HONOLULU – Covert strokes are relatively common in elderly patients who undergo noncardiac surgery, with a 7% incidence among a group of prospectively followed but generally unselected patients in a multicenter, international study.
By definition, these covert strokes were acutely asymptomatic, but showed evidence of clinical effects during the subsequent year. Twelve months after surgery, patients with acute, perioperative covert strokes found by systematic collection of postoperative MRI brain scans had a twofold increased rate of cognitive decline and a greater than twofold increased rate of delirium, compared with the patients who did not have evidence of a covert stroke, Marko Mrkobrada, MD, said at the International Stroke Conference sponsored by the American Heart Association.
The message from these findings is that, when elderly patients exhibit confusion or delirium after noncardiac surgery, their physicians should have a high index of suspicion that a covert stroke may have occurred, Dr. Mrkobrada said in a video interview. It’s possible that typical stroke symptoms do not appear in many of the covert stroke patients because they are masked in the immediate postoperative period, he added.
Right now, the only way to screen for a covert stroke is with a brain MR, a test that generally costs several hundred dollars, which is too expensive for routine screening. Dr. Mrkobrada said that his team hopes further study will identify a biomarker that can flag patients with a covert stroke at a lower cost. For example, colleagues of Dr. Mrkobrada have successfully used high-sensitivity troponin T, a biomarker of myocardial injury, to identify patients who have myocardial injury after noncardiac surgery (MINS; JAMA. 2017 April 25;371:1642-51). Study results also established that treating MINS patients with dabigatran improved their long-term clinical outcomes (Lancet. 2018 June 9;391:2325-34).
Covert stroke after noncardiac surgery “is the same concept” as MINS, said Dr. Mrkobrada, a researcher at the London Health Sciences Centre in Canada. “We find strokes that do not get picked up after noncardiac surgery just like MIs that are not picked up,” he said. It’s also possible that certain interventions may improve outcomes in patients with covert strokes, just as they have helped MINS patients, he suggested. Potentially helpful interventions could include aspirin, a statin, and improved blood pressure control. A major goal for his research group is finding a biomarker that makes diagnosing covert stroke as easy as using high sensitivity troponin T to diagnose MINS.
The NeuroVISION (Detection and Neurological Impact of Cerebrovascular Events In Noncardiac Surgery Patients: A Cohort EvaluatioN) study enrolled and tested 1,114 people aged 65 years or older scheduled for elective noncardiac surgery anticipated to keep them hospitalized for at least 2 days at any of 12 participating centers in nine countries. Patients underwent cognitive function testing before surgery and had a brain MR scan 2-9 days after surgery, and they were excluded if they developed an overt stroke prior to the scan. Patients underwent a second round of cognitive testing a year after surgery. Patients averaged 73 years old.
The screening MR scans identified covert strokes in 78 of the study subjects (7%). The 1-year cognitive tests showed measurable drops in cognitive function in 42% of those who had experience covert strokes and in 29% of everyone else. Those rates translated to a doubled odds ratio for cognitive decline after covert stroke, compared with people without covert stroke after adjustment for baseline between-group differences, a highly statistically significant between-group difference for the study’s primary endpoint. Delirium occurred 2.2-fold more often in the covert stroke patients after adjustment, and overt strokes during 1-year follow-up were 4.1-fold more common patients who’d experienced a covert stroke, compared with everyone else, after adjustment, Dr. Mrkobrada reported. NeuroVISION is the first large-scale study to assess the incidence and associations of covert strokes after noncardiac surgery, he noted.
SOURCE: Mrkobrada M. ISC 2019, Late-Breaking Abstract LB18.