The graft looks good, why should I bother to measure flow? Flow Specialists are often asked this question by surgeons, whose observation skills have been honed through years of training and surgical practice. Yes, we all tend to believe what we see.

“A picture is worth a 1000 words,” is a familiar adage.

We think what we see is “real.” A measurement, on the other hand, is abstract, sometimes hard to get one’s mind around unless one has a reference chart and, even then, it is often hard to determine if the number is actually “good” or real. We become skeptical of the equipment when and if it doesn’t jive with what we are seeing.

But should surgeons base their surgical decisions on just what is obvious to the eye. They shouldn’t and they don’t. "Two parameters, graft function and anatomy, are required for the complete assessment of bypass grafts”, notes Stuart J. Head, MD, Dept. of Cardiothoracic Surgery, Erasmus University Medical Center, Rotterdam, The Netherlands, in his 2013 clinical update Coronary Artery Bypass Grafting: Part2 - Optimizing Outcomes and Future Prospects.¹ When it comes to physiological function, what one sees on a coronary angiogram is not sufficient. Anatomy does disclose full function. Anatomy provides a view of one or two dimensions. Measuring flow, intraoperatively, on the other hand, provides a number that correlates to actual physiological function. It provides the clinician with a quantitative dimension of physiological information that can corroborate clinical observations. But more importantly, it can also signal a warning that a graft’s function is not as hoped or expected, even though the graft might look fine.

Just as airline pilots have to learn to trust the measurements of their instruments, so do surgeons have to learn, not just to trust just what they see, but to take a “leap of faith” to trust the flow measurements of their instruments to give them a true indicator of the physiological function of a bypass graft. It can sometimes be lifesaving!

¹Head SJ, Börgermann J, Osnabrugge RL, Kieser TM, Falk V, Taggart DP, Puskas JD, Gummert JF, Kappetein AP. Coronary artery bypass grafting: Part 2--optimizing outcomes and future prospects. Eur Heart J. 2013 Oct;34(37):2873-86.