Accuracy of Left Ventricular Cavity Volume and Ejection Fraction for Conventional Estimation Methods and 3D Surface Fitting

Echocardiographic assessment of left ventricular volumes: a comparison of different methods in athletes

BACKGROUND

Cardiac magnetic resonance imaging (cMRI) is considered the gold standard for the assessment of left ventricular (LV) systolic function. However, discrepancies have been reported in the literature between LV volumes assessed by transthoracic echocardiography (TTE) and cMRI. The objective of this study was to analyze the differences in LV volumes between different echocardiographic techniques and cMRI.

METHODS AND RESULTS

In 64 male athletes (21.1 ± 4.9 years), LV volumes were measured by TTE using the following methods: Doppler echocardiography, anatomical M-Mode, biplane/triplane planimetry and 3D volumetry. In addition, LV end-diastolic (LVEDV), end-systolic (LVESV), and stroke volumes (LVSV) were assessed in 11 athletes by both TTE and cMRI. There was no significant difference between LVEDV and LVESV determined by biplane/triplane planimetry and 3D volumetry. LVEDV and LVESV measured by M-Mode were significantly lower compared to 3D volumetry. LVSV determined by Doppler with 3D planimetry of LV outflow tract was significantly higher than 2D planimetry and 3D volumetry, whereas none of the planimetric or volumetric methods for determining LVSV differed significantly. There were no significant differences for LVEDV, LVESV, LVSV and LVEF between cMRI and TTE determined by biplane planimetry in the subgroup of 11 athletes.

CONCLUSION

The choice of echocardiographic method used has an impact on LVSV in athletes, so the LVSV should always be checked for plausibility. The same echocardiographic method should be used to assess LVSV at follow-ups to ensure good comparability. The data suggest that biplane LV planimetry by TTE is not inferior to cMRI.

Automatic left ventricle volume and mass quantification from 2D cine-MRI: Investigating papillary muscle influence

OBJECTIVE

Early detection of cardiovascular diseases is based on accurate quantification of the left ventricle (LV) function parameters. In this paper, we propose a fully automatic framework for LV volume and mass quantification from 2D-cine MR images already segmented using U-Net.

METHODS

The general framework consists of three main steps: Data preparation including automatic LV localization using a convolution neural network (CNN) and application of morphological operations to exclude papillary muscles from the LV cavity. The second step consists in automatically extracting the LV contours using U-Net architecture. Finally, by integrating temporal information which is manifested by a spatial motion of myocytes as a third dimension, we calculated LV volume, LV ejection fraction (LVEF) and left ventricle mass (LVM). Based on these parameters, we detected and quantified cardiac contraction abnormalities using Python software.

RESULTS

CNN was trained with 35 patients and tested on 15 patients from the ACDC database with an accuracy of 99,15 %. U-Net architecture was trained using ACDC database and evaluated using local dataset with a Dice similarity coefficient (DSC) of 99,78 % and a Hausdorff Distance (HD) of 4.468 mm (p < 0,001). Quantification results showed a strong correlation with physiological measures with a Pearson correlation coefficient (PCC) of 0,991 for LV volume, 0.962 for LVEF, 0.98 for stroke volume (SV) and 0.923 for LVM after pillars' elimination. Clinically, our method allows regional and accurate identification of pathological myocardial segments and can serve as a diagnostic aid tool of cardiac contraction abnormalities.

CONCLUSION

Experimental results prove the usefulness of the proposed method for LV volume and function quantification and verify its potential clinical applicability.

The robustness of the flow-gradient classification of severe aortic stenosis

Objectives

A flow-gradient classification is used to determine the indication for intervention for patients with severe aortic stenosis (AS) with discordant echocardiographic parameters. We investigated the agreement in flow-gradient classification by stroke volume (SV) measurement at the left ventricular outflow tract (LVOT) and at the left ventricle.

Methods

Data were used from a prospective cohort study and patients with severe AS (aortic valve area index ≤0.6 cm2/m2) with preserved ejection fraction (>50%) were selected. SV was determined by an echocardiographic core laboratory at the LVOT and by subtracting the 2-dimensional left ventricle end-systolic from the end-diastolic volume (volumetric). Patients were stratified into 4 groups based on SV index (35 mL/m2) and mean gradient (40 mm Hg). The group composition was compared and the agreement between the SV measurements was investigated using regression, correlation, and limits of agreement. In addition, a systematic LVOT diameter overestimation of 1 mm was simulated to study flow-gradient reclassification.

