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This report is being submitted as follow up no.1 to provide additional information in section b5 and d10, to provide the device return date in section d9, update section h3, and to provide the completed investigation results.The actual sample was received for evaluation.Visual inspection revealed a kink at approximately 190 mm from the distal end.The handle was confirmed to have been disassembled.This was thought to be due to the bailout for taking out the system from the patient as described in the complaint.Magnifying inspection of the kinked section found that the adhesion between the cover sheath and the distal shaft had been separated and the edge of the cover sheath had been rolled up distally.Magnifying inspection of the catheter shaft found a crush at approximately 180 mm from the distal end, which was near the kink.No other kink, crush, or other deformity was observed in other parts of the catheter shaft.Magnifying inspection of the distal tip section found no kink, crush, or other deformity.Magnifying inspection of the stent-mounted section found no kink, crush, or other deformity in the stent sheath.Electron microscopic inspection of the kinked section (adhered section at approximately 190 mm from the distal end) revealed multiple abrasion on the rolled-up part of the cover sheath and the distal shaft.Electron microscopic inspection of the crushed section (at approximately 180 mm from the distal end) revealed multiple abrasions on the surface.Electron microscopic inspection of the stent-mounted section found deep abrasions on the distal end of the stent sheath, in addition, multiple abrasions were observed on the area approx.80 mm from the distal end of the stent sheath.No abrasions were observed in other parts of the stent sheath.From the findings, it was presumed that a hard object such as a stenotic lesion might have come into contact with the above-mentioned parts.X-ray fluoroscopic inspection of the kinked section at approximately 190 mm from the distal end revealed that the inner shaft and the release wire had been kinked also.The lumen of the stent sheath had become narrower than normal due to the kink; therefore, it was in close contact with the release wire and the inner shaft.No other anomalies such as disconnection of the release wire were observed in other parts inside the catheter shaft.An attempt to insert the actual sample over a factory-retained 0.035-inch guidewire was made.As a result, the actual sample was stuck due to its kinked section at approximately 190 mm from the distal end.Next, stent release was attempted by directly grasping and pulling on the release wire inside the handle.As a result, it was confirmed that the stent would not deploy.This was thought to be due to the cover sheath, release wire, and inner tube shaft being in close contact due to the kink, as confirmed in the investigation result 9, which prevented the sheath from moving toward the distal end.However, according to the description of the event, the actual sample was possible to be inserted over the guidewire during the event; therefore, the kink was thought to be not the factor of the stent deployment failure.The outer diameter of the stent-mounted section was measured and confirmed to meet the factory's control standards.No dimensional anomaly was observed.Simulation test 1: release while the cover sheath or the distal end of stent sheath is trapped in a stenotic lesion.To simulate the occurrence situation, using a lower extremity vascular model we performed a contralateral approach (crossover) with a 6fr destination.Then, a 0.035-inch guidewire was inserted in the destination, and a misago (the test sample-1) was inserted up to the left cfa of the simulated vessel model.Since the deep abrasions at the distal end of the stent sheath and a crush at approx.180 mm from the distal end were observed on the actual sample, in order to simulate a stenotic lesion, the involved part of the test sample-1 was restrained along with the simulated vessel with tie band.Then, an attempt was made to release the stent.As a result, the following behavior was observed.At 8 clicks, the proximal shaft located outside the body and the sliding part located inside the body became rippled, and with each subsequent click, the rippling of the proximal shaft and sliding part progressed.At 13 clicks, the stent had not yet deployed.Even when the number of clicks was increased to 15 clicks (upper limit of the number of clicks stated in the ifu) and 18 clicks, it did not deployed.When it reached to 20 clicks, the stent began to deploy.Then an attempt to remove the test sample-1 was made but failed because the distal end of the stent sheath and the area approximately 180 mm from the distal end (cover sheath) were trapped in the simulated stenotic lesion.In order to remove the test sample-1, system removal was done.Magnifying inspection of the test sample-1 found no kink, however, the edge of the cover sheath at approximately 190 mm from the distal end had been lifted.This was thought to have been caused when the adhesive area between the cover sheath and the distal shaft was separated due to sagging of the sliding part inside the body during release.In the ifu of the product in question, it is stated that the stent starts to deploy approximately in 10 to 15 clicks.The reason for the failure of the actual sample to deploy stent at the number of clicks at which it should have deployed was thought to be that the actual sample during the event was in the similar situation as the simulation test above.In addition, during the above simulation test, no kink occurred in the test sample-1 when the guidewire was inside it, so the kink at approximately 190 mm from the distal end of the actual sample was considered to have occurred during the handling process after use.Simulation test-2: kink and rolled-up cover sheath: since the kink at approximately, 190 mm from the distal end of the actual sample was not reproduced in the simulation test-1, a bending load was applied to the same part of a factory retained misago sample (the test sampe-2).As a result, the adhesion between the cover sheath and the distal shaft became separated and the edge of the cover sheath became lifted.Next, when the lifting part was hooked with fingers, the edge of the cover sheath became rolled up in the distal direction.The state of the test sample-2 of the simulation test 2 was similar to that of the actual sample.Ifu states: as a guide, stent deployment commences on rolling back the thumbwheel 5-10 clicks for stents up to 100 mm long and 10-15 clicks for stents at least 120 mm long.Carefully roll back the thumbwheel one click at a time and adjust the position of the stent just prior to deployment if necessary (otherwise the stent can be deployed in the wrong position).Deploy the stent completely, even if the delivery catheter bends and corrugates.If the stent does not start to deploy when the thumbwheel is rolled back, if no corrugations can be seen in the delivery catheter, stop rolling the thumbwheel, observe using high-resolution fluoroscopy, and then carefully remove the stent system.(the stent system could become unrecoverable.) to assure optimal stent delivery, confirm that the pre-dilation is properly done before stenting patients who have highly tortuous or calcified lesions and/or vessels proximal to the lesion.Based on the provided information and investigation results, there is no definitive evidence that this event was related to a device defect or malfunction.According to the investigation results, deep abrasions were observed at the distal end of the stent sheath and the crush was observed on the cover sheath about 180 mm from the distal end, which suggested that the area was trapped by some hard object (e.G., stenosis).This may have prevented the sheath (sliding part) from moving toward the proximal side during release, and the stent could not be deployed in the number of clicks that it should have been deployed (10-15 clicks).In addition, the actual sample could not be removed since it was in the trapped state.It was likely that, when the release was attempted while the actual sample was in the trapped state, the sliding part (about 190 mm from the distal end: the position of the kink) was sagged inside the body.Due to this, the adhesive between the cover sheath and the distal shaft was separated and the edge of the cover sheath became slightly lifted.The kink of the actual sample at approximately 190 mm from the distal end and the rolled-up edge of the cover sheath were likely to have been caused by the following mechanisms after the occurrence of the event.In the process of handling the product after use (e.G., storing the catheter in a round shape), a bending load was applied to the relevant part, causing it to kink, which promoted the lifting of the edge of the cover sheath that had occurred during the procedure.After that, the floating part of the cover sheath was caught during the process of handling, causing the adhesive part to separate and the edge of the cover sheath to roll up distally.The exact cause of the reported event cannot be definitively determined based on the available information.
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