Evaluation of the capabilities of a steerable ultrasound Doppler catheter to provide quantitative coronary flow indices

A compliant flow-through coronary cast and an in-vitro coronary flow system with physiologic flow were developed to evaluate, by comparison with laser Doppler anemometry (LDA), the capability of a 3F Millar steerable ultrasound Doppler catheter to provide coronary blood flow velocity and coronary vasodilator reserve. Doppler catheter and LDA phasic velocities were measured at four sites in the left anterior descending (LAD) and left circumflex (LCX) coronary arteries, for five mean flow rates ranging from 60 ml/min to 300 ml/min. Temporal mean velocities were calculated from the phasic data. Linear regressions were made of mean velocity versus flow rate for each testing condition to assess the statistical significance of the differences between: velocities measured with the Doppler catheter and with LDA; near wall and center-line velocities; and LDA measurements made with and without the catheter present. Analyses show that while the catheter is capable of providing relative velocity change, it underestimates the local blood velocity by 20% to 50% depending on the measurement location. The catheter is generally non-obstructive when properly positioned parallel to the flow direction in a straight segment of the artery. However, it has considerable effect on the flow field in measurement locations with complex geometry, such as bends and bifurcations. Values of coronary reserve given by the Doppler catheter correlate well with the known values on average, but the reliability of a single measurement is poor.

Duke Scholars

Author Morton Friedman Biomedical Engineering