Intra-arterial Fractional Flow Reserve Measurements Provide an Objective Assessment of the Functional Significance of Peripheral Arterial Stenoses

Figures

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  Figure 1. Procedural steps for measuring resting pressure (Pd/Pa) and fractional flow reserve (FFR). (A) For iliac artery stenoses, resting aortic pressure, Pa, is obtained via a 5 French catheter placed in the distal aorta using contralateral femoral access. Pressure distal to the index lesion (asterisk), Pd, is acquired concurrently using a ComboWire inserted via the ipsilateral femoral sheath. Adenosine is administered distal to the index lesion via the ipsilateral femoral sheath. FFR is defined as the lowest Pd/Pa ratio following administration of adenosine. (B) For superficial femoral artery stenoses, single femoral access from the contralateral limb was obtained and a long 6 French sheath to measure Pa. The lesion was crossed with a ComboWire and microcatheter, which was used to administer adenosine then immediately fully retracted. The ComboWire is kept in place to allow measurement of Pd distal to the lesion. FFR is defined as the lowest Pd/Pa ratio following administration of adenosine. (C) Representative digital subtraction angiogram of a left common iliac artery stenosis demonstrating bilateral access with sheath, catheter, and ComboWire positioning. Subsequent Pd (black), Pa…

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  Figure 2. Relationship between resting and hyperaemic pressure indices and lesional diameter stenosis measured angiographically. In non-stenosed arteries and those with minimal stenoses (< 30% diameter stenosis), Pd/Pa (distal lesion pressure/distal aortic pressure) (black circles) and fractional flow reserve (FFR) (red triangles) are comparable. Lesions in the 30 – 79% diameter stenosis range were not well discriminated using resting Pd/Pa index and required FFR measurement after provocation of hyperaemia by adenosine to unmask the true extent of haemodynamic impairment. Lesions over 80% diameter stenosis demonstrated lower Pd/Pa values and could be haemodynamically discriminated from lesions less than 80% diameter stenosis using resting Pd/Pa measurements alone. Curves fitted using second order polynomial, and bars represent standard error of mean. APV = average peak velocity.

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  Figure 3. Association between standard of care assessments and intra-arterial pressure–flow measurements with critical limb threatening ischaemia. Receiver operator characteristic curve analysis with corresponding area under the curve (AUC), 95% confidence interval (CI), and sensitivity (Sens) and specificity (Spec) values. Fractional flow reserve (FFR) demonstrates the greatest AUC for association with critical limb threatening ischaemia in this cohort of patients. Pa = distal aortic pressure; Pd = distal lesion pressure; CT % DS = computed tomography percentage diameter stenosis; eABPI = exercise ankle brachial pressure index; PSVR = peak systolic velocity ratio.

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  Figure 4. Scatterplot of blood oxygenation level dependent cardiovascular magnetic resonance derived limb perfusion and corresponding angiographic metrics, and non-invasive and invasive haemodynamic indices. Relationship between limb tissue oxygenation (T2∗ gradient) and (A) fractional flow reserve, (B) Pd/Pa (distal lesion pressure/distal aortic pressure), (C) computed tomography percentage diameter stenosis (CT % DS), (D) invasive angiography percentage diameter stenosis (IA % DS), (E) peak systolic velocity ratio (PSVR), and (F) exercise ankle brachial pressure index (eABPI).

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  Figure 5. Change in fractional flow reserve (FFR) values after angioplasty and stenting of lesions and association between post-intervention FFR and treatment failure. (A) Per lesion change in FFR following angioplasty and stenting of index lesion, grouped according to patients with clinical improvement and those with persistent signs and symptoms at follow up. (B) Post-percutaneous transluminal angioplasty (PTA) FFR cut off value corresponding to the maximum Youden index for predicting revascularisation. ∗Comparison of mean ΔFFR (pre- and post-PTA) between the two groups of resolved and persistent symptoms.