Myocardial deformation characteristics assessed by cardiovascular magnetic resonance feature tracking in a healthy Chinese population

Purpose

To explore global/regional myocardial deformation across various layers, vascular distributions, specific levels and distinct walls in healthy individuals using cardiovascular magnetic resonance feature tracking (CMR-FT).

Methods

We selected a cohort of 55 healthy participants and CMR cine images were used to obtain the left ventricular (LV) peak longitudinal, circumferential, radial strains (LS, CS, RS). The characteristics of normal LV strain in various layers (endocardium, myocardium, epicardium), territories [left anterior descending artery (LAD), left circumflex artery (LCX), and right coronary artery (RCA)], levels (basal, middle, apical) and walls (anterior, septum, inferior, lateral) were compared.

Results

The absolute values of the LV global LS and CS gradually decreased from endocardium to epicardium. The absolute LV global RS (65.7 ± 47.7%) was maximum relative to LS (-22.0 ± 10.8%) and CS (-22.8 ± 7.7%). The absolute values of the LCX territorial strain were the largest compared with the LAD and RCA territorial strains. Regional RS, endo-CS and endo-LS gradually increased from the basal to the apical level. The LV lateral walls had the highest strain values (CS, LS, and RS).

Conclusions

Variations in normal LV strain values across various layers, territories, levels, and walls were observed, suggesting the necessity for careful clinical interpretation of these strain values. These findings also partially revealed the complexity of normal cardiac mechanics.

Adiposity influences on myocardial deformation: a cardiovascular magnetic resonance feature tracking study in people with overweight to obesity without established cardiovascular disease

The objective of this study was to assess whether dietary-induced weight loss improves myocardial deformation in people with overweight to obesity without established cardiovascular disease applying cardiovascular magnetic resonance (CMR) with feature tracking (FT) based strain analysis. Ninety people with overweight to obesity without established cardiovascular disease (age 44.6 ± 9.3 years, body mass index (BMI) 32.6 ± 4 kg/m2) underwent CMR. We retrospectively quantified FT based strain and LA size and function at baseline and after a 6-month hypocaloric diet, with either low-carbohydrate or low-fat intake. The study cohort was compared to thirty-four healthy normal-weight controls (age 40.8 ± 16.0 years, BMI 22.5 ± 1.4 kg/m2). At baseline, the study cohort with overweight to obesity without established cardiovascular disease displayed significantly increased global circumferential strain (GCS), global radial strain (GRS) and LA size (all p < 0.0001 versus controls) but normal global longitudinal strain (GLS) and normal LA ejection fraction (all p > 0.05 versus controls). Dietary-induced weight loss led to a significant reduction in GCS, GRS and LA size irrespective of macronutrient composition (all p < 0.01). In a population with overweight to obesity without established cardiovascular disease subclinical myocardial changes can be detected applying CMR. After dietary-induced weight loss improvement of myocardial deformation could be shown. A potential clinical impact needs further studies.

Simulating impaired left ventricular-arterial coupling in aging and disease: a systematic review

Aortic stenosis, hypertension, and left ventricular hypertrophy often coexist in the elderly, causing a detrimental mismatch in coupling between the heart and vasculature known as ventricular-vascular (VA) coupling. Impaired left VA coupling, a critical aspect of cardiovascular dysfunction in aging and disease, poses significant challenges for optimal cardiovascular performance. This systematic review aims to assess the impact of simulating and studying this coupling through computational models. By conducting a comprehensive analysis of 34 relevant articles obtained from esteemed databases such as Web of Science, Scopus, and PubMed until July 14, 2022, we explore various modeling techniques and simulation approaches employed to unravel the complex mechanisms underlying this impairment. Our review highlights the essential role of computational models in providing detailed insights beyond clinical observations, enabling a deeper understanding of the cardiovascular system. By elucidating the existing models of the heart (3D, 2D, and 0D), cardiac valves, and blood vessels (3D, 1D, and 0D), as well as discussing mechanical boundary conditions, model parameterization and validation, coupling approaches, computer resources and diverse applications, we establish a comprehensive overview of the field. The descriptions as well as the pros and cons on the choices of different dimensionality in heart, valve, and circulation are provided. Crucially, we emphasize the significance of evaluating heart-vessel interaction in pathological conditions and propose future research directions, such as the development of fully coupled personalized multidimensional models, integration of deep learning techniques, and comprehensive assessment of confounding effects on biomarkers.

Establishment of Cardiac Laterality

Formation of the vertebrate heart with its complex arterial and venous connections is critically dependent on patterning of the left-right axis during early embryonic development. Abnormalities in left-right patterning can lead to a variety of complex life-threatening congenital heart defects. A highly conserved pathway responsible for left-right axis specification has been uncovered. This pathway involves initial asymmetric activation of a nodal signaling cascade at the embryonic node, followed by its propagation to the left lateral plate mesoderm and activation of left-sided expression of the Pitx2 transcription factor specifying visceral organ asymmetry. Intriguingly, recent work suggests that cardiac laterality is encoded by intrinsic cell and tissue chirality independent of Nodal signaling. Thus, Nodal signaling may be superimposed on this intrinsic chirality, providing additional instructive cues to pattern cardiac situs. The impact of intrinsic chirality and the perturbation of left-right patterning on myofiber organization and cardiac function warrants further investigation. We summarize recent insights gained from studies in animal models and also some human clinical studies in a brief overview of the complex processes regulating cardiac asymmetry and their impact on cardiac function and the pathogenesis of congenital heart defects.

Late gadolinium enhanced cardiac MR derived radiomics approach for predicting all-cause mortality in cardiac amyloidosis: a multicenter study

OBJECTIVES

To evaluate the prognostic value of radiomics features based on late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) images in patients with cardiac amyloidosis (CA).

METHODS

This retrospective study included 120 CA patients undergoing CMR at three institutions. Radiomics features were extracted from global and three different segments (base, mid-ventricular, and apex) of left ventricular (LV) on short-axis LGE images. Primary endpoint was all-cause mortality. The predictive performance of the radiomics features and semi-quantitative and quantitative LGE parameters were compared by ROC. The AUC was used to observe whether Rad-score had an incremental value for clinical stage. The Kaplan-Meier curve was used to further stratify the risk of CA patients.

RESULTS

During a median follow-up of 12.9 months, 30% (40/120) patients died. There was no significant difference in the predictive performance of the radiomics model in different LV sections in the validation set (AUCs of the global, basal, middle, and apical radiomics model were 0.75, 0.77, 0.76, and 0.77, respectively; all p > 0.05). The predictive performance of the Rad-score of the base-LV was better than that of the LGE total enhancement mass (AUC:0.77 vs. 0.54, p < 0.001) and LGE extent (AUC: 0.77 vs. 0.53, p = 0.004). Rad-score combined with Mayo stage had better predictive performance than Mayo stage alone (AUC: 0.86 vs. 0.81, p = 0.03). Rad-score (≥ 0.66) contributed to the risk stratification of all-cause mortality in CA.

CONCLUSIONS

Compared to quantitative LGE parameters, radiomics can better predict all-cause mortality in CA, while the combination of radiomics and Mayo stage could provide higher predictive accuracy.

CLINICAL RELEVANCE STATEMENT

Radiomics analysis provides incremental value and improved risk stratification for all-cause mortality in patients with cardiac amyloidosis.

KEY POINTS

• Radiomics in LV-base was superior to LGE semi-quantitative and quantitative parameters for predicting all-cause mortality in CA. • Rad-score combined with Mayo stage had better predictive performance than Mayo stage alone or radiomics alone. • Rad-score ≥ 0.66 was associated with a significantly increased risk of all-cause mortality in CA patients.

Role of Cardiac Energetics in Aortic Stenosis Disease Progression: Identifying the High-risk Metabolic Phenotype

BACKGROUND

Severe aortic stenosis (AS) is associated with left ventricular (LV) hypertrophy and cardiac metabolic alterations with evidence of steatosis and impaired myocardial energetics. Despite this common phenotype, there is an unexplained and wide individual heterogeneity in the degree of hypertrophy and progression to myocardial fibrosis and heart failure. We sought to determine whether the cardiac metabolic state may underpin this variability.

METHODS

We recruited 74 asymptomatic participants with AS and 13 healthy volunteers. Cardiac energetics were measured using phosphorus spectroscopy to define the myocardial phosphocreatine to adenosine triphosphate ratio. Myocardial lipid content was determined using proton spectroscopy. Cardiac function was assessed by cardiovascular magnetic resonance cine imaging.

RESULTS

Phosphocreatine/adenosine triphosphate was reduced early and significantly across the LV wall thickness quartiles (Q2, 1.50 [1.21-1.71] versus Q1, 1.64 [1.53-1.94]) with a progressive decline with increasing disease severity (Q4, 1.48 [1.18-1.70]; P=0.02). Myocardial triglyceride content levels were overall higher in all the quartiles with a significant increase seen across the AV pressure gradient quartiles (Q2, 1.36 [0.86-1.98] versus Q1, 1.03 [0.81-1.56]; P=0.034). While all AS groups had evidence of subclinical LV dysfunction with impaired strain parameters, impaired systolic longitudinal strain was related to the degree of energetic impairment (r=0.219; P=0.03). Phosphocreatine/adenosine triphosphate was not only an independent predictor of LV wall thickness (r=-0.20; P=0.04) but also strongly associated with myocardial fibrosis (r=-0.24; P=0.03), suggesting that metabolic changes play a role in disease progression. The metabolic and functional parameters showed comparable results when graded by clinical severity of AS.

