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EVEREST II: Effectiveness of mitral valve debated, despite demonstrated safety
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Coverage from the Transcatheter Cardiovascular Therapeutics (TCT) 2010 meeting
Results from the EVEREST II trial suggest that the MitraClip system is safer than surgical options for mitral valve repair, but measures of effectiveness depended on how data were analyzed.
Two researchers debated results from the intent-to-treat analysis of major adverse events in patients with mitral regurgitation randomized to intervention with the MitraClip (Abbott Vascular; n=184 enrolled, 178 treated) or in patients who underwent surgical intervention (n=95 enrolled, 80 treated). The rate of major adverse events was much lower in the MitraClip group vs. the control group.
Saibal Kar, MD, of Cedars-Sinai Medical Center, Los Angeles, said that a modified analysis of safety outcomes that included bleeding events showed an even greater difference between the device and the control groups. Under the modified definition, the rate was 8.3% in the device group vs. 42.6% in the control group.
“No matter how you look at it, [the data] clearly show that the major adverse event rate is higher in the control group,” Kar said.
The effectiveness of intervention with the device was less clear from the data. Because EVEREST II was a strategy trial — device vs. surgery — investigators performed an intent-to-treat analysis to determine effectiveness.
However, because it was known from baseline that a certain number of patients would require subsequent surgery after device-based intervention (ie, device failure), a per protocol analysis also was conducted to eliminate bias introduced by surgical patients.
Ted Feldman, MD, of Evanston Hospital in Evanston, Ill., said that in the intent-to-treat analysis, “effectiveness” could be defined in several ways, and the resulting measure varied accordingly. For example, in what Feldman called a classic intent-to-treat analysis, 72.3% of patients in the device group vs. 74.2% of patients in the control group were free from death and more than 2+ mitral regurgitation at 12 months. When an intent-to-treat analysis of the initial strategy was performed, however, the rate was 55.2% in the device group vs. 73% in the control group.
Using criteria established before patient enrollment, the MitraClip device met the study’s primary effectiveness endpoint (MitraClip effectiveness at 72%, with mitral valve surgery effectiveness at 88%).
Feldman also noted that the per protocol effectiveness analysis suggested greater benefit for device-based intervention, pointing to a steady increase of mortality in the control group over time.
Disclosures:
- Dr. Feldman is a consultant for and has received research grants from Abbott Vascular.
- Dr. Kar is a consultant for and has received research grants from Abbott Vascular.