Conducted over the course of eight years at 69 medical centers in the U.S. and Canada, the RESPECT study followed 980 participants who had suffered a cryptogenic stroke that was confirmed by stroke neurologists using routine imaging technologies. The average age of the patients in this trial was 46-years old. The trial was a prospective, controlled, randomized (1:1) study in which patients were randomly assigned to either the device group or the medical group. The primary efficacy endpoint was defined as the composite rate of recurrent nonfatal stroke, fatal ischemic stroke or death after randomization. Enrollment was stopped once 25 events occurred, all of which were non-fatal recurrent stroke, as measured across all patients in the study.
Patients in the device group underwent a procedure in which their PFO was closed with the Amplatzer PFO Occluder followed by six months of medication therapy. In the medical group, four standard-of-care medical therapy regimens were used throughout the study: aspirin, warfarin, clopidogrel and aspirin combined with extended release dipyridamole.
Analyses were conducted on the intent-to-treat population, which included all patients according to the group to which they were randomly assigned, though some patients in the device group did not receive the randomized treatment. A difference in the dropout rate between the medical therapy group and the device group challenged the validity of the primary intent-to-treat raw count analysis, which did not meet statistical significance. Using the same intent-to-treat cohort in a time-to-event analysis demonstrated a risk reduction of greater than 50 percent, which trended towards statistical superiority with a p-value of 0.08.
The study protocol also prespecified that if dropout rates differed significantly between the medication and device groups that analyses of two additional cohorts would be evaluated. These included:
- Per-protocol cohort – patients who received the randomly assigned treatment and adhered to the protocol-mandated medical treatment
- As-treated cohort – patients who received and adhered to a protocol-approved treatment and were classified according to the treatment they actually received