CONCLUSIONS

A gradient of myocardial energetic deficit and steatosis exists across the spectrum of hypertrophied AS hearts, and these metabolic changes precede irreversible LV remodeling and subclinical dysfunction. As such, cardiac metabolism may play an important and potentially causal role in disease progression.

Prognosis evaluation of chronic inflammatory cardiomyopathy with ring-like late gadolinium enhancement

AIMS

Ring-like late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) imaging is a special LGE pattern in patients with chronic inflammatory cardiomyopathy (infl-CMP), which is associated with cardiac dysfunction and ventricular remodelling and attributed to viral infection followed by bacterial and parasitic infections. Data on the combination of CMR imaging and clinical parameters that can add long-term prognostic value in patients with infl-CMP are still rare. We aimed to evaluate the prognostic value of CMR in risk stratification in this kind of patients.

METHODS AND RESULTS

A total of 319 consecutive patients with clinically suspected myocarditis were retrospectively identified. Forty-seven patients with ring-like LGE on CMR who diagnosed as infl-CMP, and 72 patients with other LGE pattern were eligible for standardized follow-up. The left ventricle (LV) and right ventricle function and mass were analyses by CMR. Myocardial strain of the ventricles was evaluated by feature tracking. Major (cardiac death, resuscitated cardiac arrest, ventricular assist device, transplantation, and appropriate implantable cardioverter-defibrillator shock) and minor (rehospitalization due to heart failure and sustained atrial fibrillation) adverse cardiovascular events were assessed during follow-up since the date of nCMR examination. Cox proportional hazards model was used to investigate which of the prognostic factors identified by univariable analysis were significantly associated with cardiac events. In the ring-like LGE group, adverse cardiac events occurred in 14 (31.11%) patients, including 7 deaths (15.56%), 6 (13.33%) heart-failure hospitalizations, and 1 (2.22%) case of sustained atrial fibrillation during the mean follow-up period of 70.15 ± 45.68 months (interquartile range: 32.83-103.71 months). No major or minor adverse cardiac event occurred in the other LGE pattern group, except rehospitalization in one patient due to arrhythmia. Further analyses of ring-like LGE group by univariable and Multivariable Cox proportional hazard regression analysis showed that body mass index (BMI) (hazard ratio [HR]: 0.54, 95% confidence interval [CI]: 0.40-0.73, P = 0.000), right ventricle cardiac index (RVCI) (HR: 0.31, 95% CI: 0.14-0.71, P = 0.002), LV basal peak circumferential strain (LV-PCSbasal ) (HR: 1.26, 95% CI: 1.11-1.43, P = 0.000) were independently associated with the long-term outcome. Receiver operator characteristic curve indicated that the cut-off of LV-PCSBasal was -7.95%, and it has added prognostic value to BMI and RVCI.

CONCLUSIONS

For infl-CMP patients with ring-like LGE on CMR, low BMI and RVCI were associated with a poor prognosis. LV-PCSBasal with a cut-off of -7.95% can add prognostic value for patients with infl-CMP who have ring-like LGE.

Motion-robust, blood-suppressed, reduced-distortion diffusion MRI of the liver

PURPOSE

To evaluate feasibility and reproducibility of liver diffusion-weighted (DW) MRI using cardiac-motion-robust, blood-suppressed, reduced-distortion techniques.

METHODS

DW-MRI data were acquired at 3T in an anatomically accurate liver phantom including controlled pulsatile motion, in eight healthy volunteers and four patients with known or suspected liver metastases. Standard monopolar and motion-robust (M1-nulled, and M1-optimized) DW gradient waveforms were each acquired with single-shot echo-planar imaging (ssEPI) and multishot EPI (msEPI). In the motion phantom, apparent diffusion coefficient (ADC) was measured in the motion-affected volume. In healthy volunteers, ADC was measured in the left and right liver lobes separately to evaluate ADC reproducibility between the two lobes. Image distortions were quantified using the normalized cross-correlation coefficient, with an undistorted T2-weighted reference.

RESULTS

In the motion phantom, ADC mean and SD in motion-affected volumes substantially increased with increasing motion for monopolar waveforms. ADC remained stable in the presence of increasing motion when using motion-robust waveforms. M1-optimized waveforms suppressed slow flow signal present with M1-nulled waveforms. In healthy volunteers, monopolar waveforms generated significantly different ADC measurements between left and right liver lobes ( p = 0 . 0078 $$ p=0.0078 $$ , reproducibility coefficients (RPC) =  470 × 1 0 - 6 $$ 470\times 1{0}^{-6} $$ mm 2 $$ {}^2 $$ /s for monopolar-msEPI), while M1-optimized waveforms showed more reproducible ADC values ( p = 0 . 29 $$ p=0.29 $$ , RPC = 220 × 1 0 - 6 $$ \mathrm{RPC}=220\times 1{0}^{-6} $$ mm 2 $$ {}^2 $$ /s for M1-optimized-msEPI). In phantom and healthy volunteer studies, motion-robust acquisitions with msEPI showed significantly reduced image distortion ( p < 0 . 001 $$ p<0.001 $$ ) compared to ssEPI. Patient scans showed reduction of wormhole artifacts when combining M1-optimized waveforms with msEPI.

CONCLUSION

Synergistic effects of combined M1-optimized diffusion waveforms and msEPI acquisitions enable reproducible liver DWI with motion robustness, blood signal suppression, and reduced distortion.

Cardiac Magnetic Resonance Imaging in Appraising Myocardial Strain and Biomechanics: A Current Overview

Subclinical alterations in myocardial structure and function occur early during the natural disease course. In contrast, clinically overt signs and symptoms occur during late phases, being associated with worse outcomes. Identification of such subclinical changes is critical for timely diagnosis and accurate management. Hence, implementing cost-effective imaging techniques with accuracy and reproducibility may improve long-term prognosis. A growing body of evidence supports using cardiac magnetic resonance (CMR) to quantify deformation parameters. Tissue-tagging (TT-CMR) and feature-tracking CMR (FT-CMR) can measure longitudinal, circumferential, and radial strains and recent research emphasize their diagnostic and prognostic roles in ischemic heart disease and primary myocardial illnesses. Additionally, these methods can accurately determine LV wringing and functional dynamic geometry parameters, such as LV torsion, twist/untwist, LV sphericity index, and long-axis strain, and several studies have proved their utility in prognostic prediction in various cardiovascular patients. More recently, few yet important studies have suggested the superiority of fast strain-encoded imaging CMR-derived myocardial strain in terms of accuracy and significantly reduced acquisition time, however, more studies need to be carried out to establish its clinical impact. Herein, the current review aims to provide an overview of currently available data regarding the role of CMR in evaluating myocardial strain and biomechanics.

Myocardial Segmentation of Tagged Magnetic Resonance Images with Transfer Learning Using Generative Cine-To-Tagged Dataset Transformation

The use of deep learning (DL) segmentation in cardiac MRI has the potential to streamline the radiology workflow, particularly for the measurement of myocardial strain. Recent efforts in DL motion tracking models have drastically reduced the time needed to measure the heart's displacement field and the subsequent myocardial strain estimation. However, the selection of initial myocardial reference points is not automated and still requires manual input from domain experts. Segmentation of the myocardium is a key step for initializing reference points. While high-performing myocardial segmentation models exist for cine images, this is not the case for tagged images. In this work, we developed and compared two novel DL models (nnU-net and Segmentation ResNet VAE) for the segmentation of myocardium from tagged CMR images. We implemented two methods to transform cardiac cine images into tagged images, allowing us to leverage large public annotated cine datasets. The cine-to-tagged methods included (i) a novel physics-driven transformation model, and (ii) a generative adversarial network (GAN) style transfer model. We show that pretrained models perform better (+2.8 Dice coefficient percentage points) and converge faster (6×) than models trained from scratch. The best-performing method relies on a pretraining with an unpaired, unlabeled, and structure-preserving generative model trained to transform cine images into their tagged-appearing equivalents. Our state-of-the-art myocardium segmentation network reached a Dice coefficient of 0.828 and 95th percentile Hausdorff distance of 4.745 mm on a held-out test set. This performance is comparable to existing state-of-the-art segmentation networks for cine images.

