Transonic history is providentially intertwined with the development of circulatory support and Ventricular Assist Devices. In 1971, Transonic founder Cornelius Drost was slated to join The Cleveland Clinic bioengineering department under Chairman Dr. Yukihiko Nose to work on projects that included development of centrifugal and axial blood pumps for cardiac assist. When grant funding fell through, Drost went to work at Cornell University to design a more reliable Doppler flowmeter to measure blood flow in conscious animals. The invention was a transit-time volume Flowmeter that would be used in the engineering and testing of almost every circulatory support device that followed.
You’ve undoubtedly heard of the importance of using technology to determine graft patency during CABG surgery. Objective measurements, instead of subjective methods like palpation, helps ensure a graft is functioning properly, thus improving patient outcomes and reducing the need for repeat surgeries.
When it comes to techniques to evaluate CABG graft patency, options include transit-time ultrasound technology and Doppler technology. This post will take a look at both, allowing you to make an informed decision.
Introduced by Cornelis Drost during the last quarter of the last century, transit-time ultrasound technology has become recognized as the gold standard for accurate intraoperative volume flow measurements. Measurements are quick, simple and repeatable. However, in order to achieve accurate flow measurements, good technique matters.
The seeds for transit-time ultrasound intraoperative measurement during CABG surgery were planted 40 years ago when a young Dutch engineer Cornelis (Cor) Drost came to work as a research associate at the NYS Veterinary College at Cornell University, Ithaca, NY. Cor was tasked by Professor of Physiology Dr. Alan Dobson with figuring out how to measure the amount of blood flowing through blood vessels in a manner that would not have to interfere with the flow inside the vessel itself.
Some surgeons ask, “What advantage is there to measuring flow? I am used to palpating the graft to sense flow.” Palpation or feeling a pulse simply indicates that the vessel is connected to the heart. It might give a qualitative indication of the presence of a pulse, but does not detect an occlusion downstream from the point of palpation (i.e., the distal anastomosis). Experienced surgeons may have developed a “feel” for flow by partially occluding the graft and feeling a turbulent thrill to provide a sense that something is passing through the graft. If a partial occlusion exists, the proximal pulse will increase, the distal pulse will decrease. Detecting an arterial obstruction from the pulse is a tenuous art form at best, but may provide the experienced surgeon with qualitative information in cases where the vessel can be palpated. It is quick and inexpensive, but is not quantitative. Flow measurement, on the other hand, provides an unique opportunity to “look inside” the graft and make a quantitative, not qualitative, assessment of graft patency.