A dual propagation contours technique for semi-automated assessment of systolic and diastolic cardiac function by CMR

Spironolactone improves left atrial function and atrioventricular coupling in patients with resistant hypertension

To determine the blood pressure independent effects of spironolactone on left atrial (LA) size and function in patients with resistant hypertension (RHTN). Patients with RHTN (n = 36, mean age 55 ± 7) were prospectively recruited. Spironolactone was initiated at 25 mg/day and increased to 50 mg/day after 4 weeks. Other antihypertensives were withdrawn to maintain constant blood pressure. Cardiac magnetic resonance imaging was performed at baseline and after 6 months of spironolactone treatment and changes in LA functional metrics were assessed. LA size and function parameters were improved (p < 0.05) from baseline to month-6: LA volumes indexed to body surface area (LAVI) were reduced (LAVImaximum 41.4 ± 12 vs. 33.2±9.7 mL/m2; LAVIpre-A 32.6 ± 9.8 vs. 25.6 ± 8.1 mL/m2; median LAVIminimum 18.5 [13.9-24.8] vs. 14.1 [10.9-19.2] mL/m2); left atrioventricular coupling index was reduced (28.2 ± 11.5 vs. 22.7 ± 9.2%); LA emptying fractions (LAEF) were increased (median total LAEF 52.4 [48.7-60.3] vs. 55.9 [50.3-61.1] %; active LAEF 40.2 ± 8.6 vs. 43.1 ± 7.8%). LA global longitudinal strain in the active phase was increased (16.3 ± 4.1 vs. 17.8 ± 4.2%). The effect of spironolactone was similar in patients with high (N = 18) and normal (N = 18) aldosterone status (defined by plasma renin activity and 24-h urine aldosterone). Treatment of RHTN with spironolactone is associated with improvements in LA size and function, and atrioventricular coupling, regardless of whether aldosterone levels were normal or high at baseline. This study suggests the need for larger prospective studies examining effects of mineralocorticoid receptor antagonists on atrial function and atrioventricular coupling.

Semi-automatic muscle segmentation in MR images using deep registration-based label propagation

Fully automated approaches based on convolutional neural networks have shown promising performances on muscle segmentation from magnetic resonance (MR) images, but still rely on an extensive amount of training data to achieve valuable results. Muscle segmentation for pediatric and rare diseases cohorts is therefore still often done manually. Producing dense delineations over 3D volumes remains a time-consuming and tedious task, with significant redundancy between successive slices. In this work, we propose a segmentation method relying on registration-based label propagation, which provides 3D muscle delineations from a limited number of annotated 2D slices. Based on an unsupervised deep registration scheme, our approach ensures the preservation of anatomical structures by penalizing deformation compositions that do not produce consistent segmentation from one annotated slice to another. Evaluation is performed on MR data from lower leg and shoulder joints. Results demonstrate that the proposed few-shot multi-label segmentation model outperforms state-of-the-art techniques.

Reduced Left Atrial Emptying Fraction and Chymase Activation in Pathophysiology of Primary Mitral Regurgitation

Increasing left atrial (LA) size predicts outcomes in patients with isolated mitral regurgitation (MR). Chymase is plentiful in the human heart and affects extracellular matrix remodeling. Chymase activation correlates to LA fibrosis, LA enlargement, and a decreased total LA emptying fraction in addition to having a potential intracellular role in mediating myofibrillar breakdown in LA myocytes. Because of the unreliability of the left ventricular ejection fraction in predicting outcomes in MR, LA size and the total LA emptying fraction may be more suitable indicators for timing of surgical intervention.

Novel Noninvasive Assessment of Pulmonary Arterial Stiffness Using Velocity Transfer Function

Background

Pulmonary artery (PA) stiffness is associated with increased pulmonary vascular resistance (PVR). PA stiffness is accurately described by invasive PA impedance because it considers pulsatile blood flow through elastic PAs. We hypothesized that PA stiffness and impedance could be evaluated noninvasively by PA velocity transfer function (VTF), calculated as a ratio of the frequency spectra of output/input mean velocity profiles in PAs.

Methods and Results

In 20 participants (55±19 years, 14 women) undergoing clinically indicated right‐sided heart catheterization, comprehensive phase‐contrast and cine‐cardiac magnetic resonance imaging was performed to calculate PA VTF, along with right ventricular mass and function. PA impedance was measured as a ratio of frequency spectra of invasive PA pressure and echocardiographically derived PA flow waveforms. Mean PA pressure was 29.5±13.6 mm Hg, and PVR was 3.5±2.8 Wood units. A mixed‐effects model showed VTF was significantly associated with PA impedance independent of elevation in pulmonary capillary wedge pressure (P=0.005). The mean of higher frequency moduli of VTF correlated with PVR (ρ=0.63; P=0.003) and discriminated subjects with low (n=10) versus elevated PVR (≥2.5 Wood units, n=10), with an area under the curve of 0.95, similar to discrimination by impedance (area under the curve=0.93). VTF had a strong inverse association with right ventricular ejection fraction (ρ=−0.73; P<0.001) and a significant positive correlation with right ventricular mass index (ρ=0.51; P=0.02).

Conclusions

VTF, a novel right ventricular–PA axis coupling parameter, is a surrogate for PA impedance with the potential to assess PA stiffness and elevation in PVR noninvasively and reliably using cardiac magnetic resonance imaging.

Impact of medical therapy for cardiovascular disease on left ventricular diastolic properties and remodeling

Background

Left ventricular (LV) remodeling and diastolic properties are affected by both underlying cardiovascular disease/cardiovascular disease risk factors (CVDRFs) and corresponding medication therapy. However, these effects may not be apparent in patients with multiple CVDRFs. We evaluated the effect of medication classes on hemodynamics in a patient cohort with normal LV dimensions and systolic function.

Methods

In 38 participants (61 ± 7 years, 64 ± 9% LV ejection fraction) undergoing coronary angiography, LV pressure measurement and cardiac magnetic resonance imaging was performed. The effects of coronary artery disease (CAD), CVDRFs and their corresponding medication therapy on LV parameters were analyzed considering the number of CAD/CVDRFs and ‘adequacy’ of medication therapy to address each existing condition with specific indication-based medication classes.

Results

Of the patients studied, 68% had CAD, 87% had hypertension, 87% had dyslipidemia, and 45% had diabetes. Neither individual or total number of CAD/CVDRFs were associated with overall differences in LV diastolic parameters. However, those without (n = 20) and with (n = 18) ‘adequate’ medication therapy for underlying CAD/CVDRFs differed in values of LV end diastolic pressure (17 ± 4 vs. 11 ± 5 mm Hg, P < 0.001), wall stress (3.9 ± 1.6 vs. 2.2 ± 1.2 x1000 N/m², P < 0.001), pressure/volume ratio (0.13 ± 0.04 vs. 0.08 ± 0.03 mm Hg/ml, P < 0.01), and mass/volume ratio (0.77 ± 0.20 vs. 0.92 ± 0.24 g/ml, P < 0.05), but not in systolic blood pressure or LV mass index.

Conclusions

Our results suggest an association between the degree of LV diastolic impairment and LV remodeling with the intensity of treatment for CAD/CVDRFs. Comprehensive treatment of all identified CAD/CVDRFs may be an important factor for the preservation of diastolic function.

Plasma xanthine oxidase activity is related to increased sodium and left ventricular hypertrophy in resistant hypertension

BACKGROUND

The extra-renal effects of aldosterone on left ventricular (LV) structure and function are exacerbated by increased dietary sodium in persons with hypertension. Previous studies demonstrated endothelial dysfunction and increased oxidative stress with high salt diet in normotensive salt-resistant subjects. We hypothesized that increased xanthine oxidase (XO), a product of endothelial cells, is related to 24-h urinary sodium and to LV hypertrophy and function in patients with resistant hypertension (RHTN).

METHODS

The study group included persons with RHTN (n = 91), defined as a blood pressure > 140/90 mmHg on ≥ 3 medications at pharmacologically effective doses. Plasma XO activity and 24-h urine were collected, and cardiac magnetic resonance imaging (MRI) was performed to assess LV function and morphology. Sixty-seven normotensive persons on no cardiovascular medications served as controls. A subset of RHTN (n = 19) received spironolactone without salt restriction for six months with follow-up XO activity measurements and MRI analyses.

RESULTS

XO activity was increased two-fold in RHTN vs. normal and was positively correlated with LV mass, LV diastolic function, and 24-h urinary sodium. In RHTN patients receiving spironolactone without salt restriction, LV mass decreased, but LV diastolic function and XO activity did not improve. Baseline urinary sodium was positively associated with rate of change of LV mass to volume ratio and the LV E/A ratio.

CONCLUSIONS

These results demonstrate a potential role of endothelium-derived oxidative stress and excess dietary salt in the pathophysiology of LV hypertrophy and diastolic dysfunction in persons with RHTN unaffected by the addition of spironolactone.

Refractory Hypertension Is not Attributable to Intravascular Fluid Retention as Determined by Intracardiac Volumes

Refractory hypertension (RfHTN) is an extreme phenotype of antihypertensive treatment failure defined as lack of blood pressure control with ≥5 medications, including a long-acting thiazide and a mineralocorticoid receptor antagonist. RfHTN is a subgroup of resistant hypertension (RHTN), which is defined as blood pressure >135/85 mm Hg with ≥3 antihypertensive medications, including a diuretic. RHTN is generally attributed to persistent intravascular fluid retention. It is unknown whether alternative mechanisms are operative in RfHTN. Our objective was to determine whether RfHTN is characterized by persistent fluid retention, indexed by greater intracardiac volumes determined by cardiac magnetic resonance when compared with controlled RHTN patients. Consecutive patients evaluated in our institution with RfHTN and controlled RHTN were prospectively enrolled. Exclusion criteria included advanced chronic kidney disease and masked or white coat hypertension. All enrolled patients underwent biochemical testing and cardiac magnetic resonance. The RfHTN group (n=24) was younger (mean age, 51.7±8.9 versus 60.6±11.5 years; P=0.003) and had a greater proportion of women (75.0% versus 43%; P=0.02) compared with the controlled RHTN group (n=30). RfHTN patients had a greater left ventricular mass index (88.3±35.0 versus 54.6±12.5 g/m²; P<0.001), posterior wall thickness (10.1±3.1 versus 7.7±1.5 mm; P=0.001), and septal wall thickness (14.5±3.8 versus 10.0±2.2 mm; P<0.001). There was no difference in B-type natriuretic peptide levels and left atrial or ventricular volumes. Diastolic dysfunction was noted in RfHTN. Our findings demonstrate greater left ventricular hypertrophy without chamber enlargement in RfHTN, suggesting that antihypertensive treatment failure is not attributable to intravascular volume retention.

