Discussion
There are many reasons that make angiography catheter discount, including vascular tortuosity,
vasospasm, abnormal ostial of coronary artery, unskilled manipulation, excessive traction and rotation. Understanding the tortuosity of blood vessels in advance, and avoiding excessive rotation of the catheter, maintaining a guide wire in the catheter lumen can help us to prevent catheter from looping.
Once the catheter was knotted, inadequate manipulation and excessive traction can make catheter fracture or even artery dissection[4, 5]. There were several methods to retrieve catheter knot, such as gentle rotation of the catheter to the opposite direction, advancement of a super stiff wire into the loop, external fixation of the distal part of the catheter at the arm level with a blood pressure cuff[6], snare delivery[7-9]. In catheter ablation procedure, steerable sheath was also used to untie diagnostic decapolar catheter knot[10].
When it was difficult to withdraw the knotted catheter, we can advance a bigger cut guiding catheter outside the angiography catheter to strengthen the supporting power and exchange the shape of angiography catheter. Pushing the guiding catheter into the knot point and pulling the angiography catheter gently at the same time can help us to withdraw the knotted catheter. In our case, the internal diameter of 6 French EBU guiding catheter was 1.8mm, which was bigger than the external diameter of 5 French angiography catheter, which was 1.7mm, and make sure that the guiding catheter can enclose the angiography catheter. According to Aminian’s study[11], the length of guiding catheter was between “Knotted point- Puncture point” distance and “Knotted point- Cut point” distance, and the length of exceeded-guiding catheter part of angiography catheter was too short to fix, so that we make balloon and angiography catheter contact tightly and as a result we prolong the length of exceeded-guiding catheter part of angiography catheter sufficiently in order to facilitate the procedure, which was a bright point of our case.