Strain-encoded (SENC) magnetic resonance imaging to evaluate regional heterogeneity of myocardial strain in healthy volunteers: Comparison with conventional tagging

Prognostic impact of MRI-derived feature tracking myocardial strain in patients with non-ischaemic dilated cardiomyopathy: a systematic review and meta-analysis

AIM

To evaluate the clinical utility of feature tracking (FT)-derived myocardial strain in patients with non-ischaemic dilated cardiomyopathy (NIDCM).

MATERIALS AND METHODS

Electronic database searches of PubMed, Web of Science Core Collection, Cochrane advanced search, and EMBASE were performed. Studies on NIDCM were divided into categories according to left ventricular ejection fraction (LVEF; <30%, 30-40%, >40%), and correlations between strains and prevalence of late gadolinium enhancement (LGE) were evaluated by weighted correlation coefficients. Global longitudinal strain (GLS) hazard ratios were also integrated for prediction of future adverse events.

RESULTS

The present meta-analysis analysed data from 5,767 patients with NIDCM from 30 eligible studies. GLS and global circumferential strain significantly differed across the three LVEF categories (all p<0.05); however, global radial strain did not. Only GLS showed a strong correlation with the prevalence of LGE (Spearman's correlation coefficient = 0.61). The pooled HR of GLS for predicting adverse events was 1.15 (95% confidence interval [CI]: 1.07-1.23, p<0.001).

CONCLUSION

In this meta-analysis, FT-derived GLS was strongly correlated with myocardial fibrosis and was an important predictor of future adverse events. These results suggest that FT-derived GLS may be useful in the pathological evaluation and risk stratification of NIDCM.

Layer-specific fast strain-encoded cardiac magnetic resonance imaging aids in the identification and discrimination of acute myocardial injury: a prospective proof-of-concept study

BACKGROUND

Acute myocardial injury is a common diagnosis in the emergency department and differential diagnoses are numerous. Cardiac magnetic resonance (CMR) strain sequences, such as fast strain ENCoded (fSENC), are early predictors of myocardial function loss. This study assessed the potential diagnostic and prognostic benefits of a layer-specific approach.

METHODS

For this prospective study, patients in the emergency department fulfilling rule-in criteria for non-ST-elevation myocardial infarction (NSTEMI) received an ultra-fast fSENC CMR. Volunteers without cardiac diseases (controls) were recruited for comparison. Measurements were performed in a single heartbeat acquisition to measure global longitudinal strain (GLS) and segmental longitudinal strain and dysfunctional segments. The GLS was measured in two layers and a difference (GLSdifference = GLSepicardial - GLSendocardial) was calculated. The performance of those strain features was compared to standard care (physical examination, cardiac biomarkers, electrocardiogram). According to the final diagnosis after discharge, patients were divided into groups and followed up for 2 years.

RESULTS

A total of 114 participants, including 50 controls, were included. The 64 patients (51 male) were divided into a NSTEMI (25), myocarditis (16), and other myocardial injury group (23). GLS served as a potent predictor of myocardial injury (area under the curve (AUC) 91.8%). The GLSdifference provided an excellent diagnostic performance to identify a NSTEMI (AUC 83.2%), further improved by including dysfunctional segments (AUC 87.5%, p = 0.01). An optimal test was achieved by adding fSENC to standard care (AUC 95.5%, sensitivity 96.0%, specificity 86.5%, p = 0.03). No death occurred in 2 years for patients with normal GLS and ≤5 dysfunctional segments, while three patients died that showed abnormal GLS or >5 dysfunctional segments.

CONCLUSIONS

Layer-specific strain is a potential new marker with high diagnostic performance in the identification and differentiation of acute myocardial injuries.

Localized strain characterization of cardiomyopathy in Duchenne muscular dystrophy using novel 4D kinematic analysis of cine cardiovascular magnetic resonance

BACKGROUND

Cardiomyopathy (CMP) is the most common cause of mortality in Duchenne muscular dystrophy (DMD), though the age of onset and clinical progression vary. We applied a novel 4D (3D + time) strain analysis method using cine cardiovascular magnetic resonance (CMR) imaging data to determine if localized strain metrics derived from 4D image analysis would be sensitive and specific for characterizing DMD CMP.

METHODS

We analyzed short-axis cine CMR image stacks from 43 DMD patients (median age: 12.23 yrs [10.6-16.5]; [interquartile range]) and 25 male healthy controls (median age: 16.2 yrs [13.3-20.7]). A subset of 25 male DMD patients age-matched to the controls (median age: 15.7 yrs [14.0-17.8]) was used for comparative metrics. CMR images were compiled into 4D sequences for feature-tracking strain analysis using custom-built software. Unpaired t-test and receiver operator characteristic area under the curve (AUC) analysis were used to determine statistical significance. Spearman's rho was used to determine correlation.

RESULTS

DMD patients had a range of CMP severity: 15 (35% of total) had left ventricular ejection fraction (LVEF) > 55% with no findings of myocardial late gadolinium enhancement (LGE), 15 (35%) had findings of LGE with LVEF > 55% and 13 (30%) had LGE with LVEF < 55%. The magnitude of the peak basal circumferential strain, basal radial strain, and basal surface area strain were all significantly decreased in DMD patients relative to healthy controls (p < 0.001) with AUC values of 0.80, 0.89, and 0.84 respectively for peak strain and 0.96, 0.91, and 0.98 respectively for systolic strain rate. Peak basal radial strain, basal radial systolic strain rate, and basal circumferential systolic strain rate magnitude values were also significantly decreased in mild CMP (No LGE, LVEF > 55%) compared to a healthy control group (p < 0.001 for all). Surface area strain significantly correlated with LVEF and extracellular volume (ECV) respectively in the basal (rho = - 0.45, 0.40), mid (rho = - 0.46, 0.46), and apical (rho = - 0.42, 0.47) regions.

CONCLUSION

Strain analysis of 3D cine CMR images in DMD CMP patients generates localized kinematic parameters that strongly differentiate disease from control and correlate with LVEF and ECV.

Myocardial strain imaging in Duchenne muscular dystrophy

Cardiomyopathy (CM) is the leading cause of death for individuals with Duchenne muscular dystrophy (DMD). While DMD CM progresses rapidly and fatally for some in teenage years, others can live relatively symptom-free into their thirties or forties. Because CM progression is variable, there is a critical need for biomarkers to detect early onset and rapid progression. Despite recent advances in imaging and analysis, there are still no reliable methods to detect the onset or progression rate of DMD CM. Cardiac strain imaging is a promising technique that has proven valuable in DMD CM assessment, though much more work has been done in adult CM patients. In this review, we address the role of strain imaging in DMD, the mechanical and functional parameters used for clinical assessment, and discuss the gaps where emerging imaging techniques could help better characterize CM progression in DMD. Prominent among these emerging techniques are strain assessment from 3D imaging and development of deep learning algorithms for automated strain assessment. Improved techniques in tracking the progression of CM may help to bridge a crucial gap in optimizing clinical treatment for this devastating disease and pave the way for future research and innovation through the definition of robust imaging biomarkers and clinical trial endpoints.

A head-to-head comparison of fast-SENC and feature tracking to LV long axis strain for assessment of myocardial deformation in chest pain patients

BACKGROUND

Myocardial strain imaging has gained importance in cardiac magnetic resonance (CMR) imaging in recent years as an even more sensitive marker of early left ventricular dysfunction than left-ventricular ejection fraction (LVEF). fSENC (fast strain encoded imaging) and FT (feature tracking) both allow for reproducible assessment of myocardial strain. However, left-ventricular long axis strain (LVLAS) might enable an equally sensitive measurement of myocardial deformation as global longitudinal or circumferential strain in a more rapid and simple fashion.

METHODS

In this study we compared the diagnostic performance of fSENC, FT and LVLAS for identification of cardiac pathology (ACS, cardiac-non-ACS) in patients presenting with chest pain (initial hscTnT 5-52 ng/l). Patients were prospectively recruited from the chest pain unit in Heidelberg. The CMR scan was performed within 1 h after patient presentation. Analysis of LVLAS was compared to the GLS and GCS as measured by fSENC and FT.

RESULTS

In total 40 patients were recruited (ACS n = 6, cardiac-non-ACS n = 6, non-cardiac n = 28). LVLAS was comparable to fSENC for differentiation between healthy myocardium and myocardial dysfunction (GLS-fSENC AUC: 0.882; GCS-fSENC AUC: 0.899; LVLAS AUC: 0.771; GLS-FT AUC: 0.740; GCS-FT: 0.688), while FT-derived strain did not allow for differentiation between ACS and non-cardiac patients. There was significant variability between the three techniques. Intra- and inter-observer variability (OV) was excellent for fSENC and FT, while for LVLAS the agreement was lower and levels of variability higher (intra-OV: Pearson > 0.7, ICC > 0.8; inter-OV: Pearson > 0.65, ICC > 0.8; CoV > 25%).

