Determination of ventricular ejection fraction: a comparison of available imaging methods. The Cardiovascular Imaging Working Group

Left Ventricular Function in Healthy Term Neonates During the Transitional Period

OBJECTIVES

To evaluate whether incorporating conventional, tissue Doppler imaging and speckle tracking echocardiography are reliable and can characterize changes in left ventricular (LV) function properly in healthy neonates in the early transitional newborn period.

STUDY DESIGN

A prospective observational study was conducted in 50 healthy term neonates with a mean ± SD gestational age and birth weight of 39.3 ± 1.2 weeks and 3.5 ± 0.44 kg, respectively. All infants underwent serial echocardiograms at 15 ± 2 (day 1) and 35 ± 2 hours (day 2) of age. The LV dimensions and various functional indices including tissue Doppler imaging velocities and speckle tracking echocardiography-derived peak longitudinal strain, and systolic and diastolic strain rate were acquired and compared between time points.

RESULTS

All measurements were feasible from each scan except speckle tracking echocardiography in 10% and 20% of images on days 1 and 2 of age, respectively. LV dimensions, but not functional measures, demonstrated a small to moderate positive correlation with birth weight. On day 2, a small reduction was observed in LV basal diameter, mitral valve inflow velocity time integral, and systolic velocity of the lateral wall and septum. Other indices remained unchanged. Tissue Doppler imaging-derived functional and flow-derived hemodynamic measures demonstrated the least measurement bias, and strain measurements demonstrated better reliability than strain rate, fractional shortening, and ejection fraction.

CONCLUSION

The relative reliability of various echocardiographic indices to quantify LV function in neonates establish a normative dataset and provide evidence for their validity during the first 2 days of life.

Technical report. Left ventricular ejection fraction measurement using cardiovascular magnetic resonance imaging in patients with post-myocardial infarction: assessment of reproducibility by a cardiovascular radiologist and a trained technologist

Background: Cardiovascular magnetic resonance imaging (CMR) has recently been accepted as a preferential method for evaluation left ventricular ejection fraction (LVEF). The LVEF analysis by CMR is usually performed by trained technologists in many institutions of Thailand.

Objective: Assess the reproducibility of LVEF measured by a cardiovascular radiologist and a trained technologist using CMR in patients with post-myocardial infarction (MI).

Methods: Twenty-one MI patients (18 men and 3 women) were recruited, where nine patients underwent CMR and left ventriculography to follow-up LVEF two times in six months. Both CMR and left ventriculography were examined within two weeks. LVEF from CMR were measured by a cardiovascular radiologist and a trained technologist and the correlation between the left ventriculography and CMR was determined.

Results: In 30 CMR studies, interobserver reliability (intraclass correlation coefficient ICC=0.94) and intraobserver reliability (ICC=0.96) was excellent. LVEF measured by left ventriculography was higher compared with that by CMR, and their correlation was moderate (ICC=0.56).

Conclusion: The LVEF measurement by a cardiovascular radiologist and a trained technologist using CMR was very reproducible, but the correlation between CMR and left ventriculography was moderate.

Fuzzy Modeling to Predict Severely Depressed Left Ventricular Ejection Fraction following Admission to the Intensive Care Unit Using Clinical Physiology

Left ventricular ejection fraction (LVEF) constitutes an important physiological parameter for the assessment of cardiac function, particularly in the settings of coronary artery disease and heart failure. This study explores the use of routinely and easily acquired variables in the intensive care unit (ICU) to predict severely depressed LVEF following ICU admission. A retrospective study was conducted. We extracted clinical physiological variables derived from ICU monitoring and available within the MIMIC II database and developed a fuzzy model using sequential feature selection and compared it with the conventional logistic regression (LR) model. Maximum predictive performance was observed using easily acquired ICU variables within 6 hours after admission and satisfactory predictive performance was achieved using variables acquired as early as one hour after admission. The fuzzy model is able to predict LVEF ≤ 25% with an AUC of 0.71 ± 0.07, outperforming the LR model, with an AUC of 0.67 ± 0.07. To the best of the authors' knowledge, this is the first study predicting severely impaired LVEF using multivariate analysis of routinely collected data in the ICU. We recommend inclusion of these findings into triaged management plans that balance urgency with resources and clinical status, particularly for reducing the time of echocardiographic examination.

Effect of percutaneous mitral balloon valvuloplasty on right ventricular functions in mitral stenosis: short- and mid-term results

OBJECTIVE

To evaluate the short- and mid-term effects of percutaneous mitral balloon valvuloplasty (PMBV) on right ventricular functions in mitral stenosis.

METHODS

A prospective study was conducted in 61 patients who had mitral stenosis in normal sinus rhythm (68% female, age: 42±11-16 years). Right ventricular functions were measured before, immediately after, and at 3 months and 1 year after PMBV by conventional and tissue Doppler echocardiography imaging methods. Additionally, the patients were evaluated in two groups (PAP≥40 mm Hg, n: 46; PAP<40 mm Hg, n: 15) according to the systolic pulmonary artery that was measured by echocardiography prior to PMBV.

RESULTS

Post-PMBV mean gradient, pulmonary artery pressure (PAP), and left atrial size decreased significantly, and the mitral valve area increased significantly in both patient groups. This significance in pulmonary artery pressure was lost at 1 year. The significant post-PMBV increase in tricuspid annular point systolic excursion (TAPSE), systolic velocity, early diastolic velocity, and peak myocardial velocity during isovolumic contraction (IVV), indicating right ventricular functions, disappeared at 1 year. The significant post-PMBV decrease in myocardial performance index (MPI) and late diastolic velocity lost its significance at 1 year. No significant change was observed in myocardial acceleration during isovolumic contraction (IVA). The group with pulmonary hypertension demonstrated significance similar to the results of the overall group. Post-PMBV TAPSE, systolic velocity, early diastolic velocity, IVV, and IVA increased significantly, and this increase was maintained up to 1 year in the group without pulmonary hypertension. MPI and late diastolic velocity maintained their significantly decreased values up to 1 year.

