Vascular endothelial growth factor (VEGF) upregulates BCL-2 and inhibits apoptosis in human and murine mammary adenocarcinoma cells.

Tumour progression is regulated by the balance of proliferation and apoptosis in the tumour cell population. To date, the role of vascular endothelial growth factor (VEGF) in tumour growth has been attributed to the induction of angiogenesis. VEGF has been shown to be a survival factor for endothelial cells, preventing apoptosis by inducing Bcl-2 expression. In both murine (4T1) and human (MDA-MB-231) metastatic mammary carcinoma cell lines, we found that VEGF upregulated Bcl-2 expression and anti-VEGF antibodies reduced Bcl-2 expression. These alterations in Bcl-2 expression were reflected by the levels of tumour cell apoptosis. VEGF resulted in reduced tumour cell apoptosis, whereas its inhibition with anti-VEGF neutralizing antibodies induced apoptosis directly in tumour cells. Therefore, in addition to its role in angiogenesis and vessel permeability, VEGF acts as a survival factor for tumour cells, inducing Bcl-2 expression and inhibiting tumour cell apoptosis.

Differentiation of intracardiac tumors and thrombi by echocardiographic tissue characterization: comparison of an artificial neural network and human observers.

The feasibility of classifying ultrasound images of intracardiac tumors and thrombi with a neural network-based algorithm was compared with the performance of experienced echocardiographers. The neural network used statistical descriptors of the apparent echocardiographic texture of the masses, and the blinded echocardiographers were given photographic prints of enlarged regions of interest without clinical data. The network classified 66% of the images correctly and the echocardiographers, 83%. The network and echocardiographers agreed in 88% of the images. Human observers usually base their classification of intracardiac masses on clinical data. The echocardiographic texture of tumors is quantitatively different from that of thrombi. This difference can be recognized by a neural network and potentially be useful in assisting with the diagnosis when clinical clues are insufficient.

Usefulness of harmonic imaging for left ventricular opacification and endocardial border delineation by optison.

Harmonic and fundamental imaging techniques were directly compared in 20 patients undergoing intravenous contrast echocardiography for enhancement of left ventricular endocardial border definition. Harmonic imaging demonstrated significantly enhanced left ventricular endocardial border detection and improved the duration and intensity of a contrast effect despite a reduced dosing requirement.

Harmonic imaging: echocardiographic enhanced contrast intensity and duration.

The intensity and duration of contrast effect within the left ventricular cavity after an intravenous bolus of Levovist Injection were observed with both harmonic and fundamental imaging in nine patients with known or suspected coronary artery disease. Contrast intensity was assessed by a qualitative grading system (0, none; 1, weak; 2, moderate; 3, good) and by videodensitometric analysis of pixel intensity. Duration of left ventricular contrast effect was determined by measuring time from the initial visual appearance of contrast agent to its disappearance. The mean increase in pixel intensity within the left ventricular cavity from precontrast to peak contrast was significantly greater for second harmonic than for fundamental imaging (25.5 vs 7.1; P < 0.012). The mean contrast intensity qualitative score with harmonic imaging was higher (2.6 +/- 0.73 vs 1.2 +/- 0.44; P < 0.01) and the duration of contrast effect was longer (242 +/- 131 s vs 53 +/- 33 s; P < 0.004). Second harmonic imaging significantly enhanced contrast intensity and prolonged visible duration of contrast effect after a peripheral venous injection of Levovist.

Image enhancement by noncontrast harmonic echocardiography. Part I. Qualitative assessment of endocardial visualization.

OBJECTIVE: To determine whether harmonic imaging--use of signals with frequencies twice that of the transmitted ultrasound to produce ultrasound images--can improve endocardial border definition in patients who have technically difficult echocardiograms. METHODS: We studied 29 patients with technically difficult echocardiograms (nonvisualization of 2 or more endocardial segments in a 16-segment model). Apical long-axis, four-chamber, and two-chamber images were acquired during fundamental imaging (at 2.0 and 3.5 MHz) and second harmonic imaging (3.5-MHz receive mode) in random order. Images were digitally stored and subsequently reviewed blindly for endocardial segment score (0 = not visualized; 1 = adequate; or 2 = excellent) and overall ranking of image quality (1 [best] to 3 [worst]). RESULTS: Mean endocardial segment score was significantly better (P < 0.0001) for harmonic imaging (1.02 +/- 0.36) than for either fundamental mode (0.49 +/- 0.21 and 0.57 +/- 0.27 for the 2.0- and 3.5-MHz images, respectively). The harmonic images were ranked as better (P < 0.0001) than those of either fundamental mode: harmonic mean rank was 1.07 in comparison with 2.67 and 2.26 for the 2.0- and 3.5-MHz fundamental images, respectively. CONCLUSION: Noncontrast harmonic imaging appreciably enhances endocardial definition in patients with technically difficult echocardiographic studies and significantly improves overall image quality.

Image enhancement by noncontrast harmonic echocardiography. Part II. Quantitative assessment with use of contrast-to-speckle ratio.

OBJECTIVE: To ascertain whether "harmonic imaging"--use of ultrasound signals with the frequency twice that of the transmitted signal for ultrasound image generation--can improve image contrast while reducing noise. METHODS: Technically difficult echocardiograms (nonvisualization of 2 or more endocardial segments in a 16-segment model) from 25 patients were analyzed. Corresponding fundamental and harmonic images of the left ventricle in the apical four-chamber, two-chamber, and long-axis views were divided into basal, mid, and apical regions. The difference in image quality between fundamental and harmonic scans was assessed by using the muscle-to-cavity contrast-to-speckle ratio (CSRmc). RESULTS: The mean CSRmc values of pooled data revealed significant image enhancement by harmonic scanning (CSRmc increased from 0.84 to 1.06; P < 0.0001). Regression analysis showed that harmonic imaging improved the CSRmc values in 68% of all scans. Regional analysis indicated the most enhancement in basal regions (CSRmc increased from 0.96 to 1.34; P < 0.0001), followed by the mid (CSRmc increased from 0.84 to 1.04; P < 0.0001) and apical (CSRmc increased from 0.68 to 0.74; P = 0.0138) left ventricular regions. CONCLUSION: Noncontrast harmonic imaging significantly enhances suboptimal echocardiographic images, particularly in the regions distant from the transducer.

Stability of the defibrillation probability curve with the development of ventricular dysfunction in the canine rapid paced model.

Most patients with implantable defibrillators have diminished cardiac function. Progressive heart failure might impair defibrillation efficacy, leading to interpreted device failure. This study sought to determine the effect of ventricular dysfunction on defibrillation energy using a biphasic endocardial system. Eleven dogs were ventricularly paced at 225 pulses/min for 2 weeks to induce ventricular dysfunction, and five control dogs remained unpaced. Dose response defibrillation probability curves were generated for each animal at baseline, after 2 weeks (at which time the pacemakers were turned off in the paced group), and then 1 week later. The defibrillation thresholds, ED20, ED50, and ED80 (the 20%, 50%, and 80% effective defibrillation energies, respectively) were determined for each dog at each study. In the paced dogs, the mean ejection fraction fell from 55% to 25% after pacing (P < 0.0001), and rose to 46% after its discontinuation (P = 0.0002). The defibrillation threshold, ED20, ED50, and ED80 remained unchanged in both the control and paced groups for all three studies, even after adjustment for dog weight or left ventricular mass. Rapid pacing produced no change in left ventricular mass. It induced ventricular cavity dilatation and wall thinning, which had opposing effects on defibrillation energy requirements, resulting in no net change of the ED50 in heart failure. In conclusion, the defibrillation efficacy of a biphasic transvenous system is not changed by the development of heart failure using the rapid paced canine model.

Destruction of contrast microbubbles during ultrasound imaging at conventional power output.

Inhomogenous opacification of cardiac chambers has been frequently observed after intravenous administration of long-persisting echocardiographic contrast agents. We observed this phenomenon to be most pronounced at high acoustic powers with incomplete opacification of the left ventricular apex and left ventricular outflow tract. Reducing the acoustic energy to which the contrast was exposed by decreasing transmit power or intermittently suspending insonification resulted in homogenous opacification of the entire left ventricular cavity. We systematically examined the effect of varying insonification power on the persistence of three investigational ultrasound contrast agents in both in vitro and in vivo models. We found an inverse relationship between the insonifying power and the persistence of the contrast agents. Contrast intensity decay could be reduced either by decreasing exposure to ultrasound by minimizing the transmit power of the system or by intermittently suspending ultrasound generation (triggering). Minimization of ultrasound contrast exposure to ultrasound energy thus improves echocardiographic contrast duration and homogeneity.

Second harmonic imaging of an intravenously administered echocardiographic contrast agent: Visualization of coronary arteries and measurement of coronary blood flow.

OBJECTIVES: This study sought to evaluate the potential of second harmonic contrast echocardiography to assess coronary vasculature. BACKGROUND: Newer transpulmonary ultrasound contrast agents capable of resonance phenomena detected by harmonic imaging may theoretically be able to demonstrate blood flow in the myocardium. METHODS: Transthoracic B-mode images and Doppler were obtained using a prototype second harmonic ultrasound system after femoral vein injection of AF0145 (10 to 40 mg) in 13 closed chest dogs (mean weight 25.6 kg). Coronary Doppler flow was simultaneously invasively measured using an intracoronary flow wire and visually compared with transthoracic Doppler flow. "Noninvasive" coronary vasodilator reserve was determined by measuring the ratio of the Doppler time velocity integral after adenosine to the baseline value and compared with the "invasive" intracoronary determination. RESULTS: Harmonic imaging showed heterogeneous opacification of the myocardium characterized by linear branching structures consistent with intramyocardial coronary arteries, which were not clearly visible during conventional ultrasound imaging. In nine dogs, transthoracic Doppler was performed, and characteristic coronary Doppler flow was observed, identical to the simultaneously observed intracoronary Doppler flow. Intracoronary adenosine (120 to 150 microgram) equally increased intracoronary and transthoracic Doppler flow velocities. The calculated "noninvasive" and "invasive" coronary vasodilator reserve ratios were similar ([mean +/- SD] 3.3 +/- 1.0 and 3.6 +/- 1.2, p = NS), with excellent correlation (r = 0.95, p = 0.0012). CONCLUSIONS: These findings indicate that noninvasive assessment of intramyocardial coronary vasculature and measurement of coronary blood flow reserve are possible using second harmonic contrast echocardiography.

Contrast echocardiography 1996. A review.

Remarkable advances in the field of contrast echocardiography have been made during the last decade. Interest in ultrasound contrast agents that strengthen the backscattered ultrasound signal and improve image display has stimulated further research. Echocardiographic contrast agents providing left ventricular cavity image enhancement after intravenous injection are now available. A role for contrast echocardiography in the assessment of myocardial perfusion has been established within the invasive clinical setting. With the development of newer contrast agents and new ultrasound technology, myocardial perfusion imaging using contrast echocardiography after venous injection is no longer the unattainable "holy grail," but is fast approaching clinical applicability.

Congenital heart disease: wide-field, three-dimensional, and four-dimensional ultrasound imaging.

The next significant advance for cardiovascular ultrasound will be the introduction of clinical three-dimensional (3-D) imaging. With increasing computer power and software and hardware, 3-D ultrasound imaging will become a reality over the next few years. Of all cardiovascular abnormalities, congenital heart disease is one of the most logical entities to lend itself to wide-field and 3-D presentation. Tomographic two-dimensional (2-D) echocardiography has in great part replaced cardiac catheterization as the means of accurately visualizing congenital cardiac defects. However, two distinct limitations exist with current 2-D presentations: (1) limited field of view (ie, 90 degrees sector) and (2) tomographic slices that must be assimilated by the examiner into a 3-D or four-dimensional diagnosis. True 3-D imaging has the ultimate capability of rendering anatomy in a format comparable to looking at the actual cardiac specimen. If electronic rendering were really feasible and of suitable quality, one could envision electronically extracting the heart from a living human and examining abnormalities much as one might examine a cardiac specimen (ie, "electronic vivisection"). This article reviews the state of the art of wide-field and 3-D cardiovascular ultrasound in the assessment of congenital heart disease.

Three-dimensional reconstruction of color Doppler jets in the human heart.

A computer algorithm has been developed for segmentation and three-dimensional (3D) reconstruction of Doppler color-flow images. The algorithm enables the user to select a range of velocities, represented by colors, for segmentation and subsequent 3D reconstruction. The reconstructed flows are assigned a color palette and merged with the volume-rendered gray-scale image to produce a 3D image containing both flow and anatomic information. The results demonstrate the application of the algorithm to regurgitant and shunt jets with complex spatial and velocity patterns. We conclude that 3D reconstruction of selected color spectra (e.g., velocities) of Doppler color flows and surrounding anatomy is feasible in the clinical setting.

Diagnostic performance of two-dimensional versus three-dimensional transesophageal echocardiographic images of selected pathologies evaluated by receiver operating characteristic analysis.

UNLABELLED: The sensitivity and specificity of 2-D and 3-D echocardiographic images for the detection of selected morphological abnormalities were compared using receiver operating characteristic (ROC) analysis. Five experienced clinical echocardiographers blinded to the patients' diagnoses evaluated the 20 original static 2-D image sets and 20 corresponding 3-D reconstructions using a five point categorical scale that ranged from definitely abnormal to definitely normal. The ROC curve for the 3-D images was significantly (P < 0.05) closer to the ideal discrimination function than was the ROC curve for the 2-D transesophageal images (i.e., the sensitivity of the 3-D images was higher than that of the 2-D sequential images at the same specificity). IN CONCLUSION: 3-D transesophageal images provided better visual clues for the identification of morphological abnormalities than did serial 2-D echocardiographic images despite the same input information in both image formats. The use of ROC analysis assisted in the comparison of these two imaging techniques.

Three-dimensional ultrasound imaging of the atrial septum: normal and pathologic anatomy.

OBJECTIVES: This study investigated the feasibility of producing three-dimensional gray scale ultrasound images of the atrial septum to demonstrate normal and pathologic anatomy. BACKGROUND: Two-dimensional echocardiography is the principal technique used for imaging the atrial septum. Although the diagnostic accuracy of two-dimensional echocardiography is high, its capability for displaying complex three-dimensional relations is limited. METHODS: Three-dimensional ultrasound images were reconstructed from tomographic images obtained during routine transesophageal echocardiographic examinations. Custom-made semi-automatic algorithms for image enhancement, interpolation and segmentation were used to produce volumetric gray scale images. Volume-rendered displays of the atrial septum were generated for analysis. Sequential three-dimensional images were generated through the cardiac cycle and displayed cinematographically to permit assessment of motion. RESULTS: The three-dimensional images obtained from six patients clearly demonstrated normal and pathologic anatomy of the atrial septum, including atrial septal defects, atrial septal aneurysm and aortic valve ring abscess. The images could be manipulated electronically to demonstrate spatial relations and internal structural details. CONCLUSIONS: Three-dimensional gray scale reconstruction of ultrasound images obtained by transesophageal echocardiography is feasible. These images clearly demonstrate anatomic details and spatial relations. The gray scale images may be interactively manipulated to optimize the clinician's visualization of the atrial septum and its associated pathologic conditions.

Multidimensional visualization in echocardiography: an introduction.

X-ray films depict three-dimensional objects as shadows in a two-dimensional plane; thus, objects become superimposed. Computed tomography and other types of tomographic imaging, such as ultrasonography, acquire two-dimensional images of a material property within a thin slice. Sequential adjacent two-dimensional tomograms can be used to construct three-dimensional displays of objects. Visualization, a field of computer science, enables scientists to measure image attributes (extraction of features), identify features (classification), separate objects from one another (segmentation), and produce comprehensible, information-dense images from three-dimensional data sets (rendering). A three-dimensional rendering of the heart can be used to represent only one component of the heart, such as the atrial septum or the ventricular chamber, and can be shaded or colored to enhance comprehension. Three-dimensional images rendered sequentially over time result in a dynamic four-dimensional display. This report describes multidimensional visualization of objects and tissues and specifically discusses examples from echocardiography.

Three- and four-dimensional cardiovascular ultrasound imaging: a new era for echocardiography.

Three-dimensional and four-dimensional ultrasonography were pioneered in the 1960s yet have been used little clinically. Only recently have advances in cardiovascular ultrasound equipment and in digital image storage, manipulation, and display techniques made three- and four-dimensional imaging clinically feasible. In this report, we review the historical development of these technologies during 3 decades to their culmination in current state-of-the-art technology. Examples of such multidimensional images are presented, with special emphasis on clinical applications. Although several limitations persist, three-dimensional cardiovascular ultrasonography seems likely to enhance imaging of the heart and vessels in a manner similar to the advent of two-dimensional echocardiography in the M-mode era. Clinician-scientists will soon be able to extract an object, such as the heart, from the body electronically for the purpose of anatomic, functional, and histologic analysis without adverse effect on the patient.

Quantitation of leukocytes in endomyocardial tissue from 100 normal human hearts at autopsy. Implications for diagnosis of myocarditis from biopsy specimens of living patients.

From 100 normal human hearts, evenly distributed by age and sex, 5 endomyocardial samples were obtained from the septal surface of each ventricle with a cardiac bioptome. In each case, from both ventricles, the number of lymphocytes, eosinophils, plasma cells, and neutrophils was counted in 10 high-power (x400) microscopic fields, and the mean number of each type of leukocyte was calculated. In 95% of the 2,000 high-power fields, the number of interstitial lymphocytes was less than 5.0. Moreover, in all but one heart, the mean number of lymphocytes was less than 4.0. The mean number of eosinophils was 0.0-0.1 and of plasma cells was 0.0-0.3. The median number of neutrophils was 0.6. Recognition of the normal number of leukocytes in the heart may help to minimize false positive interpretations of myocarditis in biopsy specimens of endomyocardial tissue from living patients.