Improved High-Frequency Transthoracic Flow Velocity Measurement in the Left Anterior Descending Coronary Artery After Intravenous Peripheral Injection of Levovist

Abstract

New ultrasonic technology allows noninvasive measurement of the flow in the distal left anterior descending coronary artery. The goal of this study was to validate transthoracic determination of coronary flow velocity with the intracoronary Doppler flow wire technique. In 20 patients with normal coronary arteries, 2 intracoronary and 2 comparative transthoracic Doppler measurements (TTDMs) of the average peak velocity (APV) and the mean systolic and diastolic velocities were performed. The diastolic/systolic ratio was calculated. Blood flow velocity was determined in the distal left anterior descending coronary artery with a Doppler guide wire. Color Doppler and subsequent pulsed wave Doppler readings in an optimal left lateral position were available within 1 hour after completion of the invasive examinations. TTDM were performed during continuous administration of 2.0 g of contrast agent. A modified apical view was obtained from the fourth or fifth intercostal space, and a high-frequency transducer was used (7 MHz for 2-dimensional and 6 MHz for color Doppler imaging; 3.5 MHz for pulsed wave Doppler readings). The Doppler flow signal quality was graded from I to III (I = no flow mapping obtainable, II = poor quality, III = Doppler signals with a well-defined outline). In 13 (65%) patients, 26 TTDMs revealed signal quality of grade III. APV was calculated to be within normal limits (APV echo = 19.96 ± 7.62 cm/s vs APV invasive = 20.77 ± 7.87 cm/s). APV echo correlated well with APV invasive ( r = 0.85, y = 0.82 x + 2.85, P < .001). The mean difference between APV echo and APV invasive (Bias) was -0.81 ± 4.23 cm/s. No correlation was found between invasive and noninvasive measurements of diastolic/systolic velocity ratios ( P > .05). High-frequency TTDM provides reliable data on APV in the majority of patients. It has the potential to be introduced as a relevant screening test for follow-up of patients after interventional treatment. (J Am Soc Echocardiogr 1999;12:252-6.)