Left Ventricular Torsion Shear Angle Volume Approach for Noninvasive Evaluation of Diastolic Dysfunction in Preserved Ejection Fraction

BACKGROUND

Accurate noninvasive diagnostic tools for evaluating left ventricular (LV) diastolic dysfunction (LVDD) are limited in preserved LV ejection fraction. We previously proposed the relationship of normalized rate of change in LV torsion shear angle (φ') to corresponding rate of change in LV volume (V') during early diastole (represented as -dφ'/dV') as a measure of LV diastolic function. We prospectively evaluated diagnostic accuracy of -dφ'/dV' in respect to invasive LV parameters.

METHODS AND RESULTS

Participants (n=36, age 61±7 years) with LV ejection fraction ≥50% and no acute myocardial infarction undergoing coronary angiography for chest pain and/or dyspnea evaluation were studied. High-fidelity invasive LV pressure measurements and cardiac magnetic resonance imaging with tissue tagging were performed. τ, the time constant of LV diastolic relaxation, was 58±10 milliseconds (mean±SD), and LV end-diastolic pressure was 14.5±5.5 mm Hg. Cardiac magnetic resonance imaging-derived -dφ'/dV' was 5.6±3.7. The value of -dφ'/dV' correlated with both τ and LV end-diastolic pressure (r=0.39 and 0.36, respectively, P<0.05). LVDD was defined as τ>48 milliseconds and LV end-diastolic pressure >12 mm Hg (LVDD1), or, alternatively, τ>48 milliseconds and LV end-diastolic pressure >16 mm Hg (LVDD2). Area under the curve (AUC) of -dφ'/dV' for identifying LVDD1 was 0.83 (0.67-0.98, P=0.001), with sensitivity/specificity of 72%/100% for -dφ'/dV' ≥6.2. AUC of -dφ'/dV' for identifying LVDD_2 was 0.82 (0.64-1.00, P=0.006), with sensitivity/specificity of 76%/85% for -dφ'/dV' ≥6.9. There were good limits of agreement between pre- and post-nitroglycerin -dφ'/dV'.

CONCLUSIONS

The -dφ'/dV' obtained from the LV torsion volume loop is a promising parameter for assessing global LVDD with preserved LV ejection fraction and requires further evaluation.

Diastolic dysfunction measured by cardiac magnetic resonance imaging in women with signs and symptoms of ischemia but no obstructive coronary artery disease

BACKGROUND

Women with chest pain and no obstructive coronary artery disease often have coronary microvascular dysfunction (CMD), diagnosed by invasive coronary reactivity testing (CRT). The relationship between CMD and diastolic function measured by cardiac magnetic resonance imaging (CMR) is not well described.

METHODS

41 women with suspected CMD underwent CRT and CMR. Left ventricular end-diastolic pressure (LVEDP), coronary flow reserve (CFR) and coronary blood flow (CBF) were measured invasively. Resting CMR of these women and 20 reference controls was assessed for LV mass, septal wall thickness, ejection fraction (LVEF), end-diastolic volume (EDV), peak filling rate (PFR) and time-to-peak-filling rate (tPFR). Pearson correlations and linear regression models were made.

RESULTS

Mean age was 55±9, all had LVEF≥50%, and 16/41 (40%) had LVEDP>15mmHg. CMD (CFR<2.5 or CBF<50%) was present in 34/41 (83%) women. tPFR (mean 178±110ms) and PFR (mean 3.2±0.64 EDV/s) were not significantly different in women with or without CMD. tPFR increased with age (r=0.37, p=0.017) and septal wall thickness (r=0.47, p=0.002), while PFR decreased with age (r=-0.45, p=0.003). There was an inverse relationship between CFR and tPFR (r=-0.3, p=0.058). Increasing mass was associated with decreasing CBF (p=0.02). Compared to controls, cases had lower LVEF (p=0.049) and lower EDV (p=0.0002).

CONCLUSION

In women with signs and symptoms of ischemia but no obstructive coronary artery disease, CMD and elevated LVEDP are prevalent. While non-endothelial dependent CMD may be related to diastolic dysfunction, further investigation is needed regarding links between CMD, diastolic dysfunction and the development of heart failure with preserved LVEF.

A graph theoretic approach for computing 3D+time biventricular cardiac strain from tagged MRI data

Tagged magnetic resonance imaging (tMRI) is a well-established method for evaluating regional mechanical function of the heart. Many techniques have been developed to compute 2D or 3D cardiac deformation and strain from tMRI images. In this paper, we present a new method for measuring 3D plus time biventricular myocardial strain from tMRI data. The method is composed of two parts. First, we use a Gabor filter bank to extract tag points along tag lines. Second, each tag point is classified to one of a set of indexed reference tag lines using a point classification with graph cuts (PCGC) algorithm and a motion compensation technique. 3D biventricular deformation and strain is computed at each image time frame from the classified tag points using a previously published finite difference method. The strain computation is fully automatic after myocardial contours are defined near end-diastole and end-systole. An in-vivo dataset composed of 30 human imaging studies with a range of pathologies was used for validation. Strains computed with the PCGC method with no manual corrections were compared to strains computed from both manually placed tag points and a manually-corrected unwrapped phase method. A typical cardiac imaging study with 10 short-axis slices and 6 long-axis slices required 30 min for contouring followed by 44 min of automated processing. The results demonstrate that the proposed method can reconstruct accurate 3D plus time cardiac strain maps with minimal user intervention.

