Flow-diverting stents have provided a new endovascular capacity to reconstruct an intracranial aneurysm with its diseased parent artery. The results of first-generation flow diversion stents have been encouraging, with even large or giant treated aneurysms achieving complete angiographic occlusion at 12-month follow-up. Numerous clinical reports have described a slow progressive thrombosis pattern and gradual increase in rate of complete aneurysm obliteration over time. Despite promising early results, some complications specific to flow-diverting stents have been encountered. Chief among them is delayed aneurysm rupture. This complication did not emerge with stent-assisted coil embolization of intracranial aneurysms, and the underlying cause has not been established. However, new evidence suggests that persistent, or even increased, aneurysm pressure after stent placement may play a role in some delayed ruptures. We sought to evaluate this phenomenon by measuring intrasaccular pressure before and after stent placement using two different 0.014 inch coronary pressure measurement wires. Two patients with giant internal carotid artery aneurysms treated with flow-diverting stents were evaluated. Before and after stent deployment, intrasaccular aneurysm and systemic arterial pressures were recorded for 60 s and compared. In both cases, intrasaccular pressure measurement with the use of 0.014 inch pressure wire system was feasible; the pressure wires could be pushed out of the microcatheter placed in the aneurysms without friction or unexpected microcatheter motion. Despite successful flow-diverting stent deployment and angiographic flow diversion effects with excellent wall opposition across the aneurysm necks, there was no significant difference between intrasaccular and systemic pressures.
- Blood Flow
- Blood Pressure
- Flow Diverter
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Flow-diverting stents have provided a new endovascular capacity to reconstruct an intracranial aneurysm with its diseased parent artery.1–3 Flow diverters are constructed from high-density braided mesh, which alters intra-aneurysmal hemodynamics without any coils and leads to obliteration of the aneurysm by inducing thrombus formation.2 ,4–6 The results of the first-generation flow diversion stent, Pipeline, have been very encouraging. Lylyk et al3 reported their single-center experience with Pipeline in 53 patients with 63 intracranial aneurysms. Despite nearly half of the aneurysms being large or giant, complete angiographic aneurysm occlusion was achieved in 95% at 12-month follow-up.3 The slow progressive thrombosis and gradual increase in the rate of complete aneurysm obliteration over the follow-up period were also observed in other clinical reports.1–3 ,7
Despite promising early results, some complications specific to flow-diverting stents have been encountered. Delayed aneurysm rupture after the placement of flow diverters as well as the need for supplementary loose coil packing may occur despite high aneurysm obliteration rates.7–10 Delayed rupture did not emerge as a therapeutic concern with stent-assisted coil embolization of intracranial aneurysms, and the underlying cause of this recent complication has not been established. However, new clinical evidence and computational hemodynamic analysis suggest that persistent, or even increased, aneurysm pressure after flow diverter stent placement may play a role in some delayed ruptures.10 ,11 We sought to evaluate this phenomenon by measuring intrasaccular pressure before and after Pipeline stent placement in a supraclinoid internal carotid artery (ICA) aneurysm and a cavernous ICA aneurysm. Two different 0.014 inch coronary pressure measurement wires were used to evaluate the feasibility of intracranial intervention.
Materials and methods
Two patients scheduled to undergo routine treatment of ICA aneurysms with the use of flow-diverting stents agreed to participate in the study. This procedure is routinely performed during coronary angiography.12 ,13 Before and after stent deployment, intrasaccular aneurysm pressure was recorded with a 0.014 inch pressure wire for 60 s. Simultaneous measurement of systemic arterial pressure was recorded from a radial artery line. Systolic, diastolic, and mean arterial pressures between the radial artery and aneurysm sac were compared.
An elderly patient presented with multiple intracranial aneurysms, the largest arising from the right cavernous ICA, projecting inferolaterally, partially thrombosed, and the patent part measuring 19 mm (CC)×16 mm (TR)×13.7 mm (AP). The aneurysm neck was wide, measuring approximately 15.7 mm. It was discovered incidentally during evaluation for diplopia. The patient was placed on aspirin (325 mg daily) and clopidogrel (75 mg daily) 4 days prior to the procedure.