CONCLUSION

The positive effect of PMBV on right ventricular function in the acute period decreases and even disappears in the mid-term in patients developing pulmonary hypertension. Intervention in the patients prior to the development of hypertension is very important for the improvement in right ventricular functions.

Subclinical left and right ventricular systolic dysfunction in Behcet's disease: a combined tissue doppler and velocity vector imaging study

BACKGROUND

Behcet's disease (BD) is a chronic inflammatory disease characterized by recurrent oral and genital ulcerations and ocular lesions. Subclinical cardiac involvement may develop in BD patients. We aimed to evaluate subclinical left ventricular (LV) and right ventricular (RV) systolic dysfunction in BD patients without any apparent cardiovascular disease.

METHODS

We studied 50 BD patients (43.8 ± 9.7 years, 59% men) and 30 healthy controls (45.4 ± 8.2 years, 60% men). Conventional echocardiography, tissue Doppler imaging, and velocity vector imaging-based strain measurements were performed to analyze LV and RV systolic functions.

RESULTS

LV isovolumic myocardial acceleration, peak systolic velocity during isovolumic contraction (isovolumic contraction velocity), were significantly lower, while myocardial performance index was increased in BD patients. RV peak systolic velocity, isovolumic myocardial acceleration, and isovolumic contraction velocity were also markedly lower in BD patients. LV and RV longitudinal peak systolic strain and strain rate were significantly lower in patients than in controls, demonstrating subclinical ventricular systolic dysfunction.

CONCLUSIONS

Ventricular long-axis functions are important markers of myocardial contractility. Novel echocardiographic techniques may provide additional data for detecting early deterioration in ventricular systolic function in patients with BD.

Tricuspid annular peak systolic velocity (S') in children and young adults with pulmonary artery hypertension secondary to congenital heart diseases, and in those with repaired tetralogy of Fallot: echocardiography and MRI data

BACKGROUND

Tricuspid annular peak systolic velocity (S'), as an echocardiographic index to assess right ventricular (RV) systolic function, has not been investigated thoroughly in children and young adults with repaired tetralogy of Fallot (TOF) and pulmonary artery hypertension secondary to congenital heart disease (PAH-CHD).

METHODS

S' values in patients with TOF (n = 183) and PAH-CHD (n = 55) were compared with those in normal subjects. S' values were compared with RV ejection fraction and RV end-diastolic volume index (RVEDVi) determined by magnetic resonance imaging.

RESULTS

S' values became significantly reduced in PAH-CHD patients after 10.4 years of age and after 13.6 years of age in patients with TOF compared with the lower boundary of the ±2-SD interval of normal subjects. Significant positive correlations between S' and RV ejection fraction were seen in patients with TOF (r = 0.66, P < .001) and those with PAH-CHD (r = 0.82, P < .001). Significant negative correlations between S' and RVEDVi were also seen in patients with repaired TOF (r = -0.29, P = .002) and in those with PAH-CHD (r = -0.59, P < .001).

CONCLUSIONS

Although initially preserved, in this prospective study, impaired S' values with increasing age were found in patients with repaired TOF and PAH-CHD. Persistent pressure overload in patients with PAH-CHD as well as volume overload in those with repaired TOF might lead to systolic RV functional impairment and increased RVEDVi. The validity of S' data was supported by magnetic resonance imaging data (RVEDVi and RV ejection fraction).

The forgotten chamber: right-ventricular functions in juvenile idiopathic arthritis

Cardiac involvement, such as pericarditis, myocarditis, and endocarditis, is seen in juvenile idiopathic arthritis. Although there have been some reports about right-ventricular systolic and diastolic functions of adults with rheumatoid arthritis and left-ventricular systolic and diastolic functions of children with JIA, there have been no studies about RV functions of children with JIA. The aim of this study was to determine RV functions in children with JIA. We performed conventional echocardiography and tissue Doppler imaging measurements of the right ventricle of patients with JIA. All patients were in sinus rhythm at the time of examination without overt LV heart failure and with normal LV ejection fraction. Fifty-five children with the diagnosis of JIA and 33 healthy control subjects were included in the study. Peak systolic, early, and late diastolic tricuspid annular velocities were significantly decreased in JIA patients compared with healthy controls (p < 0.05). Isovolumic accelaration (IVA), as a measure of myocardial acceleration during isovolumic contraction of the right ventricle, was also significantly lower in JIA patients than in healthy controls (p < 0.05). RV systolic and diastolic functions, in addition to the previously shown LV functions, are affected in JIA patients. IVA decreases in JIA patients and may be used as an alternative, noninvasive parameter for the assessment of RV systolic function in children with JIA.

Continuous and less invasive central hemodynamic monitoring by blood pressure waveform analysis

Blood pressure waveform analysis may permit continuous (i.e., automated) and less invasive (i.e., safer and simpler) central hemodynamic monitoring in the intensive care unit and other clinical settings without requiring any instrumentation beyond what is already in use or available. This practical approach has been a topic of intense investigation for decades and may garner even more interest henceforth due to the evolving demographics as well as recent trends in clinical hemodynamic monitoring. Here, we review techniques that have appeared in the literature for mathematically estimating clinically significant central hemodynamic variables, such as cardiac output, from different blood pressure waveforms. We begin by providing the rationale for pursuing such techniques. We then summarize earlier techniques and thereafter overview recent techniques by our collaborators and us in greater depth while pinpointing both their strengths and weaknesses. We conclude with suggestions for future research directions in the field and a description of some potential clinical applications of the techniques.

