TTFM & HFUS verifies graft patency in graft with competitive flow

Graft patency verification can be difficult in cases with competitive flow. This case from the REQUEST study describes how the combined use of Transit Time Flow Measurement (TTFM) and High-Frequency Ultrasound (HFUS) allowed the surgeon to make informed decisions about how to proceed.

Case story

Patient information

  • 67-year-old male
  • BMI 28,1
  • Stable angina

Intraoperative completion control

The surgical plan was to perform an Off-pump procedure and create three grafts:

  • LIMA-OM2
  • RIMA-LAD
  • SVG-RCA

The LIMA-OM2 and SVG-RCA grafts were uneventful, but the RIMA-LAD graft had unsatisfactory TTFM readings (Image 1). The Mean flow is very low (3 ml/min), Pulsatility Index is high (PI = 11,6), the Diastolic Filling is low (DF 38%) and the waveform is very spiky and erratic. Competitive flow was suspected.

The TTFM was repeated with the proximal part of LAD compressed (snare test) (Image 2). The readings improved significantly. Mean flow and DF% increased to acceptable levels and PI decreased drastically. The waveform also became smoother and more repetitive. These improvements indicate a severe case of competitive flow.

HFUS was used on the anastomosis and confirmed both forward and backward flow. Additionally, the HFUS showed an obstruction in the anastomosis. (Image 3)

Revision of the anastomosis was performed post protamine due to suspected stitch issue. The TTFM  was recorded post revision and shows a slight improvement in the parameters. The PI was still higher than the surgeon would normally prefer but with the snare test indicating a case of severe competitive flow further revisions would likely not improve the results anymore. (Image 4)

This case shows how the combination of TTFM and HFUS can be used to help indicate competitive flow due to low grade stenosis in the native artery as the cause of suboptimal graft performance. In this case HFUS also uncovered a technical issue that could be resolved immediately.

Case attachments

Click images below to view.
MiraQ instrument monitor presenting collected data information

RIMA-LAD graft with unsatisfactory TTFM

RIMA-LAD graft with unsatisfactory TTFM

TTFM reading of RIMA-LAD

Improved TTFM during snare test

Improved TTFM during snare test

HFUS shows an obstruction in anastomosis

HFUS of the anastomosis

HFUS of the anastomosis

TTFM reading showing a RIMA-LAD

TTFM after revision of the anastomosis

TTFM after revision of the anastomosis

MiraQ instrument monitor presenting collected data information
Image 1

Image 1

TTFM reading of RIMA-LAD
Image 2

Image 2

HFUS shows an obstruction in anastomosis
Image 3

Image 3

TTFM reading showing a RIMA-LAD
Image 4

Image 4

Reference

REQUEST study

Registry for Quality Assessment with Ultrasound Imaging and Transit-time Flow Measurement in Cardiac Bypass Surgery

Taggart DP et al. Intraoperative transit-time flow measurement and high-frequency ultrasound assessment in coronary artery bypass grafting. J Thorac Cardiovasc Surg. 2019; 159: 1283-1292.
DOI: https://doi.org/10.1016/j.jtcvs.2019.05.087

Technology used

Medistim MiraQTM Cardiac System with QuickFitTM TTFM Probes (PS series) and L15 High-Frequency Ultrasound Imaging Probe.

MiraQ instrument monitor presenting collected data information

RIMA-LAD graft with unsatisfactory TTFM

RIMA-LAD graft with unsatisfactory TTFM

TTFM reading of RIMA-LAD

Improved TTFM during snare test

Improved TTFM during snare test

HFUS shows an obstruction in anastomosis

HFUS of the anastomosis

HFUS of the anastomosis

TTFM reading showing a RIMA-LAD

TTFM after revision of the anastomosis

TTFM after revision of the anastomosis