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.
- 67-year-old male
- BMI 28,1
- Stable angina
Medistim MiraQTM Cardiac System with QuickFitTM TTFM probes (PS series) and L15 HFUS probe.
The surgical plan was to perform an Off-pump procedure and create three grafts:
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. (See 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.