We report a 75-year-old man with ischemic cardiomyopathy who had mitral regurgitation which was increased markedly by intermittent left bundle branch block (LBBB). He complained of angina-like chest pain that was preceded by episodes of LBBB. During LBBB, a marked elevation of the V wave in the pulmonary capillary wedge pressure was shown, and an increase in mitral and tricuspid regurgitation was observed with color Doppler echocardiography. Biventricular pacing (BVP) therapy was selected so as to protect the patient from episodes of LBBB. After BVP, the patient did not experience chest pain or dyspnea. This case sheds valuable light on the ongoing investigation of the hemodynamic benefit of BVP.