Myocardial tissue tagging with cardiovascular magnetic resonance

Myocardial Strain Imaging: Theory, Current Practice, and the Future

Myocardial strain imaging by echocardiography or cardiac magnetic resonance (CMR) is a powerful method to diagnose cardiac disease. Strain imaging provides measures of myocardial shortening, thickening, and lengthening and can be applied to any cardiac chamber. Left ventricular (LV) global longitudinal strain by speckle-tracking echocardiography is the most widely used clinical strain parameter. Several CMR-based modalities are available and are ready to be implemented clinically. Clinical applications of strain include global longitudinal strain as a more sensitive method than ejection fraction for diagnosing mild systolic dysfunction. This applies to patients suspected of having heart failure with normal LV ejection fraction, to early systolic dysfunction in valvular disease, and when monitoring myocardial function during cancer chemotherapy. Segmental LV strain maps provide diagnostic clues in specific cardiomyopathies, when evaluating LV dyssynchrony and ischemic dysfunction. Strain imaging is a promising modality to quantify right ventricular function. Left atrial strain may be used to evaluate LV diastolic function and filling pressure.

Cardiac MRI in heart failure with preserved ejection fraction

Patients who have heart failure with preserved ejection fraction (HFpEF) have signs and symptoms of heart failure, yet their ejection fraction remains greater than or equal to 50 percent. Understanding the underlying cause of HFpEF is crucial for accurate diagnosis and effective treatment. This condition can be caused by multiple factors, including ischemic or nonischemic myocardial diseases. HFpEF is often associated with diastolic dysfunction. Cardiac magnetic resonance (CMR) allows for a precise examination of the functional and structural alterations associated with HFpEF through the measurement of volumes and mass, the assessment of systolic and diastolic function, and the analysis of tissue characteristics. We will discuss CMR imaging indicators that are specific to patients with HFpEF and their relation to the disease. These markers can be acquired through both established and emerging methods.

Identification of Circulating Plasma Proteins as a Mediator of Hypertension-Driven Cardiac Remodeling: A Mediation Mendelian Randomization Study

BACKGROUND

This study focused on circulating plasma protein profiles to identify mediators of hypertension-driven myocardial remodeling and heart failure.

METHODS

A Mendelian randomization design was used to investigate the causal impact of systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse pressure on 82 cardiac magnetic resonance traits and heart failure risk. Mediation analyses were also conducted to identify potential plasma proteins mediating these effects.

RESULTS

Genetically proxied higher SBP, DBP, and pulse pressure were causally associated with increased left ventricular myocardial mass and alterations in global myocardial wall thickness at end diastole. Elevated SBP and DBP were linked to increased regional myocardial radial strain of the left ventricle (basal anterior, mid, and apical walls), while higher SBP was associated with reduced circumferential strain in specific left ventricular segments (apical, mid-anteroseptal, mid-inferoseptal, and mid-inferolateral walls). Specific plasma proteins mediated the impact of blood pressure on cardiac remodeling, with FGF5 (fibroblast growth factor 5) contributing 2.96% (P=0.024) and 4.15% (P=0.046) to the total effect of SBP and DBP on myocardial wall thickness at end diastole in the apical anterior segment and leptin explaining 15.21% (P=0.042) and 23.24% (P=0.022) of the total effect of SBP and DBP on radial strain in the mid-anteroseptal segment. Additionally, FGF5 was the only mediator, explaining 4.19% (P=0.013) and 4.54% (P=0.032) of the total effect of SBP and DBP on heart failure susceptibility.

CONCLUSIONS

This mediation Mendelian randomization study provides evidence supporting specific circulating plasma proteins as mediators of hypertension-driven cardiac remodeling and heart failure.

Impact of pulmonary stenosis on right ventricular global longitudinal strain in repaired tetralogy of Fallot patients post transcatheter pulmonary valve replacement

BACKGROUND

Mixed pulmonary disease with pulmonary regurgitation (PR) and stenosis (PS) in repaired tetralogy of Fallot (rTOF) can negatively impact ventricular health. Myocardial strain has been shown to be more sensitive at detecting occult ventricular dysfunction compared to right ventricular ejection fraction (RV EF). We hypothesize that rTOF patients with predominant PS will have lower RV global longitudinal strain (RV GLS) prior to and post-transcatheter pulmonary valve replacement (TPVR).

METHODS

A retrospective cohort of rTOF patients who underwent cardiac magnetic resonance (CMR) and cardiac catheterization for right ventricular pressure (RVSP) measurement were analyzed at three time points: before valve implantation, at discharge and within 18 months post-TPVR. Patients were dichotomized into three groups based on RVSP: 0%-49%, 50%-74%, and >75%. RV GLS and left ventricular (LV) GLS by speckle tracking echocardiography (STE) were obtained from the apical 4-chamber using TomTec software (TOMTEC IS, Germany).

RESULTS

Forty-eight patients were included. Every 14.3% increase in preimplantation RVSP above 28% was associated with an absolute magnitude 1% lower RV GLS (p = .001). Preimplantation RVSP when 75% or higher had 3.36% worse RV GLS than the lowest bin (p = .014). Overall, average RV strain magnitude was higher when preimplantation RVSP was less than 50% and had greater improvement over the three time points. Higher post implantation RVSP correlated with lower strain magnitude.

CONCLUSION

Patients with significant PS (>50%) may benefit from earlier PVR and not depend solely on RV size and EF. Myocardial strain may be a more sensitive marker of function; however, larger, prospective studies are needed.

Impact of temporal and spatial resolution on atrial feature tracking cardiovascular magnetic resonance imaging

BACKGROUND

Myocardial deformation assessment by cardiovascular magnetic resonance-feature tracking (CMR-FT) has incremental prognostic value over volumetric analyses. Recently, atrial functional analyses have come to the fore. However, to date recommendations for optimal resolution parameters for accurate atrial functional analyses are still lacking.

METHODS

CMR-FT was performed in 12 healthy volunteers and 9 ischemic heart failure (HF) patients. Cine sequences were acquired using different temporal (20, 30, 40 and 50 frames/cardiac cycle) and spatial resolution parameters (high 1.5 × 1.5 mm in plane and 5 mm slice thickness, standard 1.8 × 1.8 × 8 mm and low 3.0 × 3.0 × 10 mm). Inter- and intra-observer reproducibility were calculated.

RESULTS

Increasing temporal resolution is associated with higher absolute strain and strain rate (SR) values. Significant changes in strain assessment for left atrial (LA) total strain occurred between 20 and 30 frames/cycle amounting to 2,5-4,4% in absolute changes depending on spatial resolution settings. From 30 frames/cycle onward, absolute strain values remained unchanged. Significant changes of LA strain rate assessment were observed up to the highest temporal resolution of 50 frames/cycle. Effects of spatial resolution on strain assessment were smaller. For LA total strain a general trend emerged for a mild decrease in strain values obtained comparing the lowest to the highest spatial resolution at temporal resolutions of 20, 40 and 50 frames/cycle (p = 0.006-0.046) but not at 30 frames/cycle (p = 0.140).

CONCLUSION

Temporal and to a smaller extent spatial resolution affect atrial functional assessment. Consistent strain assessment requires a standard spatial resolution and a temporal resolution of 30 frames/cycle, whilst SR assessment requires even higher settings of at least 50 frames/cycle.

Progress in Cardiac Magnetic Resonance Feature Tracking for Evaluating Myocardial Strain in Type-2 Diabetes Mellitus

The global prevalence of type-2 diabetes mellitus (T2DM) has caused harm to human health and economies. Cardiovascular disease is one main cause of T2DM mortality. Increased prevalence of diabetes and associated heart failure (HF) is common in older populations, so accurately evaluating heart-related injury and T2DM risk factors and conducting early intervention are important. Quantitative cardiovascular system imaging assessments, including functional imaging during cardiovascular disease treatment, are also important. The left-ventricular ejection fraction (LVEF) has been traditionally used to monitor cardiac function; it is often preserved or increased in early T2DM, but subclinical heart deformation and dysfunction can occur. Myocardial strains are sensitive to global and regional heart dysfunction in subclinical T2DM. Cardiac magnetic resonance feature-tracking technology (CMR-FT) can visualize and quantify strain and identify subclinical myocardial injury for early management, especially with preserved LVEF. Meanwhile, CMR-FT can be used to evaluate the multiple cardiac chambers involvement mediated by T2DM and the coexistence of complications. This review discusses CMR-FT principles, clinical applications, and research progress in the evaluation of myocardial strain in T2DM.

