Investigación reciente

    NMR Biomed.

    Cine-MRI versus two-dimensional echocardiography to measure in vivo left ventricular function in rat heart.

    Stuckey, DJ, Carr, CA, et al. (2008).
    Contact: Cardiac Metabolism Research Group, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.

    Two-dimensional echocardiography is the most commonly used non-invasive method for measuring in vivo cardiac function in experimental animals. In humans, measurements of cardiac function made using cine-MRI compare favourably with those made using echocardiography. However, no rigorous comparison has been made in small animals. Here, standard short-axis two-dimensional (2D) echocardiography (2D-echo) and cine-MRI measurements were made in the same rats, both control and after chronic myocardial infarction. Correlations between the two techniques were found for end diastolic area, stroke area and ejection fraction, but cine-MRI measurements of ejection fraction were 12 +/- 6% higher than those made using 2D-echo, because of the 1.8-fold higher temporal resolution of the MRI technique (4.6 ms vs 8.3 ms). Repeated measurements on the same group of rats over several days showed that the cine-MRI technique was more reproducible than 2D-echo, in that 2D-echo would require five times more animals to find a statistically significant difference. In summary, caution should be exercised when comparing functional results acquired using short-axis 2D-echo vs cine-MRI. The accuracy of cine-MRI allows identification of alterations in heart function that may be missed when using 2D-echo.
    Copyright (c) 2008 John Wiley & Sons, Ltd.

    Am Heart J 155(5): 946-53.

    How accurately, reproducibly, and efficiently can we measure left ventricular indices using M-mode, 2-dimensional, and 3-dimensional echocardiography in children?

    Lu, X, Xie, M, et al. (2008)
    Contact: The Lillie Frank Abercrombie Section of Cardiology, Department of Pediatrics, Baylor College of Medicine and Texas Children's Hospital, Houston, TX 77030, USA.

    BACKGROUND: Measurements of left ventricular (LV) size, mass, and function are the most common and important tasks for echocardiography in clinical practice and research in children with congenital and acquired heart diseases. There are little data to compare the utility of M-mode (MM), 2-dimensional (2D), and 3-dimensional (3D) echocardiographic techniques for quantification of LV indices. The objective of the study was to assess the accuracy, reproducibility, and efficiency of these echocardiographic methods for measurement of LV indices in children.

    METHODS: A prospective study was conducted in 20 consecutive children (mean 10.6 +/- 2.8 years, 11 male and 9 female subjects) using conventional MM, 2D, and real-time 3D echocardiography (RT3DE). A Sonos 7500 system (Philips Medical Systems, Andover, MA) was used. M-mode and 2DE measurements were made according to the American Society of echocardiography recommendations. To include the entire LV for volumetric measurement, full-volume 3D data sets were acquired from 4 electrocardiogram gated subvolumes. The 3DE measurements were made off-line manually using 4-plane and 8-plane algorithms by 4D Echo-View (TomTec Imaging Systems, Munich, Germany) and a semiautomated algorithm by QLAB (Philips Medical Systems). Magnetic resonance imaging studies were also performed to determine the LV indices by a disk summation method based on the Simpson principle.

    RESULTS: The correlation and agreement between MM, 2D, and RT3D echocardiography and magnetic resonance imaging measurements are good (r = 0.81-0.97) for the 3 methods. The correlation was superior for RT3DE compared with 2DE and MM. The correlation and agreement were similar for the three 3DE methods. The intra- and interobserver variabilities ranged from MM (4.3%-4.8% and 7.0%-8.7%), 2DE (3.3%-4.5% and 5.5%-7.3%), and 3DE (0.4%-2.3%, and 0.2%-4.8%). The total time (acquisition and analysis) used for MM measurements was the least compared with 2DE and 3DE. The total time for 3DE using the semiautomated algorithms was not significantly different compared with that for 2DE.

    CONCLUSIONS: Our study showed that MM provides the most efficient assessment of LV indices but is the least accurate and reproducible technique compared with 2DE and 3DE. Three-dimensional echocardiography using both automated and manual analysis algorithm is superior to MM and 2DE for measurements of LV indices, and the automated 3DE algorithm is as efficient as 2DE. Therefore, 3DE using the automated algorithm is the method of choice for quantification of LV indices.

    Int J Cardiovasc Imaging.

    Accuracy of guideline recommendations for two-dimensional quantification of the right ventricle by echocardiography.

    Lai, WW, Gauvreau, K, et al. (2008)
    Contact: Department of Cardiology, Children's Hospital Boston, 300 Longwood Avenue, Boston, MA, 02115, USA.

    BACKGROUND: The accuracy of the guidelines of the American Society of Echocardiography (ASE) for the two-dimensional (2D) quantitative assessment of right ventricular (RV) size and function has not been evaluated against MRI-derived RV volumes in patients with congenital heart disease and RV volume overload.

    METHODS: Three groups of patients were studied: a normal RV group (Group I, n = 31), a repaired tetralogy of Fallot group (Group II, n = 33), and an unrepaired atrial septal defect and/or partially anomalous pulmonary venous connection group (Group III, n = 23). Recommended 2D linear and cross-sectional area measurements were made on clinical echocardiographic and MRI studies performed less than 6 months apart.

    RESULTS: Most 2D RV parameters were smaller by echocardiography versus MRI. There was weak correlation between 2D RV measurements by echocardiography and MRI-derived RV volumes (Group I: r = 0.15-0.54, Group II: r = 0.33-0.61, Group III: r = 0.32-0.85), and only modest improvement when the same 2D measurements were performed by MRI (Group I: r = 0.37-0.61, Group II: r = 0.44-0.69, Group III: r = 0.28-0.74). The difference between 2D RV measurements by echocardiography and MRI-derived RV volumes was more pronounced in the RV volume overload groups.

    CONCLUSIONS: The correlation between currently recommended 2D RV measurements by echocardiography and MRI-derived RV volumes was weak, and improved only modestly when MRI was used to make the same 2D measurements. Moreover, 2D echocardiographic assessment of the RV appears to be less accurate in patients with congenital heart disease and a dilated RV.


    Utility of Right Ventricular Tissue Doppler Imaging: Correlation with Right Heart Catheterization.

    Rajagopalan, N, Simon, MA, et al. (2008).
    Contact: Cardiovascular Institute, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA.

    OBJECTIVES: The objective of this study was to correlate tissue Doppler imaging of the right ventricle (RV) with pulmonary hemodynamics in patients referred for right heart catheterization.

    METHODS: Seventy subjects (mean age 54 +/- 13; 35 males) prospectively underwent tissue Doppler imaging of the RV and right heart catheterization within 1 day of each other. Peak systolic velocity and strain were measured at the RV free wall and correlated with pulmonary hemodynamics.

    RESULTS: RV myocardial velocity demonstrated no correlation with any hemodynamic variable. While RV strain demonstrated significant correlation with cardiac index (r =-0.61; P < 0.001), correlations with transpulmonary gradient (r = 0.26; P < 0.05) and pulmonary vascular resistance (r = 0.30; P < 0.05) were weaker. Subgroup analysis revealed that in patients with left ventricular systolic dysfunction (n = 31), RV strain showed no correlation with any hemodynamic variable. In patients with normal left ventricular systolic function (n = 39), correlations were significant between RV strain and mean pulmonary artery pressure (r = 0.59; P < 0.001), pulmonary vascular resistance (r = 0.60; P < 0.001), and cardiac index (r =-0.67; P < 0.001).

    CONCLUSIONS: RV myocardial strain correlates significantly with pulmonary hemodynamics in patients with pulmonary hypertension and normal left ventricular function. However, there is no correlation with RV performance in patients with left ventricular dysfunction.


    High-speed digital scan converter for high-frequency ultrasound sector scanners.

    Chang, JH, Yen, JT, et al. (2008).
    Contact: NIH Resource Center for Medical Ultrasonic Transducer Technology, Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, United States.

    This paper presents a high-speed digital scan converter (DSC) capable of providing more than 400 images per second, which is necessary to examine the activities of the mouse heart whose rate is 5-10 beats per second. To achieve the desired high-speed performance in cost-effective manner, the DSC developed adopts a linear interpolation algorithm in which two nearest samples to each object pixel of a monitor are selected and only angular interpolation is performed. Through computer simulation with the Field II program, its accuracy was investigated by comparing it to that of bilinear interpolation known as the best algorithm in terms of accuracy and processing speed. The simulation results show that the linear interpolation algorithm is capable of providing an acceptable image quality, which means that the difference of the root mean square error (RMSE) values of the linear and bilinear interpolation algorithms is below 1%, if the sample rate of the envelope samples is at least four times higher than the Nyquist rate for the baseband component of echo signals. The designed DSC was implemented with a single FPGA (Stratix EP1S60F1020C6, Altera Corporation, San Jose, CA) on a DSC board that is a part of a high-speed ultrasound imaging system developed. The temporal and spatial resolutions of the implemented DSC were evaluated by examining its maximum processing time with a time stamp indicating when an image is completely formed and wire phantom testing, respectively. The experimental results show that the implemented DSC is capable of providing images at the rate of 400 images per second with negligible processing error.

    Cardiovasc Ultrasound 6: 2.

    Usefulness and limitations of transthoracic echocardiography in heart transplantation recipients.

    Mondillo, S, Maccherini, M, et al. (2008).
    Contact: Cardiologia Universitaria, Universita di Siena, Siena, Italy.

    Transthoracic echocardiography is a primary non-invasive modality for investigation of heart transplant recipients. It is a versatile tool which provides comprehensive information about cardiac structure and function. Echocardiographic examinations can be easily performed at the bedside and serially repeated without any patient's discomfort. This review highlights the usefulness of Doppler echocardiography in the assessment of left ventricular and right ventricular systolic and diastolic function, of left ventricular mass, valvular heart disease, pulmonary arterial hypertension and pericardial effusion in heart transplant recipients. The main experiences performed by either standard Doppler echocardiography and new high-tech ultrasound technologies are summarised, pointing out advantages and limitations of the described techniques in diagnosing acute allograft rejection and cardiac graft vasculopathy. Despite the sustained efforts of echocardiographic technique in predicting the biopsy state, endocardial myocardial biopsies are still regarded as the gold standard for detection of acute allograft rejection. Conversely, stress echocardiography is able to identify accurately cardiac graft vasculopathy and has a recognised prognostic in this clinical setting. A normal stress-echo justifies postponement of invasive studies. Another use of transthoracic echocardiography is the monitorisation and the visualisation of the catheter during the performance of endomyocardial biopsy. Bedside stress echocardiography is even useful to select appropriately heart donors with brain death. The ultrasound monitoring is simple and effective for monitoring a safe performance of biopsy procedures.

    Crit Care Med 36(1 Suppl): S28-39.

    Imaging studies in patients with heart failure: current and evolving technologies.

    Glassberg, H, Kirkpatrick, J, et al. (2008).
    Contact: Cardiovascular Medicine Division, Hospital of the University of Pennsylvania, Philadelphia, PA, USA.

    Technological advances continue to expand the clinical role of echocardiography in the intensive care unit, particularly in patients with heart failure. It has many advantages over tomographic techniques such as echo cardiac magnetic resonance imaging and cardiac computed tomography, can provide rapid bedside cardiac assessment, and facilitate emergent decision-making for critically ill patients. Image quality problems in the intensive care setting have largely been overcome by the use of harmonic imaging, contrast opacification, and when indicated, transesophageal echocardiography. Newer techniques promise to advance the scope and prognostic power of echocardiography, and to expand the portability and availability of this tool.

    Echocardiography 24(5): 522-32.

    Right ventricular tissue Doppler and strain imaging: ready for clinical use?

    Gondi, S and Dokainish, H (2007).
    Contact: Department of Medicine, Section of Cardiology, Baylor College of Medicine, Houston, Texas 77030, USA.

    Although tissue Doppler (TD) imaging of the left ventricle is now commonly used in clinical settings, TD imaging of the right ventricle (RV) is not routinely practiced. Yet, there are significant data on clinical uses of RV TD imaging, including established normal values using both color and spectral TD. In acute left ventricular (LV) inferior wall myocardial infarction, depressed RV TD velocities have been shown to correlate with the presence of RV impairment, and with patient outcome. In patients with LV heart failure, TD imaging has been correlated to RV ejection fraction by radionuclide angiography, and is an independent predictor of outcome. In patients with congenital heart disease, RV TD has been especially valuable for assessing RV function, and has been correlated to invasive hemodynamic indices, and RV ejection fraction by magnetic resonance imaging. The RV performance (Tei) index has been calculated and validated using TD-derived, rather than conventional pulsed Doppler time intervals. RV TD indices have been shown to be useful in the detection of subclinical and clinical disease in morbid obesity, chronic pulmonary, and systemic disease. TD-derived RV strain imaging can detect segmental myocardial dysfunction, overcoming limitations to conventional TD imaging resulting from tethering. For both TD velocity and strain imaging, however, appreciation of the limitations of these techniques is necessary for their appropriate use. Given its rapid acquisition times, reproducibility, and ease of addition to standard transthoracic echocardiographic protocols, RV TD and strain imaging are important additional modalities in the comprehensive echo-Doppler assessment of RV function.

    Pediatr Radiol 37(5): 426-36.

    Evaluation of aortic regurgitation in congenital heart disease: value of MR imaging in comparison to echocardiography.

    Ley, S, Eichhorn, J, et al. (2007).
    Contact: Department of Radiology (E010), German Cancer Research Centre (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany.

    BACKGROUND: Evaluation of the severity and the follow-up of aortic insufficiency (AI) are important tasks in paediatric cardiology. Assessment is based on clinical and echocardiographic (ECHO) findings such as the configuration of the valve and the regurgitation fraction (RF).

    OBJECTIVE: The goal of this study was to evaluate MRI compared to ECHO for determination of clinical severity, valve morphology and RF.

    MATERIALS AND METHODS: Thirty patients (age 3-27 years) with mild-to-severe AI were evaluated by clinical examination, ECHO (2-D and Doppler), and MRI at 1.5 T (2-D true-FISP cine short axis, phase-contrast flow in the ascending aorta).

    RESULTS: Both methods identified 13 bicuspid and 17 tricuspid valves. Good correlations between ECHO and cine MRI were found for ventricular mass, stroke volume, and ejection fraction. A good linear correlation was found for the RF determined by ECHO and phase-contrast MRI (r = 0.7). The RF was 6% in mild AI, 17% in moderate AI, and 30% in severe AI. The different severity groups showed significantly different RF and it was possible to discriminate between clinical severity grades (P = 0.01).

    CONCLUSION: ECHO and MRI showed good agreement in evaluating morphology and function of the left ventricle. The clinical severity of the disease can be evaluated correctly using MRI.

    Congenit Heart Dis 2(1): 27-31.

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

    Puchalski, MD, Williams, RV, et al. (2007).
    Contact: Primary Children's Medical Center, University of Utah, Salt Lake City, UT 84113, USA.

    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.

    J Cardiovasc Med (Hagerstown) 8(1): 17-22.

    Echocardiography in congenital heart disease: usefulness, limits and new techniques.

    Pacileo, G, Di Salvo, G, et al. (2007).
    Contact: Paediatric Cardiology, Second University, A.O. Monaldi, Naples, Italy.

    Echocardiography represents the non-invasive tool most commonly used in pediatric cardiology. Indeed, it enables the definition of both the morphological and functional findings in congenital heart disease (CHD), as completely as possible in almost all the cases. In comparison with adult subjects, the echocardiographic evaluation in pediatric patients requires a different approach, providing information on the heart position in the thorax, the atrial situs viscerum, the vein-atrial and the atrio-ventricular connections, the relationship between the ventricles, the ventriculo-arterial connection and the relationship of the great arteries (segmental analysis). In addition, the echocardiographic study should include a non-invasive study of ventricular function, as mandatory to warrant an optimal pre- and postoperative management in patients with CHD. The indices most commonly utilized to assess ventricular mechanics are the 'pump indices' (i.e. ejection fraction or fractional shortening). Unfortunately, they may lead to invalid data, because of their dependence on loading conditions and heart rate. As a consequence, echocardiographic indices should be used (i.e. fiber shortening or rate-corrected velocity of circumferential fiber shortening-end systolic stress relationship), which better reflect the intrinsic myocardial contractility. More recently, evidence is mounting that new echocardiographic techniques (i.e. Doppler myocardial imaging, strain/strain rate and backscatter) may offer new insights in terms of regional functional and textural findings of the myocardium. However, long-term follow-up studies will be necessary to better define their real impact in the clinical setting.

    Int J Cardiol 124(1): 47-56.

    Objective quantification of global and regional left ventricular systolic function by endocardial tracking of contrast echocardiographic sequences.

    Bermejo, J, Timperley, J, et al. (2008).
    Contact: Department of Cardiology, Hospital General Universitario Gregorio Maranon, Madrid, Spain.

    BACKGROUND: Echocardiographic assessment of LV wall motion is still most frequently done visually. This study was designed to validate a new system for semi-automatic quantification of global and regional LV systolic function from contrast-enhanced cross-sectional echocardiograms.

    METHODS: Measurements of LV volumes were validated in 50 patients using magnetic resonance (MR) as reference. The regional identification of the endocardial boundary was validated frame-by-frame against the visually identified border in another 27 patients. Finally, the applicability of the system for quantifying stress-echocardiographic exams was assessed in 52 patients undergoing dobutamine interventions. Echocardiographic sequences were digitally processed using custom-built algorithms, based on local phase feature descriptors, deformable contour fitting, and prospective training.

    RESULTS: Compared to MR, the tracing system showed reasonable accuracy, with relative errors for end-diastolic volume, end-systolic volume, and EF of 21+/-20%, 27+/-33%, and--4+/-18%, respectively. Regional agreement of the instantaneous contours with visually traced borders was within the limits of visual reproducibility. The system was suitable for tracking stress-echo studies from all patients except two (96%). Quantification of regional radial shortening allowed to discriminate segments showing an abnormal regional wall motion with an overall area under the ROC curve of 0.87.

    CONCLUSIONS: A reliable and accurate quantification of LV systolic function can be obtained by processing contrast echocardiograms. Values of LV volumes, ejection fraction, and regional endocardial shortening adequately correlate with currently available reference methods. Readily applicable to baseline and stress studies, endocardial tracking techniques increase the reliability of echocardiography for the assessment of global and regional systolic function.

    J Cardiovasc Pharmacol 51(1): 86-91.

    The acute effect of an echo-contrast agent on right ventricular dimensions and contractility in pigs.

    Bramos, D, Tsirikos, N, et al. (2008).
    Contact: Department of Clinical Therapeutics, Athens Medical School, Alexandra Hospital, Athens, Greece.

    BACKGROUND: The aim of the present study was to examine the effect of the second-generation ultrasound contrast agent (2nd GUCA) SonoVue on right ventricular (RV) dimensions and contractility and to investigate whether a dose-related interaction exists between the contrast agent and RV function.

    METHODS: Twenty-eight pigs were randomly assigned to 3 groups for intravenous administration: a low-dose group (0.5 cc of SonoVue), a high-dose group (1 cc of SonoVue), and a control group (2 cc of normal saline). RV end-diastolic (EDD) and end-systolic dimension (ESD) and pulmonary pressure (PP) were measured, and the fractional shortening (FS%) was calculated before the administration of SonoVue or normal saline and after the return of the RV-EDD or PP to the baseline value. The time to reach maximal RV-EDD or PP value and the time until the return of RV-EDD or PP to the baseline value were also measured.

    RESULTS: Contrast agent infusion was followed by an acute transient increase of RV-EDD, RV-ESD, FS, and PP in both the low-dose and high-dose groups, but the increase was greater in the high-dose group. FS and PP did not change significantly in the control group. A dose-dependent delay in the time from baseline to maximum RV-EDD and PP was detected in the high-dose group (P < 0.001 for both) as well as a delay in the return from maximum to the baseline values (P < 0.001 for both).

    CONCLUSIONS: Administration of the 2nd GUCA SonoVue is associated with an acute, transient, dose-dependent RV dilatation and an increase in pulmonary pressure with a consequent impact on RV contractility.

    Am Heart J 155(1): 161-5.

    Failure of digital echocardiography to accurately diagnose intracardiac shunts.

    Rahmouni, HW, Keane, MG, et al. (2008).
    Contact: Department of Medicine, Cardiovascular Division, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.

    BACKGROUND: Intravenous agitated saline injection during transthoracic echocardiography assists in the detection of right to left intracardiac and intrapulmonary shunts. Whether digital echocardiography offers comparable sensitivity and specificity to analog tape recording to assess shunts is unknown. Technical differences between methods could lead to significant differences in shunt detection.

    METHODS: Agitated saline was injected intravenously at rest and with Valsalva in 189 consecutive patient studies (406 injections). Echocardiographers assessed presence and degree of left ventricle contrast on simultaneously recorded analog tape and digital echocardiography images in blinded fashion.

    RESULTS: Digital echocardiography had low overall sensitivity (rest 0.50, valsalva 0.63, late 0.39) compared to analog tape. Longer clip lengths improved sensitivity for detection of late contrast passage (rest 0.50, valsalva 0.67, late 0.46).

    CONCLUSION: Digital echocardiography saline contrast studies have poor sensitivity for assessment of intracardiac shunts versus analog tape, and increasing clip length only modestly increases sensitivity. Joint Photographic Experts Group digital compression losses may be an important cause of failure to detect intracardiac shunts, including patent foramen ovale.