OBJECTIVE: The purpose of this study was to evaluate the hemostatic efficacy and safety of the Mynx extravascular sealant for femoral artery closure. BACKGROUND: The Mynx device is an extra-arterial vascular closure technology utilizing a water-soluble, porous, polyethylene glycol matrix that immediately seals the arteriotomy by rapidly absorbing subcutaneous fluids and expanding in the tissue tract and then, resorbs within 30 days. METHODS: The Mynx study was a prospective, multicenter, single-arm clinical investigation conducted at five European centers. The safety and effectiveness of the Mynx device was evaluated in patients following diagnostic or interventional endovascular procedures performed through 5 Fr, 6 Fr, or 7 Fr introducer sheaths in the common femoral artery. The primary safety endpoint was the combined rate of major complications within 30 days (+/-7 days). The primary efficacy endpoints were time to hemostasis and time to ambulation. RESULTS: Patient enrollment included 190 patients with 50% having undergone diagnostic catheterization and 50% interventional procedures with a mean activated clotting time of 221 sec. One (0.5%) major vascular complication (transfusion) occurred in one patient. No device-precipitated complications associated with serious clinical sequelae were reported. Mean (+/- standard deviation) times to hemostasis and ambulation were 1.3 +/- 2.3 min and 2.6 +/- 2.6 hr, respectively. There was no significant difference in median times to hemostasis between diagnostic and interventional patients (0.5 vs. 0.6 min). CONCLUSIONS: The initial experience with the extra-arterial Mynx closure technology supports hemostatic safety and efficacy in patients undergoing diagnostic and interventional catheterization procedures.