Computational Analysis of Cardiac Contractile Function

PURPOSE OF REVIEW

Heart failure results in the high incidence and mortality all over the world. Mechanical properties of myocardium are critical determinants of cardiac function, with regional variations in myocardial contractility demonstrated within infarcted ventricles. Quantitative assessment of cardiac contractile function is therefore critical to identify myocardial infarction for the early diagnosis and therapeutic intervention.

RECENT FINDINGS

Current advancement of cardiac functional assessments is in pace with the development of imaging techniques. The methods tailored to advanced imaging have been widely used in cardiac magnetic resonance, echocardiography, and optical microscopy. In this review, we introduce fundamental concepts and applications of representative methods for each imaging modality used in both fundamental research and clinical investigations. All these methods have been designed or developed to quantify time-dependent 2-dimensional (2D) or 3D cardiac mechanics, holding great potential to unravel global or regional myocardial deformation and contractile function from end-systole to end-diastole. Computational methods to assess cardiac contractile function provide a quantitative insight into the analysis of myocardial mechanics during cardiac development, injury, and remodeling.

Detection of early signs of right ventricular systolic impairment in unoperated Ebstein's anomaly by cardiac magnetic resonance feature tracking

BACKGROUND

Cardiovascular magnetic resonance feature-tracking analysis (CMR-FT) provides a quantitative assessment of myocardial contraction with potential for diagnostic and prognostic ability in a wide spectrum of diseases. Ebstein's anomaly (EA) is a rare congenital heart disease characterized by apical displacement of the tricuspid valve. However, it is also considered a disorder of development affecting the global right ventricular myocardium. Aim of our study is to describe the complex contractile mechanics of the functional right ventricle (RV) in patients affected by EA through CMR-FT.

METHODS

Fifty surgery-free EA patients who had undergone a complete CMR protocol at our institution between January 2017 and December 2020 were selected for the retrospective study. A historical control group of twenty-five healthy subjects was also included. CMR-FT analysis was performed at a dedicated workstation by manually tracing RV endo- end epicardial borders on steady-state-free-precession (SSFP) cine images. Strain values were calculated. Apical displacement of the tricuspid valve (TV) was measured on a 4-chamber cine image from the right atrio-ventricular junction to the functional annulus of the TV.

RESULTS

EA patients presented significantly impaired RV global radial strain (GRS) and global circumferential strain (GCS) compared to controls (P<0.0001 and P=0.0008, respectively). In a subgroup analysis, GRS was significantly compromised in patients with a severely displaced TV (>16 mm/m²) compared to milder forms (P=0.03) and to controls (P<0.0001). Among EA patients with a preserved ejection fraction, 12 (48%) vs. 6 (24%) controls had reduced both GRS and GCS.

CONCLUSIONS

The contractile pattern of the functional RV in EA is characterised by prevalent alterations in the short-axis direction as indicated by reduced GRS and GCS. Strain values might be reduced prior to routine used functional parameters like RV ejection fraction (RVEF) and can possibly serve as an early predictor of myocardial dysfunction in EA patients.

Regional Strain Score as Prognostic Marker of Cardiovascular Events From the Multi-Ethnic Study of Atherosclerosis (MESA)

Background

Left ventricular (LV) circumferential strain (Ecc) is an accurate indicator of regional myocardial function, particularly using the regional Ecc or layer-specific strain.

Aim

This study aimed to investigate the prognostic value of a regional strain score (RSS) for predicting the incident of heart failure (HF) and coronary heart disease (CHD) in a population without a history of cardiovascular disease at baseline.

Materials and Methods

Data from participants in the Multi-Ethnic Study of Atherosclerosis (MESA) who underwent tagged magnetic resonance imaging for strain determination were analyzed. Using −17% and −10% as Ecc cut-offs, each segment was rated from 0 to 2 points according to the Ecc value of each layer. The endo-Ecc, mid-Ecc, and epi-Ecc values from the 16-segment model were used to calculate three RSS: Endo-, Mid-, and Epi-RSS, respectively, which were defined as a percentage of good LV regional function. The Intramyocardial-RSS was the sum of these three RSS. Cox proportional hazard models were used to evaluate the association between each RSS and incident HF and hard CHD.

Results

Among the 1,506 participants (63.3 ± 9.4 years, 54.6% men), 122 cases of hard CHD and 91 cases of HF were observed [median (IQR) follow-up 15.9 (12.9–16.6) years]. After adjustment, Mid-, Epi-, and Intramyocardial-RSS values <50% were independently associated with HF [adjusted HR 1.43; 95% CI (1.08–2.87), p = 0.004; HR 1.80; 95% CI (1.12–3.07), p < 0.001; and HR 2.01; 95% CI (1.19–3.20), p < 0.001]. After adjustment, Endo-, Mid-, Epi-, and Intramyocardial-RSS <50% were also independently associated with hard CHD [adjusted HR 1.31; 95% CI (1.03–1.51), p = 0.04; HR 1.79; 95% CI (1.26–2.57), p < 0.001; HR 2.03; 95% CI (1.45–3.40), p < 0.001; and HR 2.28; 95% CI (1.51–3.53), p < 0.001].

Conclusions

Layer-specific regional Ecc, assessed by RSS, provides a robust, independent predictive value for incident HF and hard CHD in asymptomatic participants without any history of previous clinical cardiovascular disease.

Clinical Trial Registration

Unique identifier: NCT00005487.

Left Ventricular Strain Measurements Derived from MR Feature Tracking: A Head-to-Head Comparison of a Higher Temporal Resolution Method With a Conventional Method

BACKGROUND

Magnetic resonance feature tracking (MR-FT) is an imaging technique that quantifies both global and regional myocardial strain. Currently, conventional MR-FT provides a superior signal and contrast-to-noise ratio but has a relatively low temporal resolution. A higher temporal resolution MR-FT technique may provide improved results.

PURPOSE

To explore the impact of higher temporal resolution on left ventricular (LV) myocardial strain measurements using MR-FT.

STUDY TYPE

Prospective.

POPULATION

One hundred and fifty-three participants including five healthy subjects and patients with various cardiac diseases referred to MR for cardiac assessment.

FIELD STRENGTH

3 T, balanced steady-state free precession sequence with and without compressed sensing (temporal resolution: 10 msec and 40 msec, respectively).

ASSESSMENT

Conventional (40 msec) and higher (10 msec) temporal resolution data were acquired in all subjects during the same scanning session. Global circumferential strain (GCS), global longitudinal strain (GLS), and global radial strain (GRS) as well as peak systolic and diastolic strain rates (SRs) were measured by MR-FT and compared between the two temporal resolutions. We also performed subgroup analyses according to heart rates (HRs) and LV ejection fraction (LVEF).

STATISTICAL TESTS

Paired t-test, Wilcoxon signed-rank test, linear regression analyses, Bland-Altman plots. A P value <0.05 was considered to be statistically significant.

RESULTS

GCS and GRS were significantly higher in the 10-msec temporal resolution studies compared to the 40-msec temporal resolution studies (GCS: -13.00 ± 6.58% vs. -12.51 ± 5.76%; GRS: 21.97 ± 14.54% vs. 20.62 ± 12.52%). In the subgroup analyses, significantly higher GLS, GCS, and GRS values were obtained in subjects with LVEF ≥50%, and significantly higher GCS and GRS values were obtained in subjects with HRs <70 bpm when assessed with the 10-msec vs. the 40-msec temporal resolutions. All the peak systolic and diastolic SRs were significantly higher in the higher temporal resolution acquisitions. This was also true for all subgroups.

DATA CONCLUSIONS

Higher temporal resolution resulted in significantly higher cardiac strain and SR values using MR-FT and could be beneficial, particularly in patients with LVEF ≥50% and HR <70 bpm.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 1.

Ultra-high sensitivity cardiac troponin-I concentration and left ventricular structure and function in women with ischemia and no obstructive coronary artery disease

Aims

Women are disproportionally impacted by ischemia and no obstructive coronary artery disease (INOCA), and such women are at increased risk of developing heart failure with preserved ejection fraction (HFpEF), however the mechanisms linking these conditions remain poorly understood. The aim of this study was to determine whether ultra-high sensitivity cardiac troponin I (u-hscTnI), an indicator of cardiomyocyte injury, is associated with abnormalities in myocardial perfusion and left ventricular (LV) structure and function in women with INOCA.

