TrueFISP: assessment of accuracy for measurement of left ventricular mass in an animal model

Age- and gender-related reference values of cardiac morphology and function in cardiovascular magnetic resonance

Cardiovascular magnetic resonance (CMR) is the reference standard for the quantitative assessment of cardiac morphology and function. The aim of the study was to determine age- and gender-related reference values for cardiac morphology and function according to current recommendations. 454 healthy volunteers (235 men, median age 52.0 (44.0-59.0) years) underwent a standard CMR scan and were divided into six groups of nearly equal size with regard to sex (male, female) and age (21-47 years, 48-57 years, 58-84 years). Left ventricular end-diastolic (LV-EDV) and end-systolic (LV-ESV) volumes and LV mass (LV-M) were measured at end-diastole and end-systole in steady-state free precession series with including papillary muscles and trabecular tissue in the LV-M. Absolute and indexed volumetric parameters were significantly different between gender groups with higher values in men compared to women (all p < 0.001). Furthermore, a significant age-dependent decline could be observed for left ventricular and right ventricular volumes (all p < 0.001), while LV-M did not show differences between the different age-groups. Parameters of longitudinal function for the left and right ventricle were higher in female compared to male subjects with a significant age-dependent decline. We provided normal values for cardiac volumes, function, and mass derived in accordance with current guidelines from a large population of healthy subjects, which can be implemented in clinical routine as a standard of reference.

Echocardiography overestimates LV mass in the elderly as compared to cardiac CT

PURPOSE

Echocardiographic studies have shown an increase in LV mass with advanced age. However, autopsy and MRI studies demonstrate that with aging, LV mass is unchanged or slightly decreased, with a decrease in LV volume and an increase in wall thickness consistent with concentric remodeling. LV structural remodeling with aging may lead to an overestimation of LV mass in older adults when using standard echocardiography measurements and calculations. This study compared CT and echocardiographic LV mass calculation in younger and older patients and parameters associated with age-related LV remodeling.

METHODS

Same subject modality comparison of echocardiographic and cardiac CT LV measurement with derivation of LV mass was performed retrospectively. Echocardiographic measurements were performed by a single observer in accordance with European Association of Cardiovascular Imaging (EACI)/American Society of Echocardiography (ASE) guidelines. CT measurements were performed in end-diastole on multiplanar reformatted image planes corresponding to those typically used in echocardiography. Calculated CT measurements were based on automatic segmentation of heart chambers via edge-tracing algorithms.

RESULTS

129 patients were identified. In patients age 65 and older, LV mass was significantly higher when calculated using echocardiographic measurements compared to CT. Patients 65 years of age and older were found to have increased average wall thickness measurements with echocardiography but not with CT. The discrepancy between calculated echo and CT LV mass was reduced when using the mid-septal instead of proximal wall width for the EACI convention.

CONCLUSION

In the elderly, increased echo-derived LV mass may reflect remodeling rather than a true increase in LV mass.

Changes in Biomarker Profile and Left Ventricular Hypertrophy Regression: Results from the Frequent Hemodialysis Network Trials

BACKGROUND

Regression of left ventricular hypertrophy (LVH) is feasible with more frequent hemodialysis (HD). We aimed to ascertain pathways associated with regression of left ventricular mass (LVM) in patients enrolled in the Frequent HD Network (FHN) trials.

METHODS

This was a post hoc observational cohort study. We hypothesized LVH regression with frequent HD was associated with a different cardiovascular biomarker profile. Regressors were defined as patients who achieved a reduction of more than 10% in LVM at 12 months. Progressors were defined as patients who had a minimum of 10% increase in LVM at 12 months.

RESULTS

Among 332 randomized patients, 243 had biomarker data available. Of these, 121 patients did not progress or regress, 77 were regressors, and 45 were progressors. Mean LVM change differed between regressors and progressors by -65.6 (-74.0 to -57.2) g, p < 0.001. Regressors had a median (interquartile range) increase in dialysis frequency (from 3.0 [3.0-3.0] to 4.9 [3-5.7] per week, p = 0.001) and reductions in pre-dialysis systolic (from 149.0 [136.0-162.0] to 136.0 [123.0-152.0] mm Hg, p < 0.001) and diastolic (from 83.0 [71.0-91.0] to 76.0 [68.0-84.0] mm Hg, p < 0.001) blood pressures. Klotho levels increased in regressors versus progressors (76.9 [10.5-143.3] pg/mL, p = 0.024). Tissue inhibitors of metalloproteinase (TIMP)-2 levels fell in regressors compared to progressors (-7,853 [-14,653 to -1,052] pg/mL, p = 0.024). TIMP-1 and log (brain natriuretic -peptide [BNP]) levels also tended to fall in regressors. Changes in LVM correlated inversely with changes in klotho (r = -0.24, p = 0.014). -Conclusions: Markers of collagen turnover and changes in klotho levels are potential novel pathways associated with regression of LVH in the dialysis population, which will require further prospective validation.

Cardiovascular Imaging: The Past and the Future, Perspectives in Computed Tomography and Magnetic Resonance Imaging

Today's noninvasive imaging of the cardiovascular system has revolutionized the approach to various diseases and has substantially affected prognostic information. Cardiovascular magnetic resonance (MR) and computed tomographic (CT) imaging are at center stage of these approaches, although 5 decades ago, these technologies were unheard of. Both modalities had their inception in the 1970s with a primary focus on noncardiovascular applications. The technical development of the various decades, however, substantially pushed the envelope for cardiovascular MR and CT applications. Within the past 10-15 years, MR and CT technologies have pushed each other in cardiac applications; and without the "rival" modality, neither one would likely not have reached its potential today. This view on the history of MR and CT in the field of cardiovascular applications provides insight into the story of success of applications that once have been ideas only but are at prime time today.

Ex vivo cardiovascular magnetic resonance measurements of right and left ventricular mass compared with direct mass measurement in excised hearts after transplantation: a first human SSFP comparison

BACKGROUND

CMR is considered the 'gold standard' for non-invasive LV and RV mass quantitation. This information is solely based on gradient-recalled echo (GRE) sequences while contrast dependent on intrinsic T1/T2 characteristics potentially offers superior image contrast between blood and myocardium. This study aims, for the first time in humans, to validate the SSFP approach using explanted hearts obtained from heart transplant recipients. Our objective is establish the correlation between and to validate steady-state free precession (SSFP) derived LV and RV mass vs. autopsy mass of hearts from cardiac transplants patients.

METHODS

Over three-years, 58 explanted cardiomyopathy hearts were obtained immediately upon orthotopic heart transplantation from the OR. They were quickly cleaned, prepared and suspended in a saline-filled container and scanned ex vivo via SSFP-SA slices to define LV/RV mass. Using an automatic thresholding program, segmentation was achieved in combination with manual trimming (ATMT) of extraneous tissue incorporating 3D cardiac modeling performed by independent and blinded readers. The explanted hearts were then dissected with the ventricles surgically separated at the interventricular septum. Weights of the total heart not excluding papillary and trabecular myocardium, LV and RV were measured via high-fidelity scale. Linear regression and Bland-Altman plots were used to analyze the data. The intra-class correlation coefficient was used to assess intra-observer reliability.

