Contrast echocardiography in acute myocardial ischemia. II. The effect of site of injection of contrast agent on the estimation of area at risk for necrosis after coronary occlusion

Myocardial contrast echocardiography has been shown to accurately assess the area at risk for necrosis after acute coronary occlusion in the experimental model. The area at risk as determined by this method, however, has been defined in different ways depending on the model used. Some investigators have injected the contrast agent proximal to the site of coronary occlusion (left main coronary artery or aorta) and defined the area at risk as the segment of myocardium not showing a contrast effect (negative risk area). Others have injected the contrast agent directly into the occluded vessel and have defined the area at risk as that showing contrast enhancement (positive risk area).To evaluate whether the areas at risk determined by these two techniques are identical, six open chest dogs were studied using both methods. The area at risk was slightly but significantly larger when the contrast agent was injected into the occluded vessel than when it was injected proximally into the left main coronary artery (4.98 ± 1.69 versus 3.97 ± 1.27 cm2, p < 0.01). It is concluded that the site of injection of the contrast agent significantly influences the determination of area at risk. Therefore, data obtained by the two techniques should not be used interchangeably, and in a given study the area at risk should be measured consistently using one technique

806-1 Left Ventricular Ejection Fraction After Myocardial Infarction: Importance of Both Infarct Site and Size

Left ventricular ejection fraction (LVEF) is an important prognostic variable after myocardial infarction (MI). While the extent of MI is known to affect the subsequent global LVEF, it is not clear whether anatomical site per se affects LVEF. Therefore, 48 consecutive patients (pts) who did not receive lytic therapy or undergo early revascularization were studied byechocardiography one week after Q wave MI. Using a previously validated endocardial mapping technique, the size of abnormal wall motion (AWM) in relation to the total endocardial surface area and the site of AWM were quantitated, LVEF was measured by Simpson's method using 2 apical views.ResultsNineteen pts had anterior MI (ANT) and 29 had inferior MI (INF). The mean LVEF was similar in both groups (ANT 46.9±14.7% vs INF 51.7±9.4%, pNS). The mean %AWM was greater in ANT MI (29.7±14.5) than in INF MI (21.3±13.8) (p=0.05). After accounting for differences in infarct size by multivariate regression analysis, both infarct size (p=0.0001) and infarct site (p=0.007) were significant independent determinants of LVEF. This effect was most pronounced in larger ANT Mis (%AWM&gt;25%) where the LVEF was significantly lower than in smaller Mis. In INF MI, despite a similar range of sizes. increasing %AWM had minimal effect on LVEF.ConclusionIn addition to infarct size, the site of AWM is an important determinant of global LVEF. This observation may reflect site-dependent differences in the biomechanical responses to regional ventricular dysfunction

Papillary muscle traction in mitral valve prolapse: Quantitation by two-dimensional echocardiography

Previous angiographic observations in patients with mitral valve prolapse have suggested that superior leaflet displacement results in abnormal superior tension on the papillary muscle tips that causes their superior traction or displacement. It has further been postulated that such tension can potentially affect the mechanical and electrophysiologic function of the left ventricle. The purpose of this study was to confirm and quantitate this phenomenon noninvasively by using two-dimensional echocardiography to determine whether superior displacement of the papillary muscle tips occurs and its relation to the degree of mitral leaflet displacement.Directed echocardiographic examination of the papillary muscles and mitral anulus was carried out in a series of patients with classic mitral valve prolapse and results were compared with those in a group of normal control subjects. Distance from the anulus to the papillary muscle tip was measured both in early and at peak ventricular systole. In normal subjects, this distance did not change significantly through systole, whereas in the patient group it decreased, corresponding to a superior displacement of the papillary muscle tips toward the anulus in systole (8.5 ± 2.6 vs. 0.8 ± 0.7 mm; p < 0.0001). This superior papillary muscle motion paralleled the superior displacement of the leaflets in individual patients (y = l.0x + 0.8; r = 0.93) and followed a similar time course. The systolic motion of the mitral anulus toward the apex, assessed with respect to a fixed external reference, was not significantly different in the patients and control groups (14.3 ± 4 vs. 15.5 ± 4.4 mm; p = 0.4) and therefore could not explain the superior papillary muscle tip motion relative to the anulus in the patients with mitral valve prolapse.These results demonstrate that normal mechanisms maintain a relatively constant distance between the papillary muscle tips and the mitral anulus during systole. In classic mitral valve prolapse, superior leaflet displacement is paralleled by superior displacement of the papillary muscles that is consistent with superiorly directed forces causing their traction. Two-dimensional echocardiography can therefore be used to measure these relations and test hypotheses as to their clinical correlates in patients with mitral valve prolapse

