Overriding role of parent over daughter vessel dimension in size ratio detection performance of bifurcation aneurysms ruptured status

Abstract

Objective: Aneurysm-to-vessel size ratio (SR) predicts rupture status based on the premise that large aneurysms on small vessels are more likely to rupture compared to small aneurysms on larger vessels. While simpler for sidewall-type (function of proximal vessel [PV] only), SR methodology for bifurcation aneurysms requires the overhead of daughter vessels measurement. This study sets to evaluate SR performance on bifurcation aneurysms, and determine the added value of including daughters’ measurements.

Methods: Catheter 3D-rotational angiograms of 154 bifurcation aneurysms (54 ruptured) were available. Aneurysms were evaluated for height (H) and maximal size (Dmax). Vessel size was evaluated as PV, daughter vessels average (DV), and parent and daughter vessels average (PDV). First, SR was evaluated as SR1_PDV  =  H/PDV and SR2_PDV  =  Dmax/PDV. Second, SR function of the parent vessel only was evaluated as SR1_PV  =  H/PV and SR2_PV  =  Dmax/PV. Statistical significance was assumed for P < 0·05. Area under the curve (AUC) was evaluated.

Results: Unexpectedly, parent vessel only definitions, SR1_PV (P < 0·001, AUC  =  0·69) and SR2_PV (P  =  0·002, AUC  =  0·64), performed marginally better as rupture status discriminators compared to the corresponding parent and daughter vessels definitions, SR1_PDV (P  =  0·001, AUC  =  0·67) and SR2_PDV (P  =  0·01, AUC  =  0·63), respectively. Parameters including daughter vessel measurements (DV, PDV, DV/PV) were not significant.

Conclusion: Not only is the inclusion of daughter measurements not statistically justified, it may be detrimental to SR performance. Parent-only SR definitions simplify the aneurysmal morphological evaluation at no performance loss. It is reasonable to employ a unified approach regardless of sidewall/bifurcation labeling, by defining SR as aneurysm size to parent vessel ratio and omitting the measurements of the daughter branches.

Keywords:

• Intracranial aneurysm
• Morphology
• Rupture risk
• Size ratio
• Bifurcation aneurysm