Measurement of instant flow reserve to quantify functional flow limitation across stenosis in intracranial atherosclerotic disease.

Angiographic stenosis may not be an accurate reflection of physiological flow limitation. Measurement of instant flow reserve (IFR) to quantify functional flow limitation across stenosis may be valuable in identifying lesions causing significant flow limitation. A case of left middle cerebral artery atherosclerotic disease is presented. Because medical therapy had failed, endovascular revascularization was chosen. In this video 1, IFR measurement to guide submaximal balloon angioplasty with a 1.5×9 mm non-compliant Mini-Trek balloon (Abbott) is demonstrated. Pressure gradient across the middle cerebral artery-M1 stenosis was measured with a Volcano pressure wire (Philips) before and after submaximal balloon angioplasty. An excellent radiographic result and flow improvement into the severely stenosed segment were achieved, with an IFR increase from 0.23 to 0.89. The degree of corresponding stenosis changed from 85% to 30%. No periprocedural complication was observed. IFR can help to identify lesions requiring treatment in select patients and prevent the tendency to overtreat a lesion that is not physiologically significant.