Under general anesthesia, a 6 Fr Shuttle guiding sheath (Cook Medical, Bloomington, Indiana, USA) was placed in the right carotid bifurcation. A 125 cm DAC 057 catheter (Stryker Neurovascular, Fremont, California, USA) was then advanced into the petrous segment of the right ICA over a 150 cm Marksman 027 microcatheter (Covidien/ev3 Neurovascular, Irvine, California, USA) preloaded with an Xpedion 14 guidewire (Covidien/ev3 Neurovascular). The Marksman microcatheter was advanced into the distal M1 segment. A 5×30 mm Pipeline stent device was then inserted into the Marksman catheter and pushed up to the tip of the catheter. Prior to the delivery of the Pipeline stent, an Echelon 10 microcatheter was navigated into the aneurysm dome over an Xpedion 14 guidewire via the Shuttle guiding sheath. A PressureWire Aeris (St Jude Medical, St Paul, Minnesota, USA) pressure measurement wire was advanced into the aneurysm via the Echelon 10 microcatheter and several intrasaccular pressure measurements were made. After the measurement, the PressureWire was pulled back into the Echelon microcatheter. Subsequently, the Pipeline stent was deployed across the neck of the aneurysm extending from just proximal to the ophthalmic artery takeoff, across the neck of the aneurysm, and terminating in the vertical segment of the cavernous ICA. At this point, the PressureWire was pushed out of the Echelon microcatheter and another pressure measurement was made. A second 5×18 mm Pipeline stent was then deployed, with the proximal end overlaying the proximal end of the first stent just before the ophthalmic artery takeoff, and terminating in the proximal vertical segment of the cavernous ICA. Again, the PressureWire was advanced and the intrasaccular pressure was measured. There were no immediate complications.
A middle-aged patient with bilateral giant ICA-ophthalmic aneurysms measuring 18 mm in largest diameter presented with decreased visual acuity in the left eye due to optic nerve compression. Given the mass effect on the optic nerve, the left ICA aneurysm was considered for treatment with a flow-diverting stent. Aspirin (325 mg daily) and clopidogrel (75 mg daily) were started 3 days prior to the procedure.
Under general anesthesia, a Shuttle guiding sheath was advanced into the left carotid bifurcation. A 5.2 Fr DAC 057 catheter was then advanced into the petrous segment of the left ICA over a Marksman 027 microcatheter and Synchro14 guidewire combination. The Marksman microcatheter was further advanced into the ipsilateral M1 segment. A 4×25 mm Pipeline stent was then advanced into the Marksman catheter but was not deployed out of the tip of the Marksman. A second microcatheter, Echelon 10, was inserted into the Shuttle guiding sheath and navigated into the aneurysm. Next, a PrimeWire (Volcano, San Diego, California, USA) pressure measurement wire was advanced into the aneurysm dome via the Echelon 10 microcatheter for subsequent intrasaccular pressure measurements. The Pipeline stent was slowly deployed under fluoroscopy. The distal end of the device was positioned within the supraclinoid ICA just short of the anterior choroidal artery and the proximal end was positioned within the horizontal cavernous segment. Intrasaccular pressure measurements were again obtained after Pipeline deployment. The pressure measurement wire and Echelon microcatheter were both pulled out from the Shuttle guiding sheath. A post-intervention angiogram showed small in-stent thrombus formation. This was successfully treated with local administration of glycoprotein IIb/IIIa inhibitor without clinical sequelae.
In both cases, intrasaccular pressure measurement with the use of the 0.014 inch pressure wire system was feasible. The pressure wires could be pushed out of the Echelon microcatheter placed in the aneurysms without friction or unexpected microcatheter motion.
Intrasaccular pressure before stent placement in case 1 was 109/55, parallel to the systemic arterial pressure of 109/55. The angiogram prior to stent placement showed clear opacification of the entire aneurysm (figure 1A). After deployment of a first stent, the intrasaccular pressure and systemic arterial pressure remained stable with values of 116/58 and 118/59, respectively. After the deployment of a second stent, the angiogram showed contrast stagnation with layering (the ‘eclipse sign’) in the aneurysm as a result of flow diversion effect (figure 1D). However, there was no significant pressure change even after placement of the second stent. The aneurysm pressure and radial pressure at this point measured 111/60 and 119/60, respectively (figure 2).
