Changes in Ischemic Patterns on CT Predict Subsequent Stroke Risk

Patients who have a transient ischemic attack (TIA) or nondisabling stroke are more likely to experience another stroke within 90 days if they show signs of ischemia on CT, according to a study published online December 4, 2014, ahead of print in Stroke. Moreover, CT findings can help predict whether repeat strokes are more likely to occur within the first 2 days after the index event or beyond.

Take Home: Changes in Ischemic Patterns on CT Predict Subsequent Stroke RiskJeffrey J. Perry, MD, MSc, of the Ottawa Hospital (Ottawa, Canada), and colleagues prospectively enrolled 2,028 patients (average age 67.9 years; 50.2% men) with TIA or nondisabling stroke who received a CT scan within 24 hours of symptom onset at 8 Canadian centers between October 2006 and April 2010.

Overall, patients with evidence of ischemia or microangiopathy on CT had a higher ABCD2 score—which takes into account age, blood pressure, clinical features, TIA duration, and diabetes status—than those without.

Acute Ischemia Increases Stroke Risk

CT-identified ischemia was reported in 814 patients (40.1%) and characterized as acute ischemia in 4.2%, chronic ischemia in 24.2%, and microangiopathy in 18.8%.

Repeat stroke occurred at a rate of 3.4% within 90 days of the initial TIA/nondisabling stroke (1.5% within 2 days and 1.9% beyond 2 days). Almost half of these events (48.6%) occurred in patients with evidence of ischemia.

Acute ischemia was associated with higher 90-day risk of stroke, both when observed alone (P = .002) and in conjunction with chronic ischemia (P = .007), microangiopathy (P = .019), and chronic ischemia and microangiopathy (P = .029). The association between CT findings and repeat stroke held true when the timing of the subsequent event was within 2 days. However, only the presence of acute ischemia (P = .019) and chronic ischemia (P = .034) were tied to repeat stroke occurring between 2 and 90 days.

On logistic regression analysis, acute ischemia on CT was linked to repeat stroke within 90 days singularly and in combination with other forms (table 1).

Table 1. Association Between CT Findings, Repeat Stroke Within 90 Days

After multivariable adjustment, the presence of acute ischemia and its various combinations remained associated with increased stroke risk within 2 days, with only a trend for acute ischemia alone. Additionally, between 3 and 90 days, increased stroke risk correlated solely with acute ischemia.

Of the 34 patients with evidence of ischemia or microangiopathy on CT who went on to have a stroke within 90 days, 14.7% were considered by ABCD2 criteria to be low risk, 50.0% medium risk, and 35.3% high risk.

Median ABCD2 scores in the groups with microangiopathy or chronic ischemia on top of acute ischemia were not different than the scores of patients without similar CT findings, “despite the fact that both of these groups were strongly associated with an increased risk of stroke,” the authors state.

Add CT to ABCD2 Score?

Dr. Perry and colleagues say the study demonstrates “for the first time” that the pattern of ischemic change can be used to determine when a patient will be at a high risk of stroke.

Building upon previous findings that ABCD2 score alone is insufficient to predict stroke risk, the authors suggest that the addition of CT imaging may improve its predictive ability. “Our study confirms the value of adding imaging to the clinical data for predicting which patients are at high risk for stroke after TIA,” they say. “In particular, we found that although most patients with CT evidence of ischemia or microangiopathy had a higher ABCD2 score than those without comparable findings, many who went on to have a stroke were still classified as low or medium risk.”

Furthermore, the authors say their research confirms the idea that early stroke risk could be attributed more to nondisabling stroke than to TIA.

Joseph P. Broderick, MD, of the University of Cincinnati (Cincinnati, OH), pointed out in an email to TCTMD that the researchers “mix patients with traditional TIA and those with mild acute strokes. [As such, it] may be hard to separate worsening related to the first stroke (a not infrequent occurrence) vs a clearly new stroke in some patients.”

Although CT imaging is not currently used in the capacity examined by the study authors, “there are clinical scores with and without MR imaging [including ABCD2] that do predict likelihood of new stroke,” Dr. Broderick explained.

 


Source:
Wasserman JK, Perry JJ, Sivilotti MLA, et al. Computed tomography identifies patients at high risk for stroke after transient ischemic attack/nondisabling stroke: prospective, multicenter cohort study. Stroke. 2014;Epub ahead of print.

Disclosures:

  • Dr. Perry reports receiving funding from a Canadian Institutes for Health Research New Investigator Award and previously from the Ontario Ministry of Health.
  • Dr. Broderick makes no statement regarding conflicts of interest.

Related Stories:

Changes in Ischemic Patterns on CT Predict Subsequent Stroke Risk

Comments