['Little is known regarding the long-term performance of coronary sinus (CS) leads, which have an effect on the longevity of cardiac resynchronization therapy (CRT) systems.', 'This study included 109 patients (79 men) whose mean age was 68 +/- 9 years, New York Heart Association (NYHA) functional class 3.2 +/- 0.5, and left ventricular ejection fraction 25.6 +/- 6.6%, and who underwent CRT (n = 45) or CRT-D (n = 64) systems implants for management of idiopathic (53%), ischemic (40%), or miscellaneous (7%) dilated cardiomyopathy. Unipolar (n = 57) or bipolar (n = 52) leads were placed into the CS venous system.', 'At implant, no significant difference was observed between unipolar and bipolar leads with respect to mean sensing performance (14 +/- 6 mV vs 14 +/- 8 mV, P = 0.97), pacing impedance (875 +/- 234 ohms vs 943 +/- 331 ohms, P = 0.24), and stimulation energy threshold (2 +/- 3.2 muJ vs 1.13 +/- 1.5 muJ, P = 0.08). At a median follow-up of 33 months, a significant decrease in stimulation impedance and increase in stimulation energy threshold was observed with unipolar (689 +/- 122 vs 875 +/- 234 ohms, P < 0.01, and 8.34 +/- 10.4 muJ vs 2 +/- 3.2 muJ, P < 0.001, respectively) as well as with bipolar (735 +/- 268 ohms vs 943 +/- 331 ohms, P < 0.01, and 4.81 +/- 9.92 vs 1.13 +/- 1.5 muJ, P = 0.02, respectively) leads. No significant difference in sensing performance was observed with either type of lead (10 +/- 5 mV vs 14 +/- 6 mV and 10 +/- 6 mV vs 14 +/- 8 mV, respectively). At long-term follow-up, no significant difference among any sensing or stimulation parameter was observed between unipolar and bipolar leads.'] Does long-term performance of coronary sinus lead used for cardiac resynchronization therapy?