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L W Eaton

Publications and source records attributed to L W Eaton.

11 recordsLinked to original sources
PubMed1983

Accuracy of volume determination by two-dimensional echocardiography: defining requirements under controlled conditions in the ejecting canine left ventricle.

The accuracy of two-dimensional echocardiographic left ventricular volume measurement in an isolated heart preparation was tested using Simpson's reconstruction of progressively fewer short-axis cross sections of known location. Echocardiographic images from five ejecting hearts submerged in a special tank were obtained under conditions designed for maximal accuracy of echocardiographic volume assessment. Echocardiographic determinations of 52 volumes at various times throughout the cardiac cycle were compared, by least-squares linear regression, with simultaneous direct-volume measurements by volumetric chamber (range 9.4-44.8 ml). Echocardiographic and direct measurements correlated well for all numbers of cross sections from 1-19 (r = 0.84-0.97); however, variability of direct volume predicted from a given echocardiographic measurement increased nonlinearly as the number of cross sections per heart decreased, and was especially large when three or fewer cross sections were used (SEE = 4.6-7 ml). The accuracy of echocardiographic measures was compared for each number of cross sections per heart, varying from one to 19; accuracy was defined as the mean absolute difference between echocardiographic and direct measurements of volume, ejection fraction, and maximal rate of ejection. The accuracy of echocardiographic measurements was significantly reduced with fewer than four cross sections per heart for ventricular volume, three cross sections for ejection fraction, and five cross sections for maximal rate of ejection. In light of what appears to be required for accurate echocardiographic volume measurement in this controlled, ejecting, noninfarcted, in vitro preparation, additional cross sections may be required in intact animals and human subjects, especially in those with diseases that cause ventricular asymmetry or regional dysfunction.

Animals↗
PubMed1981

Ventricular size and shape by two-dimensional echocardiography.

The evaluation of cardiac size and shape has been aided by the recent development of high resolution real-time two-dimensional echocardiography, which permits dynamic cross-sectional evaluation of all or a large portion of the left ventricle throughout the cardiac cycle. This review addresses itself to the determination of left ventricular size and shape by two-dimensional echocardiography. A method is described for accurate volume determination in the intact, isolated, ejecting canine heart. By combining the two-dimensional echocardiogram with knowledge of transducer position and orientation with respect to the heart, it is possible to reconstruct a three-dimensional representation of a chamber and thereby measure volume without reliance on major geometric assumptions. Because of the unique ability of two-dimensional echocardiography to produce a cross-sectional image of the beating heart in a large number of planes, it is suitable for the determination of cardiac shape and architecture. The recognition of early regional cardiac dilatation in acute myocardial infarction is described. Changes in ventricular shape brought about by the dynamic alterations lend themselves well to two-dimensional echocardiographic study. The pivotal nature of the interventricular septum renders it susceptible to changes in the functional state of both ventricles. That the interventricular septum may mediate ventricular interaction acutely is suggested by the acute effects of right ventricular loading in man using the Mueller maneuver. Leftward septal displacement and flattening of the septum during the early maximal Mueller maneuver is evidenced by a substantial increase in the radius of curvature of the septal segment, without a change in the left ventricular free wall. This septal flattening occurs in diastole and persists during systole. Diastolic events thus appear to influence systolic shape. Changed septal shape may be an important mechanism of, and evidence for, ventricular interdependence in normal man.

Animals↗
PubMed1981

Transseptal pressure gradient with leftward septal displacement during the Mueller manoeuvre in man.

Septal displacement is postulated as an important mediator of ventricular interdependence. During acute right ventricular loading with the Mueller manoeuvre the septum flattens and shifts leftward. To investigate the mechanism of this septal deformation, we measured transseptal pressures in nine patients during Mueller manoeuvres with simultaneous right and left ventricular micromanometers, and left ventricular configuration with two-dimensional echocardiograms. Data were analysed throughout diastole and at end-systole during control and maximum Mueller manoeuvre (-40 to -80 mmHg airway pressure). Leftward septal displacement during the Mueller manoeuvre was evidenced by an increase in septal radius of curvature at end-diastole persisting through end-systole. The left ventricular free wall radius of curvature was unchanged. During the Mueller manoeuvre, the left ventricular cavity area decreased significantly in the cross-sectional view. All Mueller manoeuvres were associated with a decrease in left-to-right ventricular transseptal pressure gradient throughout diastole. There was no significant change in the gradient at end-systole; septal flattening persisted, however, despite a pronounced left to right pressure gradient. Thus, diastolic septal flattening during right ventricular loading is associated with a decreased transseptal pressure gradient but does not require right ventricular diastolic pressure to exceed left ventricular diastolic pressure. The persistence of flattening in systole suggests that once septal shift occurs during diastole, other forces during systole maintain the deformity despite a large intracavitary transseptal gradient.

Blood Pressure↗
PubMed1979

Regional cardiac dilatation after acute myocardial infarction: recognition by two-dimensional echocardiography.

To assess the early topographic changes after acute transmural myocardial infarction, we studied 28 patients during the first two weeks after infarction by serial two-dimensional echocardiography. Regional end-diastolic segment lengths and wall thicknesses for anterior and posterior left ventricular walls were calculated. Eight patients showed infarct expansion, with disproportionate dilatation and transmural thinning in the infarcted zone, that was significantly different (P less than 0.005) from changes in non-infarcted regions. This regional expansion led to an overall left ventricular dilatation in these eight patients of 25 per cent compared to 5 per cent in the 20 patients without infarct expansion. Although the eight patients with regional expansion did not have significantly higher peak creatine kinase or Killip classification, they had a significantly greater eight-week mortality (four of eight versus none of 20, P less than 0.004). Thus, regional cardiac dilatation may be an early, lethal consequence of transmural infarcts, and appears to be an important mechanism of acute cardiac dilatation after myocardial infarction.

Acute Disease↗
PubMed1979

Accurate volume determination in the isolated ejecting canine left ventricle by two-dimensional echocardiography.

Two-dimensional echocardiography can provide serial cross-sectional images of the left ventricular cavity. We examined whether such serial images from steady-state ejecting hearts would allow three-dimensional reconstruction and accurate volume estimation without major geometric assumptions. Cross-circulated, paced dog hearts were suspended in a blood-filled tank. Serial cross-sectional images were taken at 3-mm intervals along the vertical axis. Left ventricular cavity and muscle areas of each image were planimetered with a light-pen system and summated for volume: total volume = sigma (areas x 3 mm). Direct left ventricular volume was measured through the cardiac cycle with a volumetric chamber connected to a balloon in the ejecting left ventricle. In six hearts, 67 separate direct volume measurements (range 9.5--54.7 ml) from various points in the cardiac cycle were compared with the simultaneous echo volume measurements. By least squares linear regression, echo volume = 1.01 (direct volume) - 0.44 ml; r = 0.972, SEE = 2.93 ml. Provided accurate cross-sectional localization is available, these studies suggest that extremely accurate steady-state left ventricular volume can be determined noninvasively in the ejecting heart from multiple cross-sectional images.

Animals↗