CONCLUSIONS

While reproducibility was excellent for both FT and fSENC, it was only fSENC and the LVLAS which allowed for significant identification of myocardial dysfunction, even before LVEF, and therefore might be used as rapid supporting parameters for assessment of left-ventricular function.

Hypverventilation strain CMR imaging in patients with acute chest pain

In patients with suspected acute coronary syndrome high-sensitivity cardiac tropnonin T is used for rapid patient triage. Some acute coronary syndrome patients assigned to the observe zone based on high-sensitivity cardiac troponin T after 1 h require further diagnostic testing. Fast-strain encoded CMR imaging with breathing maneuvers may accelerate diagnostic work-up and identify patients suffering from acute coronary syndrome. Patients presenting with acute chest pain (high-sensitivity cardiac troponin T level 5-52 ng/L) were prospectively enrolled (consecutive sampling, time of recruitment: 09/18-06/19). Fast-strain-encoded imaging was performed within the 1-h timeframe (0 h/1 h algorithm) prior to 2nd high-sensitivity troponin T lab results. Images were acquired at rest as well as after 1-min of hyperventilation followed by a short breath-hold. In 108 patients (59 male; mean age: 57 ± 17y) the mean study time was 17 ± 3 min. An abnormal strain response after the breathing maneuver (persistent/increased/new onset of increased strain rates) correctly identified all 17 patients with a high-sensitivity troponin T dynamic (0 h/1 h algorithm) and explanatory significant coronary lesions, while in 86 patients without serologic or angiographic evidence for severe coronary artery disease the strain response was normal (sensitivity 100%, specificity 94.5%; 5 false positive results). The number of dysfunctional segments (strain > - 10%) proved to be a quantifiable marker for identifying patients with acute coronary syndrome. In patients with suspected acute coronary syndrome and inconclusive initial high-sensitivity troponin T, fast-strain-encoded imaging with a breathing maneuver may safely and rapidly identify patients with acute coronary syndrome, without the need for vasodilators, stress, or contrast agents.

The role of cardiac magnetic resonance imaging in the assessment of heart failure with preserved ejection fraction

Heart failure (HF) is a major cause of morbidity and mortality worldwide. Current classifications of HF categorize patients with a left ventricular ejection fraction of 50% or greater as HF with preserved ejection fraction or HFpEF. Echocardiography is the first line imaging modality in assessing diastolic function given its practicality, low cost and the utilization of Doppler imaging. However, the last decade has seen cardiac magnetic resonance (CMR) emerge as a valuable test for the sometimes challenging diagnosis of HFpEF. The unique ability of CMR for myocardial tissue characterization coupled with high resolution imaging provides additional information to echocardiography that may help in phenotyping HFpEF and provide prognostication for patients with HF. The precision and accuracy of CMR underlies its use in clinical trials for the assessment of novel and repurposed drugs in HFpEF. Importantly, CMR has powerful diagnostic utility in differentiating acquired and inherited heart muscle diseases presenting as HFpEF such as Fabry disease and amyloidosis with specific treatment options to reverse or halt disease progression. This state of the art review will outline established CMR techniques such as transmitral velocities and strain imaging of the left ventricle and left atrium in assessing diastolic function and their clinical application to HFpEF. Furthermore, it will include a discussion on novel methods and future developments such as stress CMR and MR spectroscopy to assess myocardial energetics, which show promise in unraveling the mechanisms behind HFpEF that may provide targets for much needed therapeutic interventions.

Comparative Analysis of Myocardial Viability Multimodality Imaging in Patients with Previous Myocardial Infarction and Symptomatic Heart Failure

Background and Objectives: To compare the accuracy of multimodality imaging (myocardial perfusion imaging with single-photon emission computed tomography (SPECT MPI), 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET), and cardiovascular magnetic resonance (CMR) in the evaluation of left ventricle (LV) myocardial viability for the patients with the myocardial infarction (MI) and symptomatic heart failure (HF). Materials and Methods: 31 consecutive patients were included in the study prospectively, with a history of previous myocardial infarction, symptomatic HF (NYHA) functional class II or above, reduced ejection fraction (EF) ≤ 40%. All patients had confirmed atherosclerotic coronary artery disease (CAD), but conflicting opinions regarding the need for percutaneous intervention due to the suspected myocardial scar tissue. All patients underwent transthoracic echocardiography (TTE), SPECT MPI, 18F-FDG PET, and CMR with late gadolinium enhancement (LGE) examinations. Quantification of myocardial viability was assessed in a 17-segment model. All segments that were described as non-viable (score 4) by CMR LGE and PET were compared. The difference of score between CMR and PET we named reversibility score. According to this reversibility score, patients were divided into two groups: Group 1, reversibility score > 10 (viable myocardium with a chance of functional recovery after revascularization); Group 2, reversibility score ≤ 10 (less viable myocardium when revascularisation remains questionable). Results: 527 segments were compared in total. A significant difference in scores 1, 2, 3 group, and score 4 group was revealed between different modalities. CMR identified “non-viable” myocardium in 28.1% of segments across all groups, significantly different than SPECT in 11.8% PET in 6.5% Group 1 (viable myocardium group) patients had significantly higher physical tolerance (6 MWT (m) 3892 ± 94.5 vs. 301.4 ± 48.2), less dilated LV (LVEDD (mm) (TTE) 53.2 ± 7.9 vs. 63.4 ± 8.9; MM (g) (TTE) 239.5 ± 85.9 vs. 276.3 ± 62.7; LVEDD (mm) (CMR) 61.7 ± 8.1 vs. 69.0 ± 6.1; LVEDDi (mm/m2) (CMR) 29.8 ± 3.7 vs. 35.2 ± 3.1), significantly better parameters of the right heart (RV diameter (mm) (TTE) 33.4 ± 6.9 vs. 38.5 ± 5.0; TAPSE (mm) (TTE) 18.7 ± 2.0 vs. 15.2 ± 2.0), better LV SENC function (LV GLS (CMR) −14.3 ± 2.1 vs. 11.4 ± 2.9; LV GCS (CMR) −17.2 ± 4.6 vs. 12.7 ± 2.6), smaller size of involved myocardium (infarct size (%) (CMR) 24.5 ± 9.6 vs. 34.8 ± 11.1). Good correlations were found with several variables (LVEDD (CMR), LV EF (CMR), LV GCS (CMR)) with a coefficient of determination (R2) of 0.72. According to the cut-off values (LVEDV (CMR) > 330 mL, infarct size (CMR) > 26%, and LV GCS (CMR) < −15.8), we performed prediction of non-viable myocardium (reversibility score < 10) with the overall percentage of 80.6 (Nagelkerke R2 0.57). Conclusions: LGE CMR reveals a significantly higher number of scars, and the FDG PET appears to be more optimistic in the functional recovery prediction. Moreover, using exact imaging parameters (LVEDV (CMR) > 330 mL, infarct size (CMR) > 26% and LV GCS (CMR) < −15.8) may increase sensitivity and specificity of LGE CMR for evaluation of non-viable myocardium and lead to a better clinical solution (revascularization vs. medical treatment) even when viability is low in LGE CMR, and FDG PET is not performed.

Left-Ventricular Reference Myocardial Strain Assessed by Cardiovascular Magnetic Resonance Feature Tracking and fSENC-Impact of Temporal Resolution and Cardiac Muscle Mass

Aims: Cardiac strain parameters are increasingly measured to overcome shortcomings of ejection fraction. For broad clinical use, this study provides reference values for the two strain assessment methods feature tracking (FT) and fast strain-encoded (fSENC) cardiovascular magnetic resonance (CMR) imaging, including the child/adolescent group and systematically evaluates the influence of temporal resolution and muscle mass on strain.

Methods and Results: Global longitudinal (GLS), circumferential (GCS), and radial (GRS) strain values in 181 participants (54% women, 11–70 years) without cardiac illness were assessed with FT (CVI42® software). GLS and GCS were also analyzed using fSENC (MyoStrain® software) in a subgroup of 84 participants (60% women). Fourteen patients suffering hypertrophic cardiomyopathy (HCM) were examined with both techniques. CMR examinations were done on a 3.0T MR-system.

FT-GLS, FT-GCS, and FT-GRS were −16.9 ± 1.8%, −19.2 ± 2.1% and 34.2 ± 6.1%. fSENC-GLS was higher at −20.3 ± 1.8% (p < 0.001). fSENC-GCS was comparable at−19.7 ± 1.8% (p = 0.06). All values were lower in men (p < 0.001). Cardiac muscle mass correlated (p < 0.001) with FT-GLS (r = 0.433), FT-GCS (r = 0.483) as well as FT-GRS (r = −0.464) and acts as partial mediator for sex differences. FT-GCS, FT-GRS and fSENC-GLS correlated weakly with age. FT strain values were significantly lower at lower cine temporal resolutions, represented by heart rates (r = −0.301, −0.379, 0.385) and 28 or 45 cardiac phases per cardiac cycle (0.3–1.9% differences). All values were lower in HCM patients than in matched controls (p < 0.01). Cut-off values were −15.0% (FT-GLS), −19.3% (FT-GCS), 32.7% (FT-GRS), −17.2% (fSENC-GLS), and −17.7% (fSENC-GCS).