RESULTS

Of the total of 58 explanted hearts, 3 (6%) were excluded due to poor image quality leaving 55 patients (94%) for the final analysis. Significant positive correlations were found between total 3D CMR mass (450 ± 111 g) and total pathology mass (445 ± 116 g; r = 0.99, p < 0.001) as well as 3D CMR measured LV mass (301 ± 93 g) and the pathology measured LV mass (313 ± 96 g; r = 0.95, p < 0.001). Strong positive correlations were demonstrated between the 3D CMR measured RV mass (149 ± 46 g) and the pathology measured RV mass (128 ± 40 g; r = 0.76, p < 0.001). The mean bias between 3D-CMR and pathology measures for total mass, LV mass and RV mass were: 3.0 g, -16 g and 19 g, respectively.

CONCLUSIONS

SSFP-CMR accurately determines total myocardial, LV and RV mass as compared to pathology weighed explanted hearts despite variable surgical removal of instrumentation (left and right ventricular assist devices, AICD and often apical core removals). Thus, this becomes the first-ever human CMR confirmation for SSFP now validating the distinction of 'gold standard'.

Geometry-independent inclusion of basal myocardium yields improved cardiac magnetic resonance agreement with echocardiography and necropsy quantified left-ventricular mass

OBJECTIVES

Left-ventricular mass (LVM) is widely used to guide clinical decision-making. Cardiac magnetic resonance (CMR) quantifies LVM by planimetry of contiguous short-axis images, an approach dependent on reader-selection of images to be contoured. Established methods have applied different binary cut-offs using circumferential extent of left-ventricular myocardium to define the basal left ventricle (LV), omitting images containing lesser fractions of left-ventricular myocardium. This study tested impact of basal slice variability on LVM quantification.

METHODS

CMR was performed in patients and laboratory animals. LVM was quantified with full inclusion of left-ventricular myocardium, and by established methods that use different cut-offs to define the left-ventricular basal-most slice: 50% circumferential myocardium at end diastole alone (ED50), 50% circumferential myocardium throughout both end diastole and end systole (EDS50).

RESULTS

One hundred and fifty patients and 10 lab animals were studied. Among patients, fully inclusive LVM (172.6±42.3g) was higher vs. ED50 (167.2±41.8g) and EDS50 (150.6±41.1g; both P<0.001). Methodological differences yielded discrepancies regarding proportion of patients meeting established criteria for left-ventricular hypertrophy and chamber dilation (P<0.05). Fully inclusive LVM yielded smaller differences with echocardiography (Δ=11.0±28.8g) than did ED50 (Δ=16.4±29.1g) and EDS50 (Δ=33.2±28.7g; both P<0.001). Among lab animals, ex-vivo left-ventricular weight (69.8±13.2g) was similar to LVM calculated using fully inclusive (70.1±13.5g, P=0.67) and ED50 (69.4±13.9g; P=0.70) methods, whereas EDS50 differed significantly (67.9±14.9g; P=0.04).

CONCLUSION

Established CMR methods that discordantly define the basal-most LV produce significant differences in calculated LVM. Fully inclusive quantification, rather than binary cut-offs that omit basal left-ventricular myocardium, yields smallest CMR discrepancy with echocardiography-measured LVM and non-significant differences with necropsy-measured left-ventricular weight.

Effects of daily hemodialysis on heart rate variability: results from the Frequent Hemodialysis Network (FHN) Daily Trial

BACKGROUND

End-stage renal disease is associated with reduced heart rate variability (HRV), components of which generally are associated with advanced age, diabetes mellitus and left ventricular hypertrophy. We hypothesized that daily in-center hemodialysis (HD) would increase HRV.

METHODS

The Frequent Hemodialysis Network (FHN) Daily Trial randomized 245 patients to receive 12 months of six versus three times per week in-center HD. Two hundred and seven patients had baseline Holter recordings. HRV measures were calculated from 24-h Holter electrocardiograms at both baseline and 12 months in 131 patients and included low-frequency power (LF, a measure of sympathetic modulation), high-frequency power (HF, a measure of parasympathetic modulation) and standard deviation (SD) of the R-R interval (SDNN, a measure of beat-to-beat variation).

RESULTS

Baseline to Month 12 change in LF was augmented by 50% [95% confidence interval (95% CI) 6.1-112%, P =0.022] and LF + HF was augmented by 40% (95% CI 3.3-88.4%, P = 0.03) in patients assigned to daily hemodialysis (DHD) compared with conventional HD. Changes in HF and SDNN were similar between the randomized groups. The effects of DHD on LF were attenuated by advanced age and diabetes mellitus (predefined subgroups). Changes in HF (r = -0.20, P = 0.02) and SDNN (r = -0.18, P = 0.04) were inversely associated with changes in left ventricular mass (LVM).

CONCLUSIONS

DHD increased the LF component of HRV. Reduction of LVM by DHD was associated with increased vagal modulation of heart rate (HF) and with increased beat-to-beat heart rate variation (SDNN), suggesting an important functional correlate to the structural effects of DHD on the heart in uremia.

Reproducibility of small animal cine and scar cardiac magnetic resonance imaging using a clinical 3.0 tesla system

Background

To evaluate the inter-study, inter-reader and intra-reader reproducibility of cardiac cine and scar imaging in rats using a clinical 3.0 Tesla magnetic resonance (MR) system.

Methods

Thirty-three adult rats (Sprague–Dawley) were imaged 24 hours after surgical occlusion of the left anterior descending coronary artery using a 3.0 Tesla clinical MR scanner (Philips Healthcare, Best, The Netherlands) equipped with a dedicated 70 mm solenoid receive-only coil. Left-ventricular (LV) volumes, mass, ejection fraction and amount of myocardial scar tissue were measured. Intra-and inter-observer reproducibility was assessed in all animals. In addition, repeat MR exams were performed in 6 randomly chosen rats within 24 hours to assess inter-study reproducibility.

Results

The MR imaging protocol was successfully completed in 32 (97%) animals. Bland-Altman analysis demonstrated high intra-reader reproducibility (mean bias%: LV end-diastolic volume (LVEDV), -1.7%; LV end-systolic volume (LVESV), -2.2%; LV ejection fraction (LVEF), 1.0%; LV mass, -2.7%; and scar mass, -1.2%) and high inter-reader reproducibility (mean bias%: LVEDV, 3.3%; LVESV, 6.2%; LVEF, -4.8%; LV mass, -1.9%; and scar mass, -1.8%). In addition, a high inter-study reproducibility was found (mean bias%: LVEDV, 0.1%; LVESV, -1.8%; LVEF, 1.0%; LV mass, -4.6%; and scar mass, -6.2%).

