Myocardial Tagging Research Articles

Fatty Heart and Subclinical Left Ventricular Dysfunction

> Those who have dissected or inspected many [bodies] have at least learnt to doubt; while others who are ignorant of anatomy and do not take the trouble to attend it are in no doubt at all. > > Giovanni B. Morgagni > > The beginning of knowledge is the discovery of something we do not understand. > > Frank Herbert Fatty degeneration of the human heart was first reported by the French cardiologist Corvisart more 200 years ago in 1806,1 while the first distinction of epicardial/pericardial fat from intramyocardial fat was made by the German physician scientist Virchow in 1858.2 Interest in these observations and their cardiovascular consequences continue to grow as techniques for noninvasive assessment of pericardial and intramyocardial fat improve. The amount of fat stored in nonadipocyte tissue (liver and muscle) is usually minimal and tightly regulated; however, recent studies have reported cardiac steatosis in human metabolic diseases such as obesity, diabetes mellitus, and metabolic syndrome.3–5 Mahmod et al,6 in this issue of Circulation: Cardiovascular Imaging , compared 39 subjects with symptomatic (64%) and asymptomatic severe aortic stenosis (AS) to 20 healthy controls and found increased myocardial fat in patients with AS. Using 1H-magnetic resonance (MR) spectroscopy, the authors measured myocardial triglyceride content (MTC) and reported that patients with symptomatic AS had the highest level of MTC as compared with asymptomatic patients and healthy control subjects. MTC values correlated inversely with regional myocardial function using circumferential and longitudinal strain obtained by myocardial tagging methods, with a gradation between the control, asymptomatic AS, and symptomatic AS groups. The authors were able to show a modest correlation of MTC with myocyte lipid content on biopsy samples of a subgroup of patients who underwent surgery ( r s =0.66; P =0.036).6 Most importantly, the authors demonstrated near complete …

Tagging of cardiac magnetic resonance images in the polar coordinate system: Physical principles and practical implementation

In current magnetic resonance practice, myocardial tagging is implemented by laying down a rectilinear presaturation grid over the heart. Although both the geometry and the deformation of the heart are better described in the polar coordinate system, practical methods for laying down polar grids have been elusive. The theory and implementation of high-density tagging in the polar coordinate system is described in this study. Tagging sequences for generating high-density tagging patterns in both radial and circular directions have been developed. The approach, theoretical basis, and experimental results of the suggested sequences for efficient polar tagging are described in this article. A 10-ms preparation tagging sequence was tested for generating compact radial and circular tag patterns in a magnetization preparation time comparable to binomial rectilinear grid tagging. The sequence was successfully tested on both phantoms and human subjects. Direct myocardial tagging in the polar coordinate system is practical in acquisition times similar to Cartesian tagging. The deformation patterns of radial and circular tag lines can be used to isolate and analyze the circumferential and radial components of myocardial motion. Further work remains to establish the reliability and robustness of the techniques for a variety of clinical applications.

101 VALIDATION OF MAGNETIC RESONANCE FEATURE TRACKING FOR LONGITUDINAL SYSTOLIC AND DIASTOLIC STRAIN CALCULATION WITH SPATIAL MODULATION OF MAGNETISATION IMAGING ANALYSIS

IntroductionFeature-tracking (FT) analysis offers a novel, fast and practicable method to calculate strain from routinely acquired steady state free precession (SSFP) images without the need to perform additional tagged sequences....

