Transonic HT331-FT - Page 46

40 AU-OPR-AureFloFT-EN,
Rev H
2) ASSESS FLOW WAVEFORM OF A BEATING HEART CABG GRAFT
a) Under the conventional “look and listen” waveform assessment approach, the Flowmeter’s
FlowSound
®
feature is turned on. By looking at the heart to discern systolic (contracting) and
diastolic (relaxing) phases of the heart, FlowSound
®
provides the surgeon with a quick impression
whether graft ow is:
i) Diastolic dominant (far higher pitch during diastole than during systole);
ii) Systolic-diastolic balanced (similarly pitched waves during systole and diastole);
iii) Systolic-dominant (far higher pitch during systole than during diastole).
b) Flow resistance of the myocardium is high (meaning: perfusion ow is low) during cardiac
contraction. This effect is far more pronounced in coronaries perfusing the left ventricle than those
perfusing the right ventricle and the atria, and the effect will be reduced in diseased left ventricular
myocardium. This leads to the following rules:
i) For grafts to left ventricle coronaries; a Diastolic dominant ow waveform indicates a good
graft;
ii) For grafts to right ventricle coronaries, a Diastolic-Systolic balanced ow waveform indicates a
good graft;
iii) A ow waveform with a stronger systolic component warrants further evaluation of possible
technical error. Please refer to Transonic
®
“Flow-Based Intraoperative Coronary Graft Patency
Assessment” booklet for more information. Briey, any kind of partial ow restriction in the
graft will create a condition where ow can be pushed past the restriction, only during systole
when blood pressure is highest. As a result, the systolic portion of the ow waveform will
become more pronounced.
c) With FlowTrace
®
and ECG signal connected, Flowmeter software will take over the task of discerning
systolic and diastolic phases of the heart, compare the volumes of blood delivered during diastole
and systole, and report their ratio as the D/S Ratio. We recommend that you take a full waveform
Snapshot: minimum of 8 seconds of stable ow recording. The D/S ratio is then calculated over the
full 8 seconds of data with good rejection of ow artifacts and noise. Graft waveform acceptance
criteria now are as follows:
i) D/S Ratio >2 = Diastolic Dominant ow waveform, indicating a good left heart graft;
ii) D/S Ratio >1 = a Diastolic-Systolic Balanced (or better) ow waveform, indicating a good right
heart graft;
iii) D/S Ratio < 1 indicates a Systolic-dominant waveform and possible technical error.
d) During CABG surgery, the screen will also report Pulsatility Index (PI): the spread in ow between
maxima and minima in the ow waveforms, divided by the average ow. Generally, a PI >5 is
considered an indication of possible technical error. HOWEVER, TRANSONIC
®
RECOMMENDS THAT
PI IS USED ONLY AS A TERTIARY INDICATION. While PI combines a measure of average ow (rst
qualier) with ow waveform (second qualier) it disregards all the information present in the
systolic-diastolic ow distribution.
3) TROUBLESHOOTING A GRAFT WITH SUSPECTED TECHNICAL ERROR.
Refer to Transonic
®
“Flow-Based Intraoperative Coronary Graft Patency Assessment” booklet for more
possible causes to be considered.
We recommend that you do this using FlowSound
®
and the Flowprobe connected to the anastomotic
side of the graft. In case of errors such as a partially occluded anastomosis because of a stitch that
picked up a back wall, FlowSound
®
may give immediate clues when the orientation of the graft onto
the heart is altered.
ECG Signal, D/S Ratio & DF