Conclusion: The analysis of reference values highlights the influence of gender, temporal resolution, cardiac muscle mass and age on myocardial strain values.

An off-resonance insensitive orthogonal CSPAMM sequence (ORI-O-CSPAMM) for the acquisition of CSPAMM and MICSR grids in half scan time

PURPOSE

To develop an Off-Resonance Insensitive Orthogonal CSPAMM sequence (ORI-O-CSPAMM) for the acquisition of CSPAMM and MICSR grids in half of the acquisition time.

METHODS

Phantom and mid-level left ventricle short-axis tagged images were acquired using CSPAMM, ORI-CSPAMM, O-CSPAMM, and the proposed ORI-O-CPAMM sequences to interrogate and compare its behavior under off-resonance effects produced by vegetable oil and subcutaneous and epicardial fat. The images were compared in terms of signal and the capacity to obtain complex difference and MICSR images.

RESULTS

Like ORI-CSPAMM, the proposed ORI-O-CSPAMM sequence removed almost completely the off-resonance artifacts produced during the tagging preparation. Tagging grids without DC components were obtained with ORI-O-CSPAMM using complex difference and MICSR from only two complementary images, which reduced the scan time to a half compared to CSPAMM and ORI-CSPAMM. The removal of off-resonance effects and the capacity to obtain MICSR images are advantages of ORI-O-CSPAMM over the O-CSPAMM sequence.

CONCLUSION

We developed a novel and fast tagging sequence designed to remove off-resonance effects during the tagging preparation, and to obtain complex difference and MICSR grids in half of the scan time compared to CSPAMM and ORI-CSPAMM sequences, which could allow its application to clinical protocols.

Multi-parametric assessment of left ventricular hypertrophy using late gadolinium enhancement, T1 mapping and strain-encoded cardiovascular magnetic resonance

AIM

To evaluate the ability of single heartbeat fast-strain encoded (SENC) cardiovascular magnetic resonance (CMR) derived myocardial strain to discriminate between different forms of left ventricular (LV) hypertrophy (LVH).

METHODS

314 patients (228 with hypertensive heart disease (HHD), 45 with hypertrophic cardiomyopathy (HCM), 41 with amyloidosis, 22 competitive athletes, and 33 healthy controls) were systematically analysed. LV ejection fraction (LVEF), LV mass index and interventricular septal (IVS) thickness, T1 mapping and atypical late gadolinium enhancement (LGE) were assessed. In addition, the percentage of LV myocardial segments with strain ≤ - 17% (%normal myocardium) was determined.

RESULTS

Patients with amyloidosis and HCM exhibited the highest IVS thickness (17.4 ± 3.3 mm and 17.4 ± 6 mm, respectively, p < 0.05 vs. all other groups), whereas patients with amyloidosis showed the highest LV mass index (95.1 ± 20.1 g/m2, p < 0.05 vs all others) and lower LVEF compared to controls (50.5 ± 9.8% vs 59.2 ± 5.5%, p < 0.05). Analysing subjects with mild to moderate hypertrophy (IVS 11-15 mm), %normal myocardium exhibited excellent and high precision, respectively for the differentiation between athletes vs. HCM (sensitivity and specificity = 100%, Area under the curve; AUC%normalmyocardium = 1.0, 95%CI = 0.85-1.0) and athletes vs. HHD (sensitivity = 83%, specificity = 75%, AUC%normalmyocardium = 0.85, 95%CI = 0.78-0.90). Combining %normal myocardial strain with atypical LGE provided high accuracy also for the differentiation of HHD vs. HCM (sensitivity = 82%, specificity = 100%, AUCcombination = 0.92, 95%CI = 0.88-0.95) and HCM vs. amyloidosis (sensitivity = 83%, specificity = 100%, AUCcombination = 0.83, 95%CI = 0.60-0.96).

CONCLUSION

Fast-SENC derived myocardial strain is a valuable tool for differentiating between athletes vs. HCM and athletes vs. HHD. Combining strain and LGE data is useful for differentiating between HHD vs. HCM and HCM vs. cardiac amyloidosis.

Value CMR: Towards a Comprehensive, Rapid, Cost-Effective Cardiovascular Magnetic Resonance Imaging

Cardiac magnetic resonance imaging (CMR) is considered the gold standard for measuring cardiac function. Further, in a single CMR exam, information about cardiac structure, tissue composition, and blood flow could be obtained. Nevertheless, CMR is underutilized due to long scanning times, the need for multiple breath-holds, use of a contrast agent, and relatively high cost. In this work, we propose a rapid, comprehensive, contrast-free CMR exam that does not require repeated breath-holds, based on recent developments in imaging sequences. Time-consuming conventional sequences have been replaced by advanced sequences in the proposed CMR exam. Specifically, conventional 2D cine and phase-contrast (PC) sequences have been replaced by optimized 3D-cine and 4D-flow sequences, respectively. Furthermore, conventional myocardial tagging has been replaced by fast strain-encoding (SENC) imaging. Finally, T1 and T2 mapping sequences are included in the proposed exam, which allows for myocardial tissue characterization. The proposed rapid exam has been tested in vivo. The proposed exam reduced the scan time from >1 hour with conventional sequences to <20 minutes. Corresponding cardiovascular measurements from the proposed rapid CMR exam showed good agreement with those from conventional sequences and showed that they can differentiate between healthy volunteers and patients. Compared to 2D cine imaging that requires 12-16 separate breath-holds, the implemented 3D-cine sequence allows for whole heart coverage in 1-2 breath-holds. The 4D-flow sequence allows for whole-chest coverage in less than 10 minutes. Finally, SENC imaging reduces scan time to only one slice per heartbeat. In conclusion, the proposed rapid, contrast-free, and comprehensive cardiovascular exam does not require repeated breath-holds or to be supervised by a cardiac imager. These improvements make it tolerable by patients and would help improve cost effectiveness of CMR and increase its adoption in clinical practice.

Role of cardiovascular magnetic resonance in early detection and treatment of cardiac dysfunction in oncology patients

The purpose of this review is to provide an overview of the essential role that cardiovascular magnetic resonance (CMR) has in the field of cardio-oncology. Recent findings: CMR has been increasingly used for early identification of cancer therapy related cardiac dysfunction (CTRCD) due to its precision in detecting subtle changes in cardiac function and for myocardial tissue characterization. Summary: CMR is able to identify subclinical CTRCD in patients receiving potentially cardiotoxic chemotherapy and guide initiation of cardio protective therapy. Multiparametric analysis with myocardial strain, tissue characterization play a critical role in understanding important clinical questions in cardio-oncology.

Reference ranges ("normal values") for cardiovascular magnetic resonance (CMR) in adults and children: 2020 update

Cardiovascular magnetic resonance (CMR) enables assessment and quantification of morphological and functional parameters of the heart, including chamber size and function, diameters of the aorta and pulmonary arteries, flow and myocardial relaxation times. Knowledge of reference ranges ("normal values") for quantitative CMR is crucial to interpretation of results and to distinguish normal from disease. Compared to the previous version of this review published in 2015, we present updated and expanded reference values for morphological and functional CMR parameters of the cardiovascular system based on the peer-reviewed literature and current CMR techniques. Further, databases and references for deep learning methods are included.

Quantification of myocardial strain assessed by cardiovascular magnetic resonance feature tracking in healthy subjects-influence of segmentation and analysis software

Objectives

Quantification of myocardial deformation by feature tracking is of growing interest in cardiovascular magnetic resonance. It allows the assessment of regional myocardial function based on cine images. However, image acquisition, post-processing, and interpretation are not standardized. We aimed to assess the influence of segmentation procedure such as slice selection and different types of analysis software on values and quantification of myocardial strain in healthy adults.

Methods

Healthy volunteers were retrospectively analyzed. Post-processing was performed using CVI⁴² and TomTec. Longitudinal and radial_{Long axis (LAX)} strain were quantified using 4-chamber-view, 3-chamber-view, and 2-chamber-view. Circumferential and radial_{Short axis (SAX)} strain were assessed in basal, midventricular, and apical short-axis views and using full coverage. Global and segmental strain values were compared to each other regarding their post-processing approach and analysis software package.