151 MYOCARDIAL PERFUSION, STRAIN AND PRE-CONTRAST T1 VALUES IN MODERATE ASYMPTOMATIC AORTIC STENOSIS

<h3>Introduction</h3> In severe aortic stenosis (AS) myocardial perfusion and myocardial strain (in particular longitudinal strain-LS) are reduced. Reduced myocardial perfusion in severe AS is thought to occur in the subendocardium due to increased LV pressure, leading to reduced LS and increased fibrosis. Our group previously showed a good correlation between pre-contrast T1 values using SHMOLLI (Shortened Modified Look-Locker Inversion recovery) sequence and histological quantification of diffuse fibrosis in severe AS. We hypothesised that impaired myocardial perfusion in patients with moderate AS would relate to impaired LS and increased pre-contrast T1 values (reflecting more diffuse fibrosis). <h3>Methods</h3> 31 patients (8 female) with asymptomatic moderate AS (by echo criteria) and normal ejection fraction were recruited. All subjects underwent CMR scanning at 1.5T for pre-contrast T1-mapping using the ShMOLLI sequence, stress and rest perfusion imaging, tagging and valve assessment. Average T1 values were analysed on a per-case basis. Perfusion scans were analysed to determine the myocardial perfusion reserve index (MPRI) and tagging to determine strain. <h3>Results</h3> All patients (average age 67±12 years) underwent CMR scanning at 1.5 T. The average MPRI was 1.3±0.4. Average T1 values were 956±32 ms. There was a significant correlation between MPRI and LS (&lt;0.05, r=−0.4, figure&nbsp;1) but not circumferential strain (CS). Average LS was −11.1%±2%, average CS was −17%±3%. There was also a significant correlation of MPRI with aortic valve area (as measured by CMR planimetry mean (1.7±0.4 cm², p&lt;0.05 r=0.4). There was no significant correlation between MPRI and pre-contrast T1 values. Pre-contrast T1 values correlated strongly with LV mass (mean 147±40 g) (r=0.4 p&lt;0.01) and peak aortic velocity (mean 3.1±0.4 m/s) (p&lt;0.0001 r=0.5). <h3>Conclusions</h3> In moderate AS, there is a significant correlation between reduced MPRI and impaired longitudinal but not circumferential strain. This supports the hypothesis that impairment of myocardial perfusion predominantly affects the subendocardial longitudinal myocardial fibres (rather than the mid-wall circumferential fibres) in moderate AS. The exact relationship of perfusion and diffuse fibrosis in moderate AS is yet to be fully established. In this study pre-contrast T1 values (as a surrogate marker for diffuse fibrosis) were not affected by changes in myocardial perfusion.

103 INTER-STUDY REPRODUCIBILITY OF STRAIN MEASURMENTS BY CARDIAC MRI: A COMPARISON OF FEATURE TRACKING, SINGLE BREATH-HOLD TAGGING AND MULTI BREATH-HOLD TAGGING

<h3>Introduction</h3> Strain and strain rate are important indices of LV function and are of prognostic value in many cardiac conditions. The current gold standard for its measurement is myocardial tissue tagging using cardiac MRI (CMR) that requires acquisition of additional sequences and semi-automatic post-processing. Feature tracking (FT), a technique that relies on automatic tracking of voxels of tissue at the cavity-tissue interface throughout the cardiac cycle, has recently been introduced and shown to have reasonable inter-study reproducibility (Cofficient of variation (CoV) ∼20%) in healthy volunteers. The inter-study reproducibility of FT has not been reported in any patient groups nor compared to MRI tagging. We sought to compare circumferential strain and strain rate values using Tagging and FT, and determine their inter-study reproducibility in patients with severe Aortic Stenosis (AS). <h3>Methods</h3> CMR was performed twice on eight patients with isolated severe AS without obstructive coronary disease, on a 1.5 T (Siemens Avanto) scanner (median interval 12 days). Complementary tagged (CSPAMM) images were acquired with both single breath-hold (SBH: temporal resolution 42 ms) and multiple breath-hold (MBH: high temporal resolution 17 ms) sequences. InTag post-processing toolbox (Creatis, Lyon, France) in OsiriX (Geneva, Switzerland) was used to calculate the Circumferential Peak Systolic Strain (PSS), Peak Systolic Strain Rate (PSSR) and Peak Early Diastolic Strain Rate (PEDSR). Diogenes CMR FT software (TomTec Imaging Systems, Munich, Germany) was used to calculate the same parameters on the short-axis stack of SSFP cine images at basal, mid and apical levels, using an average of epicaridal and endocardial contours. <h3>Results</h3> PSS, PSSR and PEDSR were calculated globally (average of base, mid, apex) as well as individually for each slice. FT revealed overall higher values for global measurements than with both tagging techniques (p&lt;0.05 for SBH/MBH values vs FT) (table&nbsp;1). However, excluding the apical slice, there was no difference between the PSS and PEDSR between the Tagging techniques and FT. The inter-study reproducibility results are shown in Table&nbsp;2. Results were comparable between Tagging and FT. The apical slice was found to be the least reproducible (CoV 20.38%, 19.69%, 16.77% for SBH, MBH and FT respectively). Excluding the apical slice improves the reproducibility of both tagging and FT. <h3>Conclusions</h3> This study has demonstrated that Global PSS, PSSR and PEDSR values are considerably higher with FT than Tagging in patients with severe AS unless the apical slice is excluded. The reproducibility of strain and strain rate measurements with FT are comparable to that of tagging in severe AS patients. Given that FT does not require additional image acquisitions to standard cine images this technique is likely to become the preferred method for strain and strain rate quantification with MRI.

