Ruptures of cerebral aneurysms lead to subarachnoid hemorrhage (SAH) and are associated with substantial mortality and morbidity. Previous research has indicated that the rupture rates of aneurysms vary with size, location, and morphological characteristics, as well as patients’ personal and family medical history. “These variables have historically been used to help guide the clinical management of cerebral aneurysms,” explains Robert M. Friedlander, MD. “For clinicians who treat these patients, microsurgical clipping and endovascular coiling have emerged as the two primary interventions for cerebral aneurysms that require intervention.”

In 2002, outcomes for patients with ruptured cerebral aneurysms were reported in the International Subarachnoid Aneurysm Trial (ISAT). The trial compared mortality and clinical outcomes of patients with aneurysmal SAH who were treated with either surgical clipping or endovascular coiling. The study found that patients who underwent coiling had lower mortality and better outcomes at 1 year than those who had open surgery. As a result of the ISAT findings, it was assumed that more clinicians in the United States would begin treating ruptured aneurysms with endovascular approaches.

“Sufficient time has now passed since the publication of the ISAT results to allow for a formal examination of treatment patterns for cerebral aneurysms—both ruptured and unruptured—within the U.S.,” says Dr. Friedlander. “It’s important to analyze trends on the use of endovascular coiling because patterns may be different in demographic subgroups and in hospitals located in different geographic areas.”

Recent Trends in Cerebral Aneurysm Treatment

In the May 2012 Journal of Neurointerventional Surgery, Dr. Friedlander, Ning Lin, MD, and colleagues published an analysis describing patterns of use and in-hospital mortality associated with surgical and endovascular treatments of cerebral aneurysms over the course of a decade. The investigation reviewed data from nearly 35,000 hospital discharges with a diagnosis of ruptured or unruptured cerebral aneurysm from 1998 to 2007 from the Nationwide Inpatient Sample. The final analysis involved 20,134 discharges with a ruptured aneurysm and 14,765 discharges with an unruptured aneurysm.

According to findings, the number of patients discharged with a ruptured aneurysm was stable, while the number discharged with an unruptured aneurysm increased significantly over the 10-year period. The use of coiling increased at least two-fold for both groups of patients, with the majority of unruptured aneurysms treated with an endovascular approach by 2007 (Figure 1). Overall, Caucasians were more likely than non-Caucasians to undergo coiling versus clipping for a ruptured aneurysm. Men with unruptured aneurysms were more likely than women to undergo coiling. However, the significance of these demographic factors lessened over time. “By 2007, the differences in treatment selection by gender and racial subgroups decreased or were statistically non-significant,” adds Dr. Lin.

Data also revealed that 90.7% of ruptured aneurysms and 79.4% of unruptured aneurysms were treated with clipping before 2002, but these rates decreased to 57.1% and 38.3%, respectively, after 2002 (Figure 2). In addition, the analysis showed that use of coiling spread from primarily large, teaching hospitals to smaller, non-teaching hospitals. “These results suggest that dissemination of endovascular procedures appears to be widespread across patient and hospital subgroups,” Dr. Lin says. Older age, higher income level, public healthcare coverage, teaching hospital admission, and non-emergency presentation were associated with a higher likelihood of coiling for both ruptured and unruptured aneurysms.

Low Mortality Rates for Unruptured Aneurysm

Endovascular coiling was associated with lower in-hospital mortality for patients with unruptured aneurysms, but the mortality for either treatment was still low, says Dr. Friedlander. “For the SAH group, coiling was associated with higher in-hospital mortality, a difference that was consistent over the study period.” He adds that this finding could be explained by the fact that patients with SAH who underwent coiling were older and had more comorbidities than those who were clipped. Notably, mortality was lower for patients at smaller hospitals than for those at larger hospitals. This may be the result of smaller hospitals transferring more complex patients to larger medical centers.

Looking Ahead

Dr. Friedlander says it is important to consider the potential impact that greater use of these procedures may have on hospitals and clinicians. “It’s expected that hospitals throughout the U.S. will deliver more uniform care for patients with ruptured cerebral aneurysms and continue to promote and adopt the use of endovascular coiling. As more technologic advances emerge, the availability of endovascular procedures will likely increase throughout the country. The shift demonstrated in our study could influence treatment selection and allocation of hospital resources in the future.”

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