Intracoronary elastography in the catheterisation laboratory: preliminary patient results

Intravascular ultrasound (IVUS) elastography is a new imaging technique that reveals regional mechanical properties of the vascular wall by measuring the local strain. In this study, the Feasibility and potential of the technique during cardiac catheterization are investigated. Presently, nine patients scheduled for percutaneous transluminal coronary angioplasty (PTCA) have been investigated. The intracoronary pressure was used as a mechanical stimulus. Local strain was estimated by cross-correlation analysis of the radio-frequency IVUS signals, obtained from two frames acquired at different pressures. Since errors are incurred with catheter motion, the phase in the heart cycle with minimal catheter motion was determined. The relation between mean strain (average strain value over the full cross-sectional circumference) and the systolo-diastolic change in lumen area was also investigated. Reliable elastographic results were obtained on sequential echo-frames near end-diastole. The elastograms reveal that regions with calcified material (as identified from the echogram) have low strain values: 0 to 0.1%. Normal vessel wall and other plaques demonstrated strain ranging from 0.1 to 1%. A high correlation was found between the mean strain at end diastole and the change in lumen over the cardiac cycle (r²=0.81, p=0.005). The results of this preliminary clinical experience suggest that it is feasible to produce clinically useful elastograms