1030Role of cardiac magnetic resonance and echocardiography prior to cardiac resynchronization therapy

Purpose: Cardiac resynchronization therapy is an established method for treatment of patients with heart failure. Optimal left ventricular lead implantation guided by novel imaging techniques appears to be a promising method to increase the response to this therapy. Methods: 29 patients scheduled for cardiac resynchronization therapy underwent detailed ECHO and cardiac magnetic resonance studies prior to CRT device implantation. The aim of the imaging studies was to determine an optimal pacing site for the left ventricular lead placement. The off-line analysis was performed by two experienced readers in a blinded fashion. CMR was performed on 3T system (Siemens). Cine, late gadolinium enhancement and myocardial tagging sequences were acquired. Image software Segment (Sweden) was used for left ventricular segmentation. Left ventricular wall motion and myocardial scar analysis were performed in all 17 segments . Tagging sequences were analysed with inTag (Universite de Lyon) in short axis slices at basal, mid ventricular and apical levels of the left ventricle. The care was taken to ensure correct alignment of these slices to achieve the same segmentation as with echocardiography. Standard echocardiographic parasternal and apical views were stored and analysed off-line. Left ventricular radial, longitudinal and circumferential strains were assessed using commercially available software (EchoPac 6.1). The cut-off value for regional longitudinal strain was – 4.5% to discriminate between transmural (>50%) and nontransmural (<50%) myocardial scar (Roes S.D., Mollema S.A., Bax J.J., Am J Cardiol 2009;104;312-317). Results: Wall motion analysis was possible in all 493 segments in CMR and in 472 (96%) in echocardiography studies. Mean ejection fraction of the left ventricle was 29 ± 5 % when assessed by echocardiography and 23 ± 9 % in CMR studies (P = 0.0005). The average LV EDVi was 99 ± 21 ml/m2 (ECHO) and 115 ± 32 ml/m2 (CMR) (P = 0.003). Scar transmurality was significantly overestimated by ECHO using the longitudinal strain cut-off -4.5% for discrimination between transmural and nontransmural scar – 2.8 times. The dyssynchrony analysis targeted to define the latest activated LV segment showed significant agreement between the two methods. The exact segments agreement was detected in 19 cases (66%). In 6 cases (21%) targeted segment was ± 1 neighbour segment. Discordance between the latest activated segment was detected in 4 patiens (14 %). Conclusions: We have demonstrated that CMR has a potential to improve diagnostic preoperative assessment in patients with severe heart failure and might be a useful tool for LV dyssynchrony assessment. CMR is an excellent method for scar assessment and is a useful tool for LV strain analysis.

Left ventricular mechanical dyssynchrony by cardiac magnetic resonance is greater in patients with strict vs nonstrict electrocardiogram criteria for left bundle-branch block

Left bundle-branch block (LBBB) is a marker of increased delay between septal and left ventricular (LV) lateral wall electrical activation and is a predictor of which patients will benefit from cardiac resynchronization therapy. Recent analysis has suggested that one-third of patients meeting the conventional electrocardiogram criteria for LBBB are misdiagnosed, and new strict LBBB criteria have been proposed. We tested the hypothesis that patients with strict LBBB have greater LV mechanical dyssynchrony than do patients meeting the nonstrict LBBB criteria, whereas there is no difference between patients with nonstrict LBBB and LV conduction delay with a QRS duration of 110 to 119 ms. Sixty-four patients referred for primary prevention implantable cardioverter-defibrillators underwent 12-lead electrocardiogram and cardiac magnetic resonance myocardial tagging. The patients were classified as strict LBBB, nonstrict LBBB, or non-LBBB (nonspecific LV conduction delay with a QRS duration of 110-119 ms). The time delay between septal and lateral LV wall peak circumferential strain (septal-to-lateral wall delay) was measured by cardiac magnetic resonance. Patients with strict LBBB (n = 31) had a greater septal-to-lateral wall delay compared with patients with nonstrict LBBB (n = 19) (210 ± 137 ms vs 122 ± 102 ms, P = .045). There was no significant difference between nonstrict LBBB and non-LBBB (n = 14) septal-to-lateral wall delay (122 ± 102 ms vs 100 ± 86 ms, P = .51). Strict LBBB criteria identify patients with greater mechanical dyssynchrony compared with patients only meeting the nonstrict LBBB criteria, whereas there was no significant difference between patients with nonstrict LBBB and non-LBBB. The greater observed LV dyssynchrony may explain why patients with strict LBBB have a better response to cardiac resynchronization therapy.