Mitral Annular Kinetics, Left Atrial, and Left Ventricular Diastolic Function Post Mitral Valve Repair in Degenerative Mitral Regurgitation

Objective

The relationship of mitral annular (MA) kinetics to left ventricular (LV) and left atrial (LA) function before and after mitral valve (MV) repair has not been well studied. Here we sought to provide comprehensive analysis that relates to MA motions, and LA and LV diastolic function post MV repair.

Methods

Three-dimensional analyses of mitral annular motion, LA function, and LV volumetric and diastolic strain rates were performed on 35 degenerative mitral regurgitation (MR) patients at baseline and 1-year post MV repair, and 51 normal controls, utilizing cardiac magnetic resonance imaging with tissue tagging.

Results

All had normal LV ejection fraction (EF) at baseline. LV and LA EFs decreased 1-year post-surgery vs. controls. LV early diastolic myocardial strain rates decreased post-surgery along with decreases in normalized early diastolic filling rate, E/A ratio, and early diastolic MA relaxation rates. Post-surgical LA late active kick remained higher in MR patients vs. control. LV and LA EFs were significantly associated with peak MA centroid to apex shortening. Furthermore, during LV systolic phase, peak LV ejection and LA filling rates were significantly correlated with peak MA centroid to apex shortening rate, respectively. While during LV diastolic phase, both peak early diastolic MA centroid to apex relaxation rate and LA ejection rate were positively significantly associated with LV peak early diastolic filling rate.

Conclusion

MA motion is significantly associated with LA and LV function. Mitral annular motion, left atrial function, and LV diastolic strain rates are still impaired 1 year post MV repair. Long-term effects of these impairments should be prospectively evaluated.

Improved Right Ventricular Performance with Increased Tricuspid Annular Excursion in Athlete's Heart

Background

Marathon runners (MTH) and patients with mitral regurgitation (MR) exhibit left ventricular (LV) overload, and LV geometric changes in these groups have been reported. In this study, right ventricular (RV) adaptation to chronic volume overload was evaluated in MTH and MR and normal controls together with interventricular septal remodeling and tricuspid annulus (TA) motion.

Methods

A total of 60 age-matched subjects (including 19 MTH, 17 isolated chronic compensated MR patients, and 24 normal subjects) underwent conventional cine and tagged cardiac magnetic resonance imaging. Myocardial strain and curvature were computed on the interventricular septum and RV free wall. A dual-propagation technique was applied to construct RV volume-time curves for a single cardiac cycle. Similarly, the TA was tracked throughout the cardiac cycle to create displacement over time curve.

Results

Septal curvature was significantly lower in MTH and MR compared to controls. No significant differences in RV free-wall strain or RV ejection fraction were noted among the three groups. However, longitudinal TA excursion was significantly higher in MTH compared to controls (p = 0.0061). The peak late diastolic TA velocity in MR was significantly faster than MTH (p = 0.0031) and controls (p = 0.020).

Conclusion

Increased TA kinetics allows for improved RV performance in MTH. Septal remodeling was observed in both MR and MTH, therefore a direct relationship of septal remodeling to TA kinetics in athlete’s heart could not be elucidated in this study.

Longitudinal Impedance Tomography for Blood Pressure Characterization of Valve Deformation

Aorta is formed in a dynamic environment which gives rise to imbalances between many forces that tend to extend the diameter and length. Furthermore, internal forces tend to resist this extension. Impedance tomography can show this imbalance to stimulate the stenosis of aortic valve, growth of the elastic, collagen and to effectively reduce the stresses in the underlying tissue. In blood flow, auscultation noises occurred and in the echocardiography decrease in left ventricular ejection speed can be observed. In this paper, we have modeled an aorta based on anatomical studies to simulate natural, 20% and 30% stenosis as usual heart disease to early diagnosis. Valve deformation causes different impedance tomography in 3D mesh of aorta as blood pressure. Remodeling of aorta and its flow is found when a cylindrical slice of the fully retracted blood aorta is cut longitudinally through the wall.

3D+time left ventricular strain by unwrapping harmonic phase with graph cuts

In previous work, a three-dimensional left ventricular strain throughout the cardiac cycle was reconstructed using a prolate spheroidal B-spline (PSB) method with displacement measurements obtained from unwrapped tagged MRI (tMRI) harmonic phase images. Manually placed branch cuts were required for each harmonic phase image to resolve phase inconsistencies and to guide the phase unwrapping (mSUP), which is both labor intensive and time consuming and therefore not proper for clinic application. In this paper, we present an automated graph cuts based phase unwrapping method for myocardium displacement measurement (caSUP) which can be used to compute 3D+time cardiac strain. A set of 8 human studies were used to optimize parameters of the energy function and another set of 32 human studies were used to validate the proposed method by comparing resulted strains with those from mSUP and a feature-based (FB) method using the same PSB strain reconstruction. The automated caSUP strains were close to the manual strains and only required 6 minutes after myocardium segmentation versus - 2 hours for the manual method.

Left ventricular twist and shear in patients with primary mitral regurgitation

PURPOSE

To evaluate the relationship between left ventricular (LV) twist, shear, and twist-per-volume and the severity of mitral regurgitation (MR). Primary MR is a valvular disorder that induces LV dysfunction. There exist several measures of LV rotational mechanics, but it remains unclear which measure of LV dysfunction best accords with the severity of MR. We hypothesized that LV systolic twist-per-volume slope would decrease with increasing severity of MR because of both decreases in rotational mechanics and increases in stroke volumes.

