Multiple blood flow measurements before and after carotid artery stenting via phase-contrast magnetic resonance imaging: An observational study

Abstract

After carotid artery stenting, the procurement of information about blood flow redistribution among brain-feeding arteries and its time trend is essential to understanding a patient's physiological background and to determine their care regimen. Cerebral blood flow has been measured twice following carotid artery stenting in few previous studies, with some discrepancies in the results. The purpose of this study was to measure cerebral blood flow at multiple time points after carotid artery stenting, and to elucidate the time trend of cerebral blood flow and redistribution among arteries. Blood flow rates in 11 subjects were measured preoperatively, at one day, one week, and about three months, respectively after carotid artery stenting by using phase-contrast magnetic resonance imaging. The target vessels were the bilateral internal carotid arteries, the basilar artery, and the bilateral middle cerebral arteries. Lumen was semi-automatically defined using an algorithm utilizing pulsatility. The results showed that blood flow rates in the stented internal carotid artery and the ipsilateral middle cerebral artery increased following carotid artery stenting. Blood flow rates in the contralateral internal carotid artery and the basilar artery gradually declined, and they were lower than the preoperative values at three months after stenting. The sum of blood flow rates of the bilateral internal carotid arteries and the basilar artery increased after carotid artery stenting, and then decreased over the next three months. There was no significant change in the blood flow rate in the contralateral middle cerebral artery. From these results, it was concluded that redistribution among the bilateral internal carotid arteries and the basilar artery occurs after carotid artery stenting, and that it takes months thereafter to reach another equilibrium.

Fig 1. Imaging plane for blood flow rate measurement in the bilateral internal carotid arteries and the basilar artery.

The plane is set as close to perpendicular as possible to these three arteries using the lateral view of the maximum intensity projection image of a three-dimensional magnetic resonance angiograph. Thus, the blood flow rates were measured in the presellar or posterior vertical segment of the cavernous portion of the internal carotid artery and basilar artery. The arteries in these anatomical locations run in a fairly straight manner and have low turbulence.

Fig 2. Flow rates of the stented internal carotid artery (solid line) and contralateral internal carotid artery (dotted line).

Horizontal bars and boxes represent mean and mean +/- standard deviation, respectively. Compared to preoperative values, the flow rates of the stented internal carotid artery after carotid artery stenting (CAS) are significantly larger. Compared to preoperative values, the flow rate of the contralateral carotid artery at 3 months after CAS is significantly smaller.

Fig 3. Flow rate of the basilar artery.

Compared to the preoperative value, the flow rate at 3 months after CAS is significantly smaller.

Fig 4. Sum of flow rates of the bilateral internal carotid arteries (ICAs) and the basilar artery.

The sum increases after CAS, then decreases over the next 3 months.

Fig 5. Flow rates of the middle cerebral artery ipsilateral to the stented internal carotid artery (solid line) and contralateral middle cerebral artery (dotted line).

The flow rate of the stented side middle cerebral artery increases after CAS and its trend is similar to that of the stented internal carotid artery. The flow rate of the contralateral one does not show significant changes.