Assessment of regional systolic and diastolic dysfunction in familial hypertrophic cardiomyopathy using MR tagging

Peak early diastolic strain rate improves prediction of adverse cardiovascular outcomes in patients with ST-elevation myocardial infarction

BACKGROUND

The prognostic role of diastolic dysfunction measured by the circumferential peak early diastolic strain rate (PEDSR) on ST-elevation myocardial infarction (STEMI) is not completely established.

OBJECTIVES

We aimed to investigate the prognostic value of diastolic function by measuring PEDSR within 1 week after STEMI.

METHODS

The cardiac magnetic resonance (CMR) pictures of 420 subjects from a clinical registry study (NCT03768453) were analyzed and the composite major adverse cardiac events (MACEs) were followed up.

RESULTS

The PEDSR of patients was significantly lower compared with that of control subjects (P < 0.001). Within the median follow-up period of 52 months, PEDSR of patients who experienced MACEs deceased more significantly than that of patients without MACEs (P < 0.001). After adjusting with clinical or CMR indexes, per 0.1/s reduction of PEDSR increased the risks of MACEs to 1.402 or 1.376 fold and the risk of left ventricular (LV) remodeling to 1.503 or 1.369 fold. When PEDSR divided by best cutoff point, significantly higher risk of MACEs (P < 0.001) and more remarkable LV remodeling (P < 0.001) occurred in patients with PEDSR ≤ 0.485/s. Moreover, when adding the PEDSR to the conventional prognostic factors such as LV ejection fraction and infarction size, better prognostic risk classification models were created. Finally, aging, tobacco use, remarkable LV remodeling, and a low LV ejection fraction were factors related with the reduction of PEDSR.

CONCLUSIONS

Diastolic dysfunction has an important prognostic effect on patients with STEMI. Measurement of the PEDSR in the acute phase could serve as an effective index to predict the long-term risk of MACEs and cardiac remodeling.

Diastolic Cardiac Function by MRI-Imaging Capabilities and Clinical Applications

Most cardiac studies focus on evaluating left ventricular (LV) systolic function. However, the assessment of diastolic cardiac function is becoming more appreciated, especially with the increasing prevalence of pathologies associated with diastolic dysfunction like heart failure with preserved ejection fraction (HFpEF). Diastolic dysfunction is an indication of abnormal mechanical properties of the myocardium, characterized by slow or delayed myocardial relaxation, abnormal LV distensibility, and/or impaired LV filling. Diastolic dysfunction has been shown to be associated with age and other cardiovascular risk factors such as hypertension and diabetes mellitus. In this context, cardiac magnetic resonance imaging (MRI) has the capability for differentiating between normal and abnormal myocardial relaxation patterns, and therefore offers the prospect of early detection of diastolic dysfunction. Although diastolic cardiac function can be assessed from the ratio between early and atrial filling peaks (E/A ratio), measuring different parameters of heart contractility during diastole allows for evaluating spatial and temporal patterns of cardiac function with the potential for illustrating subtle changes related to age, gender, or other differences among different patient populations. In this article, we review different MRI techniques for evaluating diastolic function along with clinical applications and findings in different heart diseases.

Finite-element based optimization of left ventricular passive stiffness in normal volunteers and patients after myocardial infarction: Utility of an inverse deformation gradient calculation of regional diastolic strain

INTRODUCTION

Left ventricular (LV) diastolic dysfunction (DD) is common after myocardial infarction (MI). Whereas current clinical assessment of DD relies on indirect markers including LV filling, finite element (FE) -based computational modeling directly measures regional diastolic stiffness. We hypothesized that an inverse deformation gradient (DG) method calculation of diastolic strain (IDGDS) allows the FE model-based calculation of regional diastolic stiffness (material parameters; MP) in post-MI patients with DD.

METHODS

Cardiac magnetic resonance (CMR) with tags (CSPAMM) and late gadolinium enhancement (LGE) was performed in 10 patients with post-MI DD and 10 healthy volunteers. The 3-dimensional (3D) LV DG from end-diastole (ED) to early diastolic filling (EDF; DG_ED→EDF) was calculated from CSPAMM. Diastolic strain was calculated from DG_EDF→ED by inverting the DG_ED→EDF. FE models were created with MI and non-MI (remote; RM) regions determined by LGE. Guccione MPs C, and exponential fiber, b_f, and transverse, b_t , terms were optimized with IDGDS strain.

RESULTS

3D circumferential and longitudinal diastolic strain (E_cc;E_ll) calculated using IDGDS in CSPAMM obtained in volunteers and MI patients were [Formula: see text]  = 0.27 ± 0.01, [Formula: see text]  = 0.24 ± 0.03 and [Formula: see text]  = 0.21 ± 0.02, and [Formula: see text]  = 0.15 ± 0.02, respectively. MPs in the volunteer group were C_H = 0.013 [0.001, 0.235] kPa, [Formula: see text]  = 20.280 ± 4.994, and [Formula: see text]  = 7.460 ± 2.171 and C_RM = 0.0105 [0.010, 0.011] kPa, [Formula: see text]  = 50.786 ± 13.511 (p = 0.0846), and [Formula: see text]  = 17.355 ± 2.743 (p = 0.0208) in the remote myocardium of post-MI patients.

CONCLUSION

Diastolic strain, calculated from CSPAMM with IDGDS, enables calculation of FE model-based regional diastolic material parameters. Transverse stiffness of the remote myocardium, , may be a valuable new metric for determination of DD in patients after MI.

Speckle tracking deformation imaging to detect regional fibrosis in hypertrophic cardiomyopathy: a comparison between 2D and 3D echo modalities

AIMS

We aimed at directly comparing three-dimensional (3D) and two-dimensional (2D) deformation parameters in hypertrophic hearts and depict which may best reflect underlying fibrosis in hypertrophic cardiomyopathy (HCM), defined by late gadolinium enhancement (LGE) in cardiac magnetic resonance (CMR).

METHODS AND RESULTS

We included 40 HCM [54.1 ± 14.3 years, 82.5% male, maximum wall thickness (MWT) 19.3 ± 4.8 mm] and 15 hypertensive (HTN) patients showing myocardial hypertrophy (58.1 ± 15.6 years, 80% male, MWT 12.8 ± 1.4 mm) who have consecutively undergone 2D-, 3D-speckle tracking echocardiography and LGE CMR. Deformation parameters (2D and 3D) presented overall poor to moderate correlations, with 3D_longitudinal strain (LS) and 3D_circumferential strain (CS) values being constantly higher compared to 2D derivatives. By regression analysis, hypertrophy substrate (HCM vs. hypertension) and hypertrophy magnitude were the parameters to influence 2D-3D LS and CS strain correlations (R2 = 0.66, P < 0.001 and R2 = 0.5, P = 0.001 accordingly). Among segmental deformation indices, 2D_LS showed the best area under the curve [AUC = 0.78, 95% confidence intervals (CI) (0.75-0.81), P < 0.0005] to detect fibrosis, with 3D deformation parameters showing similar AUC (0.65) and 3D_LS presenting the highest specificity [93.1%, 95% CI (90.6-95.1)].

CONCLUSIONS

In hypertrophic hearts, 2D and 3D deformation parameters are not interchangeable, showing modest correlations. Thickness, substrate, and tracking algorithm calculating assumptions seem to induce this variability. Nevertheless, among HCM patients 2D_peak segmental longitudinal strain remains the best strain parameter for tissue characterization and fibrosis detection.