Factor analysis of ventricular contraction using SPECT-ERNA images

Equilibrium radionuclide angiography images (ERNA) has been established as a useful modality for clinical evaluation of the ventricular function. Tomographic acquisition of ERNA (SPECT-ERNA) improves the quantification of ventricular function with planar ERNA, avoiding both the overlap of structures and the need of defining the best septal view which can be difficult in dilated ventricles. In this work we analyze the contribution and distribution of the most significant factors of dynamic structures (FADS), and propose an index based on the characterization of the normal contraction pattern, to quantify the ventricular contraction normality in a set of patients with clinical diagnosis of pulmonary arterial hypertension (PAH) using SPECT-ERNA. The statistical analysis shows significant differences between normal and PAH subjects in the models of left ventricle (LV) contraction pattern. This comparison shows that the LV has an abnormal contraction as a consequence of the pulmonary arterial hypertension.

Visually estimated ejection fraction by two dimensional and triplane echocardiography is closely correlated with quantitative ejection fraction by real-time three dimensional echocardiography

Background

Visual assessment of left ventricular ejection fraction (LVEF) is often used in clinical routine despite general recommendations to use quantitative biplane Simpsons (BPS) measurements. Even thou quantitative methods are well validated and from many reasons preferable, the feasibility of visual assessment (eyeballing) is superior. There is to date only sparse data comparing visual EF assessment in comparison to quantitative methods available. The aim of this study was to compare visual EF assessment by two-dimensional echocardiography (2DE) and triplane echocardiography (TPE) using quantitative real-time three-dimensional echocardiography (RT3DE) as the reference method.

Methods

Thirty patients were enrolled in the study. Eyeballing EF was assessed using apical 4-and 2 chamber views and TP mode by two experienced readers blinded to all clinical data. The measurements were compared to quantitative RT3DE.

Results

There were an excellent correlation between eyeballing EF by 2D and TP vs 3DE (r = 0.91 and 0.95 respectively) without any significant bias (-0.5 ± 3.7% and -0.2 ± 2.9% respectively). Intraobserver variability was 3.8% for eyeballing 2DE, 3.2% for eyeballing TP and 2.3% for quantitative 3D-EF. Interobserver variability was 7.5% for eyeballing 2D and 8.4% for eyeballing TP.

Conclusion

Visual estimation of LVEF both using 2D and TP by an experienced reader correlates well with quantitative EF determined by RT3DE. There is an apparent trend towards a smaller variability using TP in comparison to 2D, this was however not statistically significant.

Continuous left ventricular ejection fraction monitoring by aortic pressure waveform analysis

We developed a technique to monitor left ventricular ejection fraction (EF) by model-based analysis of the aortic pressure waveform. First, the aortic pressure waveform is represented with a lumped parameter circulatory model. Then, the model is fitted to each beat of the waveform to estimate its lumped parameters to within a constant scale factor equal to the arterial compliance (C (a)). Finally, the proportional parameter estimates are utilized to compute beat-to-beat absolute EF by cancelation of the C (a) scale factor. In this way, in contrast to conventional imaging, EF may be continuously monitored without any ventricular geometry assumptions. Moreover, with the proportional parameter estimates, relative changes in beat-to-beat left ventricular end-diastolic volume (EDV), cardiac output (CO), and maximum left ventricular elastance (E (max)) may also be monitored. To evaluate the technique, we measured aortic pressure waveforms, reference EF and EDV via standard echocardiography, and other cardiovascular variables from six dogs during various pharmacological influences and total intravascular volume changes. Our results showed overall EF and calibrated EDV root-mean-squared-errors of 5.6% and 4.1 mL, and reliable estimation of relative E (max) and beat-to-beat CO changes. These results demonstrate, perhaps for the first time, the feasibility of estimating EF from only a blood pressure waveform.

Assessment of right ventricular size and function: echo versus magnetic resonance imaging

OBJECTIVE

The assessment of right ventricular (RV) size and function is important in the management of many patients with heart disease. Although magnetic resonance imaging (MRI) is considered the gold standard for quantitation of ventricular volumes and systolic function, subjective assessment ("eyeball") by echocardiography is the modality most often used for the RV. The echocardiographic "eyeball" method of assessing RV size and systolic function was compared with quantitative MRI.

DESIGN

Patients with right-sided congenital heart disease who underwent an echocardiogram within 6 months of MRI formed the study group. Four echocardiographers blinded to the MRI results reviewed the echocardiograms to subjectively assess RV size and systolic function. The reliability of an echocardiographer in accurately identifying a severely dilated RV and moderately to severely diminished RV systolic function was measured using the Kappa coefficient. Inter-rater agreement was also assessed using Kappa.

RESULTS

The study group consisted of 22 patients aged 16.6 +/- 7.1 years, with interval between MRI and echocardiogram of 49 +/- 54 days. Using echocardiography, reliability for accurately identifying a severely dilated RV was "slight" with a prevalence-adjusted bias-adjusted Kappa (PABAK) of 0.25; and for identifying moderately to severely diminished RV systolic function was fair with a PABAK of 0.43. Inter-rater agreement analysis was poor for both with Kappas of 0.07 (P = .22) and 0.12 (P = .09), respectively.

CONCLUSION

The usefulness of the echocardiographic "eyeball" method to estimate RV size and systolic function in patients with right heart disease has limitations when compared with MRI, specifically in regard to the variability between echocardiographers.

[Quantification of ventricular mass and function using real-time free-breathing SSFP sequences]

OBJECTIVES

To compare real-time free-breathing steady-state free precession (SSFP) sequences with conventional breath-hold segmented SSFP sequences on the quantification of ventricular mass and function.

MATERIAL AND METHODS

Cardiac function and mass were assessed in 15 consecutive patients with cardiopathies who underwent MRI for diverse indications. Sequences were planned in the short axis to include the area from the base to the apex of the ventricle. Two sequences were used: 1) a conventional breath-hold segmented SSFP sequence with 7-mm-thick slices and 3-mm gap between slices and 2) a real-time free-breathing SSFP sequence with 10-mm-thick slices. The systolic and diastolic volumes (VTD, VTS) and ejection fraction (EF) of both ventricles were evaluated and the mass of the left ventricle (LVM) was measured. The correlation between the different sequences was studied for each variable.

