Variation of the ‘‘Black Hole’’ phenomenon with speed and stroke rate

Abstract

The Black Hole (BH) phenomenon, a central hypoechoic hole surrounded by a hyperechoic zone, has been observed and investigated only under steady flow. The phenomenon was recently observed under pulsatile flow, but its variation during a cycle has never been reported yet. In order to better understand the BH phenomenon and its variation, a GE LOGIQ 700 Expert system was used to collect B mode images from porcine blood in a rigid tube (ID: 9.5 mm). The BH became weaker or disappeared during the systole in terms of contrast and size. The variation of the BH over a cycle was investigated with the peak speed levels (10–25 cm/s), stroke rates (20, 40, 60 beats/min), mean speed levels (10, 20 cm/s), and hematocrits (12%–46%). Under steady flow, the BH phenomenon started to appear at an asymmetrical radial position at very low speeds when speed was increased. The BH shifted to the center of the tube at higher speeds and finally disappeared at ∼100 cm/s. However, the asymmetrical position at lower speeds was not observed when speed was decreased. The variation in the BH is presumably due to the red cell aggregation, which is affected by the shear rate and acceleration during a pulsatile cycle.