Conclusions

Cardiac MR imaging of rats yielded highly reproducible measurements of cardiac volumes/function and myocardial infarct size on a clinical 3.0 Tesla MR scanner system. Consequently, more widely available high field clinical MR scanners can be employed for small animal imaging of the heart e.g. when aiming at serial assessments during therapeutic intervention studies.

Effects of frequent hemodialysis on ventricular volumes and left ventricular remodeling

BACKGROUND AND OBJECTIVES

Higher left ventricular volume is associated with death in patients with ESRD. This work investigated the effects of frequent hemodialysis on ventricular volumes and left ventricular remodeling.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The Frequent Hemodialysis Network daily trial randomized 245 patients to 12 months of six times per week versus three times per week in-center hemodialysis; the Frequent Hemodialysis Network nocturnal trial randomized 87 patients to 12 months of six times per week nocturnal hemodialysis versus three times per week predominantly home-based hemodialysis. Left and right ventricular end systolic and diastolic volumes, left ventricular mass, and ejection fraction at baseline and end of the study were ascertained by cardiac magnetic resonance imaging. The ratio of left ventricular mass/left ventricular end diastolic volume was used as a surrogate marker of left ventricular remodeling. In each trial, the effect of frequent dialysis on left or right ventricular end diastolic volume was tested between predefined subgroups.

RESULTS

In the daily trial, frequent hemodialysis resulted in significant reductions in left ventricular end diastolic volume (-11.0% [95% confidence interval, -16.1% to -5.5%]), left ventricular end systolic volume (-14.8% [-22.7% to -6.2%]), right ventricular end diastolic volume (-11.6% [-19.0% to -3.6%]), and a trend for right ventricular end systolic volume (-11.3% [-21.4% to 0.1%]) compared with conventional therapy. The magnitude of reduction in left and right ventricular end diastolic volumes with frequent hemodialysis was accentuated among patients with residual urine output<100 ml/d (P value [interaction]=0.02). In the nocturnal trial, there were no significant changes in left or right ventricular volumes. The frequent dialysis interventions had no substantial effect on the ratio of left ventricular mass/left ventricular end diastolic volume in either trial.

CONCLUSIONS

Frequent in-center hemodialysis reduces left and right ventricular end systolic and diastolic ventricular volumes as well as left ventricular mass, but it does not affect left ventricular remodeling.

CMR reference values for left ventricular volumes, mass, and ejection fraction using computer-aided analysis: the Framingham Heart Study

PURPOSE

To determine sex-specific reference values for left ventricular (LV) volumes, mass, and ejection fraction (EF) in healthy adults using computer-aided analysis and to examine the effect of age on LV parameters.

MATERIALS AND METHODS

We examined data from 1494 members of the Framingham Heart Study Offspring cohort, obtained using short-axis stack cine SSFP CMR, identified a healthy reference group (without cardiovascular disease, hypertension, or LV wall motion abnormality) and determined sex-specific upper 95th percentile thresholds for LV volumes and mass, and lower 5th percentile thresholds for EF using computer-assisted border detection. In secondary analyses, we stratified participants by age-decade and tested for linear trend across age groups.

RESULTS

The reference group comprised 685 adults (423F; 61 ± 9 years). Men had greater LV volumes and mass, before and after indexation to common measures of body size (all P = 0.001). Women had greater EF (73 ± 6 versus 71 ± 6%; P = 0.0002). LV volumes decreased with greater age in both sexes, even after indexation. Indexed LV mass did not vary with age. LV EF and concentricity increased with greater age in both sexes.

CONCLUSION

We present CMR-derived LV reference values. There are significant age and sex differences in LV volumes, EF, and geometry, whereas mass differs between sexes but not age groups.

Cardiovascular magnetic resonance: deeper insights through bioengineering

Heart disease is the main cause of morbidity and mortality worldwide, with coronary artery disease, diabetes, and obesity being major contributing factors. Cardiovascular magnetic resonance (CMR) can provide a wealth of quantitative information on the performance of the heart, without risk to the patient. Quantitative analyses of these data can substantially augment the diagnostic quality of CMR examinations and can lead to more effective characterization of disease and quantification of treatment benefit. This review provides an overview of the current state of the art in CMR with particular regard to the quantification of motion, both microscopic and macroscopic, and the application of bioengineering analysis for the evaluation of cardiac mechanics. We discuss the current clinical practice and the likely advances in the next 5-10 years, as well as the ways in which clinical examinations can be augmented by bioengineering analysis of strain, compliance, and stress.

Correlation of trabeculae and papillary muscles with clinical and cardiac characteristics and impact on CMR measures of LV anatomy and function

OBJECTIVES

The goal of this study was to assess the relationship of left ventricular (LV) trabeculae and papillary muscles (TPM) with clinical characteristics in a community-based, free-living adult cohort and to determine the effect of TPM on quantitative measures of LV volume, mass, and ejection fraction (EF).

BACKGROUND

Hypertrabeculation has been associated with adverse cardiovascular events, but the distribution and clinical correlates of the volume and mass of the TPM in a normal left ventricle have not been well characterized.

METHODS

Short-axis cine cardiac magnetic resonance images, obtained using a steady-state free precession sequence from 1,494 members of the Framingham Heart Study Offspring cohort, were analyzed with software that automatically segments TPM. Absolute TPM volume, TPM as a fraction of end-diastolic volume (EDV) (TPM/EDV), and TPM mass as a fraction of LV mass were determined in all offspring and in a referent group of offspring free of clinical cardiovascular disease and hypertension.

RESULTS

In the referent group (mean age 61 ± 9 years; 262 men and 423 women), mean TPM was 23 ± 3% of LV EDV in both sexes (p = 0.9). TPM/EDV decreased with age (p < 0.02) but was not associated with body mass index. TPM mass as a fraction of LV mass was inversely correlated with age (p < 0.0001), body mass index (p < 0.018), and systolic blood pressure (p < 0.0001). Among all 1,494 participants (699 men), LV volumes decreased 23%, LV mass increased 28%, and EF increased by 7.5 EF units (p < 0.0001) when TPM were considered myocardial mass rather than part of the LV blood pool.

CONCLUSIONS

Global cardiac magnetic resonance LV parameters were significantly affected by whether TPM was considered as part of the LV blood pool or as part of LV mass. Our cross-sectional data from a healthy referent group of adults free of clinical cardiovascular disease demonstrated that TPM/EDV decreases with increasing age in both sexes but is not related to hypertension or obesity.

Determinants of left ventricular mass in patients on hemodialysis: Frequent Hemodialysis Network (FHN) Trials

BACKGROUND

An increase in left ventricular mass (LVM) is associated with mortality and cardiovascular morbidity in patients with end-stage renal disease.

