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.

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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.

SUMMARY 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 = 4.6-7.1 ml). We previously used isolated, ejecting dog hearts to compare directly measured ventricular volume (without reliance on geometric assumptions) with echocardiographic volume obtained by reconstructing multiple cross-sectional images obtained at 3-mm intervals along the vertical axis of the heart.'0 Comparison of simultaneous data obtained throughout the cardiac cycle revealed not only a high correlation of echo to direct volume, but also a high predictive value of direct volume from any echocardiographic determination owing to low variability (r = 0.972, SEE = 2.93 ml, direct volume range 9.4-54.7 ml). These measurements were obtained under highly controlled conditions and it was not expected that the accuracy of echocardiographic volume determination could be matched in clinical use or in research applications in intact animals. At the very least, one could not obtain the large number of slices used in that study, and we did not assess the accuracy of volume changes with decreasing numbers of slices.Using the same preparation in the present study, but analyzing the data using progressively fewer slices, we found that at least four cross-sectional images of known location are required to predict ventricular volume without significant loss in accuracy.