Methods

327 women with INOCA enrolled in the Women's Ischemia Syndrome Evaluation-Coronary Vascular Dysfunction (WISE-CVD) study underwent vasodilator stress cardiac magnetic resonance imaging (CMRI) and u-hscTnI measurements (Simoa HD-1 Analyzer, Quanterix Corporation). Multivariable linear regression was used to evaluate associations between u-hscTnI concentrations and myocardial perfusion (MPRI), LV mass index and feature-tracking derived strain measures of LV function.

Results

u-hscTnI concentrations were quantifiable in 100% of the cohort and ranged from 0.004 to 79.6 pg/mL. In adjusted models, u-hscTnI was associated with LV mass index (+2.03; 95% CI 1.17, 2.89; p < 0.01) and early diastolic radial strain rate (SR) (+0.13; 95% CI 0.01, 0.25; p = 0.03), early diastolic circumferential SR (-0.04; 95% CI -0.08, 0.002; p = 0.06) and early diastolic longitudinal SR (-0.03; 95% CI -0.07, 0.002; p = 0.06). u-hscTnI was not associated with MPRI (p = 0.39) in adjusted models.

Conclusion

Together, these findings support cardiomyocyte injury as a putative pathway towards adverse LV remodeling and dysfunction; however, further research is needed to define the specific mechanism(s) driving myocellular injury in INOCA.

In-silico study of accuracy and precision of left-ventricular strain quantification from 3D tagged MRI

Cardiac Magnetic Resonance Imaging (MRI) allows quantifying myocardial tissue deformation and strain based on the tagging principle. In this work, we investigate accuracy and precision of strain quantification from synthetic 3D tagged MRI using equilibrated warping. To this end, synthetic biomechanical left-ventricular tagged MRI data with varying tag distance, spatial resolution and signal-to-noise ratio (SNR) were generated and processed to quantify errors in radial, circumferential and longitudinal strains relative to ground truth. Results reveal that radial strain is more sensitive to image resolution and noise than the other strain components. The study also shows robustness of quantifying circumferential and longitudinal strain in the presence of geometrical inconsistencies of 3D tagged data. In conclusion, our study points to the need for higher-resolution 3D tagged MRI than currently available in practice in order to achieve sufficient accuracy of radial strain quantification.

Quantification of Myocardial Deformation in Patients with Takayasu Arteritis by Cardiovascular Magnetic Resonance Feature Tracking Imaging

BACKGROUND

Cardiac involvement is one of the main causes of morbidity and mortality in patients with Takayasu arteritis (TA). Early detection and intervention of cardiac damage may be helpful to reduce the mortality of TA. Magnetic resonance (MR) imaging (MRI)-derived feature tracking (FT) is an effective quantitative method to assess myocardial deformation which may reflect early changes of cardiac function.

PURPOSE

To explore the utility of MR-FT as a method to detect cardiac damage in TA patients.

STUDY TYPE

Retrospective.

POPULATION

Fifty-seven TA patients who had undergone clinically indicated MRI and 57 healthy controls.

FIELD STRENGTH/SEQUENCES

Balanced steady-state free precession rest cine and 2D phase-sensitive inversion recovery breath-hold segmented gradient echo late gadolinium enhancement (LGE) sequences at 3.0 T.

ASSESSMENT

Based on LGE images, TA patients were divided into two subgroups, LGE (+) subgroup (N = 12) and LGE (-) subgroup (N = 45). In addition, patients were further subdivided into impaired (N = 26) and preserved left ventricle ejection fraction (LVEF) subgroups (N = 31). FT-derived deformation indices, including left ventricular (LV) global longitudinal strain (GLS), were measured by commercial software.

STATISTICAL TESTS

Mann-Whitney U-test, Kruskal-Wallis test followed by Dunn-Bonferroni post hoc method, and receiver operating characteristic curve analysis were conducted. A P-value of <0.05 was considered statistically significant.

RESULTS

GLS was significantly worse in TA than in controls (median [interquartile range, IQR]: TA -10.0 [-7.5 to 12.4] vs. controls -12.7 [-11.8 to 14.7]). Moreover, TA patients with LGE (+) had significantly poorer GLS than those with LGE (-) (median [IQR]: LGE (+) -6.8 [-4.0 to 8.1] vs. LGE (-) -10.7 [-8.5 to 12.9]). The reduced LVEF subgroup had significantly greater cardiac dysfunction as measured by MR-FT than the preserved LVEF subgroup (GLS median [IQR]: reduced LVEF -7.9 [-6.2 to 11.4] vs. preserved LVEF -10.8 [-8.6 to 13.5]).

DATA CONCLUSION

Myocardial deformation impairment was found in the majority of TA patients. MR-FT imaging may be helpful in the early diagnosis and management of TA patients.

LEVEL OF EVIDENCE

4 TECHNICAL EFFICACY STAGE: 5.

Quantitative Assessment of Left and Right Atrial Strains Using Cardiovascular Magnetic Resonance Based Tissue Tracking

Background: Left and right atrium (LA and RA) exert an essential and dynamic role in ventricular filling and hence affect heart performance. Strain quantification has been reported as a novel parameter to assess function. However, the assessment of bi-atrial strains with cardiovascular magnetic resonance (CMR) based techniques is still limited and gender- and age-specific normal values in a healthy population are missing.

Methods: One hundred and fifty healthy volunteers (49.8 ± 17.3 years, 75 males) undergoing 1.5 Tesla CMR examination were retrospectively and consecutively recruited. LA and RA free wall (RAFW) radial and longitudinal strains (RS and LS) associated with atrial reservoir, conduit and booster pump functions were evaluated with CMR based tissue tracking (CMR-TT) technique.

Results: The reservoir, conduit and pump LS resulted as 30.7 ± 10.2%, 19.5 ± 8.2%, 10.9 ± 3.7% for LA, and 52.2 ± 17.6%, 33.3 ± 14.2%, 19.1 ± 8.5% for RAFW, respectively. The amplitude of RA strains was significantly larger than that of LA strains, except for conduit RS. With the increase of age, the decrement of majority of reservoir and conduit strains were observed, while pump strains remained unaffected. Females presented with significantly larger RAFW strains compared with males, especially in the elderly. In addition to the positive correlation between atrial strains and emptying fraction, the negative correlation between atrial strains and volume index was also confirmed. Intra-observer reproducibility of LA strains was superior to RAFW strains (coefficient of variation: 10.12–17.04% vs. 10.80–27.36%, respectively), and the measurement of reservoir and conduit strains was more reproducible in comparison with pump strain.

Conclusion: CMR-TT is a feasible and reproducible technique to quantify LA and RA strains and determine atrial phasic functions. The existence of age- and gender-related difference of strains suggests the necessity to establish specific normal values for individual populations.

Left Ventricular Remodeling Following Balloon Mitral Valvuloplasty in Rheumatic Mitral Stenosis: Magnetic Resonance Imaging Study

Background: Rheumatic heart disease affects primarily cardiac valves, it could involve the myocardium either primarily or secondary to heart valve affection. The influence of balloon mitral valvuloplasty (BMV) on left ventricular function has not been sufficiently studied. Aim: To determine the influence of balloon mitral valvuloplasty (BMV) on both global and regional left ventricular (LV) function. Methods: Thirty patients with isolated rheumatic mitral stenosis (MS) were studied. All patients had cardiac magnetic resonance imaging (CMR) before, 6 months and 1 year after successful BMV. LV volumes, ejection fraction (EF), regional and global LV deformation, and LV late gadolinium enhancement were evaluated. Results: At baseline, patients had median EF of 57 (range: 45-69) %, LVEDVI of 74 (44-111) ml/m2 and LVESVI of 31 (14-57) ml/m2 with absence of late gadolinium enhancement in all myocardial segments. Six months following BMV, there was a significant increase in LV peak systolic global longitudinal strain (GLS) (-16.4 vs. -13.8, p < 0.001) and global circumferential strain (GCS) (-17.8 vs. -15.6, p = 0.002). At 1 year, there was a trend towards decrease in LVESVI (29 ml/m2, p = 0.079) with a significant increase in LV EF (62%, p < 0.001). A further significant increase, compared to 6 months follow up studies, was noticed in GLS (-17.9 vs. -16.4, p = 0.008) and GCS (-19.4 vs. -17.8 p = 0.03). Conclusions: Successful BMV is associated with improvement in global and regional LV systolic strain which continues for up to 1 year after the procedure.

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.

Cardiac Magnetic Resonance Feature Tracking in Aortic Stenosis: Exploration of Strain Parameters and Prognostic Value in Asymptomatic Patients with Preserved Ejection Fraction

Objective

To determine the most valuable cardiac magnetic resonance feature tracking (CMR-FT) parameters for evaluating aortic stenosis (AS) and determine whether they can predict the prognosis in asymptomatic AS patients with preserved ejection fraction (pEF).

