The femoral segment is the ideal segment for duplex ultrasound investigations. The diagnostic accuracy in skilled hands is about 90%; it is noninvasive and risk free and is an excellent tool to plan endovascular interventions in the entire femoral segments. In our practice, duplex sonography is the only required imaging method for isolated femoral interventions. Furthermore, duplex ultrasound can be used for evaluation of stents or bypasses in the femoral area. Using the peak velocity ratio (PVR: ratio between the maximum systolic flow within the stenosis compared to the systolic velocity in the pre-stenotic segment), an estimation of the degree of stenosis can be given, which nicely corresponds to angiography. Usually, a PVR of 2.4 or 2.5 is considered indicative of a flow-limiting stenosis with a degree of at least 50%. Limitations of duplex ultrasound are as follows:

(contrast-enhanced magnetic resonance angiography—ce-MRA) can be considered as the new gold standard for evaluation of the lower limb arteries. The diagnostic accuracy particularly in the femoral ­segment is above 95%, the diagnostic accuracy is not affected by calcification and it can be used to plan endovascular as well as surgical interventions. Nevertheless, there are some limitations of ce-MRA: it tends to overestimate the degree of stenosis—short high-grade stenoses are frequently displayed as complete occlusions. Furthermore, ce-MRA has to be carefully used in patients with severe renal dysfunction due to the risk of nephrogenic fibrosis. In patients with stents, artifacts usually make the interpretation of the remaining lumen problematic. Finally, general contraindications for MR like pacemakers or metal implants have to be considered. In clinical practice, a certain percentage (approximately 5%) of the patients therefore is not suitable for MRA.

In contrast to the predominant role of CTA for assessment of aortoiliac disease, heavy calcification frequently limits the usefulness of CTA for assessment of the femoral segment. CTA has the definite advantage of adequately assessing stents and instent-restenosis, but has problems with calcification, includes the use of iodinated contrast administration and radiation.

This method remains the most accurate way of assessing the vasculature and has to be done routinely immediately before all endovascular interventions. Femoral angiography can be done via an ipsilateral antegrade access by direct puncture of the CFA at the level of the femoral head, by contralateral access via retrograde puncture of the contralateral CFA and an over-the-bifurcation approach or alternatively via a left (preferred) or a right transbrachial or transradial access. Contrast injection can be done manually in doses of 5–10 ml (diluted) contrast, which is the preferred way for selective injection, or via an automated flush injection to the distal aorta, when bilateral overview angiograms are acquired. The usual dosage for an automated overview angiogram to the distal aorta using a pig-tail catheter is 20 ml contrast injected within 10 s.

Patients receive therapy with aspirin (100 mg) and clopidogrel (75 mg) in preparation for stent implantation. If clopidogrel is started less than 7 days before the intervention, a loading dose with 300 mg is administered 1 day pre-procedure or 600 mg at the day of the procedure. Patients should be well hydrated. During the intervention, we administer 2.000–5.000 IU (rarely 7.000) unfractionated heparin, depending on the length of the intervention. ACT monitoring is not routinely used at our institution.

Generally, we prefer the contralateral crossover approach (Fig. 25.2

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