Results

We screened healthy volunteers studied at 1.5 or 3.0 T and included 67 (age 44.3 ± 16.3 years, 31 females). Circumferential and radial_SAX strain values were different between a full coverage approach vs. three short slices (− 17.6 ± 1.8% vs. − 19.2 ± 2.3% and 29.1 ± 4.8% vs. 34.6 ± 7.1%). Different analysis software calculated significantly different strain values. Within the same vendor, different field strengths (− 17.0 ± 2.1% at 1.5 T vs. − 17.0 ± 1.7% at 3 T, p = 0.845) did not influence the calculated global longitudinal strain (GLS), and were similar in gender (− 17.4 ± 2.0% in females vs. − 16.6 ± 1.8% in males, p = 0.098). Circumferential and radial strain were different in females and males (circumferential strain − 18.2 ± 1.7% vs. − 17.1 ± 1.8%, p = 0.029 and radial strain 30.7 ± 4.7% vs. 27.8 ± 4.6%, p = 0.047).

Conclusions

Myocardial deformation assessed by feature tracking depends on segmentation procedure and type of analysis software. Circumferential_SAX and radial_SAX depend on the number of slices used for feature tracking analysis. As known from other imaging modalities, GLS seems to be the most stable parameter. During follow-up studies, standardized conditions should be warranted.

Trial registration Retrospectively registered

Key Points

• Myocardial deformation assessed by feature tracking depends on the segmentation procedure.

• Global myocardial strain values differ significantly among vendors.

• Standardization in post-processing using CMR feature tracking is essential.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00330-020-07539-5.

Quantification of myocardial strain in patients with isolated left ventricular non-compaction and healthy subjects using deformable registration algorithm: comparison with feature tracking

Background

Systolic dysfunction of the left ventricle is frequently associated with isolated left ventricular non-compaction (iLVNC). Clinically, the ejection fraction (EF) is the primary index of cardiac function. However, changes of EF usually occur later in the disease course. Feature tracking (FT) and deformable registration algorithm (DRA) have become appealing techniques for myocardial strain assessment.

Methods

Thirty patients with iLVNC (36.7 ± 13.3 years old) and fifty healthy volunteers (42.3 ± 13.6 years old) underwent cardiovascular magnetic resonance (CMR) examination on a 1.5 T MR scanner. Strain values in the radial, circumferential, longitudinal directions were analyzed based on the short-axis and long-axis cine images using FT and DRA methods. The iLVNC patients were further divided based on the ejection fraction, into EF ≥ 50% group (n = 11) and EF < 50% group (n = 19). Receiver-operating-characteristic (ROC) analysis was performed to assess the diagnostic performance of the global strain values. Intraclass correlation coefficient (ICC) analysis was used to evaluate the intra- and inter-observer agreement.

Results

Global radial strain (GRS) was statistically lower in EF ≥ 50% group compared with control group [GRS (DRA)/% vs. controls: 34.6 ± 7.0 vs. 37.6 ± 7.2, P < 0.001; GRS (FT)/% vs. controls: 37.4 ± 13.2 vs. 56.9 ± 16.4, P < 0.01]. ROC analysis of global strain values derived from DRA and FT demonstrated high area under curve (range, 0.743–0.854). DRA showed excellent intra- and inter-observer agreement of global strain in both iLVNC patients (ICC: 0.995–0.999) and normal controls (ICC: 0.934–0.996). While for FT analysis, global radial strain of normal controls showed moderate intra-observer (ICC: 0.509) and poor inter-observer agreement (ICC: 0.394).

Conclusions

In patients with iLVNC, DRA can be used to quantitatively analyze the strain of left ventricle, with global radial strain being an earlier marker of LV systolic dysfunction. DRA has better reproducibility in evaluating both the global and segmental strain.

Non-contrast enhanced diagnosis of acute myocarditis based on the 17-segment heart model using 2D-feature tracking magnetic resonance imaging

PURPOSE

The aim of this study was to investigate the diagnostic value of myocardial deformation analysis based on the 17-segment heart model using non-contrast enhanced (CE) 2D tissue feature tracking (2D-FT) technique.

MATERIAL AND METHODS

Seventy patients with suspected myocarditis underwent a cardiovascular magnetic resonance (CMR) examination at 1.5 Tesla. A contrast-agent-free part of this CMR protocol was additionally performed in forty healthy volunteers (HV). Besides standard CMR data sets, 2D-FT derived segmental and global longitudinal, radial, and circumferential deformation parameters were analyzed. The 2D-FT results were compared to the combined findings from CMR imaging and endomyocardial biopsy (EMB).

RESULTS

Patients were assigned to three groups depending on their ejection fraction (EF) (<40%, 40-55%, ≥55%). Compared to HV, impaired EF (<55%) was significantly correlated to reduced segmental and global strain and strain rate values. The circumferential deformation analysis was more sensitive to myocardial changes than longitudinal and radial analysis. The segmental strain/strain rate had an accuracy of 84.3%/70.0% for the diagnosis of an acute myocarditis, stated by EMB and CMR in 42 of 70 patients. In patients with preserved EF, acute myocarditis could be ruled out using only segmental strain analysis with a negative predictive value of 87.5%.

CONCLUSION

In patients with suspected myocarditis, the deformation analysis based on the 17-segment heart model provides valuable information about functional myocardial inhomogeneity. This quantitative approach could be used in addition to the clinical standard CMR protocol and represents a promising tool in the framework of a prospective automatized multiparametric CMR imaging analysis.

Effect of comprehensive initial training on the variability of left ventricular measures using fast-SENC cardiac magnetic resonance imaging

Cardiac magnetic resonance (CMR) is becoming the imaging modality of choice in multicenter studies where highly reproducible measurements are necessary. The purpose of this study was to assess the effect of comprehensive initial training on reproducibility of quantitative left ventricular (LV) parameters estimated using strain-encoded (SENC) imaging. Thirty participants (10 patients with heart failure (HF) and preserved LV ejection fraction (HFpEF), 10 patients with HF and reduced LV ejection fraction (HFrEF) and 10 healthy volunteers) were examined using fast-SENC imaging. Four observers with different experience in non-invasive cardiac imaging completed comprehensive initial training course and were invited to perform CMR data analysis. To assess agreement between observers, LV volumes, mass, ejection fraction (LVEF), global longitudinal strain (GLS) and global circumferential strain (GCS) were estimated using dedicated software (MyoStrain, USA). To test intraobserver agreement data analysis was repeated after 4 weeks. SENC imaging and analysis were fast and were completed in less than 5 minutes. LV end-diastolic volume index (LVEDVi), LVEF and strain were significantly lower in HFpEF patients than in healthy volunteers (p = 0.019 for LVEDVi; p = 0.023 for LVEF; p = 0.004 for GLS and p < 0.001 for GCS). All LV functional parameters were further reduced in HFrEF. Excellent interobserver agreement was found for all LV parameters independently of the level of experience. The reproducibility of LV mass was lower, especially at the intraobserver level (ICC 0.91; 95% CI 0.74–0.96). LV volumetric and functional parameters derived using fast-SENC imaging, are highly reproducible. The appropriate initial training is relevant and allows to achieve highest concordance in fast-SENC measurements.

Association of cardiovascular magnetic resonance-derived circumferential strain parameters with the risk of ventricular arrhythmia and all-cause mortality in patients with prior myocardial infarction and primary prevention implantable cardioverter defibrillator

BACKGROUND

Impaired left ventricular (LV) contraction and relaxation may further promote adverse remodeling and may increase the risk of ventricular arrhythmia (VA) in ischemic cardiomyopathy. We aimed to examine the association of cardiovascular magnetic resonance (CMR)-derived circumferential strain parameters for LV regional systolic function, LV diastolic function and mechanical dispersion with the risk of VA in patients with prior myocardial infarction and primary prevention implantable cardioverter defibrillator (ICD).

METHODS

Patients with an ischemic cardiomyopathy who underwent CMR prior to primary prevention ICD implantation, were retrospectively identified. LV segmental circumferential strain curves were extracted from short-axis cine CMR. For LV regional strain analysis, the extent of moderately and severely impaired strain (percentage of LV segments with strain between - 10% and - 5% and > - 5%, respectively) were calculated. LV diastolic function was quantified by the early and late diastolic strain rate. Mechanical dispersion was defined as the standard deviation in delay time between each strain curve and the patient-specific reference curve. Cox proportional hazard ratios (HR) (95%CI) were calculated to assess the association between LV strain parameters and appropriate ICD therapy.

RESULTS

A total of 121 patients (63 ± 11 years, 84% men, LV ejection fraction (LVEF) 27 ± 9%) were included. During a median (interquartile range) follow-up of 47 (27;69) months, 30 (25%) patients received appropriate ICD therapy. The late diastolic strain rate (HR 1.1 (1.0;1.2) per - 0.25 1/s, P = 0.043) and the extent of moderately impaired strain (HR 1.5 (1.0;2.2) per + 10%, P = 0.048) but not the extent of severely impaired strain (HR 0.9 (0.6;1.4) per + 10%, P = 0.685) were associated with appropriate ICD therapy, independent of LVEF, late gadolinium enhancement (LGE) scar border size and acute revascularization. Mechanical dispersion was not related to appropriate ICD therapy (HR 1.1 (0.8;1.6) per + 25 ms, P = 0.464).