Results

Of 1118 patients, 699 were eligible. The group composition changed considerably as agreement on flow state occurred in only 50% of the measurements. LVOT SV was on average 15.1 mL (95% limits of agreement -24.9:55.1 mL) greater than volumetric SV. When a systematic 1-mm LVOT diameter overestimation was introduced, the low-flow groups halved.

Conclusions

There was poor agreement in the flow-gradient classification of severe AS as a result of large differences between LVOT and volumetric SV. Furthermore, this classification was sensitive to small measurement errors. These results stress that parameters beyond the flow-gradient classification should be considered to ensure accurate recommendations for intervention.

Accuracy of Devereaux and Teichholz formulas for left ventricular mass calculation in different geometric patterns: comparison with cardiac magnetic resonance imaging

Left ventricular (LV) myocardial mass is important in the evaluation of cardiac remodeling and requires accurate assessment when performed on linear measurements in two-dimensional echocardiography (Echo). We aimed to compare the accuracy of the Devereaux formula (DEV) and the Teichholz formula (TEICH) in calculating LV myocardial mass in Echo using cardiac magnetic resonance (CMR) as the reference method. Based on preceding mathematical calculations, we identified primarily LV size rather than wall thickness as the main source of bias between DEV and TEICH in a retrospective derivation cohort (n = 1276). Although LV mass from DEV and TEICH were correlated with CMR, TEICH did not show a proportional bias as did DEV (- 2 g/m2 vs. + 22 g/m2). This could be validated in an independent prospective cohort (n = 226) with symptomatic non-ischemic heart failure. DEV systematically overestimated LV mass in all tiers of LV remodeling as compared to TEICH. In conclusion, the TEICH method accounts for the changes in LV geometry with increasing LV mass and thus better reflects the different pattern of LV remodeling than the DEV method. This has important clinical implications, as TEICH may be more appropriate for use in clinical practice, rather than DEV, currently recommended.

Valid and Reproducible Quantitative Assessment of Cardiac Volumes by Echocardiography in Patients with Valvular Heart Diseases-Possible or Wishful Thinking?

The analysis of left ventricular function is predominantly based on left ventricular volume assessment. Especially in valvular heart diseases, the quantitative assessment of total and effective stroke volumes as well as regurgitant volumes is necessary for a quantitative approach to determine regurgitant volumes and regurgitant fraction. In the literature, there is an ongoing discussion about differences between cardiac volumes estimated by echocardiography and cardiac magnetic resonance tomography. This viewpoint focuses on the feasibility to assess comparable cardiac volumes with both modalities. The former underestimation of cardiac volumes determined by 2D and 3D echocardiography is presumably explained by methodological and technical limitations. Thus, this viewpoint aims to stimulate an urgent and critical rethinking of the echocardiographic assessment of patients with valvular heart diseases, especially valvular regurgitations, because the actual integrative approach might be too error prone to be continued in this form. It should be replaced or supplemented by a definitive quantitative approach. Valid quantitative assessment by echocardiography is feasible once echocardiography and data analysis are performed with methodological and technical considerations in mind. Unfortunately, implementation of this approach cannot generally be considered for real-world conditions.

Impact of Measurement Imprecision on Genetic Association Studies of Cardiac Function

Background

Recent studies have leveraged quantitative traits from imaging to amplify the power of genome-wide association studies (GWAS) to gain further insights into the biology of diseases and traits. However, measurement imprecision is intrinsic to phenotyping and can impact downstream genetic analyses.

Methods

Left ventricular ejection fraction (LVEF), an important but imprecise quantitative imaging measurement, was examined to assess the impact of precision of phenotype measurement on genetic studies. Multiple approaches to obtain LVEF, as well as simulated measurement noise, were evaluated with their impact on downstream genetic analyses.

Results

Even within the same population, small changes in the measurement of LVEF drastically impacted downstream genetic analyses. Introducing measurement noise as little as 7.9% can eliminate all significant genetic associations in an GWAS with almost forty thousand individuals. An increase of 1% in mean absolute error (MAE) in LVEF had an equivalent impact on GWAS power as a decrease of 10% in the cohort sample size, suggesting optimizing phenotyping precision is a cost-effective way to improve power of genetic studies.

Conclusions

Improving the precision of phenotyping is important for maximizing the yield of genome-wide association studies.

Heart failure with mildly reduced ejection fraction: retrospective study of ejection fraction trajectory risk

AIMS

Heart failure with mildly reduced ejection fraction (HFmrEF) is associated with a favourable prognosis compared with heart failure (HF) with reduced ejection fraction (EF). We assessed whether left ventricular ejection fraction (LVEF) trajectory can be used to identify groups of patients with HFmrEF who have different clinical outcomes in a large retrospective study of patients with serial imaging.