Phenotyping of hypertensive heart disease and hypertrophic cardiomyopathy using personalized 3D modelling and cardiac cine MRI

Differential diagnosis of hypertensive heart disease (HHD) and hypertrophic cardiomyopathy (HCM) is clinically challenging but important for treatment management. This study aims to phenotype HHD and HCM in 3D + time domain by using a multiparametric motion-corrected personalized modeling algorithm and cardiac magnetic resonance (CMR). 44 CMR data, including 12 healthy, 16 HHD and 16 HCM cases, were examined. Multiple CMR phenotype data consisting of geometric and dynamic variables were extracted globally and regionally from the models over a full cardiac cycle for comparison against healthy models and clinical reports. Statistical classifications were used to identify the distinctive characteristics and disease subtypes with overlapping functional data, providing insights into the challenges for differential diagnosis of both types of disease. While HCM is characterized by localized extreme hypertrophy of the LV, wall thickening/contraction/strain was found to be normal and in sync, though it was occasionally exaggerated at normotrophic/less severely hypertrophic regions during systole to preserve the overall ejection fraction (EF) and systolic functionality. Additionally, we observed that hypertrophy in HHD could also be localized, although at less extreme conditions (i.e. more concentric). While fibrosis occurs mostly in those HCM cases with aortic obstruction, only minority of HHD patients were found affected by fibrosis. We demonstrate that subgroups of HHD (i.e. preserved and reduced EF: HHDpEF & HHDrEF) have different 3D + time CMR characteristics. While HHDpEF has cardiac functions in normal range, dilation and heart failure are indicated in HHDrEF as reflected by low LV wall thickening/contraction/strain and synchrony, as well as much reduced EF.

Assessment of diastolic dysfunction: comparison of different cardiovascular magnetic resonance techniques

Aims

Heart failure with preserved ejection fraction is still a diagnostic and therapeutic challenge, and accurate non‐invasive diagnosis of left ventricular (LV) diastolic dysfunction (DD) remains difficult. The current study aimed at identifying the most informative cardiovascular magnetic resonance (CMR) parameters for the assessment of LVDD.

Methods and results

We prospectively included 50 patients and classified them into three groups: with DD (DD+, n = 15), without (DD−, n = 26), and uncertain (DD±, n = 9). Diagnosis of DD was based on echocardiographic E/E′, invasive LV end‐diastolic pressure, and N‐terminal pro‐brain natriuretic peptide. CMR was performed at 1.5 T to assess LV and left atrial (LA) morphology, LV diastolic strain rate (SR) by tissue tracking and tagging, myocardial peak velocities by tissue phase mapping, and transmitral inflow profile using phase contrast techniques. Statistics were performed only on definitive DD+ and DD− (total number 41). DD+ showed enlarged LA with LA end‐diastolic volume/height performing best to identify DD+ with a cut‐off value of ≥0.52 mL/cm (sensitivity = 0.71, specificity = 0.84, and area under the receiver operating characteristic curve = 0.75). DD+ showed significantly reduced radial (inferolateral E peak: DD−: −14.5 ± 6.5%/s vs. DD+: −10.9 ± 5.9%/s, P = 0.04; anterolateral A peak: DD−: −4.2 ± 1.6%/s vs. DD+: −3.1 ± 1.4%/s, P = 0.04) and circumferential (inferolateral A peak: DD−: 3.8 ± 1.2%/s vs. DD+: 2.8 ± 0.8%/s, P = 0.007; anterolateral A peak: DD−: 3.5 ± 1.2%/s vs. DD+: 2.5 ± 0.8%/s, P = 0.048) SR in the basal lateral wall assessed by tissue tracking. In the same segments, DD+ showed lower peak myocardial velocity by tissue phase mapping (inferolateral radial peak: DD−: −3.6 ± 0.7 ms vs. DD+: −2.8 ± 1.0 ms, P = 0.017; anterolateral longitudinal peak: DD−: −5.0 ± 1.8 ms vs. DD+: −3.4 ± 1.4 ms, P = 0.006). Tagging revealed reduced global longitudinal SR in DD+ (DD−: 45.8 ± 12.0%/s vs. DD+: 34.8 ± 9.2%/s, P = 0.022). Global circumferential and radial SR by tissue tracking and tagging, LV morphology, and transmitral flow did not differ between DD+ and DD−.

Conclusions

Left atrial size and regional quantitative myocardial deformation applying CMR identified best patients with DD.

Altered regional myocardial velocities by tissue phase mapping and feature tracking in pediatric patients with hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is associated with heart failure, atrial fibrillation and sudden death. Reduced myocardial function has been reported in HCM despite normal left ventricular (LV) ejection fraction. Additionally, LV fibrosis is associated with elevated T1 and might be an outcome predictor.

OBJECTIVE

To systematically compare tissue phase mapping and feature tracking for assessing regional LV function in children and young adults with HCM and pediatric controls, and to evaluate structure-function relationships among myocardial velocities, LV wall thickness and myocardial T1.

MATERIALS AND METHODS

Seventeen pediatric patients with HCM and 21 age-matched controls underwent cardiac MRI including standard cine imaging, tissue phase mapping (two-dimensional cine phase contrast with three-directional velocity encoding), and modified Look-Locker inversion recovery to calculate native global LV T1. Maximum LV wall thickness was measured on cine images. LV radial, circumferential and long-axis myocardial velocity time courses, as well as global and segmental systolic and diastolic peak velocities, were quantified from tissue phase mapping and feature tracking.

RESULTS

Both tissue phase mapping and feature tracking detected significantly decreased global and segmental diastolic radial and long-axis peak velocities (by 12-51%, P<0.001-0.05) in pediatric patients with HCM vs. controls. Feature tracking peak velocities were lower than directly measured tissue phase mapping velocities (mean bias = 0.3-2.9 cm/s). Diastolic global peak velocities correlated moderately with global T1 (r = -0.57 to -0.72, P<0.01) and maximum wall thickness (r = -0.37 to -0.61, P<0.05).

CONCLUSION

Both tissue phase mapping and feature tracking detected myocardial velocity changes in children and young adults with HCM vs. controls. Associations between impaired diastolic LV velocities and elevated T1 indicate structure-function relationships in HCM.

Practical Guide to Evaluating Myocardial Disease by Cardiac MRI

OBJECTIVE. A spectrum of pathophysiologic mechanisms can lead to the development of myocardial disorders including ischemia, genetic abnormalities, and systemic disorders. Cardiac MRI identifies different myocardial disorders, provides prognostic information, and directs therapy. In comparison with other imaging modalities, cardiac MRI has the advantage of allowing both functional assessment and tissues characterization in a single examination without the use of ionizing radiation. Newer cardiac MRI techniques including mapping can provide additional information about myocardial disease that may not be detected using conventional techniques. Emerging techniques including MR spectroscopy and finger printing will likely change the way we understand the pathophysiology mechanisms of the wide array of myocardial disorders. CONCLUSION. Imaging of myocardial disorders encompasses a large variety of conditions including both ischemic and nonischemic diseases. Cardiac MRI sequences, such as balanced steady-state free precession and late gadolinium enhancement, play a critical role in establishing diagnosis, determining prognosis, and guiding therapeutic management. Additional sequences-including perfusion imaging, T2*, real-time cine, and T2-weighted sequences-should be performed in specific clinical scenarios. There is emerging evidence for the use of mapping in imaging of myocardial disease. Multiple other new techniques are currently being studied. These novel techniques will likely change the way myocardial disorders are understood and diagnosed in the near future.