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

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

Comparison of myocardial tagging and feature tracking in patients with severe aortic stenosis

Transcatheter aortic valve implantation (TAVI) has become an effective treatment for severe aortic stenosis (AS) in patients considered to be at high surgical risk. However, data relating to myocardial function and deformation in these patients are rare. Cardiovascular magnetic resonance (CMR) tagging has been established as non-invasive technique for the accurate measurement of myocardial motion. However, additional tagging datasets are necessary and the post-processing procedure is time-consuming. Recently, the novel technique of feature tracking (FT) was introduced, with which myocardial strain can be derived directly from balanced steady-state free precession (bSSFP) cine sequences. The study aim was to compare tagging with FT in patients with high-grade AS and who had been considered for TAVI. Thirty patients with severe AS underwent cardiac magnetic resonance imaging at 1.5 T (Philips Achieva). A stack of serial short-axis slices was used to assess left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV), and LV mass and function. TomTec 2D Cardiac Performance Analysis software was used to derive myocardial deformation parameters from three short-axis cine views (basal, medial and apical levels) using bSSFP. All patients also underwent myocardial tagging on identical short-axis views, and data acquired from FT and tagging were compared. The mean left ventricular ejection fraction (LVEF), LVEDV and LVESV (57 ± 14%, 158 ± 58 ml, and 74 ± 48 ml, respectively) were all normal. All patients demonstrated concentric hypertrophy of the left ventricle with an increased basal septal thickness (16 ± 3 mm), LV mass (126 ± 40 g) and indexed LV mass (68 ± 23 g/m2, papillary muscles excluded). Bland-Altman analysis revealed a reasonable agreement between basal and medial circumferential strain (cc), and a good correlation was observed between tagging and FT for the derived basal and medial cc (Pearson's correlation coefficient 0.83 for basal, 0.74 for medial). Basal rotation was impaired compared to previous studies in patients with AS, but medial and apical rotations were comparable. The apical peak diastolic rotation velocity was faster compared to earlier analyses. Rotation, peak systolic and end-diastolic rotation velocity did not demonstrate any correlation or acceptable agreement between FT and tagging. The inter-observer agreement as assessed by the intra- class correlation coefficient for FT showed good results for the cc (basal 0.94, medial 0.83, apical 0.75). To the present authors' knowledge, this is the first study to assess myocardial motion using tagging and FT in patients with AS prior to TAVI. A reasonable agreement was found for the basal and medial cc between both techniques. Estimated cc-values using FT were systematically higher than those with tagging, but this might have been due to the different techniques employed. Although FT is a promising method to assess cc, further studies including the evaluation of standard values--and investigations with different diseases are necessary.

The effect of microvascular obstruction and intramyocardial hemorrhage on contractile recovery in reperfused myocardial infarction: insights from cardiovascular magnetic resonance.

BackgroundFollowing acute myocardial infarction (AMI), microvascular obstruction (MO) and intramyocardial hemorrhage (IMH) adversely affect left ventricular remodeling and prognosis independently of infarct size. Whether this is due to infarct zone remodeling, changes in remote myocardium or other factors is unknown. We investigated the role of MO and IMH in recovery of contractility in infarct and remote myocardium.MethodsThirty-nine patients underwent cardiovascular magnetic resonance (CMR) with T2-weighted and T2* imaging, late gadolinium enhancement (LGE) and myocardial tagging at 2, 7, 30 and 90 days following primary percutaneous coronary intervention for AMI. Circumferential strain in infarct and remote zones was stratified by presence of MO and IMH.ResultsOverall, infarct zone strain recovered with time (p < 0.001). In the presence of MO with IMH and without IMH, epicardial strain recovered (p = 0.03, p < 0.01 respectively), but mid-myocardial or endocardial strain did not (mid-myocardium: p = 0.05, p = 0.12; endocardium: p = 0.27, p = 0.05, respectively). By day 90, infarcts with MO had more attenuated strain in all myocardial layers compared to infarcts without MO (p < 0.01); those with IMH were attenuated further (p < 0.01). Remote myocardial strain was similar across groups at all time-points (p > 0.2). Infarct transmural extent did not correlate with strain (p > 0.05 at each time point). In multivariable logistic regression, MO and IMH were the only significant independent predictors of attenuated 90-day infarct zone strain (p = 0.004, p = 0.011, respectively).ConclusionsStrain improves within the infarct zone overall following reperfusion with or without MO or IMH. Mid-myocardial and endocardial infarct contractility is diminished in the presence of MO, and further in the presence of IMH. MO and IMH are greater independent predictors of infarct zone contractile recovery than infarct volume or transmural extent.

Epicardial left ventricular myocardial rotation correlates with resting myocardial blood flow in type 2 diabetes mellitus patients with angiographically normal coronary arteries

Background Type 2 Diabetes Mellitus (T2DM) and prediabetes are associated with an increased cardiovascular risk and heart failure independent of the presence of obstructive coronary artery disease, caused in part by myocardial microvascular dysfunction. Recent studies have reported contractile dysfunction and increased rotation with the onset of diabetic cardiomyopathy in uncomplicated T2DM patients. Independently, higher resting myocardial blood flow (MBF) has been reported in T2DM. The objective of this study was to determine whether there is a correlation between LV Epicardial Rotation (LV ER) and resting MBF in T2DM patients with angiographically normal coronaries, measured by tissue tagging and perfusion cardiovascular Magnetic Resonance (CMR). Methods Sixty five patients with no coronary stenosis >30% on invasive angiography were recruited and categorized into T2DM, prediabetes and normal controls groups according to American Diabetes Association guidelines. All patients underwent rest and adenosine stress myocardial perfusion CMR at a single mid-LV location, cine imaging covering the entire heart and myocardial tissue tagging in three LV short axis locations (apical, mid LV and basal). LV volumes and mass were calculated from cine images. LV rotation in three myocardial layers (endocardial, midmyocardial and epicardial) was calculated from CSPAMM tissue images using Tag Track (Gyrotools, Zurich). For this study, only rest MBF was calculated using Fermi-constrained deconvolution for the entire myocardium. Results Patient characteristics and results are shown in Table 1. Patients with T2DM had significantly higher resting MBF than the two other groups. Corresponding mid LV ER was higher in T2DM patients compared to patients with prediabetes and normal controls (Figure 1) (not statistically significant). Univariate analysis showed a significant positive correlation between MBF and LV ER in the entire study population (Pearson coefficient (r) of 0.25, p = 0.05). In the individual groups, the linear determination coefficient (R2) showed that LV ER in T2DM patients had stronger positive correlation (R2 = 0.31) with resting MBF than in patients with prediabetes (R2 = 0.16) and controls (R2 = 0.29), Figure 1. Conclusions T2DM patients when compared to age-matched patients with prediabetes and normal controls have higher peak LV ER. Resting MBF correlates with LV ER. These results suggest that LV ER analysis in uncomplicated T2DM patients may be useful for non-invasive screening of early subtle contractile dysfunction associated with microvascular dysfunction in diabetes patients.

Feature tracking strain is a promising functional analysis technique in single ventricle patients

Background Feature-tracking Strain (FT S) is a new technique that performs myocardial Strain evaluation on Steady State Free Precession (SSFP) cines without the need for myocardial tagging. As a pilot study to determine whether FT S may be useful in single ventricle patients, we applied this analysis to patients with hypoplastic left heart syndrome (HLHS) and tricuspid atresia (TA). Methods We retrospectively reviewed 22 patients with a history of Fontan palliation (median age 8.2, range 2 - 27.5 years) who had cardiac MRIs with a Siemens 1.5 Tesla Avanto (Siemens Medical Systems) scanner, 11 with TA, 11 with HLHS. All had steady-state free precession (SSFP) sequences of 4-chamber (4ch) cine and short axis (SAx) cine stacks from cardiac base to apex. Ejection fraction (EF) was calculated from the SAx stack on a Leonardo workstation (Siemens, Inc.). FT S analysis of the 4ch cine was performed off-line with TomTec 2D Cardiac Performance Analysis (version 1.0, TomTec Imaging Systems) following two tracking protocols: endocardial trace only (Endo), epicardial to endocardial trace (Endo-Epi) (Figure 1). Pearson correlation was used to test relationship between absolute global longitudinal Strain (GLSabs) and EF. Differences in GLS between tracking methods were tested with Bland Altman analysis. Results Mean EF was 60.2%, 95% CI 42.6% to 77.8%. Mean GLS was -15.7 (95% CI -6.8 to -24.7) by Endo., and -16.5 (95% CI -6.9 to -26.1) by Endo-Epi tracking methods. There was fair correlation (Figure 2) between GLSabs and EF using the Endo method (Pearson r = 0.67, p mean Endo GLS of 0.8, with a wide distribution in difference values, 95% CI 2.9 to -4.5. Morphologic ventricle type (single LV vs single RV) did not make a difference in GLS to EF correlations when compared to the mixed cohort. Mean GLS for single LVs was somewhat higher than single RVs, but this difference did not reach statistical significance. Conclusions There is fair correlation between GLS and EF in single ventricle patients with feature-tracking Strain analysis tracking the ventricular endocardium. Validation in a larger sample is warranted. Comparison of FT S with tagged harmonic phase MRI in single ventricle patients may further validate this promising technique in defining regional and global strain. Funding

Comparison of magnetic resonance feature tracking for longitudinal strain calculation with spatial modulation of magnetization imaging analysis

Background Feature-tracking (FT) analysis offers a novel, fast and practicable method to calculate strain from routinely acquired steady state free precession (SSFP) images without the need to perform additional tagged sequences. There is no validation of this technique, however, against a reference standard myocardial tagging analysis for any strain parameter other than mid-left ventricular whole slice circumferential strain in children. In an adult study of patients with dilated cardiomyopathy (DCM) and healthy controls, we sought to validate the FT method (TomTec Imaging systems, Munich) against spatial modulation of magnetization (SPAMM) tissue tagging analysis (Cardiac Image Modeling Package (CIMTAG), University of Auckland) for the computation of long axis function. Methods We compared measures of peak systolic longitudinal strain from the horizontal long axis view using the 2 techniques in 30 patients (median age 42 yr, male 40%). Normal healthy adults were identified from an ongoing prospective, observational research study examining the effects of living kidney donation on cardiovascular structure and function (NCT01028703) while DCM patients underwent routine tagging during CMR studies performed for clinical requirements. A timed retrospective off-line analysis was performed on matched tagged and SSFP slices by 2 independent blinded observers (WEM and RJT). Results Mean peak systolic longitudinal strain and strain rate determined by FT were significantly reduced in DCM patients compared with healthy controls (-6.7 ± 1.7% vs. -20.4 ± 3.7%, P<0.001 and -1.21 ± 0.14 /s vs. -0.61 ± 0.09 /s, both P<0.0001). The mean peak systolic longitudinal strain of DCM patients determined by CIMTAG (-6.7 ± 1.7%) and FT (-7.0 ± 1.4%) was not significantly different (P = NS). In an analysis of all patients, mean FT systolic longitudinal strain values were highly correlated with CIMTAG values, with a Pearson correlation coefficient of 0.67 (P=0.0001, Figure 1). The individual longitudinal systolic strain values obtained for each

In vivo validation of an ultra-high field, high temporal resolution myocardial tagging technique for assessment of diastolic function in mice

Background Heart failure with preserved ejection fraction accounts for approximately half of all heart failure cases and is associated with similar morbidity and mortality. Although abnormalities of diastolic function are felt to play an important role, no specific treatments have been identified for this common condition, primarily because of poor understanding of its pathophysiology. Despite development of several murine models of this disease, accurate non-invasive assessment of diastolic function has been challenging. Echocardiographic measurements have been limited by small heart sizes, rapid ventricular rates and high inter-observer variability. The aim of this study was to assess the ability of ultra-high field, high temporal resolution CMR tagging to assess diastolic function in mice, compared to the gold-standard technique of invasive pressure-volume loop analysis.

Myocardial Tagging with MR Imaging: Overview of Normal and Pathologic Findings

Magnetic resonance tagging is used to evaluate the dynamic deformation of lines or grids superimposed on the myocardium during the cardiac cycle. From these data, a specific postprocessing procedure provides two kinds of metrics: (a) three orthogonal components of myocardial motion (longitudinal, circumferential, and radial), and (b) rotation and torsion. Strain expresses the local myocardial deformation and is prone to important physiologic heterogeneities. Peak systolic strain is in the range of -15% to -20% for the longitudinal and circumferential components (fiber shortening) and 30%-40% for the radial component (wall thickening). The helical arrangement of myofibers that run in opposite directions at the epicardium and endocardium explains systolic twist (~15°). This torsion may be enhanced during the early stage of several diseases (eg, hypertrophic cardiomyopathy) or in heart failure with a normal left ventricular ejection fraction. Strain is generally impaired in ischemic heart disease and cardiomyopathy, but the most diagnostically significant finding is the early identification of contractile dysfunction on the basis of longitudinal and circumferential strain reduction in patients with apparently preserved systolic function. Thus, strain impairment appears to be a sensitive and promising marker of subclinical disease, with the potential for improving patient management.

MR Cine DENSE Dyssynchrony Parameters for the Evaluation of Heart Failure: Comparison With Myocardial Tissue Tagging

We sought to assess the effectiveness of automated mechanical dyssynchrony (MD) parameters based on regional heterogeneity of strain (circumferential [CURE], longitudinal [LURE], and radial uniformity ratio estimates) relative to parameters based on regional time to peak contraction with cardiac magnetic resonance (CMR) cine DENSE (Displacement Encoding with Stimulated Echoes) validated with myocardial tissue tagging (MTT) strain data. Dyssynchrony measures based on the Fourier transformation (FT) of regional strain, such as CURE (previously evaluated in cardiac resynchronization therapy candidates), directly assess MD and yield straightforward global dyssynchrony indexes; however, performance relative to the 12-segment standard deviation of time to peak strain (SD12) or maximal regional delay in time to peak strain is unknown. Cine DENSE and MTT were obtained with CMR (1.5-T Siemens Avanto, Siemens, Erlangen, Germany) in 13 canines: 3 normal control subjects, 5 with tachycardia pacing-induced heart failure (HF) and left bundle branch ablation (LBBB-HF), and 5 with HF and narrow QRS (NQRS-HF). Strain and dyssynchrony parameters were determined with both CMR methods. Both HF groups had reduced peak strains and left ventricular ejection fraction compared with normal cases. There was strong agreement between cine DENSE and MTT on the basis of intraclass correlation coefficients (CURE: 0.99, 95% CI: 0.96 to 1.00; LURE: 0.92, 95% CI: 0.77 to 0.98; circumferential strain [E(CC)]: 0.95, 95% CI: 0.72 to 0.99; longitudinal strain [E(LL)]: 0.82, 95% CI: 0.42 to 0.97). The FT-based metrics (scale 0 to 1), in particular CURE, discriminated highly between LBBB-HF and NQRS-HF groups (median difference): CURE: 0.60, 95% CI: 0.43 to 0.76; LURE: 0.39, 95% CI: 0.19 to 0.58; radial uniformity ratio estimate: 0.22, 95% CI: 0.04 to 0.40). In contrast, relative confidence intervals for group differences in time-to-peak parameters were wide, indicating less consistent discrimination (median difference): SD12-E(CC): 52.5, 95% CI: -4.0 to 109.2; SD12-E(LL): 40.9, 95% CI: -5.3 to 87.1; SD12-radial strain: 42.0, 95% CI: 0.4 to 83.6). Correlations between FT-based and time-to-peak parameters were significant (CURE/SD12-E(CC): r = -0.62, p = 0.03; LURE/SD12-E(LL): r = -0.76, p = 0.005) but not as tight as correlations between time-to-peak parameters. Automated FT-based circumferential, radial, and longitudinal dyssynchrony measures compare favorably with time-to-peak parameters. Cine DENSE was effective for this application and validated with MTT. Further clinical evaluation in cardiac resynchronization therapy candidates with CMR or other imaging modalities is warranted.

089 Regression of myocardial oedema is related to improvement in myocardial contractility following reperfused acute myocardial infarction

IntroductionMyocardial oedema is a feature of reperfused acute myocardial infarction (AMI), and contributes to stunning of peri-infarct myocardium (the “area at risk”). Regression of oedema on T2 weighted (T2w) cardiovascular...

Comparison of cardiac MRI tissue tracking and myocardial tagging for assessment of regional ventricular strain

This study sought to compare regional measures of ventricular strain by tissue tracking (TT) to those derived from myocardial tagging (MT) within cardiac MR (CMR), in normal subjects and patients with hypertrophic cardiomyopathy. CMR images from 13 normal subjects and 11 subjects with hypertrophic cardiomyopathy were retrospectively analyzed. For each subject, equivalent mid-papillary level short-axis cine steady-state free precession and MT slices from the same examination were evaluated. The time to peak circumferential strain and magnitude of the peak strain were calculated for 6 matched left ventricular segments. Data from 24 slices (n = 144 segments) were compared. The mean difference between techniques in magnitude of peak strain and time to peak strain was 1 ± 9% and 1 ± 58 ms, respectively. The mean difference in the standard deviation of time to peak strain within a slice was 0 ± 19 ms (mean cardiac cycle duration 1,013 ± 204 ms). Bland-Altman analysis showed closer agreement in time to peak strain than peak strain magnitude. Measurements of segmental time to peak strain by TT and MT were in close agreement; agreement for the magnitude of peak segmental strain was more modest. The TT approach does not add to CMR examination time and may be a useful tool for the assessment of ventricular synchrony.