MATERIALS AND METHODS

Normal subjects (n = 54), moderate MR patients (n = 29), and severe MR patients (n = 54) were studied. Magnetic resonance imaging (MRI) was performed on a 1.5T scanner and grid-tagged LV images were collected at the LV base and LV apex. Measures of LV rotational mechanics were derived from tagged images using Fourier Analysis of STimulated echoes (FAST).

RESULTS

Peak systolic twist-per-volume slope was significantly different for all pairwise comparisons (P < 0.0001) and compared to normal subjects (-0.14 ± 0.05°/mL) was decreased in moderate MR (-0.12 ± 0.04°/mL) and further decreased in severe MR (-0.07 ± 0.03°/mL).

CONCLUSION

Peak systolic twist-per-volume slope significantly decreased with increasing severity of MR and is therefore a suitable quantitative imaging biomarker for LV dysfunction in patients with MR.

Left ventricular torsion shear angle volume analysis in patients with hypertension: a global approach for LV diastolic function

BACKGROUND

Torsion shear angle φ is an important measure of left ventricular (LV) systolic and diastolic functions. Here we provide a novel index utilizing LV normalized torsion shear angle φ ^ volume V ^ loop to assess LV diastolic functional properties. We defined the area within φ ^ V ^ loop as torsion hysteresis area, and hypothesized that it may be an important global parameter of diastolic function. We evaluated the φ ^ changes to increased V ^ during early diastole - d φ ^ / d V ^ as a potential measure of LV suction.

METHODS

Sixty resistant hypertension patients (HTN), forty control volunteers were studied using cardiovascular magnetic resonance with tissue tagging. Volumetric and torsional parameters were evaluated.

RESULTS

HTN demonstrated concentric remodeling with preserved ejection fraction. HTN had significantly decreased normalized early filling rate, early diastolic mitral annulus velocity and E/A (1.33 ± 1.13 vs. 2.19 ± 1.07, P < 0.0001) vs. control. Torsion hysteresis area was greater (0.11 ± 0.07 vs. 0.079 ± 0.045, P < 0.001) and peak - d φ ^ / d V ^ at early diastole was higher (10.46 ± 8.51 vs. 6.29 ± 3.85, P = 0.002) than control. Torsion hysteresis area was significantly correlated with E/A (r = -0.23, P = 0.025). Thirteen HTN patients had both E/A ratio < 1.12 (Control mean E/A-1SD) and torsion hysteresis area > 0.12 (Control mean torsion hysteresis area + 1SD).

CONCLUSIONS

Torsion hysteresis area and peak early diastolic - d φ ^ / d V ^ were significantly increased in hypertensive concentric remodeling. The φ ^ V ^ loop takes into account the active and passive recoil processes of LV diastolic and systolic phases, therefore provides a new global description of LV diastolic function.

Synthetic generation of myocardial blood-oxygen-level-dependent MRI time series via structural sparse decomposition modeling

This paper aims to identify approaches that generate appropriate synthetic data (computer generated) for cardiac phase-resolved blood-oxygen-level-dependent (CP-BOLD) MRI. CP-BOLD MRI is a new contrast agent- and stress-free approach for examining changes in myocardial oxygenation in response to coronary artery disease. However, since signal intensity changes are subtle, rapid visualization is not possible with the naked eye. Quantifying and visualizing the extent of disease relies on myocardial segmentation and registration to isolate the myocardium and establish temporal correspondences and ischemia detection algorithms to identify temporal differences in BOLD signal intensity patterns. If transmurality of the defect is of interest pixel-level analysis is necessary and thus a higher precision in registration is required. Such precision is currently not available affecting the design and performance of the ischemia detection algorithms. In this work, to enable algorithmic developments of ischemia detection irrespective to registration accuracy, we propose an approach that generates synthetic pixel-level myocardial time series. We do this by 1) modeling the temporal changes in BOLD signal intensity based on sparse multi-component dictionary learning, whereby segmentally derived myocardial time series are extracted from canine experimental data to learn the model; and 2) demonstrating the resemblance between real and synthetic time series for validation purposes. We envision that the proposed approach has the capacity to accelerate development of tools for ischemia detection while markedly reducing experimental costs so that cardiac BOLD MRI can be rapidly translated into the clinical arena for the noninvasive assessment of ischemic heart disease.

Increased sarcolipin expression and adrenergic drive in humans with preserved left ventricular ejection fraction and chronic isolated mitral regurgitation

BACKGROUND

There is currently no therapy proven to attenuate left ventricular (LV) dilatation and dysfunction in volume overload induced by isolated mitral regurgitation (MR). To better understand molecular signatures underlying isolated MR, we performed LV gene expression analyses and overlaid regulated genes into ingenuity pathway analysis in patients with isolated MR.

METHODS AND RESULTS

Gene arrays from LV tissue of 35 patients, taken at the time of surgical repair for isolated MR, were compared with 13 normal controls. Cine-MRI was performed in 31 patients before surgery to measure LV function and volume from serial short-axis summation. LV end-diastolic volume was 2-fold (P=0.005) higher in MR patients than in normal controls, and LV ejection fraction was 64±7% (50%-79%) in MR patients. Ingenuity pathway analysis identified significant activation of pathways involved in β-adrenergic, cAMP, and G-protein-coupled signaling, whereas there was downregulation of pathways associated with complement activation and acute phase response. SERCA2a and phospholamban protein were unchanged in MR versus control left ventricles. However, mRNA and protein levels of the sarcoplasmic reticulum Ca2+ ATPase (SERCA) regulatory protein sarcolipin, which is predominantly expressed in normal atria, were increased 12- and 6-fold, respectively. Immunofluorescence analysis confirmed the absence of sarcolipin in normal left ventricles and its marked upregulation in MR left ventricles.