3-Dimensional regional and global strain abnormalities in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is characterized by myocardial disarray, hypertrophy, and fibrosis. Reduced global longitudinal strain and presence of late gadolinium enhancement (LGE) by cardiac magnetic resonance imaging (CMR) have been associated with an adverse prognosis. This study evaluated 3D principal and conventional strain characteristics of non-enhanced myocardium in patients with HCM. 3D principal and conventional strain analysis was conducted in 51 HCM patients and 38 healthy controls. Principal strain was reduced within the non-enhanced myocardium of HCM as compared with controls (maximum principal: 51.5 ± 23.7 vs. 75.1 ± 21.4%, P < 0.0001; minimum principal: - 18.4 ± 4.0 vs. - 20.1 ± 2.9%, P < 0.05). Principal strain within the non-enhanced myocardium was incrementally reduced in HCM patients with extensive global LGE ( ≥ 15%) (maximum principal: 41.6 ± 17.5 vs. 56.9 ± 25.9%, P < 0.05; minimum principal: - 16.9 ± 3.9 vs. - 19.1 ± 4.0%, P = 0.1), as was longitudinal ( - 10.5 ± 2.6 vs. - 12.7 ± 2.6%, P < 0.05) and circumferential strain ( - 11.0 ± 2.7 vs. - 14.0 ± 2.9%, P < 0.01). Principal strain within non-enhanced myocardium was significantly correlated with indexed LV mass (P < 0.0001), maximum (P = 0.0008), and mean wall thickness (P < 0.0001), but not LGE (P = 0.0841). In adjusted analysis, all strain measures within non-enhanced myocardium were independently associated with indexed LV mass (maximum principal: P = 0.0003; minimum principal: P = 0.0039; longitudinal: P = 0.0015; circumferential: P = 0.0002; radial: P = 0.0023). 3D principal strain of non-enhanced myocardium was significantly reduced in HCM patients as compared with controls, and was incrementally reduced among patients with more extensive global LGE. Comprehensive strain assessment may be considered in routine CMR assessment of HCM patients.

Left ventricular function and regional strain with subtly-tagged steady-state free precession feature tracking

PURPOSE

To provide regional strain and ventricular volume from a single acquisition, using subtly tagged steady-state free precession (SubTag SSFP) feature tracking.

MATERIALS AND METHODS

The effects on regional strain of tag strength in gradient recalled echo (GRE) tagging, flip angle in untagged balanced SSFP, and both in SubTag SSFP were examined in the mid left ventricle of 15 healthy volunteers at 3T. Optimal parameters were determined from varying both tag strength and SSFP flip angle using full tag saturation GRE as the reference standard. SubTag SSFP was acquired in 15 additional healthy volunteers for whole-heart volume and strain assessment using the optimized parameters. Values measured by two image analysts were compared to clinical reference standards from untagged SSFP (volumes) and GRE tagging (strains).

RESULTS

Regional strain accuracy was maintained with decreasing total tagging flip angle (β); less than 3% differences for β ≥ 26°. For untagged SSFP flip angle (α), whole-wall strain differences became statistically significant when α < 40°. A SubTag SSFP acquisition with α = 40° and β = 46° showed the best combination of tagging strength, blood-myocardial contrast, and tag persistence at end-systole for regional strain estimation. SubTag SSFP also showed excellent agreement with untagged SSFP for volumetrics (percent difference: end-diastolic volume = 0.6%, end-systolic volume = 0.4%, stroke volume = 1.2%, ejection fraction = 0.6%, mass = 1.1%).

CONCLUSION

Feature tracking for regional myocardial strain assessment is dependent on image features, mainly the tag strength, persistence, and image contrast. SubTag SSFP balances these criteria to provide accurate regional strain and volumetric assessment in a single acquisition.

LEVEL OF EVIDENCE

1 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2018;47:787-797.

Hypertrophic cardiomyopathy and left ventricular hypertrophy in hypertensive heart disease with mildly reduced or preserved ejection fraction: insight from altered mechanics and native T1 mapping

AIM

To explore the relationship between extracellular volume (ECV), native T1, and systolic strain in hypertrophic cardiomyopathy (HCM) and hypertensive patients with left ventricular hypertrophy (HTN LVH) with mildly reduced or preserved ejection fraction.

MATERIALS AND METHODS

T1 mapping was performed in 45 patients with late gadolinium enhancement positive (LGE+) HCM (mean age, 53±6 years), 11 patients with LGE- (LGE-) HCM (mean age, 56±5 years), and 20 patients with HTN LVH (mean age, 55±6 years) on at 3 T magnetic resonance imaging (MRI) using the modified look-locker inversion-recovery (MOLLI) pulse sequence. Mean T1 value, ECV and circumferential strain parameters were determined for each patient.

RESULTS

Overall, the HCM patients had higher native T1 values (1242.92±68.94) and ECV (0.31±0.05) in comparison to those of the HTN LVH patients (1197±46.80, 0.27±0.04; p<0.05). In the subgroup analysis, the HCM LGE+ patients had the highest native T1 values among the three groups. The HCM LGE+ patients had higher ECV than the LGE- patients. HCM LGE- patients had higher ECV than HTN LVH patients (p<0.05). Peak systolic circumferential strain and early diastolic strain rates were reduced in the HCM LGE+ patients in comparison to the HCM LGE- and HTN LVH patients (p<0.05). Reduced peak systolic and early diastolic circumferential strain rates were associated with increased levels of ECV and native T1 values among all the patients.

CONCLUSION

HCM LGE+ patients had higher native T1 values, higher ECV, and an associated reduction in early diastolic strain rates and peak systolic circumferential strains when compared to the HCM LGE- and HTN LVH patients with mildly reduced or preserved ejection fraction.

Early marker of regional left ventricular deformation in patients with hypertrophic cardiomyopathy evaluated by MRI tissue tracking: The effects of myocardial hypertrophy and fibrosis

PURPOSE

To evaluate the regional left ventricular (LV) myocardial strain of early stage hypertrophic cardiomyopathy (HCM) patients by magnetic resonance (MR) tissue tracking.

MATERIALS AND METHODS

In all, 114 adult HCM patients classified as NYHA I or II and 32 healthy volunteers were enrolled and underwent 3.0T MR examination. Vertical 2-chamber long axis, horizontal 4-chamber, and short axis cine sequence as well as late gadolinium enhancement images (LGE) were scanned. The cardiac function, regional LV tissue tracking variables, end-diastolic wall thickness (EDTH), and LGE extent were measured.

RESULTS

In the HCM group, 38 were NYHA I and 76 were NYHA II. By regional analysis, peak strain (PS) and peak displacement (PD) with radial, circumferential direction of hypertrophic segments (n = 283) were significantly lower than nonhypertrophic segments (n = 1541) (all P < 0.05). Radial PS was significantly correlated with LVEDTH (r = -0.467, P < 0.0001). Radial PD was negatively associated with LVEDTH (r = -0.331, P < 0.0001). The PS and PD of all directions were decreased in segments with LGE (n = 723) compared with those without LGE (n = 1101) (all P < 0.05). In addition, radial PS and PD were negatively associated with LGE extent (radial PS, r = -0.441; radial PD, r = -0.274; both P < 0.0001). All strain parameters showed excellent inter- and intraobserver agreements.

