In any bypass surgery, whether operating on the heart or leg, success depends entirely on sufficient restoration or augmentation of flow.

Visual and manual assessments indicate the graft will be successful, but are those tools sufficient? Should we entrust a patient's life to them alone?

This was exactly the situation in a femoropopliteal (fem-pop) bypass case where the surgeon followed the standard steps, and even intraoperative angiography showed a good distal anastomosis with unrestricted runoff.

The graft looked perfect. The pulses sounded fine. The patient was stable.

But something was missing and, without flow measurement, it might have gone unnoticed. 

A Closer Look at the Case

A reversed saphenous vein graft was constructed from the deep femoral artery to the above-knee popliteal artery in the right leg. Before reestablishing flow, angiography revealed no issues. Everything appeared technically successful.

But when the surgical team used Transonic’s 4 mm flowprobe to measure flow through the graft, they discovered something unexpected: both the mean flow value and the flow waveform indicated no flow in the graft, even though the blood pulses were excellent in the proximal graft.

It was a moment where another tool may have given false reassurance. But TTFM revealed the truth: there was a critical problem affecting graft function.

The Discovery: A Twisted Graft

Upon re-exposing the distal anastomosis, the team found the issue: a twist in the vein graft that was obstructing flow.

The graft was divided, untwisted and then re-anastomosed end-to-end. 

A second flow measurement showed immediate improvement of 132 mL/min. The pulses at the distal anastomoses were excellent and the foot was well perfused.

The post-operative course was uneventful. The patient remained asymptomatic and the graft was still patent two years later.

Why Flow Measurement Matters in Lower Limb Bypass

This case reflects a broader truth about infrainguinal bypass procedures like fem-pop, fem-fem, and fem-tib:

• Even visually perfect grafts can have hidden issues
• Visual inspection and Doppler alone can miss them
• Transit-time flow measurement provides objective, beat-to-beat confirmation that blood is actually moving through the graft at sufficient volume

Had the flow not been measured in this case, the graft might have failed. The patient may have returned days or weeks later, facing a very different outcome.

Instead, a quick, non-invasive flow check changed everything. That’s the power of TTFM. 

Learn more about why confirming flow in lower limb bypass procedures makes all the difference.