CONCLUSIONS

These results demonstrate alterations in multiple pathways associated with β-adrenergic signaling and sarcolipin in the left ventricles of patients with isolated MR and LV ejection fraction>50%, suggesting a beneficial role for β-adrenergic blockade in isolated MR.

High-resolution cine MRI with TGRAPPA for fast assessment of left ventricular function at 3 Tesla

PURPOSE

To implement and evaluate the accuracy of multislice dual-breath hold cine MR for analysis of global systolic and diastolic left ventricular function at 3T.

MATERIALS AND METHODS

25 patients referred to cardiac MR underwent cine imaging at 3T (MAGNETOM Verio) using prospective triggered SSFP (TR 3.1 ms; TE 1.4 ms; FA 60°). Analysis of LV function was performed using a standard non-accelerated single-slice approach (STD) with multiple breath-holds and an accelerated multi-slice technique (TGRAPPA; R=4) encompassing the ventricles with 5 slices/breath-hold. Parameters of spatial and temporal resolution were kept identical (pixel: 1.9 × 2.5 mm(2); temporal resolution: 47 ms). Data of both acquisition techniques were analyzed by two readers using semiautomatic algorithms (syngoARGUS) with respect to EDV, ESV, EF, myocardial mass (MM), peak filling rate (PFR) and peak ejection rate (PER) including assessment of interobserver agreement.

RESULTS

Volumetric results of the TGRAPPA approach did not show significant differences to the STD approach for left ventricular ejection fraction (62.3 ± 10.6 vs. 61.0 ± 8.4, P=0.2), end-diastolic volume (135.8 ± 47.5 vs. 130.8 ± 46.4, P=0.07), endsystolic volume (53.0 ± 29.7 vs. 53.1 ± 32.7, P=0.99) and myocardial mass (114.2 ± 32.5 vs. 114.6±30.6, P=0.9). Moreover, a comparison of peak ejection rate (601.3 ± 190.2 vs. 590.8 ± 218.2, P=0.8) and peak filling rate (535.1±191.2 vs. 535.4 ± 210.7, P=0.99) did not reveal significant differences between the two groups. Limits in interobserver agreement were low for all systolic and diastolic parameters in both groups (P ≥ 0.05). Total acquisition time for STD was 273 ± 124 s and 34 ± 5 s for TGRAPPA (P ≤ 0.001). Evaluation time for standard and multislice approach was equal (10.8 ± 1.4 vs. 9.8 ± 2.1 min; P=0.08).

A randomized controlled phase IIb trial of beta(1)-receptor blockade for chronic degenerative mitral regurgitation

OBJECTIVES

The purpose of the study was to evaluate the effect of long-term β(1)-aderergic receptor (AR) blockade on left ventricular (LV) remodeling and function in patients with chronic, isolated, degenerative mitral regurgitation (MR).

BACKGROUND

Isolated MR currently has no proven therapy that attenuates LV remodeling or preserves systolic function.

METHODS

Thirty-eight asymptomatic subjects with moderate to severe, isolated MR were randomized either to placebo or β(1)-AR blockade (Toprol-XL, AstraZeneca, London, United Kingdom) for 2 years. Magnetic resonance imaging with tissue tagging and 3-dimensional analysis was performed at baseline and at 6-month intervals for 2 years. Rate of progression analysis was performed for endpoint variables for primary outcomes: LV end-diastolic volume/body surface area, LV ejection fraction, LV end-diastolic (ED) mass/ED volume ratio, LV ED 3-dimensional radius/wall thickness; LV end-systolic volume/body surface area, LV longitudinal strain rate, and LV early diastolic filling rate.

RESULTS

Baseline LV magnetic resonance imaging or demographic variables did not differ between the 2 groups. Significant treatment effects were found on LV ejection fraction (p = 0.006) and LV early diastolic filling rate (p = 0.001), which decreased over time in untreated patients on an intention-to-treat analysis and remained significant after sensitivity analysis. There were no significant treatment effects found on LV ED or LV end-systolic volumes, LV ED mass/LV ED volume or LV ED 3-dimensional radius/wall thickness, or LV longitudinal strain rate. Over 2 years, 6 patients treated in the placebo group and 2 patients in the β(1)-AR blockade group required mitral valve surgery (p = 0.23).

CONCLUSIONS

β(1)-AR blockade improves LV function over a 2-year follow-up in isolated MR and provides the impetus for a large-scale clinical trial with clinical outcomes. (Molecular Mechanisms of Volume Overload-Aim 1 [SCCOR in Cardiac Dysfunction and Disease]; NCT01052428).