Multimodality Imaging in the Diagnosis and Assessment of Cardiac Amyloidosis

Amyloidosis is a rare disorder where abnormal protein aggregates are deposited in tissues forming amyloid fibrils, leading to progressive organ failure. Although any organ can be affected, cardiac involvement is the main cause of morbidity and mortality associated with amyloidosis as diagnosis is often delayed due to the indolent nature of the disease in some forms. An early diagnosis of disease and knowledge of the type/subtype of cardiac amyloidosis (CA) are essential for appropriate management and better outcome. Echocardiography is often the first line of investigation for patients suspected of CA and offers superior hemodynamic assessment. Although cardiovascular magnetic resonance (CMR) imaging is not diagnostic of CA, it provides vital clues to diagnosis and has a role in disease quantification and prognostication. Radiolabeled bone seeking tracers are the mainstay of diagnosis of CA and when combined with screening of monoclonal light chains, bone scintigraphy offers high sensitivity in diagnosing transthyretin type of CA. This review aims to describe the noninvasive imaging assessment and approach to diagnosis of patients with suspected CA. Imaging features of echocardiography, nuclear scintigraphy, and CMR are described with a brief mention on computed tomography.

Feasibility of one breath-hold cardiovascular magnetic resonance compressed sensing cine for left ventricular strain analysis

Objective

To investigate the feasibility of 3D left ventricular global and regional strain by using one breath-hold (BH) compressed sensing cine (CSC) protocol and determine the agreement between CSC and conventional cine (CC) protocols.

Methods

A total of 30 volunteers were enrolled in this study. Cardiovascular magnetic resonance (CMR) images were acquired using a 1.436 T magnetic resonance imaging (MRI) system. The CSC protocols included one BH CSC and the shortest BH CSC protocols with different parameters and were only performed in short-axis (SA) view following CC protocols. Left ventricular (LV) end-diastole volume (EDV), end-systole volume (ESV), stroke volume (SV), and ejection fraction (EF) global and regional strain were calculated by CC, one BH CSC, and shortest BH CSC protocols. The intraclass correlation coefficient (ICC) and coefficient of variance (CV) of these parameters were used to determine the agreement between different acquisitions.

Results

The agreement of all volumetric variables and EF between the CC protocol and one BH CSC protocol was excellent (ICC &gt; 0.9). EDV, ESV, and SV between CC and shortest BH CSC protocols also had a remarkable coherence (ICC &gt; 0.9). The agreement of 3D LV global strain assessment between CC protocol and one BH CSC protocol was good (ICC &gt; 0.8). Most CVs of variables were also good (CV &lt; 15%). ICCs of all variables were lower than 0.8. CVs of all parameters were higher than 15% except global longitudinal strain (GLS) between CC and shortest BH CSC protocols. The agreement of regional strain between CC and BH CSC protocols was heterogeneous (-0.2 &lt; ICC &lt; 0.7). Many variables of CVs were poor.

Conclusion

Notably, one BH CSC protocol can be used for 3D global strain analysis, along with a good correlation with the CC protocol. The regional strain should continue to be computed by the CC protocol due to poor agreement and a remarkable variation between the protocols. The shortest BH CSC protocol was insufficient to replace the CC protocol for 3D global and regional strain.

3D-speckle-tracking echocardiography correlates with cardiovascular magnetic resonance imaging diagnosis of acute myocarditis – An observational study

•

Regional changes in myocardial texture (as diagnosed by CMR) were significantly associated with regional impairment of circumferential, longitudinal, and radial strain, as well as regional 3D displacement and total 3D strain.

•

3D and 2D global longitudinal strain (GLS) showed higher diagnostic performance than well-known parameters associated with myocarditis, such as LVEF and LVEDV in our patient collective.

•

3D-speckle-tracking echocardiography offers a promising diagnostic tool in the diagnosis of myocarditis.

Background

The diagnostic importance of three-dimensional (3D) speckle-tracking strain-imaging echocardiography in patients with acute myocarditis remains unclear. The aim of this study was to test the diagnostic performance of 3D-speckle-tracking echocardiography compared to CMR (cardiovascular magnetic resonance imaging) for the diagnosis of acute myocarditis.

Methods and results

45 patients with clinically suspected myocarditis were enrolled in our study (29% female, mean age: 43.9 ± 16.3 years, peak troponin I level: 1.38 ± 3.51 ng/ml). 3D full-volume echocardiographic images were obtained and offline 2D as well as 3D speckle-tracking analysis of regional and global LV deformation was performed. All patients received CMR scans and myocarditis was diagnosed in 29 subjects based on original Lake-Louise criteria. The 16 patients, in whom myocarditis was excluded by CMR, served as controls. Regional changes in myocardial texture (diagnosed by CMR) were significantly associated with regional impairment of circumferential, longitudinal, and radial strain, as well as regional 3D displacement and total 3D strain. Interestingly, the 2D and 3D global longitudinal strain (GLS) showed higher diagnostic performance than well-known parameters associated with myocarditis, such as LVEF (as obtained by echocardiography and CMR) and LVEDV (as obtained by CMR).

Conclusions

In this study, we examined the use of 3D-speckle-tracking echocardiography in patients with acute myocarditis. Global longitudinal strain was significantly impaired in patients with acute myocarditis and correlated with CMR findings. Therefore, 3D echocardiography could become a useful diagnostic tool in the primary diagnosis of myocarditis.

The Dynamic Characteristics of Myocardial Contractility and Extracellular Volume in Type 2 Diabetes Mellitus Mice Investigated by 7.0T Cardiac Magnetic Resonance

Type 2 diabetes mellitus (T2DM) is associated with a high prevalence of diastolic dysfunction and congestive heart failure. A potential contributing factor is the accelerated accumulation of diffuse myocardial fibrosis and stiffness. Novel cardiac magnetic resonance (CMR) imaging techniques can identify both myocardial fibrosis and contractility quantitatively. This study aimed to investigate the dynamic characteristics of the myocardial strain and altered extracellular volume (ECV) fraction as determined by 7.0 T CMR in T2DM mice. C57Bl/6J mice were randomly divided into T2DM (fed a high-fat diet) and control (fed a normal diet) groups. They were scanned on 7.0 T MRI every 4 weeks until the end of week 24. The CMR protocol included multi-slice cine imaging to assess left ventricle strain and strain rate, and pre- and post-contrast T1 mapping images to quantify ECV. The ECV in the T2DM mice was significantly higher (p < 0.05) than that in the control group since week 12 with significantly impaired myocardial strain (p < 0.05). A significant linear correlation was established between myocardial strain and ECV (p < 0.001) and left ventricular-ejection fraction and ECV (p = 0.003). The results suggested that CMR feature tracking-derived myocardial strain analysis can assess functional abnormalities that may be associated with ECM alterations in diabetic cardiomyopathy, contributing to the study of diabetic therapy effects.

Myocardial Strain Evaluation with Cardiovascular MRI: Physics, Principles, and Clinical Applications

Myocardial strain is a measure of myocardial deformation, which is a more sensitive imaging biomarker of myocardial disease than the commonly used ventricular ejection fraction. Although myocardial strain is commonly evaluated by using speckle-tracking echocardiography, cardiovascular MRI (CMR) is increasingly performed for this purpose. The most common CMR technique is feature tracking (FT), which involves postprocessing of routinely acquired cine MR images. Other CMR strain techniques require dedicated sequences, including myocardial tagging, strain-encoded imaging, displacement encoding with stimulated echoes, and tissue phase mapping. The complex systolic motion of the heart can be resolved into longitudinal strain, circumferential strain, radial strain, and torsion. Myocardial strain metrics include strain, strain rate, displacement, velocity, torsion, and torsion rate. Wide variability exists in the reference ranges for strain dependent on the imaging technique, analysis software, operator, patient demographics, and hemodynamic factors. In anticancer therapy cardiotoxicity, CMR myocardial strain can help identify left ventricular dysfunction before the decline of ejection fraction. CMR myocardial strain is also valuable for identifying patients with left ventricle dyssynchrony who will benefit from cardiac resynchronization therapy. CMR myocardial strain is also useful in ischemic heart disease, cardiomyopathies, pulmonary hypertension, and congenital heart disease. The authors review the physics, principles, and clinical applications of CMR strain techniques. Online supplemental material is available for this article. ^©RSNA, 2022.

Sex-specific effects of daily tadalafil on diabetic heart kinetics in RECOGITO, a randomized, double-blind, placebo-controlled trial

Cyclic GMP-phosphodiesterase type 5 (PDE5) inhibition has been shown to counteract maladaptive cardiac changes triggered by diabetes in some but not all studies. We performed a single-center, 20-week, double-blind, randomized, placebo-controlled trial (NCT01803828) to assess sex differences in cardiac remodeling after PDE5 inhibition in patients with diabetic cardiomyopathy. A total of 122 men and women (45 to 80 years) with long-duration (>3 years) and well-controlled type 2 diabetes mellitus (T2DM; HbA1c < 86 mmol/mol) were selected according to echocardiographic signs of cardiac remodeling. Patients were randomly assigned (1:1) to placebo or oral tadalafil (20 mg, once daily). The primary outcome was to evaluate sex differences in cardiac torsion change. Secondary outcomes were changes in cardiovascular, metabolic, immune, and renal function. At 20 weeks, the treatment-by-sex interaction documented an improvement in cardiac torsion (-3.40°, -5.96; -0.84, P = 0.011) and fiber shortening (-1.19%, -2.24; -0.14, P = 0.027) in men but not women. The primary outcome could not be explained by differences in cGMP concentrations or tadalafil pharmacodynamics. In both sexes, tadalafil improved hsa-miR-199-5p expression, biomarkers of cardiovascular remodeling, albuminuria, renal artery resistive index, and circulating Klotho concentrations. Immune cell profiling revealed an improvement in low-grade chronic inflammation: Classic CD14⁺⁺CD16^- monocytes reduced, and Tie2⁺ monocytes increased. Nine patients (14.5%) had minor adverse reactions after tadalafil administration. Continuous PDE5 inhibition could offer a strategy to target cardiorenal complications of T2DM, with sex- and tissue-specific responses. Further studies are needed to confirm Klotho and hsa-miR-199-5p as markers for T2DM complications.