Materials and Methods

A prospective cohort of 123 moderate to severe AS patients (60 males, 68.6 ± 9.2 years) and 32 control subjects (14 males, 67.9 ± 4.4 years) underwent echocardiography and 3T CMR imaging from 2011–2015. CMR cine images were analyzed using CMR-FT to assess the left ventricular radial, circumferential, and longitudinal peak strain (PS) in 2- and 3-dimensions. The primary endpoints were clinical cardiac events (CCEs), including cardiac death, heart failure, and AS-associated symptom development. For statistical analysis, logistic regression and log-rank tests were used.

Results

Global PSs differed between AS patients and controls and between severe and moderate AS patients (p < 0.05). Two-dimensional (2D) global radial and longitudinal PSs changed gradually with the severity of AS groups (p < 0.001). Twenty-two of 67 asymptomatic AS patients with pEF experienced CCEs during the follow-up (median: 31.1 months). 2D global longitudinal PS (GLPS) was the single risk factor for CCE (p = 0.017). The relative risk for CCE was 3.9 (p = 0.016, 95% confidence interval: 1.2–11.9) based on 2D GLPS with a cutoff of −17.9% according to receiver operating characteristic curve analysis. Survival analysis demonstrated that asymptomatic AS patients with pEF having impaired 2D GLPS experienced worse event-free survival than the others (p = 0.041).

Conclusion

2D global longitudinal and radial PSs may reflect cardiac dysfunction according to the degree of AS. 2D GLPS might be a prognostic predictor of CCEs in asymptomatic AS patients with pEF.

Head-to-head comparison of cardiovascular MR feature tracking cine versus acquisition-based deformation strain imaging using myocardial tagging and strain encoding

PURPOSE

Myocardial feature-tracking (FT) deformation imaging is superior for risk stratification compared with volumetric approaches. Because there is no clear recommendation regarding FT postprocessing, we compared different FT-strain analyses with reference standard techniques, including tagging and strain-encoded (SENC) MRI.

METHODS

Feature-tracking software from four different vendors (TomTec, Medis, Circle [CVI], and Neosoft), tagging (Segment), and fastSENC (MyoStrain) were used to determine left ventricular global circumferential strains (GCS) and longitudinal strains (GLS) in 12 healthy volunteers and 12 patients with heart failure. Variability and agreements were assessed using intraclass correlation coefficients for absolute agreement (ICCa) and consistency (ICCc) as well as Pearson correlation coefficients.

RESULTS

For FT-GCS, consistency was excellent comparing different FT vendors (ICCc = 0.84-0.97, r = 0.86-0.95) and in comparison to fast SENC (ICCc = 0.78-0.89, r = 0.73-0.81). FT-GCS consistency was excellent compared with tagging (ICCc = 0.79-0.85, r = 0.74-0.77) except for TomTec (ICCc = 0.68, r = 0.72). Absolute FT-GCS agreements among FT vendors were highest for CVI and Medis (ICCa = 0.96) and lowest for TomTec and Neosoft (ICCa = 0.32). Similarly, absolute FT-GCS agreements were excellent for CVI and Medis compared with both tagging and fast SENC (ICCa = 0.84-0.88), good to excellent for Neosoft (ICCa = 0.77 and 0.64), and lowest for TomTec (ICCa = 0.41 and 0.47). For FT-GLS, consistency was excellent (ICCc ≥ 0.86, r ≥ 0.76). Absolute agreements among FT vendors were excellent (ICCa = 0.91-0.93) or good to excellent for TomTec (ICCa = 0.69-0.85). Absolute agreements (ICCa) were good (CVI 0.70, Medis 0.60) and fair (TomTec 0.41, Neosoft 0.59) compared with tagging, but excellent compared with fast SENC (ICCa = 0.77-0.90).

CONCLUSION

Although absolute agreements differ depending on deformation assessment approaches, consistency and correlation are consistently high regardless of the method chosen, thus indicating reliable strain assessment. Further standardisation and introduction of uniform references is warranted for routine clinical implementation.

Rotation and torsion of the left ventricle with cardiovascular magnetic resonance tagging: comparison of two analysis methods

Background

Left ventricle rotation and torsion are fundamental components of myocardial function, and several software packages have been developed for analysis of these components. The purpose of this study was to compare the suitability of two software packages with different technical principles for analysis of rotation and torsion of the left ventricle during systole.

Methods

A group of hypertrophic cardiomyopathy (HCM) patients (N = 14, age 43 ± 11 years), mutation carriers without hypertrophy (N = 10, age 34 ± 13 years), and healthy relatives (N = 12, age 43 ± 17 years) underwent a cardiovascular magnetic resonance examination, including spatial modulation of magnetization tagging sequences in basal and apical planes of the left ventricle. The tagging images were analyzed offline using a harmonic phase image analysis method with Gabor filtering and a non-rigid registration-based free-form deformation technique. Left-ventricle rotation and torsion scores were obtained from end-diastole to end-systole with both software.

Results

Analysis was successful in all cases with both software applications. End-systolic torsion values between the study groups were not statistically different with either software. End-systolic apical rotation, end-systolic basal rotation, and end-systolic torsion were consistently higher when analyzed with non-rigid registration than with harmonic phase-based analysis (p <  0.0001). End-systolic rotation and torsion values had significant correlations between the two software (p <  0.0001), most significant in the apical plane.

Conclusions

When comparing absolute values of rotation and torsion between different individuals, software-specific reference values are required. Harmonic phase flow with Gabor filtering and non-rigid registration-based methods can both be used reliably in the analysis of systolic rotation and torsion patterns of the left ventricle.

Advanced myocardial characterization in hypertrophic cardiomyopathy: feasibility of CMR-based feature tracking strain analysis in a case-control study

OBJECTIVES

This study aimed to evaluate the feasibility and reproducibility of using cardiovascular magnetic resonance feature tracking (CMR-FT) for analysis of bi-ventricular strain and strain rate (SR) in hypertrophic cardiomyopathy (HCM) patients as well as to explore the correlation between right ventricular (RV) and left ventricular (LV) deformation.

METHODS

A total of 60 HCM patients and 48 controls were studied. Global and segmental peak values of bi-ventricular longitudinal, circumferential, radial strain, and systolic SR were analyzed. Pearson analysis was performed to investigate the correlation of RV and LV deformation. Intra-observer and inter-observer reproducibility were also assessed.

RESULTS

LV mass in the HCM group was significantly higher than that in the control group. LV end-systolic and end-diastolic volume and RV end-systolic and end-diastolic volume in the HCM group were all significantly lower than the correlated parameters in the control group (p < 0.001, respectively), whereas no statistical difference was found in ejection fraction (p > 0.05). Global longitudinal strain (GLS), global longitudinal strain rate (GLSR), global circumferential strain (GCS), global circumferential strain rate (GCSR), global radial strain (GRS), and global radial strain rate (GRSR) of the LV and RV were all significantly lower than the control group, and segmental strain and SR were also true (p < 0.001, respectively). Bi-ventricular strain and SR measurements were highly reproducible at both intra- and inter-observer levels. Additionally, Pearson analysis showed RV GCS, GLS, and GRS positively correlated with LV GCS, GLS, and GRS (r = 0.713, p < 0.001; r = 0.728, p < 0.001; r = 0.730, p < 0.001, respectively).

CONCLUSIONS

CMR-FT is a promising approach to analyze impairment of global and segmental myocardium deformation in HCM patients non-invasively and quantitatively.

KEY POINTS

• CMR-FT allows for advanced myocardial characterization with high reproducibility. • As compared with controls, HCM patients have significant differences in CMR-FT strain analysis while ejection fraction was similar. • CMR-FT may serve as an early biomarker of HCM in subjects at risk.

