Real-world two-year outcomes and territorial specificity after posterior and anterior circulation ischemic stroke

Posterior circulation ischemic stroke (PCIS) accounts for approximately one-quarter of ischemic strokes, but long-term survival and territory-specific recurrence patterns compared with anterior circulation ischemic stroke (ACIS) remain incompletely defined.

We analyzed Oracle Health Real-World Data from January 2015 through February 2025, including 118,727 patients hospitalized with acute ischemic stroke across 149 United States (U.S.) health systems. PCIS and ACIS were identified using validated International Classification of Diseases, Tenth Revision, Clinical Modification codes. Outcomes included 30-day recurrent ischemic stroke or death, two-year recurrent ischemic stroke by territory, intracerebral hemorrhage, and mortality. Binary outcomes used logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs). P values for binary comparisons were Hochberg-adjusted for multiple comparisons. Recurrent-stroke time-to-event analyses used adjusted cause-specific Cox models to estimate hazard ratios (HRs), with patients censored at death before recurrence.

Of 118,727 patients, 30,030 (25.3%) and 88,697 (74.7%) had PCIS and ACIS, respectively. Within 30 days, mortality was lower after PCIS (1.88% vs 2.66%; OR 0.70, 95% CI 0.64-0.77; P < 0.001), whereas recurrent ischemic stroke was similar (0.23% vs 0.24%; OR 0.95, 95% CI 0.72-1.24; P = 0.750). Over 2 years, PCIS had lower intracerebral hemorrhage (1.99% vs 2.82%; OR 0.70, 95% CI 0.64-0.77; P < 0.001) and mortality (11.23% vs 14.35%; OR 0.75, 95% CI 0.72-0.79; P < 0.001). Recurrence was territory-specific: recurrent PCIS was more frequent after index PCIS (12.90% vs 0.54%; OR 27.29, 95% CI 24.79-30.03), whereas recurrent ACIS was less frequent after index PCIS (1.67% vs 15.32%; OR 0.09, 95% CI 0.09-0.10) (both P < 0.001). PCIS had a modestly higher unadjusted recurrence hazard (HR, 1.04; 95% CI, 1.02-1.07; P < 0.001), no longer present after adjustment (adjusted HR, 1.00; 95% CI, 0.98-1.02; P = 0.933).

In a large contemporary U.S. real-world cohort, PCIS was associated withlower 30-day mortality, similar 30-day recurrent ischemic stroke, lower two-year mortality, and lower risk of intracerebral hemorrhage than ACIS. Recurrent ischemic stroke showed marked circulation concordance, and two-year recurrent stroke risk after PCIS remained clinically important. These findings support circulation-aware risk stratification, focused follow-up, and targeted secondary prevention after ischemic stroke.