Treatment of Cerebral Aneurysms with Hydrogel-Coated Platinum Coils (HydroCoil): Early Single-Center Experience

Patient Selection

Between November 2002 and February 2005, 277 patients with cerebral aneurysms were treated with endovascular coil embolization at the Beth Israel Hyman-Newman Institute for Neurology and Neurosurgery in New York. During this period, the first consecutive 100 patients in whom HydroCoils were detached in 104 intradural saccular cerebral aneurysms were identified. Patients with HydroCoil and treated extradural cavernous aneurysms, fusiform aneurysms, and distal aneurysms treated primarily with parent artery sacrifice were excluded. Most patients were referred from neurologic and neurosurgical centers for aneurysms or were believed to have a higher risk for surgical treatment, after failed surgical attempt, after prior evaluation by both endovascular surgery and vascular microsurgery teams recommended coiling, or because of patient refusal of surgery.

There were no strict inclusion criteria. On the basis of operator preference, the coiling procedure was augmented with HydroCoil filling coils in selected cases. In general, the tendency of the operators was to treat larger aneurysms with HydroCoils, with the rationale of decreasing the total number of coils used. Review of records could not accurately nor reliably identify patients in whom HydroCoil placement was attempted but not deployed; therefore, the exact number of patients with failed HydroCoil deployments was not recorded. The anatomic and clinical outcomes of this cohort of 100 patients with 104 HydroCoil-treated cerebral saccular aneurysms were retrospectively studied. The patient clinical and aneurysm data are summarized in Table 1. Aneurysms were divided into 4 categories¹¹: S/S, S/W, L, and G aneurysms.

Endovascular Treatment

The technique for endovascular coil treatment has been previously described.^11,15 Eighty-seven patients were treated on a biplane angiographic system (Siemens, Erlangen, Germany) with 3D-rotational digital subtraction angiography; 13 patients were treated on a single-plane angiographic system without 3D-rotational angiography (Philips Medical Systems, Best, the Netherlands). In general, intravenous heparin infusion was continued for 24–48 hours after the procedure, with maintenance pulse transit time goal of 50 seconds. HydroCoil size and length selection were based on operator preference, and preparation was performed as specified by the manufacturer. HydroCoils were used primarily as filling coils in this series. GDC bare platinum coils were used almost exclusively initially to frame the aneurysm. Balloon-remodeling technique was used in 21 (20%) procedures.¹³ Stent-assisted coiling was performed in 8 (8%) procedures.^16,17

Complications

Procedure-related morbidity was recorded as a permanent new neurologic deficit after embolization. Procedure-related death was recorded as death directly related to procedure (eg, intraoperative rupture or procedure-related morbidity leading to death). Delayed rehemorrhage of treated aneurysm was recorded. Clinical follow-up data were collected by review of hospital charts, evaluation at last clinic visitation or follow-up angiography, or by telephone interview. Patients’ neurologic outcome at last evaluation was recorded as unchanged, improved, or worse, compared with pretreatment status.¹¹

Angiographic Evaluation

Angiographic results were recorded immediately and on last follow-up. Multiple projections with selective contrast injections were reviewed for angiographic complete occlusion, defined as no contrast within the aneurysm dome, body, and neck. We used the classification of angiographic results as defined by Roy et al⁷: class 1, complete occlusion; class 2, persistence of any portion of the original defect of the arterial wall as seen on any single projection but without opacification of the aneurysm sac; class 3, aneurysm sac opacification (Figs 2 and 3). For each patient, the pre- and postembolization and follow-up (if available) angiograms were independently reviewed by 2 attending interventionalists for initial and follow-up aneurysm occlusion grades. The interventionalists were blinded as to the type and percentage length of the HydroCoil used for each patient. Written reports were not reviewed for aneurysm occlusion grade determination. For discordant grades, the worse of the 2 occlusion grades was recorded.

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Fig 2.

Diagrams of angiographic occlusion classes, adapted from Roy et al⁷: class 1, complete; class 2, residual neck; and class 3, aneurysm filling.

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Fig 3.

Example of angiographic occlusion classes 1, 2, and 3: class 1, complete occlusion; class 2, persistence of any portion of the original defect of the arterial wall as seen on any single projection but without opacification of the aneurysm sac; and class 3, aneurysm sac opacification.

Angiographic Follow-Up Strategy and Evaluation

For patients with all treated aneurysms, follow-up skull x-rays were requested at 3 months. If skull x-rays showed evidence of coil compaction, angiography was recommended immediately. Compared with the postembolization unsubtracted coil mass, visual recognition of a change in coil mass configuration on skull x-rays, either flattening, rotation, loosening, reorientation, and so forth, indicated coil compaction.¹⁸ Otherwise, for patients with ruptured aneurysms, a 6-month follow-up angiogram was recommended. For patients with unruptured aneurysms, a 1-year follow-up angiogram was recommended. Angiograms were also recommended at 3-year and at 5-year follow-up.

To better compare recanalization results with GDC bare platinum coils, we used the same definition of recanalization as that used in the 11-year UCLA experience¹¹: Recanalization was defined as more than 10% increase in contrast filling of the aneurysm; less than 10% increased filling was defined as unchanged. Also for this follow-up group, class (1, 2, or 3) angiographic results were compared immediately after embolization and at last follow-up.