901-110 Three-Dimensional Ultrasound Can Accurately Reconstruct Intravascular Thrombi: In Vitro Validation

High-frequency ultrasound can potentially display gross morphologic changes during thrombus formation and lysis. Current intravascular ultrasound (IVUS) devices, however, provide only 2-dimensional cross-sectional images with limited overall appreciation of thrombus size and 3-dimensional (3D) configuration. The purpose of this study was to explore the ability of 3D reconstruction of serial ultrasound images to provide a quantitative assessment of intravascular thrombi. We therefore imaged 11 arterial thrombi of varying shape and volume (10 to 116mm3). To avoid thrombus disruption, we used an epivascular approach (also suitable for transvenous imaging) with a 20MHz IVUS catheter withdrawn at 1mm/sec. A 3D voxel image intensity data set was reconstructed, and thrombus volume was semiautomatically extracted based on its intensity. Calculated volume was compared with directly measured values by volume displacement in a miniature cylinder.Results3D reconstruction provided previously unobtainable longitudinal and 3D views that improved spatial appreciation of thrombus size, shape and channel formation. Calculated thrombus volumes agreed well with actual volumes: y=0.92x+2.4, r=0.98, SEE=5mm3, mean error = 1±5mm3(ns vs 0).Conclusion3D reconstruction can improve spatial appreciation of the shape of thrombi and accurately measure their volumes. This approach, suitable for epivascular or transvenous imaging, could potentially be used to study thrombus formation and lysis in research and clinical studies

Automated flow rate calculation based on digital analysis of flow convergence proximal to regurgitant orifice

AbstractObjectives. The purpose of the study was to develop and validate an automated method for calculating regurgitant flow rate using color Doppler echocardiography.Background. The proximal flow convergence method is a promising approach to quantitate valvular regurgitation noninvasively because it allows one to calculate regurgitant flow rate and regurgitant orifice area; however, defining the location of the regurgitant orifice is often difficult and can lead to significant error in the calculated flow rates. To overcome this problem we developed an automated algorithm to locate the orifice and calculate flow rate based on the digital Doppler velocity map.Methods. This algorithm compares the observed velocities with the anticipated relative velocities, cos ϑ/μt2. The orifice is localized as the point with maximal correlation between predicted and observed velocity, whereas flow rate is specified as the slope of the regression line. We validated this algorithm in an in vitro model for flow through circular orifices with planar surroundings and a porcine bioprosthesis.Results. For flow through circular orifices, flow rates calculated on individual Doppler maps and on an average of eight velocity maps showed excellent agreement with true flow, with r = 0.977 and ΔQ = −3.7 ± 15.8 cm3/s and r = 0.991 and ΔQ = −4.3 ± 8.5 cm3/s, respectively. Calculated flow rates through the bioprosthesis correlated well but underestimated true flow, with r = 0.97, ΔQ = −10.9 ± 12.5 cm3/s, suggesting flow convergence over an >2π. This systematic underestimation was corrected by assuming an effective convergence angle of 212 δ.Conclusions. This algorithm accurately locates the regurgitant orifice and calculates regurgitant flow rate for circular orifices with planar surroundings. Automated analysis of the proximal flow field is also applicable to more physiologic surfaces surrounding the regurgitant orifice; however, the convergence angle should be adjusted. This automated algorithm should make quantification of regurgitant flow rate and regurgitant orifice area more reproducible and readily available in clinical cardiology practice

