Jailed Balloon Technique in Side Branch Protection in Coronary Intervention

INTERVENTION: Coronary artery disease patients with side branch arising from target lesions are randomly divided into 2 groups. Group 1 patients will use new technique: leaving 1 small balloon in side branch ostium before main branch stent inflation, proximal part of balloon protruded into the main branch and jailed between the main branch stent and the vessel wall. After inflation of main branch stent at low pressure, if the blood flow of side branch were affected, then the balloon were inflated immediately to recover the side branch blood flow. Rewire the side branch wire through the stent cell and post dilate stent with post‐dilation balloon at high pressure to make sure the stent expanded fully. Side branch can be post dilated or stented according to the operator's intention. For one side branch, this technique will occur only once and will spend about 1 hour to finish the whole procedure. CONDITION: coronary artery disease PRIMARY OUTCOME: side branch occlusion rate after the procedure. The side branch occlusion will be diagnosed if the side branch TIMI flow is 0 or 1 grade in angiogram after crossed by main vessel stent. SECONDARY OUTCOME: chest discomfort during the procedure. The chest discomfort will be assessed by the symptoms and ECG changes. cost related to the procedure. The cost will be recorded by one nurse in cath lab after the procedure. Cath lab is the place where the angiography and coronary intervention is performed. myocadial infarction rate after the procedure. The myocardial infarction will be diagnosed if the CK‐MB is elevated 3 times upper limited value. CK‐MB will be tested at baseline, 4h, 24hs, 3 days after the procedure. procedure time radiation exposure dose. The exposure dose will be showed on the medical equipment automatically and will be recored by the technician. INCLUSION CRITERIA: coronary artery disease patients with side branch arising from target lesion