Longitudinal changes in cardiac function in Duchenne muscular dystrophy population as measured by magnetic resonance imaging

BACKGROUND

The lack of dystrophin in cardiomyocytes in Duchenne muscular dystrophy (DMD) is associated with progressive decline in cardiac function eventually leading to death by 20-40 years of age. The aim of this prospective study was to determine rate of progressive decline in left ventricular (LV) function in Duchenne muscular dystrophy (DMD) over 5 years.

METHODS

Short axis cine and grid tagged images of the LV were acquired in individuals with DMD (n = 59; age = 5.3-18.0 years) yearly, and healthy controls at baseline (n = 16, age = 6.0-18.3 years) on a 3 T MRI scanner. Grid-tagged images were analyzed for composite circumferential strain (ℇcc%) and ℇcc% in six mid LV segments. Cine images were analyzed for left ventricular ejection fraction (LVEF), LV mass (LVM), end-diastolic volume (EDV), end-systolic volume (ESV), LV atrioventricular plane displacement (LVAPD), and circumferential uniformity ratio estimate (CURE). LVM, EDV, and ESV were normalized to body surface area for a normalized index of LVM (LVMI), EDV (EDVI) and ESV (ESVI).

RESULTS

At baseline, LV ℇcc% was significantly worse in DMD compared to controls and five of the six mid LV segments demonstrated abnormal strain in DMD. Longitudinal measurements revealed that ℇcc% consistently declined in individuals with DMD with the inferior segments being more affected. LVEF progressively declined between 3 to 5 years post baseline visit. In a multivariate analysis, the use of cardioprotective drugs trended towards positively impacting cardiac measures while loss of ambulation and baseline age were associated with negative impact. Eight out of 17 cardiac parameters reached a minimal clinically important difference with a threshold of 1/3 standard deviation.

CONCLUSION

The study shows a worsening of circumferential strain in dystrophic myocardium. The findings emphasize the significance of early and longitudinal assessment of cardiac function in DMD and identify early biomarkers of cardiac dysfunction to help design clinical trials to mitigate cardiac pathology. This study provides valuable non-invasive and non-contrast based natural history data of cardiac changes which can be used to design clinical trials or interpret the results of current trials aimed at mitigating the effects of decreased cardiac function in DMD.

Patient-Specific Inverse Modeling of In Vivo Cardiovascular Mechanics with Medical Image-Derived Kinematics as Input Data: Concepts, Methods, and Applications

Inverse modeling approaches in cardiovascular medicine are a collection of methodologies that can provide non-invasive patient-specific estimations of tissue properties, mechanical loads, and other mechanics-based risk factors using medical imaging as inputs. Its incorporation into clinical practice has the potential to improve diagnosis and treatment planning with low associated risks and costs. These methods have become available for medical applications mainly due to the continuing development of image-based kinematic techniques, the maturity of the associated theories describing cardiovascular function, and recent progress in computer science, modeling, and simulation engineering. Inverse method applications are multidisciplinary, requiring tailored solutions to the available clinical data, pathology of interest, and available computational resources. Herein, we review biomechanical modeling and simulation principles, methods of solving inverse problems, and techniques for image-based kinematic analysis. In the final section, the major advances in inverse modeling of human cardiovascular mechanics since its early development in the early 2000s are reviewed with emphasis on method-specific descriptions, results, and conclusions. We draw selected studies on healthy and diseased hearts, aortas, and pulmonary arteries achieved through the incorporation of tissue mechanics, hemodynamics, and fluid-structure interaction methods paired with patient-specific data acquired with medical imaging in inverse modeling approaches.

Reduced myocardial septal function assessed by cardiac magnetic resonance feature tracking in patients with hypertrophic obstructive cardiomyopathy: associated with histological myocardial fibrosis and ventricular arrhythmias

AIMS

Echocardiographic studies suggest that strain is related to myocardial fibrosis (MF) and ventricular arrhythmias (VA) in hypertrophic cardiomyopathy (HCM) patients. Cardiac magnetic resonance feature tracking (CMR-FT) also allows strain analysis, but little is known whether it provides incremental value to late gadolinium enhancement imaging (LGE). This study aimed to explore the relationship between CMR-FT-derived strain parameters and histopathology MF and VA and its incremental value to LGE in obstructive HCM (HOCM) patients undergoing septal myectomy.

METHODS AND RESULTS

One hundred and twenty-three symptomatic HOCM patients underwent CMR examination, followed by septal myectomy. The abnormally increased histological MF was defined as higher than the mean + 2 standard deviation (SD) of nine control autopsy subjects who had no history of cardiovascular disease. Septal strain parameters and septal LGE were evaluated at the site of surgical myectomy. Among HOCM patients without LGE, septal circumferential (P = 0.003), longitudinal (P = 0.001), and radial (P = 0.02) strains were significantly impaired in patients with increased histological MF than those without. Histological MF was significantly associated with septal circumferential strain (r = 0.32, P < 0.001), septal longitudinal strain (r = 0.42, P < 0.001), and septal radial strain (r = -0.27, P = 0.003). On multivariate analysis, septal longitudinal strain was independently associated with histological MF [β, 0.19 (0.05-0.34); P = 0.01], and VA [odds ratio, 1.10 (1.01-1.19); P = 0.02]. Moreover, septal longitudinal strain was incremental to septal %LGE in detecting increased MF (P = 0.001) and VA (P = 0.048).

CONCLUSIONS

Septal longitudinal strain at CMR is independently related to histological MF and occurrence of VA in HOCM patients. Moreover, it provides incremental value over LGE in detecting increased MF and VA.

Preliminary study on the diagnostic value of cardiac magnetic resonance feature tracking for malignant ventricular arrhythmias in non-ischemic dilated cardiomyopathy

Background

Patients with nonischemic dilated cardiomyopathy (NIDCM) and malignant ventricular arrhythmia (MVA) often have a poor prognosis and a high risk of sudden cardiac death. Although the diagnosis of MVA is straightforward by electrocardiogram (ECG), the underlying abnormalities of ventricular mechanics in these patients are unknown. This study aims to preliminarily explore the value of cardiac magnetic resonance feature tracking (CMR-FT) for MVA in dilated cardiomyopathy.

Methods

In this retrospective study, patients with NIDCM who met inclusion criteria were divided into an MVA group and a non-MVA group (included from January 2018 to September 2021). The interobserver agreement of myocardial strain parameters, including global longitudinal strain (GLS), global circumferential strain (GCS) and global radial strain (GRS), were tested. The GLS, GCS, GRS, left ventricular ejection fraction (LVEF), T_peak-T_end interval on ECG and brain natriuretic peptide (BNP) were compared between groups. Single-factor and multifactor receiver operating characteristic (ROC) curve analyses were conducted to calculate the area under the ROC curve (AUC), cut-off point, sensitivity, and specificity of these parameters in predicting MVA in NIDCM.

Results

A total of 161 NIDCM patients were included (54 in the MVA group). GLS, GCS, and GRS had good interobserver agreement (all intraclass correlation coefficients >0.80). The absolute GLS and GCS, GRS and LVEF were lower in the MVA group than the non-MVA group (P<0.001), T_peak-T_end and BNP were higher (P<0.001). Single-factor ROC curve analysis showed that GLS, GCS and GRS had certain diagnostic value for MVA (AUC =0.795, 0.802, and 0.754, respectively). Among them, GCS had higher sensitivity and specificity (GCS 0.796/0.776, GLS 0.778/0.757, GRS 0.741/0.692). Multifactor ROC curve analysis showed the combination of GLS and GCS (AUC =0.810), the combination of GCS and GRS (AUC =0.802), the combination of GLS and GRS (AUC =0.787), the combination of GLS, GCS, and GRS (AUC =0.810).

Conclusions

The three-dimensional myocardial strain parameters (especially GLS and GCS) measured by CMR-FT had certain diagnostic value and could reflect the underlying abnormality of ventricular mechanics of NIDCM with MVA.

Real-time radial tagging for quantification of left ventricular torsion

PURPOSE

To develop a real-time radial tagging MRI for accurate measurement of rotational motion and twist of the left ventricle (LV).

