Use of myocardial backscatter as a quantitative tool for dobutamine echocardiography: feasibility, response to ischemia and accuracy compared with coronary angiography.
BACKGROUND
Integrated backscatter (IB) changes with ischemia, but most prior studies have involved parasternal imaging, which limited the number of evaluable segments. We sought to assess the efficacy and feasibility of IB from the apical views, and compare this to myocardial Doppler findings and wall motion analysis during dobutamine echocardiography.


RESULTS
Forty-one patients undergoing dobutamine echocardiography had gray scale images and color myocardial Doppler acquired in three apical views. Cyclic variation IB (CVIB), time to peak IB (tIB, corrected for QT interval) and Doppler peak velocity (PV) in the same segment at rest and peak stress were assessed offline from digital cineloops at 80-120 frames/s. Significant coronary disease was defined by quantitative angiography as > 50% stenosis. Analysis of the waveform in the apical views was feasible in 82% of segments. The backscatter curve was shown to be biphasic, with correlation of the first peak with peak tissue velocity, and significant regional variation. However, the response to normal segments was different with tissue Doppler (increased velocity) and backscatter (no change). Ischemia was associated with a lower peak tissue velocity and lower CVIB. Only resting tissue velocity and tIB (not CVIB) distinguished scar from ischemic segments. Using an optimal cutoff of < 5.3 dB at rest achieved a sensitivity of 55%, a specificity of 76% and an accuracy of 75% when compared to angiography. The same cutoff at peak achieved a sensitivity of 58%, a specificity of 80% and an accuracy of 76%.


CONCLUSIONS
CVIB and tissue velocity responses to stress are different, but both may be used to identify abnormal segments in patients with CAD. However, while measurement of CVIB is feasible in the apical views, the variability caused by anisotropy limits the accuracy of a single cutoff.
Dart
Jared
J
Department of Medicine, University of Queensland, Princess Alexandra Hospital, Brisbane, Australia.
Yuda
Satoshi
S
Cain
Peter
P
Case
Colin
C
Marwick
Thomas H
TH
D000328:Adult; D000368:Aged; D017023:Coronary Angiography; D003327:Coronary Disease / Q000000981:diagnostic imaging*; D003971:Diastole / Q000502:physiology; D025401:Echocardiography, Stress / Q000379:methods*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging*; D012372:ROC Curve; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity