A 53-year-old woman who had severe mitral regurgitation associated with moderate tricuspid regurgitation and mild aortic regurgitation underwent mitral valve replacement with a 27 mm Björk-Shiley mechanical valve, left atrial plication and tricuspid annuloplasty. She fell into low output syndrome on the first postoperative day because of persistent intractable ventricular arrhythmia and eventually required open cardiac massage. The left ventricular (LV) bypass using a centrifugal pump was initiated with cannulation to ascending aorta and left atrium. Echocardiography showed LV wall motion extremely poor with the prosthetic valve being in closed posture. For prevention from thrombus formation on the prosthetic valve and in the LV, a catheter was inserted into LV through RV to give heparin and monitor the LV pressure. As the result, activated clotting time of LV was higher (range from 280-388 sec) than that of systemic blood (range from 182-258 sec). Also, the change of LV pressure was monitored through this LV catheter. Under this monitor, IABP was smoothly applied in the presence of aortic regurgitation, and she was weaned from LV-bypass successfully after 157 hrs support. She was discharge on the 77th postoperative day without thromboembolic complication.