Under the circumstances that appropriate first-choice guidewires for percutaneous coronary intervention (PCI) for chronic total occlusion (CTO) have yet to be established, the objective of this study is to determine appropriate first-choice guidewires. G-FORCE study is a prospective multicenter randomized study between normal (distal tip size 0.014 inch) and slender (distal tip size 0.010 inch or less) guidewires. Primary end point is lesion penetration rate of the first choice guidewire.

Background. Although the success rate of PCI for CTO is yet to reach a satisfactory level, prognoses have been improved in successful cases. The greatest challenge is the passage of the guidewire and a variety of new approaches including a parallel wire technique and a retrograde approach have been reported. However, the fundamental question of what type of guidewire is the most appropriate as a first-choice guidewire has not been answered.Tapered guidewires have recently been reported to be useful for CTO lesions. In addition, a multicenter prospective registry indicates the effectiveness of 0.010-inch guidewires (PIKACHU registry, personal communication). Its mechanism is associated with micro-channels ranging from 100 to 300 μm in size in CTO lesions. If 250 μm micro-channels are present in 60% of CTO lesions, a 0.010-inch (equivalent to 250 μm) guidewire theoretically can pass through the lesion at the probability of 60%, and this assumption consists with the findings of the PIKACHU study. This idea also suggests that a 0.014-inch (350 μm) guidewire is unlikely to pass through lesions.

Based on the above, a hypothesis has been formulated that a guidewire with a small tip should be selected as a first-choice guidewire for CTO lesions. In this study, patients will be prospectively randomized to slender guidewires or standard 0.014-inch guidewires to determine appropriate first-choice guidewires.

Objective. To determine appropriate first-choice guidewires.

Design. Prospective multicenter randomized controlled trial

Methods. The first choice guidewire to treat CTO lesion was randomly assigned to normal group (distal tip size 0.014 inch) or slender group (distal tip size 0.010 inch or less). The primary passage must be performed with antegrade approach.

Primary endpoint. Lesion penetration rate of a first-choice guidewire

Power calculation. The PIKACHU registry indicates a 0.010 guidewire passes through a lesion with a success rate of 60%. Assuming the penetration rate of a 0.014 guidewire is 40%, a necessary number of patients would be 260 for a two-sided test with 90% power and significance level of 0.05. Assuming the dropout rate is approximately 10%, the target sample size would be 290 patients.

Inclusion Criteria:

• Chronic total occlusion (CTO) lesion in native coronary artery
• De novo lesion
• Elective procedure

Exclusion Criteria:

• No indication of PCI
• Prior failed lesion
• Restenotic or in-stent restenotic lesion
• Vein or arterial grafts
• Younger than 20 years old
• Pregnant woman
• Patients who gave no informed consent