Accurate computer-aided quantification of left ventricular parameters: experience in 1555 cardiac magnetic resonance studies from the Framingham Heart Study

Quantitative analysis of short-axis functional cardiac magnetic resonance images can be performed using automatic contour detection methods. The resulting myocardial contours must be reviewed and possibly corrected, which can be time-consuming, particularly when performed across all cardiac phases. We quantified the impact of manual contour corrections on both analysis time and quantitative measurements obtained from left ventricular short-axis cine images acquired from 1555 participants of the Framingham Heart Study Offspring cohort using computer-aided contour detection methods. The total analysis time for a single case was 7.6 ± 1.7 min for an average of 221 ± 36 myocardial contours per participant. This included 4.8 ± 1.6 min for manual contour correction of 2% of all automatically detected endocardial contours and 8% of all automatically detected epicardial contours. However, the impact of these corrections on global left ventricular parameters was limited, introducing differences of 0.4 ± 4.1 mL for end-diastolic volume, -0.3 ± 2.9 mL for end-systolic volume, 0.7 ± 3.1 mL for stroke volume, and 0.3 ± 1.8% for ejection fraction. We conclude that left ventricular functional parameters can be obtained under 5 min from short-axis functional cardiac magnetic resonance images using automatic contour detection methods. Manual correction more than doubles analysis time, with minimal impact on left ventricular volumes and ejection fraction.

Magnetic resonance imaging with 3-dimensional analysis of left ventricular remodeling in isolated mitral regurgitation: implications beyond dimensions

BACKGROUND

Although surgery is indicated in patients with mitral regurgitation (MR) when left ventricular (LV) end-systolic (LVES) dimension is >40 mm, LV ejection fraction may decrease after mitral valve surgery. We hypothesize that significant LV remodeling before surgery is not reflected by standard echocardiographic parameters measured at the base of the heart.

METHODS AND RESULTS

Ninety-four patients (age, 54 ± 11 years; 38% female) with degenerative isolated MR underwent cine magnetic resonance imaging with tissue tagging and 3-dimensional analysis. In 51 control subjects (age, 44 ± 14 years; 53% female), the relation between LVES volume (LVESV) and LVES dimension was quadratic, whereas in 94 MR patients, this relation was cubic, indicating a greater increase in LVESV per LVES dimension among MR patients. Moreover, magnetic resonance imaging LVESV from summated serial short-axis slices was significantly greater than LVESV assessed with the Bullet formula in MR patients, attributed to a more spherical remodeling distal to the tips of the papillary muscles (P<0.001). Thirty-five patients underwent mitral valve repair per current guideline recommendations. LV ejection fraction decreased from 61 ± 7% to 54 ± 8% (P<0.0001) and maximum shortening decreased significantly below normal at 1 year postoperatively (P<0.0001). Despite normalization of LV stroke volume and LV end-diastolic volume/mass ratio, there was a persistent significant increase in distal LVES 3-dimensional radius/wall thickness ratio and LVESV index after surgery.

CONCLUSIONS

Despite apparently preserved LVES dimension, MR patients demonstrate significant spherical mid to apical LVES remodeling that contributes to higher LVESV than predicted by standard geometry-based calculations. Decreased LV strain after surgery suggests that a volumetric analysis of LV remodeling and function may be preferred to evaluate disease progression in isolated MR.

Left ventricular remodeling in preclinical experimental mitral regurgitation of dogs

Dogs with experimental mitral regurgitation (MR) provide insights into the left ventricular remodeling in preclinical MR. The early preclinical left ventricular (LV) changes after mitral regurgitation represent progressive dysfunctional remodeling, in that no compensatory response returns the functional stroke volume (SV) to normal even as total SV increases. The gradual disease progression leads to mitral annulus stretch and enlargement of the regurgitant orifice, further increasing the regurgitant volume. Remodeling with loss of collagen weave and extracellular matrix (ECM) is accompanied by stretching and hypertrophy of the cross-sectional area and length of the cardiomyocyte. Isolated ventricular cardiomyocytes demonstrate dysfunction based on decreased cell shortening and reduced intracellular calcium transients before chamber enlargement or decreases in contractility in the whole heart can be clinically appreciated. The genetic response to increased end-diastolic pressure is down-regulation of genes associated with support of the collagen and ECM and up-regulation of genes associated with matrix remodeling. Experiments have not demonstrated any beneficial effects on remodeling from treatments that decrease afterload via blocking the renin-angiotensin system (RAS). Beta-1 receptor blockade and chymase inhibition have altered the progression of the LV remodeling and have supported cardiomyocyte function. The geometry of the LV during the remodeling provides insight into the importance of regional differences in responses to wall stress.

Review of journal of cardiovascular magnetic resonance 2010

There were 75 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2010, which is a 34% increase in the number of articles since 2009. The quality of the submissions continues to increase, and the editors were delighted with the recent announcement of the JCMR Impact Factor of 4.33 which showed a 90% increase since last year. Our acceptance rate is approximately 30%, but has been falling as the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. Last year for the first time, the Editors summarized the papers for the readership into broad areas of interest or theme, which we felt would be useful to practitioners of cardiovascular magnetic resonance (CMR) so that you could review areas of interest from the previous year in a single article in relation to each other and other recent JCMR articles 1. This experiment proved very popular with a very high rate of downloading, and therefore we intend to continue this review annually. The papers are presented in themes and comparison is drawn with previously published JCMR papers to identify the continuity of thought and publication in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication.