Inter-study repeatability of circumferential strain and diastolic strain rate by CMR tagging, feature tracking and tissue tracking in ST-segment elevation myocardial infarction

Strain assessment allows accurate evaluation of myocardial function and mechanics in ST-segment elevation myocardial infarction (STEMI). Strain using cardiovascular magnetic resonance (CMR) has traditionally been assessed with tagging but limitations of this technique have led to more widespread use of alternative methods, which may be more robust. We compared the inter-study repeatability of circumferential global peak-systolic strain (Ecc) and peak-early diastolic strain rate (PEDSR) derived by tagging with values obtained using novel cine-based software: Feature Tracking (FT) (TomTec, Germany) and Tissue Tracking (TT) (Circle cvi42, Canada) in patients following STEMI. Twenty male patients (mean age 56 ± 10 years, mean infarct size 13.7 ± 7.1% of left ventricular mass) were randomised to undergo CMR 1-5 days post-STEMI at 1.5 T or 3.0 T, repeated after ten minutes at the same field strength. Ecc and PEDSR were assessed using tagging, FT and TT. Inter-study repeatability was evaluated using Bland-Altman analyses, coefficients of variation (CoV) and intra-class correlation coefficient (ICC). Ecc (%) was significantly lower with tagging than with FT or TT at 1.5 T (- 9.5 ± 3.3 vs. - 17.5 ± 3.8 vs. -15.5 ± 5.2, respectively, p < 0.001) and 3.0 T (- 13.1 ± 1.8 vs. - 19.4 ± 2.9 vs. - 17.3 ± 2.1, respectively, p = 0.001). This was similar for PEDSR (.s-1): 1.5 T (0.6 ± 0.2 vs. 1.5 ± 0.4 vs. 1.0 ± 0.4, for tagging, FT and TT respectively, p < 0.001) and 3.0 T (0.6 ± 0.2 vs. 1.5 ± 0.3 vs. 0.9 ± 0.3, respectively, p < 0.001). Inter-study repeatability for Ecc at 1.5 T was good for tagging and excellent for FT and TT: CoV 16.7%, 6.38%, and 8.65%, respectively. Repeatability for Ecc at 3.0 T was good for all three techniques: CoV 14.4%, 11.2%, and 13.0%, respectively. However, repeatability of PEDSR was generally lower than that for Ecc at 1.5 T (CoV 15.1%, 13.1%, and 34.0% for tagging, FT and TT, respectively) and 3.0 T (CoV 23.0%, 18.6%, and 26.2%, respectively). Following STEMI, Ecc and PEDSR are higher when measured with FT and TT than with tagging. Inter-study repeatability of Ecc is good for tagging, excellent for FT and TT at 1.5 T, and good for all three methods at 3.0 T. The repeatability of PEDSR is good to moderate at 1.5 T and moderate at 3.0 T. Cine-based methods to assess Ecc following STEMI may be preferable to tagging.

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.

Early and Quantitative Assessment of Myocardial Deformation in Essential Hypertension Patients by Using Cardiovascular Magnetic Resonance Feature Tracking

The aims of the study were to identify subclinical global systolic function abnormalities and evaluate influencing factors associated with left ventricular (LV) strain parameters in hypertensive subjects using cardiovascular magnetic resonance imaging feature tracking (CMR-FT). The study enrolled 57 patients with essential hypertension (mean age: 43.04 ± 10.90 years; 35 males) and 26 healthy volunteers (mean age: 38.69 ± 10.44 years; 11 males) who underwent clinical evaluation and CMR examination. Compared with controls, hypertensive patients had significantly impaired myocardial strain values while ejection fraction (EF) did not differ. After multivariate regression analyses adjustment for confounders, the global radial strains (GRS) was independently associated with the mean arterial pressure (MAP) and left ventricular mass index (LVMI) (β = -0.219, p = 0.009 and β = -0.224, p = 0.015, respectively; Adjusted R² = 0.4); the global circumferential strains (GCS) was also independently associated with the MAP and LVMI (β = 0.084, p = 0.002 and β = 0.073, p = 0.01, respectively; Adjusted R² = 0.439); the global longitudinal strains (GLS) was independently associated with the Age and MAP (β = 0.065, p = 0.021 and β = 0.077, p = 0.009, respectively; Adjusted R² = 0.289). Myocardial strain can early detect the myocardial damage and may be an appropriate target for preventive strategies before abnormalities of EF.

Tagged cine magnetic resonance imaging to quantify regional mechanical changes after acute myocardial infarction

PURPOSE

The conventional volumetric approaches of measuring cardiac function are load-dependent, and are not able to discriminate functional changes in the infarct, transition and remote myocardium. We examined phase-dependent regional mechanical changes in the infarct, transition and remote regions after acute myocardial infarction (MI) in a preclinical mouse model using cardiovascular magnetic resonance imaging (CMR).

METHODS

We induced acute MI in six mice with left anterior descending coronary artery ligation. We then examined cardiac (infarct, transition and remote-zone) morphology and function utilizing 9.4 T high field CMR before and 2 weeks after the induction of acute MI. Myocardial scar tissue was evaluated by using CMR with late gadolinium enhancement (LGE). After determining global function through volumetric analysis, regional wall motion was evaluated by measuring wall thickening and radial velocities. Strain rate imaging was performed to assess circumferential contraction and relaxation at the myocardium, endocardium, and epicardium.

RESULTS

There was abnormal LGE in the anterior walls after acute MI suggesting a successful MI procedure. The transition zone consisted of a mixed signal intensity, while the remote zone contained viable myocardium. As expected, the infarct zone had demonstrated severely decreased myocardial velocities and strain rates, suggesting reduced contraction and relaxation function. Compared to pre-infarct baseline, systolic and diastolic velocities (v_S and v_D) were significantly reduced at the transition zone (v_S: -1.86 ± 0.16 cm/s vs -0.68 ± 0.13 cm/s, P < 0.001; v_D: 1.86 ± 0.17 cm/s vs 0.53 ± 0.06 cm/s, P < 0.001) and remote zone (v_S: -1.86 ± 0.16 cm/s vs -0.65 ± 0.12 cm/s, P < 0.001; v_D: 1.86 ± 0.16 cm/s vs 0.51 ± 0.04 cm/s, P < 0.001). Myocardial peak systolic and diastolic strain rates (SR_S and SR_D) were significantly lower in the transition zone (SR_S: -4.2 ± 0.3 s^-1 vs -1.3 ± 0.2 s^-1, P < 0.001; SR_D: 3.9 ± 0.3 s^-1 vs 1.3 ± 0.2 s^-1, P < 0.001) and remote zone (SR_S: -3.8 ± 0.3 s^-1 vs -1.4 ± 0.3 s^-1, P < 0.001; SR_D: 3.5 ± 0.2 s^-1 vs 1.5 ± 0.4 s^-1, P = 0.006). Endocardial and epicardial SR_S and SR_D were similarly reduced in the transition and remote zones compared to baseline.

CONCLUSIONS

This study, for the first time, utilized state-of-the art high-field CMR algorithms in a preclinical mouse model for a comprehensive and controlled evaluation of the regional mechanical changes in the transition and remote zones, after acute MI. Our data demonstrate that CMR can quantitatively monitor dynamic post-MI remodeling in the transition and remote zones, thereby serving as a gold standard tool for therapeutic surveillance.

Changes in Cardiac Morphology and Function in Individuals With Diabetes Mellitus: The UK Biobank Cardiovascular Magnetic Resonance Substudy

BACKGROUND

Diabetes mellitus (DM) is associated with increased risk of cardiovascular disease. Detection of early cardiac changes before manifest disease develops is important. We investigated early alterations in cardiac structure and function associated with DM using cardiovascular magnetic resonance imaging.

METHODS

Participants from the UK Biobank Cardiovascular Magnetic Resonance Substudy, a community cohort study, without known cardiovascular disease and left ventricular ejection fraction ≥50% were included. Multivariable linear regression models were performed. The investigators were blinded to DM status.

RESULTS

A total of 3984 individuals, 45% men, (mean [SD]) age 61.3 (7.5) years, hereof 143 individuals (3.6%) with DM. There was no difference in left ventricular (LV) ejection fraction (DM versus no DM; coefficient [95% CI]: -0.86% [-1.8 to 0.5]; P=0.065), LV mass (-0.13 g/m2 [-1.6 to 1.3], P=0.86), or right ventricular ejection fraction (-0.23% [-1.2 to 0.8], P=0.65). However, both LV and right ventricular volumes were significantly smaller in DM, (LV end-diastolic volume/m2: -3.46 mL/m2 [-5.8 to -1.2], P=0.003, right ventricular end-diastolic volume/m2: -4.2 mL/m2 [-6.8 to -1.7], P=0.001, LV stroke volume/m2: -3.0 mL/m2 [-4.5 to -1.5], P<0.001; right ventricular stroke volume/m2: -3.8 mL/m2 [-6.5 to -1.1], P=0.005), LV mass/volume: 0.026 (0.01 to 0.04) g/mL, P=0.006. Both left atrial and right atrial emptying fraction were lower in DM (right atrial emptying fraction: -6.2% [-10.2 to -2.1], P=0.003; left atrial emptying fraction:-3.5% [-6.9 to -0.1], P=0.043). LV global circumferential strain was impaired in DM (coefficient [95% CI]: 0.38% [0.01 to 0.7], P=0.045).

CONCLUSIONS

In a low-risk general population without known cardiovascular disease and with preserved LV ejection fraction, DM is associated with early changes in all 4 cardiac chambers. These findings suggest that diabetic cardiomyopathy is not a regional condition of the LV but affects the heart globally.

Intermittently tagged real-time MRI reveals internal tongue motion during speech production

PURPOSE

To demonstrate a tagging method compatible with RT-MRI for the study of speech production.

METHODS

Tagging is applied as a brief interruption to a continuous real-time spiral acquisition. Tagging can be initiated manually by the operator, cued to the speech stimulus, or be automatically applied with a fixed frequency. We use a standard 2D 1-3-3-1 binomial SPAtial Modulation of Magnetization (SPAMM) sequence with 1 cm spacing in both in-plane directions. Tag persistence in tongue muscle is simulated and validated in vivo. The ability to capture internal tongue deformations is tested during speech production of American English diphthongs in native speakers.

RESULTS

We achieved an imaging window of 650-800 ms at 1.5T, with imaging signal to noise ratio ≥ 17 and tag contrast to noise ratio ≥ 5 in human tongue, providing 36 frames/s temporal resolution and 2 mm in-plane spatial resolution with real-time interactive acquisition and view-sharing reconstruction. The proposed method was able to capture tongue motion patterns and their relative timing with adequate spatiotemporal resolution during the production of American English diphthongs and consonants.

CONCLUSION

Intermittent tagging during real-time MRI of speech production is able to reveal the internal deformations of the tongue. This capability will allow new investigations of valuable spatiotemporal information on the biomechanics of the lingual subsystems during speech without reliance on binning speech utterance repetition.

Association between reduced myocardial contraction fraction and cardiovascular disease outcomes: The Multi-Ethnic Study of Atherosclerosis

BACKGROUND

The myocardial contraction fraction (MCF: stroke volume to myocardial volume) is a volumetric measure of left ventricular myocardial shortening. We examined the relationship of MCF, measured by cardiac magnetic resonance imaging (cMRI), to incident cardiovascular (CV) events within the Multi-Ethnic Study of Atherosclerosis (MESA).

METHODS

Participants (n = 5000, aged 45-84 years) underwent cMRI.

PRIMARY OUTCOME

CVD events (myocardial infarction, resuscitated cardiac arrest, stroke, coronary heart disease: CHD death, and stroke death).

SECONDARY OUTCOMES

CHD and heart failure (HF) events. Cox proportional hazards regression was used to estimate the hazard ratio (HR) and 95% confidence intervals (CI) for outcomes.

RESULTS

There were 299 incident CVD, 188 CHD, and 151 HF events over 10.2 years. The lowest MCF quartile was associated with an increased risk for incident CVD [HR 2.42, CI: 1.58-3.72], CHD [HR 2.32, CI: 1.36-3.96] and HF events [HR 1.99, CI: 1.15-3.44]. In a model adjusted for demographics, CV risk factors, antihypertensive and lipid-lowering medication use, each standard deviation decrease in MCF was associated with incident CVD [HR 1.42, CI: 1.23-1.64], CHD [HR 1.40, CI: 1.17-1.67] and HF [HR 1.58, CI: 1.30-1.94]. In a subgroup analysis of participants with preserved ejection fraction and without left ventricular hypertrophy, the lowest MCF quartile and each standard deviation decrease in MCF was also associated with an increased risk for incident CVD in fully-adjusted analyses.

CONCLUSIONS

MCF is a novel measure that can be measured using cMRI. In this multi-ethnic cohort, MCF is a measure that can be used to predict incident CVD events.

Non-invasive Multimodality Cardiovascular Imaging of the Right Heart and Pulmonary Circulation in Pulmonary Hypertension

Pulmonary hypertension (PH) is defined as resting mean pulmonary arterial pressure (mPAP) ≥25 millimeters of mercury (mmHg) via right heart (RH) catheterization (RHC), where increased afterload in the pulmonary arterial vasculature leads to alterations in RH structure and function. Mortality rates have remained high despite therapy, however non-invasive imaging holds the potential to expedite diagnosis and lead to earlier initiation of treatment, with the hope of improving prognosis. While historically the right ventricle (RV) had been considered a passive chamber with minimal role in the overall function of the heart, in recent years in the evaluation of PH and RH failure the anatomical and functional assessment of the RV has received increased attention regarding its performance and its relationship to other structures in the RH-pulmonary circulation. Today, the RV is the key determinant of patient survival. This review provides an overview and summary of non-invasive imaging methods to assess RV structure, function, flow, and tissue characterization in the setting of imaging's contribution to the diagnostic, severity stratification, prognostic risk, response of treatment management, and disease surveillance implications of PH's impact on RH dysfunction and clinical RH failure.

Phenotypes of hypertrophic cardiomyopathy. An illustrative review of MRI findings

Objective

The purpose of this article is to review how cardiac MRI provides the clinician with detailed information about the hypertrophic cardiomyopathy (HCM) phenotypes, assessing its morphological and functional consequences.

Conclusion

An understanding of cardiac MRI manifestations of HCM phenotypes will aid early diagnosis recognition and its functional consequences.

Teaching Points

• The phenotypic variability of HCM expands beyond myocardial hypertrophy, to include morphological and functional manifestations, ranging from subtle anomalies to remodelling of the LV with progressive dilatation and thinning of its wall.

• The stages of HCM, which are based on the clinical evidence of disease progression, include subclinical HCM, the classic HCM phenothype, adverse remodelling and overt dysfunction, or end-stage HCM.

• Cardiac MRI provides the clinician with detailed information regarding the HCM phenotypes and enables the assessment of its functional consequences.

Equilibrated warping: Finite element image registration with finite strain equilibrium gap regularization

In this paper, we propose a novel continuum finite strain formulation of the equilibrium gap regularization for image registration. The equilibrium gap regularization essentially penalizes any deviation from the solution of a hyperelastic body in equilibrium with arbitrary loads prescribed at the boundary. It thus represents a regularization with strong mechanical basis, especially suited for cardiac image analysis. We describe the consistent linearization and discretization of the regularized image registration problem, in the framework of the finite elements method. The method is implemented using FEniCS & VTK, and distributed as a freely available python library. We show that the equilibrated warping method is effective and robust: regularization strength and image noise have minimal impact on motion tracking, especially when compared to strain-based regularization methods such as hyperelastic warping. We also show that equilibrated warping is able to extract main deformation features on both tagged and untagged cardiac magnetic resonance images.

Left ventricular torsion rate and the relation to right ventricular function in pediatric pulmonary arterial hypertension

The right ventricle and left ventricle are physically coupled through the interventricular septum. Therefore, changes in the geometry and mechanics of one ventricle can directly affect the function of the other. In treatment of pediatric pulmonary arterial hypertension, the left ventricle is often overlooked, with clinical focus primarily on improving right ventricular function. Pediatric pulmonary arterial hypertension represents a disease distinct from adult pulmonary arterial hypertension based on etiology and survival rates. We aimed to assess left ventricular torsion rate in pediatric pulmonary arterial hypertension and its role in right ventricular dysfunction. Cardiac magnetic resonance images with tissue tagging were prospectively acquired for 18 pediatric pulmonary arterial hypertension (WHO class I) patients and 17 control subjects with no known cardiopulmonary disease. The pulmonary arterial hypertension cohort underwent cardiac magnetic resonance within 48 hours of clinically indicated right heart catheterization. Using right heart catheterization data, we computed single beat estimation of right ventricular end-systolic elastance (as a measure of right ventricular contractility) and ventricular vascular coupling ratio (end-systolic elastance/arterial afterload). Left ventricular torsion rate was quantified from harmonic phase analysis of tagged cardiac magnetic resonance images. Ventricular and pulmonary pressures and pulmonary vascular resistance were derived from right heart catheterization data. Right ventricular ejection fraction and interventricular septum curvature were derived from cardiac magnetic resonance. Left ventricular torsion rate was significantly reduced in pulmonary arterial hypertension patients compared to control subjects (1.40 ± 0.61° vs. 3.02 ± 1.47°, P < 0.001). A decrease in left ventricular torsion rate was significantly correlated with a decrease in right ventricular contractility (end-systolic elastance) ( r = 0.61, P = 0.007), and an increase in right ventricular systolic pressure in pulmonary arterial hypertension kids ( r = -0.54, P = 0.021). In both pulmonary arterial hypertension and control subjects, left ventricular torsion rate correlated with right ventricular ejection fraction (controls r = 0.45, P = 0.034) (pulmonary arterial hypertension r = 0.57, P = 0.032). In the pulmonary arterial hypertension group, interventricular septum curvature demonstrated a strong direct relationship with right ventricular systolic pressure ( r = 0.7, P = 0.001) and inversely with left ventricular torsion rate ( r = -0.57, P = 0.013). Left ventricular torsion rate showed a direct relationship with ventricular vascular coupling ratio ( r = 0.54, P = 0.021), and an inverse relationship with mean pulmonary arterial pressure ( r = -0.60, P = 0.008), and pulmonary vascular resistance ( r = -0.47, P = 0.049). We conclude that in pediatric pulmonary arterial hypertension, reduced right ventricular contractility is associated with decreased left ventricular torsion rate.

