An improved intravascular ultrasonic Doppler device could aid the clinical assessment of coronary hemodynamics. We evaluated a new device consisting of a 12-MHz piezoelectric transducer integrated onto the tip of a 0.018-in. flexible, steerable angioplasty guide wire.

Doppler spectra were recorded in model tubes with pulsatile blood flow and in-line electromagnetic flowmeter. In four straight tubes (i.d., 0.79-4.76 mm), the time average of spectral peak velocity (APV) was linearly related to blood flow (QEMF) (r2 greater than or equal to 0.98 for each tube). A Doppler-derived quantitative flow estimate (QD) was calculated as the product of vessel cross-sectional area and mean velocity, with mean velocity estimated as 0.5 x APV. The slope of QD versus QEMF for the four tubes was near unity. APV was less accurate in a 7.94-mm straight tube and in tortuous segments. In four dogs, the left circumflex coronary artery (LCx) was perfused from the femoral artery via a cannula with in-line electromagnetic flowmeter. Good-quality signals were obtained in proximal and distal LCx vessels 3.3-1.2 mm in diameter. APV varied linearly with QEMF (r2 greater than or equal to 0.99 in the cannula, r2 = 0.93-0.99 in proximal LCx, and r2 = 0.86-0.99 in distal LCx). QD was calculated by quantitative angiography to determine proximal LCx diameter. For all dogs combined, the slope of QD versus QEMF was 0.95 in the cannula and 0.85 in the proximal LCx.

The Doppler guide wire measures phasic flow velocity patterns and linearly tracks changes in flow rate in small, straight coronary arteries. It should facilitate measurement of phasic coronary flow velocity during coronary angiography and angioplasty.