, and exercise capacity in these patients.

Prognosis after ST-elevation myocardial infarction: a study on cardiac magnetic resonance imaging versus clinical routine

Background

This study aimed to evaluate the incremental prognostic value of infarct size, microvascular obstruction (MO), myocardial salvage index (MSI), and left ventricular ejection fraction (LV-EF_CMR) assessed by cardiac magnetic resonance imaging (CMR) in comparison to traditional outcome markers in patients with ST-elevation myocardial infarction (STEMI) reperfused by primary percutaneous intervention (PCI).

Methods

STEMI patients reperfused by primary PCI (n = 278) within 12 hours after symptom onset underwent CMR three days after the index event (interquartile range [IQR] two to four). Infarct size and MO were measured 15 minutes after gadolinium injection. T2-weighted and contrast-enhanced CMR were used to calculate MSI. In addition, traditional outcome markers such as ST-segment resolution, pre- and post-PCI Thrombolysis In Myocardial Infarction (TIMI)-flow, maximum level of creatine kinase-MB, TIMI-risk score, and left ventricular ejection fraction assessed by echocardiography were determined in all patients. Clinical follow-up was conducted after 19 months (IQR 10 to 27). The primary endpoint was defined as a composite of death, myocardial reinfarction, and congestive heart failure (MACE).

Results

In multivariable Cox regression analysis, adjusting for all traditional outcome parameters significantly associated with the primary endpoint in univariable analysis, MSI was identified as an independent predictor for the occurrence of MACE (Hazard ratio 0.94, 95% CI 0.92 to 0.96, P <0.001). Further, C-statistics comparing a model including only traditional outcome markers to a model including CMR parameters on top of traditional outcome markers revealed an incremental prognostic value of CMR parameters (0.74 versus 0.94, P <0.001).

Conclusions

CMR parameters such as infarct size, MO, MSI, and LV-EF_CMR add incremental prognostic value above traditional outcome markers alone in acute reperfused STEMI.

Trial registration

Clinicaltrials.gov NCT00463749, Clinicaltrials.gov NCT00359918.

Myocardial scar identification based on analysis of Look-Locker and 3D late gadolinium enhanced MRI

The aim of this study is to introduce and evaluate an approach for objective and reproducible scar identification from late gadolinium enhanced (LGE) MR by analysis of LGE data with post-contrast T(1) mapping from a routinely acquired T(1) scout Look-Locker (LL) sequence. In 90 post-infarction patients, a LL sequence was acquired prior to a three-dimensional LGE sequence covering the entire left ventricle. In 60/90 patients (training set), the T(1) relaxation rates of remote myocardium and dense myocardial scar were linearly regressed to that of blood. The learned linear relationship was applied to 30/90 patients (validation set) to identify the remote myocardium and dense scar, and to normalize the LGE signal intensity to a range from 0 to 100 %. A 50 % threshold was applied to identify myocardial scar. In the validation set, two observers independently performed manual scar identification, annotated reference regions for the full-width-half-maxima (FWHM) and standard deviation (SD) method, and analyzed the LL sequence for the proposed method. Compared with the manual, FWHM, and SD methods, the proposed method demonstrated the highest inter-class correlation coefficient (0.997) and Dice overlap index (98.7 ± 1.3 %) between the two observers. The proposed method also showed excellent agreement with the gold-standard manual scar identification, with a Dice index of 89.8 ± 7.5 and 90.2 ± 6.6 % for the two observers, respectively. Combined analysis of LL and LGE sequences leads to objective and reproducible myocardial scar identification in post-infarction patients.

Different contribution of extent of myocardial injury to left ventricular systolic and diastolic function in early reperfused acute myocardial infarction

Background

We sought to investigate the influence of the extent of myocardial injury on left ventricular (LV) systolic and diastolic function in patients after reperfused acute myocardial infarction (AMI).

Methods

Thirty-eight reperfused AMI patients underwent cardiac magnetic resonance (CMR) imaging after percutaneous coronary revascularization. The extent of myocardial edema and scarring were assessed by T2 weighted imaging and late gadolinium enhancement (LGE) imaging, respectively. Within a day of CMR, echocardiography was done. Using 2D speckle tracking analysis, LV longitudinal, circumferential strain, and twist were measured.

