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Sensing Savvy

Evaluating Gastroepiploic Arterial Grafts for CABG

Posted by Roger DeLong, CP, PE, MBA on May 18, 2016 6:30:00 AM

Surgeons at the University of Sapporo Japan analyzed the relationship between intraoperative transit-time flow values and post-op angiographic results of gastroepiploic arterial grafts to the right coronary artery to determine whether the flow values are reliable indicators of early graft patency in gastroepiploic to right coronary artery grafts.

Their study pool included 169 patients who underwent off-pump CABG with GEA-RCA bypass grafts. Eighty-three grafts were anastomosed and flows were measured. An angiogram was taken one week after surgery and the anastomosis of each graft was graded using FitzGibbon grading (Study 1) and graft-flow grading (Study 2).

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Topics: Graft Patency Assessment, CABG Surgery

Analysis of a Bypass Graft Waveform: 5 Things to Look For

Posted by Susan Eymann, MS on Oct 23, 2015 6:30:00 AM

Analysis of a flow waveform is useful when the mean flow of the bypass graft is questionable, between 5 mL/min and 20 mL/min. But what should one look for? First, the waveform should have a smooth, repeatable flow profile. Secondly, there generally should be clear definition of a biphasic waveform representing systole and diastole as shown in the following example of four patent grafts in an 83-year-old patient.

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Topics: CABG Case Reports, Cardiothoracic, Graft Patency Assessment

Don’t Depend on Pulsatility Index as a Sole Indicator of Graft Patency

Posted by Susan Eymann, MS on Oct 16, 2015 6:30:00 AM

Intraoperative flow measurements during coronary artery bypass grafting are performed to detect technical problems at the time of surgery when correction is relatively simple. One tool in the surgeon’s arsenal to detect a graft in trouble is Pulsatility Index that combines mean flow and waveform properties into one number. Introduced by D’Ancona and colleagues about 2000, the Pulsatility Index is simply calculated by subtracting the minimum recorded flow from the maximum recorded flow and dividing the difference by the mean flow. D’Ancona and colleagues suggested that a PI between 1 and 5 would indicate a good graft, while a PI greater than 5 would indicate a suspect graft. PI quickly caught on as a reliable indicator of graft patency and was soon added to the display screens and printouts of flowmeters to be used as a major indicator of a good graft. Studies were performed using PI as one endpoint for assessment of grafts and comparison of flowmeters.

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Topics: CABG Case Reports, Cardiothoracic, Graft Patency Assessment

Why Mean Flow is Key to Assessing Graft Patency

Posted by Susan Eymann, MS on Oct 13, 2015 3:00:00 PM

Mean flow, maximum flow, minimum flow, PI, DF% or D/S Ratio all show up on the flow monitor display. What should the surgeon consider first in assessing the patency of a bypass graft?

Mean flow is the primary indicator of graft patency. It can confirm the patency of a good graft or, conversely, signal an undesirable graft. While flows greater than 20 to 30 mL/min indicate a good graft, flows under 5 mL/min always indicate that there is a problem with the graft. Experience supports a mean flow of 30 mL/min to indicate acceptable patency. For small patients or small target vessels, this number can be reduced to 20 mL/min. European guidelines state: “Flow < 20 mL/min and pulsatility index >5 predict technically inadequate grafts, mandating graft revision before leaving the operating theatre.”1

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Topics: CABG Case Reports, Cardiothoracic, Graft Patency Assessment

Here’s Why Technique Matters in Intraoperative Flow Measurement

Posted by Susan Eymann, MS on Oct 9, 2015 6:00:00 AM

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.

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Topics: Transit-time Ultrasound, Cardiothoracic, Graft Patency Assessment

Can You Trust Your Fingertip to Feel a Pulse or a Pen-Tip Doppler to Test Bypass Graft Patency?

Posted by Susan Eymann, MS on Oct 2, 2015 6:00:00 AM

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.

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Topics: Transit-time Ultrasound, Cardiothoracic, Graft Patency Assessment

Believing What You See; Does Structure Correlate to Graft Function?

Posted by Susan Eymann, MS on Sep 14, 2015 9:30:00 AM

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.

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Topics: Cardiothoracic, Graft Patency Assessment