METHODS AND RESULTS

Patients with HF and ≥2 echocardiograms performed ≥6 months apart were included if the LVEF measured 40-49% on the second study. Patients were classified as HFmrEF-Increasing if LVEF had increased ≥10% (n = 450), HFmrEF-Decreasing if LVEF had decreased ≥10% (n = 512), or HFmrEF-Stable if they did not meet other criteria (n = 389). The primary outcome was all-cause mortality or cardiovascular hospitalization after the second echocardiogram. Associations with time to first event were assessed with multivariable Cox analyses adjusted for age, co-morbidities, and medications. In total, 1351 patients with HFmrEF (median age 74, 64.2% male) were included with 28.8% exhibiting stable LVEF. During median follow-up of 15.3 months, the composite outcome occurred in 811 patients. During follow-up, patients with HFmrEF-Increasing were less likely to experience the primary outcome [adjusted hazard ratio (HR) 0.72, 95% confidence interval (CI) 0.60-0.88, P < 0.001] compared with HFmrEF-Stable. Patients with HFmrEF-Decreasing were more likely to experience the composite outcome in unadjusted analyses (unadjusted HR 1.19, 95% CI 1.01-1.40, P = 0.040) but not adjusted analyses (adjusted HR 1.16, 95% CI 0.98-1.37, P = 0.092). Associations with death or HF hospitalizations were similar (HFmrEF-Increasing: adjusted HR 0.72, 95% CI 0.59-0.88, P = 0.005; HFmrEF-Decreasing: adjusted HR 1.20, 95% CI 1.01-1.44, P = 0.044). Patients with HFmrEF-Decreasing had a similar risk of the composite outcome as patients with HF with reduced EF (adjusted HR 1.03, 95% CI 0.89-1.20, P = 0.670). Patients with HFmrEF-Increasing were less likely to experience the composite outcome compared with patients with HF with preserved EF (adjusted HR 0.73, 95% CI 0.62-0.87, P < 0.001).

CONCLUSIONS

Amongst patients with HFmrEF, those exhibiting positive LVEF trajectory were less likely to experience adverse outcomes after correcting for important confounders including medical therapy. Categorizing HFmrEF patients based on LVEF trajectory provides meaningful clinical information and may assist clinicians with management decisions.

Coenzyme Q10 to manage chronic heart failure with a reduced ejection fraction: a systematic review and economic evaluation

BACKGROUND

Chronic heart failure is a debilitating condition that accounts for an annual NHS spend of £2.3B. Low levels of endogenous coenzyme Q10 may exacerbate chronic heart failure. Coenzyme Q10 supplements might improve symptoms and slow progression. As statins are thought to block the production of coenzyme Q10, supplementation might be particularly beneficial for patients taking statins.

OBJECTIVES

To assess the clinical effectiveness and cost-effectiveness of coenzyme Q10 in managing chronic heart failure with a reduced ejection fraction.

METHODS

A systematic review that included randomised trials comparing coenzyme Q10 plus standard care with standard care alone in chronic heart failure. Trials restricted to chronic heart failure with a preserved ejection fraction were excluded. Databases including MEDLINE, EMBASE and CENTRAL were searched up to March 2020. Risk of bias was assessed using the Cochrane Risk of Bias tool (version 5.2). A planned individual participant data meta-analysis was not possible and meta-analyses were mostly based on aggregate data from publications. Potential effect modification was examined using meta-regression. A Markov model used treatment effects from the meta-analysis and baseline mortality and hospitalisation from an observational UK cohort. Costs were evaluated from an NHS and Personal Social Services perspective and expressed in Great British pounds at a 2019/20 price base. Outcomes were expressed in quality-adjusted life-years. Both costs and outcomes were discounted at a 3.5% annual rate.

RESULTS

A total of 26 trials, comprising 2250 participants, were included in the systematic review. Many trials were reported poorly and were rated as having a high or unclear risk of bias in at least one domain. Meta-analysis suggested a possible benefit of coenzyme Q10 on all-cause mortality (seven trials, 1371 participants; relative risk 0.68, 95% confidence interval 0.45 to 1.03). The results for short-term functional outcomes were more modest or unclear. There was no indication of increased adverse events with coenzyme Q10. Meta-regression found no evidence of treatment interaction with statins. The base-case cost-effectiveness analysis produced incremental costs of £4878, incremental quality-adjusted life-years of 1.34 and an incremental cost-effectiveness ratio of £3650. Probabilistic sensitivity analyses showed that at thresholds of £20,000 and £30,000 per quality-adjusted life-year coenzyme Q10 had a high probability (95.2% and 95.8%, respectively) of being more cost-effective than standard care alone. Scenario analyses in which the population and other model assumptions were varied all found coenzyme Q10 to be cost-effective. The expected value of perfect information suggested that a new trial could be valuable.