Comparison of left ventricular volumes and ejection fraction by monoplane cineventriculography, unenhanced echocardiography and cardiac magnetic resonance imaging

Right-anterior-oblique (RAO) monoplane cineventriculography is usually applied in cardiac catheter labs to assess the left ventricular (LV) function. However, it is uncertain whether this technique is reliable in clinical routine. Unenhanced two-dimensional echocardiography was reported to underestimate left ventricular volumes. The aim of this study was to compare these two conventional techniques with cardiac magnetic resonance imaging (MRI), the present gold standard for the determination of LV function, to evaluate whether the results from the conventional techniques are reliable and in accordance with each other. Seventy-two patients were retrospectively recruited and analysis of the three techniques was performed. Compared with MRI, RAO cineventriculography underestimated LV end-systolic volumes (ESV), and overestimated LV ejection fraction (EF); two-dimensional echocardiography underestimated LV end-diastolic volume (EDV) and EF. Correlation coefficients on EDV, ESV, and EF were 0.8806, 0.9201, and 0.8864 between echocardiography and MRI (P < 0.01, for all), followed by 0.7718, 0.8835, and 0.7785, between cineventriculography and MRI (P < 0.01, for all), and 0.7006, 0.7680, and 0.7644 between cineventriculography and echocardiography (P < 0.01, for all). Echocardiography and MRI showed the highest inter-technique correlation coefficients, and the narrowest Bland-Altman limits of agreement for EDV, ESV and EF. EDV, ESV and EF determined by RAO monoplane cineventriculography, unenhanced two-dimensional echocardiography and MRI were in high accordance with each other, with wide variances between the techniques. Although not interchangeable, RAO monoplane cineventriculography, unenhanced two-dimensional echocardiography, and cardiac MRI are reliable tools in clinical routine for the assessment of LV volumes and function.

Three-dimensional plus time biventricular strain from tagged MR images by phase-unwrapped harmonic phase

PURPOSE

To validate a method called bi-ventricular strain unwrapped phase (BiSUP) for reconstructing three-dimensional plus time (3D+t) biventricular strain maps from phase-unwrapped harmonic phase (HARP) images derived from tagged cardiac magnetic resonance imaging (MRI).

MATERIALS AND METHODS

A set of 30 human subjects were imaged with tagged MRI. In each study, HARP phase was computed and unwrapped in each short-axis and long-axis image. Inconsistencies in unwrapped phase were resolved using branch cuts manually placed with a graphical user interface. The 3D strain maps were computed independently in each imaged time frame through systole and mid diastole in each study. The BiSUP strain and displacements were compared with those estimated by a 3D feature-based (FB) technique and a 2D+t HARP technique.

RESULTS

The standard deviation of the difference between strains measured by the FB and the BiSUP methods was less than 4% of the average of the strains from the two methods. The correlation between peak minimum principal strain measured using the BiSUP and HARP techniques was over 83%.

CONCLUSION

The BiSUP technique can reconstruct full 3D+t strain maps from tagged MR images through the cardiac cycle in a reasonable amount of time and user interaction compared with other 3D analysis methods.

Chymase inhibition prevents fibronectin and myofibrillar loss and improves cardiomyocyte function and LV torsion angle in dogs with isolated mitral regurgitation

BACKGROUND

The left ventricular (LV) dilatation of isolated mitral regurgitation (MR) is associated with an increase in chymase and a decrease in interstitial collagen and extracellular matrix. In addition to profibrotic effects, chymase has significant antifibrotic actions because it activates matrix metalloproteinases and kallikrein and degrades fibronectin. Thus, we hypothesize that chymase inhibitor (CI) will attenuate extracellular matrix loss and LV remodeling in MR.

METHODS AND RESULTS

We studied dogs with 4 months of untreated MR (MR; n=9) or MR treated with CI (MR+CI; n=8). Cine MRI demonstrated a >40% increase in LV end-diastolic volume in both groups, consistent with a failure of CI to improve a 25% decrease in interstitial collagen in MR. However, LV cardiomyocyte fractional shortening was decreased in MR versus normal dogs (3.71±0.24% versus 4.81±0.31%; P<0.05) and normalized in MR+CI dogs (4.85±0.44%). MRI with tissue tagging demonstrated an increase in LV torsion angle in MR+CI versus MR dogs. CI normalized the significant decrease in fibronectin and FAK phosphorylation and prevented cardiomyocyte myofibrillar degeneration in MR dogs. In addition, total titin and its stiffer isoform were increased in the LV epicardium and paralleled the changes in fibronectin and FAK phosphorylation in MR+CI dogs.

CONCLUSIONS

These results suggest that chymase disrupts cell surface-fibronectin connections and FAK phosphorylation that can adversely affect cardiomyocyte myofibrillar structure and function. The greater effect of CI on epicardial versus endocardial titin and noncollagen cell surface proteins may be responsible for the increase in torsion angle in chronic MR.

Multi-modality imaging of diastolic function

Non-invasive evaluation of diastolic function continues to play a critical role in furthering our understanding of diastole, improving the diagnosis of diastolic dysfunction, evaluating left ventricular filling pressures, and providing important prognostic information for patients with heart failure. Echocardiography, cardiovascular magnetic resonance, and nuclear cardiology each provide important tools for evaluating diastolic performance. This review will focus on the techniques from multiple cardiovascular imaging modalities which have been used for the clinical assessment of diastolic function.

Review of Journal of Cardiovascular Magnetic Resonance 2009

There were 56 articles published in the Journal of Cardiovascular Magnetic Resonance in 2009. The editors were impressed with the high quality of the submissions, of which our acceptance rate was about 40%. In accordance with open-access publishing, the articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. We have therefore chosen to briefly summarise the papers in this article for quick reference for our readers in broad areas of interest, which we feel will be useful to practitioners of cardiovascular magnetic resonance (CMR). In some cases where it is considered useful, the articles are also put into the wider context with a short narrative and recent CMR references. It has been a privilege to serve as the Editor of the JCMR this past year. I hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication.