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Two-dimensional echocardiography is an excellent technique for detecting left ventricular thrombi, however, acute clot is sometimes difficult to differentiate from adjacent myocardium and intracavitary signals. We hypothesized that quantitative assessment of the acoustic properties of acute left ventricular thrombi using a quantitative backscatter imaging system would permit the differentiation of thrombus from adjacent myocardium and intracavitary echoes. Acute, experimental left ventricular thrombi in seven dogs were evaluated with a quantitative backscatter imaging system that allowed the measurement of relative integrated backscatter and cyclic (i.e., diastolic minus systolic) variation in integrated backscatter. Coronary ligation abolished the cyclic variation in relative backscatter that occurred in normal myocardium. The end-diastolic relative backscatter in the thrombus (16.9 +/- 1.3 dB) was significantly higher than in apical myocardium (13.2 +/- 0.6 dB, p less than 0.05). There was no significant difference in the cyclic variation in relative backscatter among thrombus, ischemic myocardium, or intracavitary blood. Thus, the quantitative assessment of the acoustic properties of left ventricular thrombi can be useful in their detection and in the differentiation from myocardium and intracavitary signals.

The development of left ventricular hypertrophy in patients with heart disease often has far-reaching clinical implications with respect to overall morbidity and mortality. Approaches used to assess left ventricular mass include electrocardiography, echocardiography, contrast ventriculography, single photon-emission tomography, and conventional computed tomography. However, all of these modalities suffer from some major draw back that precludes widespread application to all patients. In this study we assessed the accuracy of determinations of left ventricular mass in 22 dogs by rapid-acquisition (50 msec) computed axial tomography (RACAT), an ultrafast computed tomographic (CT) instrument. Electrocardiographically triggered, end-diastolic, short-axis cardiac scans were obtained from apex to base during administration of intravenous iodinated contrast. Myocardial edges were determined for each tomographic scan by two methods: the regional half-contour method (the CT density half way between that of the left ventricular myocardium and adjacent ventricular cavities or lung) and "interactive plateau thresholding" of the cardiac borders. Left ventricular mass by RACAT was calculated as the sum of the mass of each individual scan from apex to base (modified Simpson's rule). Postmortem left ventricular mass ranged from 58 to 160 g. The correlation between true left ventricular mass and tomographically determined mass was excellent (r = .99), with the slope and y intercept not statistically different from 1 and 0, respectively. The standard error of the estimate was 4.1 g. Interobserver and intraobserver variability for determining left ventricular mass demonstrated excellent agreement (r = .99 and r = .99, respectively). We conclude that quantitative assessment of left ventricular mass can be accurately and reproducibly performed in dogs by rapid acquisition CT scanning. It is likely that this technique will be readily transferable to the clinical settings and prove to be an important method for quantifying left ventricular mass in patients.

Integrated ultrasonic backscatter from normal myocardium has been shown to vary with the phase of cardiac contraction (decreasing from end-diastole to end-systole) in previous studies of open-chest dogs. If confirmed, this finding would have important implications for clinical application of ultrasonic tissue characterization. Our hypothesis was that a cardiac cycle-dependent variation in regional average gray level would be detected on analysis of digitized two-dimensional echocardiograms. We analyzed echocardiographic images from 16 subjects in whom normal, technically good studies were obtained with a commercial phased-array scanner and a 2.25 MHz transducer. Images from six subjects were digitized from stop-frame photographs and those from 10 subjects were obtained directly in digital format from the scanner. Average gray level was measured in a portion of the left ventricular posterior wall in parasternal long-axis images obtained at end-diastole and end-systole by both photographic and digital-image acquisition. In seven of the subjects from whom digital images were acquired, left ventricular posterior wall gray level and ventricular septal gray level were also evaluated on parasternal short-axis images. In images digitized by the photographic technique, mean posterior wall gray level decreased significantly from end-diastole (175 +/- 5.8 SEM) to end-systole (167 +/- 5.1, p less than .05). Similarly, in images digitized directly, mean posterior wall gray level in the long-axis view decreased from end-diastole (71 +/- 3.4) to end-systole (59 +/- 2.5, p less than .005).(ABSTRACT TRUNCATED AT 250 WORDS)

Videodensitometry is a nongeometric method of coronary angiographic analysis that can be used to provide an index of coronary luminal area. However, there are few direct studies in vivo of the relationship of videodensitometric data to independent measures of luminal area in humans. Although videodensitometry is theoretically independent of angiographic projection and luminal shape, validation of these assumptions in vivo is also limited. We therefore used intraoperative high-frequency epicardial echocardiography, a technique that can directly determine human coronary luminal area and shape in vivo, to further validate videodensitometry. A total of 36 arterial segments in the left anterior descending and right coronary arteries were studied by videodensitometry and high-frequency echocardiography. Videodensitometry was performed on angiograms in which the arterial segment of interest was not markedly foreshortened and was uniformly filled with contrast. In 22 discrete lesions (13 with circular lumens and nine with oval or complex lumens), videodensitometric and echocardiographic measures of luminal area correlated well (r = .86). In 33 coronary arterial segments, the effect of angiographic projection on videodensitometry was determined by comparison of the results of videodensitometry performed on left anterior oblique vs right anterior oblique angiograms of the segments. Here too, the correlation was good (r = .94, y = 1.04x + 0.002). The good correlation of left anterior oblique with right anterior oblique videodensitometric results held true for lesions with circular and oval or complex lumens. This study further validates the ability of videodensitometry to provide an index of coronary luminal area and confirms in vivo previous assumptions that the results of videodensitometric analysis are independent of angiographic projection and luminal shape.

Integrated ultrasonic backscatter has been related to collagen deposition in fibrotic myocardium. The purpose of our study was to measure the integrated ultrasonic backscatter in the right and left ventricles of 10 normal freshly excised canine hearts and five normal formalin-fixed human hearts. A 2.25 MHz, 50% fractional bandwidth transducer was positioned at the transducer focal distance from the epicardium. The radio frequency backscatter signal, excluding specular reflections, was digitized, squared, and integrated to yield the integrated ultrasonic backscatter (in decibels down from a 100% reflector). The segment of myocardium corresponding to the integrated ultrasonic backscatter sample volume was excised and assayed for hydroxyproline, a marker for collagen. A second purpose of our study was to evaluate the influence of fixation with formalin on the backscatter. Regional integrated ultrasonic backscatter was therefore measured in 10 freshly excised canine left ventricles, which were fixed in 10% formalin for 2 weeks. Integrated ultrasonic backscatter measurements were then repeated. In freshly excised canine hearts, the integrated ultrasonic backscatter from right ventricle was higher than that from left ventricle (-60.4 +/- 1.6 [SEM] vs -66.9 +/- 1.0 dB; p less than .001). The collagen content of right ventricle was also higher than that of left ventricle (4.40 +/- 0.26 [SEM] vs 3.58 +/- 0.13 micrograms/mg dry weight; p less than .005). Similar results were obtained in human hearts. There were no correlations between integrated ultrasonic backscatter and collagen content (r = .28 and .32 for dogs and humans, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

We tested the hypothesis that lesion rethrombosis after streptokinase reperfusion is related to luminal size of the residual stenosis. Two independent techniques of analyzing coronary angiograms, quantitative coronary angiography and computer-based videodensitometry, were used to estimate the size of the residual lumen immediately after discontinuation of streptokinase. These techniques were selected because they provide independent estimates of cross-sectional area of a lesion with high degrees of reproducibility and minimal observer variability. Twenty-four patients who had undergone successful reperfusion with streptokinase were studied. Seven patients had lesion rethrombosis documented either on a repeat angiogram, at autopsy, or, in one case, by the fact that the patient had an acute transmural infarction resulting in death. Vessel patency was documented by repeat coronary angiography 8 to 14 days after initial streptokinase reperfusion in the other 17 patients. As assessed by quantitative coronary angiography, seven of 13 patients (54%) with minimal luminal cross-sectional areas of less than 0.4 mm2 had rethrombosis. None of the 11 patients with lumens greater than 0.4 mm2 had rethrombosis. In the 17 patients with vessels that remained patent the size of the residual lesion at repeat catheterization was compared with its size immediately after reperfusion with streptokinase. Over the intervening 8 to 14 day interval, an average percentage increase in minimal cross-sectional area of 116 +/- 34% was observed. In seven patients minimal luminal cross-sectional area more than doubled. Integrated optical density, an index of the severity of coronary stenosis derived from computer-based videodensitometry, was also useful in identifying a subgroup of patients at high risk for rethrombosis of lesion.(ABSTRACT TRUNCATED AT 250 WORDS)

In animal hearts, the magnitude of integrated ultrasonic backscatter is increased in fibrotic myocardium. Our purpose in this study was to quantitate the relationship between ultrasonic backscatter and collagen deposition in 10 excised human hearts with old infarcts. A 2.25 MHz, 50% fractional bandwidth transducer was positioned at the transducer focal distance from the epicardium of each specimen. The radio frequency backscatter signal was digitized, squared, and integrated to yield the integrated ultrasonic backscatter, which was referenced to the backscatter from a water/steel interface. The interrogated myocardium was then excised and divided into two portions. One portion was assayed for hydroxyproline, a marker for collagen. A second portion was sectioned, stained with Masson's trichrome, and studied with the use of a computer-assisted image analysis system. There was a linear correlation between the magnitude of integrated backscatter and myocardial collagen content estimated by hydroxyproline assay (r = .78). Quantitative histologic analysis revealed a variable relationship between the transmural distribution of collagen and the corresponding transmural pattern of the backscatter signal. In two specimens exhibiting a discrete layer of subendocardial fibrosis, the backscatter amplitude was also increased in the subendocardial region. In specimens with other patterns of fibrosis, the local backscatter amplitude did not correspond to the transmural pattern of collagen distribution. We conclude that the quantitative analysis of ultrasonic backscatter shows promise for the noninvasive evaluation of myocardial fibrosis after infarction.

Although immediate and late changes in coronary stenoses after percutaneous transluminal coronary angioplasty (PTCA) have been reported, most investigators have employed qualitative or semiquantitative techniques to analyze the angiograms. Such data is not optimal because of considerable interobserver variability and the use of relative instead of absolute changes in lesion geometry. Analysis is further compounded by the indistinct edges that characterize coronary lesions immediately after angioplasty. To quantify the changes in minimal cross-sectional area (MCSA) of the coronary lumen that occur during and after PTCA, we analyzed the angiograms of 23 patients before PTCA, immediately after PTCA, and at 7.2 +/- 3.0 (mean +/- SD) months follow-up using two computer-assisted methods of angiographic analysis--quantitative coronary angiography (QCA) and videodensitometry (VID). QCA provides an absolute measure of the area of the lumen; VID is a nongeometric method that is not dependent on exact border recognition. Based on these quantitative methods, we found that successful angioplasty is associated with about a three-fold increase in the MCSA of the lesion (from 1.0 to 3.2 mm2). This area is, however, well below normal and is less than half of the average MCSA of the inflated dilating balloon. Analysis of follow-up angiograms demonstrated that eight of 23 patients had a substantial late increase in the MCSA of the lesion (from 2.7 to 4.1 mm2) after the angioplasty procedure. Clinical, hemodynamic, and angiographic characteristics immediately after PTCA were not predictive of MCSA of the lumen at follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

We postulated that the analysis of regional image texture in two-dimensional (2D) echocardiograms would be an accurate method to differentiate normal from abnormal myocardial structure. We tested this hypothesis with quantitative texture measures to study the regional, spatial distribution of echo amplitudes in 2D echocardiograms performed before and immediately after blunt left chest trauma was induced in six anesthetized dogs. After trauma the contused region of myocardium appeared brighter and exhibited an altered myocardial texture. By use of a set quantitative texture measures, we found no significant differences in pretrauma images when normal regions were compared with regions to be contused. Also, we found no difference when we compared the normal regions in each animal in pretrauma vs posttrauma images. Twelve measures, however, differentiated normal from contused regions within the posttrauma images (p values ranged from .0057 to .0001 by multivariate analysis of variance). These texture measures were capable of differentiating normal from abnormal tissue only when texture along the azimuthal (lateral) direction was calculated. We conclude that regions of myocardial contusion exhibit visibly altered local echo-amplitude patterns (altered image texture) and that these image texture alterations may be quantified with digital image analysis techniques. These findings suggest that quantitative texture calculations may be a useful approach to ultrasound tissue characterization.

Regional two-dimensional (2D) echocardiographic amplitude patterns, or image texture, may be of diagnostic importance. Echocardiographic image texture is due in part to acoustic speckle, a complex pattern of interference of reflections from many small scatterers in tissue. The regional speckle pattern appears to be altered in several disorders associated with abnormalities in myocardial structure but also may be altered by a variety of characteristics of the scanning instrument. We hypothesized that quantitative measures of regional 2D echocardiographic image texture would vary as a function of position in range and azimuth within the field of view, even when imaging a uniform ensemble of scatterers. We tested this hypothesis by imaging a tissue-equivalent phantom with two phased-array scanners and two different methods of digitization. We analyzed the texture in several regions of interest separated in range and azimuth and found significant differences in quantitative texture measures as a function of position of the region of interest in the sector field of view (p values .006 to .0001 by multivariate analysis of variance). We found significant regional variability in texture with both scanners and both methods of digitization. We conclude that regional quantitative image texture in 2D echocardiograms varies as a function of range and azimuth, even when imaging a uniform ensemble of scatterers. This variability is related to several physical and instrument-related phenomena and precludes interpreting all regional texture alterations as indicating tissue structural abnormalities.