LIMITATIONS

For most outcomes, data were available from few trials and different trials contributed to different outcomes. There were concerns about risk of bias and whether or not the results from included trials were applicable to a typical UK population. A lack of individual participant data meant that planned detailed analyses of effect modifiers were not possible.

CONCLUSIONS

Available evidence suggested that, if prescribed, coenzyme Q10 has the potential to be clinically effective and cost-effective for heart failure with a reduced ejection fraction. However, given important concerns about risk of bias, plausibility of effect sizes and applicability of the evidence base, establishing whether or not coenzyme Q10 is genuinely effective in a typical UK population is important, particularly as coenzyme Q10 has not been subject to the scrutiny of drug-licensing processes. Stronger evidence is needed before considering its prescription in the NHS.

FUTURE WORK

A new independent, well-designed clinical trial of coenzyme Q10 in a typical UK heart failure with a reduced ejection fraction population may be warranted.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42018106189.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 26, No. 4. See the NIHR Journals Library website for further project information.

A Mechanistic Lumped Parameter Model of the Berlin Heart EXCOR to Analyze Device Performance and Physiologic Interactions

PURPOSE

The Berlin Heart EXCOR (BH) is the only FDA-approved, extracorporeal pulsatile ventricular assist device (VAD) for infants and children with heart failure. Clinicians control four settings on the device-systolic and diastolic drive pressures, device pump rate, and systolic time as a percentage of the pump cycle. However, interactions between BH pneumatics and the native circulation remain poorly understood. Thus, establishing appropriate device size and settings can be challenging on a patient-to-patient basis.

METHODS

In this study we develop a novel lumped parameter network based on simplified device mechanics. We perform parametric studies to characterize device behavior, study interactions between the left ventricle (LV) and BH across different device settings, and develop patient-specific simulations. We then simulate the impact of changing device parameters for each of three patients.

RESULTS

Increasing systolic pressure and systolic time increased device output. We identified previously unobserved cycle-to-cycle variations in LV-BH interactions that may impact patient health. Patient-specific simulations demonstrated the model's ability to replicate BH performance, captured trends in LV behavior after device implantation, and emphasized the importance of device rate and volume in optimizing BH efficiency.

CONCLUSION

We present a novel, mechanistic model that can be readily adjusted to study a wide range of device settings and clinical scenarios. Physiologic interactions between the BH and the native LV produced large variability in cardiac loading. Our findings showed that operating the BH at a device rate greater than the patient's native heart decreases variability in physiological interactions between the BH and LV, increasing cardiac offloading while maintaining cardiac output. Device rates that are close to the resting heart rate may result in unfavorable cardiac loading conditions. Our work demonstrates the utility of our model to investigate BH performance for patient-specific physiologies.

Numerical wave speed sensitivity study for assessment of myocardial elasticity in a simplified linear elastic and isotropic left ventricle model

Since tissue elasticity can change with pathology, noninvasive assessment of elasticity has received increasing attention. Emerging methods for assessing cardiac elasticity utilize either an external source to induce propagating shear waves or intrinsic longitudinal waves created by natural cardiac events such as left ventricle stretching that occurs due to atrial kick during late diastole. However, the effect of morphological variations that occur in diseased hearts on this longitudinal stretch wave and the corresponding estimate of elasticity is not well understood and is an active area of research. This study investigated the sensitivity of longitudinal wave speed to material properties and chamber geometry parameters through numerical simulations using a finite element model of a bullet-shaped chamber with homogeneous isotropic linear elastic material properties. A longitudinal impulse displacement was applied to the base edge of the model to investigate wave propagation from this boundary. Parametric studies were performed for variables of interest related to geometry and material properties. The wave speeds estimated from simulation results were used to determine wave speed sensitivity to each variable. Wave speed was found to be a strong function of material elasticity and a weak function of chamber geometry and viscous damping. Simulated wave speed as a function of elasticity was in good agreement with wave speeds determined from an analytical expression for longitudinal wave speed in elastic thin plates. These promising preliminary results increase our understanding of how these parameters affect intrinsic longitudinal wave speed and warrant future studies addressing the impact of patient-specific model geometry, material anisotropy and hyperelasticity, and boundary conditions on wave speed.