RESULTS

An excellent correlation was observed between the two sequences on the quantification of cardiac parameters in both ventricles (0.9; p < 0.01). The mean differences for EF, VTD, VTS, and stroke volume (VTD-VTS) were 2.5% (2.1), 5.6 ml (14.2), -0.8 ml (6.4), 6.4 ml (9.4), respectively, for the left ventricle and 1.7% (3.1), 1.8 ml (18.7), -1.9 ml (9.8), 3.7 ml (10.8), respectively, for the right ventricle. The mean difference between the LVM was 4.8 g (6.3).

CONCLUSIONS

The real-time free-breathing SSFP sequence is useful for the quantification of ventricular mass and function. The correlation with conventional SSFP is excellent. Both sequences allow the cardiac parameters to be precisely quantified and the results are reproducible.

Quantitative assessment of regional left ventricular wall thickness and thickening using 16 multidetector-row computed tomography: comparison with cine magnetic resonance imaging

PURPOSE

The purpose of this study was to investigate the feasibility of retrospective electrocardiography-gated multidetector-row computed tomography (MDCT) in the assessment left ventricular (LV) wall thickness and thickening and to test its validity compared to cine magnetic resonance imaging (MRI) as a standard of reference.

MATERIALS AND METHODS

We enrolled 19 patients who underwent both cardiac MDCT and cine MRI. End-diastolic wall thickness (EDWT) and end-systolic wall thickness (ESWT) were measured in 16 myocardial segments. Percent systolic wall thickening (%SWT) was generated from the EDWT and ESWT. Nondiagnostic myocardial segments were excluded. Correlation and agreement between MDCT and cine MRI were analyzed.

RESULTS

Segmental assessability values were 86.2% (262/304) and 92.1% (280/304) for MDCT and cine MRI, respectively. In assessable segments by both modalities (80.9%, 246/304), a significant correlation between MDCT and MRI was found (r = 0.89, 0.85, and 0.61, for EDWT, ESWT, and %SWT, respectively; all P < 0.05). Mean EDWT and ESWT values by MDCT were slightly lower than those by cine MRI (9.8 +/- 3.6 vs. 10.0 +/- 3.7 mm and 13.8 +/- 4.4 vs. 14.1 +/- 4.3 mm, respectively; both P < 0.01). Bland-Altman analysis revealed acceptable limits of agreement between MDCT and Cine MRI.

CONCLUSION

MDCT is a feasible method to assess regional LV wall thickness and systolic thickening.

Value of Tissue Doppler Myocardial Velocities of Tricuspid Lateral Annulus for the Diagnosis of Right Heart Failure in Patients with COPD

OBJECTIVE

Aim of this study was to investigate the value of systolic indices of tricuspid valve annular motion measured by tissue Doppler imaging for the diagnosis right ventricular failure in patients with chronic obstructive pulmonary disease (COPD).

METHODS

Patients with COPD with right heart failure symptoms and/or right ventricular dilatation were enrolled for the study. The control group consisted of age and sex matched patients referred to the echocardiography laboratory who had normal echocardiographic examination. Tricuspid valve annulus peak systolic velocity and myocardial acceleration during isovolumic contraction were recorded by tissue Doppler imaging.

RESULTS

IVA and Sa wave velocities were found to be significantly decreased in patients with right ventricular failure. For the prediction of right heart failure IVA <3.8 m/sec2 had 91% sensitivity, 80% specificity, 90% positive predictive value (PPV), and 82% negative predictive value (NPV) and Sa wave velocity <9.2 cm/sec had 80% sensitivity, 62% specificity, 75% PPV, and 68% NPV.

CONCLUSION

Tricuspid valve annular velocities measured by tissue Doppler imaging especially IVA, offer potential diagnostic value for the diagnosis of right heart failure in patients with COPD.

Continuous ejection fraction estimation by model-based analysis of an aortic pressure waveform: comparison to echocardiography

Left ventricular ejection fraction (EF) is perhaps the most clinically significant index of global ventricular function. EF is measured in clinical practice using imaging methods such as non-invasive echocardiography. However, imaging methods generally require a skilled operator and expensive equipment. Thus, EF is not sufficiently monitored. To this end, we have recently developed a novel technique to continuously (i.e., automatically) estimate EF by model-based analysis of an aortic pressure waveform. Here, we review the technique and present its evaluation with respect to reference echocardiography measurements from three dogs during diverse interventions. We report an overall EF error of only 8.3%. With further successful testing, the technique may ultimately be utilized for continuous EF monitoring in research and clinical settings in which an aortic catheter is employed.

Inhibition of xanthine oxidase improves myocardial contractility in patients with ischemic cardiomyopathy

Reactive oxygen species, in particular superoxide, have been closely linked to the underlying pathophysiology of ischemic cardiomyopathy: superoxide not only mediates mechanoenergetic uncoupling of the myocyte but also adversely impacts on myocardial perfusion by depleting endothelial-derived nitric oxide bioavailability. Xanthine oxidase generates superoxide upon oxidation of hypoxanthine and xanthine and has been detected in cardiac myocytes and coronary endothelial cells of patients with ischemic heart disease. Here we investigated the effects of oxypurinol, a xanthine oxidase inhibitor, on myocardial contractility in patients with ischemic cardiomyopathy. Twenty patients (19 males, 66+/-8 years) with stable coronary disease, severely suppressed systolic function (left ventricular ejection fraction 22+/-2%), and nonelevated uric acid plasma levels received a single intravenous dose of oxypurinol (400 mg). Cardiac MRI studies, performed before and 5.2+/-0.9 h after oxypurinol administration, revealed a reduction in end-systolic volumes (-9.7+/-4.2%; p=0.03) and an increase in left ventricular ejection fraction (+17.5+/-5.2%; p=0.003), whereas 6 patients (6 males, 63+/-3.8 years, ejection fraction 26+/-5%) who received vehicle only did not show significant changes in any of the parameters studied. Oxypurinol improves left ventricular function in patients with ischemic cardiomyopathy. These results underscore the significance of reactive oxygen species as important pathophysiological mediators in ischemic heart failure and point toward xanthine oxidase as an important source of reactive species that serve to modulate the myocardial redox state in this disease.