Results

Extent of LGE were significantly correlated with LV systolic functional indices such as ejection fraction (r = -0.57, p < 0.001), regional wall motion score index (r = 0.52, p = 0.001), and global longitudinal strain (r = 0.56, p < 0.001). The diastolic functional indices significantly correlated with age (r = -0.64, p < 0.001), LV twist (r = -0.39, p = 0.02), average non-infarcted myocardial circumferential strain (r = -0.52, p = 0.001), and LV end-diastolic wall stress index (r = -0.47, p = 0.003 with e’) but not or weakly with extent of LGE. In multivariate analysis, age and non-infarcted myocardial circumferential strain independently correlated with diastolic functional indices rather than extent of injury.

Conclusions

In patients with timely reperfused AMI, not only extent of myocardial injury but also age and non-infarcted myocardial function were more significantly related to LV chamber diastolic function.

Multi-Stencil Streamline Fast Marching: A General 3-D Framework to Determine Myocardial Thickness and Transmurality in Late Enhancement Images

We propose a fully 3-D methodology for the computation of myocardial nonviable tissue transmurality in contrast enhanced magnetic resonance images. The outcome is a continuous map defined within the myocardium where not only current state-of-the-art measures of transmurality can be calculated, but also information on the location of nonviable tissue is preserved. The computation is done by means of a partial differential equation framework we have called multi-stencil streamline fast marching. Using it, the myocardial and scarred tissue thickness is simultaneously computed. Experimental results show that the proposed 3-D method allows for the computation of transmurality in myocardial regions where current 2-D methods are not able to as conceived, and it also provides more robust and accurate results in situations where the assumptions on which current 2-D methods are based-i.e., there is a visible endocardial contour and its corresponding epicardial points lie on the same slice-, are not met.

Quality assessment of cardiovascular magnetic resonance in the setting of the European CMR registry: description and validation of standardized criteria

BACKGROUND

Cardiovascular magnetic resonance (CMR) has become an important diagnostic imaging modality in cardiovascular medicine. However, insufficient image quality may compromise its diagnostic accuracy. We aimed to describe and validate standardized criteria to evaluate a) cine steady-state free precession (SSFP), b) late gadolinium enhancement (LGE), and c) stress first-pass perfusion images. These criteria will serve for quality assessment in the setting of the Euro-CMR registry.

METHODS

Thirty-five qualitative criteria were defined (scores 0-3) with lower scores indicating better image quality. In addition, quantitative parameters were measured yielding 2 additional quality criteria, i.e. signal-to-noise ratio (SNR) of non-infarcted myocardium (as a measure of correct signal nulling of healthy myocardium) for LGE and % signal increase during contrast medium first-pass for perfusion images. These qualitative and quantitative criteria were assessed in a total of 90 patients (60 patients scanned at our own institution at 1.5T (n=30) and 3T (n=30) and in 30 patients randomly chosen from the Euro-CMR registry examined at 1.5T). Analyses were performed by 2 SCMR level-3 experts, 1 trained study nurse, and 1 trained medical student.

RESULTS

The global quality score was 6.7±4.6 (n=90, mean of 4 observers, maximum possible score 64), range 6.4-6.9 (p=0.76 between observers). It ranged from 4.0-4.3 for 1.5T (p=0.96 between observers), from 5.9-6.9 for 3T (p=0.33 between observers), and from 8.6-10.3 for the Euro-CMR cases (p=0.40 between observers). The inter- (n=4) and intra-observer (n=2) agreement for the global quality score, i.e. the percentage of assignments to the same quality tertile ranged from 80% to 88% and from 90% to 98%, respectively. The agreement for the quantitative assessment for LGE images (scores 0-2 for SNR <2, 2-5, >5, respectively) ranged from 78-84% for the entire population, and 70-93% at 1.5T, 64-88% at 3T, and 72-90% for the Euro-CMR cases. The agreement for perfusion images (scores 0-2 for %SI increase >200%, 100%-200%,<100%, respectively) ranged from 81-91% for the entire population, and 76-100% at 1.5T, 67-96% at 3T, and 62-90% for the Euro-CMR registry cases. The intra-class correlation coefficient for the global quality score was 0.83.

