Larger Perfusion Mismatch Volume is Associated with Longer Hospital Length of Stay in Medium Vessel Occlusion Stroke

Academic Background

Stroke is the second leading cause of death globally, imposing a significant burden on both patients and healthcare systems. Prolonged hospital length of stay (LOS) is closely associated with adverse clinical outcomes following a stroke, including hospital-acquired infections, gastrointestinal bleeding, poorer neurological outcomes at discharge, post-stroke depression, and increased risk of disability. Additionally, extended LOS escalates the costs of stroke care and rehabilitation, placing pressure on healthcare resources and hospital capacity.

While factors influencing LOS, such as stroke severity, stroke volume, and types of endovascular therapies, have been extensively studied in large vessel occlusion (LVO), their roles in medium vessel occlusion (MeVO) remain underexplored. MeVO accounts for 40% of acute ischemic stroke (AIS) cases, and its pathophysiology differs from LVO, potentially leading to different predictive values.

This study aims to investigate the predictors of LOS in AIS-MeVO patients, particularly the relationship between perfusion mismatch volume and LOS. Perfusion mismatch volume, calculated using CT perfusion imaging (CTP), is defined as the region with time to maximum (Tmax > 6 seconds) minus the region with relative cerebral blood flow (rCBF < 30%). The clinical significance of this metric in MeVO has not been thoroughly studied.

Source of the Paper

This paper was co-authored by scholars from several renowned institutions, including Johns Hopkins Medical Center, Massachusetts General Hospital, and Stanford Medical Center. The primary authors include Janet Mei, Hamza Adel Salim, and Vivek Yedavalli. The paper was published in 2025 in the Journal of Neuroimaging, titled Larger Perfusion Mismatch Volume is Associated with Longer Hospital Length of Stay in Medium Vessel Occlusion Stroke.

Research Process and Results

Study Design

This study is a retrospective analysis based on prospectively maintained stroke databases from two comprehensive stroke centers. It included consecutive patients who met the inclusion criteria between July 29, 2019, and January 29, 2023. The inclusion criteria were: 1) mechanical thrombectomy (MT) triage within 24 hours of symptom onset or last known well; 2) pretreatment multimodal CT imaging, including non-contrast CT, CT angiography, and CT perfusion imaging; and 3) AIS due to anterior circulation MeVO confirmed by CTA/CTP.

Data Collection

Baseline and clinical data were collected from electronic medical records and stroke center databases, including demographic information, admission National Institutes of Health Stroke Scale (NIHSS) scores, comorbidities (e.g., hypertension, hyperlipidemia, diabetes), and Alberta Stroke Program Early CT Score (ASPECTS).

CT Perfusion Imaging Analysis

CTP images were acquired using a Siemens Somatom Force scanner and automatically processed using FDA-approved RAPID software (version 5.9) to generate quantitative perfusion maps. All CTP images were evaluated by board-certified neuroradiologists to ensure diagnostic quality.

Statistical Analysis

Data were analyzed using IBM SPSS Statistics (version 22.0). Continuous variables were reported as medians and interquartile ranges (IQR), while categorical variables were reported as frequencies. Data comparisons were performed using Wilcoxon rank-sum tests or chi-square tests, as appropriate. Multiple regression analysis was used to explore the relationship between baseline parameters and LOS.

Key Findings

The study included 133 patients, with a median age of 71 years, 59.4% of whom were female. Perfusion mismatch volume was significantly positively correlated with LOS (r = 0.264, p = 0.004). After adjusting for age, sex, hypertension, diabetes, prior stroke or transient ischemic attack (TIA), admission NIHSS score, ASPECTS score, TAN score, intravenous thrombolysis, mechanical thrombectomy, and hemorrhagic transformation, larger perfusion mismatch volume remained independently associated with longer LOS (β = 0.209, 95% CI: 0.006–0.412, p = 0.045).

Other significant determinants of LOS included admission NIHSS score (β = 0.250, 95% CI: 0.060–0.440, p = 0.010) and mechanical thrombectomy (β = 0.208, 95% CI: 0.006–0.410, p = 0.044). Among patients who underwent mechanical thrombectomy, perfusion mismatch volume remained significantly associated with LOS (β = 0.248, 95% CI: 0.019–0.471, p = 0.033), while admission NIHSS score lost significance (β = 0.208, 95% CI: 0.019–0.433, p = 0.071).

Conclusions and Significance

This study demonstrates that in anterior circulation AIS-MeVO patients, particularly those undergoing mechanical thrombectomy, perfusion mismatch volume is an independent predictor of LOS. This finding provides critical insights for clinical assessments and decision-making, especially in the selection of mechanical thrombectomy indications and treatment strategies.

Research Highlights

1. Clinical Significance of Perfusion Mismatch Volume: This study is the first to systematically explore the predictive value of CTP perfusion mismatch volume in MeVO, addressing a gap in this field.
2. Relationship Between Mechanical Thrombectomy and LOS: The study found that mechanical thrombectomy is associated with longer LOS, likely due to postoperative ICU observation and management of hemorrhagic transformation.
3. Predictive Role of NIHSS Score: The correlation between admission NIHSS score and LOS became non-significant after adjusting for perfusion mismatch volume, suggesting that perfusion mismatch volume may play a more fundamental role in predicting LOS.

Study Limitations

1. Retrospective Design: The study may be subject to selection bias.
2. Sample Limitations: The study only included anterior circulation MeVO patients, limiting the generalizability of the results to occlusions in other arterial territories.
3. Availability of CTP: The accessibility of CTP in smaller and community hospitals may affect the applicability of the findings.

Future Directions

Future large-scale prospective studies are needed to validate these results and further explore the optimization of mechanical thrombectomy indications and post-stroke care strategies for MeVO patients.