Vortical features for myocardial rotation assessment in hypertrophic cardiomyopathy using cardiac tagged magnetic resonance

Left ventricular rotational motion is a feature of normal and diseased cardiac function. However, classical torsion and twist measures rely on the definition of a rotational axis which may not exist. This paper reviews global and local rotation descriptors of myocardial motion and introduces new curl-based (vortical) features built from tensorial magnitudes, intended to provide better comprehension about fibrotic tissue characteristics mechanical properties. Fifty-six cardiomyopathy patients and twenty-two healthy volunteers have been studied using tagged magnetic resonance by means of harmonic phase analysis. Rotation descriptors are built, with no assumption about a regular geometrical model, from different approaches. The extracted vortical features have been tested by means of a sequential cardiomyopathy classification procedure; they have proven useful for the regional characterization of the left ventricular function by showing great separability not only between pathologic and healthy patients but also, and specifically, between heterogeneous phenotypes within cardiomyopathies.

Regional myocardial strain measurements from 4DCT in patients with normal LV function

BACKGROUND

CT SQUEEZ is a new automated technique to evaluate regional endocardial strain by tracking features on the endocardium from 4D cine CT data. The objective of this study was to measure the range of endocardial regional strain (RS_CT) values obtained with CT SQUEEZ in the normal human left ventricle (LV) from standard clinical 4D coronary CTA exams.

METHODS

RS_CT was measured over the heart cycle in 25 humans with normal LV function using cine CT from three vendors. Mean and standard deviation of RS_CT values were computed in 16 AHA LV segments to estimate the range of values expected in the normal LV.

RESULTS

Curves describing RS_CT vs. time were consistent between subjects. There was a slight gradient of decreasing minimum RS_CT value (increased shortening) from the base to the apex of the heart. Mean RS_CT values at end-systole were: base = -32% ± 1%, mid = -33% ± 1%, apex = -36% ± 1%. The standard deviation of the minimum systolic RS_CT in each segment over all subjects was 5%. The average time to reach maximum shortening was 34% of the RR interval.

CONCLUSIONS

Regional strain (RS_CT) can be rapidly obtained from standard gated coronary CCTA protocols using 4DCT SQUEEZ processing. We estimate that 95% of normal LV end-systolic RS_CT values will fall between -23% and -43%; therefore, we hypothesize that an RS_CT value higher than -23% will indicate a hypokinetic segment in the human heart.

Use of integrated imaging and serum biomarker profiles to identify subclinical dysfunction in pediatric cancer patients treated with anthracyclines

BACKGROUND

Anthracycline induced cardiomyopathy is a major cause of mortality and morbidity among pediatric cancer survivors. It has been postulated that oxidative stress induction and inflammation may play a role in the pathogenesis of this process. Accordingly, the present study performed an assessment of biomarker profiles and functional imaging parameters focused upon potential early determinants of anthracycline induced cardiomyopathy.

METHODS

Patients (10-22 years) were prospectively enrolled between January 2013 and November 2014. Thirteen subjects completed the study and underwent serial cardiac magnetic resonance imaging and plasma biomarker profiling performed 24-48 h after the first anthracycline dose and at set dose intervals. In addition, we collected plasma samples from 62 healthy controls to examine normal plasma biomarker profiles.

RESULTS

Left ventricular ejection fraction (LVEF) decreased from 64.3 ± 6.2 at the first visit to 57.5 ± 3.3 (p = 0.004) 1 year after chemotherapy. A decline in longitudinal strain magnitude occurred at lower cumulative doses. A differential inflammatory/matrix signature emerged in anthracycline induced cardiomyopathy patients compared to normal including increased interleukin-8 and MMP levels. With longer periods of anthracycline dosing, MMP-7, a marker of macrophage proteolytic activation, increased by 165 ± 54% whereas interleukin-10 an anti-inflammatory marker decreased by 75 ± 13% (both p < 0.05). MMP7 correlated with time dependent changes in EF.

CONCLUSIONS

Asymptomatic pediatric patients exposed to anthracycline therapy develop abnormal strain parameters at lower cumulative doses when compared to changes in EF. A differential biomarker signature containing both inflammatory and matrix domains occur early in anthracycline treatment. Dynamic changes in these domains occur with increased anthracycline doses and progression to anthracycline induced cardiomyopathy. These findings provide potential prognostic and mechanistic insights into the natural history of anthracycline induced cardiomyopathy.

TRIAL REGISTRATION NUMBER

NCT03211520 Date of Registration February 13, 2017, retrospectively registered.

One-Year Follow-up Study Detects Myocardial Changes with Cardiovascular Magnetic Resonance Tagging in Active Rheumatoid Arthritis

RATIONALE AND OBJECTIVES

To evaluate the effects of 1 year of medical treatment on myocardial function in active rheumatoid arthritis (RA).

MATERIALS AND METHODS

Thirty-nine female patients with RA without any known cardiovascular disease underwent a cardiovascular magnetic resonance (CMR) examination before and after 1 year of antirheumatic treatment. The population comprised untreated active early RA (ERA) and chronic RA patients, who were grouped accordingly. The CMR protocol included volumetric determinations, late gadolinium enhancement imaging, myocardial tagging, and native T1 mapping. DAS28-CRP disease activity scores were calculated before and after the treatment.

RESULTS

Results are reported as median (quartile 1-quartile 3). Time to peak diastolic filling rate improved in ERA (495 [443-561] ms vs 441 [340-518] ms, P = .018). Peak diastolic mean mid short-axis circumferential strain rate of all six segments was improved (82 [74-91] %/s vs 91 [77-100] %/s, P = .05), particularly in the anterior segment (82 [63-98] %/s vs 86 [77-109] %/s, P = .013). DAS28-CRP decreased in ERA (3.8 [3.2-4.1] vs 1.6 [1.4-2.2], P < .001). In chronic RA, no statistically significant improvement was detected.

CONCLUSIONS

Early treatment of active RA is important, as myocardial function detected with CMR tagging improved in ERA in parallel with decreasing inflammatory activity.

Prediction of infarct size and adverse cardiac outcomes by tissue tracking-cardiac magnetic resonance imaging in ST-segment elevation myocardial infarction

OBJECTIVES

We investigated whether quantification of global left ventricular (LV) strain by tissue tracking-CMR (TT-CMR) can estimate the infarct size and clinical outcomes in patients with acute myocardial infarction (MI).

METHODS

We retrospectively registered 247 consecutive patients (58 ± 12 years; male, 81%) who underwent 1.5-T CMR within 1 month after ST-segment elevation MI (median, 4 days; interquartile range, 3-6 days), and 20 age- and sex-matched controls (58 ± 11 years; male, 80%). TT-CMR analysis was applied to cine-images to measure global LV radial, circumferential and longitudinal peak strains (GRS, GCS and GLS, respectively). Adverse cardiac events were defined as cardiac death and hospitalization for heart failure.

RESULTS

During the follow-up (median, 7.8 years), 20 patients (8.1%) experienced adverse events. LV myocardial deformation was significantly decreased in MI patients compared to controls and closely related to the infarct size. The GRS, GCS and GLS were all significant predictors of adverse cardiac events. In particular, a GLS > -14.1% was independently associated with a > 5-fold increased risk for adverse events, even after adjustment for the LV ejection fraction and infarct size.

CONCLUSIONS

TT-CMR-derived LV strain is significantly related to the infarct size and adverse events. GLS measurement provides strong prognostic information in MI patients.

KEY POINTS

• TT-CMR provides reliable quantification of LV strain in MI patients. • TT-CMR allows prediction of the infarct size and adverse events. • In particular, GLS by TT-CMR had independent prognostic value in MI patients.