CONCLUSIONS

The described criteria for the assessment of CMR image quality are robust with a good inter- and intra-observer agreement. Further research is needed to define the impact of image quality on the diagnostic and prognostic yield of CMR studies.

Intracoronary infusion of mononuclear cells after PCI-treated myocardial infarction and arrhythmogenesis: is it safe?

To reduce long-term morbidity after revascularised acute myocardial infarction, different therapeutic strategies have been investigated. Cell therapy with mononuclear cells from bone marrow (BMMC) or peripheral blood (PBMC) has been proposed to attenuate the adverse processes of remodelling and subsequent heart failure. Previous trials have suggested that cell therapy may facilitate arrhythmogenesis. In the present substudy of the HEBE cell therapy trial, we investigated whether intracoronary cell therapy alters the prevalence of ventricular arrhythmias after 1 month or the rate of severe arrhythmogenic events (SAE) in the first year. In 164 patients of the trial we measured function and infarct size with cardiovascular magnetic resonance (CMR) imaging. Holter registration was performed after 1 month from which the number of triplets (3 successive PVCs) and ventricular tachycardias (VT, ≥4 successive PVCs) was assessed. Thirty-three patients (20%) showed triplets and/or VTs, with similar distribution amongst the groups (triplets: control n = 8 vs. BMMC n = 9, p = 1.00; vs. PBMC n = 10, p = 0.67. VT: control n = 9 vs. BMMC n = 9, p = 0.80; vs. PBMC n = 11, p = 0.69). SAE occurred in 2 patients in the PBMC group and 1 patient in the control group. In conclusion, intracoronary cell therapy is not associated with an increase in ventricular arrhythmias or SAE.

Revascularization in patients with chronic ischaemic myocardial dysfunction: insights from cardiovascular magnetic resonance imaging

In patients with chronic ischaemic left ventricular dysfunction, revascularization may lead to symptomatic and prognostic improvement. Cardiovascular magnetic resonance (CMR) imaging with its high spatial resolution provides the qualitative and quantitative, global and regional information on myocardial anatomy and function. In combination with a gadolinium-based contrast agent, CMR allows an accurate quantification of the myocardial scar and predicts the likelihood of functional recovery after revascularization. The aim of this review is to summarize our current understanding of the detection of myocardial viability using CMR, and why it may be the preferred technique in the assessment of patients with ischaemic cardiomyopathy.

Relationship and prognostic value of microvascular obstruction and infarct size in ST-elevation myocardial infarction as visualized by magnetic resonance imaging

BACKGROUND

Both infarct size and microvascular obstruction (MO) assessed by cardiac magnetic resonance imaging (CMR) are known to be predictors for adverse clinical outcome after ST-elevation myocardial infarction (STEMI). We hypothesized that a ratio of MO and infarct size (MO/infarct size) might be an even stronger predictor for outcome after STEMI, which has not been investigated yet.

METHODS

STEMI patients reperfused by primary angioplasty (n = 438) within 12 h after symptom onset underwent contrast-enhanced CMR at a median of 3 days (interquartile range [IQR] 2;4) after the index event. MO and infarct size were measured 15 min after intravenous gadolinium injection. Follow-up was conducted after 19 months (IQR 10;27). The primary end point was defined as a composite of death, non-fatal myocardial reinfarction and congestive heart failure (major adverse cardiac events [MACE]).

RESULTS

The extent of MO was only weakly correlated with infarct size (r = 0.21, p < 0.001). In a first multivariate analysis including extent of MO, infarct size, ejection fraction, end-systolic and end-diastolic volume, the extent of MO was independently associated with MACE (hazard ratio [HR] 1.03, 95%CI 1.02–1.05, p < 0.001). In a second multivariate analysis including MO/infarct size on top of the extent of MO, infarct size, ejection fraction, end-systolic and end-diastolic volume, MO/infarct size was identified as the strongest independent predictor for MACE (HR 2.22 [95%CI 1.60–3.08, p < 0.001]).

CONCLUSIONS

In contrast to infarct size, MO is associated with adverse clinical outcome after STEMI even after adjustment for other CMR parameters. However, MO/infarct size is a more powerful predictor for long-term outcome after STEMI than either parameter alone.

