Systems of care for acute ischemic stroke

Prehospital
All prehospital stroke scales can have cutoffs established with high positive or negative predictive value, but that makes them so insensitive or nonspecific that they become useless. When used appropriately, they will still miss as much as 20% of patients with an LVO. While this is beneficial in getting the other 80% of patients triaged appropriately to comprehensive stroke centers, we still cannot identify LVO more accurately with clinical scores. Thus, many continue to advocate for vascular imaging in all patients presenting with acute ischemic stroke within 6 hours of onset.



3-Item Stroke Scale (3ISS) (2005)
A score of ≥4 is 100% predictive of LVO, but if negative only has negative predictive value of 0.89, so a false negative rate of 11%.



Los Angeles Motor Score (LAMS) score (2008)
A score of ≥4 had a positive predictive value of 0.92 and a negative predictive value of 0.74, so a false negative rate of 26%. In one randomized trial the use of this scale led to an accurate triage decision in 70% of patients.



Rapid Arterial oCclusion Evaluation (RACE) score (2014)
A score of ≥4 had a PPV of 0.35 but a NPV of 0.95, so a false negative rate of only 5%. A score of ≥5 had a PPV of 0.42 but a NPV of 0.94. Although this score had a low false negative rate compared with others, it is considerably more cumbersome.



Cincinnati Prehospital Stroke Severity Scale (CPSSS) (2015)
A cutoff of CPSSS ≥2 had a PPV of 0.79 but a NPV of 0.47, so a high false negative rate.



Prehospital Acute Stroke Severity (PASS) scale (2016)
A score of ≥2 is associated with LVO, but this only has a negative predictive value of 0.81, so a false negative rate of 19%.



Field Assessment Stroke Triage for Emergency Destination (FAST-ED) scale (2016)
A score of ≥3 has PPV 0.62 and NPV 0.84, and score of ≥4 has a PPV 0.72 and NPV 0.82, so a false negative rate of 16-18%.



Madrid-Direct Referral to Endovascular Center (M-DIRECT) scale (2020)
A score of ≥2 has a NPV of 75-86% and PPV of 82-91% for LVO. However they have a NPV of 94% and PPV of 53% for thrombectomy.

GAI2AA Scale (2019)
A score of ≥3 has a PPV of 0.71 and a NPV of 0.95, so a false negative rate of only 5%. However, the prevalence of LVO was considerably lower in this study than in others, which improves its NPV. The author's propose that such a scale could be used to help triage patients directly to the angiography suite and avoid CTA prior to it. By using it, they lowered the door to puncture time by 40 minutes.

Mobile stroke unit
Mobile stroke units are highly accurate at making triage decisions (100%) in one study.

Comprehensive vs. primary stroke center first?
Although it was not statistically significant, in a study of 410 patients with LVO, patients directly admitted to a comprehensive stroke center had a trend to better outcomes (good outcome = mRS 0-2) than those undergoing drip-and-ship (33.5% vs. 24.3%, p=0.056).

Stroke unit
Admission to a dedicated unit (stroke unit, ICU) with neuroscience physician and nursing expertise for all ischemic stroke patients is a Neurocritical Care Society Clinical Performance Measure.

Interfacility transfer
Patients may have improvement during interfacility transfer (in one study, 19% improved with a decrease in NIHSS of 4 or more points).

It is important for primary stroke centers to have a Quality Improvement project, which can substantially reduce delays in getting the patient transferred.

A major source of delay is obtaining a CTA at a spoke hospital, which is associated with a predicted additional time of care of 94 minutes longer prior to groin puncture.

Stroke Center Volume
Outcomes are improved at centers that do at least 2 acute thrombectomy cases per month.

Readmissions
Readmission to a hospital within 30-days of an infarction occurred in approximately 12.6% of patients in one large study of the Nationwide Readmissions Database. The most common reasons for readmission were acute cerebrovascular disease, septicemia, and occlusion or stenosis of precerebral arteries. Of the readmissions, 29.6% were readmitted to a different hospital. For those readmitted to a different hospital, the hospital length of stay was 1.1 days longer (95% CI 0.9-1.4 days), cost was $9,174 more expensive (95% CI $6,962-11,386), and mortality was higher (aOR 1.2, 95% CI 1.1-1.3).

In an analysis of the PharMetrics database, readmission within 30-days of infarction occurred in 7.3% of patients, and within 90 days in 13.7% of patients. Most readmissions were for acute ischemic stroke. Follow-up with primary care within 30 days was associated with a reduced rate of readmission (HR 0.84, 95% CI 0.72-0.98). Therefore, early follow-up with primary care is important. Follow-up with primary care within 30 days may reduce readmissions by 16%, for a NNT of 6.