Update on assessment and management of primary cardiac involvement in systemic sclerosis

Primary cardiac involvement is a common and severe complication of systemic sclerosis, which may affect all of the hearts' structural components, including pericardium, myocardium, endocardium, cardiac valves, and conduction system. While cardiac disease can be clinically silent and only diagnosed in autopsy, new imaging modalities such as speckle-tracking echocardiography and cardiovascular magnetic resonance may reveal various abnormal findings in the majority of patients. Cardiovascular magnetic resonance evaluation should include assessment of left and right ventricular function, inflammation (STIR T2-weighted sequences (T2-W) for edema detection), and fibrosis (T1-weighted sequences 15 min after Gd-DTPA contrast medium injection (late-gadolinium enhancement). Notably, cardiac disease is responsible for about one-fourth of systemic sclerosis-related deaths. Systematic studies for the assessment and therapy of systemic sclerosis-related cardiac complications, as well as relevant guidelines from the European League Against Rheumatism and the American College of Rheumatology, are currently lacking. However, research advances reviewed herein allow for a better understanding of the mechanisms that alter cardiac function. Implementation of such knowledge should reduce cardiac morbidity and mortality in systemic sclerosis patients.

Assessment of reverse remodeling predicted by myocardial deformation on tissue tracking in patients with severe aortic stenosis: a cardiovascular magnetic resonance imaging study

BACKGROUND

The technique of tissue tracking with balanced steady-state free precession cine sequences was introduced, and allowed myocardial strain to be derived directly, offering advantages over traditional myocardial tagging. The aim of this study was to evaluate the correlation between reverse remodeling as an outcome and left ventricular strain using cardiovascular magnetic resonance imaging (CMR) tissue tracking, and to evaluate prediction of reverse remodeling by myocardial deformation in patients with severe aortic stenosis (AS).

METHODS

We enrolled 63 patients with severe AS and normal left ventricular (LV) systolic function (ejection fraction > 60%), who underwent both CMR and transthoracic echocardiography (Echo) before surgical aortic valve replacement (AVR). CMR at 1.5 T, including non and post-contrast T1 mapping for extracellular volume (ECV), was carried out to define the amount of myocardial fibrosis. Cardiac Performance Analysis software was used to derive myocardial deformation as strain parameters from three short-axis cine views (basal, mid and apical levels) and apical 2, 3, and 4 chamber views. The primary outcome was reverse remodeling, as evaluated by regression of left ventricular mass index (LVMI).

RESULTS

Median follow-up was 28.8 months (interquartile range 11.3-38.3 months). As evaluated by LVMI between baseline and follow-up, mass regression was significantly improved after AVR (baseline 145.9 ± 37.0 [g/m2] vs. follow-up 97.7 ± 22.2[g/m2], p < 0.001). Statistically significant Pearson's correlations with LVMI regression were observed for longitudinal global strain (r = -0.461, p < 0.001), radial strain (r = 0.391, p = 0.002), and circumferential strain (r = -0.334, p = 0.009). A simple linear regression analysis showed that all strain parameters could predict the amount of LVMI regression (P < 0.05), as well as non-contrast T1 value (beta = -0.314, p < 0.001) and ECV (beta = -2.546, p = 0.038). However, ECV had the lowest predictive power (multiple r2 = 0.071). Multiple regression analysis showed strain could independently predict the amount of LVMI regression and the longitudinal global strain (beta = -3.335, p < 0.001).

CONCLUSION

Longitudinal global strain measured by CMR tissue tracking as a technique was correlated with reverse remodeling as LVMI regression and was predictive of this outcome. As a simple and practical method, tissue tracking is promising to assess strain and predict reverse remodeling in severe AS, especially in patients with suboptimal Echo image quality.

Myocardial deformation assessment using cardiovascular magnetic resonance-feature tracking technique

BACKGROUND

Cardiovascular magnetic resonance (CMR) imaging is an important modality that allows the assessment of regional myocardial function by measuring myocardial deformation parameters, such as strain and strain rate throughout the cardiac cycle. Feature tracking is a promising quantitative post-processing technique that is increasingly used. It is commonly applied to cine images, in particular steady-state free precession, acquired during routine CMR examinations.

OBJECTIVE

To review the studies that have used feature tracking techniques in healthy subjects or patients with cardiovascular diseases. The article emphasizes the advantages and limitations of feature tracking when applied to regional deformation parameters. The challenges of applying the techniques in clinics and potential solutions are also reviewed.

RESULTS

Research studies in healthy volunteers and/or patients either applied CMR-feature tracking alone to assess myocardial motion or compared it with either established CMR-tagging techniques or to speckle tracking echocardiography. These studies assessed the feasibility and reliability of calculating or determining global and regional myocardial deformation strain parameters. Regional deformation parameters are reviewed and compared. Better reproducibility for global deformation was observed compared with segmental parameters. Overall, studies demonstrated that circumferential was the most reproducible deformation parameter, usually followed by longitudinal strain; in contrast, radial strain showed high variability.

CONCLUSION

Although feature tracking is a promising tool, there are still discrepancies in the results obtained using different software packages. This highlights a clear need for standardization of MRI acquisition parameters and feature tracking analysis methodologies. Validation, including physical and numerical phantoms, is still required to facilitate the use of feature tracking in routine clinical practice.

Feature tracking CMR reveals abnormal strain in preclinical arrhythmogenic right ventricular dysplasia/ cardiomyopathy: a multisoftware feasibility and clinical implementation study

BACKGROUND

Regional right ventricular (RV) dysfunction is the hallmark of Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy (ARVD/C), but is currently only qualitatively evaluated in the clinical setting. Feature Tracking Cardiovascular Magnetic Resonance (FT-CMR) is a novel quantitative method that uses cine CMR to calculate strain values. However, most prior FT-CMR studies in ARVD/C have focused on global RV strain using different software methods, complicating implementation of FT-CMR in clinical practice. We aimed to assess the clinical value of global and regional strain using FT-CMR in ARVD/C and to determine differences between commercially available FT-CMR software packages.

METHODS

We analyzed cine CMR images of 110 subjects (39 overt ARVD/C [mutation+/phenotype+], 40 preclinical ARVD/C [mutation+/phenotype-] and 31 control) for global and regional (subtricuspid, anterior, apical) RV strain in the horizontal longitudinal axis using four FT-CMR software methods (Multimodality Tissue Tracking, TomTec, Medis and Circle Cardiovascular Imaging). Intersoftware agreement was assessed using Bland Altman plots.

RESULTS

For global strain, all methods showed reduced strain in overt ARVD/C patients compared to control subjects (p < 0.041), whereas none distinguished preclinical from control subjects (p > 0.275). For regional strain, overt ARVD/C patients showed reduced strain compared to control subjects in all segments which reached statistical significance in the subtricuspid region for all software methods (p < 0.037), in the anterior wall for two methods (p < 0.005) and in the apex for one method (p = 0.012). Preclinical subjects showed abnormal subtricuspid strain compared to control subjects using one of the software methods (p = 0.009). Agreement between software methods for absolute strain values was low (Intraclass Correlation Coefficient = 0.373).

CONCLUSIONS

Despite large intersoftware variability of FT-CMR derived strain values, all four software methods distinguished overt ARVD/C patients from control subjects by both global and subtricuspid strain values. In the subtricuspid region, one software package distinguished preclinical from control subjects, suggesting the potential to identify early ARVD/C prior to overt disease expression.

Cardiac MRI: a Translational Imaging Tool for Characterizing Anthracycline-Induced Myocardial Remodeling

Cardiovascular side effects of cancer therapeutics are the leading causes of morbidity and mortality in cancer survivors. Anthracyclines (AC) serve as the backbone of many anti-cancer treatment strategies, but dose-dependent myocardial injury limits their use. Cumulative AC exposure can disrupt the dynamic equilibrium of the myocardial microarchitecture while repeated injury and repair leads to myocyte loss, interstitial myocardial fibrosis, and impaired contractility. Although children are assumed to have greater myocardial plasticity, AC exposure at a younger age portends worse prognosis. In older patients, there is lower overall survival once they develop cardiovascular disease. Because aberrations in the myocardial architecture predispose the heart to a decline in function, early detection with sensitive imaging tools is crucial and the implications for resource utilization are substantial. As a comprehensive imaging modality, cardiac magnetic resonance (CMR) imaging is able to go beyond quantification of ejection fraction and myocardial deformation to characterize adaptive microstructural and microvascular changes that are important to myocardial tissue health. Herein, we describe CMR as an established translational imaging tool that can be used clinically to characterize AC-associated myocardial remodeling.