CONCLUSIONS

In an ischemic cardiomyopathy population referred for primary prevention ICD implantation, the extent of moderately impaired strain and late diastolic strain rate were associated with the risk of appropriate ICD therapy, independent of LVEF, scar border size and acute revascularization. These findings suggest that disturbed LV contraction and relaxation may contribute to an increased risk of VA after myocardial infarction.

Strain-encoded magnetic resonance: a method for the assessment of myocardial deformation

This study aims to assess the usefulness of strain‐encoded magnetic resonance (SENC) for the quantification of myocardial deformation (‘strain’) in healthy volunteers and for the diagnostic workup of patients with different cardiovascular pathologies. SENC was initially described in the year 2001. Since then, the SENC sequence has undergone several technical developments, aiming at the detection of strain during single‐heartbeat acquisitions (fast‐SENC). Experimental and clinical studies that used SENC and fast‐SENC or compared SENC with conventional cine or tagged magnetic resonance in phantoms, animals, healthy volunteers, or patients were systematically searched for in PubMed. Using ‘strain‐encoded magnetic resonance and SENC’ as keywords, three phantom and three animal studies were identified, along with 27 further clinical studies, involving 185 healthy subjects and 904 patients. SENC (i) enabled reproducible assessment of myocardial deformation in vitro, in animals and in healthy volunteers, (ii) showed high reproducibility and substantially lower time spent compared with conventional tagging, (iii) exhibited incremental value to standard cine imaging for the detection of inducible ischaemia and for the risk stratification of patients with ischaemic heart disease, and (iv) enabled the diagnostic classification of patients with transplant vasculopathy, cardiomyopathies, pulmonary hypertension, and diabetic heart disease. SENC has the potential to detect a wide range of myocardial diseases early, accurately, and without the need of contrast agent injection, possibly enabling the initiation of specific cardiac therapies during earlier disease stages. Its one‐heartbeat acquisition mode during free breathing results in shorter cardiovascular magnetic resonance protocols, making its implementation in the clinical realm promising.

Strain-encoded cardiac magnetic resonance imaging: a new approach for fast estimation of left ventricular function

Background

Recently introduced fast strain-encoded (SENC) cardiac magnetic resonance (CMR) imaging (fast-SENC) provides real-time acquisition of myocardial performance in a single heartbeat. We aimed to test the ability and accuracy of real-time strain-encoded CMR imaging to estimate left ventricular volumes, ejection fraction and mass.

Methods

Thirty-five subjects (12 healthy volunteers and 23 patients with known or suspected coronary artery disease) were investigated. All study participants were imaged at 1.5 Tesla MRI scanner (Achieva, Philips) using an advanced CMR study protocol which included conventional cine and fast-SENC imaging. A newly developed real-time free-breathing SENC imaging technique based on the acquisition of two images with different frequency modulation was employed.

Results

All parameters were successfully derived from fast-SENC images with total study time of 105 s (a 15 s scan time and a 90 s post-processing time). There was no significant difference between fast-SENC and cine imaging in the estimation of LV volumes and EF, whereas fast-SENC underestimated LV end-diastolic mass by 7%.

Conclusion

The single heartbeat fast-SENC technique can be used as a good alternative to cine imaging for the precise calculation of LV volumes and ejection fraction while the technique significantly underestimates LV end-diastolic mass.

Feature-tracking myocardial strain in healthy adults- a magnetic resonance study at 3.0 tesla

We analyzed feature-tracking derived circumferential and longitudinal strain in healthy volunteers who underwent cardiac magnetic resonance imaging (CMR) at 3.0 T. 88 healthy adults (44.6 ± 18.0 years old, 49% male), without prior cardiovascular disease, underwent CMR at 3.0 T including cine, and late gadolinium enhancement in subjects >45 years. LV functional analysis and feature-tracking strain analyses were carried out. Global strain had better reproducibility than segmental strain. There was a sex specific difference global longitudinal strain (mean ± SD, -18.48 ± 3.65% (male), -21.91 ± 3.01% (female), p < 0.001), but not global circumferential strain (mean ± SD, -25.41 ± 4.50% (male), -27.94 ± 3.48% (female), p = 0.643). There was no association of strain with ageing after accounting for sex for both global longitudinal and circumferential strain. Feature-tracking strain analysis is feasible at 3.0 T. Healthy female volunteers demonstrated higher magnitudes of global longitudinal strain when compared to male counterparts. Whilst global cine-strain has good reproducibility, segmental strain does not.

MRI-derived Regional Biventricular Function in Patients with Chronic Thromboembolic Pulmonary Hypertension Before and After Pulmonary Endarterectomy

RATIONALE AND OBJECTIVES

The aim of this study was to assess regional myocardial function in patients with chronic thromboembolic hypertension (CTEPH) before and after successful pulmonary endarterectomy (PEA) using magnetic resonance imaging.

METHODS

Twenty-two patients with CTEPH underwent cardiac magnetic resonance imaging before and 12 (11, 17) days after PEA. Mean pulmonary artery pressure was evaluated preoperatively by right heart catheterization and during post-PEA intensive care unit-stay using a Swan-Ganz catheter. Biventricular peak systolic longitudinal, radial, circumferential strain and time-to-peak strain were obtained by tissue-tracking analysis.

RESULTS

Mean pulmonary artery pressure decreased (46 mm Hg (34.5, 55) to 24 mm Hg (16, 27); P < .0001) and stroke volume increased (P < .0001) after PEA. In the right ventricle (RV) peak radial strain increased in the anterior (P = .04) and in the inferior wall (P = .0012) and slightly missed statistical significance in the lateral wall (P = .051) and septum (P = .07). Circumferential strain increased in the lateral (P = .0002) and inferior wall of the RV (P = .03) and in the lateral as well as in the inferior wall of the left ventricle (P = .01; P = .03). Radial, longitudinal, and circumferential time-to-peak strain shortened (P < .0001) with resynchronization of the ventricles 12 days after PEA.

CONCLUSION

While biventricular resynchronization and recovery of global predominantly RV function was observed, regional circumferential function mainly improved in the lateral and inferior walls of both ventricles and regional radial function in the RV wall and septum 12 days after PEA, suggesting fibers primarily affected by myocardial stress in patients with CTEPH possibly need a relatively longer recovery time.

Reproducibility study on myocardial strain assessment using fast-SENC cardiac magnetic resonance imaging

Myocardial strain is a well validated parameter for estimating left ventricular (LV) performance. The aim of our study was to evaluate the inter-study as well as intra- and interobserver reproducibility of fast-SENC derived myocardial strain. Eighteen subjects (11 healthy individuals and 7 patients with heart failure) underwent a cardiac MRI examination including fast-SENC acquisition for evaluating left ventricular global longitudinal (GLS) and circumferential strain (GCS) as well as left ventricular ejection fraction (LVEF). The examination was repeated after 63 [range 49‒87] days and analyzed by two experienced observers. Ten datasets were repeatedly assessed after 1 month by the same observer to test intraobserver variability. The reproducibility was measured using the intraclass correlation coefficient (ICC) and Bland-Altman analysis. Patients with heart failure demonstrated reduced GLS and GCS compared to healthy controls (−15.7 ± 3.7 vs. −20.1 ± 1.4; p = 0.002 for GLS and −15.3 ± 3.7 vs. −21.4 ± 1.1; p = 0.001 for GCS). The test-retest analysis showed excellent ICC for LVEF (0.92), GLS (0.94) and GCS (0.95). GLS exhibited excellent ICC (0.99) in both intra- and interobserver variability analysis with very narrow limits of agreement (−0.6 to 0.5 for intraobserver and −1.3 to 0.96 for interobserver agreement). Similarly, GCS showed excellent ICC (0.99) in both variability analyses with narrow limits of agreement (−1.1 to 1.2 for intraobserver and −1.7 to 1.3 for interobserver agreement), whereas LVEF showed larger limits of agreement (−14.4 to 10.1). The analysis of fast-SENC derived myocardial strain using cardiac MRI provides a highly reproducible method for assessing LV functional performance.

Longitudinal Deformation of the Right Ventricle in Hypoplastic Left Heart Syndrome: A Comparative Study of 2D-Feature Tracking Magnetic Resonance Imaging and 2D-Speckle Tracking Echocardiography

In hypoplastic left heart syndrome (HLHS), long-term outcome is closely related to right ventricular function. Echocardiography and magnetic resonance imaging (MRI) are routinely used for functional assessment. MRI 2D-tissue feature tracking (2D-FT) allows quantification of myocardial deformation but has not yet been applied to HLHS patients. We sought to investigate the feasibility of this technique and to compare the results to 2D-speckle tracking echocardiography (2D-STE). In routine MRI 2D anatomical four chamber view, cine images were recorded in 55 HLHS patients (median age 4.9 years [1.6, 17.0]). Regional and global peak systolic longitudinal strain (LS) and strain rate (LSR) were determined using 2D-FT software. Echocardiographic four chamber view was analyzed with 2D-STE. Visualization of all myocardial segments with MRI was excellent, regional, and global LS and LSR could be assessed in all data sets. In 2D-STE, 28% of apical segments could not be analyzed due to poor image quality. Agreement of 2D-FT MRI and 2D-STE was acceptable for global LS, but poor for global LSR. In MRI, regional LS was lower in the septal segments, while LSR was not different between the segments. GLS and GLSR correlated with ejection fraction (GLS: r = - 0.45 and r < 0.001, GLSR: r = - 0.34 and p = 0.01). With new post-processing options, the assessment of regional and global LS and LSR is feasible in routine MRI of HLHS patients. For LS, results were comparable with 2D-STE. The agreement was poor for LSR, which might relate to differences in temporal resolution between the two imaging modalities.

Strain imaging using cardiac magnetic resonance

The objective assessments of left ventricular (LV) and right ventricular (RV) ejection fractions (EFs) are the main important tasks of routine cardiovascular magnetic resonance (CMR). Over the years, CMR has emerged as the reference standard for the evaluation of biventricular morphology and function. However, changes in EF may occur in the late stages of the majority of cardiac diseases, and being a measure of global function, it has limited sensitivity for identifying regional myocardial impairment. On the other hand, current wall motion evaluation is done on a subjective basis and subjective, qualitative analysis has a substantial error rate. In an attempt to better quantify global and regional LV function; several techniques, to assess myocardial deformation, have been developed, over the past years. The aim of this review is to provide a comprehensive compendium of all the CMR techniques to assess myocardial deformation parameters as well as the application in different clinical scenarios.

Heterogeneity of longitudinal and circumferential contraction in relation to late gadolinium enhancement in hypertrophic cardiomyopathy patients with preserved left ventricular ejection fraction

PURPOSE

To evaluate heterogeneity of myocardial contraction in relation to extensive late gadolinium enhancement (LGE) in hypertrophic cardiomyopathy (HCM) patients with preserved left ventricular ejection fraction, using fast strain-encoded magnetic resonance imaging.

MATERIALS AND METHODS

Twenty-two HCM patients and 24 age-matched control subjects were included in this retrospective study. The regional and global peak values of longitudinal and circumferential strain (LS_regional, LS_global, CS_regional, CS_global), and their regional heterogeneities were evaluated using coefficients of variation (LS_CoV, CS_CoV) in relation to LGE. Receiver operating characteristic curve analysis was performed to identify patients with a total left ventricular myocardial LGE ≥ 15%.

RESULTS

LS_global in HCM patients was significantly decreased compared to that in controls (- 14.4 ± 2.4% vs - 17.2 ± 2.0%; p = 0.0004), while CS_global was not (p = 1.0). Negative LGE segments demonstrated decreased LS_regional in HCM patients compared to in controls (p < 0.0001), while CS_regional was not decreased. CS_CoV demonstrated the largest area under the curve (AUC) (0.91), with high sensitivity (83%) and specificity (94%) for detection of HCM patients with extensive LGE, while the AUC of LS_CoV was low (0.49).

CONCLUSION

The heterogeneity in CS_regional has a high diagnostic value for detection of HCM patients with extensive LGE.

Magnetic Resonance Imaging of Myocardial Strain After Acute ST-Segment-Elevation Myocardial Infarction: A Systematic Review

The purpose of this systematic review is to provide a clinically relevant, disease-based perspective on myocardial strain imaging in patients with acute myocardial infarction or stable ischemic heart disease. Cardiac magnetic resonance imaging uniquely integrates myocardial function with pathology. Therefore, this review focuses on strain imaging with cardiac magnetic resonance. We have specifically considered the relationships between left ventricular (LV) strain, infarct pathologies, and their associations with prognosis. A comprehensive literature review was conducted in accordance with the PRISMA guidelines. Publications were identified that (1) described the relationship between strain and infarct pathologies, (2) assessed the relationship between strain and subsequent LV outcomes, and (3) assessed the relationship between strain and health outcomes. In patients with acute myocardial infarction, circumferential strain predicts the recovery of LV systolic function in the longer term. The prognostic value of longitudinal strain is less certain. Strain differentiates between infarcted versus noninfarcted myocardium, even in patients with stable ischemic heart disease with preserved LV ejection fraction. Strain recovery is impaired in infarcted segments with intramyocardial hemorrhage or microvascular obstruction. There are practical limitations to measuring strain with cardiac magnetic resonance in the acute setting, and knowledge gaps, including the lack of data showing incremental value in clinical practice. Critically, studies of cardiac magnetic resonance strain imaging in patients with ischemic heart disease have been limited by sample size and design. Strain imaging has potential as a tool to assess for early or subclinical changes in LV function, and strain is now being included as a surrogate measure of outcome in therapeutic trials.

A Novel Method for Estimating Myocardial Strain: Assessment of Deformation Tracking Against Reference Magnetic Resonance Methods in Healthy Volunteers

We developed a novel method for tracking myocardial deformation using cardiac magnetic resonance (CMR) cine imaging. We hypothesised that circumferential strain using deformation-tracking has comparable diagnostic performance to a validated method (Displacement Encoding with Stimulated Echoes- DENSE) and potentially diagnostically superior to an established cine-strain method (feature-tracking). 81 healthy adults (44.6 ± 17.7 years old, 47% male), without any history of cardiovascular disease, underwent CMR at 1.5 T including cine, DENSE, and late gadolinium enhancement in subjects >45 years. Acquisitions were divided into 6 segments, and global and segmental peak circumferential strain were derived and analysed by age and sex. Peak circumferential strain differed between the 3 groups (DENSE: −19.4 ± 4.8%; deformation-tracking: −16.8 ± 2.4%; feature-tracking: −28.7 ± 4.8%) (ANOVA with Tukey post-hoc, F-value 279.93, p < 0.01). DENSE and deformation-tracking had better reproducibility than feature-tracking. Intra-class correlation co-efficient was >0.90. Larger magnitudes of strain were detected in women using deformation-tracking and DENSE, but not feature-tracking. Compared with a reference method (DENSE), deformation-tracking using cine imaging has similar diagnostic performance for circumferential strain assessment in healthy individuals. Deformation-tracking could potentially obviate the need for bespoke strain sequences, reducing scanning time and is more reproducible than feature-tracking.

Myocardial strain in healthy adults across a broad age range as revealed by cardiac magnetic resonance imaging at 1.5 and 3.0T: Associations of myocardial strain with myocardial region, age, and sex

Purpose

To assess myocardial strain using cine displacement encoding with stimulated echoes (DENSE) using 1.5T and 3.0T MRI in healthy adults.

Materials and Methods

Healthy adults without any history of cardiovascular disease underwent magnetic resonance imaging (MRI) at 1.5T and 3.0T within 2 days. The MRI protocol included balanced steady‐state free‐precession (b‐SSFP), 2D cine‐echo planar imaging (EPI)‐DENSE, and late gadolinium enhancement in subjects >45 years. Acquisitions were divided into six segments; global and segmental peak longitudinal and circumferential strain were derived and analyzed by field strength, age, and gender.

Results

In all, 89 volunteers (mean age 44.8 ± 18.0 years, range: 18–87 years) underwent MRI at 1.5T, and 88 of these subjects underwent MRI at 3.0T (1.4 ± 1.4 days between the scans). Compared with 3.0T, the magnitudes of global circumferential (–19.5 ± 2.6% vs. –18.47 ± 2.6%; P = 0.001) and longitudinal (–12.47 ± 3.2% vs. –10.53 ± 3.1%; P = 0.004) strain were greater at 1.5T. At 1.5T, longitudinal strain was greater in females than in males: –10.17 ± 3.4% vs. –13.67 ± 2.4%; P = 0.001. Similar observations occurred for circumferential strain at 1.5T (–18.72 ± 2.2% vs. –20.10 ± 2.7%; P = 0.014) and at 3.0T (–17.92 ± 1.8% vs. –19.1 ± 3.1%; P = 0.047). At 1.5T, longitudinal and circumferential strain were not associated with age after accounting for sex (longitudinal strain P = 0.178, circumferential strain P = 0.733). At 3.0T, longitudinal and circumferential strain were associated with age (P < 0.05). Longitudinal strain values were greater in the apico‐septal, basal‐lateral, and mid‐lateral segments and circumferential strain in the inferior, infero‐lateral, and antero‐lateral LV segments.

Conclusion

Myocardial strain parameters as revealed by cine‐DENSE at different MRI field strengths were associated with myocardial region, age, and sex. J. Magn. Reson. Imaging 2016;44:1197–1205.

A review of heart chamber segmentation for structural and functional analysis using cardiac magnetic resonance imaging

Cardiovascular magnetic resonance (CMR) has become a key imaging modality in clinical cardiology practice due to its unique capabilities for non-invasive imaging of the cardiac chambers and great vessels. A wide range of CMR sequences have been developed to assess various aspects of cardiac structure and function, and significant advances have also been made in terms of imaging quality and acquisition times. A lot of research has been dedicated to the development of global and regional quantitative CMR indices that help the distinction between health and pathology. The goal of this review paper is to discuss the structural and functional CMR indices that have been proposed thus far for clinical assessment of the cardiac chambers. We include indices definitions, the requirements for the calculations, exemplar applications in cardiovascular diseases, and the corresponding normal ranges. Furthermore, we review the most recent state-of-the art techniques for the automatic segmentation of the cardiac boundaries, which are necessary for the calculation of the CMR indices. Finally, we provide a detailed discussion of the existing literature and of the future challenges that need to be addressed to enable a more robust and comprehensive assessment of the cardiac chambers in clinical practice.

Global and regional functional assessment of ischemic heart disease with cardiac MR imaging

Cardiac MR imaging (CMR) combines assessment of myocardial function and tissue characterization, and is therefore ideally suited to evaluating patients with ischemic heart disease (IHD). This article discusses evaluation of left ventricular global function at CMR, reviewing the literature supporting global parameters in risk stratification and assessment of treatment response in IHD. Techniques for assessment of regional myocardial function are reviewed, and normal myocardial motion and fiber arrangement discussed. Despite barriers to clinical adoption, integration of this assessment into clinical routine should improve the ability to detect functional consequences of early myocardial structural alterations in patients with IHD.

Myocardial T2 mapping reveals age- and sex-related differences in volunteers

BACKGROUND

T2 mapping indicates to be a sensitive method for detection of tissue oedema hidden beyond the detection limits of T2-weighted Cardiovascular Magnetic Resonance (CMR). However, due to variability of baseline T2 values in volunteers, reference values need to be defined. Therefore, the aim of the study was to investigate the effects of age and sex on quantitative T2 mapping with a turbo gradient-spin-echo (GRASE) sequence at 1.5 T. For that reason, we studied sensitivity issues as well as technical and biological effects on GRASE-derived myocardial T2 maps. Furthermore, intra- and interobserver variability were calculated using data from a large volunteer group.

METHODS

GRASE-derived multiecho images were analysed using dedicated software. After sequence optimization, validation and sensitivity measurements were performed in muscle phantoms ex vivo and in vivo. The optimized parameters were used to analyse CMR images of 74 volunteers of mixed sex and a wide range of age with typical prevalence of hypertension and diabetes. Myocardial T2 values were analysed globally and according to the 17 segment model. Strain-encoded (SENC) imaging was additionally performed to investigate possible effects of myocardial strain on global or segmental T2 values.

RESULTS

Ex vivo studies in muscle phantoms showed, that GRASE-derived T2 values were comparable to those acquired by a standard multiecho spinecho sequence but faster by a factor of 6. Besides that, T2 values reflected tissue water content. The in vivo measurements in volunteers revealed intra- and interobserver correlations with R2=0.91 and R2=0.94 as well as a coefficients of variation of 2.4% and 2.2%, respectively. While global T2 time significantly decreased towards the heart basis, female volunteers had significant higher T2 time irrespective of myocardial region. We found no correlation of segmental T2 values with maximal systolic, diastolic strain or heart rate. Interestingly, volunteers´ age was significantly correlated to T2 time while that was not the case for other coincident cardiovascular risk factors.

CONCLUSION

GRASE-derived T2 maps are highly reproducible. However, female sex and aging with typical prevalence of hypertension and diabetes were accompanied by increased myocardial T2 values. Thus, sex and age must be considered as influence factors when using GRASE in a diagnostic manner.

Strain measurement by cardiovascular magnetic resonance in pediatric cancer survivors: validation of feature tracking against harmonic phase imaging

BACKGROUND

Left ventricular strain may be a more sensitive marker of left ventricular dysfunction than ejection fraction in pediatric cancer survivors after anthracycline therapy, but there is limited validation of strain measurement by feature tracking on cardiovascular magnetic resonance (MR) images.

OBJECTIVE

To compare left ventricular circumferential and radial strain by feature tracking vs. harmonic phase imaging analysis (HARP) in pediatric cancer survivors.

MATERIALS AND METHODS

Twenty-six patients (20.2 ± 5.6 years old) underwent cardiovascular MR at least 5 years after completing anthracycline therapy. Circumferential and radial strain were measured at the base, midventricle and apex from short-axis myocardial tagged images by HARP, and from steady-state free precession images by feature tracking.

RESULTS

Left ventricular ejection fraction more closely correlated with global circumferential strain by feature tracking (r = -0.63, P = 0.0005) than by HARP (r = -0.39, P = 0.05). Midventricular circumferential strain did not significantly differ by feature tracking or HARP (-20.8 ± 3.4 vs. -19.5 ± 2.5, P = 0.07), with acceptable limits of agreement. Midventricular circumferential strain by feature tracking strongly correlated with global circumferential strain by feature tracking (r = 0.87, P < 0.0001). Radial strain by feature tracking had poor agreement with HARP, particularly at higher values of radial strain. Intraobserver and interobserver reproducibility was excellent for feature tracking circumferential strain, but reproducibility was poor for feature tracking radial strain.

CONCLUSION

Midventricular circumferential strain by feature tracking is a reliable and reproducible measure of myocardial deformation in patients status post anthracycline therapy, while radial strain measurements are unreliable. Further studies are necessary to evaluate potential relation to long-term outcomes.

Cardiac magnetic resonance and computed tomography angiography for clinical imaging of stable coronary artery disease. Diagnostic classification and risk stratification

Despite advances in the pharmacologic and interventional treatment of coronary artery disease (CAD), atherosclerosis remains the leading cause of death in Western societies. X-ray coronary angiography has been the modality of choice for diagnosing the presence and extent of CAD. However, this technique is invasive and provides limited information on the composition of atherosclerotic plaque. Coronary computed tomography angiography (CCTA) and cardiac magnetic resonance (CMR) have emerged as promising non-invasive techniques for the clinical imaging of CAD. Hereby, CCTA allows for visualization of coronary calcification, lumen narrowing and atherosclerotic plaque composition. In this regard, data from the CONFIRM Registry recently demonstrated that both atherosclerotic plaque burden and lumen narrowing exhibit incremental value for the prediction of future cardiac events. However, due to technical limitations with CCTA, resulting in false positive or negative results in the presence of severe calcification or motion artifacts, this technique cannot entirely replace invasive angiography at the present time. CMR on the other hand, provides accurate assessment of the myocardial function due to its high spatial and temporal resolution and intrinsic blood-to-tissue contrast. Hereby, regional wall motion and perfusion abnormalities, during dobutamine or vasodilator stress, precede the development of ST-segment depression and anginal symptoms enabling the detection of functionally significant CAD. While CT generally offers better spatial resolution, the versatility of CMR can provide information on myocardial function, perfusion, and viability, all without ionizing radiation for the patients. Technical developments with these 2 non-invasive imaging tools and their current implementation in the clinical imaging of CAD will be presented and discussed herein.

Characterization of normal regional myocardial function by MRI cardiac tagging

PURPOSE

The aim of this study was to establish reference values for segmental myocardial strain measured by magnetic resonance (MR) cardiac tagging in order to characterize the regional function of the heart.

MATERIAL AND METHODS

We characterized the left ventricular (LV) systolic deformation in 39 subjects (26 women and 13 men, age 58.8 ± 11.6 years) whose cardiological study had not revealed any significant abnormality. The deformation was measured from MR-tagged (Siemens 1.5T MR) images using an algorithm based on sine wave modeling. Circumferential and radial peak systolic strain values along with the torsion angle and circumferential-longitudinal (CL) shear were determined in 16 LV segments in order to settle the reference values for these parameters.

