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A computer algorithm was developed and applied to measure brightness decay rates of myocardial contrast opacification observed with two-dimensional echocardiography (2DE). An agitated mixture of diatrizoate meglumine and saline (Renografin-saline) was injected into the left main coronary artery of 17 closed-chest dogs during the control state as well as after placement of an intracoronary plug to induce 85% stenosis in the left anterior descending coronary artery (LAD) in five dogs. In 12 dogs, injections were also performed distally to complete intracoronary balloon occlusion of the LAD. For each injection, up to 35 electrocardiographic-gated, end-diastolic 2DE frames were digitized into an image-processing computer that determined mean pixel brightness of each of 12 myocardial segments per 2DE short-axis cross-section. Time-activity curves for each segment were generated, and contrast decay half-life (t 1/2) was calculated. Mean t 1/2 for control-state injections was found to be 24.1 +/- 7.7 sec, as opposed to 293.8 +/- 164.5 sec after complete coronary occlusion (p less than .001). In the five dogs in which 85% LAD stenosis was induced, prolongation of contrast t 1/2 from 18.3 +/- 8.9 sec during control to 44.3 +/- 21.0 sec (p less than .001) after plug insertion occurred in myocardial segments subserved by the stenosed vessel. No significant change occurred in segments that were not supplied by the stenosed vessel (21.9 +/- 9.1 sec during control vs 24.9 +/- 11.6 after plug insertion into the LAD). A reproducibility study of injection-to-injection t 1/2 in the control state indicated a correlation coefficient of r = .84 and a standard error of the estimate (SEE) equal to 5.86 sec, while interobserver t 1/2 reproducibility was r = .91 and SEE = 5.21 sec. The t 1/2 measurement derived by computer analysis of myocardial contrast 2DE may serve as an index for characterization of regional myocardial blood flow and may be applicable to evaluate interventions that alter perfusion.

Two-dimensional echocardiography was applied experimentally in a closed chest dog model with intact pericardium to determine the location, magnitude and extent of contractile response during pacing from discrete ventricular sites. Mid ventricular short-axis tomographic images obtained during regular sinus rhythm and subsequent premature ventricular beats provided comparative measurements of global and segmental systolic changes of cross-sectional luminal areas and myocardial wall thickness. Computer-assisted standardized analysis of segmental systolic fractional area change and wall thickening was used to map left ventricular contraction during normal rhythm and premature beats of 70% coupling interval, induced alternately from anterior and lateral aspects of the mid-left ventricular short-axis cross-sectional plane. A characteristic pattern consisting of early systolic contraction and wall thickening was followed by paradoxical motion and wall thinning in late systole in segments corresponding to the region of direct electrical stimulation. Statistical analysis of segment by segment function indicated a maximal amount of premature beat contractile derangement at the site of the stimuli. Pacing from a right ventricular wall site in the midventricular plane caused a similar premature beat response at the anterior aspect of the interventricular septum. It is concluded that two-dimensional echographic analysis of segmental ventricular function can identify the location of electrical stimuli, and thus might non-invasively characterize regional patterns of contraction associated with ectopic foci during arrhythmias.

Two-dimensional echocardiographic measurements of regional left ventricular end-diastolic wall thickness and systolic wall thickening were studied during coronary artery occlusion and early after reperfusion and compared with measurements of regional myocardial infarct size. In 25 closed chest anesthetized dogs with left anterior descending coronary artery occlusion followed by reperfusion, the occlusion period was 3 minutes in group I (n = 4), 20 minutes in group II (n = 4), 60 minutes in group III (n = 5) and 180 minutes in group IV (n = 12). Infarct size in groups III and IV was quantitated using the triphenyltetrazolium chloride technique. After coronary occlusion, wall thickening was replaced by thinning in the center of the ischemic region at the midpapillary echographic short-axis section, and no improvement in function occurred up to 60 minutes after reperfusion, except in group I. Ischemic zone enddiastolic wall thickness did not change significantly from control to the end of the coronary occlusion period, except Group IV. At 60 minutes after reperfusion, enddiastolic wall thickness increased only slightly in groups I and II (by 7.2 and 0.24%, respectively), but a marked increase was observed in groups III and IV (by 41 and 50%, respectively). The percent change in ischemic zone end-diastolic wall thickness from before reperfusion to 60 minutes after reperfusion correlated well with the amount of myocardial necrosis in corresponding segments (r = 0.936, standard error of estimate = 11.4%); an increase in segmental end-diastolic wall thickness of more than 25% was generally associated with 20% or more segmental necrosis. It is concluded that significantly increased regional end-diastolic wall thickness early after reperfusion is associated with irreversibly damaged myocardium, and this might be used as an index of myocardial salvage.