METHODS AND RESULTS

The Frequent Hemodialysis Network (FHN) Daily Trial randomized 245 patients to 12 months of 6 times per week daily in-center hemodialysis or conventional hemodialysis; the FHN Nocturnal Trial randomized 87 patients to 12 months of 6 times per week nocturnal hemodialysis or conventional hemodialysis. The main cardiac secondary outcome was change in LVM. In each trial, we examined whether several predefined baseline demographic or clinical factors as well as change in volume removal, blood pressure, or solute clearance influenced the effect of frequent hemodialysis on LVM. In the Daily Trial, frequent hemodialysis resulted in a significant reduction in LVM (13.1 g; 95% CI, 5.0-21.3 g; P=0.002), LVM index (6.9 g/m(2); 95% CI, 2.4-11.3 g/m(2); P=0.003), and percent change in geometric mean of LVM (7.0%; 95% CI, 1.0%-12.6; P=0.02). Similar trends were noted in the Nocturnal Trial but did not reach statistical significance. In the Daily Trial, a more pronounced effect of frequent hemodialysis on LVM was evident among patients with left ventricular hypertrophy at baseline. Changes in LVM were associated with changes in blood pressure (conventional hemodialysis: R=0.28, P=0.01, daily hemodialysis: R=0.54, P<0.001) and were not significantly associated with changes in other parameters.

CONCLUSIONS

Frequent in-center hemodialysis reduces LVM. The benefit of frequent hemodialysis on LVM may be mediated by salutary effects on blood pressure. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT00264758.

Improved left ventricular mass quantification with partial voxel interpolation: in vivo and necropsy validation of a novel cardiac MRI segmentation algorithm

BACKGROUND

Cardiac magnetic resonance (CMR) typically quantifies LV mass (LVM) by means of manual planimetry (MP), but this approach is time-consuming and does not account for partial voxel components--myocardium admixed with blood in a single voxel. Automated segmentation (AS) can account for partial voxels, but this has not been used for LVM quantification. This study used automated CMR segmentation to test the influence of partial voxels on quantification of LVM.

METHODS AND RESULTS

LVM was quantified by AS and MP in 126 consecutive patients and 10 laboratory animals undergoing CMR. AS yielded both partial voxel (AS(PV)) and full voxel (AS(FV)) measurements. Methods were independently compared with LVM quantified on echocardiography (echo) and an ex vivo standard of LVM at necropsy. AS quantified LVM in all patients, yielding a 12-fold decrease in processing time versus MP (0:21±0:04 versus 4:18±1:02 minutes; P<0.001). AS(FV) mass (136±35 g) was slightly lower than MP (139±35; Δ=3±9 g, P<0.001). Both methods yielded similar proportions of patients with LV remodeling (P=0.73) and hypertrophy (P=1.00). Regarding partial voxel segmentation, AS(PV) yielded higher LVM (159±38 g) than MP (Δ=20±10 g) and AS(FV) (Δ=23±6 g, both P<0.001), corresponding to relative increases of 14% and 17%. In multivariable analysis, magnitude of difference between AS(PV) and AS(FV) correlated with larger voxel size (partial r=0.37, P<0.001) even after controlling for LV chamber volume (r=0.28, P=0.002) and total LVM (r=0.19, P=0.03). Among patients, AS(PV) yielded better agreement with echo (Δ=20±25 g) than did AS(FV) (Δ=43±24 g) or MP (Δ=40±22 g, both P<0.001). Among laboratory animals, AS(PV) and ex vivo results were similar (Δ=1±3 g, P=0.3), whereas AS(FV) (6±3 g, P<0.001) and MP (4±5 g, P=0.02) yielded small but significant differences with LVM at necropsy.

CONCLUSIONS

Automated segmentation of myocardial partial voxels yields a 14-17% increase in LVM versus full voxel segmentation, with increased differences correlated with lower spatial resolution. Partial voxel segmentation yields improved CMR agreement with echo and necropsy-verified LVM.

Several sources of error in estimation of left ventricular mass with M-mode echocardiography in elderly subjects

INTRODUCTION

M-mode echocardiography estimates of the left ventricular mass (LVM) were greater than magnetic resonance imaging (MRI) estimates. There are substantial differences between the methods both in the means of measuring and the calculation formula. The aim of this study was to investigate whether any difference in estimates of LVM between M-mode echocardiography and MRI is due to the means of measuring or to the calculation formula, using MRI as the gold standard.

MATERIAL AND METHODS

M-mode echocardiography and MRI were performed on 229 randomly selected 70-year-old community-living subjects. LVM was calculated from echocardiography (LVM(echo)) and from MRI (LVM(MRI)) measurements using standard techniques. Additionally LVM was calculated with the echocardiography formula from echo-mimicking measurements made on MR images (LVM(MRI/ASE)).

RESULTS

There were significant differences between all three LVM estimates in women, in men, and in the entire population. Echocardiography estimated LVM to be larger than did MRI, and the LVM(MRI/ASE) estimate was larger than the LVM(MRI). The difference between LVM(MRI) and LVM(MRI/ASE) was larger than the difference between LVM(echo) and LVM(MRI/ASE). There was a low correlation between LVM(echo) and LVM(MRI) (R(2) = 0.46) as well as between LVM(MRI/ASE) and LVM(MRI) (R(2) = 0.65).

CONCLUSION

The means of measuring and the calculation formula both independently add to the error in LVM estimation with M-mode echocardiography. The error of the calculation formula seems to be greater than the error of the means of measuring in a population of community-living elderly men and women.

Cardiac index is associated with brain aging: the Framingham Heart Study

BACKGROUND

Cardiac dysfunction is associated with neuroanatomic and neuropsychological changes in aging adults with prevalent cardiovascular disease, theoretically because systemic hypoperfusion disrupts cerebral perfusion, contributing to subclinical brain injury. We hypothesized that cardiac function, as measured by cardiac index, would be associated with preclinical brain magnetic resonance imaging (MRI) and neuropsychological markers of ischemia and Alzheimer disease in the community.

METHODS AND RESULTS

Brain MRI, cardiac MRI, neuropsychological, and laboratory data were collected on 1504 Framingham Offspring Cohort participants free of clinical stroke, transient ischemic attack, or dementia (age, 61+/-9 years; 54% women). Neuropsychological and brain MRI variables were related to cardiac MRI-assessed cardiac index (cardiac output/body surface area). In multivariable-adjusted models, cardiac index was positively related to total brain volume (P=0.03) and information processing speed (P=0.02) and inversely related to lateral ventricular volume (P=0.048). When participants with clinically prevalent cardiovascular disease were excluded, the relation between cardiac index and total brain volume remained (P=0.02). Post hoc comparisons revealed that participants in the bottom cardiac index tertile (values <2.54) and middle cardiac index tertile (values between 2.54 and 2.92) had significantly lower brain volumes (P=0.04) than participants in the top cardiac index tertile (values >2.92).

CONCLUSIONS

Although observational data cannot establish causality, our findings are consistent with the hypothesis that decreasing cardiac function, even at normal cardiac index levels, is associated with accelerated brain aging.

Left ventricular trabeculae: quantification in different cardiac diseases and impact on left ventricular morphological and functional parameters assessed with cardiac magnetic resonance

OBJECTIVES

Left ventricle trabeculae (LVT) are frequently seen in different cardiac diseases. Normal reference values of LVT in different cardiac conditions are not known. The aim of the study was to quantify with cardiac magnetic resonance (CMR), LVT mass (LVTM) and LVTM percentage (LVTM%) in different heart diseases and to evaluate their influence on left ventricular morphological and functional parameters.