CONCLUSION

Decreased regional LV myocardial strain hypertrophic and fibrotic segments of early-stage HCM patients can be measured by MR tissue tracking based on routine cine images. Moreover, myocardial strain may decrease with the increasing of myocardial hypertrophy as well as fibrosis.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2017;46:1368-1376.

Hypertrophic obstructive cardiomyopathy

Hypertrophic obstructive cardiomyopathy is an inherited myocardial disease defined by cardiac hypertrophy (wall thickness ≥15 mm) that is not explained by abnormal loading conditions, and left ventricular obstruction greater than or equal to 30 mm Hg. Typical symptoms include dyspnoea, chest pain, palpitations, and syncope. The diagnosis is usually suspected on clinical examination and confirmed by imaging. Some patients are at increased risk of sudden cardiac death, heart failure, and atrial fibrillation. Patients with an increased risk of sudden cardiac death undergo cardioverter-defibrillator implantation; in patients with severe symptoms related to ventricular obstruction, septal reduction therapy (myectomy or alcohol septal ablation) is recommended. Life-long anticoagulation is indicated after the first episode of atrial fibrillation.

Quantitative assessment of systolic and diastolic function in patients with LGE negative systemic amyloidosis using CMR

OBJECTIVES

In clinical routine myocardial affection in amyloidosis is assessed by qualitative late gadolinium enhancement (LGE). Recent studies suggest that early cardiac involvement in amyloidosis may be overlooked by qualitative LGE assessment. The aim of this study was to assess possible early cardiac involvement in LGE negative AL patients by means of systolic and diastolic strain assessment and quantitative enhancement.

METHODS

51 individuals (17 Patients with LGE positive light-chain amyloidosis (AL) (Group A), 17 Patients with LGE negative systemic AL (Group B), and 17 healthy controls (Group C)) were investigated. SSFP-Cine sequences were acquired in short axis slices as well as horizontal long axis views. Standard CMR parameters as well as Feature Tracking (FT) derived systolic and diastolic circumferential and longitudinal strain parameters were calculated. Additionally, contrast enhanced MRI images were analyzed to quantitatively determine the extent of enhancement.

RESULTS

AL patients with and without LGE both had significantly lower early diastolic strain rate (EDSR) values and peak systolic longitudinal strain (PSLS) values than healthy controls (EDSR: Group A 63.1±17.6; Group B: 74.46±11.8; Group C: 86.82±12.7; F(2.48)=10.7 p<0.001); (PSLS: Group A: -13.44±1.9%; Group B: -20.31±1.2%; Group C: -23.11±1.4%; F(2.48)=167.6; p<0.001). Analysis of quantitative LGE enhancement revealed increased enhancement in qualitative LGE negative AL patients compared to healthy controls (Group A: 19.6±8.9%; Group B: 8.2±3.9%; Group C: 2.4±1.3% F(2.48)=52.2; p<0.001).

CONCLUSION

CMR strain analysis detects early systolic and diastolic strain impairment in AL patients lacking qualitative LGE enhancement.

Three-dimensional maximum principal strain using cardiac computed tomography for identification of myocardial infarction

OBJECTIVES

To evaluate the feasibility of three-dimensional (3D) maximum principal strain (MP-strain) derived from cardiac computed tomography (CT) for detecting myocardial infarction (MI).

METHODS

Forty-three patients who underwent cardiac CT and magnetic resonance imaging (MRI) were retrospectively selected. Using the voxel tracking of motion coherence algorithm, the peak CT MP-strain was measured using the 16-segment model. With the trans-mural extent of late gadolinium enhancement (LGE) and the distance from MI, all segments were classified into four groups (infarcted, border, adjacent, and remote segments); infarcted and border segments were defined as MI with LGE positive. Diagnostic performance of MP-strain for detecting MI was compared with per cent systolic wall thickening (%SWT) assessed by MRI using receiver-operating characteristic curve analysis at a segment level.

RESULTS

Of 672 segments excluding16 segments influenced by artefacts, 193 were diagnosed as MI. Sensitivity and specificity of peak MP-strain to identify MI were 81 % [95 % confidence interval (95 % CI): 74-88 %] and 86 % (81-92 %) compared with %SWT: 76 % (60-95 %) and 68 % (48-84 %), respectively. The area under the curve of peak MP-strain was superior to %SWT [0.90 (0.87-0.93) vs. 0.80 (0.76-0.83), p < 0.05].

CONCLUSIONS

CT MP-strain has a potential to provide incremental value to coronary CT angiography for detecting MI.

KEY POINTS

• CT MP-strain allows for three-dimensional assessment of regional cardiac function. • CT-MP strain has high diagnostic accuracy for detecting myocardial infarction. • CT-MP strain may assist in tissue characterisation of myocardium assessed by LGE-MRI. • CT-MP strain provides incremental values to coronary CTA for detecting myocardial infarction.

Novel Cardiac Magnetic Resonance Feature Tracking (CMR-FT) Analysis for Detection of Myocardial Fibrosis in Pediatric Hypertrophic Cardiomyopathy

Myocardial fibrosis is a risk factor for sudden cardiac death in hypertrophic cardiomyopathy (HCM) and is conventionally identified by cardiac magnetic resonance imaging (CMR) using late gadolinium enhancement (LGE). This study evaluates utility of a novel 16-segment CMR feature tracking (CMR-FT) technique for measuring left ventricular (LV) strain (S) and strain rate (SR) on non-contrast cine images to detect myocardial fibrosis in pediatric HCM. We hypothesized that CMR-FT-derived S and SR will accurately differentiate HCM patients with and without myocardial fibrosis. Consecutive children with HCM who underwent CMR with LGE at our institution from 2006 to 2014 were included. Global and regional longitudinal, radial and circumferential S and SR of the LV in 2D and 3D were obtained using a CMR-FT software. Comparisons were made between HCM patients with (+LGE) and without (-LGE) delayed enhancement. Of the 29 HCM patients (mean age 13.5 ± 6.1 years; 52 % males), 11 (40 %) patients (mean age 17.5 ± 8.4 years) had +LGE. Global longitudinal, circumferential and radial S and SR were lower in +LGE compared to -LGE patients, in both 2D and 3D. Regional analysis revealed lower segmental S and SR in the septum with fibrosis compared to free wall without fibrosis. A global longitudinal S of ≤ -12.8 had 91 % sensitivity and 89 % specificity for detection of LGE. In pediatric HCM patients with myocardial fibrosis, global LV longitudinal, circumferential and radial S and SR were reduced, specifically in areas of fibrosis. A global longitudinal S of ≤ -12.8 detected patients with fibrosis with high degree of accuracy. This novel CMR-FT technique may be useful to identify myocardial fibrosis and risk-stratify pediatric HCM without use of contrast agents.