CMR imaging assessing viability in patients with chronic ventricular dysfunction due to coronary artery disease: a meta-analysis of prospective trials

OBJECTIVES

The purpose of this study was to compare the diagnostic accuracy of cardiac magnetic resonance (CMR) assessing myocardial viability in patients with chronic left ventricular (LV) dysfunction due to coronary artery disease using 3 techniques: 1) end-diastolic wall thickness (EDWT); 2) low-dose dobutamine (LDD); and 3) contrast delayed enhancement (DE).

BACKGROUND

CMR has been proposed to assess myocardial viability over the past decade. However, the best CMR strategy to evaluate patients being contemplated for revascularization has not yet been determined. Some centers advocate DE CMR due to its high sensitivity to identify scar, whereas others favor the use of LDD CMR for its ability to identify contractile reserve.

METHODS

A systematic review of MEDLINE, Cochrane, and Embase for all the prospective trials assessing myocardial viability in subjects with chronic LV dysfunction using CMR was performed using a standard approach for meta-analysis for diagnostic tests and a bivariate analysis of sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV).

RESULTS

A total of 24 studies of CMR evaluating myocardial viability with 698 patients fulfilled the inclusion criteria. Eleven studies used DE, 9 studies used LDD, and 4 studies used EDWT. Our meta-analysis indicates that among CMR methods, DE CMR provides the highest sensitivity as well as the highest NPV (95% and 90%, respectively) for predicting improved segmental LV contractile function after revascularization, followed by EDWT CMR, whereas LDD CMR demonstrated the lowest sensitivity/NPV among all modalities. On the other hand, LDD CMR offered the highest specificity and PPV (91% and 93%, respectively), followed by DE CMR, whereas EDWT showed the lowest of these parameters.

CONCLUSIONS

DE CMR provides the highest sensitivity and NPV, whereas LDD CMR provides the best specificity and PPV. In light of these findings, integrating these 2 methods should provide increased accuracy in evaluating patients with chronic LV dysfunction being considered for revascularization.

Intraindividual comparison of gadobutrol and gadopentetate dimeglumine for detection of myocardial late enhancement in cardiac MRI

OBJECTIVE

Gadobutrol is an extracellular macrocyclic gadolinium chelate recently introduced in MRI, and it has already been used for cardiac late enhancement imaging; however, until now it has never been compared with gadopentetate dimeglumine. The purpose of our study was to compare 0.1 mmol/kg gadobutrol to 0.2 mmol/kg gadopentetate dimeglumine for the detection of myocardial late enhancement in the same group of patients.

SUBJECTS AND METHODS

This was an exploratory single-blind parallel group study comparing gadobutrol (0.1 mmol/kg) to gadopentetate dimeglumine (0.2 mmol/kg) in 20 adult patients scheduled for cardiac late enhancement MRI with gadopentetate dimeglumine and whose MR images showed late enhancement. MR images were acquired at 10, 15, and 20 minutes after peripheral injection of gadobutrol by using a 3D turbo field echo inversion recovery T1-weighted sequence. Volume and percentage of late enhancement, number of involved segments, late enhancement localization and pattern, and late enhancement signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were compared between contrast agents.

RESULTS

Late enhancement was not significantly different with gadobutrol and gadopentetate dimeglumine both in terms of total volume of myocardium (mean ± SD, 37.8 ± 56.1 and 35.1 ± 46.7 cm(3), respectively; p = 0.33) and percentage of myocardial wall involvement (22.5% ± 19.1% and 22.0% ± 17.2%, respectively; p = 0.67). The number of segments involved was not different (138 with gadobutrol vs 134 with gadopentetate dimeglumine). Furthermore, SNR and CNR were not different (gadopentetate dimeglumine, 123.8 ± 82.9 and gadobutrol, 117.2 ± 88.6, p = 0.58 and gadopentetate dimeglumine, 96.2 ± 68.9 and gadobutrol, 88.4 ± 72.9, p = 0.53, respectively).

CONCLUSION

A single dose of gadobutrol seems to be as effective as a double dose of gadopentetate dimeglumine for the detection of late enhancement.