METHODS

Fifty-nine patients (14 controls, 17 ischemic cardiomyopathy, 15 nonischemic dilated cardiomyopathy, 7 valvular heart disease and 6 with left ventricle hypertrophy) were enrolled. Cine-MR images were acquired with steady-state free-precession sequence in a short-axis view. LVTM was calculated as the difference between LVM excluding/including trabecuale from the blood cavity. LVTM% was calculated as the percentage of the whole left ventricle mass excluding trabeculae from the blood cavity.

RESULTS

Mean age was 47.60 +/- 22.03 years; male 62.7%. Mean LVTM was of 33.38 +/- 16.1 g with mean LVTM% of 19.22 +/- 6.5%. Significant differences between groups for both parameters with P values of 0.02 were obtained. Nonischemic dilated cardiomyopathy showed the highest degree of LVTM (44.73 +/- 16.0 g) and LVTM% (23.26 +/- 6%). Significant differences were noted in left ventricular morphological and functional parameters with inclusion/exclusion of LVT in the myocardial mass.

CONCLUSIONS

Reference values and differences of LVTM and LVTM% in various cardiac conditions are given for the first time. Quantification of these parameters with CMR may be clinically useful in the differential diagnosis between left ventricular noncompaction and other cardiac diseases. Exclusion of LVT from myocardium alters left ventricular morphological and functional parameters, which have significant clinical importance.

Left ventricular mass and volume with telmisartan, ramipril, or combination in patients with previous atherosclerotic events or with diabetes mellitus (from the ONgoing Telmisartan Alone and in Combination With Ramipril Global Endpoint Trial [ONTARGET])

The ONgoing Telmisartan Alone and in combination with Ramipril Global Endpoint Trial (ONTARGET) showed that the angiotensin receptor blocker telmisartan 80 mg was not inferior to the angiotensin-converting enzyme inhibitor ramipril 10 mg, and the combination no more effective than ramipril alone, in decreasing morbidity and mortality in patients with cardiovascular disease or high-risk diabetes. Although therapy targeting angiotensin II is known to decrease left ventricular (LV) mass and volume, the relative influence of angiotensin-converting enzyme inhibitor inhibitors and angiotensin receptor blocker, and their combination, on the heart remains unclear in this population. Magnetic resonance imaging was performed in 287 patients enrolled in ONTARGET, across 8 centers in 6 countries, at randomization and after 2-year treatment (90, 100, and 97 patients in the ramipril, telmisartan, and combination therapy groups, respectively). Baseline patient characteristics showed higher frequencies of coronary artery disease, Asian ethnicity, and use of statins and beta blockers than the main ONTARGET trial. LV mass decreased in all groups (p <0.0001 for each), but there were no significant differences in change in LV mass or volume among groups, except that LV mass index decreased more on combination versus telmisartan (p = 0.04). Key determinants of LV mass decrease were a history of hypertension (p = 0.03), baseline mass (p <0.0001), and decrease in systolic blood pressure (p <0.0001). The best magnetic resonance imaging predictor of composite events was end-systolic volume (p <0.0001). In conclusion, telmisartan and ramipril had similar effects on LV mass and volume, and combination therapy was not more effective, in high-risk patients with cardiovascular disease. These results are consistent with the major outcome findings of the main ONTARGET study.

Advances in Cardiovascular MRI for Diagnostics: Applications in Coronary Artery Disease and Cardiomyopathies

BACKGROUND: Cardiac magnetic resonance (CMR) imaging has emerged as an important cardiac imaging technique for the evaluation of multiple cardiac pathologies. OBJECTIVE/METHOD: The goal of this review is to describe recent advances in techniques which have extended the potential applications of CMR. The focus will be on the clinical applications of CMR for the evaluation of coronary artery disease and heart failure/cardiomyopathies which are major causes of morbidity and mortality worldwide. CONCLUSION: CMR provides unique tissue characterization which is not available from other imaging modalities and has demonstrated important diagnostic and prognostic information in many forms of heart disease.

Rationale and design for the Defibrillators to Reduce Risk by Magnetic Resonance Imaging Evaluation (DETERMINE) trial

BACKGROUND

Cardiac magnetic resonance imaging (CMR) can accurately determine infarct size. Prior studies using indirect methods and CMR to assess infarct size have shown that patients with larger myocardial infarctions have worse prognoses. Implantable cardioverter defibrillators (ICD) have been shown to improve survival among patients with severe left ventricular (LV) dysfunction. However, the majority of cardiac arrests occur in patients with higher ejection fractions.

METHODS

The Defibrillators To Reduce Risk By Magnetic Resonance Imaging Evaluation study (DETERMINE) is a prospective, multicenter, randomized, clinical trial in patients with coronary artery disease (CAD) and mild-to-moderate LV dysfunction. The purpose of this trial is to test the hypothesis that patients with an infarct size > or = 10% of LV mass, randomized to ICD plus appropriate medical therapy will have improved survival compared with patients randomized to medical therapy alone. Cine and myocardial delayed contrast CMR will be performed in patients with CAD. The primary endpoint will be death from any cause. At least 10,000 patients with CAD will undergo CMR. The target enrollment is 1,550 patients with an estimated 36-month enrollment period. The patients will be followed up for 24 months after the last patient randomization. During the follow-up period, 330 deaths are estimated to occur. This study is powered to detect a 28% reduction in mortality by ICD therapy.

CONCLUSION

The DETERMINE trial will assess the efficacy of ICD therapy to improve survival among patients with CAD, mild-to-moderate LV dysfunction, and infarct size > or = 10% of LV mass as measured by CMR.

Guiding automated left ventricular chamber segmentation in cardiac imaging using the concept of conserved myocardial volume

The active surface technique using gradient vector flow allows semi-automated segmentation of ventricular borders. The accuracy of the algorithm depends on the optimal selection of several key parameters. We investigated the use of conservation of myocardial volume for quantitative assessment of each of these parameters using synthetic and in vivo data. We predicted that for a given set of model parameters, strong conservation of volume would correlate with accurate segmentation. The metric was most useful when applied to the gradient vector field weighting and temporal step-size parameters, but less effective in guiding an optimal choice of the active surface tension and rigidity parameters.

Effects of papillary muscles and trabeculae on left ventricular quantification: increased impact of methodological variability in patients with left ventricular hypertrophy

BACKGROUND

Accurate quantification of left ventricular mass and ejection fraction is important for patients with left ventricular hypertrophy. Although cardiac magnetic resonance imaging has been proposed as a standard for these indices, prior studies have variably included papillary muscles and trabeculae in myocardial volume. This study investigated the contribution of papillary muscles and trabeculae to left ventricular quantification in relation to the presence and pattern of hypertrophy.

METHODS

Cardiac magnetic resonance quantification was performed on patients with concentric or eccentric hypertrophy and normal controls (20 per group) using two established methods that included papillary muscles and trabeculae in myocardium (method 1) or intracavitary (method 2) volumes.

RESULTS

Among all patients, papillary muscles and trabeculae accounted for 10.5% of ventricular mass, with greater contribution with left ventricular hypertrophy than normals (12.6 vs. 6.2%, P < 0.001). Papillary muscles and trabeculae mass correlated with ventricular wall mass (r = 0.53) and end-diastolic volume (r = 0.52; P < 0.001). Papillary muscles and trabeculae inclusion in myocardium (method 1) yielded smaller differences with a standard of mass quantification from linear ventricular measurements than did method 2 (P < 0.001). Method 1 in comparison with method 2 yielded differences in left ventricular mass, ejection fraction and volume in all groups, especially in patients with hypertrophy: the difference in ventricular mass index was three-fold to six-fold greater in hypertrophy than normal groups (P < 0.001). Difference in ejection fraction, greatest in concentric hypertrophy (P < 0.001), was independently related to papillary muscles and trabeculae mass, ventricular wall mass, and smaller ventricular volume (R = 0.56, P < 0.001).

CONCLUSION

Established cardiac magnetic resonance methods yield differences in left ventricular quantification due to variable exclusion of papillary muscles and trabeculae from myocardium. The relative impact of papillary muscles and trabeculae exclusion on calculated mass and ejection fraction is increased among patients with hypertrophy-associated left ventricular remodeling.

Left ventricular papillary muscles and trabeculae are significant determinants of cardiac MRI volumetric measurements: Effects on clinical standards in patients with advanced systolic dysfunction

BACKGROUND

Left ventricular (LV) mass and ejection fraction are of diagnostic and therapeutic importance in patients with systolic dysfunction. Cardiac MRI (CMR) has been proposed as a standard for these indices. Prior studies have variably included papillary muscles and trabeculae in either intracavitary or myocardial volumes. Quantitative effects and clinical implications of this methodological difference in patients with systolic dysfunction are unknown.

METHODS

Fifty consecutive patients with known systolic dysfunction (EF<40%) underwent CMR. LV volumes were determined using previously established methods: Method 1 included papillary muscles and trabeculae in cavity volume, method 2 included these in myocardial volume. Both methods were used for each patient with tracings superimposed to isolate papillary/trabecular volume and insure consistency of other endocardial contours. Readers applied methods in random order blinded to clinical findings and results of the other method.

RESULTS

LV mass differed substantially by method (p<0.001) with absolute difference of 16.6%. Ejection fraction differed by 3 points (p<0.001) with absolute differences of > or =5 points in 16% of patients. Mean differences in LV mass and ejection fraction were produced by consistent methodological differences on a per-patient basis. Methodology used produced differences in patients meeting established criteria for LV hypertrophy (28% vs. 60%, p<0.001) and ICD implantation (64% vs. 48%, p<0.01).

CONCLUSIONS

LV mass and ejection fraction differ significantly between commonly employed CMR methods. Alternative inclusion of papillary muscles and trabeculae in either cavity or myocardial volumes produces significant differences in clinical and therapeutic indices that can affect management of patients with advanced systolic dysfunction.

Feasibility of single breath-hold left ventricular function with 3 Tesla TSENSE acquisition and 3D modeling analysis

BACKGROUND

A single breath-hold evaluation of ventricular function would allow assessment in cases where scan time or patient tolerance is limited. Spatiotemporal acceleration techniques such as TSENSE decrease cardiovascular MR acquisition time, but standard slice summation analysis requires enough short axis slices to cover the left ventricle (LV). By reducing the number of short axis slices, incorporating long axis slices, and applying a 3D model based analysis, it may be possible to obtain accurate LV mass and volumes. We evaluated LV volume, mass and ejection fraction at 3.0 T using a 3D modeling analysis in 9 patients with a history of myocardial infarction and one healthy volunteer. Acquisition consisted of a standard short axis SSFP stack and a 15 heart-beat single breath-hold six slice multi-planar (4 short and 2 long axis) TSENSE SSFP protocol with an acceleration factor of R = 4.

RESULTS

Differences (standard minus accelerated protocol mean +/- s.d.) and coefficients of variation (s.d. of differences as a percentage of the average estimate) were 7.5 +/- 9.6 mL and 6% for end-diastolic volume (p = 0.035), 0.4 +/- 5.1 mL and 7% for end-systolic volume (p = NS), 7.1 +/- 8.1 mL and 9% for stroke volume (p = 0.022), 2.2 +/- 2.8% and 5% for ejection fraction (p = 0.035), and -7.1 +/- 6.2 g and 4% for LV mass (p = 0.005), respectively. Intra- and inter-observer errors were similar for both protocols (p = NS for all measures).

CONCLUSION

These results suggest that clinically useful estimates of LV function can be obtained in a TSENSE accelerated single breath-hold reduced slice acquisition at 3T using 3D modeling analysis techniques.

Cardiac MRI assessment of left and right ventricular parameters in healthy Australian normal volunteers

Cardiac magnetic resonance imaging (MRI) is being utilised increasingly for the purposes of cardiovascular imaging. Limited data suggest a high degree of reproducibility for parameters such as left ventricular (LV) ejection fraction (EF), mass, end-diastolic and end-systolic volumes (EDV and ESV). We sought to investigate reproducibility and establish means for these parameters in a selected normal non-Aboriginal Australian population, using cardiac MRI. Sixty normal volunteers underwent cardiac MRI investigation using a 1.5 T MRI system. Steady state free precession imaging was performed with short axis cine images through the left ventricle obtained. All images were acquired with cardiac gating. Two independent observers then analysed the data set. Data were collected for assessment of left ventricular EF, EDV, ESV, mass and right ventricular volumes. Data are presented as mean+/-S.D. Total imaging time was approximately 15 min. All patients were able to complete the full protocol. Left ventricular parameters: EF 58.5+/-8.0%, LV mass 114.2+/-40.6g, EDV 117.3+/-33.4 mls and ESV 50.0+/-22.2 mls. Right ventricular parameters: EF 45.6+/-11.6%, EDV 163.5+/-52.2 mls and ESV 89.5+/-34.3 mls. Intraclass correlation coefficients for LV: EF 0.84, LV mass 0.84, EDV 0.85 and ESV 0.89. Cardiac MRI provides high quality information about cardiac function with a high level of reproducibility. Cardiac MRI parameters in a normal non-Aboriginal Australian population are provided.

Relationship between central sympathetic drive and magnetic resonance imaging-determined left ventricular mass in essential hypertension

BACKGROUND

Sympathetic activation has been implicated in the development of left ventricular hypertrophy (LVH). However, the relationship between sympathetic activation and LV mass (LVM) has not been clearly defined across a range of arterial pressure measurements. The present study was planned to determine that relationship, using cardiac magnetic resonance imaging to accurately quantify LVM, in hypertensive patients with and without LVH and in normal subjects.

METHODS AND RESULTS

Twenty-four patients with uncomplicated and untreated essential hypertension (LVH[-]) were compared with 25 patients with essential hypertension and left ventricular hypertrophy (LVH[+]) and 24 normal control subjects. Resting muscle sympathetic nerve activity was quantified as multiunit bursts and single units. Cardiac magnetic resonance imaging-determined LVM was indexed to body surface area (LVM index); in the LVH[-] group, LVM index was 67+/-2.1 g/m2, a value between those of the LVH[+] (91+/-3.4 g/m2) and normal control (57+/-2.2 g/m2) groups, respectively. The sympathetic activity in the LVH[-] group (53+/-1.3 bursts per 100 cardiac beats and 63+/-1.6 impulses per 100 cardiac beats) was between (at least P<0.001) those of the LVH[+] (66+/-1.7 bursts per 100 cardiac beats and 77+/-2.2 impulses per 100 cardiac beats) and normal control (39+/-3.0 bursts per 100 cardiac beats and 45+/-3.4 impulses per 100 cardiac beats) groups. Significant positive correlation existed between sympathetic activity and LVM index in the LVH[-] and LVH[+] groups (at least r=0.76, P<0.0001) but not in the normal control group. However, no consistent relationship existed between arterial blood pressure and sympathetic activity or LVM index.

CONCLUSIONS

These findings further support the hypothesis that central sympathetic activation is associated with the development of LVH in human hypertension.

Effects of steady state free precession parameters on cardiac mass, function, and volumes

PURPOSE

We aimed to investigate comparability of LV volumes, function, and mass acquired with three steady-state free precession (SSFP) pulse sequences, simulating typical vendor and protocol specific differences in data acquisition.

METHODS

Twenty-one healthy subjects (11 male and 10 female; age range 23-49) underwent cardiac magnetic resonance (CMR) imaging at 1.5 Tesla (T). A complete stack of short-axis views covering the entire left ventricle (LV) were acquired for each of the three SSFP sequences, differing in the interslice gap and slice thickness (7 mm with no gap (7/0 mm); 7 mm with a 3 mm gap (7/3 mm) and 6 mm with a 4 mm gap (6/4 mm)) with slight variations in acquisition parameters. For each sequence, the LV volumes, function, and mass were determined. Intra- and inter-observer variability and inter-study reproducibility were assessed for all protocols.

RESULTS

All LV volumes, function and mass parameters were similar for the three SSFP sequences (P > 0.05 for all). The LV ejection fraction for the 7/3 mm sequence was 67.2 +/- 6.0, 67.4 +/- 5.3 for the 7/0 mm sequence, and the 6/4 mm sequence was 69.2 +/- 5.7. The LV mass ranged from 119.8 +/- 32.4 for the 7/3 mm sequence to 122.2 +/- 34.0 for the 7/0 mm sequence. Variabilities were low with no difference in variability between the sequences.

CONCLUSION

The three SSFP pulse sequence techniques resulted in similar LV volume, function, and mass measurements with no difference in observer and interstudy variabilities. This may allow application and transfer of LV volume studies and databases based on different imaging parameters, at different CMR sites, with a given post-processing method. Future multi-centre studies may now be in a position to consider multi-vendor study designs for LV volume studies.

Fast 3D cine steady-state free precession imaging with sensitivity encoding for assessment of left ventricular function in a single breath-hold

OBJECTIVE

This study compares single breath-hold 3D cine steady-state free precession (SSFP) MRI using sensitivity encoding (SENSE) with standard 2D cine SSFP imaging in the quantitative evaluation of global left ventricular (LV) function.

MATERIALS AND METHODS

The LV function of 22 healthy volunteers and 15 patients was evaluated using a standard 2D SSFP sequence and a 3D SSFP sequence with SENSE at 1.5 T. Ventricular volume, ejection fraction, and LV mass were calculated with each method, and signal-to-noise ratios (SNRs) and myocardium-to-blood contrast-to-noise ratios (CNRs) were measured. Agreement between the two methods was assessed using Bland-Altman analysis, and results were compared using a paired Student's t test (p < 0.05). The local institutional review board approved the study protocol, and all participants gave signed informed consent. The study complied with the Health Insurance Portability and Accountability Act.

RESULTS

Both techniques produced similar estimates of ejection fraction (mean bias +/- SD, -1.2% +/- 3.6%) and LV mass (mean bias, +/- SD-1.2 +/- 10.9 g). No significant differences were found in calculated volumes, ejection fraction, or LV mass between the two methods. Acquisition time was reduced by 82%, to a single breath-hold (18 +/- 3 seconds), with the 3D SSFP technique. SNR and CNR were significantly lower with the 3D method than with the standard method.

CONCLUSION

Three-dimensional SSFP imaging with SENSE can reduce acquisition time to a single breath-hold and can provide LV function quantification comparable to that obtained with conventional 2D SSFP imaging.

MR Imaging with Remote Control: Feasibility Study in Cardiovascular Disease

The institutional review board approved this HIPAA-compliant study and waived informed consent. The purpose was to retrospectively evaluate remote control magnetic resonance (MR) imaging in complex cardiovascular procedures, whereby operational expertise was made available locally from a remote location. Thirty patients underwent cardiac (12 patients) and/or vascular (30 patients) 1.5-T MR imaging with a remote operator by using a personal computer. All patient studies were compared with 30 control studies obtained with conventional local imaging. Cardiac cine, myocardial delayed enhancement, and MR angiograms were assessed for overall image quality and motion artifact. MR angiograms were evaluated for vascular definition. Image quality was excellent in 90% (38 of 42) of remote images versus 60% (25 of 42) of control group images (P < .01). Scores for motion artifact were not significantly different (P = .11). Interactive MR imaging was successfully implemented with remote control in complex cardiovascular cases; diagnostic quality of images was superior to that of images obtained locally.

Determination of cardiac volumes and mass with FLASH and SSFP cine sequences at 1.5 vs. 3 Tesla: a validation study

PURPOSE

To compare cardiac cine MR imaging using steady state free precession (SSFP) and fast low angle shot (FLASH) techniques at 1.5 and 3 T, and to establish their variabilities and reproducibilities for cardiac volume and mass determination in volunteers. To assess the feasibility of SSFP imaging in patients at 3 T and to determine comparability to volume data acquired at 1.5 T.

MATERIALS AND METHODS

Ten healthy volunteers underwent cardiac magnetic resonance imaging using SSFP and segmented gradient-echo FLASH, using both a 1.5 and a 3 T MR system on the same day. Ten patients with impaired left ventricular (LV) function were also studied at both field strengths with SSFP.

RESULTS

For both SSFP and FLASH, field strength had no effect on the quantification of LV and right ventricular (RV) volumes, mass, or function (P > or = 0.05 for field strength for all parameters). At both 1.5 and 3 T, SSFP yielded smaller LV mass (e.g., at 3 T 109 +/- 30 g vs. 142 +/- 37 g; P = 0.011) and larger LV volume (e.g., at 3 T end-diastolic volume 149 +/- 37 mL vs. 133 +/- 31 mL at 5 T; P = 0.041) measurements than FLASH. In patients with reduced LV function, all volume and mass measurements were again similar for SSFP sequences at 1.5 vs. 3 T. In volunteers and patients, measurement variabilities for LV parameters were small for both field strength and sequences, ranging between 3.7% and 10.7% for mass.