Comparison between three-dimensional speckle-tracking echocardiography and cardiac magnetic resonance imaging for quantification of left ventricular volumes and function

We evaluated the accuracy of three-dimensional speckle-tracking echocardiography (3DSTE) to evaluate left ventricular (LV) volumes, ejection fraction (EF), and global circumferential strain (CS) in comparison with cardiac magnetic resonance imaging (MRI) in a healthy population. A total of 45 out of 50 consecutive healthy subjects (38 males, age 45 ± 15 years) successfully underwent both 3DSTE and MRI on the same day. Three-dimensional echocardiography data sets were analysed using speckle tracking to measure LV end-diastolic and end-systolic volumes, EF, and global CS. With MRI, the method of discs approximation was used to obtain volumes and the EF, whereas CS was acquired using myocardial tissue tagging. Inter-technique comparisons included regression and the Bland-Altman analysis. For quantification of LV volumes, 3DSTE correlated well with MRI (r: 0.75-0.81), but volumes were significantly underestimated with relatively large biases (13-34 mL) and wide limits of agreement (SD: 11-25 mL). However, excellent accuracy was revealed for measurement of EF by 3DSTE with a good correlation (r: 0.91), minimal bias, and narrow limits of agreement (0.6 ± 1.7%) compared with MRI. For measurement of CS, a large mean bias was found between techniques (10.0%), despite narrow limits of agreement (SD: 1.7%) and a good correlation between techniques (r: 0.80). Although 3DSTE-derived LV volumes are underestimated in most patients compared with MRI, measurement of the LVEF revealed excellent accuracy. Measurements of CS were systematically greater (i.e. more negative) with 3DSTE than MRI, which likely reflects various inter-technique differences that preclude direct comparability of their measurements.

Recovery of regional myocardial function and myocardial oedema following reperfused acute myocardial infarction

Summary We investigated the relationship between myocardial oedema and recovery of regional myocardial function in patients with acute reperfused myocardial infarction (MI). Early after acute MI, oedema in the peri-infarct zone, as delineated by T2 weighted (T2w) cardiovascular magnetic resonance (CMR) imaging, demonstrated significantly reduced strain as compared to remote myocardium. The recovery of regional function in the peri-infarct zone closely followed the resolution of hyperenhancement on T2w CMR. In addition, both transmural and subendocardial infarcts showed a degree of functional recovery after acute MI. Background Myocardial tissue oedema is a feature of acute reperfused myocardial infarction, and contributes to stunning of viable peri-infarct myocardium (the ‘area at risk’). Regression of oedema on T2w CMR imaging is related to improved myocardial contractility post MI in animal models. Whether a similar relationship between myocardial oedema and regional myocardial function exists in man is not currently known. We hypothesised that the resolution of tissue oedema correlates with recovery of regional contractile function. Methods We studied patients after primary percutaneous coronary intervention for first ST-elevation MI. Patients underwent CMR with T2w, myocardial tagging and late gadolinium enhancement imaging at median 2, 30 and 90 days post reperfusion. Infarct size, regional circumferential strain, intensity and volume of myocardial oedema were measured for infarct zone, peri-infarct zone (area at risk) and remote myocardium. Oedema and infarction were defined as zones with signal intensity 2 standard deviations above remote myocardium in T2w and LGE imaging respectively. T2w signal intensity was corrected using a ratio to remote myocardium. Results Thirty patients had CMR imaging at all three time points and had adequate image quality with sufficient peri-infarct oedema for quantitative analysis. Circumferential strain was significantly diminished in infarct and peri-infarct zones compared to remote myocardium (means -0.149 vs. -0.184 vs. -0.236, P<0.01 between groups and P<0.01 for trend). Remote myocardium showed no significant change in strain over time (F=1.44, P=0.24), whilst the peri-infarct zone (F=6.03, P=0.004) and infarct zone (F=20.34, P<0.001) showed a significant increase in magnitude. This change closely mirrored resolution of both intensity and volume of T2 hyperenhancement (Figure 1). Decreased circumferential strain correlated significantly with T2 volume (r=0.30; P<0.01) and corrected T2 signal intensity (r=0.28; P<0.01). Due to the unexpected finding of recovery of function in the infarct zone, we analysed the 8 patients with complete transmural infarction. The area of fully transmural infarction showed a trend towards significant resolution of strain with time (means -0.103 (day 2), -0.148 (day 30) and -0.194 (day 90); P=0.050 for trend).