Noninvasive transthoracic and transesophageal Doppler echocardiographic measurements of human coronary blood flow velocity: In vitro flow phantom validation

Coronary angiography is limited in assessing the hemodynamic significance of a coronary lesion or the state of the coronary microcirculation. Noninvasive transthoracic (TTE) and transesophageal (TEE) Doppler echocardiography have been used to measure coronary blood flow velocity and coronary flow reserve and thus the physiology of the coronary vasculature (normal, stable or unstable lesions). A fundamental, in vitro validation of these methods with a tissue and blood mimicking flow phantom has not been reported. Accordingly, Bland-Altman 95% confidence levels for precision (repeated measures) and accuracy (comparison with time collection) were determined for both TTE and TEE measurements of simulated coronary diastolic blood velocities in 2 mm and 4 mm vessels at the normal in vivo depths of 40 mm and 60 mm. The Doppler angle was set at 45 degrees and flow velocities were varied within a normal in vivo range of 0- 150 cm/s. Confidence levels for precisions and accuracies were similar between TTE and TEE and ranged from ±6 cm/s to ±13 cm/s or approximately 10-15% over the range of the measured velocities. These in vitro results in a controlled flow phantom suggest that technically adequate TTE and TEE can be used to reliably measure epicardial coronary conduit artery blood flow velocities.