Search

The transmission of echocardiographic contrast medium and the cyclic changes in left ventricular videodensity during transpulmonary contrast echocardiography were investigated in nine adult volunteers with the use of intravenous injections of sonicated albumin (microbubble size 5.2 +/- 2.6 microns). Right and left ventricular and myocardial contrast were quantitated by videodensitometric analysis. The injections caused no symptoms, and no hemodynamic or electrocardiographic changes were observed. All injections resulted in right ventricular contrast. Mean peak right ventricular videodensity was 75 +/- 48 at end-diastole and 61 +/- 36 gray scale U/pixel at end-systole (p less than 0.05). Seventy-eight percent of injections resulted in left ventricular contrast with a mean peak videodensity of 21 +/- 33 gray scale U/pixel. Early systole was associated with a rapid decrease in left ventricular contrast intensity with near total disappearance of contrast by end-systole (from 23 +/- 33 and 17 +/- 23 U/pixel at end-diastole to 6 +/- 10 and 3 +/- 2 at end-systole at the left ventricular base and apex, respectively; p less than 0.05). None of the injections resulted in myocardial contrast enhancement by visual or quantitative analysis. Thus, left ventricular contrast echocardiography can be achieved after intravenous injections of sonicated albumin. Transpulmonary left ventricular contrast echocardiography is associated with near total disappearance of contrast during systole. This may be secondary to the destruction of microbubbles by the high left ventricular systolic pressure. These findings may help explain the limited success of this technique thus far for myocardial perfusion imaging.

To determine whether myocardial contrast echocardiography is quantitatively reproducible, repeated intracoronary injections of sonicated albumin (5%) were performed in eight open chest dogs. Paired injections were performed at baseline, during ischemia produced by ligation of a coronary artery, and during hyperemia induced by intravenous infusion of 0.75 mg/kg body weight of dipyridamole. Contrast washout curves were generated for the left anterior descending coronary artery territory (ischemic area) and left circumflex coronary artery territory (nonischemic area) by beat per beat analysis of frozen end-diastolic frames of left ventricular short-axis views. Peak contrast intensity, contrast washout half-time and area under the curve were derived from these curves. A total of 75 contrast washout curves were analyzed for the study of interinjection, intraobserver and interobserver reproducibility. The correlation coefficients between measurements obtained from paired injections of the echocardiographic contrast agent (interinjection reproducibility) ranged from 0.78 for peak contrast intensity to 0.87 for area under the curve. Percent error varied between 14.7% and 24.7%. The intraobserver variability in measurements was less than the interinjection variability, with a cumulative mean percent error of 17.8% and correlation coefficients of 0.72 (peak contrast intensity), 0.95 (area under the curve) and 0.96 (washout half-time). Interobserver correlation for all indexes was high (r = 0.92 to 0.96). It is concluded that peak contrast intensity, contrast washout half-time and the area under the curve derived from myocardial contrast washout curves can be measured reproducibly from videotapes. In addition, the variability between two injections attempted under identical conditions is greater than reader variability from videotapes.

It is controversial whether echocardiographic contrast agents prepared by sonication cause transient myocardial depression beyond that known to occur with contrast agents alone. In nine open chest dogs, contrast injections were made into the left anterior descending coronary artery during two-dimensional echocardiography. One hundred forty-four recordings were analyzed subsequently, by an observer who was unaware of other data, for percent depression of systolic wall thickening, duration of regional wall motion abnormalities, peak contrast enhancement and contrast washout. Two microbubble sizes were obtained by sonicating Renografin-76 (meglumine sodium diatrizoate): mean diameter 12 +/- 3 (SEE) and 20 +/- 6 micron. Four doses (range 0.5 to 3 ml) of each of four agents (12 and 20 micron bubbles in Renografin, nonsonicated Renografin and saline solution) were injected in random order. Significant relations were found between percent depression of systolic wall thickening, duration of regional wall motion abnormalities and contrast washout time versus microbubble size (p less than 0.001) and microbubble dose (p less than 0.01). Little increased contrast effect was found at larger doses or with larger microbubbles compared with the smaller doses and size studied. Injections of nonsonicated Renografin caused less depression of systolic wall thickening (p less than 0.05), faster resolution of wall motion abnormalities (p less than 0.05), less contrast (p less than 0.001) and more rapid contrast washout (p less than 0.001) than did 12 micron bubbles in Renografin. A significant correlation was found between the duration of regional wall motion abnormalities and contrast washout time (r = 0.93, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

A low pressure gradient across the residual lesion and a minimal percent residual stenosis are markers of a successful coronary angioplasty. A more physiologic method of assessing the results of coronary angioplasty would involve assessment of myocardial perfusion in the affected coronary bed. Contrast two-dimensional echocardiography provides information about regional myocardial perfusion. To assess the correlation between pre- to postcoronary angioplasty changes in gradient or percent stenosis and the increase in peak contrast intensity, 23 consecutive patients were studied during coronary angioplasty. In 19 of the 23 patients, the coronary angioplasty was successful and in 15 (79%) of the 19, an adequate echocardiographic study was obtained. Mild and transient side effects of echo contrast were observed in 3 of the 15 patients. The gradient across the residual lesions decreased from 52 +/- 12 to 11 +/- 4 mm Hg (mean +/- SD), the diameter of the stenotic lesion decreased from 89 +/- 10 to 25 +/- 16% and corrected peak contrast intensity (peak contrast - baseline contrast in gray level U/pixel) increased from 15 +/- 16 to 50 +/- 26. All these differences were significant at the p less than 0.001 level. Corrected peak contrast intensity correlated exponentially with the decrease in pressure gradient (r = 0.82, p less than 0.001). The correlation curve had a greater increase in peak contrast intensity at gradient decreases greater than 45 mm Hg. Corrected peak contrast intensity did not correlate with decrease in diameter of the stenotic lesion (r = 0.19).

Sonicated albumin has been proposed as a near ideal echocardiographic contrast agent with little myocardial toxicity or hemodynamic effect. Its use has not yet been reported in humans, partly because of difficulties in preparation. With use of the newly modified sonication method, 10 ml of 5% albumin was sonicated for 75 s with a 5.0 ml slow infusion of air. This resulted in microbubbles with a mean diameter (+/- SD) of 5 +/- microns). Fourteen patients undergoing routine coronary angiography were studied. One patient had normal coronary arteries; the other 13 had significant coronary artery disease. In a subgroup of nine patients, sonicated albumin and sonicated diatrizoate meglumine sodium (microbubble diameter 9 +/- 3 microns) were injected several minutes apart, using the same technique. Videodensity-time curves were obtained from a region of interest in the myocardium. Corrected peak contrast intensity (baseline contrast intensity subtracted from peak contrast intensity, gray scale U/pixel) for sonicated albumin and for sonicated diatrizoate meglumine sodium was 51 +/- 26 and 52 +/- 19, respectively (p = 0.89). Washout half-time (T1/2) for the two agents was 5.5 +/- 4.5 and 16.0 +/- 12.2 s, respectively (p = 0.01). One patient with unstable angina experienced transient chest pain after repeated albumin injections. No electrocardiographic changes, blood pressure changes or wall motion abnormalities were observed. Administered by intracoronary injection, sonicated 5% albumin is a safe and effective echocardiographic contrast agent for myocardial perfusion imaging, yielding excellent myocardial contrast with physiologic washout time.