Procedural Blinding and Randomization

The randomization code was generated independently from the investiga-tional sites and personnel by the Biostatistics Department of the University of Bergen, Institute of Medicine. Individual, sealed patient envelopes were prepared and provided to the laser operator, who maintained these envelopes in a locked safe. Throughout this trial, only one individual participating in the procedures, the laser operator, was aware of the randomized assignments. To assure blinding of the patients, treating investigators, and staff during the procedure, the laser console and the laser operator were placed behind an opaque curtain out of view in the cardiac catheterization laboratory. Two laser catheters were pre-calibrated to produce an identical response from the laser. At the initiation of every procedure, the patient was instrumented with a sterile guiding catheter and one of the laser catheters. The distal end of the other laser catheter was placed into a lead box behind the opaque curtain. The laser technician, positioned behind the curtain, then opened the treatment assignment envelope. Depending on the group assignment, the proximal end of the sterile catheter positioned in the patient's left ventricle (PML assignment) or of the catheter terminated to the lead box (sham assignment) was connected to the laser console by the laser operator. In the PML group, pulsed-laser energy was delivered to the endocardium through the laser catheter to create a nontransmural channel. For the sham group, the procedure was identical except there was no laser energy delivered to the patient when the interventionalist activated the footswitch. Throughout the procedure, music was played. There was no visual or audible feedback from the laser system that could reveal the randomized assignment.

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