1. Stress injury to the myocardium Although PCI is less invasive, the body instinctively produces a stress response to surgery. Excessive or prolonged stress can cause the destruction of the body’s adaptive capacity or the depletion of its adaptive potential. In order to prevent the effects of stress on patients, first, it is important to be aware of the effects of stress on patients undergoing PCI for coronary artery disease; second, to communicate well with patients and doctors to relieve tension and anxiety. Sedation in the evening before the procedure is necessary. Through careful communication and necessary medication, patients can achieve “double adaptation” psychologically and cardiologically. During PCI, the tip of the catheter remains in the coronary opening or at the beginning of the coronary artery and moves with the beating of the heart, and sometimes deep insertion of the catheter is required to provide stronger support for the operation, which can cause damage to the coronary endothelium and lead to the formation of endothelial tears or even entrapment, resulting in unpredictable consequences. These can cause damage to the coronary endothelium, leading to endothelial tears and even the formation of entrapment, with unpredictable consequences. In addition, the outside diameter of the catheter can have an impact on the detection of blood pressure. The larger outside diameter of 7F and 8F catheters can easily form an inlay in the coronary opening, which can affect the antegrade blood flow and slow down the excretion of contrast on the one hand, and affect the hemodynamic detection on the other hand. Therefore, careful reading of the imaging images and selection of a suitable and accurate guiding catheter is the key to successful PCI. Intraoperative cardiac monitoring and hemodynamic changes are always kept in mind. Be gentle and avoid using rough techniques. Strictly control the amount of contrast agent. 3, finger guide wire (guide wire) on the endothelium and vascular impact Different types of guide wire in the adjustment force, flexibility, pushing force and support force differences. When manipulating the guide wire, improper selection or operation of the guide wire may cause vasospasm and intimal tearing, which may lead to entrapment or even vascular perforation, especially when dealing with CTO lesions; or when dealing with bifurcation lesions, which may cause the stent outer guide wire to tear the proximal vessels. In order to avoid the above complications, the operator should have a full understanding of the comprehensive performance of the selected guidewire, and reasonably choose the guidewire he or she is skilled in using according to the lesion. 4. The effect of balloon dilation on the myocardium The balloon plays an important role in the PCI process, but it can also cause certain damage to the myocardium. In order to avoid or minimize the damage to myocardium caused by balloon dilation, (1) when performing emergency PCI, it is not easy to choose a pre-dilated balloon that is too large for the purpose of opening the vessel and understanding the distal lesion. For lesions with excessive thrombus load, it is better to aspirate first, avoid repeated balloon expansion, and avoid repeatedly pushing the balloon back and forth to reduce the chance of “slow flow” and “no recurrent flow”. (2) In patients with elective surgery, the balloon should not be too large for soft lesions of straight vessels; relatively large and long balloons should be chosen for long twisted lesions or combined with calcification; cuttinge balloom should be used to dilate bifurcated or open lesions; “post-dilation” should be the mainstay for long lesions, and pre-dilation or stent dilatation should be the mainstay for limited or staged lesions. If the heart function is normal, it can be dilated several times for a short period of time to “pre-adapt”, and if the heart function is poor, the shorter the time of dilatation, the better. (3) For complex lesions, bifurcation lesions and vessels not requiring stenting, it is better not to “pre-dilate”; for those whose main branch stent has obvious influence on the opening of the side branch, it can be solved by anastomotic dilation; for those whose side branch is severely stenosed but the main branch is almost normal, only the side branch can be dilated by cutting balloom; for slow closing lesions, after the guiding wire is opened Only after confirming the true lumen at the distal end of the vessel, small balloons and progressively larger balloons can be used to dilate. 5. The effect of stent release on the myocardium Stent release is the “grand finale” of the entire PCI process, from stent selection to stent positioning and release, each step is full of excitement and danger. If the stent is selected too small, the stent may not fit the wall well; if the stent is selected too short, the two ends may be easily “shoveled”; if the stent is too long, the restenosis rate is high. The result of thrombus and debris dislodgement, or damage from the above mentioned operations, leads to “slow flow” or “no reflow” phenomenon, and can also cause blockage of tiny capillaries in the side wall. What can be done to prevent this? First, careful reading of the imaging images, careful analysis of the lesion characteristics, and detailed treatment methods. Secondly, rich experience in interventional treatment, skillful operation technique and gentle operation method. Once again, strict mastery of indications, pursuit of guidelines, and variation according to the time and person. Finally, adequate preoperative preparation and full understanding of the patient’s condition. 6.Summary PCI is a blessing to the patient but also comes with various risks, and the whole procedure seems simple but is not easy. Only by fully recognizing the risks are present everywhere.