METHODS

A FLASH-based radial tagging sequence with an undersampled radial reading scheme was developed for both single and double-slice imaging in real-time. The Polar Fourier Transform was used for reconstruction to push the undersampling artifacts out of a reduced FOV. The developed technique was used to image five normal subjects during rest, plus one during both exercise and rest conditions. LV rotational motions were estimated for five consecutive cardiac cycles in all cases. The process was validated using a numerical phantom. The real-time measurement of global rotational motion was compared with those measured from a non-real-time exam using linear regression analysis and the Bland-Altman plot.

RESULTS

The real-time acquisition was performed successfully with a temporal resolution of 46.2 ms. Image quality was sufficient for the reproducible calculation of rotation at rest and exercise. The feasibility of double-slice acquisition on human was further studied and a real-time twist of the left ventricle was demonstrated. The difference between LV global rotations from real-time and non-real-time approaches was 0.27 degrees. A significant reverse recoiling, induced by exercise, was reproducibly measured by the technique.

CONCLUSION

A real-time radial tagging MRI technique was developed based on the undersampled radial acquisition and Polar Fourier Transform reconstruction, for accurate measuring of the heart rotational motion and twist. The technique was able to extract a meaningful change of diastolic recoiling under stress test conditions during physical activities (cycling).

Real-world clinical validity of cardiac magnetic resonance tissue tracking in primitive hypertrophic cardiomyopathy

OBJECTIVE

Cardiac magnetic resonance (CMR) is an uncontested diagnostic tool for identifying and assessing hypertrophic cardiomyopathy (HCM) patients. Concerning the necessity to identify valid prognosticators for predicting the individual risk of clinical evolution, this study aimed to evaluate the clinical validity of CMR tissue tracking (TT) analysis in patients affected by primitive HCM in a real-world setting.

METHODS

This historical prospective study included 33 patients. Diagnostic validity and clinical validation were assessed for strain values. CMR-TT diagnostic validity was studied comparing HCM patients with healthy control groups and phenotypic presentation of HCM. The impact of strain values and all phenotypic disease characteristics were assessed in a long-term follow-up study.

RESULTS

The inter-reading agreement was good for all strain parameters. Significant differences were observed between the control group and HCM patients. Similarly, hypertrophic and LGE + segments showed lower deformability than healthy segments. The AUC of predictive model, including conventional risk factors for MACE occurrence and all strain values, reached 98% of diagnostic concordance (95% CI .94-1; standard error: .02; p value .0001), compared to conventional risk factors only (86%; 95% CI .73-99; standard error: .07; p value .002).

CONCLUSION

In patients with primitive HCM, CMR-TT strain proves high clinical validity providing independent and non-negligible prognostic advantages over clinical features and traditional CMR markers.

Cardiac magnetic resonance techniques: Our experience on wide bore 3 tesla magnetic resonance system

Cardiovascular magnetic resonance (CMR) has become a widely adapted imaging modality in the diagnosis and management of patients with cardiovascular diseases. It provides unparalleled data of cardiac function and myocardial morphology. Majority of CMR imaging is currently being performed on 1.5 Tesla (T) MR systems. Over the last many years, the cardiac imaging protocols have been standardized and optimized in the 1.5T systems. 3T MR systems are now being used more and more in small and large institutions in our country due to their proven advantages in the field of neuro, body, and musculoskeletal imaging. Cardiac imaging on 3T system can be a double-edged sword. On one hand, it may provide nondiagnostic images due to significant artifacts, and on the other hand, it may complete the examination in quick time and provide excellent quality images. It is therefore important for the user to be aware of the potential pitfalls of CMR in 3T systems and also the necessary steps to avoid them. In this study, we discuss various challenges and advantages of performing CMR in a 3T system. We also present potential technical solutions to improve the image quality.

Myocardial Strain Imaging in Resistant Hypertension

PURPOSE OF REVIEW

Resistant hypertension (RH) is a major contributor to cardiovascular diseases and is associated with increased all-cause and cardiovascular mortality. Cardiac changes such as impaired left ventricular (LV) function, left ventricular hypertrophy (LVH), myocardial fibrosis, and enlarged left atrium (LA) are consequences of chronic exposure to an elevated blood pressure. The purpose of this review article is to demonstrate the potential benefits of using STE as a non-invasive imaging technique in the assessment of cardiac remodeling in patients with hypertension and specifically in uncontrolled and RH population.

RECENT FINDINGS

It is well-recognized that conventional transthoracic echocardiography is a useful analytic imaging modality to evaluate hypertension-mediated organ damage (HMOD) and in a resistant hypertensive population. More recently two-dimensional speckle tracking echocardiography (STE) has been utilized to provide further risk assessment to this population. Recent data has shown that STE is a new promising echocardiographic marker to evaluate early stage LV dysfunction and myocardial fibrosis over conventional 2D parameters in patients with cardiovascular diseases.

HARP-I: A Harmonic Phase Interpolation Method for the Estimation of Motion From Tagged MR Images

We proposed a novel method called HARP-I, which enhances the estimation of motion from tagged Magnetic Resonance Imaging (MRI). The harmonic phase of the images is unwrapped and treated as noisy measurements of reference coordinates on a deformed domain, obtaining motion with high accuracy using Radial Basis Functions interpolations. Results were compared against Shortest Path HARP Refinement (SP-HR) and Sine-wave Modeling (SinMod), two harmonic image-based techniques for motion estimation from tagged images. HARP-I showed a favorable similarity with both methods under noise-free conditions, whereas a more robust performance was found in the presence of noise. Cardiac strain was better estimated using HARP-I at almost any motion level, giving strain maps with less artifacts. Additionally, HARP-I showed better temporal consistency as a new method was developed to fix phase jumps between frames. In conclusion, HARP-I showed to be a robust method for the estimation of motion and strain under ideal and non-ideal conditions.

Hyperparameter optimisation and validation of registration algorithms for measuring regional ventricular deformation using retrospective gated computed tomography images

Recent dose reduction techniques have made retrospective computed tomography (CT) scans more applicable and extracting myocardial function from cardiac computed tomography (CCT) images feasible. However, hyperparameters of generic image intensity-based registration techniques, which are used for tracking motion, have not been systematically optimised for this modality. There is limited work on their validation for measuring regional strains from retrospective gated CCT images and open-source software for motion analysis is not widely available. We calculated strain using our open-source platform by applying an image registration warping field to a triangulated mesh of the left ventricular endocardium. We optimised hyperparameters of two registration methods to track the wall motion. Both methods required a single semi-automated segmentation of the left ventricle cavity at end-diastolic phase. The motion was characterised by the circumferential and longitudinal strains, as well as local area change throughout the cardiac cycle from a dataset of 24 patients. The derived motion was validated against manually annotated anatomical landmarks and the calculation of strains were verified using idealised problems. Optimising hyperparameters of registration methods allowed tracking of anatomical measurements with a mean error of 6.63% across frames, landmarks, and patients, comparable to an intra-observer error of 7.98%. Both registration methods differentiated between normal and dyssynchronous contraction patterns based on circumferential strain (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$p_1=0.0065$$\end{document}p1=0.0065, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$p_2=0.0011$$\end{document}p2=0.0011). To test whether a typical 10 temporal frames sampling of retrospective gated CCT datasets affects measuring cardiac mechanics, we compared motion tracking results from 10 and 20 frames datasets and found a maximum error of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$8.51\pm 0.8\%$$\end{document}8.51±0.8%. Our findings show that intensity-based registration techniques with optimal hyperparameters are able to accurately measure regional strains from CCT in a very short amount of time. Furthermore, sufficient sensitivity can be achieved to identify heart failure patients and left ventricle mechanics can be quantified with 10 reconstructed temporal frames. Our open-source platform will support increased use of CCT for quantifying cardiac mechanics.

Cardiac involvement in COVID-19 patients: mid-term follow up by cardiovascular magnetic resonance

BACKGROUND

Coronavirus disease 2019 (COVID-19) induces myocardial injury, either direct myocarditis or indirect injury due to systemic inflammatory response. Myocardial involvement has been proved to be one of the primary manifestations of COVID-19 infection, according to laboratory test, autopsy, and cardiovascular magnetic resonance (CMR). However, the middle-term outcome of cardiac involvement after the patients were discharged from the hospital is yet unknown. The present study aimed to evaluate mid-term cardiac sequelae in recovered COVID-19 patients by CMR METHODS: A total of 47 recovered COVID-19 patients were prospectively recruited and underwent CMR examination. The CMR protocol consisted of black blood fat-suppressed T2 weighted imaging, T2 star mapping, left ventricle (LV) cine imaging, pre- and post-contrast T1 mapping, and late gadolinium enhancement (LGE). LGE were assessed in mixed both recovered COVID-19 patients and healthy controls. The LV and right ventricle (RV) function and LV mass were assessed and compared with healthy controls.

RESULTS

A total of 44 recovered COVID-19 patients and 31 healthy controls were studied. LGE was found in 13 (30%) of COVID-19 patients. All LGE lesions were located in the mid myocardium and/or sub-epicardium with a scattered distribution. Further analysis showed that LGE-positive patients had significantly decreased LV peak global circumferential strain (GCS), RV peak GCS, RV peak global longitudinal strain (GLS) as compared to non-LGE patients (p < 0.05), while no difference was found between the non-LGE patients and healthy controls.

CONCLUSION

Myocardium injury existed in 30% of COVID-19 patients. These patients have depressed LV GCS and peak RV strains at the 3-month follow-up. CMR can monitor the COVID-19-induced myocarditis progression, and CMR strain analysis is a sensitive tool to evaluate the recovery of LV and RV dysfunction.

Layer-Specific Strain Is Preload Dependent: Comparison between Speckle-Tracking Echocardiography and Cardiac Magnetic Resonance Feature-Tracking

BACKGROUND

Speckle-tracking echocardiographic (STE) imaging and cardiac magnetic resonance feature-tracking (CMR-FT) are novel imaging techniques enabling layer-specific quantification of myocardial deformation. Conventional echocardiographic parameters are load dependent, but few studies have investigated the effects of loading conditions on STE and CMR-FT layer-specific strain and the interchangeability of the two modalities. The aim of this study was to evaluate the effects of acute preload augmentation by saline infusion on STE and CMR-FT longitudinal and circumferential layer-specific strain parameters and their intermodal agreement.

METHODS

A total of 80 subjects, including 41 control subjects (mean age, 40 ± 12 years; 49% men) and 39 patients with cardiac disease (mean age, 47 ± 15 years; 92% men) were examined using STE and CMR-FT layer-specific strain analysis before and after saline infusion (median, 2.0 L) with quantification of transmural global longitudinal strain (GLS), epicardial GLS, endocardial GLS, transmural global circumferential strain (GCS), epicardial GCS, and endocardial GCS in addition to epicardial-endocardial gradients. Bland-Altman plots and Pearson correlation coefficients were used to evaluate agreement between the two modalities across all strain parameters.

RESULTS

Acute saline infusion increased all STE and CMR-FT layer-specific strain parameters in both groups. STE and CMR-FT GLS increased by 1.4 ± 1.5% and 1.5 ± 2.0% (P < .001) in control subjects and by 0.9 ± 1.8% and 0.9 ± 1.9% (P < .001) in patients with cardiac disease. STE and CMR-FT GCS increased by 2.0 ± 2.2% and 1.8 ± 2.3% (P < .001) in control subjects and by 1.8 ± 2.3% and 1.7 ± 3.6% in patients with cardiac disease (P < .001 and P = .03). STE longitudinal strain correlated strongly with corresponding CMR-FT longitudinal strain (GLS, epicardial GLS, and endocardial GLS: r = 0.81, r = 0.82, and r = 0.81, respectively) despite poor intermodal agreement (bias ± limits of agreement, -2.84 ± 4.06%, 0.16 ± 3.68%, and 2.33 ± 3.52%, respectively) whereas GCS, epicardial GCS, and endocardial GCS correlated weakly between the two modalities (r = 0.28, r = 0.19, and r = 0.34, respectively) and displayed poor intermodal agreement (bias ± limits of agreement, -1.33 ± 6.86%, 4.43 ± 6.49%, and -9.92 ± 8.55%, respectively).

CONCLUSIONS

STE and CMR-FT longitudinal and circumferential layer-specific strain parameters are preload dependent in both control subjects and patients with cardiac disease. STE and CMR-FT longitudinal layer-specific strain parameters are strongly correlated, whereas circumferential layer-specific strain parameters are weakly correlated. STE and CMR-FT longitudinal and circumferential strain should not be used interchangeably, because of poor intermodal agreement.

Cardiac MRI Assessment of Mouse Myocardial Infarction and Regeneration

Small animal models are indispensable for cardiac regeneration research. Studies in mouse and rat models have provided important insights into the etiology and mechanisms of cardiovascular diseases and accelerated the development of therapeutic strategies. It is vitally important to be able to evaluate the therapeutic efficacy and have reliable surrogate markers for therapeutic development for cardiac regeneration research. Magnetic resonance imaging (MRI), a versatile and noninvasive imaging modality with excellent penetration depth, tissue coverage, and soft-tissue contrast, is becoming a more important tool in both clinical settings and research arenas. Cardiac MRI (CMR) is versatile, noninvasive, and capable of measuring many different aspects of cardiac functions, and, thus, is ideally suited to evaluate therapeutic efficacy for cardiac regeneration. CMR applications include assessment of cardiac anatomy, regional wall motion, myocardial perfusion, myocardial viability, cardiac function assessment, assessment of myocardial infarction, and myocardial injury. Myocardial infarction models in mice are commonly used model systems for cardiac regeneration research. In this chapter, we discuss various CMR applications to evaluate cardiac functions and inflammation after myocardial infarction.

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.

Comprehensive enhanced methodology of an MRI-based automated left-ventricular chamber quantification algorithm and validation in chemotherapy-related cardiotoxicity

Purpose: To comprehensively outline the methodology of a fully automated, MRI motion-guided, left-ventricular (LV) chamber quantification algorithm that enhances a similar, existing semi-automated approach. Additionally, to validate the motion-guided technique in comparison to chamber quantification with a vendor tool in post-chemotherapy breast cancer patients susceptible to cardiotoxicity. Approach: LV deformation data were acquired with the displacement encoding with stimulated echoes (DENSE) sequence on N = 21 post-chemotherapy female patients and N = 21 age-matched healthy females. The new chamber quantification algorithm consists of detecting LV boundary motion via a combination of image quantization and DENSE phase-encoded displacements. LV contractility was analyzed via chamber quantification and computations of 3D strains and torsion. For validation, estimates of chamber quantification with the motion-guided algorithm on DENSE and steady-state free precession (SSFP) acquisitions, and similar estimates with an existing vendor tool on DENSE acquisitions were compared via repeated measures analysis. Patient results were compared to healthy subjects for observing abnormalities. Results: Repeated measures analysis showed similar LV ejection fractions (LVEF), 59 % ± 6 % , 58 % ± 6 % , and 58 % ± 6 % , p = 0.2 , by applying the motion-guided algorithm on DENSE and SSFP and vendor tool on DENSE acquisitions, respectively. Differences found between patients and healthy subjects included enlarged basal diameters ( 5.0 ± 0.5    cm versus 4.4 ± 0.5    cm , p < 0.01 ), torsions ( p < 0.001 ), and longitudinal strains ( p < 0.001 ), but not LVEF ( p = 0.1 ). Conclusions: Measurement similarities between new and existing tools, and between DENSE and SSFP validated the motion-guided algorithm and differences found between subpopulations demonstrate the ability to detect contractile abnormalities.

Assessment of Pericardial Disease with Cardiovascular MRI

Disorders of the pericardium are common and can result in significant morbidity and mortality. Advances in multimodality imaging have enhanced our ability to diagnose and stage pericardial disease and improve our understanding of the pathophysiology of the disease. Cardiovascular MRI (CMR) can be used to define pericardial anatomy, identify the presence and extent of active pericardial inflammation, and assess the hemodynamic consequences of pericardial disease. In this way, CMR can guide the judicial use of antiinflammatory and immune modulatory medications and help with timing of pericardiectomy. CMR can also be used to diagnose congenital disorders of the pericardium. Furthermore, CMR can be used to define pericardial masses and understand their malignant potential.

Early diagnosis of chemotherapy-induced cardiotoxicity by cardiac MRI

Survival rate in cancer patients has improved over the course of the years. In cancer survivors, cardiovascular disease is the second leading cause of mortality and early detection and serial monitoring of cardiotoxicity are key factors towards the improvement of patients' outcomes. This review article will provide an overview of the existing literature regarding the tools that MRI can offer in the early diagnosis of myocardial damage.

Characteristics of the left ventricular three-dimensional maximum principal strain using cardiac computed tomography: reference values from subjects with normal cardiac function

OBJECTIVES

This study evaluated the characteristics of left ventricular maximum principal strain (LV-MPS) using cardiac CT in subjects with normal LV function.

METHODS

Of 973 subjects who underwent retrospective electrocardiogram-gated cardiac CT using a third-generation dual-source CT without beta-blocker administration, 31 subjects with preserved LV ejection fraction ≥ 55% assessed by echocardiography without coronary artery stenosis and cardiac pathology were retrospectively identified. CT images were reconstructed every 5% (0-95%) of the RR interval. LV-MPS and the time to peak (TTP) were analyzed using the 16-segment model and compared among three levels (base, mid, and apex) and among four regions (anterior, septum, inferior, and lateral) using the Steel-Dwass test. The intra- and inter-observer reproducibilities for LV-MPS were calculated using intraclass correlation coefficients (ICCs).

RESULTS

The intra- and inter-observer ICCs (95% confidence interval) for peak LV-MPS were 0.96 (0.94-0.97) and 0.94 (0.92-0.96), respectively. The global peak LV-MPS (median, inter-quantile range) was 0.59 (0.55-0.72). The regional LV-MPS significantly increased in the order of the basal (0.54, 0.49-0.59), mid-LV (0.57, 0.53-0.65), and apex (0.68, 0.60-0.84) (p < 0.05, in each), and was significantly higher in the lateral wall (0.66, 0.60-0.77), while that in the septal region (0.47, 0.44-0.54) was the lowest among the four LV regions (all p < 0.05). No significant difference in TTP was seen among the myocardial levels and regions.

CONCLUSION

CT-derived LV-MPS is reproducible and quantitatively represents synchronized myocardial contraction with heterogeneous values in subjects with normal LV function.

KEY POINTS

• CT-derived left ventricular maximum principal strain analysis allows highly reproducible quantitative assessments of left ventricular myocardial contraction. • In subjects with normal cardiac function, the peak value of CT-derived left ventricular maximum principal strain is the highest in the apical level and in the lateral wall and the lowest in the septum. • The regional peak left ventricular maximum principal strain shows intra-ventricular heterogeneity on a per-patient basis, but myocardial contraction is globally synchronized in subjects with normal cardiac function seen on cardiac CT.

Feature-tracking-based strain analysis - a comparison of tracking algorithms

PURPOSE

Optical flow feature-tracking (FT) strain assessment is increasingly being employed scientifically and clinically. Several software packages, employing different algorithms, enable computation of FT-derived strains. The aim of this study is to investigate the impact of the underlying algorithm on the validity and robustness of FT-derived strain results.

MATERIAL AND METHODS

CSPAMM and SSFP cine sequences were acquired in 30 subjects (15 patients with aortic stenosis and associated secondary hypertrophic cardiomyopathy, and 15 controls) in identical midventricular short-axis locations. Global peak systolic circumferential strain (PSCS) was calculated using tagging and feature-tracking software with different algorithms (non-rigid, elastic image registration, and blood myocardial border tracing). Intermodality agreement and intra- as well inter-observer variability were assessed.

RESULTS

Intermodality/inter-algorithm comparison for global PSCS using Friedman's test revealed statistically significant differences (tagging vs. blood myocardial border tracing algorithm). Intermodality assessment revealed the highest correlation between tagging and non-rigid, elastic image registration (r = 0.84), while correlation between tagging and blood myocardial border tracing (r = 0.36) and between the two feature-tracking software packages (r = 0.5) were considerably lower.

CONCLUSIONS

The type of algorithm employed during feature-tracking strain assessment has a significant impact on the results. The non-rigid, elastic image registration algorithm produces more precise and reproducible results than the blood myocardium tracing algorithm.

How His bundle pacing prevents and reverses heart failure induced by right ventricular pacing

Ideal heart performance demands vigorous systolic contractions and rapid diastolic relaxation. These sequential events are precisely timed and interdependent and require the rapid synchronous electrical stimulation provided by the His-Purkinje system. Right ventricular (RV) pacing creates slow asynchronous electrical stimulation that disrupts the timing of the cardiac cycle and results in left ventricular (LV) mechanical asynchrony. Long-term mechanical asynchrony produces LV dysfunction, remodeling, and clinical heart failure. His bundle pacing preserves synchronous electrical and mechanical LV function, prevents or reverses RV pacemaker-induced remodeling, and reduces heart failure.

Cardiovascular magnetic resonance-derived myocardial strain in asymptomatic heart transplanted patients and its correlation with late gadolinium enhancement

OBJECTIVES

To investigate whether cardiovascular magnetic resonance (CMR)-derived myocardial strains were abnormal in asymptomatic heart transplant (HT) patients with normal left ventricular ejection fraction (LVEF) and to detect the relationship between CMR-derived myocardial strain parameters and late gadolinium enhancement (LGE) in asymptomatic HT patients.

METHODS

A total of 72 HT patients and 35 healthy volunteers underwent 1.5-T MR scanning. The examination protocol included basic cine imaging and LGE. The deformation registration algorithm (DRA) and feature tracking (FT) software were used for the strain analyses. Myocardial strain measurements included left ventricular global longitudinal strain (LVGLS), LV global circumferential strain (LVGCS), LV global radial strain (LVGRS) and right ventricular longitudinal strain (RVLS).

RESULTS

Compared with healthy volunteers, HT patients had significantly decreased DRA- and FT- derived myocardial strain measurements (all p < 0.05). There was a significant correlation and high reproducibility between the DRA- and FT-derived strain parameters. Both CMR-derived LVGLS and LVGRS were significantly related to the presence of LGE, and multivariate logistic regression analyses showed that the LVGLS measurement obtained from both techniques was independently associated with the presence of LGE. The odds ratios (ORs) for DRA- and FT-LVGLS were 1.340 and 1.342, respectively.

CONCLUSIONS

Asymptomatic HT patients with preserved LVEF exhibited reduced myocardial strain parameters. The CMR-derived LVGLS was independently related to the presence of LGE in HT patients.

KEY POINTS

• Reduced myocardial strain parameters were found in asymptomatic heart transplanted (HT) patients with normal left ventricular ejection fraction (LVEF). • The deformation registration algorithm (DRA) and feature tracking (FT)-derived strains in asymptomatic HT patients had high reproducibility. • DRA- and FT-derived LVGLS had an independent relationship with late gadolinium enhancement (LGE) in asymptomatic HT patients.

Fully Automated Myocardial Strain Estimation from Cardiovascular MRI-tagged Images Using a Deep Learning Framework in the UK Biobank

PURPOSE

To demonstrate the feasibility and performance of a fully automated deep learning framework to estimate myocardial strain from short-axis cardiac MRI-tagged images.

MATERIALS AND METHODS

In this retrospective cross-sectional study, 4508 cases from the U.K. Biobank were split randomly into 3244 training cases, 812 validation cases, and 452 test cases. Ground truth myocardial landmarks were defined and tracked by manual initialization and correction of deformable image registration using previously validated software with five readers. The fully automatic framework consisted of (a) a convolutional neural network (CNN) for localization and (b) a combination of a recurrent neural network (RNN) and a CNN to detect and track the myocardial landmarks through the image sequence for each slice. Radial and circumferential strain were then calculated from the motion of the landmarks and averaged on a slice basis.

RESULTS

Within the test set, myocardial end-systolic circumferential Green strain errors were -0.001 ± 0.025, -0.001 ± 0.021, and 0.004 ± 0.035 in the basal, mid-, and apical slices, respectively (mean ± standard deviation of differences between predicted and manual strain). The framework reproduced significant reductions in circumferential strain in participants with diabetes, hypertensive participants, and participants with a previous heart attack. Typical processing time was approximately 260 frames (approximately 13 slices) per second on a GPU with 12 GB RAM compared with 6-8 minutes per slice for the manual analysis.

CONCLUSION

The fully automated combined RNN and CNN framework for analysis of myocardial strain enabled unbiased strain evaluation in a high-throughput workflow, with similar ability to distinguish impairment due to diabetes, hypertension, and previous heart attack.Published under a CC BY 4.0 license. Supplemental material is available for this article.

Right and left ventricular interactions, strain, and remodeling in repaired pulmonary stenosis patients with preserved right ventricular ejection fraction: A cardiac magnetic resonance study

BACKGROUND

Right ventricular dilation and dysfunction is a common long-term complication in patients with repaired pulmonary stenosis (rPS). Additionally, abnormal right and left ventricular interactions have been reported in right-sided heart defect after intervention, including in pulmonary stenosis.

PURPOSE

To analyze ventricular strain, remodeling, and left and right ventricular interactions in rPS patients with preserved right ventricular ejection fraction (RVEF) compared with healthy children using cardiac magnetic resonance.

STUDY TYPE

A cross-sectional study.

POPULATION

In all, 34 rPS patients and 10 healthy children volunteers (controls).

FIELD STRENGTH/SEQUENCE

3.0T/2D balanced steady-state free precession (2D b-SSFP) cine, late gadolinium enhancement (LGE), and 2D phase contrast (2D-PC).

ASSESSMENT

Pulmonary regurgitation (PR) fractions of the main pulmonary artery, biventricular volumes, masses, function, and cardiac strain.

STATISTICAL TESTS

Mann-Whitney U-test, t-test, Pearson correlation coefficients, Spearman's correlation coefficients, and intraclass correlation coefficients analysis were performed.

RESULTS

For group analysis, the right ventricular (RV) global circumferential strain and radial strain were significantly increased in patients when compared with controls (-13.57 ± 2.69 vs. -5.91 ± 3.16, P < 0.001; 25.31 ± 8.12 vs. 9.87 ± 5.32, P < 0.001, respectively). The fraction of PR displayed moderate correlation with right ventricular end-diastolic volume index (RVEDVi) (r = 0.452, P = 0.022). RVEDVi and mass index were larger in patients vs. control (104.92 ± 27.46 vs. 85.15 ± 11.98, P = 0.016; 18.28 ± 4.95g/m² vs. 11.67 ± 2.14 g/m² , P < 0.001, respectively). Patients presented with preserved left ventricular ejection function, but was lower than healthy controls (60.89% ± 4.89% vs. 65.95% ± 4.56%, P = 0.006). Regional circumferential strain of segment 3 of left ventricle (LV) were significantly decreased in patients (-7.79 ± 6.52 vs. -13.56 ± 3.22, P = 0.003).

DATA CONCLUSION

Compensated increased RV strain, myocardial remodeling of RV, and adverse right and left ventricular interactions occur in rPS patients with preserved RVEF. The decreased interventricular septum strain may lead to impaired LV function due to RV dilation as a result of PR.

