The interrelated effects of 2D angiographic morphological variables and aneurysm rupture

Objective:

To investigate the correlations between morphological parameters and rupture status in cerebral aneurysm patients.

Methods:

We conducted a retrospective study of 34 patient records from March 2010 to December 2012. The morphological parameters of 34 ruptured and 42 unruptured cerebral aneurysms in 34 patients (males: female, 15:19; mean age 55.79±10.64 years) leading to subarachnoid hemorrhage were examined using 3D (dimension) digital subtraction angiography (DSA) models, to identify the correlation between 2D morphological parameters and risk factors of rupture status with univariate and multivariate analysis.

Results:

The 2D morphological parameters in ruptured aneurysms were significantly different from those observed in unruptured aneurysms (p<0.05), though only size and height-width ratios independently predicted rupture status. Dmax, Hmax, bottleneck factor, and size ratio significantly correlated with height-width ratio in ruptured but not unruptured aneurysms.

Conclusions:

A specific set of morphological characteristics, most notably size and height-width ratios, may help to understand rupture risk by indicating arterial stretch character in cerebral aneurysms patients.Cerebral and intracranial aneurysms occur when weak blood vessel walls give way in the brain, producing a bulging or ballooning effect that may or may not be symptomatic or lead to rupture.1,2 The pathophysiological mechanisms associated with rupture occurrence remain poorly understood, and rupture risk is most commonly assessed using aneurysm size, location, and shape.1 With CT technique application on imaging of intracranial aneurysms, more detailed measurements on aneurysm morphologies have become available to better assess rupture risk in diverse cerebral aneurysms. In one of the largest international studies of cerebral aneurysms to date, the International Study of Unruptured Intracranial Aneurysms (ISUIA) reported in 1998-1999 that 0.1-0.2% of intracranial aneurysm patients experienced rupture, with the risk of morbidity and mortality related to surgery greatly exceeding the 7.5-year risk of rupture in patients with relatively small diameters (<10 mm).3,4 Thus, preventative surgical treatment may not be appropriate for many patients, despite a mortality rate of 40-50%, and a morbidity rate of 10-20%5-7 in patients that develop rupture leading to aneurysmal subarachnoid hemorrhage. Over the last decade, numerous strategies have been proposed for assessing rupture risk;7-9 however, these broad guidelines may not consistently predict outcomes and rupture risk in many patient subpopulations. Thus, detailed stratification of intracranial aneurysm patients with aneurysm morphology and patient status such as gender, age, and the clinical condition (namely, hypertension, body mass index, smoking habits) help to understand the prevention of potentially life-threatening aneurysmal subarachnoid hemorrhage occurrence.The geometrical morphological characteristics of aneurysm rupture are mostly location, shape, and size.1 More recently, aspect ratios greater than 1.6 have been shown to be significantly associated with rupture, with 80% of patients that experienced rupture exhibiting greater aspect ratios.10 Similarly, increased bottleneck factor and height-width ratio were consistently associated with rupture.11 The increasingly wide availability of 3 dimensional (3D) angiography imaging has also led to the employment of advanced computations and hemodynamics models for rupture assessment, that carefully consider individual physiological and morphological parameters related to aneurysm rupture.12,13 In these models, trends toward simple stable patterns, large impingement regions, and jet sizes have been associated with unruptured aneurysms, while disturbed flow patterns, small impingement regions, and narrow jets were indicative of rupture.Due to the diversity in morphological and clinical characteristics and methodologies in these reports; however, accurate meta-analysis is all but impossible.14 Though comprehensive reviews have been conducted on strategies for assessing rupture in aneurysm patients,14 few clinical studies have examined aneurysm morphology and clinical status in a single patient cohort. Thus, most reports on aneurysm rupture risk fail to account for confounding variables between diverse patient cohorts, potentially overlooking the impact of key clinical parameters. Therefore, improved cerebral aneurysm patient stratification requires comprehensive assessment of key clinical and morphological characteristics in a single group of patients, which may yield valuable information on the interrelationships between these parameters of rupture risk. The current study investigated the relationship between morphological and clinical parameters and rupture status in cerebral aneurysm patients using 3D models produced by digital subtraction angiography (DSA). Notably, clinical performance was minimized in order to most effectively assess morphological parameters.