Fractional Flow Assessment for the Evaluation of Intracranial Atherosclerosis: A Feasibility Study

Abstract

Purpose: Current studies on endovascular intervention for intracranial atherosclerosis select patients based on luminal stenosis. Coronary studies demonstrated that fractional flow measurements assess ischemia better than anatomical stenosis and can guide patient selection for intervention. We similarly postulated that fractional flow can be used to assess ischemic stroke risk. Methods: This was a feasibility study to assess the technical use and safety of applying a pressure guidewire to measure fractional flow across intracranial stenoses. Twenty patients with severe intracranial stenosis were recruited. The percentage of luminal stenosis, distal to proximal pressure ratios (fractional flow) and the fractional flow gradients across the stenosis were measured. Procedural success rate and safety outcomes were documented. Results: All 20 patients had successful crossing of stenosis by the pressure guidewire. Ten patients underwent angioplasty, and 5 had stenting performed. There was one perforator stroke, but not related to the use of the pressure wire. For the 13 patients with complete pre- and postintervention data, the mean preintervention stenosis, fractional flow and translesional pressure gradient were 76.2%, 0.66 and 29.9 mm Hg, whilst the corresponding postintervention measurements were 24.7%, 0.88 and 10.9 mm Hg, respectively. Fractional flow (r = -0.530, p = 0.001) and the translesional pressure gradient (r = 0.501, p = 0.002) only had a modest correlation with the luminal stenosis. Conclusion: Fractional flow measurement by floating a pressure guidewire across the intracranial stenosis was technically feasible and safe in this study. Further studies are needed to validate its use for ischemic stroke risk assessment.

Hemodynamics and stroke risk in intracranial atherosclerotic disease

“…33,36 In addition, WSS quantified with CFD models has been associated with progression of atherosclerotic plaques and arterial remodeling in CAD. There have been reports measuring pressure gradient across sICAS lesions using pressure guidewire during performance of cerebral angiography in small case series; 37,38 however, this could not be widely applied by far. 30,34,35 Compared with extracranial arteries, however, hemodynamics in intracranial arteries are more difficult to assess with invasive imaging methods, due to the anatomic features of intracranial arteries (eg, small calibers, tortuosity, and deep locations of the arteries within the skull).…”

“…30,34,35 Compared with extracranial arteries, however, hemodynamics in intracranial arteries are more difficult to assess with invasive imaging methods, due to the anatomic features of intracranial arteries (eg, small calibers, tortuosity, and deep locations of the arteries within the skull). There have been reports measuring pressure gradient across sICAS lesions using pressure guidewire during performance of cerebral angiography in small case series; 37,38 however, this could not be widely applied by far. Conversely, although noninvasive imaging methods such as CT or magnetic resonance perfusion imaging, or quantitative magnetic resonance angiography (MRA) could gauge whole-brain or territorial blood flow, these imaging methods could not directly quantify hemodynamic metrics such as intra-arterial pressure and WSS.…”

Effect of revascularization on cognitive outcomes in intracranial steno-occlusive disease: a systematic review

“…Floating a pressure guidewire across a region of intracranial stenosis as a means of measuring fractional flow reserve (FFR, maximal blood flow in a stenotic artery divided by normal maximal flow in a nonstenotic artery) may represent a superior way of assessing cerebral ischemia when compared with angiographic evaluation. 32 Data from randomized trials in interventional cardiology showed that using FFR as opposed to angiographic assessment to guide endovascular intervention resulted in a significant reduction in the composite endpoint of death, nonfatal myocardial infarction, and re-peat revascularization at 1 year. 42 A trial assessing the cognitive effects of revascularization in patients chosen using FFR would be a welcome addition to the literature.…”

Intracranial artery stenosis: Current status of evaluation and treatment in China

“… 43 The first study in which pressure guidewire was floated across the intracranial lesion site to measure fractional flow reserve (FFR), a superior approach to anatomic stenosis for determining ischemic risk in coronary research, was conducted by a group of neurologists from China and the USA in ICAS. 44 The preliminary outcome indicated that fractional flow measurement across intracranial artery lesions with a pressure guidewire was technically feasible and safe. 44 Moreover, based on the CFD method, the researchers designed a non-invasive technique for computing the fractional pressure ratio (FPR), to evaluate the hemodynamic significance of severe ICAS; they found that this non-invasive parameter was comparable with the invasive parameter.…”