LEVEL OF EVIDENCE

3 Technical Efficacy Stage: 3 J. Magn. Reson. Imaging 2020;52:129-138.

Triple-marker cardiac MRI detects sequential tissue changes of healing myocardium after a hydrogel-based therapy

Regenerative therapies based on injectable biomaterials, hold an unparalleled potential for treating myocardial ischemia. Yet, noninvasive evaluation of their efficacy has been lagging behind. Here, we report the development and longitudinal application of multiparametric cardiac magnetic resonance imaging (MRI) to evaluate a hydrogel-based cardiac regenerative therapy. A pH-switchable hydrogel was loaded with slow releasing insulin growth factor 1 and vascular endothelial growth factor, followed by intramyocardial injection in a mouse model of ischemia reperfusion injury. Longitudinal cardiac MRI assessed three hallmarks of cardiac regeneration: angiogenesis, resolution of fibrosis and (re)muscularization after infarction. The multiparametric approach contained dynamic contrast enhanced MRI that measured improved vessel features by assessing fractional blood volume and permeability*surface area product, T1-mapping that displayed reduced fibrosis, and tagging MRI that showed improved regional myocardial strain in hydrogel treated infarcts. Finally, standard volumetric MRI demonstrated improved left ventricular functioning in hydrogel treated mice followed over time. Histology confirmed MR-based vessel features and fibrotic measurements. Our novel triple-marker strategy enabled detection of ameliorated regeneration in hydrogel treated hearts highlighting the translational potential of these longitudinal MRI approaches.

Fully automated and comprehensive MRI-based left-ventricular contractility analysis in post-chemotherapy breast cancer patients

OBJECTIVE

This study investigated the occurrence of cardiotoxicity-related left-ventricular (LV) contractile dysfunction in breast cancer patients following treatment with antineoplastic chemotherapy agents.

METHODS

A validated and automated MRI-based LV contractility analysis tool consisting of quantization-based boundary detection, unwrapping of image phases and the meshfree Radial Point Interpolation Method was used toward measuring LV chamber quantifications (LVCQ), three-dimensional strains and torsions in patients and healthy subjects. Data were acquired with the Displacement Encoding with Stimulated Echoes (DENSE) sequence on 21 female patients and 21 age-matched healthy females. Estimates of patient LVCQs from DENSE acquisitions were validated in comparison to similar steady-state free precession measurements and their strain results validated via Bland-Altman interobserver agreements. The occurrence of LV abnormalities was investigated via significant differences in contractility measurements (LVCQs, strains and torsions) between patients and healthy subjects.

RESULTS

Repeated measures analysis showed similarities between LVCQ measurements from DENSE and steady-state free precession, including cardiac output (4.7 ± 0.4 L, 4.6 ± 0.4 L, p = 0.8), and LV ejection fractions (59±6%, 58±5%, p = 0.2). Differences found between patients and healthy subjects included enlarged basal diameter (5.0 ± 0.5 cm vs 4.4 ± 0.5 cm, p < 0.01), apical torsion (6.0 ± 1.1° vs 9.7 ± 1.4°, p < 0.001) and global longitudinal strain (-0.15 ± 0.02 vs. -0.21 ± 0.04, p < 0.001), but not LV ejection fraction (59±6% vs. 63±6%, p = 0.1).

CONCLUSION

The results from the statistical analysis reveal the possibility of LV abnormalities in the post-chemotherapy patients via enlarged basal diameter and reduced longitudinal strain and torsion, in comparison to healthy subjects.

ADVANCES IN KNOWLEDGE

This study shows that subclinical LV abnormalities in post-chemotherapy breast cancer patients can be detected with an automated technique for the comprehensive analysis of contractile parameters.

Regional dynamics of fractal dimension of the left ventricular endocardium from cine computed tomography images

We present a method to leverage the high fidelity of computed tomography (CT) to quantify regional left ventricular function using topography variation of the endocardium as a surrogate measure of strain. 4DCT images of 10 normal and 10 abnormal subjects, acquired with standard clinical protocols, are used. The topography of the endocardium is characterized by its regional values of fractal dimension (F D ), computed using a box-counting algorithm developed in-house. The averageF D in each of the 16 American Heart Association segments is calculated for each subject as a function of time over the cardiac cycle. The normal subjects show a peak systolic percentage change inF D of 5.9 % ± 2 % in all free-wall segments, whereas the abnormal cohort experiences a change of 2 % ± 1.2 % ( p < 0.00001 ). Septal segments, being smooth, do not undergo large changes inF D . Additionally, a principal component analysis is performed on the temporal profiles ofF D to highlight the possibility for unsupervised classification of normal and abnormal function. The method developed is free from manual contouring and does not require any feature tracking or registration algorithms. TheF D values in the free-wall segments correlated well with radial strain and with endocardial regional shortening measurements.

Anthropomorphic left ventricular mesh phantom: a framework to investigate the accuracy of SQUEEZ using Coherent Point Drift for the detection of regional wall motion abnormalities

We present an anthropomorphically accurate left ventricular (LV) phantom derived from human computed tomography (CT) data to serve as the ground truth for the optimization and the spatial resolution quantification of a CT-derived regional strain metric (SQUEEZ) for the detection of regional wall motion abnormalities. Displacements were applied to the mesh points of a clinically derived end-diastolic LV mesh to create analytical end-systolic poses with physiologically accurate endocardial strains. Normal function and regional dysfunction of four sizes [1, 2/3, 1/2, and 1/3 American Heart Association (AHA) segments as core diameter], each exhibiting hypokinesia (70% reduction in strain) and subtle hypokinesia (40% reduction in strain), were simulated. Regional shortening (RS CT ) estimates were obtained by registering the end-diastolic mesh to each simulated end-systolic mesh condition using a nonrigid registration algorithm. Ground-truth models of normal function and of hypokinesia were used to identify the optimal parameters in the registration algorithm and to measure the accuracy of detecting regional dysfunction of varying sizes and severities. For normal LV function,RS CT values in all 16 AHA segments were accurate to within ± 5 % . For cases with regional dysfunction, the errors inRS CT around the dysfunctional region increased with decreasing size of dysfunctional tissue.

Magnetic resonance imaging of the papillary muscles of the left ventricle: normal anatomy, variants, and abnormalities

Left ventricular papillary muscles are small myocardial structures that play an important role in the functioning of mitral valve and left ventricle. Typically, there are two groups of papillary muscles, namely the anterolateral and the posteromedial groups. Cardiovascular magnetic resonance (CMR) is a valuable imaging modality in the evaluation of papillary muscles, providing both morphological and functional information. There is a remarkably wide variation in the morphology of papillary muscles. These variations can be asymptomatic or associated with symptoms related to LV outflow tract obstruction, often associated with hypertrophic cardiomyopathy. Abnormalities of the papillary muscles range from congenital disorders to neoplasms. Parachute mitral valve is the most common congenital abnormality of papillary muscles, in which all the chordae insert into a single papillary muscle. Papillary muscles can become dysfunctional, most commonly due to ischemia. Papillary muscle rupture is a major complication of acute myocardial infarction that results in mitral regurgitation and associated with high mortality rates. The most common papillary neoplasm is metastasis, but primary benign and malignant neoplasms can also be seen. In this article, we discuss the role of CMR in the evaluation of papillary muscle anatomy, function, and abnormalities.

The prognostic value of biventricular long axis strain using standard cardiovascular magnetic resonance imaging in patients with hypertrophic cardiomyopathy

BACKGROUND

Long axis strain (LAS) is a parameter derived from standard cardiovascular magnetic resonance imaging. However, the prognostic value of biventricular LAS in hypertrophic cardiomyopathy (HCM) is unknown.

METHODS

Patients with HCM (n = 384) and healthy volunteers (n = 150) were included in the study. Left ventricular (LV)-LAS was defined as the percentage change in the length measured from the epicardial border of the LV apex to the midpoint of a line connecting the mitral annulus at end-systole and end-diastole. Right ventricular (RV)-LAS represented the percentage change of length between epicardial border of the LV apex to the midpoint of a line connecting the tricuspid annulus at end-systole and end-diastole. The primary endpoint was a combination of all-cause death and sudden cardiac death aborted by appropriate implantable cardioverter-defibrillator discharge and cardiopulmonary resuscitation after syncope. The secondary endpoint was a combination of the primary endpoint and hospitalization for congestive heart failure.

RESULTS

Twenty-nine patients (7.6%) achieved the primary endpoint, and the secondary endpoint occurred in 66 (17.2%) patients. In multivariate Cox regression analysis, RV-LAS was an independent prognostic factor for the primary (hazard ratio (HR), 1.13) and secondary (HR, 1.11) endpoints. In the subgroup of patients with a normal RV ejection fraction (EF) (>45.0%, n = 345), impaired RV-LAS was associated with adverse outcomes and might add incremental prognostic value to RVEF and tricuspid annular plane systolic excursion (TAPSE) (p < 0.01).

CONCLUSIONS

RV-LAS is an independent predictor of adverse prognosis in HCM in addition to RVEF and TAPSE.