Patient Population

Table 1 summarizes patient and aneurysm characteristics. Sixty percent of patients were women. The mean age was 54 years. Fifty-four percent of the treated aneurysms were unruptured. Three fourths of the treated aneurysms were located in the anterior circulation. S/S aneurysms composed 40%; S/W, 26%; L, 32%; and G, 3%.

Clinical Outcome

Table 2 summarizes procedural complications. Procedure-related morbidity was 5.8% and procedure-related death was 0%. One aneurysm perforation (<1%) occurred (first bare platinum coil framing coil; HydroCoil used to seal re-ruptured site) and led to permanent neurologic deficit in a surviving patient.

Thromboembolism occurred in 9 procedures, leading to 3 permanent neurologic deficits. In a 65-year-old man, a ruptured anterior communicating artery aneurysm was coiled with 20% HydroCoil by length; after the coiling procedure, thromboembolism of the left frontal and parietal cortical branches occurred and was treated with intra-arterial thrombolysis, with improved perfusion to the parietal middle cerebral artery (MCA) branches but not in the left prefrontal MCA territory, leading to a permanent language deficit. In a 22-year-old woman with a ruptured basilar trunk aneurysm, intraoperative aneurysm rupture occurred during placement of the first bare platinum coil. Heparin was reversed. A single HydroCoil was used to seal the aneurysm rupture site, but 1 of the coil loops protruded into the parent vessel. An emergent ventriculostomy catheter was then placed in the angiography suite. After ventriculostomy placement, a control angiogram showed thrombus about the coil loop, which was treated with 2 mg of intra-arterial abciximab (ReoPro). Follow-up MR imaging with diffusion imaging showed no infarct; however, the patient did not recover from the rehemorrhage and was eventually discharged to a skilled nursing facility, not cognitively able to participate in her care.

In the third patient, a 67-year-old woman with a ruptured large right posterior communicating artery aneurysm, 22% HydroCoil by length was used; the last coil, a bare platinum coil, stretched and was eventually removed without movement of the coil mass. On the postembolization control angiogram, a distal right inferior parietal branch occlusion was present. The patient was treated with intravenous heparin for 48 hours but had a mild sensory deficit. Parent artery occlusion occurred in 1 procedure, but this did not lead to a new neurologic deficit. Follow-up angiography performed 3 days later showed complete recanalization of the occluded artery.

Clinical follow-up was obtained in 73 patients from <1 month to 24 months; average, 5.3 months. Of these 73 patients, 68 (93%) had improved or unchanged neurologic status at last follow-up. Thirty-two patients had improved neurologic status, 36 patients had unchanged neurologic status, and 5 patients had worse neurologic status. Three patients experienced rehemorrhage after coiling (Table 3). Of the patients who rebled, 2 died. Three patients who did not have aneurysm rupture developed symptomatic hydrocephalus requiring ventriculoperitoneal shunt surgery, with recovery in all 3 (Table 4).

Immediate Angiographic Outcome

Immediate postprocedure angiography demonstrated overall class 1 complete aneurysm occlusion in 35 (34%), class 2 neck remnant in 36 (35%), and class 3 incomplete occlusion in 33 (32%). Table 5 summarizes class 1, 2, and 3 angiographic results for S/S, S/W, L, and G aneurysms. In general, more complete closure was seen in S/S aneurysms. On average, HydroCoils composed 45.5% by total length of detached coils within treated aneurysms.

Follow-Up Angiographic Outcome

Follow-up angiography was performed in 51 patients with 53 HydroCoil-treated aneurysms. Table 6 lists the clinical and aneurysm characteristics of this group of patients. Angiographic follow-up was obtained from 0 to 31 months; average, 10.3 months. Forty-two of the 51 patients (82%) had >6 month follow-up. In this angiographically followed group, 1 aneurysm was G; 22 (46%) were L; 7 were (13%) S/W; and 23 were (43%) S/S. On the basis of the initial size distribution of treated aneurysms, angiographic follow-up was obtained in 55% (23/42) of S/S aneurysms, 26% (7/27) of S/W aneurysms, 69% (22/32) of L aneurysms, and 33% (1/3) of G aneurysms. In this angiographically followed group, compared with all patients, the percentage by length of HydroCoils was similar, 51% versus 46%.

Comparison of occlusion class immediately after treatment and at last follow-up showed that 87% of the 53 aneurysms had stable or improved class and 13% had worse class (Table 7). Of the 43 class 2 and class 3 aneurysms, on follow-up, 15 (35%) aneurysms were class 1, completely occluded (Fig 4). Of note, 12/20 (60%) class 3 aneurysms converted to class 1 on last follow-up.

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Fig 4.

Example of class 3 conversion to class 1. Left accessory MCA aneurysm shows aneurysm filling (class 3) in immediate postembolization angiogram. Ten-month follow-up angiogram shows class 1 complete occlusion.

Aneurysm Recanalization

In these 53 angiographically followed aneurysms, overall recanalization rate was 21% (Table 8). No recanalization occurred in 23 S/S aneurysms. Four recanalizations occurred in 7 S/W aneurysms. Recanalization occurred in 6/22 (27%) L aneurysms. One G aneurysm recanalized.