When the investigators examined the rate of good 90-day outcome (defined as an mRS of 0-2), they found the best outcomes in patients with the lowest baseline NIHSS scores. "As the stroke became more severe, the likelihood of good outcome went down," she said. In cases with NIHSS scores lower than 16, "the outcomes were excellent," she said, with up to 70% of those with a TICI grade of 2b or 3 experiencing a good outcome. TICI 2a provided only modest benefit, but it was consistent across the whole range of NIHSS scores, she added.
Age and recanalization status also affected mortality. "Age was a predictor of worse outcome, but recanalization did provide benefit across all ages except for the very young, who had low mortality rates in any case," she said.
A multivariate analysis identified several factors that significantly affected mortality both negatively and positively, including advancing age (odds ratio, 1.05), worse baseline NIHSS score (OR, 1.08), revascularization to a TICI grade of 2a, 2b, or 3 (OR, 0.33), heart failure (OR, 2.85), blood glucose above 140 mg/dL (OR 2.0), and intubation during the revascularization procedure (OR, 2.20)
The same multivariate model also identified factors that negatively impacted good 90-day outcomes, including worse baseline NIHSS score (OR, 0.88), advancing age (OR, 0.96), intubation during the procedure (OR, 0.43), longer duration of procedure (OR, 0.66), and a blood glucose level of 140 mg/dL or greater (OR, 0.59).
During the discussion period, several audience members questioned the relationship between intubation and poor outcomes. Dr. Joseph Broderick, chair of the department of neurology at the University of Cincinnati, said that the intubation data were interesting but could throw a statistical kink into the risk analysis. "How do you take into account those centers with a 100% intubation rate?" he asked. "Why don’t you analyze the data separately and see if the risk of intubation still holds up? There is always a risk of selection bias unless you compare the [sites] that always intubated against those that did not. Otherwise, you might be including people who were intubated because they looked dead, had heart failure, or weren’t breathing."
Three other speakers echoed the same concern, with one suggesting that intubation could lead to aspiration pneumonia, which in turn could contribute to a bad outcome.
"We don’t know what all the facts are" in relation to intubation, Dr. Rymer said. "We can only speculate."
However, the discussants also emphasized that there are still no randomized data confirming the device’s efficacy when compared with medical therapies. "There is, however, a clear association of improved outcomes with better revascularization," Dr. Rymer said in an interview.
Both MERCI and Multi MERCI were criticized for comparing their device-treated populations with only a placebo arm of PROACT II, according to an editorial by Dr. Kyra J. Becker of the University of Washington and Dr. Thomas G. Brott of the Mayo Clinic in Jacksonville, Fla. (Stroke 2005;36:400-3).
They said that the data presented to the Food and Drug Administration for the device’s approval did not meet the standards that could be achieved in a randomized trial.
"These data certainly provide no reassurance about the safety of mechanical embolectomy, yet alone the efficacy," the authors said. "The risks of treatment with the Concentric clot retriever might not be limited to arterial perforation, dissection, or distal embolization; there could be unidentified risks associated with the required immediate poststroke angiography as well as with endovascular instrumentation and injury to the arterial endothelium. Unfortunately, these questions cannot be addressed with the data presented ... by the MERCI investigators. Randomized trials have a distinct advantage in this setting; they can control for variables we know are likely to relate to procedure success and outcome, and they can control for important variables we have yet to identify."
Concentric Medical, the manufacturer of the MERCI device, sponsored the MERCI registry. Dr. Rymer reported being on the speakers bureau of the company. The five other coauthors reported varying relationships with Concentric, including being consultants or medical advisors, and having an ownership interest in Concentric.