Effect of free-breathing on left ventricular rotational mechanics in healthy subjects and patients with duchenne muscular dystrophy

PURPOSE

Cardiovascular magnetic resonance imaging exams can be performed during free-breathing. This may be especially important for boys with Duchenne muscular dystrophy (DMD) given their frequently limited breath-hold abilities. The impact of the respiratory compensation method on quantitative measurements of left ventricular (LV) rotational mechanics is incompletely understood. The purpose of this study was to evaluate differences in LV rotational mechanics acquired during breath-holding (BH), free-breathing with averaging (AVG), and free-breathing with respiratory bellows gating (BEL).

METHODS

LV short-axis tagged images from healthy subjects (N = 16) and DMD patients (N = 5) were acquired with BH, AVG, and BEL. LV twist and circumferential-longitudinal shear (CL-shear) angle were measured using the Fourier Analysis of STimulated echoes (FAST) method.

RESULTS

Peak LV twist estimates using BEL were significantly lower compared with BH in both healthy subjects (10.2 ± 3.6 ° versus 12.9 ± 2.3 °, P = 0.003) and patients with DMD (8.6 ± 3.6 ° versus 10.5 ± 3.6 °, P = 0.004). AVG results were in between BEL and BH. No significant differences in CL-shear were detected between BEL and BH.

CONCLUSION

Breath-holding directly affects estimates of peak LV twist, but not CL-shear. Using a free-breathing strategy for the evaluation of cardiac function is important for intrasubject longitudinal studies, intersubject comparisons, and multicenter trials for patients with DMD. Magn Reson Med 77:864-869, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Systolic and diastolic myocardial mechanics in hypertrophic cardiomyopathy and their link to the extent of hypertrophy, replacement fibrosis and interstitial fibrosis

Aim of the present study was to investigate the relations between myocardial mechanics and the extent of hypertrophy and fibrosis in hypertrophic cardiomyopathy (HCM). Forty-five consecutive patients with HCM and 15 subjects without structural heart disease were included. Cardiac magnetic resonance with late gadolinium enhancement (LGE) imaging was performed to evaluate biventricular function, LV mass index and presence/extent of LGE, expression of replacement fibrosis. Myocardial T1 relaxation, a surrogate of interstitial fibrosis, was measured from Look-Locker sequence. Feature-tracking analysis was applied to LV basal, mid and apical short-axis images to assess systolic and diastolic global LV circumferential strain (CS) and strain rate (CSr). Peak systolic CS and CSr were significantly higher among HCM patients as compared to control subjects (p = 0.015 and p = 0.007, respectively). The ratio of peak CSr during early filling to peak systolic CSr was significantly lower among HCM patients (p = 0.002). At multivariate linear regression analysis, LV mass index (p < 0.001) and %LV LGE (p = 0.011) were significantly and independently related to peak systolic CS; LV mass index (p < 0.001) and %LV LGE (p = 0.023) were significantly and independently related to peak systolic CSr; %LV LGE (p = 0.021) and T1 ratio (p = 0.006) were significantly and independently related to the ratio of peak CSr during early filling to peak systolic CSr. LV systolic mechanics are enhanced and LV diastolic mechanics are impaired in HCM. Extent of hypertrophy and replacement fibrosis influence the LV systolic mechanics while extent of replacement fibrosis and interstitial fibrosis influence the LV diastolic mechanics.

Role of multimodality cardiac imaging in the management of patients with hypertrophic cardiomyopathy: an expert consensus of the European Association of Cardiovascular Imaging Endorsed by the Saudi Heart Association

Taking into account the complexity and limitations of clinical assessment in hypertrophic cardiomyopathy (HCM), imaging techniques play an essential role in the evaluation of patients with this disease. Thus, in HCM patients, imaging provides solutions for most clinical needs, from diagnosis to prognosis and risk stratification, from anatomical and functional assessment to ischaemia detection, from metabolic evaluation to monitoring of treatment modalities, from staging and clinical profiles to follow-up, and from family screening and preclinical diagnosis to differential diagnosis. Accordingly, a multimodality imaging (MMI) approach (including echocardiography, cardiac magnetic resonance, cardiac computed tomography, and cardiac nuclear imaging) is encouraged in the assessment of these patients. The choice of which technique to use should be based on a broad perspective and expert knowledge of what each technique has to offer, including its specific advantages and disadvantages. Experts in different imaging techniques should collaborate and the different methods should be seen as complementary, not as competitors. Each test must be selected in an integrated and rational way in order to provide clear answers to specific clinical questions and problems, trying to avoid redundant and duplicated information, taking into account its availability, benefits, risks, and cost.

Characterization and quantification of curvature using independent coordinates method in the human left ventricle by magnetic resonance imaging to identify the morphology subtype of hypertrophy cardiomyopathy

The patterns of ventricular hypertrophy are critical determinants of blood flow and function, but are variable. Therefore, it is clinically relevant to assess the hypertrophic shape patterns to better characterize and identify the morphological subtypes. We proposed and developed an independent coordinates method (ICM) to quantify the regional shape of the left ventricle in terms of curvature. 19 normal subjects and 5 HCM (hypertrophic cardiomyopathy) patients with different morphological subtype (i.e., septal hypertrophy, mid-ventricular hypertrophy, reverse curvature septum hypertrophy and sigmoid septum hypertrophy) were recruited and underwent magnetic resonance scans. The curvature along the endocardial and epicardial surface was computed using ICM method and was compared in HCM patients against normal subjects. The results showed that curvature plots are variable in different morphological subtype. The curvature pattern demonstrated the utilities in delineating different subtype. In conclusion, ICM method to quantify regional curvature of the left ventricle from magnetic resonance imaging are feasible in normal subjects and those with hypertrophy cardiomyopathy, which may serve as a novel approach to depict local shape of the left ventricle and to assess the morphological subtype in clinical practice.

Ventricular mechanics: techniques and applications

Magnetic resonance assessment of regional myocardial function is a novel potentially important tool for early identification of cardiac pathology. Many cardiac magnetic resonance techniques have been developed for detection and quantification of regional strain abnormalities including steady-state free-precession CINE, tagging, displacement encoding with stimulated echoes, strain encoding imaging, and feature tracking. Potential clinical applications of magnetic resonance strain imaging include early detection of systolic dysfunction in heart failure patients with both ischemic and nonischemic etiologies.

Probing dynamic myocardial microstructure with cardiac magnetic resonance diffusion tensor imaging

This article is an invited editorial comment on the paper entitled "In vivo cardiovascular magnetic resonance diffusion tensor imaging shows evidence of abnormal myocardial laminar orientations and mobility in hypertrophic cardiomyopathy" by Ferreira et al., and published as Journal of Cardiovascular Magnetic Resonance 2014; 16:87.

Comparison of magnetic resonance feature tracking with harmonic phase imaging analysis (CSPAMM) for assessment of global and regional diastolic function

AIMS

Complex post-processing is required for strain-derived assessment of diastolic dysfunction (DD) using CMR-tagging (TAG). Feature-tracking (FT), allows for rapid systolic strain assessment using conventional steady-state free precession (SSFP)-Cine sequences. Aim of this study was to investigate whether FT may be employed for the clinically applicable quantification of DD.

METHODS AND RESULTS

40 individuals (20 patients with DD I-III°, 20 controls) were investigated. CSPAMM and SSFP-Cine sequences were acquired in identical short-axis locations. Global and regional early diastolic strain rate (EDSR), peak diastolic strain rate (PDSR), twist, untwist and torsion were calculated from tagged and SSFP-Cine datasets. DD indices were compared, intra- as well inter-observer variability assessed.

