Power Doppler dual-frame triggering of myocardial contrast echocardiography: a quantitative video intensity analysis

Reproducibility of intravenous intermittent triggered myocardial contrast echocardiography in healthy subjects

Few data have been published on the reproducibility of baseline subtracted peak intensity obtained from intravenous intermittent triggered myocardial contrast echocardiography. We investigated the reproducibility of the peak intensity measured from intravenous intermittent triggered myocardial contrast echocardiography in 10 young healthy males. The contrast echocardiography was obtained using the second harmonic mode with an intravenous bolus injection of Levovist (first study). The same myocardial contrast echocardiography was repeated after the first study (second study). The myocardial opacification and peak intensity in the 12 segments of the apical 4 and 2 chamber views were assessed visually and quantitatively. The differences in the peak intensity between the initial and repeated measurements in the first study (intraobserver reproducibility) and between the initial measurements in the first and second studies (interinjection reproducibility) were assessed using the Bland and Altman method. The degree of opacification was good or intermediate in 207/228 (91%) of the segments. The agreement of myocardial opacification between the first and second studies was 87/114 (76%). However, significantly higher peak intensity was obtained in apical septal (8200 +/- 6300 au2) and mid septal (8500 +/- 6000 au2) segments in the 4 chamber view and in the mid inferior (12400 +/- 9300 au2) and apical inferior (10700 +/- 6300 au2) segments in the 2 chamber view compared with other segments. The mean differences of the peak intensities according to the Bland and Altman analysis was -1600 +/- 5000 au2 in the intraobserver reproducibility study, and -1100 +/- 5300 au2 in the interinjection reproducibility study. Thus, the measurement error was determined to range from 8400 au2 to 9500 au2 in both studies. We conclude that the peak intensity obtained from intravenous intermittent triggered myocardial contrast echocardiography using Levovist varies significantly among segments in the left ventricular myocardium. Large intraobserver and interinjection variability exists in the measurement of peak intensity, suggesting that the reproducibility of this technique is limited for quantitative assessment of myocardial perfusion.

Measurement of radial artery contrast intensity to assess cardiac microbubble behavior

OBJECTIVES

We sought to determine whether analysis of the contrast signal from the radial artery is better able to reflect changes in left ventricular (LV) microbubble dynamics than the signal from the LV itself.

BACKGROUND

Assessment of microbubble behavior from images of the LV may be affected by attenuation from overlying microbubbles and nonuniform background signal intensities. The signal intensity from contrast in a peripheral artery is not affected by these artifacts and may, thus, be more accurate.

METHODS

After injection of a contrast bolus into a peripheral vein, signal intensity was followed simultaneously in the LV and radial artery. The measurements were repeated using continuous, triggered, low and high mechanical index harmonic imaging of the LV.

RESULTS

Peak and integrated signal intensities ranged from 25 dB and 1550 dB/s, respectively, with radial artery imaging to 5.6 dB and 471 dB/s with ventricular imaging. Although differences in microbubble behavior during the different imaging protocols could be determined from both the LV and radial artery curves, analysis of the radial artery curves yielded more consistent and robust differences.

CONCLUSIONS

The signal from microbubbles in the radial artery is not affected by shadowing and is, thus, a more accurate reflection of microbubble behavior in the LV than the signal from the LV itself. This may have important implications for the measurement of myocardial perfusion by contrast echocardiography.