Color Doppler of Diastolic Flow Converging Into Coronary Ostia by Transthoracic Ultrasound

The flow convergence method is a recently described color Doppler method for determination of flow rate across orifices in patients with valve leaks and ventricular septal defects. For a given geometry, the flow net of the flow convergence region is predictable, which allows one to derive flow rate from the local velocity at given points within the field of convective acceleration proximal to the orifice. This underlying fluid dynamic principle should also apply to coronary ostia. Therefore, we looked to see if the flow convergence region proximal to the coronary ostia can be imaged by color Doppler. In 16 healthy adults we imaged the aortic root by transthoracic color Doppler echocardiography in the parasternal short axis. A low velocity setup was used (PRF 450–2000 Hz, wall filter 50–200 Hz). Eighty-four percent of the coronary ostia was seen (left 15/16; right 12/16). A color signal of the coronary flow convergence region was displayed in 88% of coronary ostia (left 15/16; right 13/16). By quantitative analysis of these color maps the velocity profile across the flow convergence was determined. This always resulted in a steady increase in velocity when approaching the ostium. Within 2 to 18 mm proximal to the orifice, the absolute velocities ranged from 1.2 to 16 cm I sec. The coronary flow convergence region can be imaged by color Doppler. However, the potential estimation of instantaneous diastolic coronary flow rate from these images needs further evaluation.