RESULTS

for global EDSR correlated strongly (r=0.94), revealed good agreement and no significant differences between both methods. Correlation for regional EDSR was lower, results differed significantly in the anterior wall (p<0.05). Correlation for PDSR was moderate (r=0.63), results in the healthy control group differed significantly (p<0.05). FT derived rotational indices correlated poorly with TAG (twist: r=0.28; untwist: r=0.02; torsion: r=0.26), subgroup analysis revealed significant differences (p<0.05). Intra- and inter-observer variability for FT derived global EDSR and PDSR were comparable to TAG, but significantly higher for regional EDSR and rotational indices.

CONCLUSION

FT derived global EDSR allows for rapid clinical determination of diastolic dysfunction, revealing good agreement with TAG and low intra- as well as interobserver variability. However, TAG analysis not only yields higher accuracy and reproducibility of global- and regional diastolic strain, but also delivers reliable information about diastolic rotational and untwisting dynamics.

Complementary radial tagging for improved myocardial tagging contrast

PURPOSE

To develop and evaluate complementary radial tagging (CRT) for improved myocardial tagging contrast.

METHODS

We sought to develop and evaluate CRT, which aims to preserve the radial tag contrast throughout the cardiac cycle. Similar to complementary spatial modulation of magnetization, CRT acquires two sets of images with a phase shift in the tag pattern. The combination of a ramped imaging flip angle and image subtraction enhances tag contrast throughout the cardiac cycle. The proposed CRT technique uses a small table shift away from the isocenter to improve the uniformity of the radial tag pattern. We provide a mathematical solution for the optimal table shift and validate the solution in using a retrospective analysis of images from 500 patients in the Cardiac Atlas Project database.

RESULTS

CRT simulations, phantom experiments, and in vivo images all demonstrate the improved tag contrast of CRT compared to RT. The retrospective evaluation demonstrated that acceptable CRT images could be acquired in over 98% of the clinical exams.

CONCLUSION

The CRT technique improves radial tag contrast throughout the cardiac cycle and should produce high quality tag patterns in nearly all patients.

Diastolic function assessed from tagged MRI predicts heart failure and atrial fibrillation over an 8-year follow-up period: the multi-ethnic study of atherosclerosis

OBJECTIVES

The strain relaxation index (SRI), a novel diastolic functional parameter derived from tagged magnetic resonance imaging (MRI), is used to assess myocardial deformation during left ventricular relaxation. We investigated whether diastolic function indexed by SRI predicts heart failure (HF) and atrial fibrillation (AF) over an 8-year follow-up.

METHODS

As a part of the multi-ethnic study of atherosclerosis, 1544 participants free of known cardiovascular disease (CVD) underwent tagged MRI in 2000-02. Harmonic phase analysis was used to compute circumferential strain. Standard parameters, early diastolic strain rate (EDSR) and the peak torsion recoil rate were calculated. An SRI was calculated as difference between post-systolic and systolic times of the strain peaks, divided by the EDSR peak. It was normalized by the total interval of relaxation. Over an 8-year follow-up period, we defined AF (n = 57) or HF (n = 36) as combined (n = 80) end-points. Cox regression assessed the ability of SRI to predict events adjusted for risk factors and markers of subclinical disease. Integrated discrimination index (IDI) and net reclassification index (NRI) of SRI, compared with conventional indices, were also assessed.

RESULTS

The hazard ratio for SRI remained significant for the combined HF and AF end-points as well as for HF alone after adjustment. For the combined end-point, IDI was 1.5% (P < 0.05) and NRI was 11.4% (P < 0.05) for SRI. Finally, SRI was more robust than all other existing cardiovascular magnetic resonance diastolic functional parameters.

CONCLUSION

SRI predicts HF and AF over an 8-year follow-up period in a large population free of known CVD, independent of established risk factors and markers of subclinical CVD.

Consistent regional heterogeneity of passive diastolic stretch and systolic deformation in the healthy heart: age-related changes in left ventricle contractility

The consistency of the normal spatial distribution of segmental passive stretch (PreS) and systolic strain (SS) within the left ventricle was investigated and a recently proposed echocardiographic estimate of left ventricular (LV) contractility was used to detect contractility changes with age. Hereto, in 54 healthy subjects, segmental PreS and SS were measured on tissue Doppler images of six left ventricle walls. For each subject, a linear regression line was estimated through the segmental PreS and SS values. The slopes and intercepts of this PreS-SS relationship did not differ between age groups, suggesting no changes in LV contractility with age. Moreover, a consistent regional distribution of PreS was observed, with the highest values measured in the septum, resulting in a similar distribution of SS as a direct consequence of the Frank-Starling mechanism.

Advances of cardiovascular MRI in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic disease characterized by abnormal myocardial hypertrophy, which can lead to a wide clinical spectrum, including sudden cardiac death and heart failure. Cardiac MRI has a significant role in establishing the diagnosis of HCM. In the three principal management issues related to HCM; testing of family members of affected individuals; assessing the risk of sudden cardiac death from lethal ventricular arrhythmias; and selection of appropriate treatments for left ventricular outflow obstruction, cardiac MRI has established or emerging roles.

Quantitative assessment of systolic and diastolic left ventricular twist using Fourier Analysis of Stimulated echoes (FAST) and CSPAMM

PURPOSE

To evaluate Fourier Analysis of Stimulated echoes (FAST) and CSPAMM for the quantification of left ventricular (LV) systolic and diastolic function and compare it with the previously validated FAST+SPAMM technique.

MATERIALS AND METHODS

LV short-axis tagged images were acquired with CSPAMM and SPAMM in healthy volunteers (n = 13). The FAST method was used to automatically estimate LV systolic and diastolic twist parameters from rotation of the stimulated echo and stimulated anti-echo about the middle of k-space subsequent to ∼3 min of user interaction.

RESULTS

There was no significant difference between measures obtained for FAST+CSPAMM and FAST+SPAMM for mean peak twist (13.5 ± 2.7° versus 11.9 ± 4.0°), torsion (3.4 ± 0.8°/cm versus 2.9 ± 1.0°/cm), twisting rate (76.8 ± 22.2°/s versus 68.2 ± 23.4°/s), untwisting rate (-102.7 ± 24.6°/s versus -106.6 ± 32.4°/s), normalized untwisting rate (-7.9 ± 2.2/s versus -9.9 ± 4.4/s), and time of peak twist (279 ± 23 ms versus 293 ± 25 ms) (all P > 0.01). FAST+CSPAMM also provided measures of duration of untwisting (148 ± 21 ms) and the ratio of rapid untwist to peak twist (0.8 ± 0.3). Bland-Altman analysis of FAST+CSPAMM and FAST+SPAMM twist data demonstrates excellent agreement with a bias of 1.1° and 95% confidence intervals of [-3.3°, 5.2°].

CONCLUSION

FAST+CSPAMM is a semi-automated method that provides a quick and quantitative assessment of LV systolic and diastolic twist and torsion.

MR assessment of regional myocardial mechanics

Regional myocardial function can be measured by several MR techniques including tissue tagging, phase velocity mapping, and more recently, displacement encoding with stimulated echoes (DENSE) and strain encoding (SENC). Each of these techniques was developed separately and has undergone significant change since its original implementation. As a result, in the current literature, the common features and the differences between the techniques and what they measure are often unclear and confusing. This review article delivers an extensively referenced introductory text which clarifies the current methodology from the starting point of the Bloch equations. By doing this in a consistent way for each method, the similarities and differences between them are highlighted. In addition, their capabilities and limitations are discussed, together with their relative advantages and disadvantages. While the focus is on sequence design and development, the principal parameters measured by each technique are also summarized, together with brief results, with the reader being directed to the extensive literature on data processing and clinical applications for more detail.

Accurate two-dimensional cardiac strain calculation using adaptive windowed Fourier transform and Gabor wavelet transform

PURPOSE

Cardiac strain calculated from tagged magnetic resonance (MR) images provides clinicians information about abnormalities of heart-wall motion in patients. It is important to develop an accurate method to determine the cardiac strain efficiently. An adaptive windowed harmonic phase (AWHARP) method is proposed for cardiac strain calculation.

MATERIALS AND METHODS

AWHARP is based on adaptive windowed Fourier transform (AWFT) and 2D Gabor wavelet transform (2D-GWT). The AWFT provides a spatially varying representation of the signal spectra, which allows the harmonic phase (HARP) image to be extracted with high accuracy. Instantaneous spatial frequencies are calculated using 2D-GWT, and the widths of the adaptive windows are then determined according to the instantaneous spatial frequencies for multi-resolution analysis of phase extraction. The proposed method was studied using simulated images and patients' MR images. Both single tagged images (SPAMM) and subtracted tagged images (CSPAMM) were generated using our simulation method, and their results calculated using AWHARP and HARP methods were compared. Normal and pathological tagged MR images were also processed to evaluate the performance of our method.

RESULTS

Our experimental results show that the accuracies of phase and strain images calculated using the AWHARP method are higher than that calculated using the HARP method especially for large tag line deformation. The improvement in accuracies can be up to 3.2 strain (E1) and 17.3 calculation from MR images reveals that the cardiac strain in the end-systolic state is significantly reduced for patients with hypertrophic cardiomyopathy (HCM) compared to that of healthy subjects.

CONCLUSION

The proposed AWHARP is an accurate and efficient method for cardiac strain estimation from MR images. This new algorithm can help clinicians to detect left ventricle dysfunctions and myocardial diseases with accurate cardiac strain analysis.

Myocardial strains from 3D displacement encoded magnetic resonance imaging

Background

The ability to measure and quantify myocardial motion and deformation provides a useful tool to assist in the diagnosis, prognosis and management of heart disease. The recent development of magnetic resonance imaging methods, such as harmonic phase analysis of tagging and displacement encoding with stimulated echoes (DENSE), make detailed non-invasive 3D kinematic analyses of human myocardium possible in the clinic and for research purposes. A robust analysis method is required, however.

Methods

We propose to estimate strain using a polynomial function which produces local models of the displacement field obtained with DENSE. Given a specific polynomial order, the model is obtained as the least squares fit of the acquired displacement field. These local models are subsequently used to produce estimates of the full strain tensor.

Results

The proposed method is evaluated on a numerical phantom as well as in vivo on a healthy human heart. The evaluation showed that the proposed method produced accurate results and showed low sensitivity to noise in the numerical phantom. The method was also demonstrated in vivo by assessment of the full strain tensor and to resolve transmural strain variations.

Conclusions

Strain estimation within a 3D myocardial volume based on polynomial functions yields accurate and robust results when validated on an analytical model. The polynomial field is capable of resolving the measured material positions from the in vivo data, and the obtained in vivo strains values agree with previously reported myocardial strains in normal human hearts.

Cardiac myosin binding protein C insufficiency leads to early onset of mechanical dysfunction

BACKGROUND

Decreased expression of cardiac myosin binding protein C (cMyBPC) as a result of genetic mutations may contribute to the development of hypertrophic cardiomyopathy (HCM); however, the mechanisms that link cMyBPC expression and HCM development, especially contractile dysfunction, remain unclear.

METHODS AND RESULTS

We evaluated cardiac mechanical function in vitro and in vivo in young mice (8-10 weeks of age) carrying no functional cMyBPC alleles (cMyBPC(-/-)) or 1 functional cMyBPC allele (cMyBPC(±)). Skinned myocardium isolated from cMyBPC(-/-) hearts displayed significant accelerations in stretch activation cross-bridge kinetics. Cardiac MRI studies revealed severely depressed in vivo left ventricular (LV) magnitude and rates of LV wall strain and torsion compared with wild-type (WT) mice. Heterozygous cMyBPC(±) hearts expressed 23±5% less cMyBPC than WT hearts but did not display overt hypertrophy. Skinned myocardium isolated from cMyBPC(±) hearts displayed small accelerations in the rate of stretch induced cross-bridge recruitment. MRI measurements revealed reductions in LV torsion and circumferential strain, as well reduced circumferential strain rates in early systole and diastole.

CONCLUSIONS

Modest decreases in cMyBPC expression in the mouse heart result in early-onset subtle changes in cross-bridge kinetics and in vivo LV mechanical function, which could contribute to the development of HCM later in life.

Role of multimodality imaging in ischemic and non-ischemic cardiomyopathy

Chronic heart failure (CHF) is a major and growing problem in the western hemisphere, affecting about 5 million patients in the United States. In daily practice patients with left ventricular systolic dysfunction (LVSD) and significant angiographic coronary artery disease (CAD) are felt to have an ischemic cardiomyopathy (ICMP) and those without CAD or mild-moderate CAD out of proportion to the extent of LVSD are felt to have a non-ischemic cardiomyopathy (NICMP). Although invasive coronary angiography is the gold standard for the diagnosis of CAD, recent advances in non-invasive imaging have created multiple options for evaluating ICMP and NICMP. This review details the role of cardiac imaging in the diagnosis of ICMP and NICMP and outlines an algorithm of use of non-invasive tests in asymtomatic LVSD and symptomatic heart failure.

Left ventricular diastolic function in type 2 diabetes mellitus is associated with myocardial triglyceride content but not with impaired myocardial perfusion reserve

PURPOSE

To study myocardial perfusion reserve and myocellular metabolic alterations indicated by triglyceride content as possible causes of diastolic dysfunction in patients with type 2 diabetes mellitus, preserved systolic function, and without clinically evident coronary artery disease.

MATERIALS AND METHODS

Patients with type 2 diabetes mellitus (n = 42) underwent cardiac magnetic resonance (CMR) for quantification of 1) myocardial contractility by strain-encoded MR (SENC); 2) myocardial triglyceride content by proton magnetic resonance spectroscopy ((1) H-MRS); and 3) myocardial perfusion reserve during pharmacologic hyperemia. Age-matched healthy volunteers (n = 16) also underwent CMR to acquire normal values for myocardial strain and perfusion reserve.

RESULTS

Stress CMR procedures were successfully performed in all subjects, and no regional inducible perfusion defects were observed in type 2 diabetes mellitus patients. Diastolic strain rate and myocardial perfusion reserve were significantly impaired in patients with type 2 diabetes mellitus compared to control subjects (P < 0.001 for both). Interestingly, impaired diastolic function in type 2 diabetes mellitus was not associated with impaired myocardial perfusion reserve (r = 0.12, P = NS). Conversely a significant association was observed between diastolic dysfunction and myocardial triglyceride content (r = -0.71, P < 0.001), which proved to be independent of age, gender, diabetes duration, blood pressure, and fasting blood glucose.