Thick Maximum Intensity Projections for the Assessment of Left Ventricular Function With 64-Slice Computed Tomography

OBJECTIVE

The objective of this study was to assess the accuracy of thick maximum intensity projections (MIP) from computed tomography (CT) data sets mimicking projection images from biplane ventriculography for evaluation of left ventricular (LV) parameters.

MATERIALS AND METHODS

Fifty-eight patients underwent 64-slice CT. Multiphase images were reconstructed in 10% steps of the RR interval. MIP images (70-mm thickness) of the contrast-enhanced LV in fixed 30 degrees right anterior oblique (RAO)/60 degrees left anterior oblique (LAO) and in adapted short-/long-axis planes were reconstructed. LV parameters were calculated using the area-length method formula. Three-dimensional assessment with semiautomated software served as reference standard.

RESULTS

Use of thick MIP reconstructions had a high intermethod reliability (86-94%) compared with the 3-dimensional approach. Smaller measurement errors were found for thick MIP reconstructions in adapted short-/long-axis planes. A significant projection error (3.0%, P < 0.001) of thick MIP reconstructions was found using fixed 30 degrees RAO/60 degrees LAO compared with adapted short-/long-axis reconstructions.

CONCLUSION

Thick MIP reconstructions with adapted short-/long-axis planes allow an accurate assessment of LV parameters compared with the established 3-dimensional method.

The right ventricle in congenital heart disease

In patients with congenital heart disease the right ventricle (RV) may support the pulmonary (subpulmonary RV) or the systemic circulation (systemic RV). During the last 50 years evidence is accumulating that RV dysfunction develops in many of these patients and leads to considerable morbidity and mortality. Therefore RV function in certain groups of congenital heart disease patients needs close surveillance and timely and appropriate intervention to optimise outcomes. Despite major progress being made, assessing the RV either in the subpulmonary or the systemic circulation remains challenging, often requiring a multi-imaging approach and expertise (echocardiography, magnetic resonance imaging, nuclear and occasionally invasive assessment with angiography). This review discusses the implications of volume and pressure loading of the RV in the context of congenital heart disease and describes the most relevant imaging modalities for monitoring RV function.

Comparing cardiac ejection fraction estimation algorithms without a gold standard

RATIONALE AND OBJECTIVES

Imaging and estimation of left ventricular function have major diagnostic and prognostic importance in patients with coronary artery disease. It is vital that the method used to estimate cardiac ejection fraction (EF) allows the observer to best perform this task. To measure task-based performance, one must clearly define the task in question, the observer performing the task, and the patient population being imaged. In this report, the task is to accurately and precisely measure cardiac EF, and the observers are human-assisted computer algorithms that analyze the images and estimate cardiac EF. It is very difficult to measure the performance of an observer by using clinical data because estimation tasks typically lack a gold standard. A solution to this "no-gold-standard" problem recently was proposed, called regression without truth (RWT).

MATERIALS AND METHODS

Results of three different software packages used to analyze gated, cardiac, and nuclear medicine images, each of which uses a different algorithm to estimate a patient's cardiac EF, are compared. The three methods are the Emory method, Quantitative Gated Single-Photon Emission Computed Tomographic method, and the Wackers-Liu Circumferential Quantification method. The same set of images is used as input to each of the three algorithms. Data were analyzed from the three different algorithms by using RWT to determine which produces the best estimates of cardiac EF in terms of accuracy and precision.

RESULTS AND DISCUSSION

In performing this study, three different consistency checks were developed to ensure that the RWT method is working properly. The Emory method of estimating EF slightly outperformed the other two methods. In addition, the RWT method passed all three consistency checks, garnering confidence in the method and its application to clinical data.

Continuous left ventricular ejection fraction monitoring by central aortic pressure waveform analysis

Left ventricular ejection fraction (EF) is perhaps the most clinically significant index of global ventricular function. EF is measured in clinical practice via imaging methods such as echocardiography. However, these methods generally require a well-trained operator and expensive capital equipment. Thus, EF measurements are only obtained in the clinical setting and are usually made few and far between. To expand the measurement of this critical hemodynamic variable, our overarching hypothesis is that EF may be continuously (i.e., automatically) monitored by mathematical analysis of routinely measured blood pressure waveforms. Here, we introduce a novel technique for estimating the absolute EF by model-based analysis of only a central aortic pressure (CAP) waveform. We then demonstrate the validity of the technique with respect to five conscious dogs in which reference EF was independently measured before and after chronic pacing induced heart failure. With further successful testing, the technique may potentially be utilized for continuous EF monitoring in research and clinical settings in which an aortic catheter is employed as well as for ambulatory EF monitoring in conjunction with recently developed implantable devices for measuring CAP.

Quantitative estimation of left ventricular ejection fraction from mitral valve E-point to septal separation and comparison to magnetic resonance imaging

This study tested the hypothesis that the mitral valve E point-to-septal separation (EPSS) can be used to quantify the left ventricular (LV) ejection fraction (EF) on a continuous scale rather than simply as "normal" or "reduced." After excluding 5 patients with mitral valve prostheses, asymmetric septal hypertrophy, or significant aortic insufficiency, EPSS was measured in 42 patients by 3 independent observers on a cardiac magnetic resonance image identical to the echocardiographic parasternal long-axis view. In each patient, the reference standard LVEF was calculated from the magnetic resonance short-axis cross-sectional stack images by Simpson's rule and ranged from 11% to 72%. For all 42 patients, linear regression revealed the relation magnetic resonance imaging (MRI) LVEF = 75.5 - 2.5. EPSS (millimeters). Correlation between EPSS and the MRI LVEF for the 3 observers agreed closely, ranging from r = 0.78 to r = 0.82 (SEE 9 to 10), with similar regression coefficients. After blinded segmental wall motion scoring of the gated magnetic resonance cine images of the left ventricle in each patient, correlations, SEEs, and regression coefficients were found to be very similar in the 21 patients with the most homogenous wall motion, compared with the 21 patients with the most heterogenous wall motion. In conclusion, clinically useful quantitative prediction of the LVEF as a continuous variable can be obtained from the EPSS with a simple linear regression equation in a substantial portion of patients and may be a useful adjunct for assessment of LV function.

Assessment of left ventricular myocardial function using 16-slice multidetector-row computed tomography: comparison with magnetic resonance imaging and echocardiography

OBJECTIVE

To assess functional parameters using multidetector-row computed tomography (MDCT) and echocardiography and to compare the results with magnetic resonance imaging (MRI).

MATERIALS AND METHODS

End-diastolic-volume (EDV), end-systolic-volume (ESV), stroke-volume (SV), ejection-fraction (EF), and myocardial mass (MM) were calculated based on CT data sets from 52 patients. Echocardiography was performed in 24 of the 52 patients. The results from MDCT and echocardiography were compared with MRI.

RESULTS

A strong correlation between MDCT and MRI (r=0.66-0.90) was found for all parameters. Echocardiography revealed a low or moderate correlation (0.05-0.59). Compared to MRI the average differences with MDCT were for EDV 15.1 ml, ESV 10.6 ml, SV 4.5 ml, EF 1.8%, and MM 8.2 g, for EDV determined by echocardiography 36.2 ml, ESV 6.8 ml, and EF 13.9%. Bland-Altman analysis revealed acceptable limits of agreement between MRI and MDCT.

CONCLUSIONS

MDCT enables reliable quantification of left ventricular function. Echocardiography was found to have only a moderate agreement of functional parameters with MRI.

Two-phase reconstruction for the assessment of left ventricular volume and function using retrospective ECG-gated MDCT: comparison with echocardiography

OBJECTIVE

The aims of our study were to investigate the clinical feasibility of a two-phase reconstruction method based on ECG to evaluate left ventricular (LV) volume and function using cardiac MDCT and to compare these results with those from echocardiography.

SUBJECTS AND METHODS

The LV end-diastolic and end-systolic volumes, stroke volume, and ejection fraction were measured using two different methods of cardiac MDCT in 19 patients who had undergone cardiac MDCT and echocardiography. The first was a two-phase reconstruction method based on retrospective ECG-triggering: The end-systolic phase was reconstructed when the reconstruction window was located halfway in the ascending T wave on ECG, and the end-diastolic phase was reconstructed when the reconstruction window was located at the starting point of the QRS complex on ECG. The second was a multiphase reconstruction method: 20 series of images were reconstructed at every 5% throughout the cardiac cycle. The LV volumes and function determined by the two reconstruction methods were compared. The results measured by cardiac MDCT were compared with those obtained by echocardiography.

RESULTS

The LV end-diastolic and end-systolic volumes, stroke volume, and ejection fraction measured by the two-phase reconstruction method correlated well with those measured by the multiphase reconstruction method (r = 0.984, 0.978, 0.969, 0.969, respectively). There were no significant differences between the results of the two different reconstruction methods (p > 0.05). The LV volumes showed moderate to good correlation between cardiac MDCT and echocardiography (0.766 < r < 0.940). Ejection fraction measured by cardiac MDCT yielded a significant overestimation of 2.9% +/- 8.7% (mean +/- SD) compared with that measured by echocardiography.

CONCLUSION

A two-phase reconstruction method on cardiac MDCT is relatively simple and can provide an objective standard for reconstructing the appropriate image sets for end-diastole and end-systole without the need to review serial preview images.

Heart failure after myocardial infarction: clinical presentation and survival

OBJECTIVES

To characterize the presentation and outcome of patients with heart failure (HF) after myocardial infarction (MI) according to left ventricular ejection fraction (LVEF) and test the hypothesis that the outcome of HF did not change over time.

BACKGROUND

Little is known about the presentation and outcome of HF post-MI and how these may have changed over time.

METHODS

Using the Rochester Epidemiology Project, all residents of Olmsted County, Minnesota who experienced an incident MI between 1979 and 1998 were identified; MI and HF were validated using standardized criteria. Subjects were followed through their community medical record.

RESULTS

Between 1979 and 1998, 1915 patients with incident MI and no prior history of HF were identified. Of these, 791(41%) experienced new onset HF as defined by Framingham criteria during 6.6+/-5.0 years of follow-up. Forty-seven percent were men, mean age was 73+/-12 years. Forty-four percent had impaired LVEF, 18% preserved LVEF and 38% had no LVEF measurement within 60 days after the HF event. Median survival after HF onset was 4 years and at 5 years after HF onset, only 45% were alive. Older age, male sex, comorbidity, hypertension and no LVEF assessment were associated with increased risk of death, however, patients with impaired LVEF had the worst outcome. Over time, survival did not improve (HR for year: 1.00; 95% CI 0.99, 1.02; P=0.919) even after adjustment for baseline characteristics.

CONCLUSION

In this geographically defined cohort of patients with MI, new onset HF after the MI was frequent. When measured, LVEF was most frequently reduced, consistent with systolic heart failure. Mortality was high and did not decline over time and death was independently associated with male sex, older age, hypertension and comorbidity. It also differed according to LVEF, which was inconsistently ascertained in this setting, potentially representing practice opportunities.

Evaluation of global left ventricular myocardial function with electrocardiogram-gated multidetector computed tomography: comparison with magnetic resonance imaging

RATIONALE AND OBJECTIVES

Electrocardiogram-gated 3D volume data from multidetector computed tomography coronary angiography (MDCT-CA) enable image reconstruction in any phase of the cardiac cycle. The objective was to determine left ventricular (LV) function parameters by MDCT in comparison to cine magnetic resonance imaging (MRI).

METHOD

Thirty patients with known or suspected coronary artery disease (CAD) underwent MDCT-CA. From multiplanar reformations in short axis orientation end-diastolic and end-systolic LV volumes (LVEDV, LVESV) were determined to calculate LV stroke volume and ejection fraction (LVSV, LVEF) and compared with MRI measurements.

RESULTS

LVEDV (147 +/- 27 mL) and LVESV (65 +/- 22 mL) determined by MDCT correlated well to the respective MRI measurements (LVEDV 133 +/- 27 mL, r = 0.80, P < 0.001; LVESV 48 +/- 19 mL, r = 0.89, P < 0.001). LVSV (MDCT 82 +/- 15 mL; MRI 85 +/- 17 mL; r = 0.77, P < 0.001) and LVEF (MDCT 56 +/- 9%; MRI 65 +/- 8%; r = 0.85, P < 0.001) showed a good correlation as well. LVEF was significantly underestimated by MDCT (-8.5 +/- 4.7%, P < 0.001).

CONCLUSIONS

Initial experience in patients evaluated for CAD shows that spiral MDCT studies may provide LV functional data in good correlation to Cine MRI.

Visual quantitative estimation: semiquantitative wall motion scoring and determination of ejection fraction

Ejection fraction (EF) is the most commonly used parameter of left ventricular (LV) systolic function and can be assessed by echocardiography. Quantitative echocardiography is time consuming and is as accurate as visual estimation, which has significant variability. We hypothesized that each echocardiographer has developed a mental set of guidelines that relate to how much individual segment shortening constitutes normal function or hypokinesis of varying extents. We determined the accuracy of applying these guidelines to an accepted technique of EF determination using a retrospective analysis of consecutive two-dimensional echocardiographic studies performed on patients who had radioventriculography (RVG) within 48 hours. Using a 12 segment model, we scored each segment at the base and mid-ventricular level based on segmental excursion and thickening. The apex was scored similarly but with 1/3 of the value based on a cylinder-cone model. EF was determined from the sum of segment scores and was estimated visually. We termed this approach visual quantitative estimation (VQE). We correlated the EF derived from VQE and visual estimation with RVG EF. In the training set, VQE demonstrated a strong correlation with RVG (r = 0.969), which was significantly greater than visual estimation (r = 0.896, P < 0.01). The limits of agreement for VQE (+12% to -7%) were similar to the limits of RVG agreement with contrast ventriculography (+10% to -11%) with similar intraobserver and interobserver variabilities. Similar correlation was noted in the prediction set between VQE and RVG EF (r = 0.967, P < 0.001). We conclude that VQE provides highly correlated estimates of EF with RVG.

Electrocardiographic findings in naturally acquired chagasic heart disease in nonhuman primates

The significance of electrocardiographic (ECG) changes described in animals with Chagas' disease is questionable in view that other non-invasive comparisons have been lacking. 12-lead ECG and two-dimensional echocardiography (echo) was performed in 17 seropositive and 13 seronegative baboons. Similar to humans, a wide variety of ECG outcomes were observed in the infected animals. Standard ECG measurements were not different between groups. Five seropositive (29%) and 3 seronegative (23%) animals had low voltage; 4 seropositives (24%) and 2 (15%) seronegatives had tall P-waves. Precordial Q waves were seen in 10 seropositives (59%) and in 7 (54%) seronegatives without septal abnormalities on two-dimensional echo. One seropositive animal had a 2(nd) degree (Wenckebach) AV block and left anterior fascicular block. Most animals in both groups had diffuse T-wave abnormalities. Echo evidence of systolic dysfunction was found in 4 seropositives and in none of the controls; thus, chagasic heart disease was present in 24% of naturally infected baboons. Since most non-human primates, irrespective of their serology, have diffuse, nonspecific ECG changes not necessarily diagnostic of myocardial disease, two-dimensional echo should be added to their non-invasive assessment.

Objective comparison of quantitative imaging modalities without the use of a gold standard

Imaging is often used for the purpose of estimating the value of some parameter of interest. For example, a cardiologist may measure the ejection fraction (EF) of the heart in order to know how much blood is being pumped out of the heart on each stroke. In clinical practice, however, it is difficult to evaluate an estimation method because the gold standard is not known, e.g., a cardiologist does not know the true EF of a patient. Thus, researchers have often evaluated an estimation method by plotting its results against the results of another (more accepted) estimation method, which amounts to using one set of estimates as the pseudogold standard. In this paper, we present a maximum-likelihood approach for evaluating and comparing different estimation methods without the use of a gold standard with specific emphasis on the problem of evaluating EF estimation methods. Results of numerous simulation studies will be presented and indicate that the method can precisely and accurately estimate the parameters of a regression line without a gold standard, i.e., without the x axis.

Estimation in medical imaging without a gold standard

RATIONALE AND OBJECTIVES

In medical imaging, physicians often estimate a parameter of interest (eg, cardiac ejection fraction) for a patient to assist in establishing a diagnosis. Many different estimation methods may exist, but rarely can one be considered a gold standard. Therefore, evaluation and comparison of different estimation methods are difficult. The purpose of this study was to examine a method of evaluating different estimation methods without use of a gold standard.

MATERIALS AND METHODS

This method is equivalent to fitting regression lines without the x axis. To use this method, multiple estimates of the clinical parameter of interest for each patient of a given population were needed. The authors assumed the statistical distribution for the true values of the clinical parameter of interest was a member of a given family of parameterized distributions. Furthermore, they assumed a statistical model relating the clinical parameter to the estimates of its value. Using these assumptions and observed data, they estimated the model parameters and the parameters characterizing the distribution of the clinical parameter.

RESULTS

The authors applied the method to simulated cardiac ejection fraction data with varying numbers of patients, numbers of modalities, and levels of noise. They also tested the method on both linear and nonlinear models and characterized the performance of this method compared to that of conventional regression analysis by using x-axis information. Results indicate that the method follows trends similar to that of conventional regression analysis as patients and noise vary, although conventional regression analysis outperforms the method presented because it uses the gold standard which the authors assume is unavailable.

CONCLUSION

The method accurately estimates model parameters. These estimates can be used to rank the systems for a given estimation task.

