Improved doppler detection of proximal left anterior descending coronary artery stenosis after intravenous injection of lung-crossing contrast agent: transesophageal doppler echocardiographic study

Objective. This study was designed to verify the usefulness of transesophageal Doppler recording of blood flow velocity in the proximal left anterior descending coronary artery, after peripheral injection of lung-crossing contrast agent (SHU 508A), in detecting and locating hemodynamically significant stenosis (vessel narrowing ≥50%) affecting this portion of the vessel. Background. Transesophageal Doppler echocardiography has limited diagnostic impact on the evaluation of proximal left anterior descending coronary artery stenoses. Peripheral injection of SHU 508A, lung-crossing contrast agent enhancing Doppler signal to noise ratio in coronary arteries, may allow recording of localized disturbed blood flow velocity at the stenosis site even in the absence of clear B-mode visualization of the vessel. Methods. Transesophageal Doppler echocardiography, before and after echo contrast injection, was performed in 31 patients who underwent coronary angiography. Using color Doppler as guide, pulsed wave Doppler recording of blood flow velocity in the left anterior descending coronary artery was attempted to detect localized increase in blood flow velocity. B-mode evaluation of the vessel was also performed. Results. Angiography showed significant proximal left anterior descending coronary artery stenosis in 16 patients (group 1) and no stenosis in 15 patients (group 2). In 15 of 16 group 1 patients, Doppler after contrast injection revealed localized velocity increase of at least 50% of the reference value; mean (±SD) percent increase in velocity was 150 ± 89% (range 367% to 0%). In group 2 Doppler after contrast injection revealed mild localized increase in velocity in four patients and no increase in velocity in the remaining 11 patients; mean (±SD) percent increase in velocity was 5 ± 7% (range 21% to 0%, p < 0.001 vs. percent increase in group 1). When percent velocity increase ≥50% of the reference value was considered positive criterion for detecting significant stenosis, the sensitivity and specificity were 92% and 100%, respectively. The sensitivity of the evaluation before contrast injection or considering B-mode imaging alone was much lower (25% and 19%, respectively, p < 0.001 vs. evaluation after contrast injection). In addition, color Doppler after contrast injection correctly located the stenosis along the vessel, as compared with angiography. Conclusions. Blood flow evaluation of the proximal left anterior descending coronary artery by transesophageal Doppler echocardiography after contrast injection is feasible and reliable method for detecting and locating significant stenoses affecting this part of the vessel and is an improvement over the traditional ultrasound approach.