To facilitate the passage of echo contrast agents through the microcirculation and the echocardiographic study of myocardial perfusion, ultrasonic energy (sonication) was employed to produce contrast agents consisting of relatively uniform, stable and small (less than 10 mu diameter) gaseous microbubbles suspended in liquid solutions. The size and persistence of the microbubbles was verified by light microscopy and an in vitro system were employed for comparative assessment of peak echo amplitude and echo persistence characteristics of various contrast agents. The study indicated that although a variety of hand-agitated and sonicated contrast agents provided satisfactory echo intensities, sonication was clearly superior to the hand-agitation method, because sonication produced smaller, more uniform and more stable microbubbles that may be suitable for myocardial contrast echocardiography. It is concluded that of the contrast agents examined, sonicated solutions of sorbitol (70%) and dextrose (70%) appeared to have particular potential because of the small sizes of the microbubbles (6 +/- 2 and 8 +/- 3 mu, respectively) and their prolonged in vitro persistence. The use of sonication to produce standardized, small and stable microbubbles should facilitate physiologic passage of the contrast agent through the capillary beds and allow two-dimensional imaging of the left heart myocardium during right-sided, aortic root, coronary sinus or intracoronary contrast injections.

SUMMARY Regional differences in wall motion and wall thickening were quantitated in the normal left ventricle using two-dimensional echocardiography (2-D echo). Using a computer-aided system, the left ventricle was subdivided in a standardized manner into 40 segments of five 2-D echo short-axis cross sections from the mitral valve level to the low left ventricle or apex. Measurements of sectional and segmental cavity areas, muscle areas and endocardial as well as epicardial peritneters, allowed assessment of contractile function using such indexes as endocardial systolic fractional area change (FAC), wall thickening (WTh), and circumferential fiber shortening (shortening). In 50 normal anesthetized, closed-chest dogs (including 10 studies in the conscious state) and in 32 normal humans, left ventricular contractile function increased significantly from base to apex. Thus, in anesthetized dogs, sectional FAC, WTh and shortening increased from left ventricular base to apex as follows: 39.4 ± 5.1% to 61.6 ± 7.2%, 20.5 ± 6.6% to 46.7 11.5% and 22.7 ± 3.4% to 35.4 5.9%, respectively. Similar trends were noted in conscious dogs. In man, sectional FAC, WTh and shortening also increased from the mitral valve to the low left ventricular level: 38.8 3.3% to 60.7 4.5%, 23.9 ± 5.6% to 28.9 ± 7.6% and 21.4 ± 5.0% to 30.6 ± 5.6%, respectively. Detailed segmental analysis in individual cross sections also revealed regional differences in contraction. Generally, contraction was most vigorous in posterior regions of the left ventricle. The septal regions exhibited lowest contraction at the base, but also the greatest increase from base to apex, both in the canine and human. Lateral regions did not show significant changes along the length of the left ventricle. Diastolic wall thickness also varied. We conclude that contraction in the normal left ventricle cannot be assumed to be uniform or symmetrical. These normal regional differences in function should be taken into account when evaluating altered physiologic states and in studying effects of therapeutic interventions.FOR MANY YEARS cardiologists have assumed that the pattern of contraction in the normal left ventricle is concentric and uniform, classically defined as synergic motion. i Most of the earlier studies aimed at characterizing ventricular function were therefore based on models and assumed myocardial fiber structure consistent with uniform contraction.2 3 However, animal investigations have shown that the distribution of fiber angles is complex and changes during systolic contraction; endocardial and epicardial fibers tend to be oriented longitudinally and midwall fibers circumferentially.4 A study by Greenbaum et al.5 indicates that the human cardiac fiber architecture is even more complex than previously thought. Thus, models based on uniform wall motion may not adequately describe LV function in normal states, a prerequisite for studying altered physiologic conditions. Clinical studies using cineventriculography in man have indicated that myocardial performance ...

Left ventricular stroke volumes derived by two-dimensional echocardiography (2D echo) were compared with thermodilution and cineangiography measurements in closed-chest dogs before andone hour after proximal LAD occlusion. Stroke volume was calculated from end-diastolic and end-systolic volumes reconstructed by two models: 1) Simpson's rule employing left ventricular length and five short-axis cross-sectional areas; 2) a simplified volume formula (V = 5/6 area . length), utilizing a single short-axis area at either the mitral valve or midpapillary muscle level. The comprehensive Simpson reconstruction yielded a good correlation of 2D echo stroke volume against thermodilution (r = 0.89) over a range of normal (N = 14) and ischemic (N = 8) states. The simplified formula provided a satisfactory correlation (r = .90, N = 22) when using the midpapillary cross-section, which encompassed the induced ischemic dys-synergy. In contrast, when using the mitral valve level cross-section above the site of ventricular asymmetry, there was no significant statistical correlation. Comparison of cineangiography with 2D echo volume reconstruction based on the simplified formula with the midpapillary muscle level section yielded good correlations for stroke volume (r = 0.87) and ejection fraction (r = 0.97). Intraobserver and interobserver variability of duplicate echo stroke volume measurements was 8% and 10%, respectively. We conclude that 2D echocardiography in dogs permits quantitation of left ventricular stroke volume in normal and ischemic states.

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