Cardiac function: MR evaluation in one breath hold with real-time true fast imaging with steady-state precession

In 12 healthy volunteers and eight patients with cardiac disease, cine magnetic resonance (MR) imaging in the heart was performed with real-time true fast imaging with steady-state precession (FISP), which permitted evaluation of the entire left ventricle in one breath hold (91 msec per frame, 13 frames per section position, nine short-axis section positions per breath hold). Contrast-to-noise ratios (CNRs) and left ventricular mass and function measurements with this technique were compared in all subjects with single-section true FISP imaging and, in the volunteers only, with segmented fast low-angle shot (FLASH) MR imaging. Myocardium-to-blood CNR was significantly higher for both true FISP sequences compared with the FLASH sequence. Measurements of resting left ventricular function with real-time true FISP imaging were comparable with those derived from a series of separate breath-hold single-section true FISP acquisitions.

Measurement of left ventricular dimensions and function in patients with dilated cardiomyopathy

Studies on medical therapy in heart failure are focused on changes of left ventricular (LV) dimensions and function. These changes may be small, requiring a large study group. We measured LV parameters (LV volumes, LV ejection fraction (LV-EF), and left ventricular mass (LVM)) with two-dimensional echocardiography (2D-echo) and magnetic resonance imaging (MRI) in 50 patients. Based on the difference between the measurements, we determined the variance of the results and calculated the sample sizes needed to detect changes of baseline values. For the calculated and measured parameters we found significant differences between the two techniques: LV-EF and LVM were higher in 2D-echo, and LV dimensions were comparable. The sample size to detect relevant changes from baseline with MRI was significantly (P < 0.01) smaller than in 2D-echo. We conclude that MRI is superior in clinical studies on left ventricular dimensional and functional changes, since measurements are more reproducible and the required sample size is substantially smaller, thereby reducing costs.

Accurate measures of left ventricular ejection fraction using electron beam tomography: a comparison with radionuclide angiography, and cine angiography

BACKGROUND

Quantitative determination of ejection fraction is predicated on precise measurement of end-diastolic and end-systolic volumes of the left ventricle. Contrast enhanced electron beam tomography (EBT), with excellent temporal and spatial resolution, has the potential for highly accurate measures of ejection fraction.

METHODS

EBT protocol used a short axis scan of the left ventricle (8-12 levels, apex to base) during infusion of iodinated contrast. To assess the accuracy of the measured left ventricular ejection fraction (LVEF), we compared EBT with first-pass radionuclide angiography (RNA) and cine angiography (CINE).

RESULTS

A total of 41 patients (26 men and 15 women) underwent all three tests within 1 week. Resting ejection fraction using each modality was assessed in a linear regression model to assess inter-test correlation with the other two modalities. Correlation between CINE and EBT was high (r = 0.90, intercept 4.67, p < 0.001). Similarly, correlation of CINE and RNA (r = 0.87, intercept -5.48, p < 0.001) and between EBT and RNA (r = 0.87, intercept -4.6, p < 0.001) were high. In a subset of those patients with LVEF < or = 40%, correlation was consistently high between EBT and CINE. However, correlations were poor for the comparisons between RNA and CINE (r = 0.40), and between the RNA and EBT (r = 0.47). The mean differences of measured ejection fractions between each of the imaging modality were small. However, there was only modest agreement between each of the comparisons as measured using 95% confidence interval (CI) on Bland-Altman plots.

CONCLUSION

These data indicate that the LVEF results are comparable among EBT, RNA, and CINE and can be used interchangeably to assess ventricular function for LVEF > 40%. For LVEF < or = 40%, we demonstrated some disparate results between cine angiography and RNA and between EBT and RNA, indicating that CINE or EBT may provide more accurate assessment.

Assessment of cardiac function: magnetic resonance and computed tomography

A complete cardiac study requires both anatomic and physiologic evaluation. Cardiac function can be evaluated noninvasively by magnetic resonance imaging (MRI)or ultrafast computed tomography (CT). MRI allows for evaluation of cardiac function by cine gradient echo imaging of the ventricles and flow analysis across cardiac valves and the great vessels. Cine gradient echo imaging is useful for evaluation of cardiac wall motion, ventricular volumes and ventricular mass. Flow analysis allows for measurement of velocity and flow during the cardiac cycle that reflects cardiac function. Ultrafast CT allows for measurement of cardiac indices similar to that provided by gradient echo imaging of the ventricles.

Comparison of measurement of left ventricular ejection fraction by Tc-99m sestamibi first-pass angiography with electron beam computed tomography in patients with anterior wall acute myocardial infarction

The goal of this study was to compare measurements of left ventricular (LV) ejection fraction (EF) by first-pass radionuclide angiography ("first-pass angiography") using technetium-99m (Tc-99m) sestamibi with those by contrast-enhanced electron beam computed tomography ("electron beam tomography") as a reference technique in patients with an anterior wall acute myocardial infarction (AMI). Twenty-five patients with first Q-wave anterior wall AMI underwent paired electron beam tomographic and first-pass angiographic studies (mean, 1 day apart). Fourteen patients had 2 sets of measurements of the LVEF obtained by both methods (separated by at least 6 weeks), for a total of 39 paired measurements. LVEF by electron beam tomography was calculated from absolute systolic and diastolic LV chamber volumes. LV volumes by electron beam tomography were 199 +/- 51 ml at end-diastole and 111 +/- 42 ml at end-systole. Mean LVEF was 45 +/- 11% by first-pass tomography and 46 +/- 9% by electron beam tomography. The linear correlation coefficient between both methods was 0.82 (p <0.0001), with slope = 1.0, y-intercept = -1.1, and SEE = 6.1. The mean difference between the 2 methods was -0.7 +/- 6.0 EF units (p = 0.75). The correlation between the differences and means of both methods was 0.34 (p = 0.04), indicating a trend for first-pass angiography to overestimate LVEF in the higher range. LVEFs measured by first-pass angiography in patients with abnormal LV geometry and contraction patterns caused by anterior wall AMI agree well with those measured by electron beam tomography in the clinically relevant range.