POSITION CONTROL OF INTRAVASCULAR DOPPLER GUIDEWIRE - CONCEPT OF A TRACKING INDICATOR AND ITS CLINICAL IMPLICATIONS

Intracoronary Doppler ultrasound guidewires (DGW) utilize a wide ultra sound beam combined with a measurement of the spectral peak velocity t o estimate the spatial peak velocity within a blood vessel. However, t he spectral peak velocity may underestimate the true spatial peak velo city if the DGW is not properly positioned. The purpose of this study was to find a Doppler-derived parameter that would aid in the optimal positioning of the DGW within the vessel lumen. We studied the relatio nship between the time-averaged, spectral-peak velocity (APV) and the normalized first Doppler moment (M1/M0) to develop a DGW position indi cator and demonstrate its clinical utility. In vitro, heparinized, hum an whole blood with a hematocrit of 45% was directed from a reservoir via a roller pump into four serially connected straight silicone tubes of known diameter (2.5, 3.0, 3.5, 4.0 mm). A DGW was inserted into th e tubes where simultaneous APV and M1/M0 measurements were obtained fo r flow rates ranging from 49 to 316 ml/min. Optimal positioning of the DGW was identified at the position where maximum APV and M1/M0 were o btained. With optimal positioning the correlation between APV and M1/M 0 was good (APV = 1.62 M1/M0 + 5.0; R-2 = 0.98). Importantly, this cor relation showed no dependence on the tube diameter. In vivo, in four p atients APV and M1/M0 measurements were obtained in 16 coronary artery segments in one left anterior descending, two circumflex, and two rig ht coronary arteries. In 10 vessel segments, there was no discrepancy between the measured and expected M1/M0 after positioning the DGW with help of the Doppler signal quality only. In six vessel segments, repe at DGW positioning using M1/M0 was necessary, yielding an average incr ease of APV of 20% (7-38%). We conclude that DGW positioning can be op timized using the correlation between APV and M1/M0 as a reference. Fo r any given APV value, there is a corresponding expected value for M1/ M0 under the condition of optimal positioning. Any discrepancy between the measured and expected values for M1/M0 then indicates suboptimal positioning. (C) 1998 Wiley-Liss, Inc.