IDENTIFICATION OF CORONARY-ARTERY STENOSES AND POSTSTENOTIC BLOOD-FLOW PATTERNS USING A MINIATURE HIGH-FREQUENCY EPICARDIAL TRANSDUCER

Background Intraoperative epicardial coronary Doppler ultrasound has t he potential to provide anatomic and functional information. This tech nique has been hindered by the large size of standard transducers, but a miniature transducer is available that may fulfill the potential of coronary ultrasound. Methods and Results Twenty consecutive patients who were undergoing coronary artery bypass grafting were studied and c ompared with 9 control patients with normal coronary arteries who were undergoing routine mitral valve surgery. A miniature 6.5-MHz transduc er was used to image coronary arteries and measure coronary blood flow velocities. Seventeen proximal left anterior descending and 3 right c oronary artery stenoses were studied. As defined by coronary angiograp hy (1 to 34 days before surgery), there were 13 severe stenoses (> 70% ), 4 moderate stenoses (40% to 70%), 2 minor stenoses (< 40%), and 1 s ubtotal occlusion. Stenoses were readily identified by ultrasound. Col or flow mapping demonstrated laminar how in normal arteries and nonlam inar flow across moderate and severe stenoses. In the control patients with unobstructed arteries, peak and mean diastolic velocities were 3 5 +/- 2.1 and 26 +/- 1.9 cm/s with peak and mean systolic velocities o f 16 +/- 1.4 and 11 +/- 0.8 cm/s, respectively. Prestenotic flow veloc ities were not significantly different from normal control values, but a wide range of poststenotic flow disturbances were detected. Analysi s of the 20 study patients did not reveal significant differences in p oststenotic compared with prestenotic flow. A subgroup analysis of 12 patients with severe left anterior descending coronary artery stenoses was performed, and reversed poststenotic systolic flow was seen in 9. Prestenotic peak and mean systolic velocities were 16.5 +/- 1.7 and 1 1.9 +/- 1.1 cm/s, respectively, and were significantly altered downstr eam of the stenoses at -22.7 +/- 17.2 and -15.9 +/- 10.9 cm/s (P < .05 and P < .01, respectively). Reversed systolic flow was seen only dist al to severe left anterior descending coronary artery stenoses and did not correlate with retrograde collateral filling as determined by pre operative coronary angiography. Moderate stenoses appeared to increase both systolic and diastolic components of poststenotic flow. Conclusi ons Epicardial Doppler ultrasound with a miniature transducer identifi es coronary stenoses and associated blood flow disturbances. Compared with moderate lesions, severe stenoses demonstrated different poststen otic flow patterns. Intraoperative use of this technique may determine the hemodynamic significance of coronary stenoses.