Early Ceasing of Intra-aneurysmal Contrast Opacification During Coil Embolization in Ruptured Aneurysms Compared With Unruptured Aneurysms

BACKGROUND: The difference between coil-embolized ruptured and unruptured aneurysms with respect to intra-aneurysmal thrombus formation remains to be determined. OBJECTIVE: We examined whether there was a difference between ruptured and unruptured coil-embolized aneurysms in the rate and timing of thrombus formation in the aneurysmal sac and discuss the effect of thrombus on the treatment outcome. METHODS: We evaluated 209 aneurysms with an aneurysmal dome smaller than 10 mm and a neck size less than 4 mm. Of these, 91 (43.5%) were ruptured. We assessed intra-aneurysmal thrombus formation by the coil-packing ratio (CPR): the percentage of coil volume occupying the aneurysmal sac. The initial CPR was defined as the CPR at which contrast influx into the sac ceased and the final CPR as that at the end of the procedure. Delta CPR was calculated as the difference between initial and final CPRs. Embolized aneurysms were evaluated on follow-up angiograms. RESULTS: The initial CPR was significantly lower in ruptured aneurysms (P < .01), and there was not a significant difference in the final CPR between ruptured and unruptured aneurysms (P = .05). Delta CPR was significantly higher in ruptured aneurysms (P < .01). The rate of aneurysmal recanalization was significantly higher in ruptured aneurysms (P < .05). The incidence of recanalization was high in ruptured aneurysms with low initial CPR and Delta CPR values. CONCLUSION: In ruptured aneurysms, intra-aneurysmal thrombus formation tends to occur in the earlier stages of coil embolization. In some cases, thrombus formation may inhibit dense coil packing and result in recanalization.