RESULTS

Circumferential strain was highest at the anterior and lateral walls (-20.2 ± 4.0% and -21.8 ± 4.3%, respectively; P < 0.05) and was lowest at the base level (-17.2 ± 3.1% vs. -20.1 ± 3.1% "mid level," P < 0.05; -17.2 ± 3.1% vs. -20.3 ± 3.0% "apical level," P < 0.05). Radial strain highest values were from inferior and lateral walls (13.7 ± 7.4% and 12.8 ± 7.8%, respectively; P < 0.05) and it was lowest medially (9.4 ± 4.1% vs. 13.1 ± 4.1% "base level," P < 0.05; 9.4 ± 4.1% vs. 12.1 ± 4.4% "apical level," P < 0.05). Torsion angle (counterclockwise when viewed from the apex) increased with the distance from the base (7.9 ± 2.4° vs. 16.8 ± 4.4°, P < 0.05), and the highest and lowest values were found at lateral (medial lateral: 12.0 ± 4.4°, apical lateral: 25.1 ± 6.4°, P < 0.05) and septal wall (medial septal: 3.6 ± 2.1°, apical septal: 8.3 ± 5.3°, P < 0.05), respectively. These differences were found again in CL shear values, around the LV circumference. However, CL shear remained constant with increasing distance from the base (9.1 ± 2.6°, medium and 9.8 ± 2.4°, apex).

CONCLUSION

In summary, this study provides reference values for the assessment of regional myocardial function by MR cardiac tagging. Comparison of patient deformation parameters with normal deformation patterns may permit early detection of regional systolic dysfunction.

Assessing myocardial recovery following ST-segment elevation myocardial infarction: short- and long-term perspectives using cardiovascular magnetic resonance

Myocardial recovery after revascularization for ST-segment elevation myocardial infarction (STEMI) remains a significant diagnostic and, despite novel treatment strategies, a therapeutic challenge. Cardiovascular magnetic resonance (CMR) has emerged as a valuable clinical and research tool after acute STEMI. It represents the gold standard for functional and morphological evaluation of the left ventricle. Gadolinium-based perfusion and late-enhancement viability imaging has expanded our knowledge about the underlying pathologies of inadequate myocardial recovery. T2-weighted imaging of myocardial salvage after early reperfusion of the infarct-related artery underlines the effectiveness of current invasive treatment for STEMI. In the last decade, the number of publications on CMR after acute STEMI continued to rise, with no plateau in sight. Currently, CMR research is gathering robust prognostic data on standardized CMR protocols with the aim to substantially improve patient care and prognosis. Beyond established CMR protocols, more specific methods such as magnetic resonance relaxometry, myocardial tagging, 4D phase-contrast imaging and novel superparamagnetic contrast agents are emerging. This review will discuss the currently available data on the use of CMR after acute STEMI and take a brief look at developing new methods currently under investigation.

Left ventricular longitudinal strain measured by speckle tracking as a predictor of the decrease in left ventricular deformation in children with congenital stenosis of the aorta or coarctation of the aorta

Children born with a left ventricular outflow tract obstruction (LVOTO) can present with symptoms of left ventricular (LV) failure while ejection fraction (EF) is normal. A more sensitive parameter of systolic function might be obtained with speckle tracking echocardiography, which describes ventricular longitudinal deformation in strain values. It is presumed that despite a normal or only slight decrease in ejection fraction, patients with a LVOTO demonstrate aberrations in the longitudinal deformation of the left ventricle. In addition, it is expected that after a successful intervention, longitudinal deformation returns to normal values. Standard trans-thoracic echocardiography was performed on 33 consecutive patients with a LVOTO, either an isolated aortic coarctation (AoCo) or an isolated aortic stenosis (AoSt). Before intervention a significant decrease in strain values was observed compared with the control group (N = 40), with an additional decrease in strain values in the first week after intervention (N = 16). Strain values recovered after a mean follow-up period of 42 wk (N = 9), though normal values were never reached. In addition, patients with an AoCo had a smaller decrease in strain values compared with patients with AoSt. All strain values were measured with a concomitant ejection fraction between normal limits. It is concluded that patients with a congenital LVOTO have decreased ventricular systolic function measured as strain values, whereas their ejection fraction is within the normal range. Therefore, as ejection fraction may not be an accurate measure, speckle tracking-based strain may be significant in the identification of subtle changes in longitudinal deformation and may create opportunities for patients to benefit from early treatment for heart failure.

Comparison of SPAMM and SENC methods for evaluating peak circumferential strain at 3T

We compared peak circumferential strain (Ecc) values with spatial modulation of magnetization (SPAMM) and strain-encoded (SENC) magnetic resonance (MR) imaging at 3 tesla. Correlation coefficients of the averaged peak Ecc values of the 2 methods were statistically significant. However, the average peak Ecc value was significantly lower with SPAMM (-13.5%±3.3%) than with SENC (-21.6%±3.4%) (P<0.0001). The SENC method showed higher circumferential strain than the SPAMM method at 3T.

Layer-specific analysis of myocardial deformation for assessment of infarct transmurality: comparison of strain-encoded cardiovascular magnetic resonance with 2D speckle tracking echocardiography

AIMS

Separate analysis of endocardial and epicardial myocardial layer deformation has become possible using strain-encoded cardiovascular magnetic resonance (SENC) and 2D-dimensional speckle tracking echocardiography (Echo). This study evaluated and compared both modalities for the assessment of infarct transmurality as defined by late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR).

METHODS AND RESULTS

In 29 patients (age 62.4 ± 11.7 years, 23 male) with ischaemic cardiomyopathy, SENC using 1.5 T CMR and Echo were performed. Peak circumferential systolic strain of the endocardial and the epicardial layer of 304 myocardial segments was assessed by SENC and by Echo. The segmental transmurality of myocardial infarction was determined as relative amount of LGE (0%: no infarction; 1-50%: non-transmural infarction; 51-100%: transmural infarction). Endocardial and epicardial strain defined by SENC and by Echo differed significantly between segments of different infarct transmurality determined by CMR. Endocardial layer circumferential strain analysis by Echo and by SENC allowed distinction of segments with non-transmural infarction from non-infarcted segments with similar accuracy [area under the curve (AUC) 0.699 vs. 0.649, respectively, P = 0.239]. Epicardial layer circumferential strain analysis by Echo and by SENC allowed distinction of transmural from non-transmural myocardial infarction defined by LGE CMR with similar accuracy (AUC 0.721 vs. 0.664, respectively, P = 0.401). Endocardial strain by SENC correlated moderately with endocardial strain by Echo (r = 0.50; standard error of estimate = 5.2%).

CONCLUSION

Layer-specific analysis of myocardial deformation by Echo and by SENC allows discrimination between different transmurality categories of myocardial infarction with similar accuracy. However, accuracy of both methods is non-optimal, indicating that further tools for improvement should be evaluated in the future.

Quantitative analysis of endocardial and epicardial left ventricular myocardial deformation-comparison of strain-encoded cardiac magnetic resonance imaging with two-dimensional speckle-tracking echocardiography

BACKGROUND

Quantitative analysis of segmental myocardial deformation of different myocardial layers has become possible using strain-encoded cardiac magnetic resonance imaging (SENC) and speckle-tracking echocardiography (STE). We evaluated and compared the quantitative analysis of myocardial deformation using SENC and STE.

METHODS

In 44 patients (age 61 ± 13 years, 34 men), SENC by cardiac magnetic resonance imaging using a 1.5-Tesla whole-body scanner and two-dimensional STE were performed prospectively. Quantitative layer-specific analysis of segmental left ventricular function was performed to determine the peak circumferential and peak longitudinal systolic strain values using SENC and STE of an endocardial and epicardial myocardial layer. In addition, segmental function was defined as normokinetic, hypokinetic, or akinetic by visual analysis of the magnetic resonance imaging cine sequences.

RESULTS

The endocardial and epicardial strain defined by SENC or STE differed significantly between the visually defined segmental function states. The correlation of the peak circumferential endocardial strain by SENC versus STE (intraclass correlation coefficient [ICC] 0.493, 95% CI 0.358-0.597) tended to be better than the correlation of the circumferential epicardial strain using both methods (ICC 0.321, 95% CI 0.238-0.399). The correlation of the peak longitudinal endocardial strain by SENC and STE was similar (ICC 0.472, 95% CI 0.398-0.541), in contrast to the longitudinal epicardial strain analysis by both techniques (ICC 0.554, 95% CI 0.417-0.655). Circumferential strain analysis by STE allowed better distinction of the hypokinetic or akinetic segments from the normokinetic segments than did the circumferential strain analysis by SENC of the endocardial layer (area under the receiver operating characteristic curve [AUC ROC] 0.946 vs 0.884; P < .001) or epicardial layer (AUC ROC 0.884 vs 0.782; P < .001). Longitudinal strain analysis using STE and SENC of the endocardial layer (AUC ROC 0.851 vs 0.839; P = .5838) and epicardial layer (AUC ROC 0.849 vs 0.833; P = .4321) had similar diagnostic value for identifying the presence of hypokinetic and akinetic segments.

CONCLUSIONS

Quantitative analysis of segmental deformation by SENC and STE allowed accurate distinction of myocardial segments with different functional states. Circumferential endocardial strain analysis by STE allowed the best distinction of segments with impaired function from the normokinetic segments.

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.