Evaluation and Comparison of Left Ventricular Functions by Cardiac MRI and 2D Transthoracic Echocardiography

Objective

It is important to measure left ventricular function (LVF) accurately in the diagnosis and follow-up of cardiovascular diseases. Different imaging algorithms and mathematical calculations have been developed for the evaluation of LVF in cardiac magnetic resonance imaging (MRI), and numerous studies are still being carried on this. In our study, LVF was calculated by two different measurement methods in MRI and were compared with transthoracic echocardiography (TTE) to assess the correlation and the consistency of these with TTE.

Materials and Methods

In this study, 31 patients with left ventricular dysfunction due to different etiologies were evaluated with simultaneous TTE and MRI. In the Cine MR images, LVF parameters of ejection fraction, end-diastolic volume, end-systolic volume, and myocardial mass were measured using short axis images (short axis method) and short axis plus four chamber and two chamber images (combined method). The results were compared with the results from TTE.

Results

We found that the combined and the short axis-based calculations of ejection fraction, end-diastolic volume, end-systolic volume, and myocardial mass in cardiac MRI showed correlation and consistency with those calculated via echocardiography. We also determined that the short axis-based calculations in cardiac MRI showed better correlation with the echocardiography compared with the combined method.

Conclusion

Because our results revealed that the cardiac MRI results obtained from the short axis method better correlate with the TTE, we recommend using short axis-based measurements in the evaluation left ventricular dysfunction.

Comparison of the within-reader and inter-vendor agreement of left ventricular circumferential strains and volume indices derived from cardiovascular magnetic resonance imaging

PURPOSE

Volume indices and left ventricular ejection fraction (LVEF) are routinely used to assess cardiac function. Ventricular strain values may provide additional diagnostic information, but their reproducibility is unclear. This study therefore compares the repeatability and reproducibility of volumes, volume fraction, and regional ventricular strains, derived from cardiovascular magnetic resonance (CMR) imaging, across three software packages and between readers.

METHODS

Seven readers analysed 16 short-axis CMR stacks of a porcine heart. Endocardial contours were manually drawn using OsiriX and Simpleware ScanIP and repeated in both softwares. The images were also contoured automatically in Circle CVI42. Endocardial global, apical, mid-ventricular, and basal circumferential strains, as well as end-diastolic and end-systolic volume and LVEF were compared.

RESULTS

Bland-Altman analysis found systematic biases in contour length between software packages. Compared to OsiriX, contour lengths were shorter in both ScanIP (-1.9 cm) and CVI42 (-0.6 cm), causing statistically significant differences in end-diastolic and end-systolic volumes, and apical circumferential strain (all p<0.006). No differences were found for mid-ventricular, basal or global strains, or left ventricular ejection fraction (all p<0.007). All CVI42 results lay within the ranges of the OsiriX results. Intra-software differences were found to be lower than inter-software differences.

CONCLUSION

OsiriX and CVI42 gave consistent results for all strain and volume metrics, with no statistical differences found between OsiriX and ScanIP for mid-ventricular, global or basal strains, or left ventricular ejection fraction. However, volumes were influenced by the choice of contouring software, suggesting care should be taken when comparing volumes across different software.

Accuracy of Left Ventricular Cavity Volume and Ejection Fraction for Conventional Estimation Methods and 3D Surface Fitting

Background

While left ventricular cavity volume (LVV) and ejection fraction (LVEF) are used routinely for clinical decision‐making, the errors in LVV and LVEF estimates in the clinic have yet to be rigorously quantified and are perhaps underappreciated.

Methods and Results

The goal of this study was to quantify the accuracy and precision of several common geometric‐model‐based methods for estimating LVV and LVEF using a highly sampled, high‐resolution magnetic resonance imaging data set and an independent ground truth. The effect on LVV and LVEF accuracy of slice number and orientation was also studied. When using the common geometric assumptions and limited short‐ and/or long‐axis views, the expected LVEF measurement uncertainty can be as high as 49%. The composite midpoint rule applied to a stack of short‐axis slices can achieve LVEF error <3% and LVV error of ≈10%, but in the clinic an additional ≈8% uncertainty is expected. An analogous approach applied to a series of radially prescribed long‐axis slices can achieve higher LVEF accuracy, up to 3.9% with 12 slices, and more reliable LVV measurements than methods based solely on short‐axis images. Using a mathematical 3‐dimensional surface model that incorporates anatomic information from multiple views achieves superior accuracy, with LVEF error <4% and LVV error <2.5% when using 6 slices in each short‐ and long‐axis view.

Conclusions

Combining anatomical information from multiple views into a conformal 3‐dimensional surface model greatly reduces errors in LVV and LVEF estimates, with potential clinical benefit via improved early detection of cardiac disease.