Trends in the in-hospital stroke rate following carotid endarterectomy in California and Maryland.

OBJECTIVE: We examined the outcome of carotid endarterectomy (CEA) in the state of Maryland during the last decade to identify any trends in the incidence of in-hospital stroke and mortality and compared these results with the outcome of the operation throughout the state of California as a control population.
METHOD: We performed a retrospective analysis of 10 years (1994 to 2003) of the Maryland and 5 years (1999 to 2003) of the California hospital discharge databases. The following patients were included in the analysis: (1) International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) procedure code 38.12 (endarterectomy of the vessels of the head and neck other than intracranial vessels) in the primary coding position but not in any secondary position, or (2) the diagnosis code 433.00 to 433.91 (occlusion/stenosis, precerebral artery), or (3) the diagnosis-related group (DRG) 5 (extracranial vascular procedure). Symptomatic patients were identified by history of previous stroke (ICD-9 codes 342 or 438), transient ischemic attack (435 or 781.4), or amaurosis fugax (362.34 or 368.12). In-hospital strokes were identified by ICD-9 codes 997.0, 997.00, 997.01, and 997.09. Low-, moderate-, and high-volume surgeons were defined as performing <15, 15 to 74 and >or=75 CEAs annually. Hospital volumes were similarly classified as low for those performing <or=20 CEAs, moderate for 21 to 100, and high for >100 annually.
RESULTS: In the Maryland data, 23,237 CEA cases were identified with 169 in-hospital strokes over 10 years (0.73%), whereas the 51,331 California CEAs had 232 in-hospital strokes over 5 years (0.45%). The stroke rate in Maryland was 2.12% in 1994, 1.47% in 1995, and 0.29% to 0.65% from 1996 to 2003. The decrease in strokes was more pronounced among symptomatic patients, where the rate was 3.82% in 1994, 4.44% in 1995, and 0.90% to 2.29% from 1996 to 2003. A similar decrease was identified in the asymptomatic patient population but was less pronounced: 1.64% in 1994, 0.81% in 1995, and 0.15% to 0.44% from 1996 to 2003. The low recent stroke rates were confirmed by the California data (0.44% to 0.48% from 1999 to 2003). Changes in the death rate for CEA during this time frame have not been as pronounced, from 0.33% to 0.58% for Maryland and 0.78% to 0.91% for California.
CONCLUSIONS: A dramatic decrease in the in-hospital stroke rates in Maryland occurred around 1995. The stroke rates in Maryland in the past 5 years are similar to those in California during the same period. An analysis of data from the two states shows that the in-hospital stroke rate now for carotid endarterectomy is approximately 0.54%.