Case Summary. For round stump chronic total occlusion with left antegrade bridging collateral, the antegrade approach was not always easy and in our case, we failed in antegrade approach. In this case, the important key to success is the choice of retrogade channel and as it was not clear. Choosing another angulation of angiogram is important. The other is: as we meet difficulties in advancing retrograde micro- catheter, we can do anchor balloon technique in stead of deep seating retrograde guide to avoid complication. TCTAP C-120 Nightmare of CTO PCI at Night: Don’t Let Small Consecutive Mistakes Lead to Big Disasters Hieu Ba Tran, 1 Quang Ngoc Nguyen 1 1 Vietnam National Heart Institute-Bach Mai Hospital, Vietnam [CLINICAL INFORMATION] Patient initials or identifier number. Mrs. NGUYEN T.A. Relevant clinical history and physical exam. A Female 56 years old, NYHA II-III, admitted due to exertional chest pain. Her CVD risk factor included: hypertension, hypercholestemia. Her stable angina become relevant 1 year ago but recently more angina episodes happened without any reliefs by antiangina medications. Her ECG showed Q wave of old infarction in inferior and anterior wall. Echocardiography results showed severely reduced LVEF of 25% with hypokinesia in all wall motion and moderate MR. Relevant test results prior to catheterization. After discussed with heart team, patient refused bypass and would like to have PCI. Attempt to open mLAD CTO was decided. Relevant catheterization findings. After crossing mLAD CTO lesion with Gaia 3 wire, the micro catheter very difficult to pass through the lesion. After predilatation with 1.25 mm balloon, the micro catheter can pass through the lesion, however tip injection through micro- catheter showed perforation at mLAD lesions. [INTERVENTIONAL MANAGEMENT] Procedural step. Face to coronary perforation at mLAD CTO due to wrong wiring at night. Use deflation with negative pressure to suck the micro catheter in the false lumen Put second wire into septal branch and inflation from proximal LAD to septal 1 with 2.5 balloon to stop perforation. However, the tricky sit- uation is the septal to inflate was the main source of collaterals for distal RCA vessels and BP will go down if balloon inflated too long. Deflation and inflation should be consequently to avoid hemodynamic deteriotation. Check bedside echocardiography showed mild effusion without any hemodynamic deterioration. No protamin was used. After long balloon inflation at septal branch, selective angiogram showed no more perforation, repeated bedside echo did not show expanded effusion, and patient was transferred to CCU to monitor closely when the hemodynamic was stable. On CICU few hours later: BP come down with moderate effusion in bedside echocardiography and elevated level of blood lactate. Peri- cardiostomy was done at CICU and clinical manifestation improved immediately. Pericardial drainage was less next morning and finally, patient discharged well 5 days later JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY, VOL. 69, NO. 16, SUPPL S, 2017 S209