CONCLUSION

Myocardial steatosis may represent an early marker of diabetic heart disease, triggering subclinical myocardial dysfunction irrespective of myocardial perfusion reserve.

Fourier analysis of STimulated echoes (FAST) for the quantitative analysis of left ventricular twist

PURPOSE

To validate a novel method for the rapid and facile quantification of left ventricular (LV) twist from tagged magnetic resonance images and demonstrate the potential clinical utility in a series of 20 healthy volunteers.

MATERIALS AND METHODS

Cardiac magnetic resonance imaging (MRI) short-axis images were acquired with tissue tagging in 20 healthy subjects and six canines. The tagged images were processed using a novel Fourier Analysis of the STimulated echoes (FAST) method, which uses a series of Fourier-space operations to measure LV twist with limited user interaction. A subset of eight healthy subjects and the canine data were compared to results from previously validated "gold standard" software (FindTags). Interobserver and intraobserver coefficients of variation (CV(INTER) and CV(INTRA) ), linear regression, and Bland-Altman analyses were used to assess agreement between observers and methods.

RESULTS

CV(INTRA) for peak systolic twist (2.9% and 2.6%) and CV(INTER) (4.3% and 4.2%) were all small. Linear regression analysis of the FAST and FindTags twist values indicated very good agreement in healthy subjects (R = 0.91) and in canines (R = 0.95). Bland-Altman comparison of the FAST and FindTags twist results indicated excellent agreement in healthy subjects (bias of -0.5°, 95% confidence intervals (-4.3°, 4.3°)) and canines (bias of 0.2°, 95% confidence intervals (-2.7°, 3.1°)). Peak systolic twist in healthy subjects averaged 10.5 ± 1.9° degrees.

CONCLUSION

The FAST method for quantifying LV twist produces results that are not significantly different from the current "gold standard" in a fraction of the user interaction time and has demonstrated feasibility in human subjects.

Effects of steroids and angiotensin converting enzyme inhibition on circumferential strain in boys with Duchenne muscular dystrophy: a cross-sectional and longitudinal study utilizing cardiovascular magnetic resonance

BACKGROUND

Steroid use has prolonged ambulation in Duchenne muscular dystrophy (DMD) and combined with advances in respiratory care overall management has improved such that cardiac manifestations have become the major cause of death. Unfortunately, there is no consensus for DMD-associated cardiac disease management. Our purpose was to assess effects of steroid use alone or in combination with angiotensin converting enzyme inhibitors (ACEI) or angiotension receptor blocker (ARB) on cardiovascular magnetic resonance (CMR) derived circumferential strain (εcc).

METHODS

We used CMR to assess effects of corticosteroids alone (Group A) or in combination with ACEI or ARB (Group B) on heart rate (HR), left ventricular ejection fraction (LVEF), mass (LVM), end diastolic volume (LVEDV) and circumferential strain (εcc) in a cohort of 171 DMD patients >5 years of age. Treatment decisions were made independently by physicians at both our institution and referral centers and not based on CMR results.

RESULTS

Patients in Group A (114 studies) were younger than those in Group B (92 studies)(10 ± 2.4 vs. 12.4 ± 3.2 years, p < 0.0001), but HR, LVEF, LVEDV and LVM were not different. Although εcc magnitude was lower in Group B than Group A (-13.8 ± 1.9 vs. -12.8 ± 2.0, p = 0.0004), age correction using covariance analysis eliminated this effect. In a subset of patients who underwent serial CMR exams with an inter-study time of ~15 months, εcc worsened regardless of treatment group.

CONCLUSIONS

These results support the need for prospective clinical trials to identify more effective treatment regimens for DMD associated cardiac disease.

Myocardial tagging by cardiovascular magnetic resonance: evolution of techniques--pulse sequences, analysis algorithms, and applications

Cardiovascular magnetic resonance (CMR) tagging has been established as an essential technique for measuring regional myocardial function. It allows quantification of local intramyocardial motion measures, e.g. strain and strain rate. The invention of CMR tagging came in the late eighties, where the technique allowed for the first time for visualizing transmural myocardial movement without having to implant physical markers. This new idea opened the door for a series of developments and improvements that continue up to the present time. Different tagging techniques are currently available that are more extensive, improved, and sophisticated than they were twenty years ago. Each of these techniques has different versions for improved resolution, signal-to-noise ratio (SNR), scan time, anatomical coverage, three-dimensional capability, and image quality. The tagging techniques covered in this article can be broadly divided into two main categories: 1) Basic techniques, which include magnetization saturation, spatial modulation of magnetization (SPAMM), delay alternating with nutations for tailored excitation (DANTE), and complementary SPAMM (CSPAMM); and 2) Advanced techniques, which include harmonic phase (HARP), displacement encoding with stimulated echoes (DENSE), and strain encoding (SENC). Although most of these techniques were developed by separate groups and evolved from different backgrounds, they are in fact closely related to each other, and they can be interpreted from more than one perspective. Some of these techniques even followed parallel paths of developments, as illustrated in the article. As each technique has its own advantages, some efforts have been made to combine different techniques together for improved image quality or composite information acquisition. In this review, different developments in pulse sequences and related image processing techniques are described along with the necessities that led to their invention, which makes this article easy to read and the covered techniques easy to follow. Major studies that applied CMR tagging for studying myocardial mechanics are also summarized. Finally, the current article includes a plethora of ideas and techniques with over 300 references that motivate the reader to think about the future of CMR tagging.

Heterogeneity of intramural function in hypertrophic cardiomyopathy: mechanistic insights from MRI late gadolinium enhancement and high-resolution displacement encoding with stimulated echoes strain maps

BACKGROUND

In hypertrophic cardiomyopathy (HCM), myocardial abnormalities are commonly heterogeneous. Two patterns of late gadolinium enhancement (LGE) have been reported: a bright "confluent" and an intermediate intensity abnormality termed "diffuse," each representing different degrees of myocardial scarring. We used MRI to study the relation between intramural cardiac function and the extent of fibrosis in HCM. The aim of this study was to determine whether excess collagen or myocardial scarring, as determined by LGE MRI, are the primary mechanisms leading to heterogeneous regional contractile function in patients with HCM.

METHODS AND RESULTS

Intramural left ventricular strain, transmural left ventricular function, and regions of myocardial fibrosis/scarring were imaged in 22 patients with HCM, using displacement encoding with stimulated echoes (DENSE), cine MRI, and LGE. DENSE systolic strain maps were qualitatively and quantitatively compared with LGE images. Intramural systolic strain by DENSE was significantly depressed within areas of confluent and diffuse LGE but also in the core of the most hypertrophic nonenhanced segment (all P < 0.001 versus nonhypertrophied segments). DENSE demonstrated an unexpected inner rim of largely preserved contractile function and a noncontracting outer wall within hypertrophic segments in 91% of patients.

CONCLUSIONS

LGE predicted some but not all of the heterogeneity of intramural contractile abnormalities. This indicates that myocardial scarring or excess interstitial collagen deposition does not fully explain the observed contractile heterogeneity in HCM. Thus, myofibril disarray or other nonfibrotic processes affect systolic function in a large number of patients with HCM.