In case 2, the angiogram prior to stent placement opacified the entire aneurysm clearly (figure 3A). Intrasaccular pressure before stent placement was 135/78, similar to the systemic arterial pressure of 149/80. After stent deployment the angiogram showed almost no opacification of the aneurysm as a result of a strong flow diversion effect (figure 3C). However, essentially no change was observed in the intrasaccular pressure. The intrasaccular and systemic pressures after stent deployment measured 107/66 and 115/65, respectively. There was no significant change in intrasaccular pressure 5 min after complete stent deployment. The pressure in the aneurysm and the radial pressure were 100/63 and 110/60, respectively (figure 4).
In both cases, despite successful flow-diverting stent deployment and angiographic flow diversion effects with excellent wall opposition across the aneurysm necks, there was no significant difference between the intrasaccular and systemic pressures.
The introduction of intracranial stents has changed the way wide-necked and fusiform aneurysms are treated.6 ,9 ,14 The metallic scaffolding of neck-bridging stents, combined with aneurysmal coil embolization, enables reconstruction of the diseased parent artery along with the aneurysm. Theoretically, flow-diverting stents serve as stand-alone devices that do not require any additional coil embolization of the aneurysm.1 Although the immediate post-treatment angiogram may show residual aneurysm filling, the contrast transit time within the aneurysm increases, producing a layering of contrast material referred to as the ‘eclipse sign’.3 Over time, stagnant blood flow within the aneurysm leads to thrombosis.
Recently, complications such as delayed aneurysm rupture after placement of a flow-diverting stent have been highlighted in spite of high aneurysm obliteration rates.3 ,7 Siddiqui et al15 reported cases of delayed aneurysm rupture and recommended the use of coils in addition to flow diversion. Delayed aneurysm rupture did not become a major issue for stent-assisted coil embolization, presumably due to aneurysm protection by the coil mass.
Schneiders et al measured the intrasaccular pressure before, during, and after placement of a flow-diverting silk stent by using a dual-sensor guidewire in a patient with a partially thrombosed giant M1 aneurysm. They found that the peak systolic pressure and pulse pressure were unaffected by flow diversion and that the aneurysm wall was not protected from pressure-induced stress.10 Our findings provide additional evidence in support of this concept.
A recent computational hemodynamic analysis conducted by our group showed that the flow diversion effect is limited to flow velocity reduction.11 In fact, the simulation suggested that flow diversion does not reduce intrasaccular pressure. In stent-assisted coil embolization, the primary material that protects a treated aneurysm is the coil mass. Without it, the aneurysm is exposed to nearly normal arterial pressure during the slow process of progressive thrombosis.11 While the mechanism of delayed aneurysm rupture after flow diversion is not well understood, the findings described here provide additional evidence that aneurysm treatment with the use of flow diversion alone fails to provide immediate aneurysm protection; our cases demonstrated no significant difference between intrasaccular and systemic pressure before and after Pipeline deployment. Even with multiple overlapping flow-diverting stents as employed in case 1, the intrasaccular pressure was unchanged.
Although we are only presenting the results of two cases, our findings provide additional evidence in support of previous reports. The persistent dilatory force of systemic-equivalent pressures inside an aneurysm may play a role in delayed rupture after treatment with a flow-diverting stent. Therefore, until future generation flow-diverting stents are available that can elicit faster thrombosis and subsequent healing, the concomitant use of aneurysm coils should be considered when immediate aneurysm protection or enhancement of the thrombotic process is necessary.16
In both of our large cavernous and giant ophthalmic aneurysms, intrasaccular flow measurement with the use of the 0.014 inch coronary pressure wires system was feasible and provided us with a clear pressure waveform reading. In our practice, adjunct use of coil embolization is often considered for large intradural and giant aneurysms if the anatomy permits. The benefit of the use of the 0.014 inch coronary pressure wire system is that it can be delivered through the microcatheter for the purpose of adjunctive coiling. Real-time information regarding intrasaccular pressure may be useful in deciding whether additional stents are needed to accelerate thrombosis. One of the limitations, however, is that the 30 mm length tip wire on both manufacturers’ pressure wire systems may be unfavorable for intrasaccular pressure measurement in relatively small aneurysms. A neuro-specific pressure wire system is required for this methodology to be used on a routine basis.
Despite successful flow-diverting stent placement with excellent wall opposition across the aneurysms described, there was no significant difference between the intrasaccular and systemic pressures during or after placement.
Contributors ST, JGJ, FMB, FV and GRD all contributed to the study and the preparation of the manuscript.
Competing interests None.
Ethics approval Ethics approval was obtained from the Institutional Review Board.
Provenance and peer review Not commissioned; externally peer reviewed.
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