CONCLUSION

Compared to 1.5 T, cardiac cine MR imaging at 3 T, using either FLASH or SSFP sequences, is feasible and highly reproducible. Field strength does not have an influence on quantification of cardiac volume or mass, but the systematic overestimation of LV mass and underestimation of LV volume by FLASH compared to SSFP is present at both 1.5 and 3 T. Normal values for cardiac volumes and mass established at 1.5 T can be applied to scans obtained at 3 T.

Left Ventricular Papillary Muscle Mass

OBJECTIVE

To evaluate the effect of papillary muscle mass on the calculation of left ventricular (LV) function and mass and to determine the relationship between papillary muscle mass with body size and sex.

METHODS

Cardiac magnetic resonance imaging examinations from 50 men and 50 women were randomly selected from the Multi-Ethnic Study of Atherosclerosis database. The contours of the papillary muscles were traced manually, and the LV wall contours were outlined semiautomatically based on short-axis images. Papillary muscle mass, LV mass, and volumes were calculated.

RESULTS

Inclusion of the papillary muscles results in significantly higher total LV mass values (P<0.001) and lower end-diastolic volume values (P<0.001) compared with measurements excluding papillary muscles from the LV mass. Papillary muscle mass accounts for 8.9% of the total LV mass and is correlated with LV wall mass (r=0.81, P<0.001).

CONCLUSION

Papillary muscle mass significantly affects LV volumes and mass determined by cine magnetic resonance imaging.

Dual breath-hold magnetic resonance cine evaluation of global and regional cardiac function

The purpose of our study was to evaluate the accuracy of a multislice cine magnetic resonance imaging (MRI) technique with parallel imaging in regard to global and regional left ventricular function. Forty-two individuals underwent cine MRI on a 1.5-tesla scanner. Cine MRI used a steady-state free precession technique and was performed as a single-slice technique (nonTSENSE cine) and an accelerated multislice technique (TSENSE cine) with five slices per breath-hold. End diastolic volume (EDV), end systolic volume (ESV), and ejection fraction (EF) were evaluated for all data sets and in regard to regional wall motion and regional wall motion analysis, and quantitative regional wall thickness and systolic thickening were also assessed. EDV, ESV, and EF based on TSENSE cine showed excellent correlation to the nonTSENSE cine approach (all r(2)=0.99, P<0.001). While EDV evaluations showed a small underestimation for TSENSE cine, ESV and EF showed accurate results compared with nonTSENSE cine. Both readers showed good agreement (kappa=0.72) in regional wall motion assessment comparing both techniques. Data acquisition for the multislice approach was significantly shorter ( approximately 75%) that in single-slice cine. We conclude that accurate evaluation of regional wall motion and left ventricular EF is possible using accelerated multislice cine MR with high spatial and temporal resolution.

Non-Invasive Cardiac Evaluation in Heart Failure Patients Using Magnetic Resonance Imaging: A Feasibility Study

BACKGROUND

To assess the feasibility of a fast, flow-insensitive magnetic resonance imaging (MRI) protocol in heart failure patients for the evaluation of cardiac function, cardiovascular anatomy, and myocardial viability.

METHODS AND RESULTS

Thirty-two consecutive patients with left ventricular (LV) systolic dysfunction and 13 control subjects were prospectively evaluated with MRI. The exam consisted of cine imaging with a steady-state free precession sequence, followed by time-resolved, three-dimensional angiography and delayed, contrast-enhanced imaging. Multiple LV parameters were evaluated, and the heart failure and control results were compared. In 12 patients, MRI-determined ejection fractions were compared to echocardiographic values. Additionally, a qualitative analysis of the cine images was performed. The cardiac MR evaluation yielded diagnostic-quality images in all subjects. Mean imaging time was 37 min. MRI demonstrated significant differences between the heart failure and control subjects in all parameters assessed (p < 0.05). MRI-determined ejection fractions correlated strongly with echocardiographic values (R = 0.75), although the limits of agreement were wide (-17.3%-18.3%).

CONCLUSIONS

Using fast, flow-insensitive imaging techniques, MRI is feasible in heart failure for the derivation of more independent indices of cardiac status than any other non-invasive test. Although further investigation is warranted, MRI may prove uniquely helpful in heart failure diagnosis and management.

Establishing a clinical cardiac MRI service

After several years of research development cardiovascular MRI has evolved into a widely accepted clinical tool. It offers important diagnostic and prognostic information for a variety of clinical indications, which include ischaemic heart disease, cardiomyopathies, valvular dysfunction and congenital heart disorders. It is a safe non-invasive technique that employs a variety of imaging sequences optimized for temporal or spatial resolution, tissue-specific contrast, flow quantification or angiography. Cardiac MRI offers specific advantages over conventional imaging techniques for a significant number of patients. The demand for cardiac MRI studies from cardiothoracic surgeons, cardiologists and other referrers is likely to continue to rise with pressure for more widespread local service provision. Setting up a cardiac MRI service requires careful consideration regarding funding issues and how it will be integrated with existing service provision. The purchase of cardiac phased array coils, monitoring equipment and software upgrades must also be considered, as well as the training needs of those involved. The choice of appropriate imaging protocols will be guided by operator experience, clinical indication and equipment capability, and is likely to evolve as the service develops. Post-processing and offline analysis form a significant part of the time taken to report studies and an efficient method of providing quantitative reports is an important requirement. Collaboration between radiologists and cardiologists is needed to develop a successful service and multi-disciplinary meetings are key component of this. This review will explore these issues from our perspective of a new clinical cardiac MRI service operating over its first year in a teaching hospital imaging department.

Myocardial first pass perfusion: steady-state free precession versus spoiled gradient echo and segmented echo planar imaging

The imaging sequences used in first pass (FP) perfusion to date have important limitations in contrast-to-noise ratio (CNR), temporal and spatial resolution, and myocardial coverage. As a result, controversy exists about optimal imaging strategies for FP myocardial perfusion. Since imaging performance varies from subject to subject, it is difficult to form conclusions without direct comparison of different sequences in the same subject. The purpose of this study was to directly compare the saturation recovery SSFP technique to other more commonly used myocardial first pass perfusion techniques, namely spoiled GRE and segmented EPI. Differences in signal-to-noise ratio (SNR), CNR, relative maximal upslope (RMU) of signal amplitude, and artifacts at comparable temporal and spatial resolution among the three sequences were investigated in computer simulation, contrast agent doped phantoms, and 16 volunteers. The results demonstrate that SSFP perfusion images exhibit an improvement of approximately 77% in SNR and 23% in CNR over spoiled GRE and 85% SNR and 50% CNR over segmented EPI. Mean RMU was similar between SSFP and spoiled GRE, but there was a 58% increase in RMU with SSFP versus segmented EPI.