LAS VEGAS – Management of blunt cerebrovascular injuries using 64-channel computed tomographic angiography screening coupled with digital subtraction angiography for a definitive diagnosis is safe and effective for identifying clinically significant injury and for maintaining a low stroke rate, according to a review of 228 cases.
The computed tomographic angiography (CTA) screening was positive in 189 patients (83%), and digital subtraction angiography (DSA) confirmed injury in 104 (55%) of those. The remaining 39 patients were found to have no injury on DSA, Dr. Charles P. Shahan of the University of Tennessee, Memphis reported at the annual meeting of the American Association for the Surgery of Trauma (AAST).
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Stroke related to blunt cerebrovascular injury (BCVI) occurred in five patients (4.8%); three of those patients were symptomatic at the time of presentation, and two became symptomatic while on therapy for a known lesion. None of the patients who had a negative screening CTA, including three with injuries missed on CTA, had a stroke, Dr. Shahan said.
The current study follows a prior study reported at the 2013 AAST annual meeting that suggested that 64-channel multidetector CTA could be the primary screening tool for BCVI. The previously used 32-channel multidetector CTA was found to be inadequate, with a sensitivity of only 52%. Sensitivity increased to 68% with the 64-channel CTA, but the positive predictive value remained remarkably low at 36%, he said.
That study led to a change in the screening algorithm, replacing DSA with CTA for screening, and reserving DSA for definitive BCVI diagnosis following a positive CTA or unexplained neurologic findings, he explained, noting that the rationale was that most injuries missed were low-grade injuries less likely to result in further injury, and that with CTA alone, about two-thirds of patients would be treated unnecessarily because of the false-positive rate.
The purpose of the current study was to evaluate outcomes in the wake of the algorithm change and to assess the potential for missed, clinically significant BCVI.
Study subjects were patients who underwent DSA over an 18-month period after implementation of the algorithm change. Most (64%) were men with a mean age of 43 years and a mean injury severity score of 22 out of 75, indicating moderate or severe injury.
The stroke rate was statistically unchanged in the second study, compared with the first. The findings demonstrate the safety and efficacy of the current management algorithm for BCVI, as well as the value of using DSA to identify false-positive CTA findings. In fact, definitive diagnosis by DSA led to avoidance of potentially harmful anticoagulation in 45% of CTA-positive patients, with no increase in the incidence of strokes resulting from injuries missed by CTA, Dr. Shahan said.
“Considering there were 85 false-positive CTAs, and also considering that our average length of heparin time is approximately 7 days prior to reevaluation, we’ve extrapolated this to nearly 600 heparin infusion days that were avoided by confirmatory DSA testing,” he said, concluding that “CTA with 64-channel multidetector technology with experienced radiology staff in a high-volume center can be safe and effective for BCVI screening.”
He added, however, that false-positive rates with CTA continue to necessitate DSA confirmation to avoid overtreatment.
“We feel that CTA screening with DSA confirmation has allowed us to maintain an acceptably low stroke rate and prevented a tremendous amount of unnecessary anticoagulation in these patients,” he said.
Dr. Clay Cothren Burlew, who was an invited discussant for Dr. Shahan’s paper, applauded Dr. Shahan and his colleagues for “continuing to question the validity of CTA as our primary diagnostic modality for BCVI,” and said the findings made her “stop and think, should we all be doing confirmatory angiography? … Are CTAs actually overcalling 45% of the injuries that we identify?”
Dr. Burlew of the University of Colorado, Denver, questioned whether the high rate of false positives is a result of radiologists who “overcall” questionable findings knowing that a confirmatory angiogram will quickly follow.
“I think this evaluation should be a model for others. Each institution should critically review their individual rates and methods of BCVI diagnosis,” she said, adding that “for centers with a marked increase in the identification of BCVI following institution of CTA as their screening tool, consideration of confirmatory angiography is recommended due to the potential false-positive rate of up to 45%.”
However, confirmatory angiography may not be warranted at centers whose screen yields remain the same with no missed injuries, she said.
“All programs should evaluate their injuries, appropriateness of diagnosis, and impact of subsequent treatment. Only then will we have optimal outcomes,” she concluded.