Patterns of normal transvalvular regurgitation in mechanical valve prostheses

AbstractThe magnitude and spatial distribution of normal leakage through mechanical prosthetic valves were studied in an in vitro model of mitral regurgitation. The effective regurgitant orifice was calculated from regurgitant rate at different transvalvular pressure differences and flow velocities. This effective orifice area was 0.6 to 2 mm2for three tilting disc prostheses (Medtronic-Hall sizes 21, 25 and 29) and 0.2 to 1.1 mm2for three bileaflet valves (St. Jude Medical sizes 21, 25 and 33).In the single disc valves, Doppler color flow examination disclosed a prominent central regurgitant jet around the central hole for the strut, accompanied by minor leakage along the rim of the disc (central to peripheral jet area ratio 3.3 ± 1.2). The bileaflet prostheses showed a peculiar complex pattern: in planes parallel to the two disc axes, convergent peripherally arising jets were visualized, whereas in orthogonal planes several diverging jets were seen.Mounting the disc and bileaflet valves on a water-filled tube allowed reproduction and interpretation of this pattern: for the bileaflet valve, the jets originated predominantly from valve ring protrusions that contained the axis hinge points and created a converging V pattern in planes parallel to the leaflets and a diverging V pattern in orthogonal planes.Similar patterns were observed during transesophageal echocardiography in 20 patients with a normally functioning St. Jude prosthesis. In 10 patients with a Medtronic-Hall valve, a dominant central jet was observed with one or more smaller peripheral jets. The median central to peripheral jet area ratio was 5 to 1.In summary, in two types of mechanical valve prostheses, effective leakage orifice areas are reported and criteria proposed for the differentiation of “physiologic” and pathologic regurgitation based on the spatial configuration of the jets

The natural history of regional wall motion in the acutely infarcted canine ventricle

Two-dimensional echocardiography was employed to define the natural history of regional wall motion abnormalities in a canine model of acute experimental myocardial infarction. Serial short-axis two-dimensional echocardiograms were recorded in 11 closed chest dogs before coronary occlusion and 10, 30, 60, 180 and 360 minutes after permanent coronary ligation. Radiolabeled microsphere-derived blood flows were obtained in each study period and the histochemical (triphenyltetrazolium chloride) extent of infarction was determined at 6 hours. Previously published methods were used to quantitate field by field (every 16.7 ms) excursion of 36 evenly spaced endocardial targets. The circumferential extent of abnormal wall motion was followed sequentially using previously published definitions of abnormality: 1) systolic fractional radial change of less than 20%; 2) dyskinesia (systolic bulging) at the point in time (echocardiographic field) in which there is maximal dyskinesia; and 3) correlation with composite normal ray motion falling outside the 95 % confidence limits defined in the control period. On the basis of the triphenyltet razolium chloride staining pattern, the ventricle was divided into five zones: central infarct zone, zone with greater than 25% transmural infarction, total infarct zone, border zones and normal zone. Mean systolic fractional radial change was calculated for each zone and used as an index of the magnitude of abnormal wall motion.Regardless of the definition of abnormality employed, the circumferential extent of abnormal wall motion manifested at 10 minutes after occlusion did not significantly change, even up to 6 hours later. Similarly, 10 minutes after coronary occlusion the three infarct zones and border zones demonstrated significantly reduced systolic fractional radial change. This remained stable over the remainder of the 6 hour study period.It is concluded that once established at 10 minutes after coronary occlusion, the circumferential extent and magnitude of abnormal wall motion do not significantly change in the immediate postinfarct (6 hour) period

A new echocardiographic model for quantifying three-dimensional endocardial surface area

A new technique for quantitatively mapping the three-dimensional left ventricular endocardial surface was developed, using measurements from standard cross-sectional echocardiographic images. To validate the accuracy of this echocardiographic mapping technique in an animal model, the endocardial areas of 15 excised canine ventricles were calculated using measurements made from echocardiographic studies of the hearts and compared with areas determined with latex casts of the same ventricles. Close correlation (r = 0.87, p < 0.001) between these two measures of endocardial area provided preliminary confirmation of the accuracy of the maps.To further characterize the mapping algorithm, it was translated into computer format and used to map the surfaces of idealized hemiellipsoids. Areas measured with this mapping technique closely approximated the actual areas of idealized surfaces with a wide spectrum of shapes; maps were particularly accurate for ellipsoids with shapes similar to those of undistorted human ventricles. Also, the accuracies of area calculations were relatively insensitive to deviation from the assumed positions of the echocardiographic short-axis planes. Finally, although the accuracy of the mapping technique improved as data from more transverse planes were added, the procedure proved reliable for estimating surface areas when data from only three planes were used. These studies confirm the accuracy of the echocardiographic mapping technique, and they suggest that the resulting planar plots might be useful as templates for localizing and quantifying the overall extent of abnormal wall motion